Implement tracking and optimizations of packed arrays.

src/ia32/code-stubs-ia32.cc

Index: src/ia32/code-stubs-ia32.cc
diff --git a/src/ia32/code-stubs-ia32.cc b/src/ia32/code-stubs-ia32.cc
index 6cd02338977eb0e5086375074b8e24bbef8786f3..ae38d24e6f1aeb40c6a4cca098396f2c66479bad 100644
--- a/src/ia32/code-stubs-ia32.cc
+++ b/src/ia32/code-stubs-ia32.cc
@@ -7059,7 +7059,7 @@ static const AheadOfTimeWriteBarrierStubList kAheadOfTime[] = {
   // KeyedStoreStubCompiler::GenerateStoreFastElement.
   { REG(edi), REG(ebx), REG(ecx), EMIT_REMEMBERED_SET},
   { REG(edx), REG(edi), REG(ebx), EMIT_REMEMBERED_SET},
-  // ElementsTransitionGenerator::GenerateSmiOnlyToObject
+  // ElementsTransitionGenerator::GenerateMapChangeElementTransition
   // and ElementsTransitionGenerator::GenerateSmiOnlyToDouble
   // and ElementsTransitionGenerator::GenerateDoubleToObject
   { REG(edx), REG(ebx), REG(edi), EMIT_REMEMBERED_SET},
@@ -7332,7 +7332,7 @@ void StoreArrayLiteralElementStub::Generate(MacroAssembler* masm) {
 
   __ CheckFastElements(edi, &double_elements);
 
-  // FAST_SMI_ONLY_ELEMENTS or FAST_ELEMENTS
+  // Check for Smi-only or Object elements
   __ JumpIfSmi(eax, &smi_element);
   __ CheckFastSmiOnlyElements(edi, &fast_elements, Label::kNear);
 
@@ -7356,7 +7356,7 @@ void StoreArrayLiteralElementStub::Generate(MacroAssembler* masm) {
   __ pop(edx);
   __ jmp(&slow_elements);
 
-  // Array literal has ElementsKind of FAST_ELEMENTS and value is an object.
+  // Array literal has ElementsKind of FAST_*_ELEMENTS and value is an object.
   __ bind(&fast_elements);
   __ mov(ebx, FieldOperand(ebx, JSObject::kElementsOffset));
   __ lea(ecx, FieldOperand(ebx, ecx, times_half_pointer_size,
@@ -7369,8 +7369,7 @@ void StoreArrayLiteralElementStub::Generate(MacroAssembler* masm) {
                  OMIT_SMI_CHECK);
   __ ret(0);
 
-  // Array literal has ElementsKind of FAST_SMI_ONLY_ELEMENTS or
-  // FAST_ELEMENTS, and value is Smi.
+  // Array literal has ElementsKind of Smi-only or Object, and value is Smi.
   __ bind(&smi_element);
   __ mov(ebx, FieldOperand(ebx, JSObject::kElementsOffset));
   __ mov(FieldOperand(ebx, ecx, times_half_pointer_size,