Add `MRB_METHOD_TABLE_INLINE` option.

Now the method tables (in classes/modules and caches) keeps C function
pointers without wrapping in `struct RProc` objects. For the sake of
portability, `mrb_method_t` is represented by the struct and union, but
if the most significant bit of the pointer is not used by the platform,
`mrb_method_t` should be packed in `uintptr_t` to reduce memory usage.

`MRB_METHOD_TABLE_INLINE` is turned on by default for linux.

11 files changed, 205 insertions, 115 deletions

diff --git a/include/mrbconf.h b/include/mrbconf.h
index c4f6f38cd..96ab6b77f 100644
--- a/include/mrbconf.h
+++ b/include/mrbconf.h
@@ -36,6 +36,13 @@
 /* size of the method cache (need to be the power of 2) */
 //#define MRB_METHOD_CACHE_SIZE (1<<7)
 
+/* add -DMRB_METHOD_TABLE_INLINE unless platform uses MSB of pointers */
+//#define MRB_METHOD_TABLE_INLINE
+/* turn MRB_METHOD_TABLE_INLINE on for linux by default */
+#if !defined(MRB_METHOD_TABLE_INLINE) && defined(__linux__)
+# define MRB_METHOD_TABLE_INLINE
+#endif
+
 /* add -DMRB_INT16 to use 16bit integer for mrb_int; conflict with MRB_INT64 */
 //#define MRB_INT16
 
diff --git a/include/mruby.h b/include/mruby.h
index 1413d604e..5c8d38200 100644
--- a/include/mruby.h
+++ b/include/mruby.h
@@ -170,11 +170,25 @@ struct mrb_context {
 # define MRB_METHOD_CACHE_SIZE (1<<7)
 #endif
 
+typedef mrb_value (*mrb_func_t)(struct mrb_state *mrb, mrb_value);
+
+#ifdef MRB_METHOD_TABLE_INLINE
+typedef uintptr_t mrb_method_t;
+#else
+typedef struct {
+  mrb_bool func_p;
+  union {
+    struct RProc *proc;
+    mrb_func_t func;
+  };
+} mrb_method_t;
+#endif
+
 #ifdef MRB_METHOD_CACHE
 struct mrb_cache_entry {
   struct RClass *c;
   mrb_sym mid;
-  struct RProc *m;
+  mrb_method_t m;
 };
 #endif
 
@@ -257,9 +271,6 @@ typedef struct mrb_state {
   mrb_int atexit_stack_len;
 } mrb_state;
 
-
-typedef mrb_value (*mrb_func_t)(mrb_state *mrb, mrb_value);
-
 /**
  * Defines a new class.
  *
diff --git a/include/mruby/class.h b/include/mruby/class.h
index 1e1d3c136..ea35d8e17 100644
--- a/include/mruby/class.h
+++ b/include/mruby/class.h
@@ -74,12 +74,12 @@ MRB_API struct RClass* mrb_define_class_id(mrb_state*, mrb_sym, struct RClass*);
 MRB_API struct RClass* mrb_define_module_id(mrb_state*, mrb_sym);
 MRB_API struct RClass *mrb_vm_define_class(mrb_state*, mrb_value, mrb_value, mrb_sym);
 MRB_API struct RClass *mrb_vm_define_module(mrb_state*, mrb_value, mrb_sym);
-MRB_API void mrb_define_method_raw(mrb_state*, struct RClass*, mrb_sym, struct RProc *);
+MRB_API void mrb_define_method_raw(mrb_state*, struct RClass*, mrb_sym, mrb_method_t);
 MRB_API void mrb_define_method_id(mrb_state *mrb, struct RClass *c, mrb_sym mid, mrb_func_t func, mrb_aspec aspec);
 MRB_API void mrb_alias_method(mrb_state *mrb, struct RClass *c, mrb_sym a, mrb_sym b);
 
-MRB_API struct RProc *mrb_method_search_vm(mrb_state*, struct RClass**, mrb_sym);
-MRB_API struct RProc *mrb_method_search(mrb_state*, struct RClass*, mrb_sym);
+MRB_API mrb_method_t mrb_method_search_vm(mrb_state*, struct RClass**, mrb_sym);
+MRB_API mrb_method_t mrb_method_search(mrb_state*, struct RClass*, mrb_sym);
 
 MRB_API struct RClass* mrb_class_real(struct RClass* cl);
 
diff --git a/include/mruby/proc.h b/include/mruby/proc.h
index b33e9e1a2..d2b676bd0 100644
--- a/include/mruby/proc.h
+++ b/include/mruby/proc.h
@@ -55,8 +55,9 @@ struct RProc {
 #define MRB_ASPEC_KDICT(a)        ((a) & (1<<1))
 #define MRB_ASPEC_BLOCK(a)        ((a) & 1)
 
-#define MRB_PROC_CFUNC 128
-#define MRB_PROC_CFUNC_P(p) (((p)->flags & MRB_PROC_CFUNC) != 0)
+#define MRB_PROC_CFUNC_FL 128
+#define MRB_PROC_CFUNC_P(p) (((p)->flags & MRB_PROC_CFUNC_FL) != 0)
+#define MRB_PROC_CFUNC(p) (p)->body.func
 #define MRB_PROC_STRICT 256
 #define MRB_PROC_STRICT_P(p) (((p)->flags & MRB_PROC_STRICT) != 0)
 #define MRB_PROC_ORPHAN 512
@@ -64,7 +65,7 @@ struct RProc {
 #define MRB_PROC_ENVSET 1024
 #define MRB_PROC_ENV_P(p) (((p)->flags & MRB_PROC_ENVSET) != 0)
 #define MRB_PROC_ENV(p) (MRB_PROC_ENV_P(p) ? (p)->e.env : NULL)
-#define MRB_PROC_TARGET_CLASS(p) (MRB_PROC_ENV_P(p) ? (p)->e.env->c : (p)->e.target_class )
+#define MRB_PROC_TARGET_CLASS(p) (MRB_PROC_ENV_P(p) ? (p)->e.env->c : (p)->e.target_class)
 #define MRB_PROC_SET_TARGET_CLASS(p,tc) do {\
   if (MRB_PROC_ENV_P(p)) {\
     (p)->e.env->c = (tc);\
@@ -95,8 +96,35 @@ MRB_API mrb_value mrb_proc_cfunc_env_get(mrb_state*, mrb_int);
 /* old name */
 #define mrb_cfunc_env_get(mrb, idx) mrb_proc_cfunc_env_get(mrb, idx)
 
+#ifdef MRB_METHOD_TABLE_INLINE
+
+#define MRB_METHOD_FUNC_FL ((uintptr_t)1U<<(sizeof(uintptr_t)*8-1))
+#define MRB_METHOD_FUNC_P(m) ((uintptr_t)(m)&MRB_METHOD_FUNC_FL)
+#define MRB_METHOD_FUNC(m) ((mrb_func_t)((uintptr_t)(m)&(~MRB_METHOD_FUNC_FL)))
+#define MRB_METHOD_FROM_FUNC(m,fn) m=(mrb_method_t)((struct RProc*)((uintptr_t)(fn)|MRB_METHOD_FUNC_FL))
+#define MRB_METHOD_FROM_PROC(m,pr) m=(mrb_method_t)(struct RProc*)(pr)
+#define MRB_METHOD_PROC_P(m) (!MRB_METHOD_FUNC_P(m))
+#define MRB_METHOD_PROC(m) ((struct RProc*)(m))
+#define MRB_METHOD_UNDEF_P(m) ((m)==0)
+
+#else
+
+#define MRB_METHOD_FUNC_P(m) ((m).func_p)
+#define MRB_METHOD_FUNC(m) ((m).func)
+#define MRB_METHOD_FROM_FUNC(m,fn) do{(m).func_p=TRUE;(m).func=(fn);}while(0)
+#define MRB_METHOD_FROM_PROC(m,pr) do{(m).func_p=FALSE;(m).proc=(pr);}while(0)
+#define MRB_METHOD_PROC_P(m) (!MRB_METHOD_FUNC_P(m))
+#define MRB_METHOD_PROC(fn) ((m).proc)
+#define MRB_METHOD_UNDEF_P(m) ((m).proc==NULL)
+
+#endif /* MRB_METHOD_TABLE_INLINE */
+
+#define MRB_METHOD_CFUNC_P(m) (MRB_METHOD_FUNC_P(m)?TRUE:(MRB_METHOD_PROC(m)?(MRB_PROC_CFUNC_P(MRB_METHOD_PROC(m))):FALSE))
+#define MRB_METHOD_CFUNC(m) (MRB_METHOD_FUNC_P(m)?MRB_METHOD_FUNC(m):((MRB_METHOD_PROC(m)&&MRB_PROC_CFUNC_P(MRB_METHOD_PROC(m)))?MRB_PROC_CFUNC(MRB_METHOD_PROC(m)):NULL))
+
+
 #include <mruby/khash.h>
-KHASH_DECLARE(mt, mrb_sym, struct RProc*, TRUE)
+KHASH_DECLARE(mt, mrb_sym, mrb_method_t, TRUE)
 
 MRB_END_DECL
 
diff --git a/mrbgems/mruby-bin-debugger/tools/mrdb/apibreak.c b/mrbgems/mruby-bin-debugger/tools/mrdb/apibreak.c
index dead4b2a8..43e538ab4 100644
--- a/mrbgems/mruby-bin-debugger/tools/mrdb/apibreak.c
+++ b/mrbgems/mruby-bin-debugger/tools/mrdb/apibreak.c
@@ -117,7 +117,7 @@ compare_break_method(mrb_state *mrb, mrb_debug_breakpoint *bp, struct RClass *cl
 {
   const char* class_name;
   const char* method_name;
-  struct RProc* m;
+  mrb_method_t m;
   struct RClass* sc;
   const char* sn;
   mrb_sym ssym;
@@ -136,10 +136,10 @@ compare_break_method(mrb_state *mrb, mrb_debug_breakpoint *bp, struct RClass *cl
     }
     else if (method_p->class_name != NULL) {
       m = mrb_method_search_vm(mrb, &class_obj, method_sym);
-      if (m == NULL) {
+      if (MRB_METHOD_UNDEF_P(m)) {
         return MRB_DEBUG_OK;
       }
-      if (MRB_PROC_CFUNC_P(m)) {
+      if (MRB_METHOD_CFUNC_P(m)) {
         *isCfunc = TRUE;
       }
 
@@ -151,7 +151,7 @@ compare_break_method(mrb_state *mrb, mrb_debug_breakpoint *bp, struct RClass *cl
       sc = mrb_class_get(mrb, method_p->class_name);
       ssym = mrb_symbol(mrb_check_intern_cstr(mrb, method_p->method_name));
       m = mrb_method_search_vm(mrb, &sc, ssym);
-      if (m == NULL) {
+      if (MRB_METHOD_UNDEF_P(m)) {
         return MRB_DEBUG_OK;
       }
 
diff --git a/mrbgems/mruby-proc-ext/test/proc.c b/mrbgems/mruby-proc-ext/test/proc.c
index a77b68e9d..7072fe2e9 100644
--- a/mrbgems/mruby-proc-ext/test/proc.c
+++ b/mrbgems/mruby-proc-ext/test/proc.c
@@ -13,10 +13,13 @@ proc_new_cfunc_with_env(mrb_state *mrb, mrb_value self)
 {
   mrb_sym n;
   mrb_value n_val;
+  mrb_method_t m;
+  struct RProc *p;
   mrb_get_args(mrb, "n", &n);
   n_val = mrb_symbol_value(n);
-  mrb_define_method_raw(mrb, mrb_class_ptr(self), n,
-                        mrb_proc_new_cfunc_with_env(mrb, return_func_name, 1, &n_val));
+  p = mrb_proc_new_cfunc_with_env(mrb, return_func_name, 1, &n_val);
+  MRB_METHOD_FROM_PROC(m, p);
+  mrb_define_method_raw(mrb, mrb_class_ptr(self), n, m);
   return self;
 }
 
@@ -33,9 +36,12 @@ cfunc_env_get(mrb_state *mrb, mrb_value self)
 {
   mrb_sym n;
   mrb_value *argv; mrb_int argc;
+  mrb_method_t m;
+  struct RProc *p;
   mrb_get_args(mrb, "na", &n, &argv, &argc);
-  mrb_define_method_raw(mrb, mrb_class_ptr(self), n,
-                        mrb_proc_new_cfunc_with_env(mrb, return_env, argc, argv));
+  p = mrb_proc_new_cfunc_with_env(mrb, return_env, argc, argv);
+  MRB_METHOD_FROM_PROC(m, p);
+  mrb_define_method_raw(mrb, mrb_class_ptr(self), n, m);
   return self;
 }
 
diff --git a/mrbgems/mruby-struct/src/struct.c b/mrbgems/mruby-struct/src/struct.c
index 1d2e62583..8de4b6c52 100644
--- a/mrbgems/mruby-struct/src/struct.c
+++ b/mrbgems/mruby-struct/src/struct.c
@@ -189,11 +189,14 @@ make_struct_define_accessors(mrb_state *mrb, mrb_value members, struct RClass *c
     const char *name = mrb_sym2name_len(mrb, id, NULL);
 
     if (is_local_id(mrb, name) || is_const_id(mrb, name)) {
+      mrb_method_t m;
       mrb_value at = mrb_fixnum_value(i);
       struct RProc *aref = mrb_proc_new_cfunc_with_env(mrb, mrb_struct_ref, 1, &at);
       struct RProc *aset = mrb_proc_new_cfunc_with_env(mrb, mrb_struct_set_m, 1, &at);
-      mrb_define_method_raw(mrb, c, id, aref);
-      mrb_define_method_raw(mrb, c, mrb_id_attrset(mrb, id), aset);
+      MRB_METHOD_FROM_PROC(m, aref);
+      mrb_define_method_raw(mrb, c, id, m);
+      MRB_METHOD_FROM_PROC(m, aset);
+      mrb_define_method_raw(mrb, c, mrb_id_attrset(mrb, id), m);
       mrb_gc_arena_restore(mrb, ai);
     }
   }
diff --git a/src/class.c b/src/class.c
index fb394cc89..c65038b87 100644
--- a/src/class.c
+++ b/src/class.c
@@ -16,7 +16,7 @@
 #include <mruby/data.h>
 #include <mruby/istruct.h>
 
-KHASH_DEFINE(mt, mrb_sym, struct RProc*, TRUE, kh_int_hash_func, kh_int_hash_equal)
+KHASH_DEFINE(mt, mrb_sym, mrb_method_t, TRUE, kh_int_hash_func, kh_int_hash_equal)
 
 void
 mrb_gc_mark_mt(mrb_state *mrb, struct RClass *c)
@@ -27,9 +27,11 @@ mrb_gc_mark_mt(mrb_state *mrb, struct RClass *c)
   if (!h) return;
   for (k = kh_begin(h); k != kh_end(h); k++) {
     if (kh_exist(h, k)) {
-      struct RProc *m = kh_value(h, k);
-      if (m) {
-        mrb_gc_mark(mrb, (struct RBasic*)m);
+      mrb_method_t m = kh_value(h, k);
+
+      if (MRB_METHOD_PROC_P(m)) {
+        struct RProc *p = MRB_METHOD_PROC(m);
+        mrb_gc_mark(mrb, (struct RBasic*)p);
       }
     }
   }
@@ -419,7 +421,7 @@ mrb_define_class_under(mrb_state *mrb, struct RClass *outer, const char *name, s
 }
 
 MRB_API void
-mrb_define_method_raw(mrb_state *mrb, struct RClass *c, mrb_sym mid, struct RProc *p)
+mrb_define_method_raw(mrb_state *mrb, struct RClass *c, mrb_sym mid, mrb_method_t m)
 {
   khash_t(mt) *h;
   khiter_t k;
@@ -434,8 +436,11 @@ mrb_define_method_raw(mrb_state *mrb, struct RClass *c, mrb_sym mid, struct RPro
   }
   if (!h) h = c->mt = kh_init(mt, mrb);
   k = kh_put(mt, mrb, h, mid);
-  kh_value(h, k) = p;
-  if (p) {
+  kh_value(h, k) = m;
+  if (MRB_METHOD_PROC_P(m) && !MRB_METHOD_UNDEF_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);
     MRB_PROC_SET_TARGET_CLASS(p, c);
@@ -447,13 +452,11 @@ mrb_define_method_raw(mrb_state *mrb, struct RClass *c, mrb_sym mid, struct RPro
 MRB_API void
 mrb_define_method_id(mrb_state *mrb, struct RClass *c, mrb_sym mid, mrb_func_t func, mrb_aspec aspec)
 {
-  struct RProc *p;
+  mrb_method_t m;
   int ai = mrb_gc_arena_save(mrb);
 
-  p = mrb_proc_new_cfunc(mrb, func);
-  MRB_PROC_SET_TARGET_CLASS(p, c);
-  p->flags |= MRB_PROC_SCOPE;
-  mrb_define_method_raw(mrb, c, mid, p);
+  MRB_METHOD_FROM_FUNC(m, func);
+  mrb_define_method_raw(mrb, c, mid, m);
   mrb_gc_arena_restore(mrb, ai);
 }
 
@@ -1383,11 +1386,11 @@ mc_clear_by_id(mrb_state *mrb, struct RClass *c, mrb_sym mid)
 }
 #endif
 
-MRB_API struct RProc*
+MRB_API mrb_method_t
 mrb_method_search_vm(mrb_state *mrb, struct RClass **cp, mrb_sym mid)
 {
   khiter_t k;
-  struct RProc *m;
+  mrb_method_t m;
   struct RClass *c = *cp;
 #ifdef MRB_METHOD_CACHE
   struct RClass *oc = c;
@@ -1406,7 +1409,7 @@ mrb_method_search_vm(mrb_state *mrb, struct RClass **cp, mrb_sym mid)
       k = kh_get(mt, mrb, h, mid);
       if (k != kh_end(h)) {
         m = kh_value(h, k);
-        if (!m) break;
+        if (MRB_METHOD_UNDEF_P(m)) break;
         *cp = c;
 #ifdef MRB_METHOD_CACHE
         mc->c = oc;
@@ -1418,16 +1421,17 @@ mrb_method_search_vm(mrb_state *mrb, struct RClass **cp, mrb_sym mid)
     }
     c = c->super;
   }
-  return NULL;                  /* no method */
+  MRB_METHOD_FROM_PROC(m, NULL);
+  return m;                  /* no method */
 }
 
-MRB_API struct RProc*
+MRB_API mrb_method_t
 mrb_method_search(mrb_state *mrb, struct RClass* c, mrb_sym mid)
 {
-  struct RProc *m;
+  mrb_method_t m;
 
   m = mrb_method_search_vm(mrb, &c, mid);
-  if (!m) {
+  if (MRB_METHOD_UNDEF_P(m)) {
     mrb_value inspect = mrb_funcall(mrb, mrb_obj_value(c), "inspect", 0);
     if (mrb_string_p(inspect) && RSTRING_LEN(inspect) > 64) {
       inspect = mrb_any_to_s(mrb, mrb_obj_value(c));
@@ -1458,6 +1462,8 @@ mrb_mod_attr_reader(mrb_state *mrb, mrb_value mod)
   for (i=0; i<argc; i++) {
     mrb_value name, str;
     mrb_sym method, sym;
+    struct RProc *p;
+    mrb_method_t m;
 
     method = to_sym(mrb, argv[i]);
     name = mrb_sym2str(mrb, method);
@@ -1467,8 +1473,9 @@ mrb_mod_attr_reader(mrb_state *mrb, mrb_value mod)
     sym = mrb_intern_str(mrb, str);
     mrb_iv_check(mrb, sym);
     name = mrb_symbol_value(sym);
-    mrb_define_method_raw(mrb, c, method,
-                          mrb_proc_new_cfunc_with_env(mrb, attr_reader, 1, &name));
+    p = mrb_proc_new_cfunc_with_env(mrb, attr_reader, 1, &name);
+    MRB_METHOD_FROM_PROC(m, p);
+    mrb_define_method_raw(mrb, c, method, m);
     mrb_gc_arena_restore(mrb, ai);
   }
   return mrb_nil_value();
@@ -1498,6 +1505,8 @@ mrb_mod_attr_writer(mrb_state *mrb, mrb_value mod)
   for (i=0; i<argc; i++) {
     mrb_value name, str, attr;
     mrb_sym method, sym;
+    struct RProc *p;
+    mrb_method_t m;
 
     method = to_sym(mrb, argv[i]);
 
@@ -1516,8 +1525,9 @@ mrb_mod_attr_writer(mrb_state *mrb, mrb_value mod)
     mrb_str_cat_lit(mrb, str, "=");
     method = mrb_intern_str(mrb, str);
 
-    mrb_define_method_raw(mrb, c, method,
-                          mrb_proc_new_cfunc_with_env(mrb, attr_writer, 1, &attr));
+    p = mrb_proc_new_cfunc_with_env(mrb, attr_writer, 1, &attr);
+    MRB_METHOD_FROM_PROC(m, p);
+    mrb_define_method_raw(mrb, c, method, m);
     mrb_gc_arena_restore(mrb, ai);
   }
   return mrb_nil_value();
@@ -1560,15 +1570,16 @@ mrb_instance_new(mrb_state *mrb, mrb_value cv)
   mrb_value *argv;
   mrb_int argc;
   mrb_sym init;
-  struct RProc *p;
+  mrb_method_t m;
 
   mrb_get_args(mrb, "*&", &argv, &argc, &blk);
   obj = mrb_instance_alloc(mrb, cv);
   init = mrb_intern_lit(mrb, "initialize");
-  p = mrb_method_search(mrb, mrb_class(mrb, obj), init);
-  if (MRB_PROC_CFUNC_P(p)) {
-    if (p->body.func != mrb_bob_init) {
-      p->body.func(mrb, obj);
+  m = mrb_method_search(mrb, mrb_class(mrb, obj), init);
+  if (MRB_METHOD_CFUNC_P(m)) {
+    mrb_func_t f = MRB_METHOD_CFUNC(m);
+    if (f != mrb_bob_init) {
+      f(mrb, obj);
     }
   }
   else {
@@ -1703,10 +1714,10 @@ mrb_obj_not_equal_m(mrb_state *mrb, mrb_value self)
 MRB_API mrb_bool
 mrb_obj_respond_to(mrb_state *mrb, struct RClass* c, mrb_sym mid)
 {
-  struct RProc *m;
+  mrb_method_t m;
 
   m = mrb_method_search_vm(mrb, &c, mid);
-  if (!m) {
+  if (MRB_METHOD_UNDEF_P(m)) {
     return FALSE;
   }
   return TRUE;
@@ -1846,7 +1857,7 @@ mrb_obj_class(mrb_state *mrb, mrb_value obj)
 MRB_API void
 mrb_alias_method(mrb_state *mrb, struct RClass *c, mrb_sym a, mrb_sym b)
 {
-  struct RProc *m = mrb_method_search(mrb, c, b);
+  mrb_method_t m = mrb_method_search(mrb, c, b);
 
   mrb_define_method_raw(mrb, c, a, m);
 }
@@ -1940,7 +1951,10 @@ undef_method(mrb_state *mrb, struct RClass *c, mrb_sym a)
     mrb_name_error(mrb, a, "undefined method '%S' for class '%S'", mrb_sym2str(mrb, a), mrb_obj_value(c));
   }
   else {
-    mrb_define_method_raw(mrb, c, a, NULL);
+    mrb_method_t m;
+
+    MRB_METHOD_FROM_PROC(m, NULL);
+    mrb_define_method_raw(mrb, c, a, m);
   }
 }
 
@@ -1976,6 +1990,7 @@ mod_define_method(mrb_state *mrb, mrb_value self)
 {
   struct RClass *c = mrb_class_ptr(self);
   struct RProc *p;
+  mrb_method_t m;
   mrb_sym mid;
   mrb_value proc = mrb_undef_value();
   mrb_value blk;
@@ -1998,7 +2013,8 @@ mod_define_method(mrb_state *mrb, mrb_value self)
   p = (struct RProc*)mrb_obj_alloc(mrb, MRB_TT_PROC, mrb->proc_class);
   mrb_proc_copy(p, mrb_proc_ptr(blk));
   p->flags |= MRB_PROC_STRICT;
-  mrb_define_method_raw(mrb, c, mid, p);
+  MRB_METHOD_FROM_PROC(m, p);
+  mrb_define_method_raw(mrb, c, mid, m);
   return mrb_symbol_value(mid);
 }
 
@@ -2379,7 +2395,7 @@ mrb_mod_module_function(mrb_state *mrb, mrb_value mod)
   mrb_value *argv;
   mrb_int argc, i;
   mrb_sym mid;
-  struct RProc *method_rproc;
+  mrb_method_t m;
   struct RClass *rclass;
   int ai;
 
@@ -2399,11 +2415,11 @@ mrb_mod_module_function(mrb_state *mrb, mrb_value mod)
 
     mid = mrb_symbol(argv[i]);
     rclass = mrb_class_ptr(mod);
-    method_rproc = mrb_method_search(mrb, rclass, mid);
+    m = mrb_method_search(mrb, rclass, mid);
 
     prepare_singleton_class(mrb, (struct RBasic*)rclass);
     ai = mrb_gc_arena_save(mrb);
-    mrb_define_method_raw(mrb, rclass->c, mid, method_rproc);
+    mrb_define_method_raw(mrb, rclass->c, mid, m);
     mrb_gc_arena_restore(mrb, ai);
   }
 
diff --git a/src/kernel.c b/src/kernel.c
index 4a20e18c1..1ac49ed04 100644
--- a/src/kernel.c
+++ b/src/kernel.c
@@ -31,8 +31,14 @@ typedef enum {
 MRB_API mrb_bool
 mrb_func_basic_p(mrb_state *mrb, mrb_value obj, mrb_sym mid, mrb_func_t func)
 {
-  struct RProc *me = mrb_method_search(mrb, mrb_class(mrb, obj), mid);
-  if (MRB_PROC_CFUNC_P(me) && (me->body.func == func))
+  mrb_method_t m = mrb_method_search(mrb, mrb_class(mrb, obj), mid);
+  struct RProc *p;
+
+  if (MRB_METHOD_UNDEF_P(m)) return FALSE;
+  if (MRB_METHOD_FUNC_P(m))
+    return MRB_METHOD_FUNC(m) == func;
+  p = MRB_METHOD_PROC(m);
+  if (MRB_PROC_CFUNC_P(p) && (MRB_PROC_CFUNC(p) == func))
     return TRUE;
   return FALSE;
 }
@@ -677,7 +683,9 @@ method_entry_loop(mrb_state *mrb, struct RClass* klass, khash_t(st)* set)
   khash_t(mt) *h = klass->mt;
   if (!h || kh_size(h) == 0) return;
   for (i=0;i<kh_end(h);i++) {
-    if (kh_exist(h, i) && kh_value(h, i)) {
+    if (kh_exist(h, i)) {
+      mrb_method_t m = kh_value(h, i);
+      if (MRB_METHOD_UNDEF_P(m)) continue;
       kh_put(st, mrb, set, kh_key(h, i));
     }
   }
@@ -1134,6 +1142,7 @@ static mrb_value
 mod_define_singleton_method(mrb_state *mrb, mrb_value self)
 {
   struct RProc *p;
+  mrb_method_t m;
   mrb_sym mid;
   mrb_value blk = mrb_nil_value();
 
@@ -1144,7 +1153,8 @@ mod_define_singleton_method(mrb_state *mrb, mrb_value self)
   p = (struct RProc*)mrb_obj_alloc(mrb, MRB_TT_PROC, mrb->proc_class);
   mrb_proc_copy(p, mrb_proc_ptr(blk));
   p->flags |= MRB_PROC_STRICT;
-  mrb_define_method_raw(mrb, mrb_class_ptr(mrb_singleton_class(mrb, self)), mid, p);
+  MRB_METHOD_FROM_PROC(m, p);
+  mrb_define_method_raw(mrb, mrb_class_ptr(mrb_singleton_class(mrb, self)), mid, m);
   return mrb_symbol_value(mid);
 }
 
diff --git a/src/proc.c b/src/proc.c
index 69a9c0299..bd93de618 100644
--- a/src/proc.c
+++ b/src/proc.c
@@ -99,7 +99,7 @@ mrb_proc_new_cfunc(mrb_state *mrb, mrb_func_t func)
 
   p = (struct RProc*)mrb_obj_alloc(mrb, MRB_TT_PROC, mrb->proc_class);
   p->body.func = func;
-  p->flags |= MRB_PROC_CFUNC;
+  p->flags |= MRB_PROC_CFUNC_FL;
   p->upper = 0;
   p->e.target_class = 0;
 
@@ -141,11 +141,12 @@ MRB_API mrb_value
 mrb_proc_cfunc_env_get(mrb_state *mrb, mrb_int idx)
 {
   struct RProc *p = mrb->c->ci->proc;
-  struct REnv *e = MRB_PROC_ENV(p);
+  struct REnv *e;
 
-  if (!MRB_PROC_CFUNC_P(p)) {
+  if (!p || !MRB_PROC_CFUNC_P(p)) {
     mrb_raise(mrb, E_TYPE_ERROR, "Can't get cfunc env from non-cfunc proc.");
   }
+  e = MRB_PROC_ENV(p);
   if (!e) {
     mrb_raise(mrb, E_TYPE_ERROR, "Can't get cfunc env from cfunc Proc without REnv.");
   }
@@ -216,12 +217,6 @@ mrb_proc_cfunc_p(struct RProc *p)
   return MRB_PROC_CFUNC_P(p);
 }
 
-mrb_value
-mrb_proc_call_cfunc(mrb_state *mrb, struct RProc *p, mrb_value self)
-{
-  return (p->body.func)(mrb, self);
-}
-
 /* 15.2.17.4.2 */
 static mrb_value
 mrb_proc_arity(mrb_state *mrb, mrb_value self)
@@ -293,7 +288,8 @@ proc_lambda(mrb_state *mrb, mrb_value self)
 void
 mrb_init_proc(mrb_state *mrb)
 {
-  struct RProc *m;
+  struct RProc *p;
+  mrb_method_t m;
   mrb_irep *call_irep = (mrb_irep *)mrb_malloc(mrb, sizeof(mrb_irep));
   static const mrb_irep mrb_irep_zero = { 0 };
 
@@ -307,7 +303,8 @@ mrb_init_proc(mrb_state *mrb)
   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", mrb_proc_arity, MRB_ARGS_NONE());
 
-  m = mrb_proc_new(mrb, call_irep);
+  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);
 
diff --git a/src/vm.c b/src/vm.c
index 8dfabdafe..170cb832d 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -400,7 +400,7 @@ mrb_funcall_with_block(mrb_state *mrb, mrb_value self, mrb_sym mid, mrb_int argc
     mrb->jmp = 0;
   }
   else {
-    struct RProc *p;
+    mrb_method_t m;
     struct RClass *c;
     mrb_callinfo *ci;
     int n;
@@ -414,12 +414,12 @@ mrb_funcall_with_block(mrb_state *mrb, mrb_value self, mrb_sym mid, mrb_int argc
       mrb_raisef(mrb, E_ARGUMENT_ERROR, "negative argc for funcall (%S)", mrb_fixnum_value(argc));
     }
     c = mrb_class(mrb, self);
-    p = mrb_method_search_vm(mrb, &c, mid);
-    if (!p) {
+    m = mrb_method_search_vm(mrb, &c, mid);
+    if (MRB_METHOD_UNDEF_P(m)) {
       mrb_sym missing = mrb_intern_lit(mrb, "method_missing");
       mrb_value args = mrb_ary_new_from_values(mrb, argc, argv);
-      p = mrb_method_search_vm(mrb, &c, missing);
-      if (!p) {
+      m = mrb_method_search_vm(mrb, &c, missing);
+      if (MRB_METHOD_UNDEF_P(m)) {
         mrb_method_missing(mrb, mid, self, args);
       }
       mrb_ary_unshift(mrb, args, mrb_symbol_value(mid));
@@ -432,7 +432,6 @@ mrb_funcall_with_block(mrb_state *mrb, mrb_value self, mrb_sym mid, mrb_int argc
     }
     ci = cipush(mrb);
     ci->mid = mid;
-    ci->proc = p;
     ci->stackent = mrb->c->stack;
     ci->argc = (int)argc;
     ci->target_class = c;
@@ -440,7 +439,7 @@ mrb_funcall_with_block(mrb_state *mrb, mrb_value self, mrb_sym mid, mrb_int argc
     if (mrb->c->stbase <= argv && argv < mrb->c->stend) {
       voff = argv - mrb->c->stbase;
     }
-    if (MRB_PROC_CFUNC_P(p)) {
+    if (MRB_METHOD_CFUNC_P(m)) {
       ci->nregs = (int)(argc + 2);
       stack_extend(mrb, ci->nregs);
     }
@@ -452,6 +451,8 @@ mrb_funcall_with_block(mrb_state *mrb, mrb_value self, mrb_sym mid, mrb_int argc
       argc = 1;
     }
     else {
+      struct RProc *p = MRB_METHOD_PROC(m);
+      ci->proc = p;
       if (argc < 0) argc = 1;
       ci->nregs = (int)(p->body.irep->nregs + argc);
       stack_extend(mrb, ci->nregs);
@@ -465,18 +466,18 @@ mrb_funcall_with_block(mrb_state *mrb, mrb_value self, mrb_sym mid, mrb_int argc
     }
     mrb->c->stack[argc+1] = blk;
 
-    if (MRB_PROC_CFUNC_P(p)) {
+    if (MRB_METHOD_CFUNC_P(m)) {
       int ai = mrb_gc_arena_save(mrb);
 
       ci->acc = CI_ACC_DIRECT;
-      val = p->body.func(mrb, self);
+      val = MRB_METHOD_CFUNC(m)(mrb, self);
       mrb->c->stack = mrb->c->ci->stackent;
       cipop(mrb);
       mrb_gc_arena_restore(mrb, ai);
     }
     else {
       ci->acc = CI_ACC_SKIP;
-      val = mrb_run(mrb, p, self);
+      val = mrb_run(mrb, MRB_METHOD_PROC(m), self);
     }
   }
   mrb_gc_protect(mrb, val);
@@ -499,7 +500,7 @@ mrb_exec_irep(mrb_state *mrb, mrb_value self, struct RProc *p)
   ci->proc = p;
   ci->target_class = MRB_PROC_TARGET_CLASS(p);
   if (MRB_PROC_CFUNC_P(p)) {
-    return p->body.func(mrb, self);
+    return MRB_PROC_CFUNC(p)(mrb, self);
   }
   ci->nregs = p->body.irep->nregs;
   if (ci->argc < 0) keep = 3;
@@ -547,7 +548,7 @@ mrb_f_send(mrb_state *mrb, mrb_value self)
   mrb_sym name;
   mrb_value block, *argv, *regs;
   mrb_int argc, i, len;
-  struct RProc *p;
+  mrb_method_t m;
   struct RClass *c;
   mrb_callinfo *ci;
 
@@ -559,9 +560,8 @@ mrb_f_send(mrb_state *mrb, mrb_value self)
   }
 
   c = mrb_class(mrb, self);
-  p = mrb_method_search_vm(mrb, &c, name);
-
-  if (!p) {                     /* call method_mising */
+  m = mrb_method_search_vm(mrb, &c, name);
+  if (MRB_METHOD_UNDEF_P(m)) {            /* call method_mising */
     goto funcall;
   }
 
@@ -579,7 +579,10 @@ mrb_f_send(mrb_state *mrb, mrb_value self)
     mrb_ary_shift(mrb, regs[0]);
   }
 
-  return mrb_exec_irep(mrb, self, p);
+  if (MRB_METHOD_CFUNC_P(m)) {
+    return MRB_METHOD_CFUNC(m)(mrb, self);
+  }
+  return mrb_exec_irep(mrb, self, MRB_METHOD_PROC(m));
 }
 
 static mrb_value
@@ -606,7 +609,7 @@ eval_under(mrb_state *mrb, mrb_value self, mrb_value blk, struct RClass *c)
     mrb->c->stack[0] = self;
     mrb->c->stack[1] = self;
     mrb->c->stack[2] = mrb_nil_value();
-    return p->body.func(mrb, self);
+    return MRB_PROC_CFUNC(p)(mrb, self);
   }
   ci->nregs = p->body.irep->nregs;
   stack_extend(mrb, (ci->nregs < 3) ? 3 : ci->nregs);
@@ -725,7 +728,7 @@ mrb_yield_with_class(mrb_state *mrb, mrb_value b, mrb_int argc, const mrb_value
   mrb->c->stack[argc+1] = mrb_nil_value();
 
   if (MRB_PROC_CFUNC_P(p)) {
-    val = p->body.func(mrb, self);
+    val = MRB_PROC_CFUNC(p)(mrb, self);
     mrb->c->stack = mrb->c->ci->stackent;
   }
   else {
@@ -1376,7 +1379,7 @@ RETRY_TRY_BLOCK:
       int n = GETARG_C(i);
       int argc = (n == CALL_MAXARGS) ? -1 : n;
       int bidx = (argc < 0) ? a+2 : a+n+1;
-      struct RProc *m;
+      mrb_method_t m;
       struct RClass *c;
       mrb_callinfo *ci = mrb->c->ci;
       mrb_value recv, blk;
@@ -1400,10 +1403,10 @@ RETRY_TRY_BLOCK:
       }
       c = mrb_class(mrb, recv);
       m = mrb_method_search_vm(mrb, &c, mid);
-      if (!m) {
+      if (MRB_METHOD_UNDEF_P(m)) {
         mrb_sym missing = mrb_intern_lit(mrb, "method_missing");
         m = mrb_method_search_vm(mrb, &c, missing);
-        if (!m) {
+        if (MRB_METHOD_UNDEF_P(m)) {
           mrb_value args = (argc < 0) ? regs[a+1] : mrb_ary_new_from_values(mrb, n, regs+a+1);
           ERR_PC_SET(mrb, pc);
           mrb_method_missing(mrb, mid, recv, args);
@@ -1423,7 +1426,6 @@ RETRY_TRY_BLOCK:
       /* push callinfo */
       ci = cipush(mrb);
       ci->mid = mid;
-      ci->proc = m;
       ci->stackent = mrb->c->stack;
       ci->target_class = c;
       ci->argc = argc;
@@ -1434,9 +1436,17 @@ RETRY_TRY_BLOCK:
       /* prepare stack */
       mrb->c->stack += a;
 
-      if (MRB_PROC_CFUNC_P(m)) {
+      if (MRB_METHOD_CFUNC_P(m)) {
         ci->nregs = (argc < 0) ? 3 : n+2;
-        recv = m->body.func(mrb, recv);
+        if (MRB_METHOD_PROC_P(m)) {
+          struct RProc *p = MRB_METHOD_PROC(m);
+
+          ci->proc = p;
+          recv = p->body.func(mrb, recv);
+        }
+        else {
+          recv = MRB_METHOD_FUNC(m)(mrb, recv);
+        }
         mrb_gc_arena_restore(mrb, ai);
         mrb_gc_arena_shrink(mrb, ai);
         if (mrb->exc) goto L_RAISE;
@@ -1471,8 +1481,8 @@ RETRY_TRY_BLOCK:
       }
       else {
         /* setup environment for calling method */
-        proc = mrb->c->ci->proc = m;
-        irep = m->body.irep;
+        proc = ci->proc = MRB_METHOD_PROC(m);
+        irep = proc->body.irep;
         pool = irep->pool;
         syms = irep->syms;
         ci->nregs = irep->nregs;
@@ -1511,7 +1521,7 @@ RETRY_TRY_BLOCK:
 
       /* prepare stack */
       if (MRB_PROC_CFUNC_P(m)) {
-        recv = m->body.func(mrb, recv);
+        recv = MRB_PROC_CFUNC(m)(mrb, recv);
         mrb_gc_arena_restore(mrb, ai);
         mrb_gc_arena_shrink(mrb, ai);
         if (mrb->exc) goto L_RAISE;
@@ -1560,7 +1570,7 @@ RETRY_TRY_BLOCK:
       int n = GETARG_C(i);
       int argc = (n == CALL_MAXARGS) ? -1 : n;
       int bidx = (argc < 0) ? a+2 : a+n+1;
-      struct RProc *m;
+      mrb_method_t m;
       struct RClass *c;
       mrb_callinfo *ci = mrb->c->ci;
       mrb_value recv, blk;
@@ -1584,10 +1594,10 @@ RETRY_TRY_BLOCK:
       }
       c = ci->target_class->super;
       m = mrb_method_search_vm(mrb, &c, mid);
-      if (!m) {
+      if (MRB_METHOD_UNDEF_P(m)) {
         mrb_sym missing = mrb_intern_lit(mrb, "method_missing");
         m = mrb_method_search_vm(mrb, &c, missing);
-        if (!m) {
+        if (MRB_METHOD_UNDEF_P(m)) {
           mrb_value args = (argc < 0) ? regs[a+1] : mrb_ary_new_from_values(mrb, n, regs+a+1);
           ERR_PC_SET(mrb, pc);
           mrb_method_missing(mrb, mid, recv, args);
@@ -1607,7 +1617,6 @@ RETRY_TRY_BLOCK:
       /* push callinfo */
       ci = cipush(mrb);
       ci->mid = mid;
-      ci->proc = m;
       ci->stackent = mrb->c->stack;
       ci->target_class = c;
       ci->pc = pc + 1;
@@ -1617,10 +1626,10 @@ RETRY_TRY_BLOCK:
       mrb->c->stack += a;
       mrb->c->stack[0] = recv;
 
-      if (MRB_PROC_CFUNC_P(m)) {
+      if (MRB_METHOD_CFUNC_P(m)) {
         mrb_value v;
         ci->nregs = (argc < 0) ? 3 : n+2;
-        v = m->body.func(mrb, recv);
+        v = MRB_METHOD_CFUNC(m)(mrb, recv);
         mrb_gc_arena_restore(mrb, ai);
         if (mrb->exc) goto L_RAISE;
         ci = mrb->c->ci;
@@ -1649,8 +1658,8 @@ RETRY_TRY_BLOCK:
         ci->acc = a;
 
         /* setup environment for calling method */
-        ci->proc = m;
-        irep = m->body.irep;
+        proc = ci->proc = MRB_METHOD_PROC(m);
+        irep = proc->body.irep;
         pool = irep->pool;
         syms = irep->syms;
         ci->nregs = irep->nregs;
@@ -1934,7 +1943,7 @@ RETRY_TRY_BLOCK:
           /* 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;
-            dst = top_proc(mrb, proc); 
+            dst = top_proc(mrb, proc);
 
             if (MRB_PROC_ENV_P(dst)) {
               struct REnv *e = MRB_PROC_ENV(dst);
@@ -2075,7 +2084,7 @@ RETRY_TRY_BLOCK:
       int a = GETARG_A(i);
       int b = GETARG_B(i);
       int n = GETARG_C(i);
-      struct RProc *m;
+      mrb_method_t m;
       struct RClass *c;
       mrb_callinfo *ci;
       mrb_value recv;
@@ -2084,11 +2093,11 @@ RETRY_TRY_BLOCK:
       recv = regs[a];
       c = mrb_class(mrb, recv);
       m = mrb_method_search_vm(mrb, &c, mid);
-      if (!m) {
+      if (MRB_METHOD_UNDEF_P(m)) {
         mrb_value sym = mrb_symbol_value(mid);
         mrb_sym missing = mrb_intern_lit(mrb, "method_missing");
         m = mrb_method_search_vm(mrb, &c, missing);
-        if (!m) {
+        if (MRB_METHOD_UNDEF_P(m)) {
           mrb_value args;
 
           if (n == CALL_MAXARGS) {
@@ -2124,15 +2133,16 @@ RETRY_TRY_BLOCK:
       /* move stack */
       value_move(mrb->c->stack, &regs[a], ci->argc+1);
 
-      if (MRB_PROC_CFUNC_P(m)) {
-        mrb_value v = m->body.func(mrb, recv);
+      if (MRB_METHOD_CFUNC_P(m)) {
+        mrb_value v = MRB_METHOD_CFUNC(m)(mrb, recv);
         mrb->c->stack[0] = v;
         mrb_gc_arena_restore(mrb, ai);
         goto L_RETURN;
       }
       else {
         /* setup environment for calling method */
-        irep = m->body.irep;
+        struct RProc *p = MRB_METHOD_PROC(m);
+        irep = p->body.irep;
         pool = irep->pool;
         syms = irep->syms;
         if (ci->argc < 0) {
@@ -2824,8 +2834,10 @@ RETRY_TRY_BLOCK:
       int a = GETARG_A(i);
       struct RClass *c = mrb_class_ptr(regs[a]);
       struct RProc *p = mrb_proc_ptr(regs[a+1]);
+      mrb_method_t m;
 
-      mrb_define_method_raw(mrb, c, syms[GETARG_B(i)], p);
+      MRB_METHOD_FROM_PROC(m, p);
+      mrb_define_method_raw(mrb, c, syms[GETARG_B(i)], m);
       mrb_gc_arena_restore(mrb, ai);
       NEXT;
     }