Basic support for tracking smi-only arrays on ia32.

src/code-stubs.cc

Index: src/code-stubs.cc
diff --git a/src/code-stubs.cc b/src/code-stubs.cc
index f309a82fb50f98b54aef808a435852f09d6d6f19..5cf02fdb249bc6f69ff0b2ef55ecf25dad91ac4d 100644
--- a/src/code-stubs.cc
+++ b/src/code-stubs.cc
@@ -250,6 +250,7 @@ void InstanceofStub::PrintName(StringStream* stream) {
 void KeyedLoadElementStub::Generate(MacroAssembler* masm) {
   switch (elements_kind_) {
     case FAST_ELEMENTS:
+    case FAST_SMI_ONLY_ELEMENTS:
       KeyedLoadStubCompiler::GenerateLoadFastElement(masm);
       break;
     case FAST_DOUBLE_ELEMENTS:
@@ -279,7 +280,15 @@ void KeyedLoadElementStub::Generate(MacroAssembler* masm) {
 void KeyedStoreElementStub::Generate(MacroAssembler* masm) {
   switch (elements_kind_) {
     case FAST_ELEMENTS:
-      KeyedStoreStubCompiler::GenerateStoreFastElement(masm, is_js_array_);
+    case FAST_SMI_ONLY_ELEMENTS: {
+      KeyedStoreStubCompiler::StoreObjectAction store_object_action =
+          elements_kind_ == FAST_SMI_ONLY_ELEMENTS
+              ? KeyedStoreStubCompiler::kObjectStoreForcesGeneric
+              : KeyedStoreStubCompiler::kObjectStoreCausesWriteBarrier;
+      KeyedStoreStubCompiler::GenerateStoreFastElement(masm,
+                                                       is_js_array_,
+                                                       store_object_action);
+    }
       break;
     case FAST_DOUBLE_ELEMENTS:
       KeyedStoreStubCompiler::GenerateStoreFastDoubleElement(masm,