When computing pairwise merges of frame elements, we should allow...

src/jump-target.cc

 // Copyright 2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 84 matching lines @@
 FrameElement* JumpTarget::Combine(FrameElement* left, FrameElement* right) {
   // Given a pair of non-null frame element pointers, return one of
   // them as an entry frame candidate or null if they are
   // incompatible.
 
   // If either is invalid, the result is.
   if (!left->is_valid()) return left;
   if (!right->is_valid()) return right;
 
   // If they have the same value, the result is the same.  (Exception:
   // bidirectional frames cannot have constants or copies.)  If either

[William Hesse, 2009/04/02 11:34:30]

Update comment.

   // is unsynced, the result is.
   if (left->is_memory() && right->is_memory()) return left;
 
   if (left->is_register() && right->is_register() &&
       left->reg().is(right->reg())) {
     if (!left->is_synced()) {
       return left;
     } else {
       return right;
     }
   }
 
-  if (direction_ == FORWARD_ONLY &&
-      left->is_constant() &&
+  if (left->is_constant() &&
       right->is_constant() &&
       left->handle().is_identical_to(right->handle())) {
     if (!left->is_synced()) {
       return left;
     } else {
       return right;
     }
   }
 
-  if (direction_ == FORWARD_ONLY &&
-      left->is_copy() &&
+  if (left->is_copy() &&
       right->is_copy() &&
       left->index() == right->index()) {
     if (!left->is_synced()) {
       return left;
     } else {
       return right;
     }
   }
 
   // Otherwise they are incompatible and we will reallocate them.
@@ skipping 571 matching lines @@
   temp.CopyTo(this);
   temp.Reset();  // So the destructor does not deallocate virtual frames.
 
 #ifdef DEBUG
   is_shadowing_ = false;
 #endif
 }
 
 
 } }  // namespace v8::internal