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`.

1 files changed, 14 insertions, 16 deletions

diff --git a/src/variable.c b/src/variable.c
index 4fbe82dd9..3e84c573c 100644
--- a/src/variable.c
+++ b/src/variable.c
@@ -632,18 +632,19 @@ mrb_cv_defined(mrb_state *mrb, mrb_value mod, mrb_sym sym)
 mrb_value
 mrb_vm_cv_get(mrb_state *mrb, mrb_sym sym)
 {
-  struct RClass *c = mrb->c->ci->proc->target_class;
+  struct RClass *c;
 
+  c = MRB_PROC_TARGET_CLASS(mrb->c->ci->proc);
   if (!c) c = mrb->c->ci->target_class;
-
   return mrb_mod_cv_get(mrb, c, sym);
 }
 
 void
 mrb_vm_cv_set(mrb_state *mrb, mrb_sym sym, mrb_value v)
 {
-  struct RClass *c = mrb->c->ci->proc->target_class;
+  struct RClass *c;
 
+  c = MRB_PROC_TARGET_CLASS(mrb->c->ci->proc);
   if (!c) c = mrb->c->ci->target_class;
   mrb_mod_cv_set(mrb, c, sym, v);
 }
@@ -700,11 +701,12 @@ mrb_const_get(mrb_state *mrb, mrb_value mod, mrb_sym sym)
 mrb_value
 mrb_vm_const_get(mrb_state *mrb, mrb_sym sym)
 {
-  struct RClass *c = mrb->c->ci->proc->target_class;
+  struct RClass *c;
   struct RClass *c2;
   mrb_value v;
-  mrb_irep *irep;
+  struct RProc *proc;
 
+  c = MRB_PROC_TARGET_CLASS(mrb->c->ci->proc);
   if (!c) c = mrb->c->ci->target_class;
   mrb_assert(c != NULL);
 
@@ -720,15 +722,13 @@ mrb_vm_const_get(mrb_state *mrb, mrb_sym sym)
   }
   if (c2->tt == MRB_TT_CLASS || c2->tt == MRB_TT_MODULE) c = c2;
   mrb_assert(!MRB_PROC_CFUNC_P(mrb->c->ci->proc));
-  irep = mrb->c->ci->proc->body.irep;
-  while (irep) {
-    if (irep->target_class) {
-      c2 = irep->target_class;
-      if (c2->iv && iv_get(mrb, c2->iv, sym, &v)) {
-        return v;
-      }
+  proc = mrb->c->ci->proc;
+  while (proc) {
+    c2 = MRB_PROC_TARGET_CLASS(proc);
+    if (c2 && c2->iv && iv_get(mrb, c2->iv, sym, &v)) { 
+      return v;
     }
-    irep = irep->outer;
+    proc = proc->upper;
   }
   return const_get(mrb, c, sym, TRUE);
 }
@@ -746,9 +746,7 @@ mrb_const_set(mrb_state *mrb, mrb_value mod, mrb_sym sym, mrb_value v)
 void
 mrb_vm_const_set(mrb_state *mrb, mrb_sym sym, mrb_value v)
 {
-  struct RClass *c = mrb->c->ci->proc->target_class;
-
-  if (!c) c = mrb->c->ci->target_class;
+  struct RClass *c = mrb->c->ci->target_class;
   mrb_obj_iv_set(mrb, (struct RObject*)c, sym, v);
 }