Heavily refactored how lexical scope links are implemented; fix #3821

Instead of `irep` links, we added a `upper` link to `struct RProc`.
To make a space for the `upper` link, we moved `target_class` reference.
If a `Proc` does not have `env`, `target_class` is saved in an `union`
shared with `env` (if a `Proc` has env, you can tell it by `MRB_PROC_ENV_P()).
Otherwise `target_class` is referenced from `env->c`. We removed links
in `env` as well.

This change removes 2 members from `mrb_irep` struct, thus saving 2
words per method/proc/block. This also fixes potential memory leaks
due to the circular references caused by a link from `mrb_irep`.

5 files changed, 30 insertions, 33 deletions

diff --git a/mrbgems/mruby-bin-mirb/tools/mirb/mirb.c b/mrbgems/mruby-bin-mirb/tools/mirb/mirb.c
index 891259a3f..3feb4270a 100644
--- a/mrbgems/mruby-bin-mirb/tools/mirb/mirb.c
+++ b/mrbgems/mruby-bin-mirb/tools/mirb/mirb.c
@@ -544,11 +544,11 @@ done:
         if (args.verbose) {
           mrb_codedump_all(mrb, proc);
         }
-        /* adjest stack length of toplevel environment */
+        /* adjust stack length of toplevel environment */
         if (mrb->c->cibase->env) {
           struct REnv *e = mrb->c->cibase->env;
-          if (MRB_ENV_STACK_LEN(e) < proc->body.irep->nlocals) {
-            MRB_SET_ENV_STACK_LEN(e, proc->body.irep->nlocals);
+          if (e && MRB_ENV_STACK_LEN(e) < proc->body.irep->nlocals) {
+            MRB_ENV_SET_STACK_LEN(e, proc->body.irep->nlocals);
           }
         }
         /* pass a proc for evaluation */
diff --git a/mrbgems/mruby-compiler/core/codegen.c b/mrbgems/mruby-compiler/core/codegen.c
index d9902a02e..da29077b0 100644
--- a/mrbgems/mruby-compiler/core/codegen.c
+++ b/mrbgems/mruby-compiler/core/codegen.c
@@ -3034,6 +3034,9 @@ mrb_generate_code(mrb_state *mrb, parser_state *p)
     mrb_irep_decref(mrb, scope->irep);
     mrb_pool_close(scope->mpool);
     proc->c = NULL;
+    if (mrb->c->cibase && mrb->c->cibase->proc == proc->upper) {
+      proc->upper = NULL;
+    }
     mrb->jmp = prev_jmp;
     return proc;
   }
diff --git a/mrbgems/mruby-compiler/core/parse.y b/mrbgems/mruby-compiler/core/parse.y
index bf9d3fe85..e5017b677 100644
--- a/mrbgems/mruby-compiler/core/parse.y
+++ b/mrbgems/mruby-compiler/core/parse.y
@@ -5825,7 +5825,7 @@ mrb_load_exec(mrb_state *mrb, struct mrb_parser_state *p, mrbc_context *c)
       c->keep_lv = TRUE;
     }
   }
-  proc->target_class = target;
+  MRB_PROC_SET_TARGET_CLASS(proc, target);
   if (mrb->c->ci) {
     mrb->c->ci->target_class = target;
   }
diff --git a/mrbgems/mruby-eval/src/eval.c b/mrbgems/mruby-eval/src/eval.c
index 7fd4f1437..7061565ea 100644
--- a/mrbgems/mruby-eval/src/eval.c
+++ b/mrbgems/mruby-eval/src/eval.c
@@ -13,11 +13,9 @@ static struct mrb_irep *
 get_closure_irep(mrb_state *mrb, int level)
 {
   struct mrb_context *c = mrb->c;
-  struct REnv *e = c->ci[-1].proc->env;
-  struct RProc *proc;
+  struct RProc *proc = c->ci[-1].proc;
 
   if (level == 0) {
-    proc = c->ci[-1].proc;
     if (MRB_PROC_CFUNC_P(proc)) {
       return NULL;
     }
@@ -25,16 +23,11 @@ get_closure_irep(mrb_state *mrb, int level)
   }
 
   while (--level) {
-    e = (struct REnv*)e->c;
-    if (!e) return NULL;
+    proc = proc->upper;
+    if (!proc) return NULL;
   }
 
-  if (!e) return NULL;
-  if (!MRB_ENV_STACK_SHARED_P(e)) return NULL;
-  c = e->cxt.c;
-  proc = c->cibase[e->cioff].proc;
-
-  if (!proc || MRB_PROC_CFUNC_P(proc)) {
+  if (MRB_PROC_CFUNC_P(proc)) {
     return NULL;
   }
   return proc->body.irep;
@@ -204,7 +197,9 @@ create_proc_from_string(mrb_state *mrb, char *s, mrb_int len, mrb_value binding,
   struct mrb_parser_state *p;
   struct RProc *proc;
   struct REnv *e;
-  struct mrb_context *c = mrb->c;
+  mrb_callinfo *ci = mrb->c->ci;
+  struct RClass *target_class = NULL;
+  int bidx;
 
   if (!mrb_nil_p(binding)) {
     mrb_raise(mrb, E_ARGUMENT_ERROR, "Binding of eval must be nil.");
@@ -251,19 +246,19 @@ create_proc_from_string(mrb_state *mrb, char *s, mrb_int len, mrb_value binding,
     mrbc_context_free(mrb, cxt);
     mrb_raise(mrb, E_SCRIPT_ERROR, "codegen error");
   }
-  if (c->ci[-1].proc->target_class) {
-    proc->target_class = c->ci[-1].proc->target_class;
-  }
-  e = c->ci[-1].proc->env;
-  if (!e) e = c->ci[-1].env;
-  e = (struct REnv*)mrb_obj_alloc(mrb, MRB_TT_ENV, (struct RClass*)e);
-  e->cxt.c = c;
-  e->cioff = c->ci - c->cibase;
-  e->stack = c->ci->stackent;
-  MRB_SET_ENV_STACK_LEN(e, c->ci->proc->body.irep->nlocals);
-  c->ci->target_class = proc->target_class;
-  c->ci->env = 0;
-  proc->env = e;
+  target_class = MRB_PROC_TARGET_CLASS(ci[-1].proc);
+  e = (struct REnv*)mrb_obj_alloc(mrb, MRB_TT_ENV,
+                                  (struct RClass*)target_class);
+  e->mid = ci->mid;
+  e->stack = ci->stackent;
+  MRB_ENV_SET_STACK_LEN(e, ci->proc->body.irep->nlocals);
+  bidx = ci->argc;
+  if (ci->argc < 0) bidx = 2;
+  else bidx += 1;
+  MRB_ENV_SET_BIDX(e, bidx);
+  proc->e.env = e;
+  proc->flags |= MRB_PROC_ENVSET;
+  ci->target_class = target_class;
   patch_irep(mrb, proc->body.irep, 0, proc->body.irep);
   /* mrb_codedump_all(mrb, proc); */
 
@@ -322,8 +317,7 @@ f_instance_eval(mrb_state *mrb, mrb_value self)
     mrb_get_args(mrb, "s|zi", &s, &len, &file, &line);
     cv = mrb_singleton_class(mrb, self);
     proc = create_proc_from_string(mrb, s, len, mrb_nil_value(), file, line);
-    proc->target_class = mrb_class_ptr(cv);
-    mrb->c->ci->env = NULL;
+    MRB_PROC_SET_TARGET_CLASS(proc, mrb_class_ptr(cv));
     mrb_assert(!MRB_PROC_CFUNC_P(proc));
     return exec_irep(mrb, self, proc);
   }
diff --git a/mrbgems/mruby-fiber/src/fiber.c b/mrbgems/mruby-fiber/src/fiber.c
index 57fe9401c..be9033063 100644
--- a/mrbgems/mruby-fiber/src/fiber.c
+++ b/mrbgems/mruby-fiber/src/fiber.c
@@ -123,7 +123,7 @@ fiber_init(mrb_state *mrb, mrb_value self)
 
   /* adjust return callinfo */
   ci = c->ci;
-  ci->target_class = p->target_class;
+  ci->target_class = MRB_PROC_TARGET_CLASS(p);
   ci->proc = p;
   mrb_field_write_barrier(mrb, (struct RBasic*)mrb_obj_ptr(self), (struct RBasic*)p);
   ci->pc = p->body.irep->iseq;
@@ -213,7 +213,7 @@ fiber_switch(mrb_state *mrb, mrb_value self, mrb_int len, const mrb_value *a, mr
       *b++ = *a++;
     }
     c->cibase->argc = (int)len;
-    value = c->stack[0] = c->ci->proc->env->stack[0];
+    value = c->stack[0] = MRB_PROC_ENV(c->ci->proc)->stack[0];
   }
   else {
     value = fiber_result(mrb, a, len);