Merge pull request #5084 from mruby/mruby3

Mruby3

25 files changed, 2675 insertions, 1906 deletions

diff --git a/src/array.c b/src/array.c
index c33641264..c4bc554ef 100644
--- a/src/array.c
+++ b/src/array.c
@@ -508,21 +508,23 @@ mrb_ary_push(mrb_state *mrb, mrb_value ary, mrb_value elem)
 static mrb_value
 mrb_ary_push_m(mrb_state *mrb, mrb_value self)
 {
+  mrb_int argc;
   mrb_value *argv;
-  mrb_int len, len2, alen;
+  mrb_int len, len2;
   struct RArray *a;
 
-  mrb_get_args(mrb, "*!", &argv, &alen);
+  argc = mrb_get_argc(mrb);
+  argv = mrb_get_argv(mrb);
   a = mrb_ary_ptr(self);
   ary_modify(mrb, a);
   len = ARY_LEN(a);
-  len2 = len + alen;
+  len2 = len + argc;
   if (ARY_CAPA(a) < len2) {
     ary_expand_capa(mrb, a, len2);
   }
-  array_copy(ARY_PTR(a)+len, argv, alen);
+  array_copy(ARY_PTR(a)+len, argv, argc);
   ARY_SET_LEN(a, len2);
-  while (alen--) {
+  while (argc--) {
     mrb_field_write_barrier_value(mrb, (struct RBasic*)a, *argv);
     argv++;
   }
@@ -820,10 +822,10 @@ mrb_ary_subseq(mrb_state *mrb, mrb_value ary, mrb_int beg, mrb_int len)
 static mrb_int
 aget_index(mrb_state *mrb, mrb_value index)
 {
-  if (mrb_fixnum_p(index)) {
-    return mrb_fixnum(index);
+  if (mrb_integer_p(index)) {
+    return mrb_integer(index);
   }
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
   else if (mrb_float_p(index)) {
     return (mrb_int)mrb_float(index);
   }
@@ -883,8 +885,8 @@ mrb_ary_aget(mrb_state *mrb, mrb_value self)
       else {
         return mrb_nil_value();
       }
-    case MRB_TT_FIXNUM:
-      return mrb_ary_ref(mrb, self, mrb_fixnum(index));
+    case MRB_TT_INTEGER:
+      return mrb_ary_ref(mrb, self, mrb_integer(index));
     default:
       return mrb_ary_ref(mrb, self, aget_index(mrb, index));
     }
@@ -1086,11 +1088,11 @@ mrb_ary_splat(mrb_state *mrb, mrb_value v)
     return mrb_obj_value(a);
   }
 
-  if (!mrb_respond_to(mrb, v, mrb_intern_lit(mrb, "to_a"))) {
+  if (!mrb_respond_to(mrb, v, MRB_SYM(to_a))) {
     return mrb_ary_new_from_values(mrb, 1, &v);
   }
 
-  ary = mrb_funcall(mrb, v, "to_a", 0);
+  ary = mrb_funcall_id(mrb, v, MRB_SYM(to_a), 0);
   if (mrb_nil_p(ary)) {
     return mrb_ary_new_from_values(mrb, 1, &v);
   }
@@ -1121,8 +1123,14 @@ mrb_ary_clear(mrb_state *mrb, mrb_value self)
   else if (!ARY_EMBED_P(a)){
     mrb_free(mrb, a->as.heap.ptr);
   }
-  ARY_SET_EMBED_LEN(a, 0);
-
+  if (MRB_ARY_EMBED_LEN_MAX > 0) {
+    ARY_SET_EMBED_LEN(a, 0);
+  }
+  else {
+    a->as.heap.ptr = NULL;
+    a->as.heap.aux.capa = 0;
+    ARY_SET_LEN(a, 0);
+  }
   return self;
 }
 
@@ -1302,31 +1310,42 @@ static const mrb_code each_iseq[] = {
   OP_RETURN, 0x0             /* OP_RETURN    R3 */
 };
 
+static const mrb_sym each_syms[] = {
+  MRB_SYM(each),
+  MRB_SYM(to_enum),
+  MRB_QSYM(aref),
+  MRB_SYM(call),
+  MRB_SYM(length),
+};
+
+static const mrb_irep each_irep = {
+  3,                                   /* nlocals */
+  7,                                   /* nregs */
+  0,                                   /* clen */
+  MRB_ISEQ_NO_FREE | MRB_IREP_NO_FREE, /* flags */
+  each_iseq,                           /* iseq */
+  NULL,                                /* pool */
+  each_syms,                           /* syms */
+  NULL,                                /* reps */
+  NULL,                                /* lv */
+  NULL,                                /* debug_info */
+  sizeof(each_iseq),                   /* ilen */
+  0,                                   /* plen */
+  sizeof(each_syms),                   /* slen */
+  1,                                   /* rlen */
+  0,                                   /* refcnt */
+};
+
 static void
 init_ary_each(mrb_state *mrb, struct RClass *ary)
 {
   struct RProc *p;
   mrb_method_t m;
-  mrb_irep *each_irep = (mrb_irep*)mrb_malloc(mrb, sizeof(mrb_irep));
-  static const mrb_irep mrb_irep_zero = { 0 };
-
-  *each_irep = mrb_irep_zero;
-  each_irep->syms = (mrb_sym*)mrb_malloc(mrb, sizeof(mrb_sym)*5);
-  each_irep->syms[0] = mrb_intern_lit(mrb, "each");
-  each_irep->syms[1] = mrb_intern_lit(mrb, "to_enum");
-  each_irep->syms[2] = mrb_intern_lit(mrb, "[]");
-  each_irep->syms[3] = mrb_intern_lit(mrb, "call");
-  each_irep->syms[4] = mrb_intern_lit(mrb, "length");
-  each_irep->slen = 5;
-  each_irep->flags = MRB_ISEQ_NO_FREE;
-  each_irep->iseq = each_iseq;
-  each_irep->ilen = sizeof(each_iseq);
-  each_irep->nregs = 7;
-  each_irep->nlocals = 3;
-  p = mrb_proc_new(mrb, each_irep);
+
+  p = mrb_proc_new(mrb, &each_irep);
   p->flags |= MRB_PROC_SCOPE | MRB_PROC_STRICT;
   MRB_METHOD_FROM_PROC(m, p);
-  mrb_define_method_raw(mrb, ary, mrb_intern_lit(mrb, "each"), m);
+  mrb_define_method_raw(mrb, ary, MRB_SYM(each), m);
 }
 
 void
diff --git a/src/backtrace.c b/src/backtrace.c
index 591f4ea4b..bcc188796 100644
--- a/src/backtrace.c
+++ b/src/backtrace.c
@@ -39,7 +39,7 @@ each_backtrace(mrb_state *mrb, ptrdiff_t ciidx, const mrb_code *pc0, each_backtr
   for (i=ciidx; i >= 0; i--) {
     struct backtrace_location loc;
     mrb_callinfo *ci;
-    mrb_irep *irep;
+    const mrb_irep *irep;
     const mrb_code *pc;
 
     ci = &mrb->c->cibase[i];
@@ -114,7 +114,7 @@ mrb_print_backtrace(mrb_state *mrb)
     return;
   }
 
-  backtrace = mrb_obj_iv_get(mrb, mrb->exc, mrb_intern_lit(mrb, "backtrace"));
+  backtrace = mrb_obj_iv_get(mrb, mrb->exc, MRB_SYM(backtrace));
   if (mrb_nil_p(backtrace)) return;
   if (!mrb_array_p(backtrace)) backtrace = mrb_unpack_backtrace(mrb, backtrace);
   print_backtrace(mrb, mrb->exc, backtrace);
@@ -171,7 +171,7 @@ packed_backtrace(mrb_state *mrb)
 void
 mrb_keep_backtrace(mrb_state *mrb, mrb_value exc)
 {
-  mrb_sym sym = mrb_intern_lit(mrb, "backtrace");
+  mrb_sym sym = MRB_SYM(backtrace);
   mrb_value backtrace;
   int ai;
 
@@ -221,7 +221,7 @@ mrb_exc_backtrace(mrb_state *mrb, mrb_value exc)
   mrb_sym attr_name;
   mrb_value backtrace;
 
-  attr_name = mrb_intern_lit(mrb, "backtrace");
+  attr_name = MRB_SYM(backtrace);
   backtrace = mrb_iv_get(mrb, exc, attr_name);
   if (mrb_nil_p(backtrace) || mrb_array_p(backtrace)) {
     return backtrace;
diff --git a/src/class.c b/src/class.c
index fcbdadea8..bbf64e8ea 100644
--- a/src/class.c
+++ b/src/class.c
@@ -18,47 +18,266 @@
 #include <mruby/istruct.h>
 #include <mruby/opcode.h>
 
-KHASH_DEFINE(mt, mrb_sym, mrb_method_t, TRUE, kh_int_hash_func, kh_int_hash_equal)
+union mt_ptr {
+  struct RProc *proc;
+  mrb_func_t func;
+};
+
+struct mt_elem {
+  union mt_ptr ptr;
+  size_t func_p:1;
+  mrb_sym key:sizeof(mrb_sym)*8-1;
+};
+
+/* method table structure */
+typedef struct mt_tbl {
+  size_t size;
+  size_t alloc;
+  struct mt_elem *table;
+} mt_tbl;
+
+/* Creates the method table. */
+static mt_tbl*
+mt_new(mrb_state *mrb)
+{
+  mt_tbl *t;
+
+  t = (mt_tbl*)mrb_malloc(mrb, sizeof(mt_tbl));
+  t->size = 0;
+  t->alloc = 0;
+  t->table = NULL;
+
+  return t;
+}
+
+static struct mt_elem *mt_put(mrb_state *mrb, mt_tbl *t, mrb_sym sym, size_t func_p, union mt_ptr ptr);
+
+static void
+mt_rehash(mrb_state *mrb, mt_tbl *t)
+{
+  size_t old_alloc = t->alloc;
+  size_t new_alloc = old_alloc+1;
+  struct mt_elem *old_table = t->table;
+
+  khash_power2(new_alloc);
+  if (old_alloc == new_alloc) return;
+
+  t->alloc = new_alloc;
+  t->size = 0;
+  t->table = (struct mt_elem*)mrb_calloc(mrb, sizeof(struct mt_elem), new_alloc);
+
+  for (size_t i = 0; i < old_alloc; i++) {
+    struct mt_elem *slot = &old_table[i];
+
+    /* key = 0 means empty or deleted */
+    if (slot->key != 0) {
+      mt_put(mrb, t, slot->key, slot->func_p, slot->ptr);
+    }
+  }
+  mrb_free(mrb, old_table);
+}
+
+#define slot_empty_p(slot) ((slot)->key == 0 && (slot)->func_p == 0)
+
+/* Set the value for the symbol in the method table. */
+static struct mt_elem*
+mt_put(mrb_state *mrb, mt_tbl *t, mrb_sym sym, size_t func_p, union mt_ptr ptr)
+{
+  size_t hash, pos, start;
+  struct mt_elem *dslot = NULL;
+
+  if (t->alloc == 0) {
+    mt_rehash(mrb, t);
+  }
+  hash = kh_int_hash_func(mrb, sym);
+  start = pos = hash & (t->alloc-1);
+  for (;;) {
+    struct mt_elem *slot = &t->table[pos];
+
+    if (slot->key == sym) {
+      slot->func_p = func_p;
+      slot->ptr = ptr;
+      return slot;
+    }
+    else if (slot->key == 0) {  /* empty or deleted */
+      if (slot->func_p == 0) {  /* empty */
+        t->size++;
+        slot->key = sym;
+        slot->func_p = func_p;
+        slot->ptr = ptr;
+        return slot;
+      }
+      else if (!dslot) {        /* deleted */
+        dslot = slot;
+      }
+    }
+    pos = (pos+1) & (t->alloc-1);
+    if (pos == start) {         /* not found */
+      if (dslot) {
+        t->size++;
+        dslot->key = sym;
+        dslot->func_p = func_p;
+        dslot->ptr = ptr;
+        return dslot;
+      }
+      /* no room */
+      mt_rehash(mrb, t);
+      start = pos = hash & (t->alloc-1);
+    }
+  }
+}
+
+/* Get a value for a symbol from the method table. */
+static struct mt_elem*
+mt_get(mrb_state *mrb, mt_tbl *t, mrb_sym sym)
+{
+  size_t hash, pos, start;
+
+  if (t == NULL) return NULL;
+  if (t->alloc == 0) return NULL;
+  if (t->size == 0) return NULL;
+
+  hash = kh_int_hash_func(mrb, sym);
+  start = pos = hash & (t->alloc-1);
+  for (;;) {
+    struct mt_elem *slot = &t->table[pos];
+
+    if (slot->key == sym) {
+      return slot;
+    }
+    else if (slot_empty_p(slot)) {
+      return NULL;
+    }
+    pos = (pos+1) & (t->alloc-1);
+    if (pos == start) {         /* not found */
+      return NULL;
+    }
+  }
+}
+
+/* Deletes the value for the symbol from the method table. */
+static mrb_bool
+mt_del(mrb_state *mrb, mt_tbl *t, mrb_sym sym)
+{
+  size_t hash, pos, start;
+
+  if (t == NULL) return FALSE;
+  if (t->alloc == 0) return  FALSE;
+  if (t->size == 0) return FALSE;
+
+  hash = kh_int_hash_func(mrb, sym);
+  start = pos = hash & (t->alloc-1);
+  for (;;) {
+    struct mt_elem *slot = &t->table[pos];
+
+    if (slot->key == sym) {
+      t->size--;
+      slot->key = 0;
+      slot->func_p = 1;
+      return TRUE;
+    }
+    else if (slot_empty_p(slot)) {
+      return FALSE;
+    }
+    pos = (pos+1) & (t->alloc-1);
+    if (pos == start) {         /* not found */
+      return FALSE;
+    }
+  }
+}
+
+/* Copy the method table. */
+static struct mt_tbl*
+mt_copy(mrb_state *mrb, mt_tbl *t)
+{
+  mt_tbl *t2;
+  size_t i;
+
+  if (t == NULL) return NULL;
+  if (t->alloc == 0) return NULL;
+  if (t->size == 0) return NULL;
+
+  t2 = mt_new(mrb);
+  for (i=0; i<t->alloc; i++) {
+    struct mt_elem *slot = &t->table[i];
+
+    if (slot->key) {
+      mt_put(mrb, t2, slot->key, slot->func_p, slot->ptr);
+    }
+  }
+  return t2;
+}
+
+/* Free memory of the method table. */
+static void
+mt_free(mrb_state *mrb, mt_tbl *t)
+{
+  mrb_free(mrb, t->table);
+  mrb_free(mrb, t);
+}
+
+MRB_API void
+mrb_mt_foreach(mrb_state *mrb, struct RClass *c, mrb_mt_foreach_func *fn, void *p)
+{
+  mt_tbl *t = c->mt;
+  size_t i;
+
+  if (t == NULL) return;
+  if (t->alloc == 0) return;
+  if (t->size == 0) return;
+
+  for (i=0; i<t->alloc; i++) {
+    struct mt_elem *slot = &t->table[i];
+
+    if (slot->key) {
+      if (fn(mrb, slot->key, slot, p) != 0)
+        return;
+    }
+  }
+  return;
+}
 
 void
 mrb_gc_mark_mt(mrb_state *mrb, struct RClass *c)
 {
-  khiter_t k;
-  khash_t(mt) *h = c->mt;
+  mt_tbl *t = c->mt;
+  size_t i;
 
-  if (!h) return;
-  for (k = kh_begin(h); k != kh_end(h); k++) {
-    if (kh_exist(h, k)) {
-      mrb_method_t m = kh_value(h, k);
+  if (t == NULL) return;
+  if (t->alloc == 0) return;
+  if (t->size == 0) return;
 
-      if (MRB_METHOD_PROC_P(m)) {
-        struct RProc *p = MRB_METHOD_PROC(m);
-        mrb_gc_mark(mrb, (struct RBasic*)p);
-      }
+  for (i=0; i<t->alloc; i++) {
+    struct mt_elem *slot = &t->table[i];
+
+    if (slot->key && !slot->func_p) { /* Proc pointer */
+      struct RProc *p = slot->ptr.proc;
+      mrb_gc_mark(mrb, (struct RBasic*)p);
     }
   }
+  return;
 }
 
 size_t
 mrb_gc_mark_mt_size(mrb_state *mrb, struct RClass *c)
 {
-  khash_t(mt) *h = c->mt;
+  struct mt_tbl *h = c->mt;
 
   if (!h) return 0;
-  return kh_size(h);
+  return h->size;
 }
 
 void
 mrb_gc_free_mt(mrb_state *mrb, struct RClass *c)
 {
-  kh_destroy(mt, mrb, c->mt);
+  if (c->mt) mt_free(mrb, c->mt);
 }
 
 void
 mrb_class_name_class(mrb_state *mrb, struct RClass *outer, struct RClass *c, mrb_sym id)
 {
   mrb_value name;
-  mrb_sym nsym = mrb_intern_lit(mrb, "__classname__");
+  mrb_sym nsym = MRB_SYM(__classname__);
 
   if (mrb_obj_iv_defined(mrb, (struct RObject*)c, nsym)) return;
   if (outer == NULL || outer == mrb->object_class) {
@@ -68,7 +287,7 @@ mrb_class_name_class(mrb_state *mrb, struct RClass *outer, struct RClass *c, mrb
     name = mrb_class_path(mrb, outer);
     if (mrb_nil_p(name)) {      /* unnamed outer class */
       if (outer != mrb->object_class && outer != c) {
-        mrb_obj_iv_set_force(mrb, (struct RObject*)c, mrb_intern_lit(mrb, "__outer__"),
+        mrb_obj_iv_set_force(mrb, (struct RObject*)c, MRB_SYM(__outer__),
                              mrb_obj_value(outer));
       }
       return;
@@ -107,7 +326,7 @@ prepare_singleton_class(mrb_state *mrb, struct RBasic *o)
   if (o->c->tt == MRB_TT_SCLASS) return;
   sc = (struct RClass*)mrb_obj_alloc(mrb, MRB_TT_SCLASS, mrb->class_class);
   sc->flags |= MRB_FL_CLASS_IS_INHERITED;
-  sc->mt = kh_init(mt, mrb);
+  sc->mt = mt_new(mrb);
   sc->iv = 0;
   if (o->tt == MRB_TT_CLASS) {
     c = (struct RClass*)o;
@@ -132,7 +351,7 @@ prepare_singleton_class(mrb_state *mrb, struct RBasic *o)
   o->c = sc;
   mrb_field_write_barrier(mrb, (struct RBasic*)o, (struct RBasic*)sc);
   mrb_field_write_barrier(mrb, (struct RBasic*)sc, (struct RBasic*)o);
-  mrb_obj_iv_set(mrb, (struct RObject*)sc, mrb_intern_lit(mrb, "__attached__"), mrb_obj_value(o));
+  mrb_obj_iv_set(mrb, (struct RObject*)sc, MRB_SYM(__attached__), mrb_obj_value(o));
   sc->flags |= o->flags & MRB_FL_OBJ_IS_FROZEN;
 }
 
@@ -230,6 +449,15 @@ mrb_vm_define_module(mrb_state *mrb, mrb_value outer, mrb_sym id)
 }
 
 MRB_API struct RClass*
+mrb_define_module_under_id(mrb_state *mrb, struct RClass *outer, mrb_sym name)
+{
+  struct RClass * c = define_module(mrb, name, outer);
+
+  setup_class(mrb, outer, c, name);
+  return c;
+}
+
+MRB_API struct RClass*
 mrb_define_module_under(mrb_state *mrb, struct RClass *outer, const char *name)
 {
   mrb_sym id = mrb_intern_cstr(mrb, name);
@@ -283,12 +511,10 @@ mrb_define_class(mrb_state *mrb, const char *name, struct RClass *super)
 }
 
 static mrb_value mrb_bob_init(mrb_state *mrb, mrb_value);
-#ifdef MRB_METHOD_CACHE
-static void mc_clear_all(mrb_state *mrb);
-static void mc_clear_by_id(mrb_state *mrb, struct RClass*, mrb_sym);
+#ifndef MRB_NO_METHOD_CACHE
+static void mc_clear(mrb_state *mrb);
 #else
-#define mc_clear_all(mrb)
-#define mc_clear_by_id(mrb,c,s)
+#define mc_clear(mrb)
 #endif
 
 static void
@@ -302,7 +528,7 @@ mrb_class_inherited(mrb_state *mrb, struct RClass *super, struct RClass *klass)
   super->flags |= MRB_FL_CLASS_IS_INHERITED;
   s = mrb_obj_value(super);
   mrb_mc_clear_by_class(mrb, klass);
-  mid = mrb_intern_lit(mrb, "inherited");
+  mid = MRB_SYM(inherited);
   if (!mrb_func_basic_p(mrb, s, mid, mrb_bob_init)) {
     mrb_value c = mrb_obj_value(klass);
     mrb_funcall_argv(mrb, s, mid, 1, &c);
@@ -349,21 +575,29 @@ mrb_vm_define_class(mrb_state *mrb, mrb_value outer, mrb_value super, mrb_sym id
 MRB_API mrb_bool
 mrb_class_defined(mrb_state *mrb, const char *name)
 {
-  mrb_value sym = mrb_check_intern_cstr(mrb, name);
-  if (mrb_nil_p(sym)) {
-    return FALSE;
-  }
-  return mrb_const_defined(mrb, mrb_obj_value(mrb->object_class), mrb_symbol(sym));
+  mrb_sym sym = mrb_intern_check_cstr(mrb, name);
+  if (!sym) return FALSE;
+  return mrb_const_defined(mrb, mrb_obj_value(mrb->object_class), sym);
+}
+
+MRB_API mrb_bool
+mrb_class_defined_id(mrb_state *mrb, mrb_sym name)
+{
+  return mrb_const_defined(mrb, mrb_obj_value(mrb->object_class), name);
 }
 
 MRB_API mrb_bool
 mrb_class_defined_under(mrb_state *mrb, struct RClass *outer, const char *name)
 {
-  mrb_value sym = mrb_check_intern_cstr(mrb, name);
-  if (mrb_nil_p(sym)) {
-    return FALSE;
-  }
-  return mrb_const_defined_at(mrb, mrb_obj_value(outer), mrb_symbol(sym));
+  mrb_sym sym = mrb_intern_check_cstr(mrb, name);
+  if (!sym) return FALSE;
+  return mrb_const_defined_at(mrb, mrb_obj_value(outer), sym);
+}
+
+MRB_API mrb_bool
+mrb_class_defined_under_id(mrb_state *mrb, struct RClass *outer, mrb_sym name)
+{
+  return mrb_const_defined_at(mrb, mrb_obj_value(outer), name);
 }
 
 MRB_API struct RClass*
@@ -373,17 +607,28 @@ mrb_class_get_under(mrb_state *mrb, struct RClass *outer, const char *name)
 }
 
 MRB_API struct RClass*
+mrb_class_get_under_id(mrb_state *mrb, struct RClass *outer, mrb_sym name)
+{
+  return class_from_sym(mrb, outer, name);
+}
+
+MRB_API struct RClass*
 mrb_class_get(mrb_state *mrb, const char *name)
 {
   return mrb_class_get_under(mrb, mrb->object_class, name);
 }
 
 MRB_API struct RClass*
-mrb_exc_get(mrb_state *mrb, const char *name)
+mrb_class_get_id(mrb_state *mrb, mrb_sym name)
+{
+  return mrb_class_get_under_id(mrb, mrb->object_class, name);
+}
+
+MRB_API struct RClass*
+mrb_exc_get_id(mrb_state *mrb, mrb_sym name)
 {
   struct RClass *exc, *e;
-  mrb_value c = mrb_const_get(mrb, mrb_obj_value(mrb->object_class),
-                              mrb_intern_cstr(mrb, name));
+  mrb_value c = mrb_const_get(mrb, mrb_obj_value(mrb->object_class), name);
 
   if (!mrb_class_p(c)) {
     mrb_raise(mrb, mrb->eException_class, "exception corrupted");
@@ -405,11 +650,23 @@ mrb_module_get_under(mrb_state *mrb, struct RClass *outer, const char *name)
 }
 
 MRB_API struct RClass*
+mrb_module_get_under_id(mrb_state *mrb, struct RClass *outer, mrb_sym name)
+{
+  return module_from_sym(mrb, outer, name);
+}
+
+MRB_API struct RClass*
 mrb_module_get(mrb_state *mrb, const char *name)
 {
   return mrb_module_get_under(mrb, mrb->object_class, name);
 }
 
+MRB_API struct RClass*
+mrb_module_get_id(mrb_state *mrb, mrb_sym name)
+{
+  return mrb_module_get_under_id(mrb, mrb->object_class, name);
+}
+
 /*!
  * Defines a class under the namespace of \a outer.
  * \param outer  a class which contains the new class.
@@ -427,9 +684,8 @@ mrb_module_get(mrb_state *mrb, const char *name)
  *       \a super, the function just returns the defined class.
  */
 MRB_API struct RClass*
-mrb_define_class_under(mrb_state *mrb, struct RClass *outer, const char *name, struct RClass *super)
+mrb_define_class_under_id(mrb_state *mrb, struct RClass *outer, mrb_sym name, struct RClass *super)
 {
-  mrb_sym id = mrb_intern_cstr(mrb, name);
   struct RClass * c;
 
 #if 0
@@ -437,34 +693,45 @@ mrb_define_class_under(mrb_state *mrb, struct RClass *outer, const char *name, s
     mrb_warn(mrb, "no super class for '%C::%n', Object assumed", outer, id);
   }
 #endif
-  c = define_class(mrb, id, super, outer);
-  setup_class(mrb, outer, c, id);
+  c = define_class(mrb, name, super, outer);
+  setup_class(mrb, outer, c, name);
   return c;
 }
 
+MRB_API struct RClass*
+mrb_define_class_under(mrb_state *mrb, struct RClass *outer, const char *name, struct RClass *super)
+{
+  return mrb_define_class_under_id(mrb, outer, mrb_intern_cstr(mrb, name), super);
+}
+
 MRB_API void
 mrb_define_method_raw(mrb_state *mrb, struct RClass *c, mrb_sym mid, mrb_method_t m)
 {
-  khash_t(mt) *h;
-  khiter_t k;
+  mt_tbl *h;
+  union mt_ptr ptr;
+
   MRB_CLASS_ORIGIN(c);
   h = c->mt;
-
   mrb_check_frozen(mrb, c);
-  if (!h) h = c->mt = kh_init(mt, mrb);
-  k = kh_put(mt, mrb, h, mid);
-  kh_value(h, k) = m;
-  if (MRB_METHOD_PROC_P(m) && !MRB_METHOD_UNDEF_P(m)) {
+  if (!h) h = c->mt = mt_new(mrb);
+  if (MRB_METHOD_PROC_P(m)) {
     struct RProc *p = MRB_METHOD_PROC(m);
 
-    p->flags |= MRB_PROC_SCOPE;
-    p->c = NULL;
-    mrb_field_write_barrier(mrb, (struct RBasic*)c, (struct RBasic*)p);
-    if (!MRB_PROC_ENV_P(p)) {
-      MRB_PROC_SET_TARGET_CLASS(p, c);
+    ptr.proc = p;
+    if (p) {
+      p->flags |= MRB_PROC_SCOPE;
+      p->c = NULL;
+      mrb_field_write_barrier(mrb, (struct RBasic*)c, (struct RBasic*)p);
+      if (!MRB_PROC_ENV_P(p)) {
+        MRB_PROC_SET_TARGET_CLASS(p, c);
+      }
     }
   }
-  mc_clear_by_id(mrb, c, mid);
+  else {
+    ptr.func = MRB_METHOD_FUNC(m);
+  }
+  mt_put(mrb, h, mid, MRB_METHOD_FUNC_P(m), ptr);
+  mc_clear(mrb);
 }
 
 MRB_API void
@@ -474,6 +741,9 @@ mrb_define_method_id(mrb_state *mrb, struct RClass *c, mrb_sym mid, mrb_func_t f
   int ai = mrb_gc_arena_save(mrb);
 
   MRB_METHOD_FROM_FUNC(m, func);
+#ifndef MRB_USE_METHOD_T_STRUCT
+  mrb_assert(MRB_METHOD_FUNC(m) == func);
+#endif
   if (aspec == MRB_ARGS_NONE()) {
     MRB_METHOD_NOARG_SET(m);
   }
@@ -588,8 +858,8 @@ void mrb_hash_check_kdict(mrb_state *mrb, mrb_value self);
     z:      String         [const char*]          NUL terminated string; z! gives NULL for nil
     a:      Array          [mrb_value*,mrb_int]   Receive two arguments; a! gives (NULL,0) for nil
     c:      Class/Module   [strcut RClass*]
-    f:      Fixnum/Float   [mrb_float]
-    i:      Fixnum/Float   [mrb_int]
+    f:      Integer/Float  [mrb_float]
+    i:      Integer/Float  [mrb_int]
     b:      boolean        [mrb_bool]
     n:      String/Symbol  [mrb_sym]
     d:      data           [void*,mrb_data_type const] 2nd argument will be used to check data type so it won't be modified; when ! follows, the value may be nil
@@ -849,7 +1119,7 @@ mrb_get_args(mrb_state *mrb, const char *format, ...)
         }
       }
       break;
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
     case 'f':
       {
         mrb_float *p;
@@ -867,7 +1137,7 @@ mrb_get_args(mrb_state *mrb, const char *format, ...)
 
         p = va_arg(ap, mrb_int*);
         if (i < argc) {
-          *p = mrb_fixnum(mrb_to_int(mrb, argv[i++]));
+          *p = mrb_integer(mrb_to_int(mrb, argv[i++]));
         }
       }
       break;
@@ -984,7 +1254,7 @@ mrb_get_args(mrb_state *mrb, const char *format, ...)
         else {
           uint32_t kwnum = kwargs->num;
           uint32_t required = kwargs->required;
-          const char *const *kname = kwargs->table;
+          const mrb_sym *kname = kwargs->table;
           mrb_value *values = kwargs->values;
           uint32_t j;
           const uint32_t keyword_max = 40;
@@ -994,16 +1264,16 @@ mrb_get_args(mrb_state *mrb, const char *format, ...)
           }
 
           for (j = required; j > 0; j --, kname ++, values ++) {
-            mrb_value k = mrb_symbol_value(mrb_intern_cstr(mrb, *kname));
+            mrb_value k = mrb_symbol_value(*kname);
             if (!mrb_hash_key_p(mrb, ksrc, k)) {
-              mrb_raisef(mrb, E_ARGUMENT_ERROR, "missing keyword: %s", *kname);
+              mrb_raisef(mrb, E_ARGUMENT_ERROR, "missing keyword: %n", *kname);
             }
             *values = mrb_hash_delete_key(mrb, ksrc, k);
             mrb_gc_protect(mrb, *values);
           }
 
           for (j = kwnum - required; j > 0; j --, kname ++, values ++) {
-            mrb_value k = mrb_symbol_value(mrb_intern_cstr(mrb, *kname));
+            mrb_value k = mrb_symbol_value(*kname);
             if (mrb_hash_key_p(mrb, ksrc, k)) {
               *values = mrb_hash_delete_key(mrb, ksrc, k);
               mrb_gc_protect(mrb, *values);
@@ -1057,7 +1327,7 @@ boot_defclass(mrb_state *mrb, struct RClass *super)
   else {
     c->super = mrb->object_class;
   }
-  c->mt = kh_init(mt, mrb);
+  c->mt = mt_new(mrb);
   return c;
 }
 
@@ -1065,7 +1335,7 @@ static void
 boot_initmod(mrb_state *mrb, struct RClass *mod)
 {
   if (!mod->mt) {
-    mod->mt = kh_init(mt, mrb);
+    mod->mt = mt_new(mrb);
   }
 }
 
@@ -1129,7 +1399,7 @@ include_module_at(mrb_state *mrb, struct RClass *c, struct RClass *ins_pos, stru
   skip:
     m = m->super;
   }
-  mc_clear_all(mrb);
+  mc_clear(mrb);
   return 0;
 }
 
@@ -1155,7 +1425,7 @@ mrb_prepend_module(mrb_state *mrb, struct RClass *c, struct RClass *m)
     origin->super = c->super;
     c->super = origin;
     origin->mt = c->mt;
-    c->mt = kh_init(mt, mrb);
+    c->mt = mt_new(mrb);
     mrb_field_write_barrier(mrb, (struct RBasic*)c, (struct RBasic*)origin);
     c->flags |= MRB_FL_CLASS_IS_PREPENDED;
   }
@@ -1292,8 +1562,8 @@ mrb_singleton_class_ptr(mrb_state *mrb, mrb_value v)
   case MRB_TT_CPTR:
     return mrb->object_class;
   case MRB_TT_SYMBOL:
-  case MRB_TT_FIXNUM:
-#ifndef MRB_WITHOUT_FLOAT
+  case MRB_TT_INTEGER:
+#ifndef MRB_NO_FLOAT
   case MRB_TT_FLOAT:
 #endif
     return NULL;
@@ -1324,28 +1594,42 @@ mrb_define_singleton_method(mrb_state *mrb, struct RObject *o, const char *name,
 }
 
 MRB_API void
+mrb_define_singleton_method_id(mrb_state *mrb, struct RObject *o, mrb_sym name, mrb_func_t func, mrb_aspec aspec)
+{
+  prepare_singleton_class(mrb, (struct RBasic*)o);
+  mrb_define_method_id(mrb, o->c, name, func, aspec);
+}
+
+MRB_API void
 mrb_define_class_method(mrb_state *mrb, struct RClass *c, const char *name, mrb_func_t func, mrb_aspec aspec)
 {
   mrb_define_singleton_method(mrb, (struct RObject*)c, name, func, aspec);
 }
 
 MRB_API void
+mrb_define_class_method_id(mrb_state *mrb, struct RClass *c, mrb_sym name, mrb_func_t func, mrb_aspec aspec)
+{
+  mrb_define_singleton_method_id(mrb, (struct RObject*)c, name, func, aspec);
+}
+
+MRB_API void
+mrb_define_module_function_id(mrb_state *mrb, struct RClass *c, mrb_sym name, mrb_func_t func, mrb_aspec aspec)
+{
+  mrb_define_class_method_id(mrb, c, name, func, aspec);
+  mrb_define_method_id(mrb, c, name, func, aspec);
+}
+
+MRB_API void
 mrb_define_module_function(mrb_state *mrb, struct RClass *c, const char *name, mrb_func_t func, mrb_aspec aspec)
 {
-  mrb_define_class_method(mrb, c, name, func, aspec);
-  mrb_define_method(mrb, c, name, func, aspec);
+  mrb_define_module_function_id(mrb, c, mrb_intern_cstr(mrb, name), func, aspec);
 }
 
-#ifdef MRB_METHOD_CACHE
+#ifndef MRB_NO_METHOD_CACHE
 static void
-mc_clear_all(mrb_state *mrb)
+mc_clear(mrb_state *mrb)
 {
-  struct mrb_cache_entry *mc = mrb->cache;
-  int i;
-
-  for (i=0; i<MRB_METHOD_CACHE_SIZE; i++) {
-    mc[i].c = 0;
-  }
+  memset(mrb->cache, 0, MRB_METHOD_CACHE_SIZE*sizeof(mrb->cache[0]));
 }
 
 void
@@ -1355,7 +1639,7 @@ mrb_mc_clear_by_class(mrb_state *mrb, struct RClass *c)
   int i;
 
   if (c->flags & MRB_FL_CLASS_IS_INHERITED) {
-    mc_clear_all(mrb);
+    mc_clear(mrb);
     c->flags &= ~MRB_FL_CLASS_IS_INHERITED;
     return;
   }
@@ -1363,32 +1647,14 @@ mrb_mc_clear_by_class(mrb_state *mrb, struct RClass *c)
     if (mc[i].c == c) mc[i].c = 0;
   }
 }
-
-static void
-mc_clear_by_id(mrb_state *mrb, struct RClass *c, mrb_sym mid)
-{
-  struct mrb_cache_entry *mc = mrb->cache;
-  int i;
-
-  if (c->flags & MRB_FL_CLASS_IS_INHERITED) {
-    mc_clear_all(mrb);
-    c->flags &= ~MRB_FL_CLASS_IS_INHERITED;
-    return;
-  }
-  for (i=0; i<MRB_METHOD_CACHE_SIZE; i++) {
-    if (mc[i].c == c || mc[i].mid == mid)
-      mc[i].c = 0;
-  }
-}
 #endif
 
 MRB_API mrb_method_t
 mrb_method_search_vm(mrb_state *mrb, struct RClass **cp, mrb_sym mid)
 {
-  khiter_t k;
   mrb_method_t m;
   struct RClass *c = *cp;
-#ifdef MRB_METHOD_CACHE
+#ifndef MRB_NO_METHOD_CACHE
   struct RClass *oc = c;
   int h = kh_int_hash_func(mrb, ((intptr_t)oc) ^ mid) & (MRB_METHOD_CACHE_SIZE-1);
   struct mrb_cache_entry *mc = &mrb->cache[h];
@@ -1400,15 +1666,20 @@ mrb_method_search_vm(mrb_state *mrb, struct RClass **cp, mrb_sym mid)
 #endif
 
   while (c) {
-    khash_t(mt) *h = c->mt;
+    mt_tbl *h = c->mt;
 
     if (h) {
-      k = kh_get(mt, mrb, h, mid);
-      if (k != kh_end(h)) {
-        m = kh_value(h, k);
-        if (MRB_METHOD_UNDEF_P(m)) break;
+      struct mt_elem *e = mt_get(mrb, h, mid);
+      if (e) {
+        if (e->ptr.proc == 0) break;
         *cp = c;
-#ifdef MRB_METHOD_CACHE
+        if (e->func_p) {
+          MRB_METHOD_FROM_FUNC(m, e->ptr.func);
+        }
+        else {
+          MRB_METHOD_FROM_PROC(m, e->ptr.proc);
+        }
+#ifndef MRB_NO_METHOD_CACHE
         mc->c = oc;
         mc->c0 = c;
         mc->mid = mid;
@@ -1578,7 +1849,7 @@ mrb_instance_new(mrb_state *mrb, mrb_value cv)
 
   mrb_get_args(mrb, "*!&", &argv, &argc, &blk);
   obj = mrb_instance_alloc(mrb, cv);
-  init = mrb_intern_lit(mrb, "initialize");
+  init = MRB_SYM(initialize);
   if (!mrb_func_basic_p(mrb, obj, init, mrb_bob_init)) {
     mrb_funcall_with_block(mrb, obj, init, argc, argv, blk);
   }
@@ -1592,7 +1863,7 @@ mrb_obj_new(mrb_state *mrb, struct RClass *c, mrb_int argc, const mrb_value *arg
   mrb_sym mid;
 
   obj = mrb_instance_alloc(mrb, mrb_obj_value(c));
-  mid = mrb_intern_lit(mrb, "initialize");
+  mid = MRB_SYM(initialize);
   if (!mrb_func_basic_p(mrb, obj, mid, mrb_bob_init)) {
     mrb_funcall_argv(mrb, obj, mid, argc, argv);
   }
@@ -1624,7 +1895,7 @@ mrb_class_new_class(mrb_state *mrb, mrb_value cv)
     super = mrb_obj_value(mrb->object_class);
   }
   new_class = mrb_obj_value(mrb_class_new(mrb, mrb_class_ptr(super)));
-  mid = mrb_intern_lit(mrb, "initialize");
+  mid = MRB_SYM(initialize);
   if (mrb_func_basic_p(mrb, new_class, mid, mrb_class_initialize)) {
     mrb_class_initialize(mrb, new_class);
   }
@@ -1722,7 +1993,7 @@ MRB_API mrb_value
 mrb_class_path(mrb_state *mrb, struct RClass *c)
 {
   mrb_value path;
-  mrb_sym nsym = mrb_intern_lit(mrb, "__classname__");
+  mrb_sym nsym = MRB_SYM(__classname__);
 
   path = mrb_obj_iv_get(mrb, (struct RObject*)c, nsym);
   if (mrb_nil_p(path)) {
@@ -1827,7 +2098,7 @@ mrb_module_new(mrb_state *mrb)
  *  called with an explicit receiver, as <code>class</code> is also a
  *  reserved word in Ruby.
  *
- *     1.class      #=> Fixnum
+ *     1.class      #=> Integer
  *     self.class   #=> Object
  */
 
@@ -1877,6 +2148,12 @@ mrb_define_alias(mrb_state *mrb, struct RClass *klass, const char *name1, const
   mrb_alias_method(mrb, klass, mrb_intern_cstr(mrb, name1), mrb_intern_cstr(mrb, name2));
 }
 
+MRB_API void
+mrb_define_alias_id(mrb_state *mrb, struct RClass *klass, mrb_sym a, mrb_sym b)
+{
+  mrb_alias_method(mrb, klass, a, b);
+}
+
 /*
  * call-seq:
  *   mod.to_s   -> string
@@ -1891,7 +2168,7 @@ mrb_mod_to_s(mrb_state *mrb, mrb_value klass)
 {
 
   if (mrb_sclass_p(klass)) {
-    mrb_value v = mrb_iv_get(mrb, klass, mrb_intern_lit(mrb, "__attached__"));
+    mrb_value v = mrb_iv_get(mrb, klass, MRB_SYM(__attached__));
     mrb_value str = mrb_str_new_lit(mrb, "#<Class:");
 
     if (class_ptr_p(v)) {
@@ -1927,7 +2204,7 @@ undef_method(mrb_state *mrb, struct RClass *c, mrb_sym a)
   mrb_define_method_raw(mrb, c, a, m);
 }
 
-void
+MRB_API void
 mrb_undef_method_id(mrb_state *mrb, struct RClass *c, mrb_sym a)
 {
   if (!mrb_obj_respond_to(mrb, c, a)) {
@@ -1943,11 +2220,29 @@ mrb_undef_method(mrb_state *mrb, struct RClass *c, const char *name)
 }
 
 MRB_API void
+mrb_undef_class_method_id(mrb_state *mrb, struct RClass *c, mrb_sym name)
+{
+  mrb_undef_method_id(mrb,  mrb_class_ptr(mrb_singleton_class(mrb, mrb_obj_value(c))), name);
+}
+
+MRB_API void
 mrb_undef_class_method(mrb_state *mrb, struct RClass *c, const char *name)
 {
   mrb_undef_method(mrb,  mrb_class_ptr(mrb_singleton_class(mrb, mrb_obj_value(c))), name);
 }
 
+MRB_API void
+mrb_remove_method(mrb_state *mrb, struct RClass *c, mrb_sym mid)
+{
+  mt_tbl *h;
+
+  MRB_CLASS_ORIGIN(c);
+  h = c->mt;
+
+  if (h && mt_del(mrb, h, mid)) return;
+  mrb_name_error(mrb, mid, "method '%n' not defined in %C", mid, c);
+}
+
 static mrb_value
 mrb_mod_undef(mrb_state *mrb, mrb_value mod)
 {
@@ -2207,6 +2502,202 @@ mrb_mod_module_function(mrb_state *mrb, mrb_value mod)
   return mod;
 }
 
+static struct RClass*
+mrb_singleton_class_clone(mrb_state *mrb, mrb_value obj)
+{
+  struct RClass *klass = mrb_basic_ptr(obj)->c;
+
+  if (klass->tt != MRB_TT_SCLASS)
+    return klass;
+  else {
+    /* copy singleton(unnamed) class */
+    struct RClass *clone = (struct RClass*)mrb_obj_alloc(mrb, klass->tt, mrb->class_class);
+
+    switch (mrb_type(obj)) {
+    case MRB_TT_CLASS:
+    case MRB_TT_SCLASS:
+      break;
+    default:
+      clone->c = mrb_singleton_class_clone(mrb, mrb_obj_value(klass));
+      break;
+    }
+    clone->super = klass->super;
+    if (klass->iv) {
+      mrb_iv_copy(mrb, mrb_obj_value(clone), mrb_obj_value(klass));
+      mrb_obj_iv_set(mrb, (struct RObject*)clone, MRB_SYM(__attached__), obj);
+    }
+    if (klass->mt) {
+      clone->mt = mt_copy(mrb, klass->mt);
+    }
+    else {
+      clone->mt = mt_new(mrb);
+    }
+    clone->tt = MRB_TT_SCLASS;
+    return clone;
+  }
+}
+
+static void
+copy_class(mrb_state *mrb, mrb_value dst, mrb_value src)
+{
+  struct RClass *dc = mrb_class_ptr(dst);
+  struct RClass *sc = mrb_class_ptr(src);
+  /* if the origin is not the same as the class, then the origin and
+     the current class need to be copied */
+  if (sc->flags & MRB_FL_CLASS_IS_PREPENDED) {
+    struct RClass *c0 = sc->super;
+    struct RClass *c1 = dc;
+
+    /* copy prepended iclasses */
+    while (!(c0->flags & MRB_FL_CLASS_IS_ORIGIN)) {
+      c1->super = mrb_class_ptr(mrb_obj_dup(mrb, mrb_obj_value(c0)));
+      c1 = c1->super;
+      c0 = c0->super;
+    }
+    c1->super = mrb_class_ptr(mrb_obj_dup(mrb, mrb_obj_value(c0)));
+    c1->super->flags |= MRB_FL_CLASS_IS_ORIGIN;
+  }
+  if (sc->mt) {
+    dc->mt = mt_copy(mrb, sc->mt);
+  }
+  else {
+    dc->mt = mt_new(mrb);
+  }
+  dc->super = sc->super;
+  MRB_SET_INSTANCE_TT(dc, MRB_INSTANCE_TT(sc));
+}
+
+/* 15.3.1.3.16 */
+static mrb_value
+mrb_obj_init_copy(mrb_state *mrb, mrb_value self)
+{
+  mrb_value orig = mrb_get_arg1(mrb);
+
+  if (mrb_obj_equal(mrb, self, orig)) return self;
+  if ((mrb_type(self) != mrb_type(orig)) || (mrb_obj_class(mrb, self) != mrb_obj_class(mrb, orig))) {
+      mrb_raise(mrb, E_TYPE_ERROR, "initialize_copy should take same class object");
+  }
+  return self;
+}
+
+static void
+init_copy(mrb_state *mrb, mrb_value dest, mrb_value obj)
+{
+  switch (mrb_type(obj)) {
+    case MRB_TT_ICLASS:
+      copy_class(mrb, dest, obj);
+      return;
+    case MRB_TT_CLASS:
+    case MRB_TT_MODULE:
+      copy_class(mrb, dest, obj);
+      mrb_iv_copy(mrb, dest, obj);
+      mrb_iv_remove(mrb, dest, MRB_SYM(__classname__));
+      break;
+    case MRB_TT_OBJECT:
+    case MRB_TT_SCLASS:
+    case MRB_TT_HASH:
+    case MRB_TT_DATA:
+    case MRB_TT_EXCEPTION:
+      mrb_iv_copy(mrb, dest, obj);
+      break;
+    case MRB_TT_ISTRUCT:
+      mrb_istruct_copy(dest, obj);
+      break;
+
+    default:
+      break;
+  }
+  if (!mrb_func_basic_p(mrb, dest, MRB_SYM(initialize_copy), mrb_obj_init_copy)) {
+    mrb_funcall_id(mrb, dest, MRB_SYM(initialize_copy), 1, obj);
+  }
+}
+
+/* 15.3.1.3.8  */
+/*
+ *  call-seq:
+ *     obj.clone -> an_object
+ *
+ *  Produces a shallow copy of <i>obj</i>---the instance variables of
+ *  <i>obj</i> are copied, but not the objects they reference. Copies
+ *  the frozen state of <i>obj</i>. See also the discussion
+ *  under <code>Object#dup</code>.
+ *
+ *     class Klass
+ *        attr_accessor :str
+ *     end
+ *     s1 = Klass.new      #=> #<Klass:0x401b3a38>
+ *     s1.str = "Hello"    #=> "Hello"
+ *     s2 = s1.clone       #=> #<Klass:0x401b3998 @str="Hello">
+ *     s2.str[1,4] = "i"   #=> "i"
+ *     s1.inspect          #=> "#<Klass:0x401b3a38 @str=\"Hi\">"
+ *     s2.inspect          #=> "#<Klass:0x401b3998 @str=\"Hi\">"
+ *
+ *  This method may have class-specific behavior.  If so, that
+ *  behavior will be documented under the #+initialize_copy+ method of
+ *  the class.
+ *
+ *  Some Class(True False Nil Symbol Integer Float) Object  cannot clone.
+ */
+MRB_API mrb_value
+mrb_obj_clone(mrb_state *mrb, mrb_value self)
+{
+  struct RObject *p;
+  mrb_value clone;
+
+  if (mrb_immediate_p(self)) {
+    return self;
+  }
+  if (mrb_sclass_p(self)) {
+    mrb_raise(mrb, E_TYPE_ERROR, "can't clone singleton class");
+  }
+  p = (struct RObject*)mrb_obj_alloc(mrb, mrb_type(self), mrb_obj_class(mrb, self));
+  p->c = mrb_singleton_class_clone(mrb, self);
+  mrb_field_write_barrier(mrb, (struct RBasic*)p, (struct RBasic*)p->c);
+  clone = mrb_obj_value(p);
+  init_copy(mrb, clone, self);
+  p->flags |= mrb_obj_ptr(self)->flags & MRB_FL_OBJ_IS_FROZEN;
+
+  return clone;
+}
+
+/* 15.3.1.3.9  */
+/*
+ *  call-seq:
+ *     obj.dup -> an_object
+ *
+ *  Produces a shallow copy of <i>obj</i>---the instance variables of
+ *  <i>obj</i> are copied, but not the objects they reference.
+ *  <code>dup</code> copies the frozen state of <i>obj</i>. See also
+ *  the discussion under <code>Object#clone</code>. In general,
+ *  <code>clone</code> and <code>dup</code> may have different semantics
+ *  in descendant classes. While <code>clone</code> is used to duplicate
+ *  an object, including its internal state, <code>dup</code> typically
+ *  uses the class of the descendant object to create the new instance.
+ *
+ *  This method may have class-specific behavior.  If so, that
+ *  behavior will be documented under the #+initialize_copy+ method of
+ *  the class.
+ */
+
+MRB_API mrb_value
+mrb_obj_dup(mrb_state *mrb, mrb_value obj)
+{
+  struct RBasic *p;
+  mrb_value dup;
+
+  if (mrb_immediate_p(obj)) {
+    return obj;
+  }
+  if (mrb_sclass_p(obj)) {
+    mrb_raise(mrb, E_TYPE_ERROR, "can't dup singleton class");
+  }
+  p = mrb_obj_alloc(mrb, mrb_type(obj), mrb_obj_class(mrb, obj));
+  dup = mrb_obj_value(p);
+  init_copy(mrb, dup, obj);
+
+  return dup;
+}
+
 /* implementation of __id__ */
 mrb_value mrb_obj_id_m(mrb_state *mrb, mrb_value self);
 /* implementation of instance_eval */
@@ -2229,29 +2720,27 @@ static const mrb_code new_iseq[] = {
   OP_RETURN, 0x0             /* OP_RETURN    R0 */
 };
 
+const mrb_sym new_syms[] = { MRB_SYM(allocate), MRB_SYM(initialize) };
+static const mrb_irep new_irep = {
+  3, 6, 0, MRB_IREP_STATIC,
+  new_iseq, NULL, new_syms, NULL, NULL, NULL,
+  sizeof(new_iseq), 0, 2, 0, 0,
+};
+
 static void
 init_class_new(mrb_state *mrb, struct RClass *cls)
 {
   struct RProc *p;
   mrb_method_t m;
-  mrb_irep *new_irep = (mrb_irep*)mrb_malloc(mrb, sizeof(mrb_irep));
-  static const mrb_irep mrb_irep_zero = { 0 };
-
-  *new_irep = mrb_irep_zero;
-  new_irep->syms = (mrb_sym*)mrb_malloc(mrb, sizeof(mrb_sym)*2);
-  new_irep->syms[0] = mrb_intern_lit(mrb, "allocate");
-  new_irep->syms[1] = mrb_intern_lit(mrb, "initialize");
-  new_irep->slen = 2;
-  new_irep->flags = MRB_ISEQ_NO_FREE;
-  new_irep->iseq = new_iseq;
-  new_irep->ilen = sizeof(new_iseq);
-  new_irep->nregs = 6;
-  new_irep->nlocals = 3;
-  p = mrb_proc_new(mrb, new_irep);
+
+  p = mrb_proc_new(mrb, &new_irep);
   MRB_METHOD_FROM_PROC(m, p);
-  mrb_define_method_raw(mrb, cls, mrb_intern_lit(mrb, "new"), m);
+  mrb_define_method_raw(mrb, cls, MRB_SYM(new), m);
 }
 
+/* implementation of #send method */
+mrb_value mrb_f_send(mrb_state *mrb, mrb_value self);
+
 void
 mrb_init_class(mrb_state *mrb)
 {
@@ -2273,16 +2762,16 @@ mrb_init_class(mrb_state *mrb)
   make_metaclass(mrb, cls);
 
   /* name basic classes */
-  mrb_define_const(mrb, bob, "BasicObject", mrb_obj_value(bob));
-  mrb_define_const(mrb, obj, "Object",      mrb_obj_value(obj));
-  mrb_define_const(mrb, obj, "Module",      mrb_obj_value(mod));
-  mrb_define_const(mrb, obj, "Class",       mrb_obj_value(cls));
+  mrb_define_const_id(mrb, bob, MRB_SYM(BasicObject), mrb_obj_value(bob));
+  mrb_define_const_id(mrb, obj, MRB_SYM(Object),      mrb_obj_value(obj));
+  mrb_define_const_id(mrb, obj, MRB_SYM(Module),      mrb_obj_value(mod));
+  mrb_define_const_id(mrb, obj, MRB_SYM(Class),       mrb_obj_value(cls));
 
   /* name each classes */
-  mrb_class_name_class(mrb, NULL, bob, mrb_intern_lit(mrb, "BasicObject"));
-  mrb_class_name_class(mrb, NULL, obj, mrb_intern_lit(mrb, "Object")); /* 15.2.1 */
-  mrb_class_name_class(mrb, NULL, mod, mrb_intern_lit(mrb, "Module")); /* 15.2.2 */
-  mrb_class_name_class(mrb, NULL, cls, mrb_intern_lit(mrb, "Class"));  /* 15.2.3 */
+  mrb_class_name_class(mrb, NULL, bob, MRB_SYM(BasicObject));
+  mrb_class_name_class(mrb, NULL, obj, MRB_SYM(Object)); /* 15.2.1 */
+  mrb_class_name_class(mrb, NULL, mod, MRB_SYM(Module)); /* 15.2.2 */
+  mrb_class_name_class(mrb, NULL, cls, MRB_SYM(Class));  /* 15.2.3 */
 
   mrb->proc_class = mrb_define_class(mrb, "Proc", mrb->object_class);  /* 15.2.17 */
   MRB_SET_INSTANCE_TT(mrb->proc_class, MRB_TT_PROC);
diff --git a/src/codedump.c b/src/codedump.c
index 649be176b..3f0801929 100644
--- a/src/codedump.c
+++ b/src/codedump.c
@@ -4,26 +4,20 @@
 #include <mruby/opcode.h>
 #include <mruby/string.h>
 #include <mruby/proc.h>
+#include <mruby/dump.h>
 
 #ifndef MRB_DISABLE_STDIO
 static void
-print_r(mrb_state *mrb, mrb_irep *irep, size_t n)
+print_r(mrb_state *mrb, const mrb_irep *irep, size_t n)
 {
-  size_t i;
-
   if (n == 0) return;
-
-  for (i=0; i+1<irep->nlocals; i++) {
-    if (irep->lv[i].r == n) {
-      mrb_sym sym = irep->lv[i].name;
-      printf(" R%d:%s", (int)n, mrb_sym_dump(mrb, sym));
-      break;
-    }
-  }
+  if (n > irep->nlocals) return;
+  if (!irep->lv[n-1]) return;
+  printf(" R%d:%s", (int)n, mrb_sym_dump(mrb, irep->lv[n-1]));
 }
 
 static void
-print_lv_a(mrb_state *mrb, mrb_irep *irep, uint16_t a)
+print_lv_a(mrb_state *mrb, const mrb_irep *irep, uint16_t a)
 {
   if (!irep->lv || a >= irep->nlocals || a == 0) {
     printf("\n");
@@ -35,7 +29,7 @@ print_lv_a(mrb_state *mrb, mrb_irep *irep, uint16_t a)
 }
 
 static void
-print_lv_ab(mrb_state *mrb, mrb_irep *irep, uint16_t a, uint16_t b)
+print_lv_ab(mrb_state *mrb, const mrb_irep *irep, uint16_t a, uint16_t b)
 {
   if (!irep->lv || (a >= irep->nlocals && b >= irep->nlocals) || a+b == 0) {
     printf("\n");
@@ -48,7 +42,7 @@ print_lv_ab(mrb_state *mrb, mrb_irep *irep, uint16_t a, uint16_t b)
 }
 
 static void
-print_header(mrb_state *mrb, mrb_irep *irep, ptrdiff_t i)
+print_header(mrb_state *mrb, const mrb_irep *irep, ptrdiff_t i)
 {
   int32_t line;
 
@@ -63,10 +57,10 @@ print_header(mrb_state *mrb, mrb_irep *irep, ptrdiff_t i)
   printf("%03d ", (int)i);
 }
 
-#define CASE(insn,ops) case insn: FETCH_ ## ops (); L_ ## insn
+#define CASE(insn,ops) case insn: FETCH_ ## ops ();
 
 static void
-codedump(mrb_state *mrb, mrb_irep *irep)
+codedump(mrb_state *mrb, const mrb_irep *irep)
 {
   int ai;
   const mrb_code *pc, *pcend;
@@ -82,9 +76,36 @@ codedump(mrb_state *mrb, mrb_irep *irep)
 
     printf("local variable names:\n");
     for (i = 1; i < irep->nlocals; ++i) {
-      char const *s = mrb_sym_dump(mrb, irep->lv[i - 1].name);
-      int n = irep->lv[i - 1].r ? irep->lv[i - 1].r : i;
-      printf("  R%d:%s\n", n, s ? s : "");
+      char const *s = mrb_sym_dump(mrb, irep->lv[i - 1]);
+      printf("  R%d:%s\n", i, s ? s : "");
+    }
+  }
+
+  if (irep->clen > 0) {
+    int i = irep->clen;
+    const struct mrb_irep_catch_handler *e = mrb_irep_catch_handler_table(irep);
+
+    for (; i > 0; i --, e ++) {
+      int begin = bin_to_uint16(e->begin);
+      int end = bin_to_uint16(e->end);
+      int target = bin_to_uint16(e->target);
+      char buf[20];
+      const char *type;
+
+      switch (e->type) {
+        case MRB_CATCH_RESCUE:
+          type = "rescue";
+          break;
+        case MRB_CATCH_ENSURE:
+          type = "ensure";
+          break;
+        default:
+          buf[0] = '\0';
+          snprintf(buf, sizeof(buf), "0x%02x <unknown>", (int)e->type);
+          type = buf;
+          break;
+      }
+      printf("catch type: %-8s begin: %04d end: %04d target: %04d\n", type, begin, end, target);
     }
   }
 
@@ -107,159 +128,173 @@ codedump(mrb_state *mrb, mrb_irep *irep)
     print_header(mrb, irep, i);
     ins = READ_B();
     switch (ins) {
-    CASE(OP_NOP, Z):
+    CASE(OP_NOP, Z);
       printf("OP_NOP\n");
       break;
-    CASE(OP_MOVE, BB):
+    CASE(OP_MOVE, BB);
       printf("OP_MOVE\tR%d\tR%d\t", a, b);
       print_lv_ab(mrb, irep, a, b);
       break;
-    CASE(OP_LOADL, BB):
-      {
-        mrb_value v = irep->pool[b];
-        mrb_value s = mrb_inspect(mrb, v);
-        printf("OP_LOADL\tR%d\tL(%d)\t; %s", a, b, RSTRING_PTR(s));
+    CASE(OP_LOADL, BB);
+      switch (irep->pool[b].tt) {
+      case IREP_TT_FLOAT:
+        printf("OP_LOADL\tR%d\tL(%d)\t; %f", a, b, (double)irep->pool[b].u.f);
+        break;
+      case IREP_TT_INT32:
+        printf("OP_LOADL\tR%d\tL(%d)\t; %" PRId32, a, b, irep->pool[b].u.i32);
+        break;
+#ifdef MRB_64BIT
+      case IREP_TT_INT64:
+        printf("OP_LOADL\tR%d\tL(%d)\t; %" PRId64, a, b, irep->pool[b].u.i64);
+        break;
+#endif
+      default:
+        printf("OP_LOADL\tR%d\tL(%d)\t", a, b);
+        break;
       }
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_LOADI, BB):
+    CASE(OP_LOADI, BB);
       printf("OP_LOADI\tR%d\t%d\t", a, b);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_LOADINEG, BB):
+    CASE(OP_LOADINEG, BB);
       printf("OP_LOADI\tR%d\t-%d\t", a, b);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_LOADI16, BS):
+    CASE(OP_LOADI16, BS);
       printf("OP_LOADI16\tR%d\t%d\t", a, (int)(int16_t)b);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_LOADI__1, B):
+    CASE(OP_LOADI__1, B);
       printf("OP_LOADI__1\tR%d\t\t", a);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_LOADI_0, B): goto L_LOADI;
-    CASE(OP_LOADI_1, B): goto L_LOADI;
-    CASE(OP_LOADI_2, B): goto L_LOADI;
-    CASE(OP_LOADI_3, B): goto L_LOADI;
-    CASE(OP_LOADI_4, B): goto L_LOADI;
-    CASE(OP_LOADI_5, B): goto L_LOADI;
-    CASE(OP_LOADI_6, B): goto L_LOADI;
-    CASE(OP_LOADI_7, B):
+    CASE(OP_LOADI_0, B); goto L_LOADI;
+    CASE(OP_LOADI_1, B); goto L_LOADI;
+    CASE(OP_LOADI_2, B); goto L_LOADI;
+    CASE(OP_LOADI_3, B); goto L_LOADI;
+    CASE(OP_LOADI_4, B); goto L_LOADI;
+    CASE(OP_LOADI_5, B); goto L_LOADI;
+    CASE(OP_LOADI_6, B); goto L_LOADI;
+    CASE(OP_LOADI_7, B);
     L_LOADI:
       printf("OP_LOADI_%d\tR%d\t\t", ins-(int)OP_LOADI_0, a);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_LOADSYM, BB):
+    CASE(OP_LOADSYM, BB);
       printf("OP_LOADSYM\tR%d\t:%s\t", a, mrb_sym_dump(mrb, irep->syms[b]));
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_LOADNIL, B):
+    CASE(OP_LOADNIL, B);
       printf("OP_LOADNIL\tR%d\t\t", a);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_LOADSELF, B):
+    CASE(OP_LOADSELF, B);
       printf("OP_LOADSELF\tR%d\t\t", a);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_LOADT, B):
+    CASE(OP_LOADT, B);
       printf("OP_LOADT\tR%d\t\t", a);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_LOADF, B):
+    CASE(OP_LOADF, B);
       printf("OP_LOADF\tR%d\t\t", a);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_GETGV, BB):
+    CASE(OP_GETGV, BB);
       printf("OP_GETGV\tR%d\t:%s", a, mrb_sym_dump(mrb, irep->syms[b]));
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_SETGV, BB):
-      printf("OP_SETGV\t:%s\tR%d", mrb_sym_dump(mrb, irep->syms[b]), a);
+    CASE(OP_SETGV, BB);
+      printf("OP_SETGV\t;%s\tR%d", mrb_sym_dump(mrb, irep->syms[b]), a);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_GETSV, BB):
+    CASE(OP_GETSV, BB);
       printf("OP_GETSV\tR%d\t:%s", a, mrb_sym_dump(mrb, irep->syms[b]));
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_SETSV, BB):
+    CASE(OP_SETSV, BB);
       printf("OP_SETSV\t:%s\tR%d", mrb_sym_dump(mrb, irep->syms[b]), a);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_GETCONST, BB):
+    CASE(OP_GETCONST, BB);
       printf("OP_GETCONST\tR%d\t:%s", a, mrb_sym_dump(mrb, irep->syms[b]));
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_SETCONST, BB):
+    CASE(OP_SETCONST, BB);
       printf("OP_SETCONST\t:%s\tR%d", mrb_sym_dump(mrb, irep->syms[b]), a);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_GETMCNST, BB):
+    CASE(OP_GETMCNST, BB);
       printf("OP_GETMCNST\tR%d\tR%d::%s", a, a, mrb_sym_dump(mrb, irep->syms[b]));
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_SETMCNST, BB):
+    CASE(OP_SETMCNST, BB);
       printf("OP_SETMCNST\tR%d::%s\tR%d", a+1, mrb_sym_dump(mrb, irep->syms[b]), a);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_GETIV, BB):
+    CASE(OP_GETIV, BB);
       printf("OP_GETIV\tR%d\t%s", a, mrb_sym_dump(mrb, irep->syms[b]));
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_SETIV, BB):
+    CASE(OP_SETIV, BB);
       printf("OP_SETIV\t%s\tR%d", mrb_sym_dump(mrb, irep->syms[b]), a);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_GETUPVAR, BBB):
+    CASE(OP_GETUPVAR, BBB);
       printf("OP_GETUPVAR\tR%d\t%d\t%d", a, b, c);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_SETUPVAR, BBB):
+    CASE(OP_SETUPVAR, BBB);
       printf("OP_SETUPVAR\tR%d\t%d\t%d", a, b, c);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_GETCV, BB):
+    CASE(OP_GETCV, BB);
       printf("OP_GETCV\tR%d\t%s", a, mrb_sym_dump(mrb, irep->syms[b]));
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_SETCV, BB):
+    CASE(OP_SETCV, BB);
       printf("OP_SETCV\t%s\tR%d", mrb_sym_dump(mrb, irep->syms[b]), a);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_JMP, S):
+    CASE(OP_JMP, S);
       printf("OP_JMP\t\t%03d\n", a);
       break;
-    CASE(OP_JMPIF, BS):
+    CASE(OP_JMPUW, S);
+      printf("OP_JMPUW\t\t%03d\n", a);
+      break;
+    CASE(OP_JMPIF, BS);
       printf("OP_JMPIF\tR%d\t%03d\t", a, b);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_JMPNOT, BS):
+    CASE(OP_JMPNOT, BS);
       printf("OP_JMPNOT\tR%d\t%03d\t", a, b);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_JMPNIL, BS):
+    CASE(OP_JMPNIL, BS);
       printf("OP_JMPNIL\tR%d\t%03d\t", a, b);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_SENDV, BB):
+    CASE(OP_SENDV, BB);
       printf("OP_SENDV\tR%d\t:%s\n", a, mrb_sym_dump(mrb, irep->syms[b]));
       break;
-    CASE(OP_SENDVB, BB):
+    CASE(OP_SENDVB, BB);
       printf("OP_SENDVB\tR%d\t:%s\n", a, mrb_sym_dump(mrb, irep->syms[b]));
       break;
-    CASE(OP_SEND, BBB):
+    CASE(OP_SEND, BBB);
       printf("OP_SEND\tR%d\t:%s\t%d\n", a, mrb_sym_dump(mrb, irep->syms[b]), c);
       break;
-    CASE(OP_SENDB, BBB):
+    CASE(OP_SENDB, BBB);
       printf("OP_SENDB\tR%d\t:%s\t%d\n", a, mrb_sym_dump(mrb, irep->syms[b]), c);
       break;
-    CASE(OP_CALL, Z):
+    CASE(OP_CALL, Z);
       printf("OP_CALL\n");
       break;
-    CASE(OP_SUPER, BB):
+    CASE(OP_SUPER, BB);
       printf("OP_SUPER\tR%d\t%d\n", a, b);
       break;
-    CASE(OP_ARGARY, BS):
+    CASE(OP_ARGARY, BS);
       printf("OP_ARGARY\tR%d\t%d:%d:%d:%d (%d)", a,
              (b>>11)&0x3f,
              (b>>10)&0x1,
@@ -268,7 +303,7 @@ codedump(mrb_state *mrb, mrb_irep *irep)
              (b>>0)&0xf);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_ENTER, W):
+    CASE(OP_ENTER, W);
       printf("OP_ENTER\t%d:%d:%d:%d:%d:%d:%d\n",
              MRB_ASPEC_REQ(a),
              MRB_ASPEC_OPT(a),
@@ -278,30 +313,30 @@ codedump(mrb_state *mrb, mrb_irep *irep)
              MRB_ASPEC_KDICT(a),
              MRB_ASPEC_BLOCK(a));
       break;
-    CASE(OP_KEY_P, BB):
+    CASE(OP_KEY_P, BB);
       printf("OP_KEY_P\tR%d\t:%s\t", a, mrb_sym_dump(mrb, irep->syms[b]));
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_KEYEND, Z):
+    CASE(OP_KEYEND, Z);
       printf("OP_KEYEND\n");
       break;
-    CASE(OP_KARG, BB):
+    CASE(OP_KARG, BB);
       printf("OP_KARG\tR%d\t:%s\t", a, mrb_sym_dump(mrb, irep->syms[b]));
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_RETURN, B):
+    CASE(OP_RETURN, B);
       printf("OP_RETURN\tR%d\t\t", a);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_RETURN_BLK, B):
+    CASE(OP_RETURN_BLK, B);
       printf("OP_RETURN_BLK\tR%d\t\t", a);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_BREAK, B):
+    CASE(OP_BREAK, B);
       printf("OP_BREAK\tR%d\t\t", a);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_BLKPUSH, BS):
+    CASE(OP_BLKPUSH, BS);
       printf("OP_BLKPUSH\tR%d\t%d:%d:%d:%d (%d)", a,
              (b>>11)&0x3f,
              (b>>10)&0x1,
@@ -310,219 +345,178 @@ codedump(mrb_state *mrb, mrb_irep *irep)
              (b>>0)&0xf);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_LAMBDA, BB):
+    CASE(OP_LAMBDA, BB);
       printf("OP_LAMBDA\tR%d\tI(%d:%p)\n", a, b, irep->reps[b]);
       break;
-    CASE(OP_BLOCK, BB):
+    CASE(OP_BLOCK, BB);
       printf("OP_BLOCK\tR%d\tI(%d:%p)\n", a, b, irep->reps[b]);
       break;
-    CASE(OP_METHOD, BB):
+    CASE(OP_METHOD, BB);
       printf("OP_METHOD\tR%d\tI(%d:%p)\n", a, b, irep->reps[b]);
       break;
-    CASE(OP_RANGE_INC, B):
+    CASE(OP_RANGE_INC, B);
       printf("OP_RANGE_INC\tR%d\n", a);
       break;
-    CASE(OP_RANGE_EXC, B):
+    CASE(OP_RANGE_EXC, B);
       printf("OP_RANGE_EXC\tR%d\n", a);
       break;
-    CASE(OP_DEF, BB):
+    CASE(OP_DEF, BB);
       printf("OP_DEF\tR%d\t:%s\n", a, mrb_sym_dump(mrb, irep->syms[b]));
       break;
-    CASE(OP_UNDEF, B):
+    CASE(OP_UNDEF, B);
       printf("OP_UNDEF\t:%s\n", mrb_sym_dump(mrb, irep->syms[a]));
       break;
-    CASE(OP_ALIAS, BB):
+    CASE(OP_ALIAS, BB);
       printf("OP_ALIAS\t:%s\t%s\n", mrb_sym_dump(mrb, irep->syms[a]), mrb_sym_dump(mrb, irep->syms[b]));
       break;
-    CASE(OP_ADD, B):
+    CASE(OP_ADD, B);
       printf("OP_ADD\tR%d\t\n", a);
       break;
-    CASE(OP_ADDI, BB):
+    CASE(OP_ADDI, BB);
       printf("OP_ADDI\tR%d\t%d\n", a, b);
       break;
-    CASE(OP_SUB, B):
+    CASE(OP_SUB, B);
       printf("OP_SUB\tR%d\t\n", a);
       break;
-    CASE(OP_SUBI, BB):
+    CASE(OP_SUBI, BB);
       printf("OP_SUBI\tR%d\t%d\n", a, b);
       break;
-    CASE(OP_MUL, B):
+    CASE(OP_MUL, B);
       printf("OP_MUL\tR%d\t\n", a);
       break;
-    CASE(OP_DIV, B):
+    CASE(OP_DIV, B);
       printf("OP_DIV\tR%d\t\n", a);
       break;
-    CASE(OP_LT, B):
+    CASE(OP_LT, B);
       printf("OP_LT\t\tR%d\t\n", a);
       break;
-    CASE(OP_LE, B):
+    CASE(OP_LE, B);
       printf("OP_LE\t\tR%d\t\n", a);
       break;
-    CASE(OP_GT, B):
+    CASE(OP_GT, B);
       printf("OP_GT\t\tR%d\t\n", a);
       break;
-    CASE(OP_GE, B):
+    CASE(OP_GE, B);
       printf("OP_GE\t\tR%d\t\n", a);
       break;
-    CASE(OP_EQ, B):
+    CASE(OP_EQ, B);
       printf("OP_EQ\t\tR%d\t\n", a);
       break;
-    CASE(OP_ARRAY, BB):
+    CASE(OP_ARRAY, BB);
       printf("OP_ARRAY\tR%d\t%d\t", a, b);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_ARRAY2, BBB):
+    CASE(OP_ARRAY2, BBB);
       printf("OP_ARRAY\tR%d\tR%d\t%d\t", a, b, c);
       print_lv_ab(mrb, irep, a, b);
       break;
-    CASE(OP_ARYCAT, B):
+    CASE(OP_ARYCAT, B);
       printf("OP_ARYCAT\tR%d\t", a);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_ARYPUSH, B):
+    CASE(OP_ARYPUSH, B);
       printf("OP_ARYPUSH\tR%d\t", a);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_ARYDUP, B):
+    CASE(OP_ARYDUP, B);
       printf("OP_ARYDUP\tR%d\t", a);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_AREF, BBB):
+    CASE(OP_AREF, BBB);
       printf("OP_AREF\tR%d\tR%d\t%d", a, b, c);
       print_lv_ab(mrb, irep, a, b);
       break;
-    CASE(OP_ASET, BBB):
+    CASE(OP_ASET, BBB);
       printf("OP_ASET\tR%d\tR%d\t%d", a, b, c);
       print_lv_ab(mrb, irep, a, b);
       break;
-    CASE(OP_APOST, BBB):
+    CASE(OP_APOST, BBB);
       printf("OP_APOST\tR%d\t%d\t%d", a, b, c);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_INTERN, B):
+    CASE(OP_INTERN, B);
       printf("OP_INTERN\tR%d", a);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_STRING, BB):
-      {
-        mrb_value v = irep->pool[b];
-        mrb_value s = mrb_str_dump(mrb, mrb_str_new(mrb, RSTRING_PTR(v), RSTRING_LEN(v)));
-        printf("OP_STRING\tR%d\tL(%d)\t; %s", a, b, RSTRING_PTR(s));
+    CASE(OP_STRING, BB);
+      if ((irep->pool[b].tt & IREP_TT_NFLAG) == 0) {
+        printf("OP_STRING\tR%d\tL(%d)\t; %s", a, b, irep->pool[b].u.str);
+      }
+      else {
+        printf("OP_STRING\tR%d\tL(%d)\t", a, b);
       }
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_STRCAT, B):
+    CASE(OP_STRCAT, B);
       printf("OP_STRCAT\tR%d\t", a);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_HASH, BB):
+    CASE(OP_HASH, BB);
       printf("OP_HASH\tR%d\t%d\t", a, b);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_HASHADD, BB):
+    CASE(OP_HASHADD, BB);
       printf("OP_HASHADD\tR%d\t%d\t", a, b);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_HASHCAT, B):
+    CASE(OP_HASHCAT, B);
       printf("OP_HASHCAT\tR%d\t", a);
       print_lv_a(mrb, irep, a);
       break;
 
-    CASE(OP_OCLASS, B):
+    CASE(OP_OCLASS, B);
       printf("OP_OCLASS\tR%d\t\t", a);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_CLASS, BB):
+    CASE(OP_CLASS, BB);
       printf("OP_CLASS\tR%d\t:%s", a, mrb_sym_dump(mrb, irep->syms[b]));
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_MODULE, BB):
+    CASE(OP_MODULE, BB);
       printf("OP_MODULE\tR%d\t:%s", a, mrb_sym_dump(mrb, irep->syms[b]));
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_EXEC, BB):
+    CASE(OP_EXEC, BB);
       printf("OP_EXEC\tR%d\tI(%d:%p)", a, b, irep->reps[b]);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_SCLASS, B):
+    CASE(OP_SCLASS, B);
       printf("OP_SCLASS\tR%d\t", a);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_TCLASS, B):
+    CASE(OP_TCLASS, B);
       printf("OP_TCLASS\tR%d\t\t", a);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_ERR, B):
-      {
-        mrb_value v = irep->pool[a];
-        mrb_value s = mrb_str_dump(mrb, mrb_str_new(mrb, RSTRING_PTR(v), RSTRING_LEN(v)));
-        printf("OP_ERR\t%s\n", RSTRING_PTR(s));
+    CASE(OP_ERR, B);
+      if ((irep->pool[a].tt & IREP_TT_NFLAG) == 0) {
+        printf("OP_ERR\t%s\n", irep->pool[a].u.str);
+      }
+      else {
+        printf("OP_ERR\tL(%d)\n", a);
       }
       break;
-    CASE(OP_EPUSH, B):
-      printf("OP_EPUSH\t\t:I(%d:%p)\n", a, irep->reps[a]);
-      break;
-    CASE(OP_ONERR, S):
-      printf("OP_ONERR\t%03d\n", a);
-      break;
-    CASE(OP_EXCEPT, B):
+    CASE(OP_EXCEPT, B);
       printf("OP_EXCEPT\tR%d\t\t", a);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_RESCUE, BB):
+    CASE(OP_RESCUE, BB);
       printf("OP_RESCUE\tR%d\tR%d", a, b);
       print_lv_ab(mrb, irep, a, b);
       break;
-    CASE(OP_RAISE, B):
-      printf("OP_RAISE\tR%d\t\t", a);
+    CASE(OP_RAISEIF, B);
+      printf("OP_RAISEIF\tR%d\t\t", a);
       print_lv_a(mrb, irep, a);
       break;
-    CASE(OP_POPERR, B):
-      printf("OP_POPERR\t%d\t\t\n", a);
-      break;
-    CASE(OP_EPOP, B):
-      printf("OP_EPOP\t%d\n", a);
-      break;
 
-    CASE(OP_DEBUG, BBB):
+    CASE(OP_DEBUG, BBB);
       printf("OP_DEBUG\t%d\t%d\t%d\n", a, b, c);
       break;
 
-    CASE(OP_STOP, Z):
+    CASE(OP_STOP, Z);
       printf("OP_STOP\n");
       break;
 
-    CASE(OP_EXT1, Z):
-      ins = READ_B();
-      printf("OP_EXT1\n");
-      print_header(mrb, irep, pc-irep->iseq-2);
-      switch (ins) {
-#define OPCODE(i,x) case OP_ ## i: FETCH_ ## x ## _1 (); goto L_OP_ ## i;
-#include "mruby/ops.h"
-#undef OPCODE
-      }
-      break;
-    CASE(OP_EXT2, Z):
-      ins = READ_B();
-      printf("OP_EXT2\n");
-      print_header(mrb, irep, pc-irep->iseq-2);
-      switch (ins) {
-#define OPCODE(i,x) case OP_ ## i: FETCH_ ## x ## _2 (); goto L_OP_ ## i;
-#include "mruby/ops.h"
-#undef OPCODE
-      }
-      break;
-    CASE(OP_EXT3, Z):
-      ins = READ_B();
-      printf("OP_EXT3\n");
-      print_header(mrb, irep, pc-irep->iseq-2);
-      switch (ins) {
-#define OPCODE(i,x) case OP_ ## i: FETCH_ ## x ## _3 (); goto L_OP_ ## i;
-#include "mruby/ops.h"
-#undef OPCODE
-      }
-      break;
-
     default:
       printf("OP_unknown (0x%x)\n", ins);
       break;
@@ -533,7 +527,7 @@ codedump(mrb_state *mrb, mrb_irep *irep)
 }
 
 static void
-codedump_recur(mrb_state *mrb, mrb_irep *irep)
+codedump_recur(mrb_state *mrb, const mrb_irep *irep)
 {
   int i;
 
diff --git a/src/debug.c b/src/debug.c
index 32add68ae..dabc5a56d 100644
--- a/src/debug.c
+++ b/src/debug.c
@@ -51,7 +51,7 @@ select_line_type(const uint16_t *lines, size_t lines_len)
 }
 
 MRB_API char const*
-mrb_debug_get_filename(mrb_state *mrb, mrb_irep *irep, ptrdiff_t pc)
+mrb_debug_get_filename(mrb_state *mrb, const mrb_irep *irep, ptrdiff_t pc)
 {
   if (irep && pc >= 0 && pc < irep->ilen) {
     mrb_irep_debug_info_file* f = NULL;
diff --git a/src/dump.c b/src/dump.c
index a6bbe68f3..2bc1b0a53 100644
--- a/src/dump.c
+++ b/src/dump.c
@@ -13,32 +13,18 @@
 #include <mruby/numeric.h>
 #include <mruby/debug.h>
 
-#ifndef MRB_WITHOUT_FLOAT
-#ifdef MRB_USE_FLOAT
-#define MRB_FLOAT_FMT "%.9g"
-#else
+#ifndef MRB_NO_FLOAT
+#include <mruby/endian.h>
 #define MRB_FLOAT_FMT "%.17g"
 #endif
-#endif
 
-static size_t get_irep_record_size_1(mrb_state *mrb, mrb_irep *irep);
+static size_t get_irep_record_size_1(mrb_state *mrb, const mrb_irep *irep);
 
 #if UINT32_MAX > SIZE_MAX
 # error This code cannot be built on your environment.
 #endif
 
 static size_t
-write_padding(uint8_t *buf)
-{
-  const size_t align = MRB_DUMP_ALIGNMENT;
-  size_t pad_len = -(intptr_t)buf & (align-1);
-  if (pad_len > 0) {
-    memset(buf, 0, pad_len);
-  }
-  return pad_len;
-}
-
-static size_t
 get_irep_header_size(mrb_state *mrb)
 {
   size_t size = 0;
@@ -50,7 +36,7 @@ get_irep_header_size(mrb_state *mrb)
 }
 
 static ptrdiff_t
-write_irep_header(mrb_state *mrb, mrb_irep *irep, uint8_t *buf)
+write_irep_header(mrb_state *mrb, const mrb_irep *irep, uint8_t *buf)
 {
   uint8_t *cur = buf;
 
@@ -64,87 +50,97 @@ write_irep_header(mrb_state *mrb, mrb_irep *irep, uint8_t *buf)
 
 
 static size_t
-get_iseq_block_size(mrb_state *mrb, mrb_irep *irep)
+get_iseq_block_size(mrb_state *mrb, const mrb_irep *irep)
 {
   size_t size = 0;
 
-  size += sizeof(uint32_t); /* ilen */
-  size += sizeof(uint32_t); /* max padding */
-  size += sizeof(uint32_t) * irep->ilen; /* iseq(n) */
+  size += sizeof(uint16_t); /* ilen */
+  size += irep->ilen * sizeof(mrb_code); /* iseq(n) */
 
   return size;
 }
 
 static ptrdiff_t
-write_iseq_block(mrb_state *mrb, mrb_irep *irep, uint8_t *buf, uint8_t flags)
+write_iseq_block(mrb_state *mrb, const mrb_irep *irep, uint8_t *buf, uint8_t flags)
 {
   uint8_t *cur = buf;
 
-  cur += uint32_to_bin(irep->ilen, cur); /* number of opcode */
-  cur += write_padding(cur);
+  cur += uint16_to_bin(irep->ilen, cur); /* number of opcode */
   memcpy(cur, irep->iseq, irep->ilen * sizeof(mrb_code));
   cur += irep->ilen * sizeof(mrb_code);
 
   return cur - buf;
 }
 
-#ifndef MRB_WITHOUT_FLOAT
-static mrb_value
-float_to_str(mrb_state *mrb, mrb_value flt)
+#ifndef MRB_NO_FLOAT
+static void
+dump_float(mrb_state *mrb, uint8_t *buf, mrb_float f)
 {
-  mrb_float f = mrb_float(flt);
+  /* dump IEEE754 binary in little endian */
+  union {
+    double f;
+    char s[sizeof(double)];
+  } u = {.f = (double)f};
+
+  if (littleendian) {
+    memcpy(buf, u.s, sizeof(double));
+  }
+  else {
+    size_t i;
 
-  if (isinf(f)) {
-    return f < 0 ? mrb_str_new_lit(mrb, "I") : mrb_str_new_lit(mrb, "i");
+    for (i=0; i<sizeof(double); i++) {
+      buf[i] = u.s[sizeof(double)-i-1];
+    }
   }
-  return  mrb_float_to_str(mrb, flt, MRB_FLOAT_FMT);
 }
 #endif
 
 static size_t
-get_pool_block_size(mrb_state *mrb, mrb_irep *irep)
+get_pool_block_size(mrb_state *mrb, const mrb_irep *irep)
 {
   int pool_no;
   size_t size = 0;
-  mrb_value str;
 
-  size += sizeof(uint32_t); /* plen */
-  size += irep->plen * (sizeof(uint8_t) + sizeof(uint16_t)); /* len(n) */
+  size += sizeof(uint16_t); /* plen */
+  size += irep->plen * sizeof(uint8_t); /* len(n) */
 
   for (pool_no = 0; pool_no < irep->plen; pool_no++) {
     int ai = mrb_gc_arena_save(mrb);
 
-    switch (mrb_type(irep->pool[pool_no])) {
-    case MRB_TT_FIXNUM:
-      str = mrb_fixnum_to_str(mrb, irep->pool[pool_no], 10);
+    switch (irep->pool[pool_no].tt) {
+    case IREP_TT_INT64:
+#ifdef MRB_64BIT
       {
-        mrb_int len = RSTRING_LEN(str);
-        mrb_assert_int_fit(mrb_int, len, size_t, SIZE_MAX);
-        size += (size_t)len;
+        int64_t i = irep->pool[pool_no].u.i64;
+
+        if (i < INT32_MIN || INT32_MAX < i)
+          size += 8;
+        else
+          size += 4;
       }
       break;
+#else
+      /* fall through */
+#endif
+    case IREP_TT_INT32:
+      size += 4;                /* 32bits = 4bytes */
+      break;
 
-#ifndef MRB_WITHOUT_FLOAT
-    case MRB_TT_FLOAT:
-      str = float_to_str(mrb, irep->pool[pool_no]);
+    case IREP_TT_FLOAT:
+#ifndef MRB_NO_FLOAT
       {
-        mrb_int len = RSTRING_LEN(str);
-        mrb_assert_int_fit(mrb_int, len, size_t, SIZE_MAX);
-        size += (size_t)len;
+        size += sizeof(double);
       }
-      break;
 #endif
+      break;
 
-    case MRB_TT_STRING:
+    default: /*  packed IREP_TT_STRING */ 
       {
-        mrb_int len = RSTRING_LEN(irep->pool[pool_no]);
+        mrb_int len = irep->pool[pool_no].tt >> 1; /* unpack length */
         mrb_assert_int_fit(mrb_int, len, size_t, SIZE_MAX);
-        size += (size_t)len;
+        size += (size_t)len+1;
       }
       break;
-
-    default:
-      break;
     }
     mrb_gc_arena_restore(mrb, ai);
   }
@@ -153,52 +149,63 @@ get_pool_block_size(mrb_state *mrb, mrb_irep *irep)
 }
 
 static ptrdiff_t
-write_pool_block(mrb_state *mrb, mrb_irep *irep, uint8_t *buf)
+write_pool_block(mrb_state *mrb, const mrb_irep *irep, uint8_t *buf)
 {
   int pool_no;
   uint8_t *cur = buf;
-  uint16_t len;
-  mrb_value str;
-  const char *char_ptr;
+  mrb_int len;
+  const char *ptr;
 
-  cur += uint32_to_bin(irep->plen, cur); /* number of pool */
+  cur += uint16_to_bin(irep->plen, cur); /* number of pool */
 
   for (pool_no = 0; pool_no < irep->plen; pool_no++) {
     int ai = mrb_gc_arena_save(mrb);
 
-    switch (mrb_type(irep->pool[pool_no])) {
-    case MRB_TT_FIXNUM:
-      cur += uint8_to_bin(IREP_TT_FIXNUM, cur); /* data type */
-      str = mrb_fixnum_to_str(mrb, irep->pool[pool_no], 10);
+    switch (irep->pool[pool_no].tt) {
+#ifdef MRB_64BIT
+    case IREP_TT_INT64:
+      {
+        int64_t i = irep->pool[pool_no].u.i64;
+        if (i < INT32_MIN || INT32_MAX < i) {
+          cur += uint8_to_bin(IREP_TT_INT64, cur); /* data type */
+          cur += uint32_to_bin((uint32_t)((i>>32) & 0xffffffff), cur); /* i64 hi */
+          cur += uint32_to_bin((uint32_t)((i    ) & 0xffffffff), cur); /* i64 lo */
+        }
+        else {
+          cur += uint8_to_bin(IREP_TT_INT32, cur); /* data type */
+          cur += uint32_to_bin(irep->pool[pool_no].u.i32, cur); /* i32 */
+        }
+      }
+      break;
+#endif
+    case IREP_TT_INT32:
+      cur += uint8_to_bin(IREP_TT_INT32, cur); /* data type */
+      cur += uint32_to_bin(irep->pool[pool_no].u.i32, cur); /* i32 */
       break;
 
-#ifndef MRB_WITHOUT_FLOAT
-    case MRB_TT_FLOAT:
+    case IREP_TT_FLOAT:
       cur += uint8_to_bin(IREP_TT_FLOAT, cur); /* data type */
-      str = float_to_str(mrb, irep->pool[pool_no]);
-      break;
+#ifndef MRB_NO_FLOAT
+      {
+        dump_float(mrb, cur,irep->pool[pool_no].u.f);
+        cur += sizeof(double);
+      }
+#else
+      cur += uint16_to_bin(0, cur); /* zero length */
 #endif
-
-    case MRB_TT_STRING:
-      cur += uint8_to_bin(IREP_TT_STRING, cur); /* data type */
-      str = irep->pool[pool_no];
       break;
 
-    default:
-      continue;
-    }
-
-    char_ptr = RSTRING_PTR(str);
-    {
-      mrb_int tlen = RSTRING_LEN(str);
-      mrb_assert_int_fit(mrb_int, tlen, uint16_t, UINT16_MAX);
-      len = (uint16_t)tlen;
+    default: /* string */
+      cur += uint8_to_bin(IREP_TT_STR, cur); /* data type */
+      ptr = irep->pool[pool_no].u.str;
+      len = irep->pool[pool_no].tt>>2;
+      mrb_assert_int_fit(mrb_int, len, uint16_t, UINT16_MAX);
+      cur += uint16_to_bin((uint16_t)len, cur); /* data length */
+      memcpy(cur, ptr, (size_t)len);
+      cur += len;
+      *cur++ = '\0';
+      break;
     }
-
-    cur += uint16_to_bin(len, cur); /* data length */
-    memcpy(cur, char_ptr, (size_t)len);
-    cur += len;
-
     mrb_gc_arena_restore(mrb, ai);
   }
 
@@ -207,13 +214,13 @@ write_pool_block(mrb_state *mrb, mrb_irep *irep, uint8_t *buf)
 
 
 static size_t
-get_syms_block_size(mrb_state *mrb, mrb_irep *irep)
+get_syms_block_size(mrb_state *mrb, const mrb_irep *irep)
 {
   size_t size = 0;
   int sym_no;
   mrb_int len;
 
-  size += sizeof(uint32_t); /* slen */
+  size += sizeof(uint16_t); /* slen */
   for (sym_no = 0; sym_no < irep->slen; sym_no++) {
     size += sizeof(uint16_t); /* snl(n) */
     if (irep->syms[sym_no] != 0) {
@@ -226,13 +233,13 @@ get_syms_block_size(mrb_state *mrb, mrb_irep *irep)
 }
 
 static ptrdiff_t
-write_syms_block(mrb_state *mrb, mrb_irep *irep, uint8_t *buf)
+write_syms_block(mrb_state *mrb, const mrb_irep *irep, uint8_t *buf)
 {
   int sym_no;
   uint8_t *cur = buf;
   const char *name;
 
-  cur += uint32_to_bin(irep->slen, cur); /* number of symbol */
+  cur += uint16_to_bin(irep->slen, cur); /* number of symbol */
 
   for (sym_no = 0; sym_no < irep->slen; sym_no++) {
     if (irep->syms[sym_no] != 0) {
@@ -255,19 +262,46 @@ write_syms_block(mrb_state *mrb, mrb_irep *irep, uint8_t *buf)
 }
 
 static size_t
-get_irep_record_size_1(mrb_state *mrb, mrb_irep *irep)
+get_catch_table_block_size(mrb_state *mrb, const mrb_irep *irep)
+{
+  size_t size = 0;
+
+  size += sizeof(uint16_t); /* number of catch handler */
+  size += (sizeof(struct mrb_irep_catch_handler)) * irep->clen;
+
+  return size;
+}
+
+static ptrdiff_t
+write_catch_table_block(mrb_state *mrb, const mrb_irep *irep, uint8_t *buf)
+{
+  uint8_t *cur = buf;
+  const struct mrb_irep_catch_handler *e = mrb_irep_catch_handler_table(irep);
+  mrb_static_assert1(sizeof(*e) == 7);
+
+  if (e == NULL) return 0;
+  /* irep->clen has already been written before iseq block */
+  memcpy(cur, (const void *)e, sizeof(*e) * irep->clen);
+  cur += sizeof(*e) * irep->clen;
+
+  return cur - buf;
+}
+
+static size_t
+get_irep_record_size_1(mrb_state *mrb, const mrb_irep *irep)
 {
   size_t size = 0;
 
   size += get_irep_header_size(mrb);
   size += get_iseq_block_size(mrb, irep);
+  size += get_catch_table_block_size(mrb, irep);
   size += get_pool_block_size(mrb, irep);
   size += get_syms_block_size(mrb, irep);
   return size;
 }
 
 static size_t
-get_irep_record_size(mrb_state *mrb, mrb_irep *irep)
+get_irep_record_size(mrb_state *mrb, const mrb_irep *irep)
 {
   size_t size = 0;
   int irep_no;
@@ -280,7 +314,7 @@ get_irep_record_size(mrb_state *mrb, mrb_irep *irep)
 }
 
 static int
-write_irep_record(mrb_state *mrb, mrb_irep *irep, uint8_t *bin, size_t *irep_record_size, uint8_t flags)
+write_irep_record(mrb_state *mrb, const mrb_irep *irep, uint8_t *bin, size_t *irep_record_size, uint8_t flags)
 {
   int i;
   uint8_t *src = bin;
@@ -289,13 +323,14 @@ write_irep_record(mrb_state *mrb, mrb_irep *irep, uint8_t *bin, size_t *irep_rec
     return MRB_DUMP_INVALID_IREP;
   }
 
-  *irep_record_size = get_irep_record_size_1(mrb, irep);
-  if (*irep_record_size == 0) {
-    return MRB_DUMP_GENERAL_FAILURE;
-  }
-
   bin += write_irep_header(mrb, irep, bin);
+  /*
+   * The catch handler table is after iseq block, but the number of
+   * elements is placed before iseq block.
+   */
+  bin += uint16_to_bin(irep->clen, bin);
   bin += write_iseq_block(mrb, irep, bin, flags);
+  bin += write_catch_table_block(mrb, irep, bin);
   bin += write_pool_block(mrb, irep, bin);
   bin += write_syms_block(mrb, irep, bin);
 
@@ -341,7 +376,7 @@ write_section_irep_header(mrb_state *mrb, size_t section_size, uint8_t *bin)
 }
 
 static int
-write_section_irep(mrb_state *mrb, mrb_irep *irep, uint8_t *bin, size_t *len_p, uint8_t flags)
+write_section_irep(mrb_state *mrb, const mrb_irep *irep, uint8_t *bin, size_t *len_p, uint8_t flags)
 {
   int result;
   size_t rsize = 0;
@@ -364,7 +399,7 @@ write_section_irep(mrb_state *mrb, mrb_irep *irep, uint8_t *bin, size_t *len_p,
 }
 
 static size_t
-get_debug_record_size(mrb_state *mrb, mrb_irep *irep)
+get_debug_record_size(mrb_state *mrb, const mrb_irep *irep)
 {
   size_t ret = 0;
   uint16_t f_idx;
@@ -413,11 +448,11 @@ find_filename_index(const mrb_sym *ary, int ary_len, mrb_sym s)
 }
 
 static size_t
-get_filename_table_size(mrb_state *mrb, mrb_irep *irep, mrb_sym **fp, uint16_t *lp)
+get_filename_table_size(mrb_state *mrb, const mrb_irep *irep, mrb_sym **fp, uint16_t *lp)
 {
   mrb_sym *filenames = *fp;
   size_t size = 0;
-  mrb_irep_debug_info *di = irep->debug_info;
+  const mrb_irep_debug_info *di = irep->debug_info;
   int i;
 
   mrb_assert(lp);
@@ -444,7 +479,7 @@ get_filename_table_size(mrb_state *mrb, mrb_irep *irep, mrb_sym **fp, uint16_t *
 }
 
 static size_t
-write_debug_record_1(mrb_state *mrb, mrb_irep *irep, uint8_t *bin, mrb_sym const* filenames, uint16_t filenames_len)
+write_debug_record_1(mrb_state *mrb, const mrb_irep *irep, uint8_t *bin, mrb_sym const* filenames, uint16_t filenames_len)
 {
   uint8_t *cur;
   uint16_t f_idx;
@@ -498,7 +533,7 @@ write_debug_record_1(mrb_state *mrb, mrb_irep *irep, uint8_t *bin, mrb_sym const
 }
 
 static size_t
-write_debug_record(mrb_state *mrb, mrb_irep *irep, uint8_t *bin, mrb_sym const* filenames, uint16_t filenames_len)
+write_debug_record(mrb_state *mrb, const mrb_irep *irep, uint8_t *bin, mrb_sym const* filenames, uint16_t filenames_len)
 {
   size_t size, len;
   int irep_no;
@@ -516,7 +551,7 @@ write_debug_record(mrb_state *mrb, mrb_irep *irep, uint8_t *bin, mrb_sym const*
 }
 
 static int
-write_section_debug(mrb_state *mrb, mrb_irep *irep, uint8_t *cur, mrb_sym const *filenames, uint16_t filenames_len)
+write_section_debug(mrb_state *mrb, const mrb_irep *irep, uint8_t *cur, mrb_sym const *filenames, uint16_t filenames_len)
 {
   size_t section_size = 0;
   const uint8_t *bin = cur;
@@ -566,7 +601,7 @@ create_lv_sym_table(mrb_state *mrb, const mrb_irep *irep, mrb_sym **syms, uint32
   }
 
   for (i = 0; i + 1 < irep->nlocals; ++i) {
-    mrb_sym const name = irep->lv[i].name;
+    mrb_sym const name = irep->lv[i];
     if (name == 0) continue;
     if (find_filename_index(*syms, *syms_len, name) != -1) continue;
 
@@ -609,16 +644,14 @@ write_lv_record(mrb_state *mrb, const mrb_irep *irep, uint8_t **start, mrb_sym c
   int i;
 
   for (i = 0; i + 1 < irep->nlocals; ++i) {
-    if (irep->lv[i].name == 0) {
+    if (irep->lv[i] == 0) {
       cur += uint16_to_bin(RITE_LV_NULL_MARK, cur);
-      cur += uint16_to_bin(0, cur);
     }
     else {
-      int const sym_idx = find_filename_index(syms, syms_len, irep->lv[i].name);
+      int const sym_idx = find_filename_index(syms, syms_len, irep->lv[i]);
       mrb_assert(sym_idx != -1); /* local variable name must be in syms */
 
       cur += uint16_to_bin(sym_idx, cur);
-      cur += uint16_to_bin(irep->lv[i].r, cur);
     }
   }
 
@@ -632,12 +665,12 @@ write_lv_record(mrb_state *mrb, const mrb_irep *irep, uint8_t **start, mrb_sym c
 }
 
 static size_t
-get_lv_record_size(mrb_state *mrb, mrb_irep *irep)
+get_lv_record_size(mrb_state *mrb, const mrb_irep *irep)
 {
   size_t ret = 0;
   int i;
 
-  ret += (sizeof(uint16_t) + sizeof(uint16_t)) * (irep->nlocals - 1);
+  ret += sizeof(uint16_t) * (irep->nlocals - 1);
 
   for (i = 0; i < irep->rlen; ++i) {
     ret += get_lv_record_size(mrb, irep->reps[i]);
@@ -647,7 +680,7 @@ get_lv_record_size(mrb_state *mrb, mrb_irep *irep)
 }
 
 static size_t
-get_lv_section_size(mrb_state *mrb, mrb_irep *irep, mrb_sym const *syms, uint32_t syms_len)
+get_lv_section_size(mrb_state *mrb, const mrb_irep *irep, mrb_sym const *syms, uint32_t syms_len)
 {
   size_t ret = 0, i;
 
@@ -665,7 +698,7 @@ get_lv_section_size(mrb_state *mrb, mrb_irep *irep, mrb_sym const *syms, uint32_
 }
 
 static int
-write_section_lv(mrb_state *mrb, mrb_irep *irep, uint8_t *start, mrb_sym const *syms, uint32_t const syms_len)
+write_section_lv(mrb_state *mrb, const mrb_irep *irep, uint8_t *start, mrb_sym const *syms, uint32_t const syms_len)
 {
   uint8_t *cur = start;
   struct rite_section_lv_header *header;
@@ -707,7 +740,8 @@ write_rite_binary_header(mrb_state *mrb, size_t binary_size, uint8_t *bin, uint8
   uint32_t offset;
 
   memcpy(header->binary_ident, RITE_BINARY_IDENT, sizeof(header->binary_ident));
-  memcpy(header->binary_version, RITE_BINARY_FORMAT_VER, sizeof(header->binary_version));
+  memcpy(header->major_version, RITE_BINARY_MAJOR_VER, sizeof(header->major_version));
+  memcpy(header->minor_version, RITE_BINARY_MAJOR_VER, sizeof(header->minor_version));
   memcpy(header->compiler_name, RITE_COMPILER_NAME, sizeof(header->compiler_name));
   memcpy(header->compiler_version, RITE_COMPILER_VERSION, sizeof(header->compiler_version));
   mrb_assert(binary_size <= UINT32_MAX);
@@ -721,7 +755,7 @@ write_rite_binary_header(mrb_state *mrb, size_t binary_size, uint8_t *bin, uint8
 }
 
 static mrb_bool
-debug_info_defined_p(mrb_irep *irep)
+debug_info_defined_p(const mrb_irep *irep)
 {
   int i;
 
@@ -733,7 +767,7 @@ debug_info_defined_p(mrb_irep *irep)
 }
 
 static mrb_bool
-lv_defined_p(mrb_irep *irep)
+lv_defined_p(const mrb_irep *irep)
 {
   int i;
 
@@ -747,7 +781,7 @@ lv_defined_p(mrb_irep *irep)
 }
 
 static int
-dump_irep(mrb_state *mrb, mrb_irep *irep, uint8_t flags, uint8_t **bin, size_t *bin_size)
+dump_irep(mrb_state *mrb, const mrb_irep *irep, uint8_t flags, uint8_t **bin, size_t *bin_size)
 {
   int result = MRB_DUMP_GENERAL_FAILURE;
   size_t malloc_size;
@@ -835,7 +869,7 @@ error_exit:
 }
 
 int
-mrb_dump_irep(mrb_state *mrb, mrb_irep *irep, uint8_t flags, uint8_t **bin, size_t *bin_size)
+mrb_dump_irep(mrb_state *mrb, const mrb_irep *irep, uint8_t flags, uint8_t **bin, size_t *bin_size)
 {
   return dump_irep(mrb, irep, flags, bin, bin_size);
 }
@@ -843,7 +877,7 @@ mrb_dump_irep(mrb_state *mrb, mrb_irep *irep, uint8_t flags, uint8_t **bin, size
 #ifndef MRB_DISABLE_STDIO
 
 int
-mrb_dump_irep_binary(mrb_state *mrb, mrb_irep *irep, uint8_t flags, FILE* fp)
+mrb_dump_irep_binary(mrb_state *mrb, const mrb_irep *irep, uint8_t flags, FILE* fp)
 {
   uint8_t *bin = NULL;
   size_t bin_size = 0;
@@ -865,7 +899,7 @@ mrb_dump_irep_binary(mrb_state *mrb, mrb_irep *irep, uint8_t flags, FILE* fp)
 }
 
 int
-mrb_dump_irep_cfunc(mrb_state *mrb, mrb_irep *irep, uint8_t flags, FILE *fp, const char *initname)
+mrb_dump_irep_cfunc(mrb_state *mrb, const mrb_irep *irep, uint8_t flags, FILE *fp, const char *initname)
 {
   uint8_t *bin = NULL;
   size_t bin_size = 0, bin_idx = 0;
@@ -884,15 +918,8 @@ mrb_dump_irep_cfunc(mrb_state *mrb, mrb_irep *irep, uint8_t flags, FILE *fp, con
           "#ifdef __cplusplus\n"
           "extern const uint8_t %s[];\n"
           "#endif\n"
-          "const uint8_t\n"
-          "#if defined __GNUC__\n"
-          "__attribute__((aligned(%u)))\n"
-          "#elif defined _MSC_VER\n"
-          "__declspec(align(%u))\n"
-          "#endif\n"
-          "%s[] = {",
-          initname,
-          (uint16_t)MRB_DUMP_ALIGNMENT, (uint16_t)MRB_DUMP_ALIGNMENT, initname) < 0) {
+          "const uint8_t %s[] = {",
+          initname, initname) < 0) {
       mrb_free(mrb, bin);
       return MRB_DUMP_WRITE_FAULT;
     }
@@ -918,4 +945,171 @@ mrb_dump_irep_cfunc(mrb_state *mrb, mrb_irep *irep, uint8_t flags, FILE *fp, con
   return result;
 }
 
+static int
+dump_pool(mrb_state *mrb, const mrb_pool_value *p, FILE *fp)
+{
+  if (p->tt & IREP_TT_NFLAG) {  /* number */
+    switch (p->tt) {
+#ifdef MRB_64BIT
+    case IREP_TT_INT64:
+      if (p->u.i64 < INT32_MIN || INT32_MAX < p->u.i64) {
+        fprintf(fp, "{IREP_TT_INT64, {.i64=%" PRId64 "}},\n", p->u.i64);
+      }
+      else {
+        fprintf(fp, "{IREP_TT_INT32, {.i32=%" PRId32 "}},\n", (int32_t)p->u.i64);
+      }
+      break;
+#endif
+    case IREP_TT_INT32:
+      fprintf(fp, "{IREP_TT_INT32, {.i32=%" PRId32 "}},\n", p->u.i32);
+      break;
+    case IREP_TT_FLOAT:
+      if (p->u.f == 0) {
+        fprintf(fp, "{IREP_TT_FLOAT, {.f=%#.1f}},\n", p->u.f);
+      }
+      else {
+        fprintf(fp, "{IREP_TT_FLOAT, {.f=" MRB_FLOAT_FMT "}},\n", p->u.f);
+      }
+      break;
+    }
+  }
+  else {                        /* string */
+    int i, len = p->tt>>2;
+    const char *s = p->u.str;
+    fprintf(fp, "{IREP_TT_STR|(%d<<2), {\"", len);
+    for (i=0; i<len; i++) {
+      fprintf(fp, "\\x%02x", (int)s[i]&0xff);
+    }
+    fputs("\"}},\n", fp);
+  }
+  return MRB_DUMP_OK;
+}
+
+mrb_bool mrb_sym_static_p(mrb_state *mrb, mrb_sym sym);
+  
+static int
+dump_sym(mrb_state *mrb, mrb_sym sym, FILE *fp)
+{
+  const char *name;
+  if (sym == 0) return MRB_DUMP_INVALID_ARGUMENT;
+  name = mrb_sym_name(mrb, sym);
+  if (!name) {
+    fprintf(stderr, "undefined symbol (%d) - define presym\n", sym);
+  }
+  if (!mrb_sym_static_p(mrb, sym)) {
+    fprintf(stderr, "no static symbol (%s) - define presym\n", name);
+  }
+  fprintf(fp, "%d /* %s */,", sym, name);
+  return MRB_DUMP_OK;
+}
+
+static int
+dump_irep_struct(mrb_state *mrb, const mrb_irep *irep, uint8_t flags, FILE *fp, const char *name, int n, int *mp)
+{
+  int i, len;
+  int max = *mp;
+
+  /* dump reps */
+  if (irep->reps) {
+    for (i=0,len=irep->rlen; i<len; i++) {
+      *mp += len;
+      if (dump_irep_struct(mrb, irep->reps[i], flags, fp, name, max+i, mp) != MRB_DUMP_OK)
+        return MRB_DUMP_INVALID_ARGUMENT;
+    }
+    fprintf(fp,   "static const mrb_irep *%s_reps_%d[%d] = {\n", name, n, len);
+    for (i=0,len=irep->rlen; i<len; i++) {
+      fprintf(fp,   "  &%s_irep_%d,\n", name, max+i);
+    }
+    fputs("};\n", fp);
+  }
+  /* dump pool */
+  if (irep->pool) {
+    len=irep->plen;
+    fprintf(fp,   "static const mrb_pool_value %s_pool_%d[%d] = {\n", name, n, len);
+    for (i=0; i<len; i++) {
+      if (dump_pool(mrb, &irep->pool[i], fp) != MRB_DUMP_OK)
+        return MRB_DUMP_INVALID_ARGUMENT;
+    }
+    fputs("};\n", fp);
+  }
+  /* dump syms */
+  if (irep->syms) {
+    len=irep->slen;
+    fprintf(fp,   "static const mrb_sym %s_syms_%d[%d] = {", name, n, len);
+    for (i=0; i<len; i++) {
+      dump_sym(mrb, irep->syms[i], fp);
+    }
+    fputs("};\n", fp);
+  }
+  /* dump iseq */
+  len=irep->ilen+sizeof(struct mrb_irep_catch_handler)*irep->clen;
+  fprintf(fp,   "static const mrb_code %s_iseq_%d[%d] = {", name, n, len);
+  for (i=0; i<len; i++) {
+    if (i%20 == 0) fputs("\n", fp);
+    fprintf(fp, "0x%02x,", irep->iseq[i]);
+  }
+  fputs("};\n", fp);
+  /* dump lv */
+  if (irep->lv) {
+    len=irep->nlocals;
+    fprintf(fp,   "static const mrb_sym %s_lv_%d[%d] = {", name, n, len);
+    for (i=0; i+1<len; i++) {
+      fprintf(fp, "%uU, ", irep->lv[i]);
+    }
+    fputs("};\n", fp);
+  }
+  /* dump irep */
+  fprintf(fp, "static const mrb_irep %s_irep_%d = {\n", name, n);
+  fprintf(fp,   "  %d,%d,%d,\n", irep->nlocals, irep->nregs, irep->clen);
+  fprintf(fp,   "  MRB_IREP_STATIC,%s_iseq_%d,\n", name, n);
+  if (irep->pool) {
+    fprintf(fp, "  %s_pool_%d,", name, n);
+  }
+  else {
+    fputs(      "  NULL,", fp);
+  }
+  if (irep->syms) {
+    fprintf(fp, "%s_syms_%d,", name, n);
+  }
+  else {
+    fputs(      "NULL,", fp);
+  }
+  if (irep->reps) {
+    fprintf(fp, "%s_reps_%d,\n", name, n);
+  }
+  else {
+    fputs(      "NULL,\n", fp);
+  }
+  if (irep->lv) {
+    fprintf(fp, "  %s_lv_%d,\n", name, n);
+  }
+  else {
+    fputs(      "  NULL,\t\t\t\t\t/* lv */\n", fp);
+  }
+  fputs(        "  NULL,\t\t\t\t\t/* debug_info */\n", fp);
+  fprintf(fp,   "  %d,%d,%d,%d,0\n};\n", irep->ilen, irep->plen, irep->slen, irep->rlen);
+
+  return MRB_DUMP_OK;
+}
+
+int
+mrb_dump_irep_cstruct(mrb_state *mrb, const mrb_irep *irep, uint8_t flags, FILE *fp, const char *initname)
+{
+  int max = 1;
+  int n;
+
+  if (fp == NULL || initname == NULL || initname[0] == '\0') {
+    return MRB_DUMP_INVALID_ARGUMENT;
+  }
+  if (fprintf(fp, "#include <mruby.h>\n" "#include <mruby/proc.h>\n\n") < 0) {
+    return MRB_DUMP_WRITE_FAULT;
+  }
+  n = dump_irep_struct(mrb, irep, flags, fp, initname, 0, &max);
+  if (n != MRB_DUMP_OK) return n;
+  fprintf(fp, "#ifdef __cplusplus\nextern const struct RProc %s[];\n#endif\n", initname);
+  fprintf(fp, "const struct RProc %s[] = {{\n", initname);
+  fprintf(fp, "NULL,NULL,MRB_TT_PROC,7,0,{&%s_irep_0},NULL,{NULL},\n}};\n", initname);
+  return MRB_DUMP_OK;
+}
+
 #endif /* MRB_DISABLE_STDIO */
diff --git a/src/enum.c b/src/enum.c
index d31370188..b95956715 100644
--- a/src/enum.c
+++ b/src/enum.c
@@ -18,7 +18,7 @@ enum_update_hash(mrb_state *mrb, mrb_value self)
   mrb_get_args(mrb, "iii", &hash, &index, &hv);
   hash ^= ((uint32_t)hv << (index % 16));
 
-  return mrb_fixnum_value(hash);
+  return mrb_int_value(mrb, hash);
 }
 
 void
diff --git a/src/error.c b/src/error.c
index 5d17209e5..b19f0ea43 100644
--- a/src/error.c
+++ b/src/error.c
@@ -45,7 +45,7 @@ exc_initialize(mrb_state *mrb, mrb_value exc)
   mrb_value mesg;
 
   if (mrb_get_args(mrb, "|o", &mesg) == 1) {
-    mrb_iv_set(mrb, exc, mrb_intern_lit(mrb, "mesg"), mesg);
+    mrb_iv_set(mrb, exc, MRB_SYM(mesg), mesg);
   }
   return exc;
 }
@@ -74,7 +74,7 @@ exc_exception(mrb_state *mrb, mrb_value self)
   if (argc == 0) return self;
   if (mrb_obj_equal(mrb, self, a)) return self;
   exc = mrb_obj_clone(mrb, self);
-  mrb_iv_set(mrb, exc, mrb_intern_lit(mrb, "mesg"), a);
+  mrb_iv_set(mrb, exc, MRB_SYM(mesg), a);
 
   return exc;
 }
@@ -90,7 +90,7 @@ exc_exception(mrb_state *mrb, mrb_value self)
 mrb_value
 exc_to_s(mrb_state *mrb, mrb_value exc)
 {
-  mrb_value mesg = mrb_attr_get(mrb, exc, mrb_intern_lit(mrb, "mesg"));
+  mrb_value mesg = mrb_attr_get(mrb, exc, MRB_SYM(mesg));
   struct RObject *p;
 
   if (!mrb_string_p(mesg)) {
@@ -114,7 +114,7 @@ exc_to_s(mrb_state *mrb, mrb_value exc)
 static mrb_value
 exc_message(mrb_state *mrb, mrb_value exc)
 {
-  return mrb_funcall(mrb, exc, "to_s", 0);
+  return mrb_funcall_id(mrb, exc, MRB_SYM(to_s), 0);
 }
 
 /*
@@ -130,7 +130,7 @@ exc_message(mrb_state *mrb, mrb_value exc)
 mrb_value
 mrb_exc_inspect(mrb_state *mrb, mrb_value exc)
 {
-  mrb_value mesg = mrb_attr_get(mrb, exc, mrb_intern_lit(mrb, "mesg"));
+  mrb_value mesg = mrb_attr_get(mrb, exc, MRB_SYM(mesg));
   mrb_value cname = mrb_mod_to_s(mrb, mrb_obj_value(mrb_obj_class(mrb, exc)));
   mesg = mrb_obj_as_string(mrb, mesg);
   return RSTRING_LEN(mesg) == 0 ? cname : mrb_format(mrb, "%v (%v)", mesg, cname);
@@ -154,7 +154,7 @@ set_backtrace(mrb_state *mrb, mrb_value exc, mrb_value backtrace)
       p++;
     }
   }
-  mrb_iv_set(mrb, exc, mrb_intern_lit(mrb, "backtrace"), backtrace);
+  mrb_iv_set(mrb, exc, MRB_SYM(backtrace), backtrace);
 }
 
 static mrb_value
@@ -288,7 +288,7 @@ mrb_vformat(mrb_state *mrb, const char *format, va_list ap)
 #endif
           obj = mrb_fixnum_value(i);
           goto L_cat_obj;
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
         case 'f':
           obj = mrb_float_value(mrb, (mrb_float)va_arg(ap, double));
           goto L_cat_obj;
@@ -474,7 +474,7 @@ mrb_make_exception(mrb_state *mrb, mrb_int argc, const mrb_value *argv)
       n = 1;
 exception_call:
       {
-        mrb_sym exc = mrb_intern_lit(mrb, "exception");
+        mrb_sym exc = MRB_SYM(exception);
         if (mrb_respond_to(mrb, argv[0], exc)) {
           mesg = mrb_funcall_argv(mrb, argv[0], exc, n, argv+1);
         }
@@ -622,11 +622,11 @@ mrb_init_exception(mrb_state *mrb)
   script_error = mrb_define_class(mrb, "ScriptError", mrb->eException_class);                /* 15.2.37 */
   mrb_define_class(mrb, "SyntaxError", script_error);                                        /* 15.2.38 */
   stack_error = mrb_define_class(mrb, "SystemStackError", exception);
-  mrb->stack_err = mrb_obj_ptr(mrb_exc_new_str_lit(mrb, stack_error, "stack level too deep"));
+  mrb->stack_err = mrb_obj_ptr(mrb_exc_new_lit(mrb, stack_error, "stack level too deep"));
 
   nomem_error = mrb_define_class(mrb, "NoMemoryError", exception);
-  mrb->nomem_err = mrb_obj_ptr(mrb_exc_new_str_lit(mrb, nomem_error, "Out of memory"));
+  mrb->nomem_err = mrb_obj_ptr(mrb_exc_new_lit(mrb, nomem_error, "Out of memory"));
 #ifdef MRB_GC_FIXED_ARENA
-  mrb->arena_err = mrb_obj_ptr(mrb_exc_new_str_lit(mrb, nomem_error, "arena overflow error"));
+  mrb->arena_err = mrb_obj_ptr(mrb_exc_new_lit(mrb, nomem_error, "arena overflow error"));
 #endif
 }
diff --git a/src/etc.c b/src/etc.c
index 74b9ab03b..96f95ad5f 100644
--- a/src/etc.c
+++ b/src/etc.c
@@ -8,6 +8,7 @@
 #include <mruby/string.h>
 #include <mruby/data.h>
 #include <mruby/class.h>
+#include <mruby/numeric.h>
 
 MRB_API struct RData*
 mrb_data_object_alloc(mrb_state *mrb, struct RClass *klass, void *ptr, const mrb_data_type *type)
@@ -69,21 +70,11 @@ mrb_obj_to_sym(mrb_state *mrb, mrb_value name)
   return 0;  /* not reached */
 }
 
-MRB_API mrb_int
-#ifdef MRB_WITHOUT_FLOAT
-mrb_fixnum_id(mrb_int f)
-#else
-mrb_float_id(mrb_float f)
-#endif
+static mrb_int
+make_num_id(const char *p, size_t len)
 {
-  const char *p = (const char*)&f;
-  int len = sizeof(f);
   uint32_t id = 0;
 
-#ifndef MRB_WITHOUT_FLOAT
-  /* normalize -0.0 to 0.0 */
-  if (f == 0) f = 0.0;
-#endif
   while (len--) {
     id = id*65599 + *p;
     p++;
@@ -94,6 +85,22 @@ mrb_float_id(mrb_float f)
 }
 
 MRB_API mrb_int
+mrb_int_id(mrb_int n)
+{
+  return make_num_id((const char*)&n, sizeof(n));
+}
+
+#ifndef MRB_NO_FLOAT
+MRB_API mrb_int
+mrb_float_id(mrb_float f)
+{
+  /* normalize -0.0 to 0.0 */
+  if (f == 0) f = 0.0;
+  return make_num_id((const char*)&f, sizeof(f));
+}
+#endif
+
+MRB_API mrb_int
 mrb_obj_id(mrb_value obj)
 {
   mrb_int tt = mrb_type(obj);
@@ -114,11 +121,9 @@ mrb_obj_id(mrb_value obj)
     return MakeID(2);
   case MRB_TT_SYMBOL:
     return MakeID(mrb_symbol(obj));
-  case MRB_TT_FIXNUM:
-#ifdef MRB_WITHOUT_FLOAT
-    return MakeID(mrb_fixnum_id(mrb_fixnum(obj)));
-#else
-    return MakeID2(mrb_float_id((mrb_float)mrb_fixnum(obj)), MRB_TT_FLOAT);
+  case MRB_TT_INTEGER:
+    return MakeID(mrb_int_id(mrb_integer(obj)));
+#ifdef MRB_NO_FLOAT
   case MRB_TT_FLOAT:
     return MakeID(mrb_float_id(mrb_float(obj)));
 #endif
@@ -147,29 +152,32 @@ mrb_obj_id(mrb_value obj)
 #ifdef MRB_WORD_BOXING
 #define mrb_xxx_boxing_cptr_value mrb_word_boxing_cptr_value
 
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
 MRB_API mrb_value
 mrb_word_boxing_float_value(mrb_state *mrb, mrb_float f)
 {
-  mrb_value v;
+  union mrb_value_ v;
 
-  v.value.p = mrb_obj_alloc(mrb, MRB_TT_FLOAT, mrb->float_class);
-  v.value.fp->f = f;
-  MRB_SET_FROZEN_FLAG(v.value.bp);
-  return v;
+  v.p = mrb_obj_alloc(mrb, MRB_TT_FLOAT, mrb->float_class);
+  v.fp->f = f;
+  MRB_SET_FROZEN_FLAG(v.bp);
+  return v.w;
 }
+#endif  /* MRB_NO_FLOAT */
 
 MRB_API mrb_value
-mrb_word_boxing_float_pool(mrb_state *mrb, mrb_float f)
+mrb_word_boxing_int_value(mrb_state *mrb, mrb_int n)
 {
-  struct RFloat *nf = (struct RFloat *)mrb_malloc(mrb, sizeof(struct RFloat));
-  nf->tt = MRB_TT_FLOAT;
-  nf->c = mrb->float_class;
-  nf->f = f;
-  MRB_SET_FROZEN_FLAG(nf);
-  return mrb_obj_value(nf);
+  if (FIXABLE(n)) return mrb_fixnum_value(n);
+  else {
+    union mrb_value_ v;
+
+    v.p = mrb_obj_alloc(mrb, MRB_TT_INTEGER, mrb->integer_class);
+    v.ip->i = n;
+    MRB_SET_FROZEN_FLAG(v.ip);
+    return v.w;
+  }
 }
-#endif  /* MRB_WITHOUT_FLOAT */
 #endif  /* MRB_WORD_BOXING */
 
 #if defined(MRB_WORD_BOXING) || (defined(MRB_NAN_BOXING) && defined(MRB_64BIT))
diff --git a/src/fmt_fp.c b/src/fmt_fp.c
index 81ace6ec8..2c1e13c36 100644
--- a/src/fmt_fp.c
+++ b/src/fmt_fp.c
@@ -1,4 +1,4 @@
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
 #if defined(MRB_DISABLE_STDIO) || defined(_WIN32) || defined(_WIN64)
 /*
 
diff --git a/src/gc.c b/src/gc.c
index 5531207db..0f2c3bfab 100644
--- a/src/gc.c
+++ b/src/gc.c
@@ -6,6 +6,9 @@
 
 #include <string.h>
 #include <stdlib.h>
+#ifdef MRB_USE_MALLOC_TRIM
+#include <malloc.h>
+#endif
 #include <mruby.h>
 #include <mruby/array.h>
 #include <mruby/class.h>
@@ -35,6 +38,11 @@
     * Gray - Marked, But the child objects are unmarked.
     * Black - Marked, the child objects are also marked.
 
+  Extra color
+
+    * Red - Static (ROM object) no need to be collected.
+          - All child objects should be Red as well.
+
   == Two White Types
 
   There're two white color types in a flip-flop fashion: White-A and White-B,
@@ -117,7 +125,7 @@ typedef struct {
     struct RException exc;
     struct RBreak brk;
 #ifdef MRB_WORD_BOXING
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
     struct RFloat floatv;
 #endif
     struct RCptr cptr;
@@ -185,6 +193,7 @@ gettimeofday_time(void)
 #define GC_WHITE_A 1
 #define GC_WHITE_B (1 << 1)
 #define GC_BLACK (1 << 2)
+#define GC_RED 7
 #define GC_WHITES (GC_WHITE_A | GC_WHITE_B)
 #define GC_COLOR_MASK 7
 
@@ -194,7 +203,8 @@ gettimeofday_time(void)
 #define paint_partial_white(s, o) ((o)->color = (s)->current_white_part)
 #define is_gray(o) ((o)->color == GC_GRAY)
 #define is_white(o) ((o)->color & GC_WHITES)
-#define is_black(o) ((o)->color & GC_BLACK)
+#define is_black(o) ((o)->color == GC_BLACK)
+#define is_red(o) ((o)->color == GC_RED)
 #define flip_white_part(s) ((s)->current_white_part = other_white_part(s))
 #define other_white_part(s) ((s)->current_white_part ^ GC_WHITES)
 #define is_dead(s, o) (((o)->color & other_white_part(s) & GC_WHITES) || (o)->tt == MRB_TT_FREE)
@@ -581,11 +591,11 @@ add_gray_list(mrb_state *mrb, mrb_gc *gc, struct RBasic *obj)
   gc->gray_list = obj;
 }
 
-static int
+static mrb_int
 ci_nregs(mrb_callinfo *ci)
 {
-  struct RProc *p = ci->proc;
-  int n = 0;
+  const struct RProc *p = ci->proc;
+  mrb_int n = 0;
 
   if (!p) {
     if (ci->argc < 0) return 3;
@@ -633,7 +643,6 @@ mark_context_stack(mrb_state *mrb, struct mrb_context *c)
 static void
 mark_context(mrb_state *mrb, struct mrb_context *c)
 {
-  int i;
   mrb_callinfo *ci;
 
  start:
@@ -650,10 +659,6 @@ mark_context(mrb_state *mrb, struct mrb_context *c)
       mrb_gc_mark(mrb, (struct RBasic*)ci->target_class);
     }
   }
-  /* mark ensure stack */
-  for (i=0; i<c->eidx; i++) {
-    mrb_gc_mark(mrb, (struct RBasic*)c->ensure[i]);
-  }
   /* mark fibers */
   mrb_gc_mark(mrb, (struct RBasic*)c->fib);
   if (c->prev) {
@@ -765,6 +770,7 @@ mrb_gc_mark(mrb_state *mrb, struct RBasic *obj)
 {
   if (obj == 0) return;
   if (!is_white(obj)) return;
+  if (is_red(obj)) return;
   mrb_assert((obj)->tt != MRB_TT_FREE);
   add_gray_list(mrb, &mrb->gc, obj);
 }
@@ -776,12 +782,12 @@ obj_free(mrb_state *mrb, struct RBasic *obj, int end)
   switch (obj->tt) {
     /* immediate - no mark */
   case MRB_TT_TRUE:
-  case MRB_TT_FIXNUM:
+  case MRB_TT_INTEGER:
   case MRB_TT_SYMBOL:
     /* cannot happen */
     return;
 
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
   case MRB_TT_FLOAT:
 #ifdef MRB_WORD_BOXING
     break;
@@ -803,12 +809,14 @@ obj_free(mrb_state *mrb, struct RBasic *obj, int end)
   case MRB_TT_SCLASS:
     mrb_gc_free_mt(mrb, (struct RClass*)obj);
     mrb_gc_free_iv(mrb, (struct RObject*)obj);
-    mrb_mc_clear_by_class(mrb, (struct RClass*)obj);
+    if (!end)
+      mrb_mc_clear_by_class(mrb, (struct RClass*)obj);
     break;
   case MRB_TT_ICLASS:
     if (MRB_FLAG_TEST(obj, MRB_FL_CLASS_IS_ORIGIN))
       mrb_gc_free_mt(mrb, (struct RClass*)obj);
-    mrb_mc_clear_by_class(mrb, (struct RClass*)obj);
+    if (!end)
+      mrb_mc_clear_by_class(mrb, (struct RClass*)obj);
     break;
   case MRB_TT_ENV:
     {
@@ -868,7 +876,7 @@ obj_free(mrb_state *mrb, struct RBasic *obj, int end)
       struct RProc *p = (struct RProc*)obj;
 
       if (!MRB_PROC_CFUNC_P(p) && p->body.irep) {
-        mrb_irep *irep = p->body.irep;
+        mrb_irep *irep = (mrb_irep*)p->body.irep;
         if (end) {
           mrb_irep_cutref(mrb, irep);
         }
@@ -924,10 +932,10 @@ root_scan_phase(mrb_state *mrb, mrb_gc *gc)
   mrb_gc_mark(mrb, (struct RBasic*)mrb->hash_class);
   mrb_gc_mark(mrb, (struct RBasic*)mrb->range_class);
 
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
   mrb_gc_mark(mrb, (struct RBasic*)mrb->float_class);
 #endif
-  mrb_gc_mark(mrb, (struct RBasic*)mrb->fixnum_class);
+  mrb_gc_mark(mrb, (struct RBasic*)mrb->integer_class);
   mrb_gc_mark(mrb, (struct RBasic*)mrb->true_class);
   mrb_gc_mark(mrb, (struct RBasic*)mrb->false_class);
   mrb_gc_mark(mrb, (struct RBasic*)mrb->nil_class);
@@ -1004,9 +1012,6 @@ gc_gray_counts(mrb_state *mrb, mrb_gc *gc, struct RBasic *obj)
       if (c->stbase + i > c->stend) i = c->stend - c->stbase;
       children += i;
 
-      /* mark ensure stack */
-      children += c->eidx;
-
       /* mark closure */
       if (c->cibase) {
         for (i=0, ci = c->cibase; ci <= c->ci; i++, ci++)
@@ -1317,6 +1322,9 @@ mrb_full_gc(mrb_state *mrb)
     gc->full = FALSE;
   }
 
+#ifdef MRB_USE_MALLOC_TRIM
+  malloc_trim(0);
+#endif
   GC_TIME_STOP_AND_REPORT;
 }
 
diff --git a/src/hash.c b/src/hash.c
index c891e1b22..d67fa6254 100644
--- a/src/hash.c
+++ b/src/hash.c
@@ -11,7 +11,7 @@
 #include <mruby/string.h>
 #include <mruby/variable.h>
 
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
 /* a function to get hash value of a float number */
 mrb_int mrb_float_id(mrb_float f);
 #endif
@@ -64,16 +64,16 @@ ht_hash_func(mrb_state *mrb, htable *t, mrb_value key)
   case MRB_TT_TRUE:
   case MRB_TT_FALSE:
   case MRB_TT_SYMBOL:
-  case MRB_TT_FIXNUM:
-#ifndef MRB_WITHOUT_FLOAT
+  case MRB_TT_INTEGER:
+#ifndef MRB_NO_FLOAT
   case MRB_TT_FLOAT:
 #endif
     h = (size_t)mrb_obj_id(key);
     break;
 
   default:
-    hv = mrb_funcall(mrb, key, "hash", 0);
-    h = (size_t)tt ^ (size_t)mrb_fixnum(hv);
+    hv = mrb_funcall_id(mrb, key, MRB_SYM(hash), 0);
+    h = (size_t)tt ^ (size_t)mrb_integer(hv);
     break;
   }
   if (index && (index != t->index || capa != index->capa)) {
@@ -95,28 +95,14 @@ ht_hash_equal(mrb_state *mrb, htable *t, mrb_value a, mrb_value b)
     if (!mrb_symbol_p(b)) return FALSE;
     return mrb_symbol(a) == mrb_symbol(b);
 
-  case MRB_TT_FIXNUM:
-    switch (mrb_type(b)) {
-    case MRB_TT_FIXNUM:
-      return mrb_fixnum(a) == mrb_fixnum(b);
-#ifndef MRB_WITHOUT_FLOAT
-    case MRB_TT_FLOAT:
-      return (mrb_float)mrb_fixnum(a) == mrb_float(b);
-#endif
-    default:
-      return FALSE;
-    }
+  case MRB_TT_INTEGER:
+    if (!mrb_integer_p(b)) return FALSE;
+    return mrb_integer(a) == mrb_integer(b);
 
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
   case MRB_TT_FLOAT:
-    switch (mrb_type(b)) {
-    case MRB_TT_FIXNUM:
-      return mrb_float(a) == (mrb_float)mrb_fixnum(b);
-    case MRB_TT_FLOAT:
-      return mrb_float(a) == mrb_float(b);
-    default:
-      return FALSE;
-    }
+    if (!mrb_float_p(b)) return FALSE;
+    return mrb_float(a) == mrb_float(b);
 #endif
 
   default:
@@ -589,7 +575,7 @@ ht_free(mrb_state *mrb, htable *t)
   mrb_free(mrb, t);
 }
 
-static void mrb_hash_modify(mrb_state *mrb, mrb_value hash);
+static void hash_modify(mrb_state *mrb, mrb_value hash);
 
 static inline mrb_value
 ht_key(mrb_state *mrb, mrb_value key)
@@ -683,7 +669,7 @@ mrb_hash_init_copy(mrb_state *mrb, mrb_value self)
   vret = mrb_obj_value(copy);
   ifnone = RHASH_IFNONE(self);
   if (!mrb_nil_p(ifnone)) {
-      mrb_iv_set(mrb, vret, mrb_intern_lit(mrb, "ifnone"), ifnone);
+    mrb_iv_set(mrb, vret, MRB_SYM(ifnone), ifnone);
   }
   return vret;
 }
@@ -729,7 +715,7 @@ mrb_hash_get(mrb_state *mrb, mrb_value hash, mrb_value key)
     return val;
   }
 
-  mid = mrb_intern_lit(mrb, "default");
+  mid = MRB_SYM(default);
   if (mrb_func_basic_p(mrb, hash, mid, mrb_hash_default)) {
     return hash_default(mrb, hash, key);
   }
@@ -752,7 +738,7 @@ mrb_hash_fetch(mrb_state *mrb, mrb_value hash, mrb_value key, mrb_value def)
 MRB_API void
 mrb_hash_set(mrb_state *mrb, mrb_value hash, mrb_value key, mrb_value val)
 {
-  mrb_hash_modify(mrb, hash);
+  hash_modify(mrb, hash);
 
   key = KEY(key);
   ht_put(mrb, RHASH_TBL(hash), key, val);
@@ -762,7 +748,7 @@ mrb_hash_set(mrb_state *mrb, mrb_value hash, mrb_value key, mrb_value val)
 }
 
 static void
-mrb_hash_modify(mrb_state *mrb, mrb_value hash)
+hash_modify(mrb_state *mrb, mrb_value hash)
 {
   mrb_check_frozen(mrb, mrb_hash_ptr(hash));
   if (!RHASH_TBL(hash)) {
@@ -814,7 +800,7 @@ mrb_hash_init(mrb_state *mrb, mrb_value hash)
 
   ifnone = mrb_nil_value();
   mrb_get_args(mrb, "&|o?", &block, &ifnone, &ifnone_p);
-  mrb_hash_modify(mrb, hash);
+  hash_modify(mrb, hash);
   if (!mrb_nil_p(block)) {
     if (ifnone_p) {
       mrb_argnum_error(mrb, 1, 0, 0);
@@ -824,7 +810,7 @@ mrb_hash_init(mrb_state *mrb, mrb_value hash)
   }
   if (!mrb_nil_p(ifnone)) {
     RHASH(hash)->flags |= MRB_HASH_DEFAULT;
-    mrb_iv_set(mrb, hash, mrb_intern_lit(mrb, "ifnone"), ifnone);
+    mrb_iv_set(mrb, hash, MRB_SYM(ifnone), ifnone);
   }
   return hash;
 }
@@ -856,7 +842,7 @@ hash_default(mrb_state *mrb, mrb_value hash, mrb_value key)
 {
   if (MRB_RHASH_DEFAULT_P(hash)) {
     if (MRB_RHASH_PROCDEFAULT_P(hash)) {
-      return mrb_funcall(mrb, RHASH_PROCDEFAULT(hash), "call", 2, hash, key);
+      return mrb_funcall_id(mrb, RHASH_PROCDEFAULT(hash), MRB_SYM(call), 2, hash, key);
     }
     else {
       return RHASH_IFNONE(hash);
@@ -897,7 +883,7 @@ mrb_hash_default(mrb_state *mrb, mrb_value hash)
   if (MRB_RHASH_DEFAULT_P(hash)) {
     if (MRB_RHASH_PROCDEFAULT_P(hash)) {
       if (!given) return mrb_nil_value();
-      return mrb_funcall(mrb, RHASH_PROCDEFAULT(hash), "call", 2, hash, key);
+      return mrb_funcall_id(mrb, RHASH_PROCDEFAULT(hash), MRB_SYM(call), 2, hash, key);
     }
     else {
       return RHASH_IFNONE(hash);
@@ -932,8 +918,8 @@ mrb_hash_set_default(mrb_state *mrb, mrb_value hash)
 {
   mrb_value ifnone = mrb_get_arg1(mrb);
 
-  mrb_hash_modify(mrb, hash);
-  mrb_iv_set(mrb, hash, mrb_intern_lit(mrb, "ifnone"), ifnone);
+  hash_modify(mrb, hash);
+  mrb_iv_set(mrb, hash, MRB_SYM(ifnone), ifnone);
   RHASH(hash)->flags &= ~MRB_HASH_PROC_DEFAULT;
   if (!mrb_nil_p(ifnone)) {
     RHASH(hash)->flags |= MRB_HASH_DEFAULT;
@@ -987,8 +973,8 @@ mrb_hash_set_default_proc(mrb_state *mrb, mrb_value hash)
 {
   mrb_value ifnone = mrb_get_arg1(mrb);
 
-  mrb_hash_modify(mrb, hash);
-  mrb_iv_set(mrb, hash, mrb_intern_lit(mrb, "ifnone"), ifnone);
+  hash_modify(mrb, hash);
+  mrb_iv_set(mrb, hash, MRB_SYM(ifnone), ifnone);
   if (!mrb_nil_p(ifnone)) {
     RHASH(hash)->flags |= MRB_HASH_PROC_DEFAULT;
     RHASH(hash)->flags |= MRB_HASH_DEFAULT;
@@ -1020,7 +1006,7 @@ mrb_hash_delete(mrb_state *mrb, mrb_value self)
 {
   mrb_value key = mrb_get_arg1(mrb);
 
-  mrb_hash_modify(mrb, self);
+  hash_modify(mrb, self);
   return mrb_hash_delete_key(mrb, self, key);
 }
 
@@ -1070,7 +1056,7 @@ mrb_hash_shift(mrb_state *mrb, mrb_value hash)
 {
   htable *t = RHASH_TBL(hash);
 
-  mrb_hash_modify(mrb, hash);
+  hash_modify(mrb, hash);
   if (t && t->size > 0) {
     mrb_value del_key = mrb_nil_value();
     mrb_value del_val = mrb_nil_value();
@@ -1083,7 +1069,7 @@ mrb_hash_shift(mrb_state *mrb, mrb_value hash)
 
   if (MRB_RHASH_DEFAULT_P(hash)) {
     if (MRB_RHASH_PROCDEFAULT_P(hash)) {
-      return mrb_funcall(mrb, RHASH_PROCDEFAULT(hash), "call", 2, hash, mrb_nil_value());
+      return mrb_funcall_id(mrb, RHASH_PROCDEFAULT(hash), MRB_SYM(call), 2, hash, mrb_nil_value());
     }
     else {
       return RHASH_IFNONE(hash);
@@ -1109,7 +1095,7 @@ mrb_hash_clear(mrb_state *mrb, mrb_value hash)
 {
   htable *t = RHASH_TBL(hash);
 
-  mrb_hash_modify(mrb, hash);
+  hash_modify(mrb, hash);
   if (t) {
     ht_free(mrb, t);
     RHASH_TBL(hash) = NULL;
@@ -1368,7 +1354,7 @@ mrb_hash_merge(mrb_state *mrb, mrb_value hash1, mrb_value hash2)
 {
   htable *h1, *h2;
 
-  mrb_hash_modify(mrb, hash1);
+  hash_modify(mrb, hash1);
   hash2 = mrb_ensure_hash_type(mrb, hash2);
   h1 = RHASH_TBL(hash1);
   h2 = RHASH_TBL(hash2);
diff --git a/src/kernel.c b/src/kernel.c
index 10ed9f88e..c34d0bb6e 100644
--- a/src/kernel.c
+++ b/src/kernel.c
@@ -19,7 +19,7 @@ mrb_func_basic_p(mrb_state *mrb, mrb_value obj, mrb_sym mid, mrb_func_t func)
 {
   struct RClass *c = mrb_class(mrb, obj);
   mrb_method_t m = mrb_method_search_vm(mrb, &c, mid);
-  struct RProc *p;
+  const struct RProc *p;
 
   if (MRB_METHOD_UNDEF_P(m)) return FALSE;
   if (MRB_METHOD_FUNC_P(m))
@@ -33,7 +33,7 @@ mrb_func_basic_p(mrb_state *mrb, mrb_value obj, mrb_sym mid, mrb_func_t func)
 static mrb_bool
 mrb_obj_basic_to_s_p(mrb_state *mrb, mrb_value obj)
 {
-  return mrb_func_basic_p(mrb, obj, mrb_intern_lit(mrb, "to_s"), mrb_any_to_s);
+  return mrb_func_basic_p(mrb, obj, MRB_SYM(to_s), mrb_any_to_s);
 }
 
 /* 15.3.1.3.17 */
@@ -96,7 +96,7 @@ mrb_equal_m(mrb_state *mrb, mrb_value self)
 mrb_value
 mrb_obj_id_m(mrb_state *mrb, mrb_value self)
 {
-  return mrb_fixnum_value(mrb_obj_id(self));
+  return mrb_int_value(mrb, mrb_obj_id(self));
 }
 
 static int
@@ -143,7 +143,7 @@ mrb_f_block_given_p_m(mrb_state *mrb, mrb_value self)
   mrb_value *bp;
   int bidx;
   struct REnv *e = NULL;
-  struct RProc *p;
+  const struct RProc *p;
 
   if (ci <= cibase) {
     /* toplevel does not have block */
@@ -209,7 +209,7 @@ mrb_f_block_given_p_m(mrb_state *mrb, mrb_value self)
  *  called with an explicit receiver, as <code>class</code> is also a
  *  reserved word in Ruby.
  *
- *     1.class      #=> Fixnum
+ *     1.class      #=> Integer
  *     self.class   #=> Object
  */
 static mrb_value
@@ -218,187 +218,6 @@ mrb_obj_class_m(mrb_state *mrb, mrb_value self)
   return mrb_obj_value(mrb_obj_class(mrb, self));
 }
 
-static struct RClass*
-mrb_singleton_class_clone(mrb_state *mrb, mrb_value obj)
-{
-  struct RClass *klass = mrb_basic_ptr(obj)->c;
-
-  if (klass->tt != MRB_TT_SCLASS)
-    return klass;
-  else {
-    /* copy singleton(unnamed) class */
-    struct RClass *clone = (struct RClass*)mrb_obj_alloc(mrb, klass->tt, mrb->class_class);
-
-    switch (mrb_type(obj)) {
-    case MRB_TT_CLASS:
-    case MRB_TT_SCLASS:
-      break;
-    default:
-      clone->c = mrb_singleton_class_clone(mrb, mrb_obj_value(klass));
-      break;
-    }
-    clone->super = klass->super;
-    if (klass->iv) {
-      mrb_iv_copy(mrb, mrb_obj_value(clone), mrb_obj_value(klass));
-      mrb_obj_iv_set(mrb, (struct RObject*)clone, mrb_intern_lit(mrb, "__attached__"), obj);
-    }
-    if (klass->mt) {
-      clone->mt = kh_copy(mt, mrb, klass->mt);
-    }
-    else {
-      clone->mt = kh_init(mt, mrb);
-    }
-    clone->tt = MRB_TT_SCLASS;
-    return clone;
-  }
-}
-
-static void
-copy_class(mrb_state *mrb, mrb_value dst, mrb_value src)
-{
-  struct RClass *dc = mrb_class_ptr(dst);
-  struct RClass *sc = mrb_class_ptr(src);
-  /* if the origin is not the same as the class, then the origin and
-     the current class need to be copied */
-  if (sc->flags & MRB_FL_CLASS_IS_PREPENDED) {
-    struct RClass *c0 = sc->super;
-    struct RClass *c1 = dc;
-
-    /* copy prepended iclasses */
-    while (!(c0->flags & MRB_FL_CLASS_IS_ORIGIN)) {
-      c1->super = mrb_class_ptr(mrb_obj_dup(mrb, mrb_obj_value(c0)));
-      c1 = c1->super;
-      c0 = c0->super;
-    }
-    c1->super = mrb_class_ptr(mrb_obj_dup(mrb, mrb_obj_value(c0)));
-    c1->super->flags |= MRB_FL_CLASS_IS_ORIGIN;
-  }
-  if (sc->mt) {
-    dc->mt = kh_copy(mt, mrb, sc->mt);
-  }
-  else {
-    dc->mt = kh_init(mt, mrb);
-  }
-  dc->super = sc->super;
-  MRB_SET_INSTANCE_TT(dc, MRB_INSTANCE_TT(sc));
-}
-
-static void
-init_copy(mrb_state *mrb, mrb_value dest, mrb_value obj)
-{
-  switch (mrb_type(obj)) {
-    case MRB_TT_ICLASS:
-      copy_class(mrb, dest, obj);
-      return;
-    case MRB_TT_CLASS:
-    case MRB_TT_MODULE:
-      copy_class(mrb, dest, obj);
-      mrb_iv_copy(mrb, dest, obj);
-      mrb_iv_remove(mrb, dest, mrb_intern_lit(mrb, "__classname__"));
-      break;
-    case MRB_TT_OBJECT:
-    case MRB_TT_SCLASS:
-    case MRB_TT_HASH:
-    case MRB_TT_DATA:
-    case MRB_TT_EXCEPTION:
-      mrb_iv_copy(mrb, dest, obj);
-      break;
-    case MRB_TT_ISTRUCT:
-      mrb_istruct_copy(dest, obj);
-      break;
-
-    default:
-      break;
-  }
-  mrb_funcall(mrb, dest, "initialize_copy", 1, obj);
-}
-
-/* 15.3.1.3.8  */
-/*
- *  call-seq:
- *     obj.clone -> an_object
- *
- *  Produces a shallow copy of <i>obj</i>---the instance variables of
- *  <i>obj</i> are copied, but not the objects they reference. Copies
- *  the frozen state of <i>obj</i>. See also the discussion
- *  under <code>Object#dup</code>.
- *
- *     class Klass
- *        attr_accessor :str
- *     end
- *     s1 = Klass.new      #=> #<Klass:0x401b3a38>
- *     s1.str = "Hello"    #=> "Hello"
- *     s2 = s1.clone       #=> #<Klass:0x401b3998 @str="Hello">
- *     s2.str[1,4] = "i"   #=> "i"
- *     s1.inspect          #=> "#<Klass:0x401b3a38 @str=\"Hi\">"
- *     s2.inspect          #=> "#<Klass:0x401b3998 @str=\"Hi\">"
- *
- *  This method may have class-specific behavior.  If so, that
- *  behavior will be documented under the #+initialize_copy+ method of
- *  the class.
- *
- *  Some Class(True False Nil Symbol Fixnum Float) Object  cannot clone.
- */
-MRB_API mrb_value
-mrb_obj_clone(mrb_state *mrb, mrb_value self)
-{
-  struct RObject *p;
-  mrb_value clone;
-
-  if (mrb_immediate_p(self)) {
-    return self;
-  }
-  if (mrb_sclass_p(self)) {
-    mrb_raise(mrb, E_TYPE_ERROR, "can't clone singleton class");
-  }
-  p = (struct RObject*)mrb_obj_alloc(mrb, mrb_type(self), mrb_obj_class(mrb, self));
-  p->c = mrb_singleton_class_clone(mrb, self);
-  mrb_field_write_barrier(mrb, (struct RBasic*)p, (struct RBasic*)p->c);
-  clone = mrb_obj_value(p);
-  init_copy(mrb, clone, self);
-  p->flags |= mrb_obj_ptr(self)->flags & MRB_FL_OBJ_IS_FROZEN;
-
-  return clone;
-}
-
-/* 15.3.1.3.9  */
-/*
- *  call-seq:
- *     obj.dup -> an_object
- *
- *  Produces a shallow copy of <i>obj</i>---the instance variables of
- *  <i>obj</i> are copied, but not the objects they reference.
- *  <code>dup</code> copies the frozen state of <i>obj</i>. See also
- *  the discussion under <code>Object#clone</code>. In general,
- *  <code>clone</code> and <code>dup</code> may have different semantics
- *  in descendant classes. While <code>clone</code> is used to duplicate
- *  an object, including its internal state, <code>dup</code> typically
- *  uses the class of the descendant object to create the new instance.
- *
- *  This method may have class-specific behavior.  If so, that
- *  behavior will be documented under the #+initialize_copy+ method of
- *  the class.
- */
-
-MRB_API mrb_value
-mrb_obj_dup(mrb_state *mrb, mrb_value obj)
-{
-  struct RBasic *p;
-  mrb_value dup;
-
-  if (mrb_immediate_p(obj)) {
-    return obj;
-  }
-  if (mrb_sclass_p(obj)) {
-    mrb_raise(mrb, E_TYPE_ERROR, "can't dup singleton class");
-  }
-  p = mrb_obj_alloc(mrb, mrb_type(obj), mrb_obj_class(mrb, obj));
-  dup = mrb_obj_value(p);
-  init_copy(mrb, dup, obj);
-
-  return dup;
-}
-
 static mrb_value
 mrb_obj_extend(mrb_state *mrb, mrb_int argc, mrb_value *argv, mrb_value obj)
 {
@@ -411,8 +230,8 @@ mrb_obj_extend(mrb_state *mrb, mrb_int argc, mrb_value *argv, mrb_value obj)
     mrb_check_type(mrb, argv[i], MRB_TT_MODULE);
   }
   while (argc--) {
-    mrb_funcall(mrb, argv[argc], "extend_object", 1, obj);
-    mrb_funcall(mrb, argv[argc], "extended", 1, obj);
+    mrb_funcall_id(mrb, argv[argc], MRB_SYM(extend_object), 1, obj);
+    mrb_funcall_id(mrb, argv[argc], MRB_SYM(extended), 1, obj);
   }
   return obj;
 }
@@ -476,20 +295,20 @@ mrb_obj_frozen(mrb_state *mrb, mrb_value self)
  *  call-seq:
  *     obj.hash    -> fixnum
  *
- *  Generates a <code>Fixnum</code> hash value for this object. This
+ *  Generates a <code>Integer</code> hash value for this object. This
  *  function must have the property that <code>a.eql?(b)</code> implies
  *  <code>a.hash == b.hash</code>. The hash value is used by class
  *  <code>Hash</code>. Any hash value that exceeds the capacity of a
- *  <code>Fixnum</code> will be truncated before being used.
+ *  <code>Integer</code> will be truncated before being used.
  */
 static mrb_value
 mrb_obj_hash(mrb_state *mrb, mrb_value self)
 {
-  return mrb_fixnum_value(mrb_obj_id(self));
+  return mrb_int_value(mrb, mrb_obj_id(self));
 }
 
 /* 15.3.1.3.16 */
-static mrb_value
+mrb_value
 mrb_obj_init_copy(mrb_state *mrb, mrb_value self)
 {
   mrb_value orig = mrb_get_arg1(mrb);
@@ -501,7 +320,6 @@ mrb_obj_init_copy(mrb_state *mrb, mrb_value self)
   return self;
 }
 
-
 MRB_API mrb_bool
 mrb_obj_is_instance_of(mrb_state *mrb, mrb_value obj, struct RClass* c)
 {
@@ -564,9 +382,6 @@ mrb_obj_is_kind_of_m(mrb_state *mrb, mrb_value self)
   return mrb_bool_value(mrb_obj_is_kind_of(mrb, self, c));
 }
 
-KHASH_DECLARE(st, mrb_sym, char, FALSE)
-KHASH_DEFINE(st, mrb_sym, char, FALSE, kh_int_hash_func, kh_int_hash_equal)
-
 /* 15.3.1.3.32 */
 /*
  * call_seq:
@@ -749,7 +564,7 @@ obj_respond_to(mrb_state *mrb, mrb_value self)
   mrb_get_args(mrb, "n|b", &id, &priv);
   respond_to_p = basic_obj_respond_to(mrb, self, id, !priv);
   if (!respond_to_p) {
-    rtm_id = mrb_intern_lit(mrb, "respond_to_missing?");
+    rtm_id = MRB_QSYM(respond_to_missing_p);
     if (basic_obj_respond_to(mrb, self, rtm_id, !priv)) {
       mrb_value args[2], v;
       args[0] = mrb_symbol_value(id);
@@ -766,7 +581,7 @@ mrb_obj_ceqq(mrb_state *mrb, mrb_value self)
 {
   mrb_value v = mrb_get_arg1(mrb);
   mrb_int i, len;
-  mrb_sym eqq = mrb_intern_lit(mrb, "===");
+  mrb_sym eqq = MRB_QSYM(eqq);
   mrb_value ary;
 
   if (mrb_array_p(self)) {
diff --git a/src/load.c b/src/load.c
index 247d511df..c1a8c4c87 100644
--- a/src/load.c
+++ b/src/load.c
@@ -15,6 +15,7 @@
 #include <mruby/debug.h>
 #include <mruby/error.h>
 #include <mruby/data.h>
+#include <mruby/endian.h>
 
 #if SIZE_MAX < UINT32_MAX
 # error size_t must be at least 32 bits wide
@@ -26,31 +27,32 @@
 #define SIZE_ERROR_MUL(nmemb, size) ((size_t)(nmemb) > SIZE_MAX / (size))
 
 static size_t
-skip_padding(const uint8_t *buf)
-{
-  const size_t align = MRB_DUMP_ALIGNMENT;
-  return -(intptr_t)buf & (align-1);
-}
-
-static size_t
 offset_crc_body(void)
 {
   struct rite_binary_header header;
   return ((uint8_t *)header.binary_crc - (uint8_t *)&header) + sizeof(header.binary_crc);
 }
 
-#ifndef MRB_WITHOUT_FLOAT
-double mrb_str_len_to_dbl(mrb_state *mrb, const char *s, size_t len, mrb_bool badcheck);
-
+#ifndef MRB_NO_FLOAT
 static double
-str_to_double(mrb_state *mrb, const char *p, size_t len)
+str_to_double(mrb_state *mrb, const char *p)
 {
-  /* `i`, `inf`, `infinity` */
-  if (len > 0 && p[0] == 'i') return INFINITY;
-
-  /* `I`, `-inf`, `-infinity` */
-  if (p[0] == 'I' || (len > 1 && p[0] == '-' && p[1] == 'i')) return -INFINITY;
-  return mrb_str_len_to_dbl(mrb, p, len, TRUE);
+  /* dump IEEE754 little endian binary */
+  union {
+    char s[sizeof(double)];
+    double f;
+  } u;
+
+  if (littleendian) {
+    memcpy(u.s, p, sizeof(double));
+  }
+  else {
+    size_t i;
+    for (i=0; i<sizeof(double); i++) {
+      u.s[i] = p[sizeof(double)-i-1];
+    }
+  }
+  return u.f;
 }
 #endif
 
@@ -73,8 +75,10 @@ read_irep_record_1(mrb_state *mrb, const uint8_t *bin, size_t *len, uint8_t flag
   uint16_t tt, pool_data_len, snl;
   int plen;
   struct RData *irep_obj = mrb_data_object_alloc(mrb, mrb->object_class, NULL, &tempirep_type);
-  mrb_irep *irep = mrb_add_irep(mrb);
+  mrb_pool_value *pool;
+  mrb_sym *syms;
   int ai = mrb_gc_arena_save(mrb);
+  mrb_irep *irep = mrb_add_irep(mrb);
 
   irep_obj->data = irep;
 
@@ -94,110 +98,137 @@ read_irep_record_1(mrb_state *mrb, const uint8_t *bin, size_t *len, uint8_t flag
   src += sizeof(uint16_t);
 
   /* Binary Data Section */
-  /* ISEQ BLOCK */
-  irep->ilen = (uint16_t)bin_to_uint32(src);
-  src += sizeof(uint32_t);
-  src += skip_padding(src);
+  /* ISEQ BLOCK (and CATCH HANDLER TABLE BLOCK) */
+  irep->clen = bin_to_uint16(src);  /* number of catch handler */
+  src += sizeof(uint16_t);
+  irep->ilen = bin_to_uint16(src);
+  src += sizeof(uint16_t);
 
   if (irep->ilen > 0) {
+    size_t data_len = sizeof(mrb_code) * irep->ilen +
+                      sizeof(struct mrb_irep_catch_handler) * irep->clen;
+    mrb_static_assert1(sizeof(struct mrb_irep_catch_handler) == 7);
     if (SIZE_ERROR_MUL(irep->ilen, sizeof(mrb_code))) {
       return NULL;
     }
     if ((flags & FLAG_SRC_MALLOC) == 0) {
       irep->iseq = (mrb_code*)src;
-      src += sizeof(mrb_code) * irep->ilen;
       irep->flags |= MRB_ISEQ_NO_FREE;
     }
     else {
-      size_t data_len = sizeof(mrb_code) * irep->ilen;
       void *buf = mrb_malloc(mrb, data_len);
       irep->iseq = (mrb_code *)buf;
       memcpy(buf, src, data_len);
-      src += data_len;
     }
+    src += data_len;
   }
 
   /* POOL BLOCK */
-  plen = bin_to_uint32(src); /* number of pool */
-  src += sizeof(uint32_t);
+  plen = bin_to_uint16(src); /* number of pool */
+  src += sizeof(uint16_t);
   if (plen > 0) {
     if (SIZE_ERROR_MUL(plen, sizeof(mrb_value))) {
       return NULL;
     }
-    irep->pool = (mrb_value*)mrb_malloc(mrb, sizeof(mrb_value) * plen);
+    irep->pool = pool = (mrb_pool_value*)mrb_calloc(mrb, sizeof(mrb_pool_value), plen);
 
     for (i = 0; i < plen; i++) {
-      const char *s;
       mrb_bool st = (flags & FLAG_SRC_MALLOC)==0;
 
       tt = *src++; /* pool TT */
-      pool_data_len = bin_to_uint16(src); /* pool data length */
-      src += sizeof(uint16_t);
-      s = (const char*)src;
-      src += pool_data_len;
       switch (tt) { /* pool data */
-      case IREP_TT_FIXNUM: {
-        mrb_value num = mrb_str_len_to_inum(mrb, s, pool_data_len, 10, FALSE);
-#ifdef MRB_WITHOUT_FLOAT
-        irep->pool[i] = num;
+      case IREP_TT_INT32:
+        {
+          mrb_int v = (int32_t)bin_to_uint32(src);
+          src += sizeof(uint32_t);
+#ifdef MRB_64BIT
+          pool[i].tt = IREP_TT_INT64;
+          pool[i].u.i64 = (int64_t)v;
 #else
-        irep->pool[i] = mrb_float_p(num)? mrb_float_pool(mrb, mrb_float(num)) : num;
+          pool[i].tt = IREP_TT_INT32;
+          pool[i].u.i32 = v;
 #endif
         }
         break;
+      case IREP_TT_INT64:
+#ifdef MRB_64BIT
+        {
+          uint64_t i = bin_to_uint32(src);
+          src += sizeof(uint32_t);
+          i <<= 32;
+          i |= bin_to_uint32(src);
+          src += sizeof(uint32_t);
+          pool[i].u.i64 = (int64_t)i;
+        }
+        break;
+#else
+        return NULL;            /* INT64 not supported on MRB_32BIT */
+#endif
 
-#ifndef MRB_WITHOUT_FLOAT
       case IREP_TT_FLOAT:
-        irep->pool[i] = mrb_float_pool(mrb, str_to_double(mrb, s, pool_data_len));
+#ifndef MRB_NO_FLOAT
+        pool[i].tt = tt;
+         pool[i].u.f = str_to_double(mrb, (const char*)src);
+        src += sizeof(double);
         break;
+#else
+        return NULL;            /* MRB_NO_FLOAT */
 #endif
 
-      case IREP_TT_STRING:
-        irep->pool[i] = mrb_str_pool(mrb, s, pool_data_len, st);
+      case IREP_TT_STR:
+        pool_data_len = bin_to_uint16(src); /* pool data length */
+        src += sizeof(uint16_t);
+        if (st) {
+          pool[i].tt = (pool_data_len<<2) | IREP_TT_SSTR;
+          pool[i].u.str = (const char*)src;
+        }
+        else {
+          char *p;
+          pool[i].tt = (pool_data_len<<2) | IREP_TT_STR;
+          p = (char*)mrb_malloc(mrb, pool_data_len+1);
+          memcpy(p, src, pool_data_len+1);
+          pool[i].u.str = (const char*)p;
+        }
+        src += pool_data_len + 1;
         break;
 
       default:
         /* should not happen */
-        irep->pool[i] = mrb_nil_value();
-        break;
+        return NULL;
       }
-      irep->plen++;
-      mrb_gc_arena_restore(mrb, ai);
+      irep->plen = i+1;
     }
   }
 
   /* SYMS BLOCK */
-  irep->slen = (uint16_t)bin_to_uint32(src);  /* syms length */
-  src += sizeof(uint32_t);
+  irep->slen = bin_to_uint16(src);  /* syms length */
+  src += sizeof(uint16_t);
   if (irep->slen > 0) {
     if (SIZE_ERROR_MUL(irep->slen, sizeof(mrb_sym))) {
       return NULL;
     }
-    irep->syms = (mrb_sym *)mrb_malloc(mrb, sizeof(mrb_sym) * irep->slen);
+    irep->syms = syms = (mrb_sym *)mrb_malloc(mrb, sizeof(mrb_sym) * irep->slen);
 
     for (i = 0; i < irep->slen; i++) {
       snl = bin_to_uint16(src);               /* symbol name length */
       src += sizeof(uint16_t);
 
       if (snl == MRB_DUMP_NULL_SYM_LEN) {
-        irep->syms[i] = 0;
+        syms[i] = 0;
         continue;
       }
 
       if (flags & FLAG_SRC_MALLOC) {
-        irep->syms[i] = mrb_intern(mrb, (char *)src, snl);
+        syms[i] = mrb_intern(mrb, (char *)src, snl);
       }
       else {
-        irep->syms[i] = mrb_intern_static(mrb, (char *)src, snl);
+        syms[i] = mrb_intern_static(mrb, (char *)src, snl);
       }
       src += snl + 1;
-
       mrb_gc_arena_restore(mrb, ai);
     }
   }
 
-  irep->reps = (mrb_irep**)mrb_calloc(mrb, irep->rlen, sizeof(mrb_irep*));
-
   diff = src - bin;
   mrb_assert_int_fit(ptrdiff_t, diff, size_t, SIZE_MAX);
   *len = (size_t)diff;
@@ -213,6 +244,7 @@ read_irep_record(mrb_state *mrb, const uint8_t *bin, size_t *len, uint8_t flags)
   struct RData *irep_obj = mrb_data_object_alloc(mrb, mrb->object_class, NULL, &tempirep_type);
   int ai = mrb_gc_arena_save(mrb);
   mrb_irep *irep = read_irep_record_1(mrb, bin, len, flags);
+  mrb_irep **reps;
   int i;
 
   mrb_gc_arena_restore(mrb, ai);
@@ -220,15 +252,17 @@ read_irep_record(mrb_state *mrb, const uint8_t *bin, size_t *len, uint8_t flags)
     return NULL;
   }
 
+  reps = (mrb_irep**)mrb_calloc(mrb, irep->rlen, sizeof(mrb_irep*));
+  irep->reps = (const mrb_irep**)reps;
   irep_obj->data = irep;
 
   bin += *len;
   for (i=0; i<irep->rlen; i++) {
     size_t rlen;
 
-    irep->reps[i] = read_irep_record(mrb, bin, &rlen, flags);
+    reps[i] = read_irep_record(mrb, bin, &rlen, flags);
     mrb_gc_arena_restore(mrb, ai);
-    if (irep->reps[i] == NULL) {
+    if (reps[i] == NULL) {
       return NULL;
     }
     bin += rlen;
@@ -257,25 +291,26 @@ read_debug_record(mrb_state *mrb, const uint8_t *start, mrb_irep* irep, size_t *
   size_t record_size;
   uint16_t f_idx;
   int i;
+  mrb_irep_debug_info *debug;
 
   if (irep->debug_info) { return MRB_DUMP_INVALID_IREP; }
 
-  irep->debug_info = (mrb_irep_debug_info*)mrb_calloc(mrb, 1, sizeof(mrb_irep_debug_info));
-  irep->debug_info->pc_count = (uint32_t)irep->ilen;
+  irep->debug_info = debug = (mrb_irep_debug_info*)mrb_calloc(mrb, 1, sizeof(mrb_irep_debug_info));
+  debug->pc_count = (uint32_t)irep->ilen;
 
   record_size = (size_t)bin_to_uint32(bin);
   bin += sizeof(uint32_t);
 
-  irep->debug_info->flen = bin_to_uint16(bin);
-  irep->debug_info->files = (mrb_irep_debug_info_file**)mrb_calloc(mrb, irep->debug_info->flen, sizeof(mrb_irep_debug_info*));
+  debug->flen = bin_to_uint16(bin);
+  debug->files = (mrb_irep_debug_info_file**)mrb_calloc(mrb, irep->debug_info->flen, sizeof(mrb_irep_debug_info*));
   bin += sizeof(uint16_t);
 
-  for (f_idx = 0; f_idx < irep->debug_info->flen; ++f_idx) {
+  for (f_idx = 0; f_idx < debug->flen; ++f_idx) {
     mrb_irep_debug_info_file *file;
     uint16_t filename_idx;
 
     file = (mrb_irep_debug_info_file *)mrb_calloc(mrb, 1, sizeof(*file));
-    irep->debug_info->files[f_idx] = file;
+    debug->files[f_idx] = file;
 
     file->start_pos = bin_to_uint32(bin);
     bin += sizeof(uint32_t);
@@ -329,7 +364,7 @@ read_debug_record(mrb_state *mrb, const uint8_t *start, mrb_irep* irep, size_t *
     size_t len;
     int ret;
 
-    ret = read_debug_record(mrb, bin, irep->reps[i], &len, filenames, filenames_len);
+    ret = read_debug_record(mrb, bin, (mrb_irep*)irep->reps[i], &len, filenames, filenames_len);
     if (ret != MRB_DUMP_OK) return ret;
     bin += len;
   }
@@ -393,34 +428,31 @@ static int
 read_lv_record(mrb_state *mrb, const uint8_t *start, mrb_irep *irep, size_t *record_len, mrb_sym const *syms, uint32_t syms_len)
 {
   const uint8_t *bin = start;
+  mrb_sym *lv;
   ptrdiff_t diff;
   int i;
 
-  irep->lv = (struct mrb_locals*)mrb_malloc(mrb, sizeof(struct mrb_locals) * (irep->nlocals - 1));
+  irep->lv = lv = (mrb_sym*)mrb_malloc(mrb, sizeof(mrb_sym) * (irep->nlocals - 1));
 
   for (i = 0; i + 1< irep->nlocals; ++i) {
     uint16_t const sym_idx = bin_to_uint16(bin);
     bin += sizeof(uint16_t);
     if (sym_idx == RITE_LV_NULL_MARK) {
-      irep->lv[i].name = 0;
-      irep->lv[i].r = 0;
+      lv[i] = 0;
     }
     else {
       if (sym_idx >= syms_len) {
         return MRB_DUMP_GENERAL_FAILURE;
       }
-      irep->lv[i].name = syms[sym_idx];
-
-      irep->lv[i].r = bin_to_uint16(bin);
+      lv[i] = syms[sym_idx];
     }
-    bin += sizeof(uint16_t);
   }
 
   for (i = 0; i < irep->rlen; ++i) {
     size_t len;
     int ret;
 
-    ret = read_lv_record(mrb, bin, irep->reps[i], &len, syms, syms_len);
+    ret = read_lv_record(mrb, bin, (mrb_irep*)irep->reps[i], &len, syms, syms_len);
     if (ret != MRB_DUMP_OK) return ret;
     bin += len;
   }
@@ -491,7 +523,12 @@ read_binary_header(const uint8_t *bin, size_t bufsize, size_t *bin_size, uint16_
     return MRB_DUMP_INVALID_FILE_HEADER;
   }
 
-  if (memcmp(header->binary_version, RITE_BINARY_FORMAT_VER, sizeof(header->binary_version)) != 0) {
+  /* if major version is different, they are incompatible */
+  if (memcmp(header->major_version, RITE_BINARY_MAJOR_VER, sizeof(header->major_version)) != 0) {
+    return MRB_DUMP_INVALID_FILE_HEADER;
+  }
+  /* if minor version is different, we can accept the older version */
+  if (memcmp(header->minor_version, RITE_BINARY_MINOR_VER, sizeof(header->minor_version)) <= 0) {
     return MRB_DUMP_INVALID_FILE_HEADER;
   }
 
@@ -587,7 +624,7 @@ void mrb_exc_set(mrb_state *mrb, mrb_value exc);
 static void
 irep_error(mrb_state *mrb)
 {
-  mrb_exc_set(mrb, mrb_exc_new_str_lit(mrb, E_SCRIPT_ERROR, "irep load error"));
+  mrb_exc_set(mrb, mrb_exc_new_lit(mrb, E_SCRIPT_ERROR, "irep load error"));
 }
 
 void mrb_codedump_all(mrb_state*, struct RProc*);
@@ -642,6 +679,12 @@ mrb_load_irep_buf(mrb_state *mrb, const void *buf, size_t bufsize)
   return mrb_load_irep_buf_cxt(mrb, buf, bufsize, NULL);
 }
 
+MRB_API mrb_value
+mrb_load_proc(mrb_state *mrb, const struct RProc *proc)
+{
+  return mrb_vm_run(mrb, proc, mrb_top_self(mrb), 0);
+}
+
 #ifndef MRB_DISABLE_STDIO
 
 mrb_irep*
diff --git a/src/numeric.c b/src/numeric.c
index f4961928b..e1898301e 100644
--- a/src/numeric.c
+++ b/src/numeric.c
@@ -1,10 +1,10 @@
 /*
-** numeric.c - Numeric, Integer, Float, Fixnum class
+** numeric.c - Numeric, Integer, Float class
 **
 ** See Copyright Notice in mruby.h
 */
 
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
 #include <float.h>
 #include <math.h>
 #endif
@@ -18,8 +18,8 @@
 #include <mruby/string.h>
 #include <mruby/class.h>
 
-#ifndef MRB_WITHOUT_FLOAT
-#ifdef MRB_USE_FLOAT
+#ifndef MRB_NO_FLOAT
+#ifdef MRB_USE_FLOAT32
 #define trunc(f) truncf(f)
 #define floor(f) floorf(f)
 #define ceil(f) ceilf(f)
@@ -30,13 +30,13 @@
 #endif
 #endif
 
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
 MRB_API mrb_float
 mrb_to_flo(mrb_state *mrb, mrb_value val)
 {
   switch (mrb_type(val)) {
-  case MRB_TT_FIXNUM:
-    return (mrb_float)mrb_fixnum(val);
+  case MRB_TT_INTEGER:
+    return (mrb_float)mrb_integer(val);
   case MRB_TT_FLOAT:
     break;
   default:
@@ -44,15 +44,6 @@ mrb_to_flo(mrb_state *mrb, mrb_value val)
   }
   return mrb_float(val);
 }
-
-MRB_API mrb_value
-mrb_int_value(mrb_state *mrb, mrb_float f)
-{
-  if (FIXABLE_FLOAT(f)) {
-    return mrb_fixnum_value((mrb_int)f);
-  }
-  return mrb_float_value(mrb, f);
-}
 #endif
 
 /*
@@ -65,80 +56,125 @@ mrb_int_value(mrb_state *mrb, mrb_float f)
  *    2.0**3      #=> 8.0
  */
 static mrb_value
-integral_pow(mrb_state *mrb, mrb_value x)
+int_pow(mrb_state *mrb, mrb_value x)
 {
-  mrb_value y = mrb_get_arg1(mrb);
-#ifndef MRB_WITHOUT_FLOAT
-  mrb_float d;
-#endif
+  mrb_int base = mrb_int(mrb, x);
+  mrb_int exp;
+#ifndef MRB_NO_FLOAT
+  mrb_value y;
+  mrb_float z;
 
-  if (mrb_fixnum_p(x) && mrb_fixnum_p(y)) {
-    /* try ipow() */
-    mrb_int base = mrb_fixnum(x);
-    mrb_int exp = mrb_fixnum(y);
-    mrb_int result = 1;
-
-    if (exp < 0)
-#ifdef MRB_WITHOUT_FLOAT
-      return mrb_fixnum_value(0);
+  mrb_get_args(mrb, "o", &y);
+  if (!mrb_integer_p(y)) {
+    mrb_get_args(mrb, "f", &z);
+    z = pow((mrb_float)base, z);
+    return mrb_float_value(mrb, z);
+  }
+  else {
+    mrb_get_args(mrb, "i", &exp);
+    z = pow((double)base, (double)exp);
+    if (exp < 0 || z < (mrb_float)MRB_INT_MIN || (mrb_float)MRB_INT_MAX < z) {
+      return mrb_float_value(mrb, z);
+    }
+  }
+  return mrb_int_value(mrb, (mrb_int)z);
 #else
-      goto float_pow;
-#endif
-    for (;;) {
-      if (exp & 1) {
-        if (mrb_int_mul_overflow(result, base, &result)) {
-#ifndef MRB_WITHOUT_FLOAT
-          goto float_pow;
-#endif
-        }
-      }
-      exp >>= 1;
-      if (exp == 0) break;
-      if (mrb_int_mul_overflow(base, base, &base)) {
-#ifndef MRB_WITHOUT_FLOAT
-        goto float_pow;
-#endif
+  mrb_int result = 1;
+
+  mrb_get_args(mrb, "i", &exp);
+  if (exp < 0) {
+    return mrb_fixnum_value(0);
+  }
+  for (;;) {
+    if (exp & 1) {
+      if (mrb_int_mul_overflow(result, base, &result)) {
+        mrb_raise(mrb, E_RANGE_ERROR, "integer overflow in division");
       }
     }
-    return mrb_fixnum_value(result);
+    exp >>= 1;
+    if (exp == 0) break;
+    if (mrb_int_mul_overflow(base, base, &base)) {
+      mrb_raise(mrb, E_RANGE_ERROR, "integer overflow in division");
+    }
   }
-#ifdef MRB_WITHOUT_FLOAT
-  mrb_raise(mrb, E_TYPE_ERROR, "non fixnum value");
-#else
- float_pow:
-  d = pow(mrb_to_flo(mrb, x), mrb_to_flo(mrb, y));
-  return mrb_float_value(mrb, d);
+  return mrb_int_value(mrb, result);
 #endif
 }
 
-static mrb_value
-integral_idiv(mrb_state *mrb, mrb_value x)
-{
-#ifdef MRB_WITHOUT_FLOAT
-  mrb_value y = mrb_get_arg1(mrb);
 
-  if (!mrb_fixnum_p(y)) {
-    mrb_raise(mrb, E_TYPE_ERROR, "non fixnum value");
+mrb_int
+mrb_num_div_int(mrb_state *mrb, mrb_int x, mrb_int y)
+{
+  if (y == 0) {
+    mrb_raise(mrb, E_ZERODIV_ERROR, "divided by 0");
   }
-  return mrb_fixnum_value(mrb_fixnum(x) / mrb_fixnum(y));
-#else
-  mrb_float y;
+  else if(x == MRB_INT_MIN && y == -1) {
+    mrb_raise(mrb, E_RANGE_ERROR, "integer overflow in division");
+  }
+  else {
+    mrb_int div, mod;
 
-  mrb_get_args(mrb, "f", &y);
-  return mrb_int_value(mrb, mrb_to_flo(mrb, x) / y);
-#endif
+    if (y < 0) {
+      if (x < 0)
+        div = -x / -y;
+      else
+        div = - (x / -y);
+    }
+    else {
+      if (x < 0)
+        div = - (-x / y);
+      else
+        div = x / y;
+    }
+    mod = x - div * y;
+    if ((mod < 0 && y > 0) || (mod > 0 && y < 0)) {
+      div -= 1;
+    }
+    return div;
+  }
+  /* not reached */
+  return 0;
 }
 
 /* 15.2.8.3.4  */
 /* 15.2.9.3.4  */
 /*
  * call-seq:
- *   num / other  ->  num
+ *   int / other  ->  int
  *
  * Performs division: the class of the resulting object depends on
  * the class of <code>num</code> and on the magnitude of the
  * result.
  */
+static mrb_value
+int_div(mrb_state *mrb, mrb_value xv)
+{
+#ifndef MRB_NO_FLOAT
+  mrb_value yv;
+
+  mrb_get_args(mrb, "o", &yv);
+  if (mrb_float_p(yv)) {
+    double d = mrb_integer(xv)/mrb_float(yv);
+#ifdef MRB_INT32
+    if (MRB_INT_MIN <= d && d <= MRB_INT_MAX)
+      return mrb_int_value(mrb, (mrb_int)d);
+    return mrb_float_value(mrb, d);
+#else
+    return mrb_int_value(mrb, (mrb_int)d);
+#endif
+  }
+  else
+#endif
+  {
+    mrb_int y;
+
+    mrb_get_args(mrb, "i", &y);
+    if (y == 0) {
+      mrb_raise(mrb, E_ZERODIV_ERROR, "devided by zero");
+    }
+    return mrb_int_value(mrb, mrb_integer(xv) / y);
+  }
+}
 
 /* 15.2.9.3.19(x) */
 /*
@@ -149,42 +185,32 @@ integral_idiv(mrb_state *mrb, mrb_value x)
  */
 
 static mrb_value
-integral_div(mrb_state *mrb, mrb_value xv)
+int_quo(mrb_state *mrb, mrb_value xv)
 {
-#ifdef MRB_WITHOUT_FLOAT
+#ifdef MRB_NO_FLOAT
   mrb_int y;
 
   mrb_get_args(mrb, "i", &y);
   if (y == 0) {
-    mrb_raise(mrb, E_RUNTIME_ERROR, "devided by zero");
+    mrb_raise(mrb, E_ZERODIV_ERROR, "devided by zero");
   }
   return mrb_fixnum_value(mrb_fixnum(xv) / y);
 #else
-  mrb_float x, y;
+  mrb_float y;
 
   mrb_get_args(mrb, "f", &y);
-  x = mrb_to_flo(mrb, xv);
-  if (y == 0) {
-    if (x < 0)
-      y = -INFINITY;
-    else if (x > 0)
-      y = INFINITY;
-    else /* if (x == 0) */
-      y = NAN;
-    return mrb_float_value(mrb, y);
-  }
-  return mrb_float_value(mrb, x / y);
+  return mrb_float_value(mrb, (mrb_float)mrb_integer(xv) / y);
 #endif
 }
 
 static mrb_value
-integral_coerce_step_counter(mrb_state *mrb, mrb_value self)
+coerce_step_counter(mrb_state *mrb, mrb_value self)
 {
   mrb_value num, step;
 
   mrb_get_args(mrb, "oo", &num, &step);
 
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
   if (mrb_float_p(self) || mrb_float_p(num) || mrb_float_p(step)) {
     return mrb_Float(mrb, self);
   }
@@ -193,7 +219,7 @@ integral_coerce_step_counter(mrb_state *mrb, mrb_value self)
   return self;
 }
 
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
 /********************************************************************
  *
  * Document-class: Float
@@ -203,19 +229,59 @@ integral_coerce_step_counter(mrb_state *mrb, mrb_value self)
  *  representation.
  */
 
-/* 15.2.9.3.16(x) */
-/*
- *  call-seq:
- *     flt.to_s  ->  string
- *
- *  Returns a string containing a representation of self. As well as a
- *  fixed or exponential form of the number, the call may return
- *  "<code>NaN</code>", "<code>Infinity</code>", and
- *  "<code>-Infinity</code>".
- */
+static mrb_value
+flo_pow(mrb_state *mrb, mrb_value x)
+{
+  mrb_value y = mrb_get_arg1(mrb);
+  mrb_float d = pow(mrb_to_flo(mrb, x), mrb_to_flo(mrb, y));
+  return mrb_float_value(mrb, d);
+}
 
 static mrb_value
-flo_to_s(mrb_state *mrb, mrb_value flt)
+flo_idiv(mrb_state *mrb, mrb_value x)
+{
+  mrb_float y;
+
+  mrb_get_args(mrb, "f", &y);
+  y = mrb_to_flo(mrb, x) / y;
+#ifdef MRB_INT32
+  if (MRB_INT_MIN <= y && y <= MRB_INT_MAX)
+    return mrb_int_value(mrb, (mrb_int)y);
+  return mrb_float_value(mrb, y);
+#else
+  return mrb_int_value(mrb, (mrb_int)y);
+#endif
+}
+
+mrb_float
+mrb_num_div_flo(mrb_state *mrb, mrb_float x, mrb_float y)
+{
+  mrb_float f;
+
+  if (y == 0) {
+    if (x > 0) f = INFINITY;
+    else if (x < 0) f = -INFINITY;
+    else /* if (x == 0) */ f = NAN;
+  }
+  else {
+    f = x / y;
+  }
+  return f;
+}
+
+static mrb_value
+flo_div(mrb_state *mrb, mrb_value xv)
+{
+  mrb_float x, y;
+
+  x = mrb_float(xv);
+  mrb_get_args(mrb, "f", &y);
+  x = mrb_num_div_flo(mrb, x, y);
+  return mrb_float_value(mrb, x);
+}
+
+static mrb_value
+flo_to_str(mrb_state *mrb, mrb_value flt, mrb_bool add_dot_zero)
 {
   mrb_float f = mrb_float(flt);
   mrb_value str;
@@ -258,6 +324,9 @@ flo_to_s(mrb_state *mrb, mrb_value flt)
       str = mrb_float_to_str(mrb, flt, fmt);
       goto insert_dot_zero;
     }
+    else if (add_dot_zero) {
+      mrb_str_cat(mrb, str, ".0", 2);
+    }
 
     goto exit;
   }
@@ -267,6 +336,49 @@ flo_to_s(mrb_state *mrb, mrb_value flt)
   return str;
 }
 
+/* 15.2.9.3.16(x) */
+/*
+ *  call-seq:
+ *     flt.to_s  ->  string
+ *
+ *  Returns a string containing a representation of self. As well as a
+ *  fixed or exponential form of the number, the call may return
+ *  "<code>NaN</code>", "<code>Infinity</code>", and
+ *  "<code>-Infinity</code>".
+ *
+ *  Trailing <code>.0</code> is removed.
+ *
+ *     3.0.to_s   #=> 3
+ *     3.25.to_s  #=> 3.25
+ */
+
+static mrb_value
+flo_to_s(mrb_state *mrb, mrb_value flt)
+{
+  return flo_to_str(mrb, flt, FALSE);
+}
+
+/*
+ *  call-seq:
+ *     flt.inspect  ->  string
+ *
+ *  Returns a string containing a representation of self. As well as a
+ *  fixed or exponential form of the number, the call may return
+ *  "<code>NaN</code>", "<code>Infinity</code>", and
+ *  "<code>-Infinity</code>".
+ *
+ *  Trailing <code>.0</code> is added.
+ *
+ *     3.0.to_s   #=> 3.0
+ *     3.25.to_s  #=> 3.25
+ */
+
+static mrb_value
+flo_inspect(mrb_state *mrb, mrb_value flt)
+{
+  return flo_to_str(mrb, flt, TRUE);
+}
+
 /* 15.2.9.3.2  */
 /*
  * call-seq:
@@ -378,15 +490,15 @@ flo_mod(mrb_state *mrb, mrb_value x)
  *     (1.0).eql?(1.0)   #=> true
  */
 static mrb_value
-fix_eql(mrb_state *mrb, mrb_value x)
+int_eql(mrb_state *mrb, mrb_value x)
 {
   mrb_value y = mrb_get_arg1(mrb);
 
-  if (!mrb_fixnum_p(y)) return mrb_false_value();
-  return mrb_bool_value(mrb_fixnum(x) == mrb_fixnum(y));
+  if (!mrb_integer_p(y)) return mrb_false_value();
+  return mrb_bool_value(mrb_integer(x) == mrb_integer(y));
 }
 
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
 static mrb_value
 flo_eql(mrb_state *mrb, mrb_value x)
 {
@@ -415,8 +527,8 @@ flo_eq(mrb_state *mrb, mrb_value x)
   mrb_value y = mrb_get_arg1(mrb);
 
   switch (mrb_type(y)) {
-  case MRB_TT_FIXNUM:
-    return mrb_bool_value(mrb_float(x) == (mrb_float)mrb_fixnum(y));
+  case MRB_TT_INTEGER:
+    return mrb_bool_value(mrb_float(x) == (mrb_float)mrb_integer(y));
   case MRB_TT_FLOAT:
     return mrb_bool_value(mrb_float(x) == mrb_float(y));
   default:
@@ -428,8 +540,8 @@ static int64_t
 value_int64(mrb_state *mrb, mrb_value x)
 {
   switch (mrb_type(x)) {
-  case MRB_TT_FIXNUM:
-    return (int64_t)mrb_fixnum(x);
+  case MRB_TT_INTEGER:
+    return (int64_t)mrb_integer(x);
   case MRB_TT_FLOAT:
     return (int64_t)mrb_float(x);
   default:
@@ -525,7 +637,7 @@ flo_shift(mrb_state *mrb, mrb_value x, mrb_int width)
       val *= 2;
     }
   }
-  return mrb_int_value(mrb, val);
+  return mrb_int_value(mrb, (mrb_int)val);
 }
 
 static mrb_value
@@ -631,7 +743,7 @@ flo_floor(mrb_state *mrb, mrb_value num)
   mrb_float f = floor(mrb_float(num));
 
   mrb_check_num_exact(mrb, f);
-  return mrb_int_value(mrb, f);
+  return mrb_int_value(mrb, (mrb_int)f);
 }
 
 /* 15.2.9.3.8  */
@@ -654,7 +766,7 @@ flo_ceil(mrb_state *mrb, mrb_value num)
   mrb_float f = ceil(mrb_float(num));
 
   mrb_check_num_exact(mrb, f);
-  return mrb_int_value(mrb, f);
+  return mrb_int_value(mrb, (mrb_int)f);
 }
 
 /* 15.2.9.3.12 */
@@ -736,7 +848,7 @@ flo_round(mrb_state *mrb, mrb_value num)
     if (!isfinite(number)) return num;
     return mrb_float_value(mrb, number);
   }
-  return mrb_int_value(mrb, number);
+  return mrb_int_value(mrb, (mrb_int)number);
 }
 
 /* 15.2.9.3.14 */
@@ -758,7 +870,7 @@ flo_truncate(mrb_state *mrb, mrb_value num)
   if (f < 0.0) f = ceil(f);
 
   mrb_check_num_exact(mrb, f);
-  return mrb_int_value(mrb, f);
+  return mrb_int_value(mrb, (mrb_int)f);
 }
 
 static mrb_value
@@ -771,8 +883,7 @@ flo_nan_p(mrb_state *mrb, mrb_value num)
 /*
  * Document-class: Integer
  *
- *  <code>Integer</code> is the basis for the two concrete classes that
- *  hold whole numbers, <code>Bignum</code> and <code>Fixnum</code>.
+ *  <code>Integer</code> is hold whole numbers.
  *
  */
 
@@ -796,20 +907,20 @@ fixnum_mul(mrb_state *mrb, mrb_value x, mrb_value y)
 {
   mrb_int a;
 
-  a = mrb_fixnum(x);
-  if (mrb_fixnum_p(y)) {
+  a = mrb_integer(x);
+  if (mrb_integer_p(y)) {
     mrb_int b, c;
 
     if (a == 0) return x;
-    b = mrb_fixnum(y);
+    b = mrb_integer(y);
     if (mrb_int_mul_overflow(a, b, &c)) {
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
       return mrb_float_value(mrb, (mrb_float)a * (mrb_float)b);
 #endif
     }
     return mrb_fixnum_value(c);
   }
-#ifdef MRB_WITHOUT_FLOAT
+#ifdef MRB_NO_FLOAT
   mrb_raise(mrb, E_TYPE_ERROR, "non fixnum value");
 #else
   return mrb_float_value(mrb, (mrb_float)a * mrb_to_flo(mrb, y));
@@ -819,10 +930,10 @@ fixnum_mul(mrb_state *mrb, mrb_value x, mrb_value y)
 MRB_API mrb_value
 mrb_num_mul(mrb_state *mrb, mrb_value x, mrb_value y)
 {
-  if (mrb_fixnum_p(x)) {
+  if (mrb_integer_p(x)) {
     return fixnum_mul(mrb, x, y);
   }
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
   if (mrb_float_p(x)) {
     return mrb_float_value(mrb, mrb_float(x) * mrb_to_flo(mrb, y));
   }
@@ -842,7 +953,7 @@ mrb_num_mul(mrb_state *mrb, mrb_value x, mrb_value y)
  */
 
 static mrb_value
-fix_mul(mrb_state *mrb, mrb_value x)
+int_mul(mrb_state *mrb, mrb_value x)
 {
   mrb_value y = mrb_get_arg1(mrb);
 
@@ -888,29 +999,22 @@ fixdivmod(mrb_state *mrb, mrb_int x, mrb_int y, mrb_int *divp, mrb_int *modp)
  */
 
 static mrb_value
-fix_mod(mrb_state *mrb, mrb_value x)
+int_mod(mrb_state *mrb, mrb_value x)
 {
   mrb_value y = mrb_get_arg1(mrb);
   mrb_int a, b;
 
-  a = mrb_fixnum(x);
-  if (mrb_fixnum_p(y) && a != MRB_INT_MIN && (b=mrb_fixnum(y)) != MRB_INT_MIN) {
+  a = mrb_integer(x);
+  if (mrb_integer_p(y) && a != MRB_INT_MIN && (b=mrb_integer(y)) != MRB_INT_MIN) {
     mrb_int mod;
 
     if (b == 0) {
-#ifdef MRB_WITHOUT_FLOAT
-      /* ZeroDivisionError */
-      return mrb_fixnum_value(0);
-#else
-      if (a > 0) return mrb_float_value(mrb, INFINITY);
-      if (a < 0) return mrb_float_value(mrb, INFINITY);
-      return mrb_float_value(mrb, NAN);
-#endif
+      mrb_raise(mrb, E_ZERODIV_ERROR, "divided by 0");
     }
     fixdivmod(mrb, a, b, NULL, &mod);
     return mrb_fixnum_value(mod);
   }
-#ifdef MRB_WITHOUT_FLOAT
+#ifdef MRB_NO_FLOAT
   mrb_raise(mrb, E_TYPE_ERROR, "non fixnum value");
 #else
   else {
@@ -929,42 +1033,35 @@ fix_mod(mrb_state *mrb, mrb_value x)
  *  See <code>Numeric#divmod</code>.
  */
 static mrb_value
-fix_divmod(mrb_state *mrb, mrb_value x)
+int_divmod(mrb_state *mrb, mrb_value x)
 {
   mrb_value y = mrb_get_arg1(mrb);
 
-  if (mrb_fixnum_p(y)) {
+  if (mrb_integer_p(y)) {
     mrb_int div, mod;
 
-    if (mrb_fixnum(y) == 0) {
-#ifdef MRB_WITHOUT_FLOAT
-      return mrb_assoc_new(mrb, mrb_fixnum_value(0), mrb_fixnum_value(0));
-#else
-      return mrb_assoc_new(mrb, ((mrb_fixnum(x) == 0) ?
-                                 mrb_float_value(mrb, NAN):
-                                 mrb_float_value(mrb, INFINITY)),
-                           mrb_float_value(mrb, NAN));
-#endif
+    if (mrb_integer(y) == 0) {
+      mrb_raise(mrb, E_ZERODIV_ERROR, "divided by 0");
     }
-    fixdivmod(mrb, mrb_fixnum(x), mrb_fixnum(y), &div, &mod);
-    return mrb_assoc_new(mrb, mrb_fixnum_value(div), mrb_fixnum_value(mod));
+    fixdivmod(mrb, mrb_integer(x), mrb_integer(y), &div, &mod);
+    return mrb_assoc_new(mrb, mrb_int_value(mrb, div), mrb_int_value(mrb, mod));
   }
-#ifdef MRB_WITHOUT_FLOAT
+#ifdef MRB_NO_FLOAT
   mrb_raise(mrb, E_TYPE_ERROR, "non fixnum value");
 #else
   else {
     mrb_float div, mod;
     mrb_value a, b;
 
-    flodivmod(mrb, (mrb_float)mrb_fixnum(x), mrb_to_flo(mrb, y), &div, &mod);
-    a = mrb_int_value(mrb, div);
+    flodivmod(mrb, (mrb_float)mrb_integer(x), mrb_to_flo(mrb, y), &div, &mod);
+    a = mrb_int_value(mrb, (mrb_int)div);
     b = mrb_float_value(mrb, mod);
     return mrb_assoc_new(mrb, a, b);
   }
 #endif
 }
 
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
 static mrb_value
 flo_divmod(mrb_state *mrb, mrb_value x)
 {
@@ -973,7 +1070,7 @@ flo_divmod(mrb_state *mrb, mrb_value x)
   mrb_value a, b;
 
   flodivmod(mrb, mrb_float(x), mrb_to_flo(mrb, y), &div, &mod);
-  a = mrb_int_value(mrb, div);
+  a = mrb_int_value(mrb, (mrb_int)div);
   b = mrb_float_value(mrb, mod);
   return mrb_assoc_new(mrb, a, b);
 }
@@ -992,16 +1089,16 @@ flo_divmod(mrb_state *mrb, mrb_value x)
  */
 
 static mrb_value
-fix_equal(mrb_state *mrb, mrb_value x)
+int_equal(mrb_state *mrb, mrb_value x)
 {
   mrb_value y = mrb_get_arg1(mrb);
 
   switch (mrb_type(y)) {
-  case MRB_TT_FIXNUM:
-    return mrb_bool_value(mrb_fixnum(x) == mrb_fixnum(y));
-#ifndef MRB_WITHOUT_FLOAT
+  case MRB_TT_INTEGER:
+    return mrb_bool_value(mrb_integer(x) == mrb_integer(y));
+#ifndef MRB_NO_FLOAT
   case MRB_TT_FLOAT:
-    return mrb_bool_value((mrb_float)mrb_fixnum(x) == mrb_float(y));
+    return mrb_bool_value((mrb_float)mrb_integer(x) == mrb_float(y));
 #endif
   default:
     return mrb_false_value();
@@ -1020,24 +1117,24 @@ fix_equal(mrb_state *mrb, mrb_value x)
  */
 
 static mrb_value
-fix_rev(mrb_state *mrb, mrb_value num)
+int_rev(mrb_state *mrb, mrb_value num)
 {
-  mrb_int val = mrb_fixnum(num);
+  mrb_int val = mrb_integer(num);
 
-  return mrb_fixnum_value(~val);
+  return mrb_int_value(mrb, ~val);
 }
 
-#ifdef MRB_WITHOUT_FLOAT
+#ifdef MRB_NO_FLOAT
 #define bit_op(x,y,op1,op2) do {\
-  return mrb_fixnum_value(mrb_fixnum(x) op2 mrb_fixnum(y));\
+  return mrb_int_value(mrb, (mrb_integer(x) op2 mrb_integer(y)));\
 } while(0)
 #else
 static mrb_value flo_and(mrb_state *mrb, mrb_value x);
 static mrb_value flo_or(mrb_state *mrb, mrb_value x);
 static mrb_value flo_xor(mrb_state *mrb, mrb_value x);
 #define bit_op(x,y,op1,op2) do {\
-  if (mrb_fixnum_p(y)) return mrb_fixnum_value(mrb_fixnum(x) op2 mrb_fixnum(y));\
-  return flo_ ## op1(mrb, mrb_float_value(mrb, (mrb_float)mrb_fixnum(x)));\
+  if (mrb_integer_p(y)) return mrb_int_value(mrb, (mrb_integer(x) op2 mrb_integer(y))); \
+  return flo_ ## op1(mrb, mrb_float_value(mrb, (mrb_float)mrb_integer(x)));\
 } while(0)
 #endif
 
@@ -1050,7 +1147,7 @@ static mrb_value flo_xor(mrb_state *mrb, mrb_value x);
  */
 
 static mrb_value
-fix_and(mrb_state *mrb, mrb_value x)
+int_and(mrb_state *mrb, mrb_value x)
 {
   mrb_value y = mrb_get_arg1(mrb);
 
@@ -1066,7 +1163,7 @@ fix_and(mrb_state *mrb, mrb_value x)
  */
 
 static mrb_value
-fix_or(mrb_state *mrb, mrb_value x)
+int_or(mrb_state *mrb, mrb_value x)
 {
   mrb_value y = mrb_get_arg1(mrb);
 
@@ -1082,7 +1179,7 @@ fix_or(mrb_state *mrb, mrb_value x)
  */
 
 static mrb_value
-fix_xor(mrb_state *mrb, mrb_value x)
+int_xor(mrb_state *mrb, mrb_value x)
 {
   mrb_value y = mrb_get_arg1(mrb);
 
@@ -1095,7 +1192,7 @@ static mrb_value
 lshift(mrb_state *mrb, mrb_int val, mrb_int width)
 {
   if (width < 0) {              /* mrb_int overflow */
-#ifdef MRB_WITHOUT_FLOAT
+#ifdef MRB_NO_FLOAT
     return mrb_fixnum_value(0);
 #else
     return mrb_float_value(mrb, INFINITY);
@@ -1104,27 +1201,27 @@ lshift(mrb_state *mrb, mrb_int val, mrb_int width)
   if (val > 0) {
     if ((width > NUMERIC_SHIFT_WIDTH_MAX) ||
         (val   > (MRB_INT_MAX >> width))) {
-#ifdef MRB_WITHOUT_FLOAT
+#ifdef MRB_NO_FLOAT
       return mrb_fixnum_value(-1);
 #else
       goto bit_overflow;
 #endif
     }
-    return mrb_fixnum_value(val << width);
+    return mrb_int_value(mrb, val << width);
   }
   else {
     if ((width > NUMERIC_SHIFT_WIDTH_MAX) ||
         (val   <= (MRB_INT_MIN >> width))) {
-#ifdef MRB_WITHOUT_FLOAT
+#ifdef MRB_NO_FLOAT
       return mrb_fixnum_value(0);
 #else
       goto bit_overflow;
 #endif
     }
-    return mrb_fixnum_value(val * ((mrb_int)1 << width));
+    return mrb_int_value(mrb, (val * ((mrb_int)1 << width)));
   }
 
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
 bit_overflow:
   {
     mrb_float f = (mrb_float)val;
@@ -1137,7 +1234,7 @@ bit_overflow:
 }
 
 static mrb_value
-rshift(mrb_int val, mrb_int width)
+rshift(mrb_state *mrb, mrb_int val, mrb_int width)
 {
   if (width < 0) {              /* mrb_int overflow */
     return mrb_fixnum_value(0);
@@ -1148,7 +1245,7 @@ rshift(mrb_int val, mrb_int width)
     }
     return mrb_fixnum_value(0);
   }
-  return mrb_fixnum_value(val >> width);
+  return mrb_int_value(mrb, val >> width);
 }
 
 /* 15.2.8.3.12 */
@@ -1160,7 +1257,7 @@ rshift(mrb_int val, mrb_int width)
  */
 
 static mrb_value
-fix_lshift(mrb_state *mrb, mrb_value x)
+int_lshift(mrb_state *mrb, mrb_value x)
 {
   mrb_int width, val;
 
@@ -1168,10 +1265,10 @@ fix_lshift(mrb_state *mrb, mrb_value x)
   if (width == 0) {
     return x;
   }
-  val = mrb_fixnum(x);
+  val = mrb_integer(x);
   if (val == 0) return x;
   if (width < 0) {
-    return rshift(val, -width);
+    return rshift(mrb, val, -width);
   }
   return lshift(mrb, val, width);
 }
@@ -1185,7 +1282,7 @@ fix_lshift(mrb_state *mrb, mrb_value x)
  */
 
 static mrb_value
-fix_rshift(mrb_state *mrb, mrb_value x)
+int_rshift(mrb_state *mrb, mrb_value x)
 {
   mrb_int width, val;
 
@@ -1193,12 +1290,12 @@ fix_rshift(mrb_state *mrb, mrb_value x)
   if (width == 0) {
     return x;
   }
-  val = mrb_fixnum(x);
+  val = mrb_integer(x);
   if (val == 0) return x;
   if (width < 0) {
     return lshift(mrb, val, -width);
   }
-  return rshift(val, width);
+  return rshift(mrb, val, width);
 }
 
 /* 15.2.8.3.23 */
@@ -1210,11 +1307,11 @@ fix_rshift(mrb_state *mrb, mrb_value x)
  *
  */
 
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
 static mrb_value
-fix_to_f(mrb_state *mrb, mrb_value num)
+int_to_f(mrb_state *mrb, mrb_value num)
 {
-  return mrb_float_value(mrb, (mrb_float)mrb_fixnum(num));
+  return mrb_float_value(mrb, (mrb_float)mrb_integer(num));
 }
 
 /*
@@ -1251,7 +1348,7 @@ mrb_flo_to_fixnum(mrb_state *mrb, mrb_value x)
       mrb_raisef(mrb, E_RANGE_ERROR, "number (%v) too big for integer", x);
     }
   }
-  return mrb_fixnum_value(z);
+  return mrb_int_value(mrb, z);
 }
 #endif
 
@@ -1260,20 +1357,20 @@ fixnum_plus(mrb_state *mrb, mrb_value x, mrb_value y)
 {
   mrb_int a;
 
-  a = mrb_fixnum(x);
-  if (mrb_fixnum_p(y)) {
+  a = mrb_integer(x);
+  if (mrb_integer_p(y)) {
     mrb_int b, c;
 
     if (a == 0) return y;
-    b = mrb_fixnum(y);
+    b = mrb_integer(y);
     if (mrb_int_add_overflow(a, b, &c)) {
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
       return mrb_float_value(mrb, (mrb_float)a + (mrb_float)b);
 #endif
     }
-    return mrb_fixnum_value(c);
+    return mrb_int_value(mrb, c);
   }
-#ifdef MRB_WITHOUT_FLOAT
+#ifdef MRB_NO_FLOAT
   mrb_raise(mrb, E_TYPE_ERROR, "non fixnum value");
 #else
   return mrb_float_value(mrb, (mrb_float)a + mrb_to_flo(mrb, y));
@@ -1283,10 +1380,10 @@ fixnum_plus(mrb_state *mrb, mrb_value x, mrb_value y)
 MRB_API mrb_value
 mrb_num_plus(mrb_state *mrb, mrb_value x, mrb_value y)
 {
-  if (mrb_fixnum_p(x)) {
+  if (mrb_integer_p(x)) {
     return fixnum_plus(mrb, x, y);
   }
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
   if (mrb_float_p(x)) {
     return mrb_float_value(mrb, mrb_float(x) + mrb_to_flo(mrb, y));
   }
@@ -1305,7 +1402,7 @@ mrb_num_plus(mrb_state *mrb, mrb_value x, mrb_value y)
  * result.
  */
 static mrb_value
-fix_plus(mrb_state *mrb, mrb_value self)
+int_plus(mrb_state *mrb, mrb_value self)
 {
   mrb_value other = mrb_get_arg1(mrb);
 
@@ -1317,19 +1414,19 @@ fixnum_minus(mrb_state *mrb, mrb_value x, mrb_value y)
 {
   mrb_int a;
 
-  a = mrb_fixnum(x);
-  if (mrb_fixnum_p(y)) {
+  a = mrb_integer(x);
+  if (mrb_integer_p(y)) {
     mrb_int b, c;
 
-    b = mrb_fixnum(y);
+    b = mrb_integer(y);
     if (mrb_int_sub_overflow(a, b, &c)) {
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
       return mrb_float_value(mrb, (mrb_float)a - (mrb_float)b);
 #endif
     }
-    return mrb_fixnum_value(c);
+    return mrb_int_value(mrb, c);
   }
-#ifdef MRB_WITHOUT_FLOAT
+#ifdef MRB_NO_FLOAT
   mrb_raise(mrb, E_TYPE_ERROR, "non fixnum value");
 #else
   return mrb_float_value(mrb, (mrb_float)a - mrb_to_flo(mrb, y));
@@ -1339,10 +1436,10 @@ fixnum_minus(mrb_state *mrb, mrb_value x, mrb_value y)
 MRB_API mrb_value
 mrb_num_minus(mrb_state *mrb, mrb_value x, mrb_value y)
 {
-  if (mrb_fixnum_p(x)) {
+  if (mrb_integer_p(x)) {
     return fixnum_minus(mrb, x, y);
   }
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
   if (mrb_float_p(x)) {
     return mrb_float_value(mrb, mrb_float(x) - mrb_to_flo(mrb, y));
   }
@@ -1362,7 +1459,7 @@ mrb_num_minus(mrb_state *mrb, mrb_value x, mrb_value y)
  * result.
  */
 static mrb_value
-fix_minus(mrb_state *mrb, mrb_value self)
+int_minus(mrb_state *mrb, mrb_value self)
 {
   mrb_value other = mrb_get_arg1(mrb);
 
@@ -1375,7 +1472,7 @@ mrb_fixnum_to_str(mrb_state *mrb, mrb_value x, mrb_int base)
 {
   char buf[MRB_INT_BIT+1];
   char *b = buf + sizeof buf;
-  mrb_int val = mrb_fixnum(x);
+  mrb_int val = mrb_integer(x);
   mrb_value str;
 
   if (base < 2 || 36 < base) {
@@ -1419,7 +1516,7 @@ mrb_fixnum_to_str(mrb_state *mrb, mrb_value x, mrb_int base)
  *
  */
 static mrb_value
-fix_to_s(mrb_state *mrb, mrb_value self)
+int_to_s(mrb_state *mrb, mrb_value self)
 {
   mrb_int base = 10;
 
@@ -1431,26 +1528,26 @@ fix_to_s(mrb_state *mrb, mrb_value self)
 static mrb_int
 cmpnum(mrb_state *mrb, mrb_value v1, mrb_value v2)
 {
-#ifdef MRB_WITHOUT_FLOAT
+#ifdef MRB_NO_FLOAT
   mrb_int x, y;
 #else
   mrb_float x, y;
 #endif
 
-#ifdef MRB_WITHOUT_FLOAT
-  x = mrb_fixnum(v1);
+#ifdef MRB_NO_FLOAT
+  x = mrb_integer(v1);
 #else
   x = mrb_to_flo(mrb, v1);
 #endif
   switch (mrb_type(v2)) {
-  case MRB_TT_FIXNUM:
-#ifdef MRB_WITHOUT_FLOAT
-    y = mrb_fixnum(v2);
+  case MRB_TT_INTEGER:
+#ifdef MRB_NO_FLOAT
+    y = mrb_integer(v2);
 #else
-    y = (mrb_float)mrb_fixnum(v2);
+    y = (mrb_float)mrb_integer(v2);
 #endif
     break;
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
   case MRB_TT_FLOAT:
     y = mrb_float(v2);
     break;
@@ -1480,7 +1577,7 @@ cmpnum(mrb_state *mrb, mrb_value v1, mrb_value v2)
  *  not comparable, it returns nil instead of raising an exception.
  */
 static mrb_value
-integral_cmp(mrb_state *mrb, mrb_value self)
+num_cmp(mrb_state *mrb, mrb_value self)
 {
   mrb_value other = mrb_get_arg1(mrb);
   mrb_int n;
@@ -1497,7 +1594,7 @@ cmperr(mrb_state *mrb, mrb_value v1, mrb_value v2)
 }
 
 static mrb_value
-integral_lt(mrb_state *mrb, mrb_value self)
+num_lt(mrb_state *mrb, mrb_value self)
 {
   mrb_value other = mrb_get_arg1(mrb);
   mrb_int n;
@@ -1509,7 +1606,7 @@ integral_lt(mrb_state *mrb, mrb_value self)
 }
 
 static mrb_value
-integral_le(mrb_state *mrb, mrb_value self)
+num_le(mrb_state *mrb, mrb_value self)
 {
   mrb_value other = mrb_get_arg1(mrb);
   mrb_int n;
@@ -1521,7 +1618,7 @@ integral_le(mrb_state *mrb, mrb_value self)
 }
 
 static mrb_value
-integral_gt(mrb_state *mrb, mrb_value self)
+num_gt(mrb_state *mrb, mrb_value self)
 {
   mrb_value other = mrb_get_arg1(mrb);
   mrb_int n;
@@ -1533,7 +1630,7 @@ integral_gt(mrb_state *mrb, mrb_value self)
 }
 
 static mrb_value
-integral_ge(mrb_state *mrb, mrb_value self)
+num_ge(mrb_state *mrb, mrb_value self)
 {
   mrb_value other = mrb_get_arg1(mrb);
   mrb_int n;
@@ -1550,7 +1647,7 @@ mrb_cmp(mrb_state *mrb, mrb_value obj1, mrb_value obj2)
   mrb_value v;
 
   switch (mrb_type(obj1)) {
-  case MRB_TT_FIXNUM:
+  case MRB_TT_INTEGER:
   case MRB_TT_FLOAT:
     return cmpnum(mrb, obj1, obj2);
   case MRB_TT_STRING:
@@ -1558,10 +1655,10 @@ mrb_cmp(mrb_state *mrb, mrb_value obj1, mrb_value obj2)
       return -2;
     return mrb_str_cmp(mrb, obj1, obj2);
   default:
-    v = mrb_funcall(mrb, obj1, "<=>", 1, obj2);
-    if (mrb_nil_p(v) || !mrb_fixnum_p(v))
+    v = mrb_funcall_id(mrb, obj1, MRB_SYM(cmp), 1, obj2);
+    if (mrb_nil_p(v) || !mrb_integer_p(v))
       return -2;
-    return mrb_fixnum(v);
+    return mrb_integer(v);
   }
 }
 
@@ -1585,7 +1682,7 @@ num_infinite_p(mrb_state *mrb, mrb_value self)
  * Returns a new float which is the sum of <code>float</code>
  * and <code>other</code>.
  */
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
 static mrb_value
 flo_plus(mrb_state *mrb, mrb_value x)
 {
@@ -1599,72 +1696,81 @@ flo_plus(mrb_state *mrb, mrb_value x)
 void
 mrb_init_numeric(mrb_state *mrb)
 {
-  struct RClass *numeric, *integer, *fixnum, *integral;
-#ifndef MRB_WITHOUT_FLOAT
+  struct RClass *numeric, *integer;
+#ifndef MRB_NO_FLOAT
   struct RClass *fl;
 #endif
 
-  integral = mrb_define_module(mrb, "Integral");
-  mrb_define_method(mrb, integral,"**",       integral_pow,    MRB_ARGS_REQ(1));
-  mrb_define_method(mrb, integral,"/",        integral_div,    MRB_ARGS_REQ(1)); /* 15.2.{8,9}.3.6  */
-  mrb_define_method(mrb, integral,"quo",      integral_div,    MRB_ARGS_REQ(1)); /* 15.2.7.4.5 (x) */
-  mrb_define_method(mrb, integral,"div",      integral_idiv,   MRB_ARGS_REQ(1));
-  mrb_define_method(mrb, integral,"<=>",      integral_cmp,    MRB_ARGS_REQ(1)); /* 15.2.{8,9}.3.1  */
-  mrb_define_method(mrb, integral,"<",        integral_lt,     MRB_ARGS_REQ(1));
-  mrb_define_method(mrb, integral,"<=",       integral_le,     MRB_ARGS_REQ(1));
-  mrb_define_method(mrb, integral,">",        integral_gt,     MRB_ARGS_REQ(1));
-  mrb_define_method(mrb, integral,">=",       integral_ge,     MRB_ARGS_REQ(1));
-  mrb_define_method(mrb, integral,"__coerce_step_counter", integral_coerce_step_counter, MRB_ARGS_REQ(2));
-
   /* Numeric Class */
   numeric = mrb_define_class(mrb, "Numeric",  mrb->object_class);                /* 15.2.7 */
   mrb_define_method(mrb, numeric, "finite?",  num_finite_p,    MRB_ARGS_NONE());
   mrb_define_method(mrb, numeric, "infinite?",num_infinite_p,  MRB_ARGS_NONE());
 
   /* Integer Class */
-  integer = mrb_define_class(mrb, "Integer",  numeric);                          /* 15.2.8 */
-  MRB_SET_INSTANCE_TT(integer, MRB_TT_FIXNUM);
+  mrb->integer_class = integer = mrb_define_class(mrb, "Integer",  numeric);     /* 15.2.8 */
+  MRB_SET_INSTANCE_TT(integer, MRB_TT_INTEGER);
   mrb_undef_class_method(mrb, integer, "new");
+  mrb_define_method(mrb, integer, "**",       int_pow,         MRB_ARGS_REQ(1));
+  mrb_define_method(mrb, integer, "/",        int_div,         MRB_ARGS_REQ(1)); /* 15.2.8.3.6  */
+  mrb_define_method(mrb, integer, "quo",      int_quo,         MRB_ARGS_REQ(1)); /* 15.2.7.4.5 (x) */
+  mrb_define_method(mrb, integer, "div",      int_div,        MRB_ARGS_REQ(1));
+  mrb_define_method(mrb, integer, "<=>",      num_cmp,         MRB_ARGS_REQ(1)); /* 15.2.8.3.1  */
+  mrb_define_method(mrb, integer, "<",        num_lt,          MRB_ARGS_REQ(1));
+  mrb_define_method(mrb, integer, "<=",       num_le,          MRB_ARGS_REQ(1));
+  mrb_define_method(mrb, integer, ">",        num_gt,          MRB_ARGS_REQ(1));
+  mrb_define_method(mrb, integer, ">=",       num_ge,          MRB_ARGS_REQ(1));
+
   mrb_define_method(mrb, integer, "to_i",     int_to_i,        MRB_ARGS_NONE()); /* 15.2.8.3.24 */
   mrb_define_method(mrb, integer, "to_int",   int_to_i,        MRB_ARGS_NONE());
-#ifndef MRB_WITHOUT_FLOAT
-  mrb_define_method(mrb, integer, "ceil",     int_to_i,        MRB_ARGS_NONE()); /* 15.2.8.3.8 (x) */
-  mrb_define_method(mrb, integer, "floor",    int_to_i,        MRB_ARGS_NONE()); /* 15.2.8.3.10 (x) */
-  mrb_define_method(mrb, integer, "round",    int_to_i,        MRB_ARGS_NONE()); /* 15.2.8.3.12 (x) */
-  mrb_define_method(mrb, integer, "truncate", int_to_i,        MRB_ARGS_NONE()); /* 15.2.8.3.15 (x) */
+#ifndef MRB_NO_FLOAT
+  mrb_define_method(mrb, integer, "ceil",     int_to_i,        MRB_ARGS_NONE()); /* 15.2.8.3.14 */
+  mrb_define_method(mrb, integer, "floor",    int_to_i,        MRB_ARGS_NONE()); /* 15.2.8.3.17 */
+  mrb_define_method(mrb, integer, "round",    int_to_i,        MRB_ARGS_NONE()); /* 15.2.8.3.20 */
+  mrb_define_method(mrb, integer, "truncate", int_to_i,        MRB_ARGS_NONE()); /* 15.2.8.3.26 */
 #endif
 
-  /* Fixnum Class */
-  mrb->fixnum_class = fixnum = mrb_define_class(mrb, "Fixnum", integer);
-  mrb_define_method(mrb, fixnum,  "+",        fix_plus,        MRB_ARGS_REQ(1)); /* 15.2.8.3.1  */
-  mrb_define_method(mrb, fixnum,  "-",        fix_minus,       MRB_ARGS_REQ(1)); /* 15.2.8.3.2  */
-  mrb_define_method(mrb, fixnum,  "*",        fix_mul,         MRB_ARGS_REQ(1)); /* 15.2.8.3.3  */
-  mrb_define_method(mrb, fixnum,  "%",        fix_mod,         MRB_ARGS_REQ(1)); /* 15.2.8.3.5  */
-  mrb_define_method(mrb, fixnum,  "==",       fix_equal,       MRB_ARGS_REQ(1)); /* 15.2.8.3.7  */
-  mrb_define_method(mrb, fixnum,  "~",        fix_rev,         MRB_ARGS_NONE()); /* 15.2.8.3.8  */
-  mrb_define_method(mrb, fixnum,  "&",        fix_and,         MRB_ARGS_REQ(1)); /* 15.2.8.3.9  */
-  mrb_define_method(mrb, fixnum,  "|",        fix_or,          MRB_ARGS_REQ(1)); /* 15.2.8.3.10 */
-  mrb_define_method(mrb, fixnum,  "^",        fix_xor,         MRB_ARGS_REQ(1)); /* 15.2.8.3.11 */
-  mrb_define_method(mrb, fixnum,  "<<",       fix_lshift,      MRB_ARGS_REQ(1)); /* 15.2.8.3.12 */
-  mrb_define_method(mrb, fixnum,  ">>",       fix_rshift,      MRB_ARGS_REQ(1)); /* 15.2.8.3.13 */
-  mrb_define_method(mrb, fixnum,  "eql?",     fix_eql,         MRB_ARGS_REQ(1)); /* 15.2.8.3.16 */
-#ifndef MRB_WITHOUT_FLOAT
-  mrb_define_method(mrb, fixnum,  "to_f",     fix_to_f,        MRB_ARGS_NONE()); /* 15.2.8.3.23 */
+  mrb_define_method(mrb, integer, "+",        int_plus,        MRB_ARGS_REQ(1)); /* 15.2.8.3.1 */
+  mrb_define_method(mrb, integer, "-",        int_minus,       MRB_ARGS_REQ(1)); /* 15.2.8.3.2 */
+  mrb_define_method(mrb, integer, "*",        int_mul,         MRB_ARGS_REQ(1)); /* 15.2.8.3.3 */
+  mrb_define_method(mrb, integer, "%",        int_mod,         MRB_ARGS_REQ(1)); /* 15.2.8.3.5 */
+  mrb_define_method(mrb, integer, "==",       int_equal,       MRB_ARGS_REQ(1)); /* 15.2.8.3.7 */
+  mrb_define_method(mrb, integer, "~",        int_rev,         MRB_ARGS_NONE()); /* 15.2.8.3.8 */
+  mrb_define_method(mrb, integer, "&",        int_and,         MRB_ARGS_REQ(1)); /* 15.2.8.3.9 */
+  mrb_define_method(mrb, integer, "|",        int_or,          MRB_ARGS_REQ(1)); /* 15.2.8.3.10 */
+  mrb_define_method(mrb, integer, "^",        int_xor,         MRB_ARGS_REQ(1)); /* 15.2.8.3.11 */
+  mrb_define_method(mrb, integer, "<<",       int_lshift,      MRB_ARGS_REQ(1)); /* 15.2.8.3.12 */
+  mrb_define_method(mrb, integer, ">>",       int_rshift,      MRB_ARGS_REQ(1)); /* 15.2.8.3.13 */
+  mrb_define_method(mrb, integer, "eql?",     int_eql,         MRB_ARGS_REQ(1)); /* 15.2.8.3.16 */
+#ifndef MRB_NO_FLOAT
+  mrb_define_method(mrb, integer, "to_f",     int_to_f,        MRB_ARGS_NONE()); /* 15.2.8.3.23 */
 #endif
-  mrb_define_method(mrb, fixnum,  "to_s",     fix_to_s,        MRB_ARGS_OPT(1)); /* 15.2.8.3.25 */
-  mrb_define_method(mrb, fixnum,  "inspect",  fix_to_s,        MRB_ARGS_OPT(1));
-  mrb_define_method(mrb, fixnum,  "divmod",   fix_divmod,      MRB_ARGS_REQ(1)); /* 15.2.8.3.30 (x) */
+  mrb_define_method(mrb, integer, "to_s",     int_to_s,        MRB_ARGS_OPT(1)); /* 15.2.8.3.25 */
+  mrb_define_method(mrb, integer, "inspect",  int_to_s,        MRB_ARGS_OPT(1));
+  mrb_define_method(mrb, integer, "divmod",   int_divmod,      MRB_ARGS_REQ(1)); /* 15.2.8.3.30 (x) */
+  mrb_define_method(mrb, integer, "__coerce_step_counter", coerce_step_counter, MRB_ARGS_REQ(2));
 
-#ifndef MRB_WITHOUT_FLOAT
+  /* Fixnum Class for compatibility */
+  mrb_define_const(mrb, mrb->object_class, "Fixnum", mrb_obj_value(integer));
+
+#ifndef MRB_NO_FLOAT
   /* Float Class */
   mrb->float_class = fl = mrb_define_class(mrb, "Float", numeric);                 /* 15.2.9 */
   MRB_SET_INSTANCE_TT(fl, MRB_TT_FLOAT);
   mrb_undef_class_method(mrb,  fl, "new");
-  mrb_define_method(mrb, fl,      "+",         flo_plus,       MRB_ARGS_REQ(1)); /* 15.2.9.3.1  */
-  mrb_define_method(mrb, fl,      "-",         flo_minus,      MRB_ARGS_REQ(1)); /* 15.2.9.3.2  */
-  mrb_define_method(mrb, fl,      "*",         flo_mul,        MRB_ARGS_REQ(1)); /* 15.2.9.3.3  */
-  mrb_define_method(mrb, fl,      "%",         flo_mod,        MRB_ARGS_REQ(1)); /* 15.2.9.3.5  */
-  mrb_define_method(mrb, fl,      "==",        flo_eq,         MRB_ARGS_REQ(1)); /* 15.2.9.3.7  */
+  mrb_define_method(mrb, fl,      "**",        flo_pow,        MRB_ARGS_REQ(1));
+  mrb_define_method(mrb, fl,      "/",         flo_div,        MRB_ARGS_REQ(1)); /* 15.2.9.3.6  */
+  mrb_define_method(mrb, fl,      "quo",       flo_div,        MRB_ARGS_REQ(1)); /* 15.2.7.4.5 (x) */
+  mrb_define_method(mrb, fl,      "div",       flo_idiv,       MRB_ARGS_REQ(1));
+  mrb_define_method(mrb, fl,      "+",         flo_plus,       MRB_ARGS_REQ(1)); /* 15.2.9.3.3  */
+  mrb_define_method(mrb, fl,      "-",         flo_minus,      MRB_ARGS_REQ(1)); /* 15.2.9.3.4  */
+  mrb_define_method(mrb, fl,      "*",         flo_mul,        MRB_ARGS_REQ(1)); /* 15.2.9.3.5  */
+  mrb_define_method(mrb, fl,      "%",         flo_mod,        MRB_ARGS_REQ(1)); /* 15.2.9.3.7  */
+  mrb_define_method(mrb, fl,      "<=>",       num_cmp,        MRB_ARGS_REQ(1)); /* 15.2.9.3.1  */
+  mrb_define_method(mrb, fl,      "<",         num_lt,         MRB_ARGS_REQ(1));
+  mrb_define_method(mrb, fl,      "<=",        num_le,         MRB_ARGS_REQ(1));
+  mrb_define_method(mrb, fl,      ">",         num_gt,         MRB_ARGS_REQ(1));
+  mrb_define_method(mrb, fl,      ">=",        num_ge,         MRB_ARGS_REQ(1));
+  mrb_define_method(mrb, fl,      "==",        flo_eq,         MRB_ARGS_REQ(1)); /* 15.2.9.3.2  */
   mrb_define_method(mrb, fl,      "~",         flo_rev,        MRB_ARGS_NONE());
   mrb_define_method(mrb, fl,      "&",         flo_and,        MRB_ARGS_REQ(1));
   mrb_define_method(mrb, fl,      "|",         flo_or,         MRB_ARGS_REQ(1));
@@ -1684,16 +1790,14 @@ mrb_init_numeric(mrb_state *mrb)
   mrb_define_method(mrb, fl,      "eql?",      flo_eql,        MRB_ARGS_REQ(1)); /* 15.2.8.3.16 */
 
   mrb_define_method(mrb, fl,      "to_s",      flo_to_s,       MRB_ARGS_NONE()); /* 15.2.9.3.16(x) */
-  mrb_define_method(mrb, fl,      "inspect",   flo_to_s,       MRB_ARGS_NONE());
+  mrb_define_method(mrb, fl,      "inspect",   flo_inspect,    MRB_ARGS_NONE());
   mrb_define_method(mrb, fl,      "nan?",      flo_nan_p,      MRB_ARGS_NONE());
 
 #ifdef INFINITY
-  mrb_define_const(mrb, fl, "INFINITY", mrb_float_value(mrb, INFINITY));
+  mrb_define_const_id(mrb, fl, MRB_SYM(INFINITY), mrb_float_value(mrb, INFINITY));
 #endif
 #ifdef NAN
-  mrb_define_const(mrb, fl, "NAN", mrb_float_value(mrb, NAN));
+  mrb_define_const_id(mrb, fl, MRB_SYM(NAN), mrb_float_value(mrb, NAN));
 #endif
-
-  mrb_include_module(mrb, fl, integral);
 #endif
 }
diff --git a/src/object.c b/src/object.c
index 7257f402d..aaab4022d 100644
--- a/src/object.c
+++ b/src/object.c
@@ -19,12 +19,12 @@ mrb_obj_eq(mrb_state *mrb, mrb_value v1, mrb_value v2)
     return TRUE;
 
   case MRB_TT_FALSE:
-  case MRB_TT_FIXNUM:
-    return (mrb_fixnum(v1) == mrb_fixnum(v2));
+  case MRB_TT_INTEGER:
+    return (mrb_integer(v1) == mrb_integer(v2));
   case MRB_TT_SYMBOL:
     return (mrb_symbol(v1) == mrb_symbol(v2));
 
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
   case MRB_TT_FLOAT:
     return (mrb_float(v1) == mrb_float(v2));
 #endif
@@ -47,18 +47,18 @@ mrb_equal(mrb_state *mrb, mrb_value obj1, mrb_value obj2)
   mrb_value result;
 
   if (mrb_obj_eq(mrb, obj1, obj2)) return TRUE;
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
   /* value mixing with integer and float */
-  if (mrb_fixnum_p(obj1)) {
-    if (mrb_float_p(obj2) && (mrb_float)mrb_fixnum(obj1) == mrb_float(obj2))
+  if (mrb_integer_p(obj1)) {
+    if (mrb_float_p(obj2) && (mrb_float)mrb_integer(obj1) == mrb_float(obj2))
       return TRUE;
   }
   else if (mrb_float_p(obj1)) {
-    if (mrb_fixnum_p(obj2) && mrb_float(obj1) == (mrb_float)mrb_fixnum(obj2))
+    if (mrb_integer_p(obj2) && mrb_float(obj1) == (mrb_float)mrb_integer(obj2))
       return TRUE;
   }
 #endif
-  result = mrb_funcall(mrb, obj1, "==", 1, obj2);
+  result = mrb_funcall_id(mrb, obj1, MRB_QSYM(eq), 1, obj2);
   if (mrb_test(result)) return TRUE;
   return FALSE;
 }
@@ -94,7 +94,7 @@ mrb_true(mrb_state *mrb, mrb_value obj)
 static mrb_value
 nil_to_s(mrb_state *mrb, mrb_value obj)
 {
-  mrb_value str = mrb_str_new_frozen(mrb, 0, 0);
+  mrb_value str = mrb_str_new_frozen(mrb, NULL, 0);
   RSTR_SET_ASCII_FLAG(mrb_str_ptr(str));
   return str;
 }
@@ -315,110 +315,115 @@ mrb_init_object(mrb_state *mrb)
   mrb_define_method(mrb, f, "inspect", false_to_s,  MRB_ARGS_NONE());
 }
 
-static mrb_value
-convert_type(mrb_state *mrb, mrb_value val, const char *tname, const char *method, mrb_bool raise)
+static const struct types {
+  const enum mrb_vtype type;
+  const char *name;
+} builtin_types[] = {
+/*    {MRB_TT_NIL,  "nil"}, */
+  {MRB_TT_FALSE,  "false"},
+  {MRB_TT_TRUE,   "true"},
+  {MRB_TT_INTEGER,"Integer"},
+  {MRB_TT_SYMBOL, "Symbol"},  /* :symbol */
+  {MRB_TT_MODULE, "Module"},
+  {MRB_TT_OBJECT, "Object"},
+  {MRB_TT_CLASS,  "Class"},
+  {MRB_TT_ICLASS, "iClass"},  /* internal use: mixed-in module holder */
+  {MRB_TT_SCLASS, "SClass"},
+  {MRB_TT_PROC,   "Proc"},
+#ifndef MRB_NO_FLOAT
+  {MRB_TT_FLOAT,  "Float"},
+#endif
+  {MRB_TT_ARRAY,  "Array"},
+  {MRB_TT_HASH,   "Hash"},
+  {MRB_TT_STRING, "String"},
+  {MRB_TT_RANGE,  "Range"},
+/*    {MRB_TT_BIGNUM,  "Bignum"}, */
+  {MRB_TT_DATA,   "Data"},  /* internal use: wrapped C pointers */
+/*    {MRB_TT_UNDEF,  "undef"}, */ /* internal use: #undef; should not happen */
+  {MRB_TT_MAXDEFINE,  0}
+};
+
+static const char*
+type_name(enum mrb_vtype t)
 {
-  mrb_sym m = 0;
+  const struct types *type = builtin_types;
+
+  while (type->type < MRB_TT_MAXDEFINE) {
+    if (type->type == t) return type->name;
+    type++;
+  }
+  return NULL;
+}
 
-  m = mrb_intern_cstr(mrb, method);
-  if (!mrb_respond_to(mrb, val, m)) {
+static mrb_value
+convert_type(mrb_state *mrb, mrb_value val, const char *tname, mrb_sym method, mrb_bool raise)
+{
+  if (!mrb_respond_to(mrb, val, method)) {
     if (raise) {
-      mrb_raisef(mrb, E_TYPE_ERROR, "can't convert %Y into %s", val, tname);
+      if (tname) mrb_raisef(mrb, E_TYPE_ERROR, "can't convert %Y into %s", val, tname);
+      mrb_raisef(mrb, E_TYPE_ERROR, "can't convert %Y", val);
     }
     return mrb_nil_value();
   }
-  return mrb_funcall_argv(mrb, val, m, 0, 0);
+  return mrb_funcall_argv(mrb, val, method, 0, 0);
 }
 
 MRB_API mrb_value
-mrb_convert_type(mrb_state *mrb, mrb_value val, enum mrb_vtype type, const char *tname, const char *method)
+mrb_type_convert(mrb_state *mrb, mrb_value val, enum mrb_vtype type, mrb_sym method)
 {
   mrb_value v;
+  const char *tname;
 
   if (mrb_type(val) == type) return val;
+  tname = type_name(type);
   v = convert_type(mrb, val, tname, method, TRUE);
   if (mrb_type(v) != type) {
     if (type == MRB_TT_STRING) return mrb_any_to_s(mrb, val);
-    mrb_raisef(mrb, E_TYPE_ERROR, "%v cannot be converted to %s by #%s", val, tname, method);
+    mrb_raisef(mrb, E_TYPE_ERROR, "%v cannot be converted to %s by #%n", val, tname, method);
   }
   return v;
 }
 
 MRB_API mrb_value
-mrb_check_convert_type(mrb_state *mrb, mrb_value val, enum mrb_vtype type, const char *tname, const char *method)
+mrb_type_convert_check(mrb_state *mrb, mrb_value val, enum mrb_vtype type, mrb_sym method)
 {
   mrb_value v;
 
   if (mrb_type(val) == type && type != MRB_TT_DATA && type != MRB_TT_ISTRUCT) return val;
-  v = convert_type(mrb, val, tname, method, FALSE);
+  v = convert_type(mrb, val, type_name(type), method, FALSE);
   if (mrb_nil_p(v) || mrb_type(v) != type) return mrb_nil_value();
   return v;
 }
 
-static const struct types {
-  unsigned char type;
-  const char *name;
-} builtin_types[] = {
-/*    {MRB_TT_NIL,  "nil"}, */
-  {MRB_TT_FALSE,  "false"},
-  {MRB_TT_TRUE,   "true"},
-  {MRB_TT_FIXNUM, "Fixnum"},
-  {MRB_TT_SYMBOL, "Symbol"},  /* :symbol */
-  {MRB_TT_MODULE, "Module"},
-  {MRB_TT_OBJECT, "Object"},
-  {MRB_TT_CLASS,  "Class"},
-  {MRB_TT_ICLASS, "iClass"},  /* internal use: mixed-in module holder */
-  {MRB_TT_SCLASS, "SClass"},
-  {MRB_TT_PROC,   "Proc"},
-#ifndef MRB_WITHOUT_FLOAT
-  {MRB_TT_FLOAT,  "Float"},
-#endif
-  {MRB_TT_ARRAY,  "Array"},
-  {MRB_TT_HASH,   "Hash"},
-  {MRB_TT_STRING, "String"},
-  {MRB_TT_RANGE,  "Range"},
-/*    {MRB_TT_BIGNUM,  "Bignum"}, */
-  {MRB_TT_DATA,   "Data"},  /* internal use: wrapped C pointers */
-/*    {MRB_TT_VARMAP,  "Varmap"}, */ /* internal use: dynamic variables */
-/*    {MRB_TT_NODE,  "Node"}, */ /* internal use: syntax tree node */
-/*    {MRB_TT_UNDEF,  "undef"}, */ /* internal use: #undef; should not happen */
-  {MRB_TT_MAXDEFINE,  0}
-};
-
 MRB_API void
 mrb_check_type(mrb_state *mrb, mrb_value x, enum mrb_vtype t)
 {
-  const struct types *type = builtin_types;
-  enum mrb_vtype xt;
-
-  xt = mrb_type(x);
-  if ((xt != t) || (xt == MRB_TT_DATA) || (xt == MRB_TT_ISTRUCT)) {
-    while (type->type < MRB_TT_MAXDEFINE) {
-      if (type->type == t) {
-        const char *etype;
-
-        if (mrb_nil_p(x)) {
-          etype = "nil";
-        }
-        else if (mrb_fixnum_p(x)) {
-          etype = "Fixnum";
-        }
-        else if (mrb_symbol_p(x)) {
-          etype = "Symbol";
-        }
-        else if (mrb_immediate_p(x)) {
-          etype = RSTRING_PTR(mrb_obj_as_string(mrb, x));
-        }
-        else {
-          etype = mrb_obj_classname(mrb, x);
-        }
-        mrb_raisef(mrb, E_TYPE_ERROR, "wrong argument type %s (expected %s)",
-                   etype, type->name);
-      }
-      type++;
-    }
-    mrb_raisef(mrb, E_TYPE_ERROR, "unknown type %d (%d given)", t, mrb_type(x));
+  enum mrb_vtype xt = mrb_type(x);
+  const char *tname, *ename;
+
+  if (t == xt) return;
+
+  tname = type_name(t);
+  if (mrb_nil_p(x)) {
+    ename = "nil";
+  }
+  else if (mrb_integer_p(x)) {
+    ename = "Fixnum";
+  }
+  else if (mrb_symbol_p(x)) {
+    ename = "Symbol";
+  }
+  else if (mrb_immediate_p(x)) {
+    ename = RSTRING_PTR(mrb_obj_as_string(mrb, x));
+  }
+  else {
+    ename = mrb_obj_classname(mrb, x);
+  }
+  if (tname) {
+    mrb_raisef(mrb, E_TYPE_ERROR, "wrong argument type %s (expected %s)",
+               ename, tname);
   }
+  mrb_raisef(mrb, E_TYPE_ERROR, "unknown type %d (%s given)", t, ename);
 }
 
 /* 15.3.1.3.46 */
@@ -504,8 +509,8 @@ MRB_API mrb_value
 mrb_to_int(mrb_state *mrb, mrb_value val)
 {
 
-  if (!mrb_fixnum_p(val)) {
-#ifndef MRB_WITHOUT_FLOAT
+  if (!mrb_integer_p(val)) {
+#ifndef MRB_NO_FLOAT
     if (mrb_float_p(val)) {
       return mrb_flo_to_fixnum(mrb, val);
     }
@@ -525,13 +530,13 @@ mrb_convert_to_integer(mrb_state *mrb, mrb_value val, mrb_int base)
     mrb_raise(mrb, E_TYPE_ERROR, "can't convert nil into Integer");
   }
   switch (mrb_type(val)) {
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
     case MRB_TT_FLOAT:
       if (base != 0) goto arg_error;
       return mrb_flo_to_fixnum(mrb, val);
 #endif
 
-    case MRB_TT_FIXNUM:
+    case MRB_TT_INTEGER:
       if (base != 0) goto arg_error;
       return val;
 
@@ -561,7 +566,7 @@ mrb_Integer(mrb_state *mrb, mrb_value val)
   return mrb_convert_to_integer(mrb, val, 0);
 }
 
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
 MRB_API mrb_value
 mrb_Float(mrb_state *mrb, mrb_value val)
 {
@@ -569,8 +574,8 @@ mrb_Float(mrb_state *mrb, mrb_value val)
     mrb_raise(mrb, E_TYPE_ERROR, "can't convert nil into Float");
   }
   switch (mrb_type(val)) {
-    case MRB_TT_FIXNUM:
-      return mrb_float_value(mrb, (mrb_float)mrb_fixnum(val));
+    case MRB_TT_INTEGER:
+      return mrb_float_value(mrb, (mrb_float)mrb_integer(val));
 
     case MRB_TT_FLOAT:
       return val;
@@ -579,7 +584,7 @@ mrb_Float(mrb_state *mrb, mrb_value val)
       return mrb_float_value(mrb, mrb_str_to_dbl(mrb, val, TRUE));
 
     default:
-      return mrb_convert_type(mrb, val, MRB_TT_FLOAT, "Float", "to_f");
+      return mrb_type_convert(mrb, val, MRB_TT_FLOAT, MRB_SYM(to_f));
   }
 }
 #endif
@@ -648,12 +653,12 @@ mrb_check_hash_type(mrb_state *mrb, mrb_value hash)
 MRB_API mrb_value
 mrb_inspect(mrb_state *mrb, mrb_value obj)
 {
-  return mrb_obj_as_string(mrb, mrb_funcall(mrb, obj, "inspect", 0));
+  return mrb_obj_as_string(mrb, mrb_funcall_id(mrb, obj, MRB_SYM(inspect), 0));
 }
 
 MRB_API mrb_bool
 mrb_eql(mrb_state *mrb, mrb_value obj1, mrb_value obj2)
 {
   if (mrb_obj_eq(mrb, obj1, obj2)) return TRUE;
-  return mrb_test(mrb_funcall(mrb, obj1, "eql?", 1, obj2));
+  return mrb_test(mrb_funcall_id(mrb, obj1, MRB_QSYM(eql_p), 1, obj2));
 }
diff --git a/src/print.c b/src/print.c
index a75814d81..6bf7da6a5 100644
--- a/src/print.c
+++ b/src/print.c
@@ -60,11 +60,11 @@ mrb_print_error(mrb_state *mrb)
 MRB_API void
 mrb_show_version(mrb_state *mrb)
 {
-  printstr(mrb_const_get(mrb, mrb_obj_value(mrb->object_class), mrb_intern_lit(mrb, "MRUBY_DESCRIPTION")), stdout);
+  printstr(mrb_const_get(mrb, mrb_obj_value(mrb->object_class), MRB_SYM(MRUBY_DESCRIPTION)), stdout);
 }
 
 MRB_API void
 mrb_show_copyright(mrb_state *mrb)
 {
-  printstr(mrb_const_get(mrb, mrb_obj_value(mrb->object_class), mrb_intern_lit(mrb, "MRUBY_COPYRIGHT")), stdout);
+  printstr(mrb_const_get(mrb, mrb_obj_value(mrb->object_class), MRB_SYM(MRUBY_COPYRIGHT)), stdout);
 }
diff --git a/src/proc.c b/src/proc.c
index c00b09acf..b971b6520 100644
--- a/src/proc.c
+++ b/src/proc.c
@@ -14,8 +14,26 @@ static const mrb_code call_iseq[] = {
   OP_CALL,
 };
 
+static const mrb_irep call_irep = {
+  0,                                   /* nlocals */
+  2,                                   /* nregs */
+  0,                                   /* clen */
+  MRB_ISEQ_NO_FREE | MRB_IREP_NO_FREE, /* flags */
+  call_iseq,                           /* iseq */
+  NULL,                                /* pool */
+  NULL,                                /* syms */
+  NULL,                                /* reps */
+  NULL,                                /* lv */
+  NULL,                                /* debug_info */
+  1,                                   /* ilen */
+  0,                                   /* plen */
+  0,                                   /* slen */
+  1,                                   /* rlen */
+  0,                                   /* refcnt */
+};
+
 struct RProc*
-mrb_proc_new(mrb_state *mrb, mrb_irep *irep)
+mrb_proc_new(mrb_state *mrb, const mrb_irep *irep)
 {
   struct RProc *p;
   mrb_callinfo *ci = mrb->c->ci;
@@ -34,7 +52,7 @@ mrb_proc_new(mrb_state *mrb, mrb_irep *irep)
     p->e.target_class = tc;
   }
   p->body.irep = irep;
-  mrb_irep_incref(mrb, irep);
+  mrb_irep_incref(mrb, (mrb_irep*)irep);
 
   return p;
 }
@@ -44,7 +62,7 @@ env_new(mrb_state *mrb, mrb_int nlocals)
 {
   struct REnv *e;
   mrb_callinfo *ci = mrb->c->ci;
-  int bidx;
+  mrb_int bidx;
 
   e = (struct REnv*)mrb_obj_alloc(mrb, MRB_TT_ENV, NULL);
   MRB_ENV_SET_LEN(e, nlocals);
@@ -63,7 +81,7 @@ static void
 closure_setup(mrb_state *mrb, struct RProc *p)
 {
   mrb_callinfo *ci = mrb->c->ci;
-  struct RProc *up = p->upper;
+  const struct RProc *up = p->upper;
   struct REnv *e = NULL;
 
   if (ci && ci->env) {
@@ -90,7 +108,7 @@ closure_setup(mrb_state *mrb, struct RProc *p)
 }
 
 struct RProc*
-mrb_closure_new(mrb_state *mrb, mrb_irep *irep)
+mrb_closure_new(mrb_state *mrb, const mrb_irep *irep)
 {
   struct RProc *p = mrb_proc_new(mrb, irep);
 
@@ -153,7 +171,7 @@ mrb_closure_new_cfunc(mrb_state *mrb, mrb_func_t func, int nlocals)
 MRB_API mrb_value
 mrb_proc_cfunc_env_get(mrb_state *mrb, mrb_int idx)
 {
-  struct RProc *p = mrb->c->ci->proc;
+  const struct RProc *p = mrb->c->ci->proc;
   struct REnv *e;
 
   if (!p || !MRB_PROC_CFUNC_P(p)) {
@@ -181,7 +199,7 @@ mrb_proc_copy(struct RProc *a, struct RProc *b)
   a->flags = b->flags;
   a->body = b->body;
   if (!MRB_PROC_CFUNC_P(a) && a->body.irep) {
-    a->body.irep->refcnt++;
+    mrb_irep_incref(NULL, (mrb_irep*)a->body.irep);
   }
   a->upper = b->upper;
   a->e.env = b->e.env;
@@ -200,7 +218,7 @@ mrb_proc_s_new(mrb_state *mrb, mrb_value proc_class)
   p = (struct RProc *)mrb_obj_alloc(mrb, MRB_TT_PROC, mrb_class_ptr(proc_class));
   mrb_proc_copy(p, mrb_proc_ptr(blk));
   proc = mrb_obj_value(p);
-  mrb_funcall_with_block(mrb, proc, mrb_intern_lit(mrb, "initialize"), 0, NULL, proc);
+  mrb_funcall_with_block(mrb, proc, MRB_SYM(initialize), 0, NULL, proc);
   if (!MRB_PROC_STRICT_P(p) &&
       mrb->c->ci > mrb->c->cibase && MRB_PROC_ENV(p) == mrb->c->ci[-1].env) {
     p->flags |= MRB_PROC_ORPHAN;
@@ -224,7 +242,7 @@ mrb_proc_init_copy(mrb_state *mrb, mrb_value self)
 static mrb_value
 proc_arity(mrb_state *mrb, mrb_value self)
 {
-  return mrb_fixnum_value(mrb_proc_arity(mrb_proc_ptr(self)));
+  return mrb_int_value(mrb, mrb_proc_arity(mrb_proc_ptr(self)));
 }
 
 /* 15.3.1.2.6  */
@@ -262,7 +280,7 @@ proc_lambda(mrb_state *mrb, mrb_value self)
 mrb_int
 mrb_proc_arity(const struct RProc *p)
 {
-  struct mrb_irep *irep;
+  const mrb_irep *irep;
   const mrb_code *pc;
   mrb_aspec aspec;
   int ma, op, ra, pa, arity;
@@ -293,40 +311,20 @@ mrb_proc_arity(const struct RProc *p)
   return arity;
 }
 
-static void
-tempirep_free(mrb_state *mrb, void *p)
-{
-  if (p) mrb_irep_free(mrb, (mrb_irep *)p);
-}
-
-static const mrb_data_type tempirep_type = { "temporary irep", tempirep_free };
-
 void
 mrb_init_proc(mrb_state *mrb)
 {
   struct RProc *p;
   mrb_method_t m;
-  struct RData *irep_obj = mrb_data_object_alloc(mrb, mrb->object_class, NULL, &tempirep_type);
-  mrb_irep *call_irep;
-  static const mrb_irep mrb_irep_zero = { 0 };
-
-  call_irep = (mrb_irep *)mrb_malloc(mrb, sizeof(mrb_irep));
-  irep_obj->data = call_irep;
-  *call_irep = mrb_irep_zero;
-  call_irep->flags = MRB_ISEQ_NO_FREE;
-  call_irep->iseq = call_iseq;
-  call_irep->ilen = 1;
-  call_irep->nregs = 2;         /* receiver and block */
 
   mrb_define_class_method(mrb, mrb->proc_class, "new", mrb_proc_s_new, MRB_ARGS_NONE()|MRB_ARGS_BLOCK());
   mrb_define_method(mrb, mrb->proc_class, "initialize_copy", mrb_proc_init_copy, MRB_ARGS_REQ(1));
   mrb_define_method(mrb, mrb->proc_class, "arity", proc_arity, MRB_ARGS_NONE());
 
-  p = mrb_proc_new(mrb, call_irep);
-  irep_obj->data = NULL;
+  p = mrb_proc_new(mrb, &call_irep);
   MRB_METHOD_FROM_PROC(m, p);
-  mrb_define_method_raw(mrb, mrb->proc_class, mrb_intern_lit(mrb, "call"), m);
-  mrb_define_method_raw(mrb, mrb->proc_class, mrb_intern_lit(mrb, "[]"), m);
+  mrb_define_method_raw(mrb, mrb->proc_class, MRB_SYM(call), m);
+  mrb_define_method_raw(mrb, mrb->proc_class, MRB_QSYM(aref), m);
 
   mrb_define_class_method(mrb, mrb->kernel_module, "lambda", proc_lambda, MRB_ARGS_NONE()|MRB_ARGS_BLOCK()); /* 15.3.1.2.6  */
   mrb_define_method(mrb, mrb->kernel_module,       "lambda", proc_lambda, MRB_ARGS_NONE()|MRB_ARGS_BLOCK()); /* 15.3.1.3.27 */
diff --git a/src/range.c b/src/range.c
index 0b4e6dbca..c06a8a00b 100644
--- a/src/range.c
+++ b/src/range.c
@@ -23,11 +23,11 @@ r_check(mrb_state *mrb, mrb_value a, mrb_value b)
 
   ta = mrb_type(a);
   tb = mrb_type(b);
-#ifdef MRB_WITHOUT_FLOAT
-  if (ta == MRB_TT_FIXNUM && tb == MRB_TT_FIXNUM ) {
+#ifdef MRB_NO_FLOAT
+  if (ta == MRB_TT_INTEGER && tb == MRB_TT_INTEGER ) {
 #else
-  if ((ta == MRB_TT_FIXNUM || ta == MRB_TT_FLOAT) &&
-      (tb == MRB_TT_FIXNUM || tb == MRB_TT_FLOAT)) {
+  if ((ta == MRB_TT_INTEGER || ta == MRB_TT_FLOAT) &&
+      (tb == MRB_TT_INTEGER || tb == MRB_TT_FLOAT)) {
 #endif
     return;
   }
@@ -78,7 +78,7 @@ range_ptr_init(mrb_state *mrb, struct RRange *r, mrb_value beg, mrb_value end, m
   if (r) {
     if (RANGE_INITIALIZED_P(r)) {
       /* Ranges are immutable, so that they should be initialized only once. */
-      mrb_name_error(mrb, mrb_intern_lit(mrb, "initialize"), "'initialize' called twice");
+      mrb_name_error(mrb, MRB_SYM(initialize), "'initialize' called twice");
     }
     else {
       range_ptr_alloc_edges(mrb, r);
@@ -328,8 +328,8 @@ mrb_get_values_at(mrb_state *mrb, mrb_value obj, mrb_int olen, mrb_int argc, con
   result = mrb_ary_new(mrb);
 
   for (i = 0; i < argc; ++i) {
-    if (mrb_fixnum_p(argv[i])) {
-      mrb_ary_push(mrb, result, func(mrb, obj, mrb_fixnum(argv[i])));
+    if (mrb_integer_p(argv[i])) {
+      mrb_ary_push(mrb, result, func(mrb, obj, mrb_integer(argv[i])));
     }
     else if (mrb_range_beg_len(mrb, argv[i], &beg, &len, olen, FALSE) == MRB_RANGE_OK) {
       mrb_int const end = olen < beg + len ? olen : beg + len;
diff --git a/src/state.c b/src/state.c
index 790f7ca13..1f85448a1 100644
--- a/src/state.c
+++ b/src/state.c
@@ -107,12 +107,14 @@ void mrb_free_symtbl(mrb_state *mrb);
 void
 mrb_irep_incref(mrb_state *mrb, mrb_irep *irep)
 {
+  if (irep->flags & MRB_IREP_NO_FREE) return;
   irep->refcnt++;
 }
 
 void
 mrb_irep_decref(mrb_state *mrb, mrb_irep *irep)
 {
+  if (irep->flags & MRB_IREP_NO_FREE) return;
   irep->refcnt--;
   if (irep->refcnt == 0) {
     mrb_irep_free(mrb, irep);
@@ -122,12 +124,14 @@ mrb_irep_decref(mrb_state *mrb, mrb_irep *irep)
 void
 mrb_irep_cutref(mrb_state *mrb, mrb_irep *irep)
 {
-  mrb_irep *tmp;
+  mrb_irep **reps;
   int i;
 
+  if (irep->flags & MRB_IREP_NO_FREE) return;
+  reps = (mrb_irep**)irep->reps;
   for (i=0; i<irep->rlen; i++) {
-    tmp = irep->reps[i];
-    irep->reps[i] = NULL;
+    mrb_irep *tmp = reps[i];
+    reps[i] = NULL;
     if (tmp) mrb_irep_decref(mrb, tmp);
   }
 }
@@ -137,29 +141,26 @@ mrb_irep_free(mrb_state *mrb, mrb_irep *irep)
 {
   int i;
 
+  if (irep->flags & MRB_IREP_NO_FREE) return;
   if (!(irep->flags & MRB_ISEQ_NO_FREE))
     mrb_free(mrb, (void*)irep->iseq);
-  if (irep->pool) for (i=0; i<irep->plen; i++) {
-    if (mrb_string_p(irep->pool[i])) {
-      mrb_gc_free_str(mrb, RSTRING(irep->pool[i]));
-      mrb_free(mrb, mrb_obj_ptr(irep->pool[i]));
+  if (irep->pool) {
+    for (i=0; i<irep->plen; i++) {
+      if ((irep->pool[i].tt & 3) == IREP_TT_STR) {
+        mrb_free(mrb, (void*)irep->pool[i].u.str);
+      }
     }
-#if defined(MRB_WORD_BOXING) && !defined(MRB_WITHOUT_FLOAT)
-    else if (mrb_float_p(irep->pool[i])) {
-      mrb_free(mrb, mrb_obj_ptr(irep->pool[i]));
-    }
-#endif
+    mrb_free(mrb, (void*)irep->pool);
   }
-  mrb_free(mrb, irep->pool);
-  mrb_free(mrb, irep->syms);
+  mrb_free(mrb, (void*)irep->syms);
   if (irep->reps) {
     for (i=0; i<irep->rlen; i++) {
       if (irep->reps[i])
-        mrb_irep_decref(mrb, irep->reps[i]);
+        mrb_irep_decref(mrb, (mrb_irep*)irep->reps[i]);
     }
+    mrb_free(mrb, (void*)irep->reps);
   }
-  mrb_free(mrb, irep->reps);
-  mrb_free(mrb, irep->lv);
+  mrb_free(mrb, (void*)irep->lv);
   mrb_debug_info_free(mrb, irep->debug_info);
   mrb_free(mrb, irep);
 }
@@ -170,8 +171,6 @@ mrb_free_context(mrb_state *mrb, struct mrb_context *c)
   if (!c) return;
   mrb_free(mrb, c->stbase);
   mrb_free(mrb, c->cibase);
-  mrb_free(mrb, c->rescue);
-  mrb_free(mrb, c->ensure);
   mrb_free(mrb, c);
 }
 
diff --git a/src/string.c b/src/string.c
index c83e791b6..f27145296 100644
--- a/src/string.c
+++ b/src/string.c
@@ -8,7 +8,7 @@
 # define _CRT_NONSTDC_NO_DEPRECATE
 #endif
 
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
 #include <float.h>
 #include <math.h>
 #endif
@@ -583,9 +583,6 @@ str_share(mrb_state *mrb, struct RString *orig, struct RString *s)
   else if (RSTR_FSHARED_P(orig)) {
     str_init_fshared(orig, s, orig->as.heap.aux.fshared);
   }
-  else if (mrb_frozen_p(orig) && !RSTR_POOL_P(orig)) {
-    str_init_fshared(orig, s, orig);
-  }
   else {
     if (orig->as.heap.aux.capa > orig->as.heap.len) {
       orig->as.heap.ptr = (char *)mrb_realloc(mrb, orig->as.heap.ptr, len+1);
@@ -597,29 +594,6 @@ str_share(mrb_state *mrb, struct RString *orig, struct RString *s)
 }
 
 mrb_value
-mrb_str_pool(mrb_state *mrb, const char *p, mrb_int len, mrb_bool nofree)
-{
-  struct RString *s = (struct RString *)mrb_malloc(mrb, sizeof(struct RString));
-
-  s->tt = MRB_TT_STRING;
-  s->c = mrb->string_class;
-  s->flags = 0;
-
-  if (RSTR_EMBEDDABLE_P(len)) {
-    str_init_embed(s, p, len);
-  }
-  else if (nofree) {
-    str_init_nofree(s, p, len);
-  }
-  else {
-    str_init_normal(mrb, s, p, len);
-  }
-  RSTR_SET_POOL_FLAG(s);
-  MRB_SET_FROZEN_FLAG(s);
-  return mrb_obj_value(s);
-}
-
-mrb_value
 mrb_str_byte_subseq(mrb_state *mrb, mrb_value str, mrb_int beg, mrb_int len)
 {
   struct RString *orig, *s;
@@ -898,7 +872,7 @@ mrb_str_to_cstr(mrb_state *mrb, mrb_value str0)
 MRB_API void
 mrb_str_concat(mrb_state *mrb, mrb_value self, mrb_value other)
 {
-  other = mrb_str_to_str(mrb, other);
+  other = mrb_obj_as_string(mrb, other);
   mrb_str_cat_str(mrb, self, other);
 }
 
@@ -1111,30 +1085,11 @@ mrb_str_equal_m(mrb_state *mrb, mrb_value str1)
 }
 /* ---------------------------------- */
 
-MRB_API mrb_value
-mrb_str_to_str(mrb_state *mrb, mrb_value str)
-{
-  switch (mrb_type(str)) {
-  case MRB_TT_STRING:
-    return str;
-  case MRB_TT_SYMBOL:
-    return mrb_sym_str(mrb, mrb_symbol(str));
-  case MRB_TT_FIXNUM:
-    return mrb_fixnum_to_str(mrb, str, 10);
-  case MRB_TT_SCLASS:
-  case MRB_TT_CLASS:
-  case MRB_TT_MODULE:
-    return mrb_mod_to_s(mrb, str);
-  default:
-    return mrb_convert_type(mrb, str, MRB_TT_STRING, "String", "to_s");
-  }
-}
-
 /* obslete: use RSTRING_PTR() */
 MRB_API const char*
 mrb_string_value_ptr(mrb_state *mrb, mrb_value str)
 {
-  str = mrb_str_to_str(mrb, str);
+  str = mrb_obj_as_string(mrb, str);
   return RSTRING_PTR(str);
 }
 
@@ -1180,8 +1135,8 @@ str_convert_range(mrb_state *mrb, mrb_value str, mrb_value indx, mrb_value alen,
   }
   else {
     switch (mrb_type(indx)) {
-      case MRB_TT_FIXNUM:
-        *beg = mrb_fixnum(indx);
+      case MRB_TT_INTEGER:
+        *beg = mrb_integer(indx);
         *len = 1;
         return STR_CHAR_RANGE;
 
@@ -1196,8 +1151,8 @@ str_convert_range(mrb_state *mrb, mrb_value str, mrb_value indx, mrb_value alen,
 
       default:
         indx = mrb_to_int(mrb, indx);
-        if (mrb_fixnum_p(indx)) {
-          *beg = mrb_fixnum(indx);
+        if (mrb_integer_p(indx)) {
+          *beg = mrb_integer(indx);
           *len = 1;
           return STR_CHAR_RANGE;
         }
@@ -1212,7 +1167,7 @@ range_arg:
             break;
         }
 
-        mrb_raise(mrb, E_TYPE_ERROR, "can't convert to Fixnum");
+        mrb_raise(mrb, E_TYPE_ERROR, "can't convert to Integer");
     }
   }
   return STR_OUT_OF_RANGE;
@@ -1256,8 +1211,8 @@ mrb_str_aref(mrb_state *mrb, mrb_value str, mrb_value indx, mrb_value alen)
  *     str.slice(range)            => new_str or nil
  *     str.slice(other_str)        => new_str or nil
  *
- *  Element Reference---If passed a single <code>Fixnum</code>, returns the code
- *  of the character at that position. If passed two <code>Fixnum</code>
+ *  Element Reference---If passed a single <code>Integer</code>, returns the code
+ *  of the character at that position. If passed two <code>Integer</code>
  *  objects, returns a substring starting at the offset given by the first, and
  *  a length given by the second. If given a range, a substring containing
  *  characters at offsets given by the range is returned. In all three cases, if
@@ -1963,7 +1918,20 @@ mrb_str_intern(mrb_state *mrb, mrb_value self)
 MRB_API mrb_value
 mrb_obj_as_string(mrb_state *mrb, mrb_value obj)
 {
-  return mrb_str_to_str(mrb, obj);
+  switch (mrb_type(obj)) {
+  case MRB_TT_STRING:
+    return obj;
+  case MRB_TT_SYMBOL:
+    return mrb_sym_str(mrb, mrb_symbol(obj));
+  case MRB_TT_INTEGER:
+    return mrb_fixnum_to_str(mrb, obj, 10);
+  case MRB_TT_SCLASS:
+  case MRB_TT_CLASS:
+  case MRB_TT_MODULE:
+    return mrb_mod_to_s(mrb, obj);
+  default:
+    return mrb_type_convert(mrb, obj, MRB_TT_STRING, MRB_SYM(to_s));
+  }
 }
 
 MRB_API mrb_value
@@ -2391,7 +2359,7 @@ mrb_str_len_to_inum(mrb_state *mrb, const char *str, size_t len, mrb_int base, i
     n *= base;
     n += c;
     if (n > (uint64_t)MRB_INT_MAX + (sign ? 0 : 1)) {
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
       if (base == 10) {
         return mrb_float_value(mrb, mrb_str_to_dbl(mrb, mrb_str_new(mrb, str, len), badcheck));
       }
@@ -2502,7 +2470,7 @@ mrb_str_to_i(mrb_state *mrb, mrb_value self)
   return mrb_str_to_inum(mrb, self, base, FALSE);
 }
 
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
 double
 mrb_str_len_to_dbl(mrb_state *mrb, const char *s, size_t len, mrb_bool badcheck)
 {
@@ -2524,8 +2492,8 @@ mrb_str_len_to_dbl(mrb_state *mrb, const char *s, size_t len, mrb_bool badcheck)
 
     if (!badcheck) return 0.0;
     x = mrb_str_len_to_inum(mrb, p, pend-p, 0, badcheck);
-    if (mrb_fixnum_p(x))
-      d = (double)mrb_fixnum(x);
+    if (mrb_integer_p(x))
+      d = (double)mrb_integer(x);
     else /* if (mrb_float_p(x)) */
       d = mrb_float(x);
     return d;
@@ -2900,7 +2868,7 @@ mrb_str_byteslice(mrb_state *mrb, mrb_value str)
       }
     }
     else {
-      beg = mrb_fixnum(mrb_to_int(mrb, a1));
+      beg = mrb_integer(mrb_to_int(mrb, a1));
       len = 1;
       empty = FALSE;
     }
@@ -2963,7 +2931,7 @@ mrb_init_string(mrb_state *mrb)
   mrb_define_method(mrb, s, "slice",           mrb_str_aref_m,          MRB_ARGS_ANY());  /* 15.2.10.5.34 */
   mrb_define_method(mrb, s, "split",           mrb_str_split_m,         MRB_ARGS_ANY());  /* 15.2.10.5.35 */
 
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
   mrb_define_method(mrb, s, "to_f",            mrb_str_to_f,            MRB_ARGS_NONE()); /* 15.2.10.5.38 */
 #endif
   mrb_define_method(mrb, s, "to_i",            mrb_str_to_i,            MRB_ARGS_ANY());  /* 15.2.10.5.39 */
@@ -2980,7 +2948,7 @@ mrb_init_string(mrb_state *mrb)
   mrb_define_method(mrb, s, "byteslice",       mrb_str_byteslice,       MRB_ARGS_ARG(1,1));
 }
 
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
 /*
  * Source code for the "strtod" library procedure.
  *
diff --git a/src/symbol.c b/src/symbol.c
index 992848797..add093d14 100644
--- a/src/symbol.c
+++ b/src/symbol.c
@@ -12,6 +12,59 @@
 #include <mruby/dump.h>
 #include <mruby/class.h>
 
+#undef MRB_PRESYM_MAX
+#undef MRB_PRESYM_CSYM
+#undef MRB_PRESYM_QSYM
+#undef MRB_PRESYM_SYM
+#define MRB_PRESYM_CSYM(sym, num) {#sym,sizeof(#sym)-1},
+#define MRB_PRESYM_QSYM(str, name, num) {str,sizeof(str)-1},
+#define MRB_PRESYM_SYM(str, num) {str,sizeof(str)-1},
+
+static const struct {
+  const char *name;
+  uint16_t len;
+} presym_table[] = {
+#include <../build/presym.inc>
+  {0,0}
+};
+
+static mrb_sym
+presym_find(const char *name, size_t len)
+{
+  int start = 0;
+  int end = MRB_PRESYM_MAX-1;
+
+  while (start<=end) {
+    int mid = (start+end)/2;
+    size_t plen = presym_table[mid].len;
+    size_t tlen = (plen > len) ? len : plen;
+    int cmp;
+
+    cmp = memcmp(name, presym_table[mid].name, tlen);
+    if (cmp == 0) {
+      if (len > plen) cmp = 1;
+      else if (len < plen) cmp = -1;
+    }
+
+    if (cmp == 0) {
+      return mid+1;
+    } else if (cmp > 0) {
+      start = mid+1;
+    } else {
+      end = mid-1;
+    }
+  }
+  return 0;
+}
+
+static const char*
+presym_sym2name(mrb_sym sym, mrb_int *lenp)
+{
+  if (sym > MRB_PRESYM_MAX) return NULL;
+  if (lenp) *lenp = presym_table[sym-1].len;
+  return presym_table[sym-1].name;
+}
+
 /* ------------------------------------------------------ */
 typedef struct symbol_name {
   mrb_bool lit : 1;
@@ -20,20 +73,15 @@ typedef struct symbol_name {
   const char *name;
 } symbol_name;
 
-#define SYMBOL_INLINE_BIT_POS       1
-#define SYMBOL_INLINE_LOWER_BIT_POS 2
-#define SYMBOL_INLINE               (1 << (SYMBOL_INLINE_BIT_POS - 1))
-#define SYMBOL_INLINE_LOWER         (1 << (SYMBOL_INLINE_LOWER_BIT_POS - 1))
-#define SYMBOL_NORMAL_SHIFT         SYMBOL_INLINE_BIT_POS
-#define SYMBOL_INLINE_SHIFT         SYMBOL_INLINE_LOWER_BIT_POS
 #ifdef MRB_ENABLE_ALL_SYMBOLS
+#define SYMBOL_SHIFT         0
 # define SYMBOL_INLINE_P(sym) FALSE
-# define SYMBOL_INLINE_LOWER_P(sym) FALSE
 # define sym_inline_pack(name, len) 0
 # define sym_inline_unpack(sym, buf, lenp) NULL
 #else
+#define SYMBOL_INLINE        1
+#define SYMBOL_SHIFT         1
 # define SYMBOL_INLINE_P(sym) ((sym) & SYMBOL_INLINE)
-# define SYMBOL_INLINE_LOWER_P(sym) ((sym) & SYMBOL_INLINE_LOWER)
 #endif
 
 static void
@@ -50,16 +98,14 @@ static const char pack_table[] = "_abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRS
 static mrb_sym
 sym_inline_pack(const char *name, size_t len)
 {
-  const size_t lower_length_max = (MRB_SYMBOL_BIT - 2) / 5;
-  const size_t mix_length_max   = (MRB_SYMBOL_BIT - 2) / 6;
+  const size_t pack_length_max   = (MRB_SYMBOL_BIT - 2) / 6;
 
   char c;
   const char *p;
   size_t i;
   mrb_sym sym = 0;
-  mrb_bool lower = TRUE;
 
-  if (len > lower_length_max) return 0; /* too long */
+  if (len > pack_length_max) return 0; /* too long */
   for (i=0; i<len; i++) {
     uint32_t bits;
 
@@ -68,36 +114,21 @@ sym_inline_pack(const char *name, size_t len)
     p = strchr(pack_table, (int)c);
     if (p == 0) return 0;       /* non alnum char */
     bits = (uint32_t)(p - pack_table)+1;
-    if (bits > 27) lower = FALSE;
-    if (i >= mix_length_max) break;
-    sym |= bits<<(i*6+SYMBOL_INLINE_SHIFT);
+    if (i >= pack_length_max) break;
+    sym |= bits<<(i*6+SYMBOL_SHIFT);
   }
-  if (lower) {
-    sym = 0;
-    for (i=0; i<len; i++) {
-      uint32_t bits;
-
-      c = name[i];
-      p = strchr(pack_table, (int)c);
-      bits = (uint32_t)(p - pack_table)+1;
-      sym |= bits<<(i*5+SYMBOL_INLINE_SHIFT);
-    }
-    return sym | SYMBOL_INLINE | SYMBOL_INLINE_LOWER;
-  }
-  if (len > mix_length_max) return 0;
   return sym | SYMBOL_INLINE;
 }
 
 static const char*
 sym_inline_unpack(mrb_sym sym, char *buf, mrb_int *lenp)
 {
-  int bit_per_char = SYMBOL_INLINE_LOWER_P(sym) ? 5 : 6;
   int i;
 
   mrb_assert(SYMBOL_INLINE_P(sym));
 
-  for (i=0; i<30/bit_per_char; i++) {
-    uint32_t bits = sym>>(i*bit_per_char+SYMBOL_INLINE_SHIFT) & ((1<<bit_per_char)-1);
+  for (i=0; i<5; i++) {
+    uint32_t bits = sym>>(i*6+SYMBOL_SHIFT) & ((1<<6)-1);
     if (bits == 0) break;
     buf[i] = pack_table[bits-1];;
   }
@@ -130,6 +161,10 @@ find_symbol(mrb_state *mrb, const char *name, size_t len, uint8_t *hashp)
   symbol_name *sname;
   uint8_t hash;
 
+  /* presym */
+  i = presym_find(name, len);
+  if (i > 0) return i<<SYMBOL_SHIFT;
+
   /* inline symbol */
   i = sym_inline_pack(name, len);
   if (i > 0) return i;
@@ -142,14 +177,14 @@ find_symbol(mrb_state *mrb, const char *name, size_t len, uint8_t *hashp)
   do {
     sname = &mrb->symtbl[i];
     if (sname->len == len && memcmp(sname->name, name, len) == 0) {
-      return i<<SYMBOL_NORMAL_SHIFT;
+      return (i+MRB_PRESYM_MAX)<<SYMBOL_SHIFT;
     }
     if (sname->prev == 0xff) {
       i -= 0xff;
       sname = &mrb->symtbl[i];
       while (mrb->symtbl < sname) {
         if (sname->len == len && memcmp(sname->name, name, len) == 0) {
-          return (mrb_sym)(sname - mrb->symtbl)<<SYMBOL_NORMAL_SHIFT;
+          return (mrb_sym)(sname - mrb->symtbl)<<SYMBOL_SHIFT;
         }
         sname--;
       }
@@ -205,7 +240,7 @@ sym_intern(mrb_state *mrb, const char *name, size_t len, mrb_bool lit)
   }
   mrb->symhash[hash] = mrb->symidx = sym;
 
-  return sym<<SYMBOL_NORMAL_SHIFT;
+  return (sym+MRB_PRESYM_MAX)<<SYMBOL_SHIFT;
 }
 
 MRB_API mrb_sym
@@ -232,27 +267,51 @@ mrb_intern_str(mrb_state *mrb, mrb_value str)
   return mrb_intern(mrb, RSTRING_PTR(str), RSTRING_LEN(str));
 }
 
-MRB_API mrb_value
-mrb_check_intern(mrb_state *mrb, const char *name, size_t len)
+MRB_API mrb_sym
+mrb_intern_check(mrb_state *mrb, const char *name, size_t len)
 {
   mrb_sym sym;
 
   sym_validate_len(mrb, len);
   sym = find_symbol(mrb, name, len, NULL);
-  if (sym > 0) return mrb_symbol_value(sym);
-  return mrb_nil_value();
+  if (sym > 0) return sym;
+  return 0;
+}
+
+MRB_API mrb_value
+mrb_check_intern(mrb_state *mrb, const char *name, size_t len)
+{
+  mrb_sym sym = mrb_intern_check(mrb, name, len);
+  if (sym == 0) return mrb_nil_value();
+  return mrb_symbol_value(sym);
+}
+
+MRB_API mrb_sym
+mrb_intern_check_cstr(mrb_state *mrb, const char *name)
+{
+  return mrb_intern_check(mrb, name, strlen(name));
 }
 
 MRB_API mrb_value
 mrb_check_intern_cstr(mrb_state *mrb, const char *name)
 {
-  return mrb_check_intern(mrb, name, strlen(name));
+  mrb_sym sym = mrb_intern_check_cstr(mrb, name);
+  if (sym == 0) return mrb_nil_value();
+  return mrb_symbol_value(sym);
+}
+
+MRB_API mrb_sym
+mrb_intern_check_str(mrb_state *mrb, mrb_value str)
+{
+  return mrb_intern_check(mrb, RSTRING_PTR(str), RSTRING_LEN(str));
 }
 
 MRB_API mrb_value
 mrb_check_intern_str(mrb_state *mrb, mrb_value str)
 {
-  return mrb_check_intern(mrb, RSTRING_PTR(str), RSTRING_LEN(str));
+  mrb_sym sym = mrb_intern_check_str(mrb, str);
+  if (sym == 0) return mrb_nil_value();
+  return mrb_symbol_value(sym);
 }
 
 static const char*
@@ -260,7 +319,13 @@ sym2name_len(mrb_state *mrb, mrb_sym sym, char *buf, mrb_int *lenp)
 {
   if (SYMBOL_INLINE_P(sym)) return sym_inline_unpack(sym, buf, lenp);
 
-  sym >>= SYMBOL_NORMAL_SHIFT;
+  sym >>= SYMBOL_SHIFT;
+  {
+    const char *name = presym_sym2name(sym, lenp);
+    if (name) return name;
+  }
+  sym -= MRB_PRESYM_MAX;
+  
   if (sym == 0 || mrb->symidx < sym) {
     if (lenp) *lenp = 0;
     return NULL;
@@ -276,6 +341,15 @@ mrb_sym_name_len(mrb_state *mrb, mrb_sym sym, mrb_int *lenp)
   return sym2name_len(mrb, sym, mrb->symbuf, lenp);
 }
 
+mrb_bool
+mrb_sym_static_p(mrb_state *mrb, mrb_sym sym)
+{
+  if (SYMBOL_INLINE_P(sym)) return TRUE;
+  sym >>= SYMBOL_SHIFT;
+  if (sym > MRB_PRESYM_MAX) return FALSE;
+  return TRUE;
+}
+
 void
 mrb_free_symtbl(mrb_state *mrb)
 {
@@ -497,7 +571,7 @@ sym_inspect(mrb_state *mrb, mrb_value sym)
   char *sp;
 
   name = mrb_sym_name_len(mrb, id, &len);
-  str = mrb_str_new(mrb, 0, len+1);
+  str = mrb_str_new(mrb, NULL, len+1);
   sp = RSTRING_PTR(str);
   sp[0] = ':';
   memcpy(sp+1, name, len);
diff --git a/src/value_array.h b/src/value_array.h
index bc5f28b06..6089b8aa0 100644
--- a/src/value_array.h
+++ b/src/value_array.h
@@ -6,6 +6,7 @@
 static inline void
 value_move(mrb_value *s1, const mrb_value *s2, size_t n)
 {
+  if (n == 0) return;
   if (s1 > s2 && s1 < s2 + n)
   {
     s1 += n;
diff --git a/src/variable.c b/src/variable.c
index c36fea6e3..f1375fd4d 100644
--- a/src/variable.c
+++ b/src/variable.c
@@ -11,21 +11,16 @@
 #include <mruby/string.h>
 #include <mruby/variable.h>
 
-#ifndef MRB_IV_SEGMENT_SIZE
-#define MRB_IV_SEGMENT_SIZE 4
-#endif
-
-typedef struct segment {
-  mrb_sym key[MRB_IV_SEGMENT_SIZE];
-  mrb_value val[MRB_IV_SEGMENT_SIZE];
-  struct segment *next;
-} segment;
+struct iv_elem {
+  mrb_sym key;
+  mrb_value val;
+};
 
 /* Instance variable table structure */
 typedef struct iv_tbl {
-  segment *rootseg;
   size_t size;
-  size_t last_len;
+  size_t alloc;
+  struct iv_elem *table;
 } iv_tbl;
 
 /* Creates the instance variable table. */
@@ -36,67 +31,82 @@ iv_new(mrb_state *mrb)
 
   t = (iv_tbl*)mrb_malloc(mrb, sizeof(iv_tbl));
   t->size = 0;
-  t->rootseg =  NULL;
-  t->last_len = 0;
+  t->alloc = 0;
+  t->table = NULL;
 
   return t;
 }
 
+static void iv_put(mrb_state *mrb, iv_tbl *t, mrb_sym sym, mrb_value val);
+
+static void
+iv_rehash(mrb_state *mrb, iv_tbl *t)
+{
+  size_t old_alloc = t->alloc;
+  size_t new_alloc = old_alloc+1;
+  struct iv_elem *old_table = t->table;
+
+  khash_power2(new_alloc);
+  if (old_alloc == new_alloc) return;
+
+  t->alloc = new_alloc;
+  t->size = 0;
+  t->table = (struct iv_elem*)mrb_calloc(mrb, sizeof(struct iv_elem), new_alloc);
+
+  for (size_t i = 0; i < old_alloc; i++) {
+    struct iv_elem *slot = &old_table[i];
+
+    /* key = 0 means empty; val = undef means deleted */
+    if (slot->key != 0 && !mrb_undef_p(slot->val)) {
+      iv_put(mrb, t, slot->key, slot->val);
+    }
+  }
+  mrb_free(mrb, old_table);
+}
+
+#define slot_empty_p(slot) ((slot)->key == 0 && !mrb_undef_p((slot)->val))
+
 /* Set the value for the symbol in the instance variable table. */
 static void
 iv_put(mrb_state *mrb, iv_tbl *t, mrb_sym sym, mrb_value val)
 {
-  segment *seg;
-  segment *prev = NULL;
-  segment *matched_seg = NULL;
-  size_t matched_idx = 0;
-  size_t i;
+  size_t hash, pos, start;
+  struct iv_elem *dslot = NULL;
 
   if (t == NULL) return;
-  seg = t->rootseg;
-  while (seg) {
-    for (i=0; i<MRB_IV_SEGMENT_SIZE; i++) {
-      mrb_sym key = seg->key[i];
-      /* Found room in last segment after last_len */
-      if (!seg->next && i >= t->last_len) {
-        seg->key[i] = sym;
-        seg->val[i] = val;
-        t->last_len = i+1;
+  if (t->alloc == 0) {
+    iv_rehash(mrb, t);
+  }
+  hash = kh_int_hash_func(mrb, sym);
+  start = pos = hash & (t->alloc-1);
+  for (;;) {
+    struct iv_elem *slot = &t->table[pos];
+
+    if (slot->key == sym) {
+      slot->val = val;
+      return;
+    }
+    else if (slot_empty_p(slot)) {
+      t->size++;
+      slot->key = sym;
+      slot->val = val;
+      return;
+    }
+    else if (!dslot && mrb_undef_p(slot->val)) { /* deleted */
+      dslot = slot;
+    }
+    pos = (pos+1) & (t->alloc-1);
+    if (pos == start) {         /* not found */
+      if (dslot) {
         t->size++;
+        dslot->key = sym;
+        dslot->val = val;
         return;
       }
-      if (!matched_seg && key == 0) {
-        matched_seg = seg;
-        matched_idx = i;
-      }
-      else if (key == sym) {
-        seg->val[i] = val;
-        return;
-      }
+      /* no room */
+      iv_rehash(mrb, t);
+      start = pos = hash & (t->alloc-1);
     }
-    prev = seg;
-    seg = seg->next;
-  }
-
-  /* Not found */
-  if (matched_seg) {
-    matched_seg->key[matched_idx] = sym;
-    matched_seg->val[matched_idx] = val;
-    t->size++;
-    return;
-  }
-
-  seg = (segment*)mrb_malloc(mrb, sizeof(segment));
-  seg->next = NULL;
-  seg->key[0] = sym;
-  seg->val[0] = val;
-  t->last_len = 1;
-  t->size++;
-  if (prev) {
-    prev->next = seg;
-  }
-  else {
-    t->rootseg = seg;
   }
 }
 
@@ -104,80 +114,81 @@ iv_put(mrb_state *mrb, iv_tbl *t, mrb_sym sym, mrb_value val)
 static mrb_bool
 iv_get(mrb_state *mrb, iv_tbl *t, mrb_sym sym, mrb_value *vp)
 {
-  segment *seg;
-  size_t i;
+  size_t hash, pos, start;
 
   if (t == NULL) return FALSE;
-  seg = t->rootseg;
-  while (seg) {
-    for (i=0; i<MRB_IV_SEGMENT_SIZE; i++) {
-      mrb_sym key = seg->key[i];
+  if (t->alloc == 0) return FALSE;
+  if (t->size == 0) return FALSE;
 
-      if (!seg->next && i >= t->last_len) {
-        return FALSE;
-      }
-      if (key == sym) {
-        if (vp) *vp = seg->val[i];
-        return TRUE;
-      }
+  hash = kh_int_hash_func(mrb, sym);
+  start = pos = hash & (t->alloc-1);
+  for (;;) {
+    struct iv_elem *slot = &t->table[pos];
+
+    if (slot->key == sym) {
+      if (vp) *vp = slot->val;
+      return TRUE;
+    }
+    else if (slot_empty_p(slot)) {
+      return FALSE;
+    }
+    pos = (pos+1) & (t->alloc-1);
+    if (pos == start) {         /* not found */
+      return FALSE;
     }
-    seg = seg->next;
   }
-  return FALSE;
 }
 
 /* Deletes the value for the symbol from the instance variable table. */
 static mrb_bool
 iv_del(mrb_state *mrb, iv_tbl *t, mrb_sym sym, mrb_value *vp)
 {
-  segment *seg;
-  size_t i;
+  size_t hash, pos, start;
 
   if (t == NULL) return FALSE;
-  seg = t->rootseg;
-  while (seg) {
-    for (i=0; i<MRB_IV_SEGMENT_SIZE; i++) {
-      mrb_sym key = seg->key[i];
+  if (t->alloc == 0) return  FALSE;
+  if (t->size == 0) return FALSE;
 
-      if (!seg->next && i >= t->last_len) {
-        return FALSE;
-      }
-      if (key == sym) {
-        t->size--;
-        seg->key[i] = 0;
-        if (vp) *vp = seg->val[i];
-        return TRUE;
-      }
+  hash = kh_int_hash_func(mrb, sym);
+  start = pos = hash & (t->alloc-1);
+  for (;;) {
+    struct iv_elem *slot = &t->table[pos];
+
+    if (slot->key == sym) {
+      if (vp) *vp = slot->val;
+      t->size--;
+      slot->key = 0;
+      slot->val = mrb_undef_value();
+      return TRUE;
+    }
+    else if (slot_empty_p(slot)) {
+      return FALSE;
+    }
+    pos = (pos+1) & (t->alloc-1);
+    if (pos == start) {         /* not found */
+      return FALSE;
     }
-    seg = seg->next;
   }
-  return FALSE;
 }
 
 /* Iterates over the instance variable table. */
 static void
 iv_foreach(mrb_state *mrb, iv_tbl *t, mrb_iv_foreach_func *func, void *p)
 {
-  segment *seg;
   size_t i;
 
   if (t == NULL) return;
-  seg = t->rootseg;
-  while (seg) {
-    for (i=0; i<MRB_IV_SEGMENT_SIZE; i++) {
-      mrb_sym key = seg->key[i];
+  if (t->alloc == 0) return;
+  if (t->size == 0) return;
 
-      /* no value in last segment after last_len */
-      if (!seg->next && i >= t->last_len) {
+  for (i=0; i<t->alloc; i++) {
+    struct iv_elem *slot = &t->table[i];
+
+    if (slot->key && !mrb_undef_p(slot->val)) {
+      if ((*func)(mrb, slot->key, slot->val, p) != 0) {
         return;
       }
-      if (key != 0) {
-        if ((*func)(mrb, key, seg->val[i], p) != 0) {
-          return;
-        }
-      }
     }
-    seg = seg->next;
   }
   return;
 }
@@ -186,47 +197,28 @@ iv_foreach(mrb_state *mrb, iv_tbl *t, mrb_iv_foreach_func *func, void *p)
 static size_t
 iv_size(mrb_state *mrb, iv_tbl *t)
 {
-  segment *seg;
-  size_t size = 0;
-
   if (t == NULL) return 0;
-  if (t->size > 0) return t->size;
-  seg = t->rootseg;
-  while (seg) {
-    if (seg->next == NULL) {
-      size += t->last_len;
-      return size;
-    }
-    seg = seg->next;
-    size += MRB_IV_SEGMENT_SIZE;
-  }
-  /* empty iv_tbl */
-  return 0;
+  return t->size;
 }
 
 /* Copy the instance variable table. */
 static iv_tbl*
 iv_copy(mrb_state *mrb, iv_tbl *t)
 {
-  segment *seg;
   iv_tbl *t2;
-
   size_t i;
 
-  seg = t->rootseg;
-  t2 = iv_new(mrb);
+  if (t == NULL) return NULL;
+  if (t->alloc == 0) return NULL;
+  if (t->size == 0) return NULL;
 
-  while (seg != NULL) {
-    for (i=0; i<MRB_IV_SEGMENT_SIZE; i++) {
-      mrb_sym key = seg->key[i];
-      mrb_value val = seg->val[i];
+  t2 = iv_new(mrb);
+  for (i=0; i<t->alloc; i++) {
+    struct iv_elem *slot = &t->table[i];
 
-      if ((seg->next == NULL) && (i >= t->last_len)) {
-        return t2;
-      }
-      iv_put(mrb, t2, key, val);
+    if (slot->key && !mrb_undef_p(slot->val)) {
+      iv_put(mrb, t2, slot->key, slot->val);
     }
-    seg = seg->next;
   }
   return t2;
 }
@@ -235,14 +227,7 @@ iv_copy(mrb_state *mrb, iv_tbl *t)
 static void
 iv_free(mrb_state *mrb, iv_tbl *t)
 {
-  segment *seg;
-
-  seg = t->rootseg;
-  while (seg) {
-    segment *p = seg;
-    seg = seg->next;
-    mrb_free(mrb, p);
-  }
+  mrb_free(mrb, t->table);
   mrb_free(mrb, t);
 }
 
@@ -379,11 +364,11 @@ assign_class_name(mrb_state *mrb, struct RObject *obj, mrb_sym sym, mrb_value v)
   if (namespace_p(obj->tt) && namespace_p(mrb_type(v))) {
     struct RObject *c = mrb_obj_ptr(v);
     if (obj != c && ISUPPER(mrb_sym_name_len(mrb, sym, NULL)[0])) {
-      mrb_sym id_classname = mrb_intern_lit(mrb, "__classname__");
+      mrb_sym id_classname = MRB_SYM(__classname__);
       mrb_value o = mrb_obj_iv_get(mrb, c, id_classname);
 
       if (mrb_nil_p(o)) {
-        mrb_sym id_outer = mrb_intern_lit(mrb, "__outer__");
+        mrb_sym id_outer = MRB_SYM(__outer__);
         o = mrb_obj_iv_get(mrb, c, id_outer);
 
         if (mrb_nil_p(o)) {
@@ -643,8 +628,7 @@ mrb_mod_cv_get(mrb_state *mrb, struct RClass *c, mrb_sym sym)
   if (cls && cls->tt == MRB_TT_SCLASS) {
     mrb_value klass;
 
-    klass = mrb_obj_iv_get(mrb, (struct RObject *)cls,
-                           mrb_intern_lit(mrb, "__attached__"));
+    klass = mrb_obj_iv_get(mrb, (struct RObject *)cls, MRB_SYM(__attached__));
     c = mrb_class_ptr(klass);
     if (c->tt == MRB_TT_CLASS || c->tt == MRB_TT_MODULE) {
       given = FALSE;
@@ -688,8 +672,7 @@ mrb_mod_cv_set(mrb_state *mrb, struct RClass *c, mrb_sym sym, mrb_value v)
   if (cls && cls->tt == MRB_TT_SCLASS) {
     mrb_value klass;
 
-    klass = mrb_obj_iv_get(mrb, (struct RObject*)cls,
-                           mrb_intern_lit(mrb, "__attached__"));
+    klass = mrb_obj_iv_get(mrb, (struct RObject*)cls, MRB_SYM(__attached__));
     switch (mrb_type(klass)) {
     case MRB_TT_CLASS:
     case MRB_TT_MODULE:
@@ -743,11 +726,11 @@ mrb_vm_cv_get(mrb_state *mrb, mrb_sym sym)
 {
   struct RClass *c;
 
-  struct RProc *p = mrb->c->ci->proc;
+  const struct RProc *p = mrb->c->ci->proc;
 
   for (;;) {
     c = MRB_PROC_TARGET_CLASS(p);
-    if (c->tt != MRB_TT_SCLASS) break;
+    if (c && c->tt != MRB_TT_SCLASS) break;
     p = p->upper;
   }
   return mrb_mod_cv_get(mrb, c, sym);
@@ -757,11 +740,11 @@ void
 mrb_vm_cv_set(mrb_state *mrb, mrb_sym sym, mrb_value v)
 {
   struct RClass *c;
-  struct RProc *p = mrb->c->ci->proc;
+  const struct RProc *p = mrb->c->ci->proc;
 
   for (;;) {
     c = MRB_PROC_TARGET_CLASS(p);
-    if (c->tt != MRB_TT_SCLASS) break;
+    if (c && c->tt != MRB_TT_SCLASS) break;
     p = p->upper;
   }
   mrb_mod_cv_set(mrb, c, sym, v);
@@ -803,7 +786,7 @@ L_RETRY:
     goto L_RETRY;
   }
   name = mrb_symbol_value(sym);
-  return mrb_funcall_argv(mrb, mrb_obj_value(base), mrb_intern_lit(mrb, "const_missing"), 1, &name);
+  return mrb_funcall_argv(mrb, mrb_obj_value(base), MRB_SYM(const_missing), 1, &name);
 }
 
 MRB_API mrb_value
@@ -819,9 +802,10 @@ mrb_vm_const_get(mrb_state *mrb, mrb_sym sym)
   struct RClass *c;
   struct RClass *c2;
   mrb_value v;
-  struct RProc *proc;
+  const struct RProc *proc;
 
   c = MRB_PROC_TARGET_CLASS(mrb->c->ci->proc);
+  if (!c) c = mrb->object_class;
   if (iv_get(mrb, c->iv, sym, &v)) {
     return v;
   }
@@ -829,7 +813,7 @@ mrb_vm_const_get(mrb_state *mrb, mrb_sym sym)
   while (c2 && c2->tt == MRB_TT_SCLASS) {
     mrb_value klass;
 
-    if (!iv_get(mrb, c2->iv, mrb_intern_lit(mrb, "__attached__"), &klass)) {
+    if (!iv_get(mrb, c2->iv, MRB_SYM(__attached__), &klass)) {
       c2 = NULL;
       break;
     }
@@ -864,6 +848,7 @@ mrb_vm_const_set(mrb_state *mrb, mrb_sym sym, mrb_value v)
   struct RClass *c;
 
   c = MRB_PROC_TARGET_CLASS(mrb->c->ci->proc);
+  if (!c) c = mrb->object_class;
   mrb_obj_iv_set(mrb, (struct RObject*)c, sym, v);
 }
 
@@ -875,6 +860,12 @@ mrb_const_remove(mrb_state *mrb, mrb_value mod, mrb_sym sym)
 }
 
 MRB_API void
+mrb_define_const_id(mrb_state *mrb, struct RClass *mod, mrb_sym name, mrb_value v)
+{
+  mrb_obj_iv_set(mrb, (struct RObject*)mod, name, v);
+}
+
+MRB_API void
 mrb_define_const(mrb_state *mrb, struct RClass *mod, const char *name, mrb_value v)
 {
   mrb_obj_iv_set(mrb, (struct RObject*)mod, mrb_intern_cstr(mrb, name), v);
@@ -1070,7 +1061,7 @@ outer_class(mrb_state *mrb, struct RClass *c)
 {
   mrb_value ov;
 
-  ov = mrb_obj_iv_get(mrb, (struct RObject*)c, mrb_intern_lit(mrb, "__outer__"));
+  ov = mrb_obj_iv_get(mrb, (struct RObject*)c, MRB_SYM(__outer__));
   if (mrb_nil_p(ov)) return NULL;
   switch (mrb_type(ov)) {
   case MRB_TT_CLASS:
@@ -1120,8 +1111,8 @@ mrb_class_find_path(mrb_state *mrb, struct RClass *c)
   str = mrb_sym_name_len(mrb, name, &len);
   mrb_str_cat(mrb, path, str, len);
   if (RSTRING_PTR(path)[0] != '#') {
-    iv_del(mrb, c->iv, mrb_intern_lit(mrb, "__outer__"), NULL);
-    iv_put(mrb, c->iv, mrb_intern_lit(mrb, "__classname__"), path);
+    iv_del(mrb, c->iv, MRB_SYM(__outer__), NULL);
+    iv_put(mrb, c->iv, MRB_SYM(__classname__), path);
     mrb_field_write_barrier_value(mrb, (struct RBasic*)c, path);
     path = mrb_str_dup(mrb, path);
   }
@@ -1131,16 +1122,9 @@ mrb_class_find_path(mrb_state *mrb, struct RClass *c)
 size_t
 mrb_obj_iv_tbl_memsize(mrb_state* mrb, mrb_value obj)
 {
-  size_t nseg = 0;
-  segment *seg;
-
-  if (mrb_obj_ptr(obj)->iv == NULL) return 0;
-  seg = mrb_obj_ptr(obj)->iv->rootseg;
-  while (seg) {
-    nseg++;
-    seg = seg->next;
-  }
-  return sizeof(iv_tbl) + sizeof(segment)*nseg;
+  iv_tbl *t = mrb_obj_ptr(obj)->iv;
+  if (t == NULL) return 0;
+  return sizeof(iv_tbl) + t->alloc*sizeof(struct iv_elem);
 }
 
 #define identchar(c) (ISALNUM(c) || (c) == '_' || !ISASCII(c))
diff --git a/src/vm.c b/src/vm.c
index cc9a187b7..d1f4660be 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -6,7 +6,7 @@
 
 #include <stddef.h>
 #include <stdarg.h>
-#ifndef MRB_WITHOUT_FLOAT
+#ifndef MRB_NO_FLOAT
 #include <math.h>
 #endif
 #include <mruby.h>
@@ -23,6 +23,7 @@
 #include <mruby/opcode.h>
 #include "value_array.h"
 #include <mruby/throw.h>
+#include <mruby/dump.h>
 
 #ifdef MRB_DISABLE_STDIO
 #if defined(__cplusplus)
@@ -222,9 +223,9 @@ mrb_stack_extend(mrb_state *mrb, mrb_int room)
 }
 
 static inline struct REnv*
-uvenv(mrb_state *mrb, int up)
+uvenv(mrb_state *mrb, mrb_int up)
 {
-  struct RProc *proc = mrb->c->ci->proc;
+  const struct RProc *proc = mrb->c->ci->proc;
   struct REnv *e;
 
   while (up--) {
@@ -247,8 +248,8 @@ uvenv(mrb_state *mrb, int up)
   return NULL;
 }
 
-static inline struct RProc*
-top_proc(mrb_state *mrb, struct RProc *proc)
+static inline const struct RProc*
+top_proc(mrb_state *mrb, const struct RProc *proc)
 {
   while (proc->upper) {
     if (MRB_PROC_SCOPE_P(proc) || MRB_PROC_STRICT_P(proc))
@@ -263,8 +264,8 @@ top_proc(mrb_state *mrb, struct RProc *proc)
 #define CI_ACC_RESUMED -3
 
 static inline mrb_callinfo*
-cipush(mrb_state *mrb, const mrb_code *pc, int push_stacks, int acc,
-    struct RClass *target_class, struct RProc *proc, mrb_sym mid, int argc)
+cipush(mrb_state *mrb, const mrb_code *pc, mrb_int push_stacks, mrb_int acc,
+       struct RClass *target_class, const struct RProc *proc, mrb_sym mid, mrb_int argc)
 {
   struct mrb_context *c = mrb->c;
   mrb_callinfo *ci = c->ci;
@@ -280,8 +281,6 @@ cipush(mrb_state *mrb, const mrb_code *pc, int push_stacks, int acc,
   ci->mid = mid;
   ci->proc = proc;
   ci->stackent = c->stack;
-  ci->epos = c->eidx;
-  ci->ridx = ci[-1].ridx;
   ci->pc = pc;
   ci->argc = argc;
   ci->acc = acc;
@@ -327,55 +326,7 @@ cipop(mrb_state *mrb)
 }
 
 void mrb_exc_set(mrb_state *mrb, mrb_value exc);
-static mrb_value mrb_run(mrb_state *mrb, struct RProc* proc, mrb_value self);
-
-static void
-ecall(mrb_state *mrb)
-{
-  struct RProc *p;
-  struct mrb_context *c = mrb->c;
-  mrb_callinfo *ci = c->ci;
-  struct RObject *exc;
-  struct REnv *env;
-  ptrdiff_t cioff;
-  int ai = mrb_gc_arena_save(mrb);
-  uint16_t i;
-  int nregs;
-
-  if (c->eidx == 0) return;
-  i = --c->eidx;
-
-  /* restrict total call depth of ecall() */
-  if (++mrb->ecall_nest > MRB_ECALL_DEPTH_MAX) {
-    mrb_exc_raise(mrb, mrb_obj_value(mrb->stack_err));
-  }
-  p = c->ensure[i];
-  if (!p) return;
-  mrb_assert(!MRB_PROC_CFUNC_P(p));
-  c->ensure[i] = NULL;
-  nregs = p->upper->body.irep->nregs;
-  if (ci->proc && !MRB_PROC_CFUNC_P(ci->proc) &&
-      ci->proc->body.irep->nregs > nregs) {
-    nregs = ci->proc->body.irep->nregs;
-  }
-  cioff = ci - c->cibase;
-  ci = cipush(mrb, NULL, nregs, CI_ACC_SKIP, MRB_PROC_TARGET_CLASS(p), p, ci->mid, 0);
-  env = MRB_PROC_ENV(p);
-  mrb_assert(env);
-  exc = mrb->exc; mrb->exc = 0;
-  if (exc) {
-    mrb_gc_protect(mrb, mrb_obj_value(exc));
-  }
-  if (mrb->c->fib) {
-    mrb_gc_protect(mrb, mrb_obj_value(mrb->c->fib));
-  }
-  mrb_run(mrb, p, env->stack[0]);
-  mrb->c = c;
-  c->ci = c->cibase + cioff;
-  if (!mrb->exc) mrb->exc = exc;
-  mrb_gc_arena_restore(mrb, ai);
-  mrb->ecall_nest--;
-}
+static mrb_value mrb_run(mrb_state *mrb, const struct RProc* proc, mrb_value self);
 
 #ifndef MRB_FUNCALL_ARGC_MAX
 #define MRB_FUNCALL_ARGC_MAX 16
@@ -401,11 +352,30 @@ mrb_funcall(mrb_state *mrb, mrb_value self, const char *name, mrb_int argc, ...)
   return mrb_funcall_argv(mrb, self, mid, argc, argv);
 }
 
-static int
+MRB_API mrb_value
+mrb_funcall_id(mrb_state *mrb, mrb_value self, mrb_sym mid, mrb_int argc, ...)
+{
+  mrb_value argv[MRB_FUNCALL_ARGC_MAX];
+  va_list ap;
+  mrb_int i;
+
+  if (argc > MRB_FUNCALL_ARGC_MAX) {
+    mrb_raise(mrb, E_ARGUMENT_ERROR, "Too long arguments. (limit=" MRB_STRINGIZE(MRB_FUNCALL_ARGC_MAX) ")");
+  }
+
+  va_start(ap, argc);
+  for (i = 0; i < argc; i++) {
+    argv[i] = va_arg(ap, mrb_value);
+  }
+  va_end(ap);
+  return mrb_funcall_argv(mrb, self, mid, argc, argv);
+}
+
+static mrb_int
 ci_nregs(mrb_callinfo *ci)
 {
-  struct RProc *p;
-  int n = 0;
+  const struct RProc *p;
+  mrb_int n = 0;
 
   if (!ci) return 3;
   p = ci->proc;
@@ -455,7 +425,7 @@ mrb_funcall_with_block(mrb_state *mrb, mrb_value self, mrb_sym mid, mrb_int argc
     mrb_method_t m;
     struct RClass *c;
     mrb_callinfo *ci;
-    int n = ci_nregs(mrb->c->ci);
+    mrb_int n = ci_nregs(mrb->c->ci);
     ptrdiff_t voff = -1;
 
     if (!mrb->c->stack) {
@@ -467,7 +437,7 @@ mrb_funcall_with_block(mrb_state *mrb, mrb_value self, mrb_sym mid, mrb_int argc
     c = mrb_class(mrb, self);
     m = mrb_method_search_vm(mrb, &c, mid);
     if (MRB_METHOD_UNDEF_P(m)) {
-      mrb_sym missing = mrb_intern_lit(mrb, "method_missing");
+      mrb_sym missing = MRB_SYM(method_missing);
       mrb_value args = mrb_ary_new_from_values(mrb, argc, argv);
       m = mrb_method_search_vm(mrb, &c, missing);
       if (MRB_METHOD_UNDEF_P(m)) {
@@ -536,7 +506,7 @@ mrb_value
 mrb_exec_irep(mrb_state *mrb, mrb_value self, struct RProc *p)
 {
   mrb_callinfo *ci = mrb->c->ci;
-  int keep, nregs;
+  mrb_int keep, nregs;
 
   mrb->c->stack[0] = self;
   ci->proc = p;
@@ -721,7 +691,7 @@ mrb_yield_with_class(mrb_state *mrb, mrb_value b, mrb_int argc, const mrb_value
   mrb_sym mid = mrb->c->ci->mid;
   mrb_callinfo *ci;
   mrb_value val;
-  int n;
+  mrb_int n;
 
   if (mrb_nil_p(b)) {
     mrb_raise(mrb, E_ARGUMENT_ERROR, "no block given");
@@ -802,17 +772,56 @@ mrb_yield_cont(mrb_state *mrb, mrb_value b, mrb_value self, mrb_int argc, const
 }
 
 static struct RBreak*
-break_new(mrb_state *mrb, struct RProc *p, mrb_value val)
+break_new(mrb_state *mrb, uint32_t tag, const struct RProc *p, mrb_value val)
 {
   struct RBreak *brk;
 
   brk = (struct RBreak*)mrb_obj_alloc(mrb, MRB_TT_BREAK, NULL);
   mrb_break_proc_set(brk, p);
   mrb_break_value_set(brk, val);
+  mrb_break_tag_set(brk, tag);
 
   return brk;
 }
 
+#define MRB_CATCH_FILTER_RESCUE (UINT32_C(1) << MRB_CATCH_RESCUE)
+#define MRB_CATCH_FILTER_ENSURE (UINT32_C(1) << MRB_CATCH_ENSURE)
+#define MRB_CATCH_FILTER_ALL    (MRB_CATCH_FILTER_RESCUE | MRB_CATCH_FILTER_ENSURE)
+
+static const struct mrb_irep_catch_handler *
+catch_handler_find(mrb_state *mrb, mrb_callinfo *ci, const mrb_code *pc, uint32_t filter)
+{
+  const mrb_irep *irep;
+  ptrdiff_t xpc;
+  size_t cnt;
+  const struct mrb_irep_catch_handler *e;
+
+/* The comparison operators use `>` and `<=` because pc already points to the next instruction */
+#define catch_cover_p(pc, beg, end) ((pc) > (beg) && (pc) <= (end))
+
+  if (ci->proc == NULL || MRB_PROC_CFUNC_P(ci->proc)) return NULL;
+  irep = ci->proc->body.irep;
+  if (irep->clen < 1) return NULL;
+  xpc = pc - irep->iseq;
+  /* If it retry at the top level, pc will be 0, so check with -1 as the start position */
+  mrb_assert(catch_cover_p(xpc, -1, irep->ilen));
+  if (!catch_cover_p(xpc, -1, irep->ilen)) return NULL;
+
+  /* Currently uses a simple linear search to avoid processing complexity. */
+  cnt = irep->clen;
+  e = mrb_irep_catch_handler_table(irep) + cnt - 1;
+  for (; cnt > 0; cnt --, e --) {
+    if (((UINT32_C(1) << e->type) & filter) &&
+        catch_cover_p(xpc, bin_to_uint16(e->begin), bin_to_uint16(e->end))) {
+      return e;
+    }
+  }
+
+#undef catch_cover_p
+
+  return NULL;
+}
+
 typedef enum {
   LOCALJUMP_ERROR_RETURN = 0,
   LOCALJUMP_ERROR_BREAK = 1,
@@ -859,6 +868,70 @@ argnum_error(mrb_state *mrb, mrb_int num)
   mrb_exc_set(mrb, exc);
 }
 
+static mrb_bool
+break_tag_p(struct RBreak *brk, uint32_t tag)
+{
+  return (brk != NULL && brk->tt == MRB_TT_BREAK) ? TRUE : FALSE;
+}
+
+static void
+prepare_tagged_break(mrb_state *mrb, uint32_t tag, const struct RProc *proc, mrb_value val)
+{
+  if (break_tag_p((struct RBreak*)mrb->exc, tag)) {
+    mrb_break_tag_set((struct RBreak*)mrb->exc, tag);
+  }
+  else {
+    mrb->exc = (struct RObject*)break_new(mrb, tag, proc, val);
+  }
+}
+
+#define THROW_TAGGED_BREAK(mrb, tag, proc, val) \
+  do { \
+    prepare_tagged_break(mrb, tag, proc, val); \
+    goto L_CATCH_TAGGED_BREAK; \
+  } while (0)
+
+#define UNWIND_ENSURE(mrb, ci, pc, tag, proc, val) \
+  do { \
+    ch = catch_handler_find(mrb, ci, pc, MRB_CATCH_FILTER_ENSURE); \
+    if (ch) { \
+      THROW_TAGGED_BREAK(mrb, tag, proc, val); \
+    } \
+  } while (0)
+
+/*
+ *  CHECKPOINT_RESTORE(tag) {
+ *    This part is executed when jumping by the same "tag" of RBreak (it is not executed the first time).
+ *    Write the code required (initialization of variables, etc.) for the subsequent processing.
+ *  }
+ *  CHECKPOINT_MAIN(tag) {
+ *    This part is always executed.
+ *  }
+ *  CHECKPOINT_END(tag);
+ *
+ *  ...
+ *
+ *  // Jump to CHECKPOINT_RESTORE with the same "tag".
+ *  goto CHECKPOINT_LABEL_MAKE(tag);
+ */
+
+#define CHECKPOINT_LABEL_MAKE(tag) L_CHECKPOINT_ ## tag
+
+#define CHECKPOINT_RESTORE(tag) \
+  do { \
+    if (FALSE) { \
+      CHECKPOINT_LABEL_MAKE(tag): \
+      do {
+
+#define CHECKPOINT_MAIN(tag) \
+      } while (0); \
+    } \
+    do {
+
+#define CHECKPOINT_END(tag) \
+    } while (0); \
+  } while (0)
+
 #define ERR_PC_SET(mrb) mrb->c->ci->err = pc0;
 #define ERR_PC_CLR(mrb) mrb->c->ci->err = 0;
 #ifdef MRB_ENABLE_DEBUG_HOOK
@@ -882,15 +955,15 @@ argnum_error(mrb_state *mrb, mrb_int num)
 #ifndef DIRECT_THREADED
 
 #define INIT_DISPATCH for (;;) { insn = BYTECODE_DECODER(*pc); CODE_FETCH_HOOK(mrb, irep, pc, regs); switch (insn) {
-#define CASE(insn,ops) case insn: pc0=pc++; FETCH_ ## ops ();; L_ ## insn ## _BODY:
-#define NEXT break
+#define CASE(insn,ops) case insn: pc0=pc++; FETCH_ ## ops (); pc_save = pc;
+#define NEXT goto L_END_DISPATCH
 #define JUMP NEXT
-#define END_DISPATCH }}
+#define END_DISPATCH L_END_DISPATCH:;}}
 
 #else
 
 #define INIT_DISPATCH JUMP; return mrb_nil_value();
-#define CASE(insn,ops) L_ ## insn: pc0=pc++; FETCH_ ## ops (); L_ ## insn ## _BODY:
+#define CASE(insn,ops) L_ ## insn: pc0=pc++; FETCH_ ## ops (); pc_save = pc;
 #define NEXT insn=BYTECODE_DECODER(*pc); CODE_FETCH_HOOK(mrb, irep, pc, regs); goto *optable[insn]
 #define JUMP NEXT
 
@@ -899,13 +972,13 @@ argnum_error(mrb_state *mrb, mrb_int num)
 #endif
 
 MRB_API mrb_value
-mrb_vm_run(mrb_state *mrb, struct RProc *proc, mrb_value self, unsigned int stack_keep)
+mrb_vm_run(mrb_state *mrb, const struct RProc *proc, mrb_value self, mrb_int stack_keep)
 {
-  mrb_irep *irep = proc->body.irep;
+  const mrb_irep *irep = proc->body.irep;
   mrb_value result;
   struct mrb_context *c = mrb->c;
   ptrdiff_t cioff = c->ci - c->cibase;
-  unsigned int nregs = irep->nregs;
+  mrb_int nregs = irep->nregs;
 
   if (!c->stack) {
     stack_init(mrb);
@@ -932,7 +1005,7 @@ static mrb_bool
 check_target_class(mrb_state *mrb)
 {
   if (!mrb->c->ci->target_class) {
-    mrb_value exc = mrb_exc_new_str_lit(mrb, E_TYPE_ERROR, "no target class or module");
+    mrb_value exc = mrb_exc_new_lit(mrb, E_TYPE_ERROR, "no target class or module");
     mrb_exc_set(mrb, exc);
     return FALSE;
   }
@@ -942,13 +1015,14 @@ check_target_class(mrb_state *mrb)
 void mrb_hash_check_kdict(mrb_state *mrb, mrb_value self);
 
 MRB_API mrb_value
-mrb_vm_exec(mrb_state *mrb, struct RProc *proc, const mrb_code *pc)
+mrb_vm_exec(mrb_state *mrb, const struct RProc *proc, const mrb_code *pc)
 {
   /* mrb_assert(MRB_PROC_CFUNC_P(proc)) */
   const mrb_code *pc0 = pc;
-  mrb_irep *irep = proc->body.irep;
-  mrb_value *pool = irep->pool;
-  mrb_sym *syms = irep->syms;
+  const mrb_code *volatile pc_save = pc;
+  const mrb_irep *irep = proc->body.irep;
+  const mrb_pool_value *pool = irep->pool;
+  const mrb_sym *syms = irep->syms;
   mrb_code insn;
   int ai = mrb_gc_arena_save(mrb);
   struct mrb_jmpbuf *prev_jmp = mrb->jmp;
@@ -957,6 +1031,7 @@ mrb_vm_exec(mrb_state *mrb, struct RProc *proc, const mrb_code *pc)
   uint16_t b;
   uint8_t c;
   mrb_sym mid;
+  const struct mrb_irep_catch_handler *ch;
 
 #ifdef DIRECT_THREADED
   static void *optable[] = {
@@ -994,27 +1069,47 @@ RETRY_TRY_BLOCK:
     }
 
     CASE(OP_LOADL, BB) {
-#ifdef MRB_WORD_BOXING
-      mrb_value val = pool[b];
-#ifndef MRB_WITHOUT_FLOAT
-      if (mrb_float_p(val)) {
-        val = mrb_float_value(mrb, mrb_float(val));
-      }
-#endif
-      regs[a] = val;
+      switch (pool[b].tt) {   /* number */
+      case IREP_TT_INT32:
+        regs[a] = mrb_int_value(mrb, (mrb_int)pool[b].u.i32);
+        break;
+      case IREP_TT_INT64:
+#if defined(MRB_INT64)
+        regs[a] = mrb_int_value(mrb, (mrb_int)pool[b].u.i64);
+        break;
 #else
-      regs[a] = pool[b];
+#if defined(MRB_64BIT)
+        if (INT32_MIN <= pool[b].u.i64 && pool[b].u.i64 <= INT32_MAX) {
+          regs[a] = mrb_int_value(mrb, (mrb_int)pool[b].u.i64);
+          break;
+        }
 #endif
+        {
+          mrb_value exc = mrb_exc_new_lit(mrb, E_RUNTIME_ERROR, "integer overflow");
+          mrb_exc_set(mrb, exc);
+        }
+        goto L_RAISE;
+#endif
+#ifndef MRB_NO_FLOAT
+      case IREP_TT_FLOAT:
+        regs[a] = mrb_float_value(mrb, pool[b].u.f);
+        break;
+#endif
+      default:
+        /* should not happen (tt:string) */
+        regs[a] = mrb_nil_value();
+        break;
+      }
       NEXT;
     }
 
     CASE(OP_LOADI, BB) {
-      SET_INT_VALUE(regs[a], b);
+      SET_FIXNUM_VALUE(regs[a], b);
       NEXT;
     }
 
     CASE(OP_LOADINEG, BB) {
-      SET_INT_VALUE(regs[a], -b);
+      SET_FIXNUM_VALUE(regs[a], -b);
       NEXT;
     }
 
@@ -1028,12 +1123,12 @@ RETRY_TRY_BLOCK:
     CASE(OP_LOADI_6,B) goto L_LOADI;
     CASE(OP_LOADI_7, B) {
     L_LOADI:
-      SET_INT_VALUE(regs[a], (mrb_int)insn - (mrb_int)OP_LOADI_0);
+      SET_FIXNUM_VALUE(regs[a], (mrb_int)insn - (mrb_int)OP_LOADI_0);
       NEXT;
     }
 
     CASE(OP_LOADI16, BS) {
-      SET_INT_VALUE(regs[a], (mrb_int)(int16_t)b);
+      SET_FIXNUM_VALUE(regs[a], (mrb_int)(int16_t)b);
       NEXT;
     }
 
@@ -1192,32 +1287,49 @@ RETRY_TRY_BLOCK:
       NEXT;
     }
 
-    CASE(OP_ONERR, S) {
-      /* check rescue stack */
-      if (mrb->c->ci->ridx == UINT16_MAX-1) {
-        mrb_value exc = mrb_exc_new_str_lit(mrb, E_RUNTIME_ERROR, "too many nested rescues");
-        mrb_exc_set(mrb, exc);
-        goto L_RAISE;
+    CASE(OP_JMPUW, S) {
+      CHECKPOINT_RESTORE(RBREAK_TAG_JUMP) {
+        struct RBreak *brk = (struct RBreak*)mrb->exc;
+        mrb_value target = mrb_break_value_get(brk);
+        mrb_assert(mrb_integer_p(target));
+        a = (uint32_t)mrb_integer(target);
+        mrb_assert(a >= 0 && a < irep->ilen);
       }
-      /* expand rescue stack */
-      if (mrb->c->rsize <= mrb->c->ci->ridx) {
-        if (mrb->c->rsize == 0) mrb->c->rsize = RESCUE_STACK_INIT_SIZE;
-        else {
-          mrb->c->rsize *= 2;
-          if (mrb->c->rsize <= mrb->c->ci->ridx) {
-            mrb->c->rsize = UINT16_MAX;
+      CHECKPOINT_MAIN(RBREAK_TAG_JUMP) {
+        ch = catch_handler_find(mrb, mrb->c->ci, pc, MRB_CATCH_FILTER_ENSURE);
+        if (ch) {
+          /* avoiding a jump from a catch handler into the same handler */
+          if (a < bin_to_uint16(ch->begin) || a >= bin_to_uint16(ch->end)) {
+            THROW_TAGGED_BREAK(mrb, RBREAK_TAG_JUMP, proc, mrb_fixnum_value(a));
           }
         }
-        mrb->c->rescue = (uint16_t*)mrb_realloc(mrb, mrb->c->rescue, sizeof(uint16_t)*mrb->c->rsize);
       }
-      /* push rescue stack */
-      mrb->c->rescue[mrb->c->ci->ridx++] = a;
-      NEXT;
+      CHECKPOINT_END(RBREAK_TAG_JUMP);
+
+      mrb->exc = NULL; /* clear break object */
+      pc = irep->iseq + a;
+      JUMP;
     }
 
     CASE(OP_EXCEPT, B) {
-      mrb_value exc = mrb_obj_value(mrb->exc);
-      mrb->exc = 0;
+      mrb_value exc;
+
+      if (mrb->exc == NULL) {
+        exc = mrb_nil_value();
+      }
+      else {
+        switch (mrb->exc->tt) {
+        case MRB_TT_BREAK:
+        case MRB_TT_EXCEPTION:
+          exc = mrb_obj_value(mrb->exc);
+          break;
+        default:
+          mrb_assert(!"bad mrb_type");
+          exc = mrb_nil_value();
+          break;
+        }
+        mrb->exc = NULL;
+      }
       regs[a] = exc;
       NEXT;
     }
@@ -1234,7 +1346,7 @@ RETRY_TRY_BLOCK:
         {
           mrb_value exc;
 
-          exc = mrb_exc_new_str_lit(mrb, E_TYPE_ERROR,
+          exc = mrb_exc_new_lit(mrb, E_TYPE_ERROR,
                                     "class or module required for rescue clause");
           mrb_exc_set(mrb, exc);
           goto L_RAISE;
@@ -1245,74 +1357,19 @@ RETRY_TRY_BLOCK:
       NEXT;
     }
 
-    CASE(OP_POPERR, B) {
-      mrb->c->ci->ridx -= a;
-      NEXT;
-    }
-
-    CASE(OP_RAISE, B) {
-      mrb_exc_set(mrb, regs[a]);
-      goto L_RAISE;
-    }
-
-    CASE(OP_EPUSH, B) {
-      struct RProc *p;
-
-      p = mrb_closure_new(mrb, irep->reps[a]);
-      /* check ensure stack */
-      if (mrb->c->eidx == UINT16_MAX-1) {
-        mrb_value exc = mrb_exc_new_str_lit(mrb, E_RUNTIME_ERROR, "too many nested ensures");
-        mrb_exc_set(mrb, exc);
-        goto L_RAISE;
+    CASE(OP_RAISEIF, B) {
+      mrb_value exc = regs[a];
+      if (mrb_break_p(exc)) {
+        mrb->exc = mrb_obj_ptr(exc);
+        goto L_BREAK;
       }
-      /* expand ensure stack */
-      if (mrb->c->esize <= mrb->c->eidx+1) {
-        if (mrb->c->esize == 0) mrb->c->esize = ENSURE_STACK_INIT_SIZE;
-        else {
-          mrb->c->esize *= 2;
-          if (mrb->c->esize <= mrb->c->eidx) {
-            mrb->c->esize = UINT16_MAX;
-          }
-        }
-        mrb->c->ensure = (struct RProc**)mrb_realloc(mrb, mrb->c->ensure, sizeof(struct RProc*)*mrb->c->esize);
+      mrb_exc_set(mrb, exc);
+      if (mrb->exc) {
+        goto L_RAISE;
       }
-      /* push ensure stack */
-      mrb->c->ensure[mrb->c->eidx++] = p;
-      mrb->c->ensure[mrb->c->eidx] = NULL;
-      mrb_gc_arena_restore(mrb, ai);
       NEXT;
     }
 
-    CASE(OP_EPOP, B) {
-      mrb_callinfo *ci = mrb->c->ci;
-      unsigned int n, epos = ci->epos;
-      mrb_value self = regs[0];
-      struct RClass *target_class = ci->target_class;
-
-      if (mrb->c->eidx <= epos) {
-        NEXT;
-      }
-
-      if (a > (int)mrb->c->eidx - epos)
-        a = mrb->c->eidx - epos;
-      for (n=0; n<a; n++) {
-        int nregs = irep->nregs;
-
-        proc = mrb->c->ensure[epos+n];
-        mrb->c->ensure[epos+n] = NULL;
-        if (proc == NULL) continue;
-        irep = proc->body.irep;
-        ci = cipush(mrb, pc, nregs, nregs, target_class, proc, ci->mid, 0);
-        mrb_stack_extend(mrb, irep->nregs);
-        regs[0] = self;
-        pc = irep->iseq;
-      }
-      pool = irep->pool;
-      syms = irep->syms;
-      mrb->c->eidx = epos;
-      JUMP;
-    }
-
     CASE(OP_SENDV, BB) {
       c = CALL_MAXARGS;
       goto L_SEND;
@@ -1344,8 +1401,8 @@ RETRY_TRY_BLOCK:
     mid = syms[b];
     L_SENDB_SYM:
     {
-      int argc = (c == CALL_MAXARGS) ? -1 : c;
-      int bidx = (argc < 0) ? a+2 : a+c+1;
+      mrb_int argc = (c == CALL_MAXARGS) ? -1 : c;
+      mrb_int bidx = (argc < 0) ? a+2 : a+c+1;
       mrb_method_t m;
       struct RClass *cls;
       mrb_callinfo *ci = mrb->c->ci;
@@ -1356,15 +1413,15 @@ RETRY_TRY_BLOCK:
       recv = regs[a];
       blk = regs[bidx];
       if (!mrb_nil_p(blk) && !mrb_proc_p(blk)) {
-        blk = mrb_convert_type(mrb, blk, MRB_TT_PROC, "Proc", "to_proc");
-        /* The stack might have been reallocated during mrb_convert_type(),
+        blk = mrb_type_convert(mrb, blk, MRB_TT_PROC, MRB_SYM(to_proc));
+        /* The stack might have been reallocated during mrb_type_convert(),
            see #3622 */
         regs[bidx] = blk;
       }
       cls = mrb_class(mrb, recv);
       m = mrb_method_search_vm(mrb, &cls, mid);
       if (MRB_METHOD_UNDEF_P(m)) {
-        mrb_sym missing = mrb_intern_lit(mrb, "method_missing");
+        mrb_sym missing = MRB_SYM(method_missing);
         m = mrb_method_search_vm(mrb, &cls, missing);
         if (MRB_METHOD_UNDEF_P(m) || (missing == mrb->c->ci->mid && mrb_obj_eq(mrb, regs[0], recv))) {
           mrb_value args = (argc < 0) ? regs[a+1] : mrb_ary_new_from_values(mrb, c, regs+a+1);
@@ -1479,7 +1536,7 @@ RETRY_TRY_BLOCK:
           mrb->c->stack[0] = mrb_nil_value();
           a = 0;
           c = OP_R_NORMAL;
-          goto L_OP_RETURN_BODY;
+          goto L_RETURN;
         }
         pool = irep->pool;
         syms = irep->syms;
@@ -1501,13 +1558,13 @@ RETRY_TRY_BLOCK:
     }
 
     CASE(OP_SUPER, BB) {
-      int argc = (b == CALL_MAXARGS) ? -1 : b;
+      mrb_int argc = (b == CALL_MAXARGS) ? -1 : b;
       int bidx = (argc < 0) ? a+2 : a+b+1;
       mrb_method_t m;
       struct RClass *cls;
       mrb_callinfo *ci = mrb->c->ci;
       mrb_value recv, blk;
-      struct RProc *p = ci->proc;
+      const struct RProc *p = ci->proc;
       mrb_sym mid = ci->mid;
       struct RClass* target_class = MRB_PROC_TARGET_CLASS(p);
 
@@ -1517,37 +1574,37 @@ RETRY_TRY_BLOCK:
       mrb_assert(bidx < irep->nregs);
 
       if (mid == 0 || !target_class) {
-        mrb_value exc = mrb_exc_new_str_lit(mrb, E_NOMETHOD_ERROR, "super called outside of method");
+        mrb_value exc = mrb_exc_new_lit(mrb, E_NOMETHOD_ERROR, "super called outside of method");
         mrb_exc_set(mrb, exc);
         goto L_RAISE;
       }
       if (target_class->tt == MRB_TT_MODULE) {
         target_class = ci->target_class;
         if (target_class->tt != MRB_TT_ICLASS) {
-          mrb_value exc = mrb_exc_new_str_lit(mrb, E_RUNTIME_ERROR, "superclass info lost [mruby limitations]");
+          mrb_value exc = mrb_exc_new_lit(mrb, E_RUNTIME_ERROR, "superclass info lost [mruby limitations]");
           mrb_exc_set(mrb, exc);
           goto L_RAISE;
         }
       }
       recv = regs[0];
       if (!mrb_obj_is_kind_of(mrb, recv, target_class)) {
-        mrb_value exc = mrb_exc_new_str_lit(mrb, E_TYPE_ERROR,
+        mrb_value exc = mrb_exc_new_lit(mrb, E_TYPE_ERROR,
                                             "self has wrong type to call super in this context");
         mrb_exc_set(mrb, exc);
         goto L_RAISE;
       }
       blk = regs[bidx];
       if (!mrb_nil_p(blk) && !mrb_proc_p(blk)) {
-        blk = mrb_convert_type(mrb, blk, MRB_TT_PROC, "Proc", "to_proc");
+        blk = mrb_type_convert(mrb, blk, MRB_TT_PROC, MRB_SYM(to_proc));
         /* The stack or ci stack might have been reallocated during
-           mrb_convert_type(), see #3622 and #3784 */
+           mrb_type_convert(), see #3622 and #3784 */
         regs[bidx] = blk;
         ci = mrb->c->ci;
       }
       cls = target_class->super;
       m = mrb_method_search_vm(mrb, &cls, mid);
       if (MRB_METHOD_UNDEF_P(m)) {
-        mrb_sym missing = mrb_intern_lit(mrb, "method_missing");
+        mrb_sym missing = MRB_SYM(method_missing);
 
         if (mid != missing) {
           cls = mrb_class(mrb, recv);
@@ -1586,6 +1643,7 @@ RETRY_TRY_BLOCK:
         mrb_gc_arena_restore(mrb, ai);
         if (mrb->exc) goto L_RAISE;
         ci = mrb->c->ci;
+        mrb_assert(!mrb_break_p(v));
         if (!ci->target_class) { /* return from context modifying method (resume/yield) */
           if (ci->acc == CI_ACC_RESUMED) {
             mrb->jmp = prev_jmp;
@@ -1620,18 +1678,18 @@ RETRY_TRY_BLOCK:
     }
 
     CASE(OP_ARGARY, BS) {
-      int m1 = (b>>11)&0x3f;
-      int r  = (b>>10)&0x1;
-      int m2 = (b>>5)&0x1f;
-      int kd = (b>>4)&0x1;
-      int lv = (b>>0)&0xf;
+      mrb_int m1 = (b>>11)&0x3f;
+      mrb_int r  = (b>>10)&0x1;
+      mrb_int m2 = (b>>5)&0x1f;
+      mrb_int kd = (b>>4)&0x1;
+      mrb_int lv = (b>>0)&0xf;
       mrb_value *stack;
 
       if (mrb->c->ci->mid == 0 || mrb->c->ci->target_class == NULL) {
         mrb_value exc;
 
       L_NOSUPER:
-        exc = mrb_exc_new_str_lit(mrb, E_NOMETHOD_ERROR, "super called outside of method");
+        exc = mrb_exc_new_lit(mrb, E_NOMETHOD_ERROR, "super called outside of method");
         mrb_exc_set(mrb, exc);
         goto L_RAISE;
       }
@@ -1649,13 +1707,13 @@ RETRY_TRY_BLOCK:
       else {
         mrb_value *pp = NULL;
         struct RArray *rest;
-        int len = 0;
+        mrb_int len = 0;
 
         if (mrb_array_p(stack[m1])) {
           struct RArray *ary = mrb_ary_ptr(stack[m1]);
 
           pp = ARY_PTR(ary);
-          len = (int)ARY_LEN(ary);
+          len = ARY_LEN(ary);
         }
         regs[a] = mrb_ary_new_capa(mrb, m1+len+m2+kd);
         rest = mrb_ary_ptr(regs[a]);
@@ -1679,22 +1737,22 @@ RETRY_TRY_BLOCK:
     }
 
     CASE(OP_ENTER, W) {
-      int m1 = MRB_ASPEC_REQ(a);
-      int o  = MRB_ASPEC_OPT(a);
-      int r  = MRB_ASPEC_REST(a);
-      int m2 = MRB_ASPEC_POST(a);
-      int kd = (MRB_ASPEC_KEY(a) > 0 || MRB_ASPEC_KDICT(a))? 1 : 0;
+      mrb_int m1 = MRB_ASPEC_REQ(a);
+      mrb_int o  = MRB_ASPEC_OPT(a);
+      mrb_int r  = MRB_ASPEC_REST(a);
+      mrb_int m2 = MRB_ASPEC_POST(a);
+      mrb_int kd = (MRB_ASPEC_KEY(a) > 0 || MRB_ASPEC_KDICT(a))? 1 : 0;
       /* unused
       int b  = MRB_ASPEC_BLOCK(a);
       */
-      int argc = mrb->c->ci->argc;
+      mrb_int argc = mrb->c->ci->argc;
       mrb_value *argv = regs+1;
       mrb_value * const argv0 = argv;
-      int const len = m1 + o + r + m2;
-      int const blk_pos = len + kd + 1;
+      mrb_int const len = m1 + o + r + m2;
+      mrb_int const blk_pos = len + kd + 1;
       mrb_value *blk = &argv[argc < 0 ? 1 : argc];
-      mrb_value kdict;
-      int kargs = kd;
+      mrb_value kdict = mrb_nil_value();
+      mrb_int kargs = kd;
 
       /* arguments is passed with Array */
       if (argc < 0) {
@@ -1746,7 +1804,7 @@ RETRY_TRY_BLOCK:
 
       /* no rest arguments */
       if (argc-kargs < len) {
-        int mlen = m2;
+        mrb_int mlen = m2;
         if (argc < m1+m2) {
           mlen = m1 < argc ? argc - m1 : 0;
         }
@@ -1754,7 +1812,7 @@ RETRY_TRY_BLOCK:
         if (kd) regs[len + 1] = kdict;
 
         /* copy mandatory and optional arguments */
-        if (argv0 != argv) {
+        if (argv0 != argv && argv) {
           value_move(&regs[1], argv, argc-mlen); /* m1 + o */
         }
         if (argc < m1) {
@@ -1776,7 +1834,7 @@ RETRY_TRY_BLOCK:
           pc += (argc - kargs - m1 - m2)*3;
       }
       else {
-        int rnum = 0;
+        mrb_int rnum = 0;
         if (argv0 != argv) {
           regs[blk_pos] = *blk; /* move block */
           if (kd) regs[len + 1] = kdict;
@@ -1862,13 +1920,7 @@ RETRY_TRY_BLOCK:
     c = OP_R_NORMAL;
     L_RETURN:
     {
-       mrb_callinfo *ci;
-
-#define ecall_adjust() do {\
-  ptrdiff_t cioff = ci - mrb->c->cibase;\
-  ecall(mrb);\
-  ci = mrb->c->cibase + cioff;\
-} while (0)
+      mrb_callinfo *ci;
 
       ci = mrb->c->ci;
       if (ci->mid) {
@@ -1896,17 +1948,20 @@ RETRY_TRY_BLOCK:
       L_RAISE:
         ci0 = ci = mrb->c->ci;
         if (ci == mrb->c->cibase) {
-          if (ci->ridx == 0) goto L_FTOP;
-          goto L_RESCUE;
+          ch = catch_handler_find(mrb, ci, pc, MRB_CATCH_FILTER_ALL);
+          if (ch == NULL) goto L_FTOP;
+          goto L_CATCH;
         }
-        while (ci[0].ridx == ci[-1].ridx) {
+        while ((ch = catch_handler_find(mrb, ci, pc, MRB_CATCH_FILTER_ALL)) == NULL) {
           ci = cipop(mrb);
           if (ci[1].acc == CI_ACC_SKIP && prev_jmp) {
             mrb->jmp = prev_jmp;
             MRB_THROW(prev_jmp);
           }
+          pc = ci[1].pc;
           if (ci == mrb->c->cibase) {
-            if (ci->ridx == 0) {
+            ch = catch_handler_find(mrb, ci, pc, MRB_CATCH_FILTER_ALL);
+            if (ch == NULL) {
             L_FTOP:             /* fiber top */
               if (mrb->c == mrb->root_c) {
                 mrb->c->stack = mrb->c->stbase;
@@ -1915,9 +1970,6 @@ RETRY_TRY_BLOCK:
               else {
                 struct mrb_context *c = mrb->c;
 
-                while (c->eidx > ci->epos) {
-                  ecall_adjust();
-                }
                 c->status = MRB_FIBER_TERMINATED;
                 mrb->c = c->prev;
                 c->prev = NULL;
@@ -1926,15 +1978,13 @@ RETRY_TRY_BLOCK:
             }
             break;
           }
-          /* call ensure only when we skip this callinfo */
-          if (ci[0].ridx == ci[-1].ridx) {
-            while (mrb->c->eidx > ci->epos) {
-              ecall_adjust();
-            }
-          }
         }
-      L_RESCUE:
-        if (ci->ridx == 0) goto L_STOP;
+      L_CATCH:
+        if (ch == NULL) goto L_STOP;
+        if (FALSE) {
+        L_CATCH_TAGGED_BREAK: /* from THROW_TAGGED_BREAK() or UNWIND_ENSURE() */
+          ci = ci0 = mrb->c->ci;
+        }
         proc = ci->proc;
         irep = proc->body.irep;
         pool = irep->pool;
@@ -1943,12 +1993,11 @@ RETRY_TRY_BLOCK:
           mrb->c->stack = ci[1].stackent;
         }
         mrb_stack_extend(mrb, irep->nregs);
-        pc = irep->iseq+mrb->c->rescue[--ci->ridx];
+        pc = irep->iseq + bin_to_uint16(ch->target);
       }
       else {
-        int acc;
+        mrb_int acc;
         mrb_value v;
-        struct RProc *dst;
 
         ci = mrb->c->ci;
         v = regs[a];
@@ -1957,7 +2006,9 @@ RETRY_TRY_BLOCK:
         case OP_R_RETURN:
           /* Fall through to OP_R_NORMAL otherwise */
           if (ci->acc >=0 && MRB_PROC_ENV_P(proc) && !MRB_PROC_STRICT_P(proc)) {
-            mrb_callinfo *cibase = mrb->c->cibase;
+            const struct RProc *dst;
+            mrb_callinfo *cibase;
+            cibase = mrb->c->cibase;
             dst = top_proc(mrb, proc);
 
             if (MRB_PROC_ENV_P(dst)) {
@@ -1968,37 +2019,58 @@ RETRY_TRY_BLOCK:
                 goto L_RAISE;
               }
             }
+            /* check jump destination */
             while (cibase <= ci && ci->proc != dst) {
-              if (ci->acc < 0) {
+              if (ci->acc < 0) { /* jump cross C boudary */
                 localjump_error(mrb, LOCALJUMP_ERROR_RETURN);
                 goto L_RAISE;
               }
               ci--;
             }
-            if (ci <= cibase) {
+            if (ci <= cibase) { /* no jump destination */
               localjump_error(mrb, LOCALJUMP_ERROR_RETURN);
               goto L_RAISE;
             }
+            ci = mrb->c->ci;
+            while (cibase <= ci && ci->proc != dst) {
+              CHECKPOINT_RESTORE(RBREAK_TAG_RETURN_BLOCK) {
+                cibase = mrb->c->cibase;
+                dst = top_proc(mrb, proc);
+              }
+              CHECKPOINT_MAIN(RBREAK_TAG_RETURN_BLOCK) {
+                UNWIND_ENSURE(mrb, ci, pc, RBREAK_TAG_RETURN_BLOCK, proc, v);
+              }
+              CHECKPOINT_END(RBREAK_TAG_RETURN_BLOCK);
+              pc = ci->pc;
+              ci = cipop(mrb);
+            }
+            proc = ci->proc;
+            mrb->exc = NULL; /* clear break object */
             break;
           }
           /* fallthrough */
         case OP_R_NORMAL:
         NORMAL_RETURN:
           if (ci == mrb->c->cibase) {
-            struct mrb_context *c = mrb->c;
+            struct mrb_context *c;
+            c = mrb->c;
 
             if (!c->prev) { /* toplevel return */
               regs[irep->nlocals] = v;
-              goto L_STOP;
+              goto CHECKPOINT_LABEL_MAKE(RBREAK_TAG_STOP);
             }
             if (c->prev->ci == c->prev->cibase) {
-              mrb_value exc = mrb_exc_new_str_lit(mrb, E_FIBER_ERROR, "double resume");
+              mrb_value exc = mrb_exc_new_lit(mrb, E_FIBER_ERROR, "double resume");
               mrb_exc_set(mrb, exc);
               goto L_RAISE;
             }
-            while (c->eidx > 0) {
-              ecall(mrb);
+            CHECKPOINT_RESTORE(RBREAK_TAG_RETURN_TOPLEVEL) {
+              c = mrb->c;
+            }
+            CHECKPOINT_MAIN(RBREAK_TAG_RETURN_TOPLEVEL) {
+              UNWIND_ENSURE(mrb, ci, pc, RBREAK_TAG_RETURN_TOPLEVEL, proc, v);
             }
+            CHECKPOINT_END(RBREAK_TAG_RETURN_TOPLEVEL);
             /* automatic yield at the end */
             c->status = MRB_FIBER_TERMINATED;
             mrb->c = c->prev;
@@ -2006,6 +2078,14 @@ RETRY_TRY_BLOCK:
             mrb->c->status = MRB_FIBER_RUNNING;
             ci = mrb->c->ci;
           }
+          CHECKPOINT_RESTORE(RBREAK_TAG_RETURN) {
+            /* do nothing */
+          }
+          CHECKPOINT_MAIN(RBREAK_TAG_RETURN) {
+            UNWIND_ENSURE(mrb, ci, pc, RBREAK_TAG_RETURN, proc, v);
+          }
+          CHECKPOINT_END(RBREAK_TAG_RETURN);
+          mrb->exc = NULL; /* clear break object */
           break;
         case OP_R_BREAK:
           if (MRB_PROC_STRICT_P(proc)) goto NORMAL_RETURN;
@@ -2013,7 +2093,7 @@ RETRY_TRY_BLOCK:
             mrb_value exc;
 
           L_BREAK_ERROR:
-            exc = mrb_exc_new_str_lit(mrb, E_LOCALJUMP_ERROR,
+            exc = mrb_exc_new_lit(mrb, E_LOCALJUMP_ERROR,
                                       "break from proc-closure");
             mrb_exc_set(mrb, exc);
             goto L_RAISE;
@@ -2028,9 +2108,13 @@ RETRY_TRY_BLOCK:
               goto L_BREAK_ERROR;
             }
           }
-          while (mrb->c->eidx > mrb->c->ci->epos) {
-            ecall_adjust();
+          CHECKPOINT_RESTORE(RBREAK_TAG_BREAK) {
+            /* do nothing */
+          }
+          CHECKPOINT_MAIN(RBREAK_TAG_BREAK) {
+            UNWIND_ENSURE(mrb, ci, pc, RBREAK_TAG_BREAK, proc, v);
           }
+          CHECKPOINT_END(RBREAK_TAG_BREAK);
           /* break from fiber block */
           if (ci == mrb->c->cibase && ci->pc) {
             struct mrb_context *c = mrb->c;
@@ -2040,45 +2124,64 @@ RETRY_TRY_BLOCK:
             ci = mrb->c->ci;
           }
           if (ci->acc < 0) {
+            ci = cipop(mrb);
             mrb_gc_arena_restore(mrb, ai);
             mrb->c->vmexec = FALSE;
-            mrb->exc = (struct RObject*)break_new(mrb, proc, v);
+            mrb->exc = (struct RObject*)break_new(mrb, RBREAK_TAG_BREAK, proc, v);
             mrb->jmp = prev_jmp;
             MRB_THROW(prev_jmp);
           }
           if (FALSE) {
+            struct RBreak *brk;
+
           L_BREAK:
-            v = mrb_break_value_get((struct RBreak*)mrb->exc);
-            proc = mrb_break_proc_get((struct RBreak*)mrb->exc);
-            mrb->exc = NULL;
+            brk = (struct RBreak*)mrb->exc;
+            proc = mrb_break_proc_get(brk);
+            v = mrb_break_value_get(brk);
             ci = mrb->c->ci;
+
+            switch (mrb_break_tag_get(brk)) {
+#define DISPATCH_CHECKPOINTS(n, i) case n: goto CHECKPOINT_LABEL_MAKE(n);
+              RBREAK_TAG_FOREACH(DISPATCH_CHECKPOINTS)
+#undef DISPATCH_CHECKPOINTS
+              default:
+                mrb_assert(!"wrong break tag");
+            }
           }
           mrb->c->stack = ci->stackent;
-          proc = proc->upper;
-          while (mrb->c->cibase < ci &&  ci[-1].proc != proc) {
+          while (mrb->c->cibase < ci && ci[-1].proc != proc->upper) {
             if (ci[-1].acc == CI_ACC_SKIP) {
-              while (ci < mrb->c->ci) {
-                cipop(mrb);
-              }
               goto L_BREAK_ERROR;
             }
-            ci--;
+            CHECKPOINT_RESTORE(RBREAK_TAG_BREAK_UPPER) {
+              /* do nothing */
+            }
+            CHECKPOINT_MAIN(RBREAK_TAG_BREAK_UPPER) {
+              UNWIND_ENSURE(mrb, ci, pc, RBREAK_TAG_BREAK_UPPER, proc, v);
+            }
+            CHECKPOINT_END(RBREAK_TAG_BREAK_UPPER);
+            pc = ci->pc;
+            ci = cipop(mrb);
+          }
+          CHECKPOINT_RESTORE(RBREAK_TAG_BREAK_INTARGET) {
+            /* do nothing */
           }
+          CHECKPOINT_MAIN(RBREAK_TAG_BREAK_INTARGET) {
+            UNWIND_ENSURE(mrb, ci, pc, RBREAK_TAG_BREAK_INTARGET, proc, v);
+          }
+          CHECKPOINT_END(RBREAK_TAG_BREAK_INTARGET);
           if (ci == mrb->c->cibase) {
             goto L_BREAK_ERROR;
           }
+          mrb->exc = NULL; /* clear break object */
           break;
         default:
           /* cannot happen */
           break;
         }
-        while (ci < mrb->c->ci) {
-          cipop(mrb);
-        }
-        ci[0].ridx = ci[-1].ridx;
-        while (mrb->c->eidx > ci->epos) {
-          ecall_adjust();
-        }
+        mrb_assert(ci == mrb->c->ci);
+        mrb_assert(mrb->exc == NULL);
+
         if (mrb->c->vmexec && !ci->target_class) {
           mrb_gc_arena_restore(mrb, ai);
           mrb->c->vmexec = FALSE;
@@ -2142,23 +2245,23 @@ RETRY_TRY_BLOCK:
     OP_MATH_CASE_STRING_##op_name();                                        \
     default:                                                                \
       c = 1;                                                                \
-      mid = mrb_intern_lit(mrb, MRB_STRINGIZE(OP_MATH_OP_##op_name));       \
+      mid = MRB_QSYM(op_name);                                              \
       goto L_SEND_SYM;                                                      \
   }                                                                         \
   NEXT;
 #define OP_MATH_CASE_FIXNUM(op_name)                                        \
-  case TYPES2(MRB_TT_FIXNUM, MRB_TT_FIXNUM):                                \
+  case TYPES2(MRB_TT_INTEGER, MRB_TT_INTEGER):                              \
     {                                                                       \
-      mrb_int x = mrb_fixnum(regs[a]), y = mrb_fixnum(regs[a+1]), z;        \
+      mrb_int x = mrb_integer(regs[a]), y = mrb_integer(regs[a+1]), z;      \
       if (mrb_int_##op_name##_overflow(x, y, &z))                           \
         OP_MATH_OVERFLOW_INT(op_name, x, y, z);                             \
       else                                                                  \
-        SET_INT_VALUE(regs[a], z);                                          \
+        SET_INT_VALUE(mrb,regs[a], z);                                      \
     }                                                                       \
     break
-#ifdef MRB_WITHOUT_FLOAT
+#ifdef MRB_NO_FLOAT
 #define OP_MATH_CASE_FLOAT(op_name, t1, t2) (void)0
-#define OP_MATH_OVERFLOW_INT(op_name, x, y, z) SET_INT_VALUE(regs[a], z)
+#define OP_MATH_OVERFLOW_INT(op_name, x, y, z) SET_INT_VALUE(mrb,regs[a], z)
 #else
 #define OP_MATH_CASE_FLOAT(op_name, t1, t2)                                     \
   case TYPES2(OP_MATH_TT_##t1, OP_MATH_TT_##t2):                                \
@@ -2180,7 +2283,7 @@ RETRY_TRY_BLOCK:
 #define OP_MATH_OP_add +
 #define OP_MATH_OP_sub -
 #define OP_MATH_OP_mul *
-#define OP_MATH_TT_fixnum MRB_TT_FIXNUM
+#define OP_MATH_TT_fixnum MRB_TT_INTEGER
 #define OP_MATH_TT_float  MRB_TT_FLOAT
 
     CASE(OP_ADD, B) {
@@ -2196,31 +2299,30 @@ RETRY_TRY_BLOCK:
     }
 
     CASE(OP_DIV, B) {
-#ifndef MRB_WITHOUT_FLOAT
-      double x, y, f;
+      mrb_int mrb_num_div_int(mrb_state *mrb, mrb_int x, mrb_int y);
+#ifndef MRB_NO_FLOAT
+      mrb_float mrb_num_div_flo(mrb_state *mrb, mrb_float x, mrb_float y);
+      mrb_float x, y, f;
 #endif
 
       /* need to check if op is overridden */
       switch (TYPES2(mrb_type(regs[a]),mrb_type(regs[a+1]))) {
-      case TYPES2(MRB_TT_FIXNUM,MRB_TT_FIXNUM):
-#ifdef MRB_WITHOUT_FLOAT
+      case TYPES2(MRB_TT_INTEGER,MRB_TT_INTEGER):
         {
-          mrb_int x = mrb_fixnum(regs[a]);
-          mrb_int y = mrb_fixnum(regs[a+1]);
-          SET_INT_VALUE(regs[a], y ? x / y : 0);
+          mrb_int x = mrb_integer(regs[a]);
+          mrb_int y = mrb_integer(regs[a+1]);
+          mrb_int div = mrb_num_div_int(mrb, x, y);
+          SET_INT_VALUE(mrb, regs[a], div);
         }
-        break;
-#else
-        x = (mrb_float)mrb_fixnum(regs[a]);
-        y = (mrb_float)mrb_fixnum(regs[a+1]);
-        break;
-      case TYPES2(MRB_TT_FIXNUM,MRB_TT_FLOAT):
-        x = (mrb_float)mrb_fixnum(regs[a]);
+        NEXT;
+#ifndef MRB_NO_FLOAT
+      case TYPES2(MRB_TT_INTEGER,MRB_TT_FLOAT):
+        x = (mrb_float)mrb_integer(regs[a]);
         y = mrb_float(regs[a+1]);
         break;
-      case TYPES2(MRB_TT_FLOAT,MRB_TT_FIXNUM):
+      case TYPES2(MRB_TT_FLOAT,MRB_TT_INTEGER):
         x = mrb_float(regs[a]);
-        y = (mrb_float)mrb_fixnum(regs[a+1]);
+        y = (mrb_float)mrb_integer(regs[a+1]);
         break;
       case TYPES2(MRB_TT_FLOAT,MRB_TT_FLOAT):
         x = mrb_float(regs[a]);
@@ -2229,19 +2331,12 @@ RETRY_TRY_BLOCK:
 #endif
       default:
         c = 1;
-        mid = mrb_intern_lit(mrb, "/");
+        mid = MRB_QSYM(div);
         goto L_SEND_SYM;
       }
 
-#ifndef MRB_WITHOUT_FLOAT
-      if (y == 0) {
-        if (x > 0) f = INFINITY;
-        else if (x < 0) f = -INFINITY;
-        else /* if (x == 0) */ f = NAN;
-      }
-      else {
-        f = x / y;
-      }
+#ifndef MRB_NO_FLOAT
+      f = mrb_num_div_flo(mrb, x, y);
       SET_FLOAT_VALUE(mrb, regs[a], f);
 #endif
       NEXT;
@@ -2253,23 +2348,23 @@ RETRY_TRY_BLOCK:
     OP_MATHI_CASE_FIXNUM(op_name);                                          \
     OP_MATHI_CASE_FLOAT(op_name);                                           \
     default:                                                                \
-      SET_INT_VALUE(regs[a+1], b);                                          \
+      SET_INT_VALUE(mrb,regs[a+1], b);                                      \
       c = 1;                                                                \
-      mid = mrb_intern_lit(mrb, MRB_STRINGIZE(OP_MATH_OP_##op_name));       \
+      mid = MRB_QSYM(op_name);                                              \
       goto L_SEND_SYM;                                                      \
   }                                                                         \
   NEXT;
 #define OP_MATHI_CASE_FIXNUM(op_name)                                       \
-  case MRB_TT_FIXNUM:                                                       \
+  case MRB_TT_INTEGER:                                                      \
     {                                                                       \
-      mrb_int x = mrb_fixnum(regs[a]), y = (mrb_int)b, z;                   \
+      mrb_int x = mrb_integer(regs[a]), y = (mrb_int)b, z;                  \
       if (mrb_int_##op_name##_overflow(x, y, &z))                           \
         OP_MATH_OVERFLOW_INT(op_name, x, y, z);                             \
       else                                                                  \
-        SET_INT_VALUE(regs[a], z);                                          \
+        SET_INT_VALUE(mrb,regs[a], z);                                      \
     }                                                                       \
     break
-#ifdef MRB_WITHOUT_FLOAT
+#ifdef MRB_NO_FLOAT
 #define OP_MATHI_CASE_FLOAT(op_name) (void)0
 #else
 #define OP_MATHI_CASE_FLOAT(op_name)                                        \
@@ -2291,17 +2386,17 @@ RETRY_TRY_BLOCK:
 
 #define OP_CMP_BODY(op,v1,v2) (v1(regs[a]) op v2(regs[a+1]))
 
-#ifdef MRB_WITHOUT_FLOAT
-#define OP_CMP(op) do {\
+#ifdef MRB_NO_FLOAT
+#define OP_CMP(op,sym) do {\
   int result;\
   /* need to check if - is overridden */\
   switch (TYPES2(mrb_type(regs[a]),mrb_type(regs[a+1]))) {\
-  case TYPES2(MRB_TT_FIXNUM,MRB_TT_FIXNUM):\
+  case TYPES2(MRB_TT_INTEGER,MRB_TT_INTEGER):\
     result = OP_CMP_BODY(op,mrb_fixnum,mrb_fixnum);\
     break;\
   default:\
     c = 1;\
-    mid = mrb_intern_lit(mrb, # op);\
+    mid = MRB_QSYM(sym);\
     goto L_SEND_SYM;\
   }\
   if (result) {\
@@ -2312,17 +2407,17 @@ RETRY_TRY_BLOCK:
   }\
 } while(0)
 #else
-#define OP_CMP(op) do {\
+#define OP_CMP(op, sym) do {\
   int result;\
   /* need to check if - is overridden */\
   switch (TYPES2(mrb_type(regs[a]),mrb_type(regs[a+1]))) {\
-  case TYPES2(MRB_TT_FIXNUM,MRB_TT_FIXNUM):\
+  case TYPES2(MRB_TT_INTEGER,MRB_TT_INTEGER):\
     result = OP_CMP_BODY(op,mrb_fixnum,mrb_fixnum);\
     break;\
-  case TYPES2(MRB_TT_FIXNUM,MRB_TT_FLOAT):\
+  case TYPES2(MRB_TT_INTEGER,MRB_TT_FLOAT):\
     result = OP_CMP_BODY(op,mrb_fixnum,mrb_float);\
     break;\
-  case TYPES2(MRB_TT_FLOAT,MRB_TT_FIXNUM):\
+  case TYPES2(MRB_TT_FLOAT,MRB_TT_INTEGER):\
     result = OP_CMP_BODY(op,mrb_float,mrb_fixnum);\
     break;\
   case TYPES2(MRB_TT_FLOAT,MRB_TT_FLOAT):\
@@ -2330,7 +2425,7 @@ RETRY_TRY_BLOCK:
     break;\
   default:\
     c = 1;\
-    mid = mrb_intern_lit(mrb, # op);\
+    mid = MRB_QSYM(sym);\
     goto L_SEND_SYM;\
   }\
   if (result) {\
@@ -2347,28 +2442,28 @@ RETRY_TRY_BLOCK:
         SET_TRUE_VALUE(regs[a]);
       }
       else {
-        OP_CMP(==);
+        OP_CMP(==,eq);
       }
       NEXT;
     }
 
     CASE(OP_LT, B) {
-      OP_CMP(<);
+      OP_CMP(<,lt);
       NEXT;
     }
 
     CASE(OP_LE, B) {
-      OP_CMP(<=);
+      OP_CMP(<=,le);
       NEXT;
     }
 
     CASE(OP_GT, B) {
-      OP_CMP(>);
+      OP_CMP(>,gt);
       NEXT;
     }
 
     CASE(OP_GE, B) {
-      OP_CMP(>=);
+      OP_CMP(>=,ge);
       NEXT;
     }
 
@@ -2480,9 +2575,13 @@ RETRY_TRY_BLOCK:
     }
 
     CASE(OP_STRING, BB) {
-      mrb_value str = mrb_str_dup(mrb, pool[b]);
-
-      regs[a] = str;
+      size_t len = pool[b].tt >> 2;
+      if (pool[b].tt & IREP_TT_SFLAG) {
+        regs[a] = mrb_str_new_static(mrb, pool[b].u.str, len);
+      }
+      else {
+        regs[a] = mrb_str_new(mrb, pool[b].u.str, len);
+      }
       mrb_gc_arena_restore(mrb, ai);
       NEXT;
     }
@@ -2530,7 +2629,7 @@ RETRY_TRY_BLOCK:
     L_MAKE_LAMBDA:
     {
       struct RProc *p;
-      mrb_irep *nirep = irep->reps[b];
+      const mrb_irep *nirep = irep->reps[b];
 
       if (c & OP_L_CAPTURE) {
         p = mrb_closure_new(mrb, nirep);
@@ -2581,6 +2680,7 @@ RETRY_TRY_BLOCK:
       super = regs[a+1];
       if (mrb_nil_p(base)) {
         baseclass = MRB_PROC_TARGET_CLASS(mrb->c->ci->proc);
+        if (!baseclass) baseclass = mrb->object_class;
         base = mrb_obj_value(baseclass);
       }
       c = mrb_vm_define_class(mrb, base, super, id);
@@ -2597,6 +2697,7 @@ RETRY_TRY_BLOCK:
       base = regs[a];
       if (mrb_nil_p(base)) {
         baseclass = MRB_PROC_TARGET_CLASS(mrb->c->ci->proc);
+        if (!baseclass) baseclass = mrb->object_class;
         base = mrb_obj_value(baseclass);
       }
       cls = mrb_vm_define_module(mrb, base, id);
@@ -2608,7 +2709,7 @@ RETRY_TRY_BLOCK:
     CASE(OP_EXEC, BB) {
       mrb_value recv = regs[a];
       struct RProc *p;
-      mrb_irep *nirep = irep->reps[b];
+      const mrb_irep *nirep = irep->reps[b];
 
       /* prepare closure */
       p = mrb_proc_new(mrb, nirep);
@@ -2684,56 +2785,30 @@ RETRY_TRY_BLOCK:
     }
 
     CASE(OP_ERR, B) {
-      mrb_value msg = mrb_str_dup(mrb, pool[a]);
+      size_t len = pool[a].tt >> 2;
       mrb_value exc;
 
-      exc = mrb_exc_new_str(mrb, E_LOCALJUMP_ERROR, msg);
+      mrb_assert((pool[a].tt&IREP_TT_NFLAG)==0);
+      exc = mrb_exc_new(mrb, E_LOCALJUMP_ERROR, pool[a].u.str, len);
       ERR_PC_SET(mrb);
       mrb_exc_set(mrb, exc);
       goto L_RAISE;
     }
 
-    CASE(OP_EXT1, Z) {
-      insn = READ_B();
-      switch (insn) {
-#define OPCODE(insn,ops) case OP_ ## insn: FETCH_ ## ops ## _1(); goto L_OP_ ## insn ## _BODY;
-#include "mruby/ops.h"
-#undef OPCODE
-      }
-      pc--;
-      NEXT;
-    }
-    CASE(OP_EXT2, Z) {
-      insn = READ_B();
-      switch (insn) {
-#define OPCODE(insn,ops) case OP_ ## insn: FETCH_ ## ops ## _2(); goto L_OP_ ## insn ## _BODY;
-#include "mruby/ops.h"
-#undef OPCODE
-      }
-      pc--;
-      NEXT;
-    }
-    CASE(OP_EXT3, Z) {
-      uint8_t insn = READ_B();
-      switch (insn) {
-#define OPCODE(insn,ops) case OP_ ## insn: FETCH_ ## ops ## _3(); goto L_OP_ ## insn ## _BODY;
-#include "mruby/ops.h"
-#undef OPCODE
-      }
-      pc--;
-      NEXT;
-    }
-
     CASE(OP_STOP, Z) {
       /*        stop VM */
-    L_STOP:
-      while (mrb->c->eidx > 0) {
-        ecall(mrb);
+      CHECKPOINT_RESTORE(RBREAK_TAG_STOP) {
+        /* do nothing */
+      }
+      CHECKPOINT_MAIN(RBREAK_TAG_STOP) {
+        UNWIND_ENSURE(mrb, mrb->c->ci, pc, RBREAK_TAG_STOP, proc, mrb_nil_value());
       }
-      mrb->c->cibase->ridx = 0;
+      CHECKPOINT_END(RBREAK_TAG_STOP);
+    L_STOP:
       ERR_PC_CLR(mrb);
       mrb->jmp = prev_jmp;
       if (mrb->exc) {
+        mrb_assert(mrb->exc->tt == MRB_TT_EXCEPTION);
         return mrb_obj_value(mrb->exc);
       }
       return regs[irep->nlocals];
@@ -2743,14 +2818,19 @@ RETRY_TRY_BLOCK:
 #undef regs
   }
   MRB_CATCH(&c_jmp) {
+    mrb_callinfo *ci = mrb->c->ci;
+    while (ci > mrb->c->cibase && ci->acc == CI_ACC_DIRECT) {
+      ci = cipop(mrb);
+    }
     exc_catched = TRUE;
+    pc = pc_save;
     goto RETRY_TRY_BLOCK;
   }
   MRB_END_EXC(&c_jmp);
 }
 
 static mrb_value
-mrb_run(mrb_state *mrb, struct RProc *proc, mrb_value self)
+mrb_run(mrb_state *mrb, const struct RProc *proc, mrb_value self)
 {
   if (mrb->c->ci->argc < 0) {
     return mrb_vm_run(mrb, proc, self, 3); /* receiver, args and block) */
@@ -2761,7 +2841,7 @@ mrb_run(mrb_state *mrb, struct RProc *proc, mrb_value self)
 }
 
 MRB_API mrb_value
-mrb_top_run(mrb_state *mrb, struct RProc *proc, mrb_value self, unsigned int stack_keep)
+mrb_top_run(mrb_state *mrb, const struct RProc *proc, mrb_value self, mrb_int stack_keep)
 {
   mrb_value v;