Change VirtualFrame::AdjustCopies to mark target as invalid.

src/virtual-frame.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 357 matching lines @@
                     && value->is_register()
                     && original.reg().is(value->reg());
   bool same_constant = original.is_constant()
                     && value->is_constant()
                     && original.handle().is_identical_to(value->handle());
   if (same_register || same_constant) {
     value->Unuse();
     return;
   }
 
-  // If the original may be a copy, adjust to preserve the copy-on-write
-  // semantics of copied elements.
-  if (original.is_copied() &&
-      (original.is_register() || original.is_memory())) {
-    FrameElement ignored = AdjustCopies(frame_index);
-  }
-
-  // If the original is a register reference, deallocate it.
-  if (original.is_register()) {
-    Unuse(original.reg());
-  }
+  InvalidateFrameSlotAt(frame_index);
 
   FrameElement new_element;
   if (value->is_register()) {
     // There are two cases depending no whether the register already
     // occurs in the frame or not.
     if (register_count(value->reg()) == 0) {
       Use(value->reg());
       elements_[frame_index] =
           FrameElement::RegisterElement(value->reg(),
                                         FrameElement::NOT_SYNCED);
     } else {
       for (int i = 0; i < elements_.length(); i++) {
         FrameElement element = elements_[i];
         if (element.is_register() && element.reg().is(value->reg())) {
-          // The register backing store is lower in the frame than its
-          // copy.
           if (i < frame_index) {
+            // The register backing store is lower in the frame than its
+            // copy.
             elements_[frame_index] = CopyElementAt(i);
           } else {
             // There was an early bailout for the case of setting a
             // register element to itself.
             ASSERT(i != frame_index);
             element.clear_sync();
             elements_[frame_index] = element;
             elements_[i] = CopyElementAt(frame_index);
           }
           // Exit the loop once the appropriate copy is inserted.
@@ skipping 151 matching lines @@
 #endif
   if (stack_pointer_ != other->stack_pointer_) return false;
   for (int i = 0; i < elements_.length(); i++) {
     if (!elements_[i].Equals(other->elements_[i])) return false;
   }
 
   return true;
 }
 
 } }  // namespace v8::internal