Implement tracking and optimizations of packed arrays

src/ia32/lithium-ia32.cc

Index: src/ia32/lithium-ia32.cc
diff --git a/src/ia32/lithium-ia32.cc b/src/ia32/lithium-ia32.cc
index 5adaf431bd702ff88a4565897b4698949d3a7736..22f56b3012a707f9e29d35897fa0fa1caaf5b207 100644
--- a/src/ia32/lithium-ia32.cc
+++ b/src/ia32/lithium-ia32.cc
@@ -2093,8 +2093,12 @@ LInstruction* LChunkBuilder::DoStoreKeyedGeneric(HStoreKeyedGeneric* instr) {
 
 LInstruction* LChunkBuilder::DoTransitionElementsKind(
     HTransitionElementsKind* instr) {
-  if (instr->original_map()->elements_kind() == FAST_SMI_ONLY_ELEMENTS &&
-      instr->transitioned_map()->elements_kind() == FAST_ELEMENTS) {
+  ElementsKind from_kind = instr->original_map()->elements_kind();
+  ElementsKind to_kind = instr->transitioned_map()->elements_kind();
+  bool simple_map_change = (GetHoleyElementsKind(from_kind) == to_kind) ||
+      (IsFastSmiElementsKind(from_kind) &&
+       IsFastObjectElementsKind(to_kind));
+  if (simple_map_change) {
     LOperand* object = UseRegister(instr->object());
     LOperand* new_map_reg = TempRegister();
     LOperand* temp_reg = TempRegister();