A change in the way we place TransitionElementKinds in the tree.

src/ia32/lithium-ia32.cc

 // Copyright 2012 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 2082 matching lines @@
   LStoreKeyedGeneric* result =
       new(zone()) LStoreKeyedGeneric(context, object, key, value);
   return MarkAsCall(result, instr);
 }
 
 
 LInstruction* LChunkBuilder::DoTransitionElementsKind(
     HTransitionElementsKind* instr) {
   ElementsKind from_kind = instr->original_map()->elements_kind();
   ElementsKind to_kind = instr->transitioned_map()->elements_kind();
-  if (IsSimpleMapChangeTransition(from_kind, to_kind)) {
-    LOperand* object = UseRegister(instr->object());
-    LOperand* new_map_reg = TempRegister();
-    LOperand* temp_reg = TempRegister();
-    LTransitionElementsKind* result =
-        new(zone()) LTransitionElementsKind(object, new_map_reg, temp_reg);
-    return DefineSameAsFirst(result);
-  } else {
-    LOperand* object = UseFixed(instr->object(), eax);
-    LOperand* fixed_object_reg = FixedTemp(edx);
-    LOperand* new_map_reg = FixedTemp(ebx);
-    LTransitionElementsKind* result =
-        new(zone()) LTransitionElementsKind(object,
-                                            new_map_reg,
-                                            fixed_object_reg);
-    return MarkAsCall(DefineFixed(result, eax), instr);
+  bool needs_pointer_map = !IsSimpleMapChangeTransition(from_kind, to_kind);
+
+  LOperand* object = UseRegister(instr->object());
+  LOperand* new_map_reg = TempRegister();
+  LOperand* temp_reg = TempRegister();
+  LTransitionElementsKind* result =
+      new(zone()) LTransitionElementsKind(object, new_map_reg, temp_reg);
+  if (needs_pointer_map) {
+    AssignPointerMap(result);
   }
+  return DefineSameAsFirst(result);
+
+  /*
+      // Old needs_pointer_map case
+      LOperand* object = UseFixed(instr->object(), eax);
+      LOperand* fixed_object_reg = FixedTemp(edx);
+      LOperand* new_map_reg = FixedTemp(ebx);
+      LTransitionElementsKind* result =
+          new(zone()) LTransitionElementsKind(object,
+                                              new_map_reg,
+                                              fixed_object_reg);
+      return MarkAsCall(DefineFixed(result, eax), instr);
+  */
 }
 
 
 LInstruction* LChunkBuilder::DoStoreNamedField(HStoreNamedField* instr) {
   bool needs_write_barrier = instr->NeedsWriteBarrier();
   bool needs_write_barrier_for_map = !instr->transition().is_null() &&
       instr->NeedsWriteBarrierForMap();
 
   LOperand* obj;
   if (needs_write_barrier) {
@@ skipping 313 matching lines @@
 LInstruction* LChunkBuilder::DoLoadFieldByIndex(HLoadFieldByIndex* instr) {
   LOperand* object = UseRegister(instr->object());
   LOperand* index = UseTempRegister(instr->index());
   return DefineSameAsFirst(new(zone()) LLoadFieldByIndex(object, index));
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32