Symbols for type cells.

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 2ef5a87da26eba19a5c4f9069bd90ebf8fef9633..bbb5aace17ec2ca5fd7b57241a4bf751de6f8684 100644
--- a/src/ia32/code-stubs-ia32.cc
+++ b/src/ia32/code-stubs-ia32.cc
@@ -2423,7 +2423,8 @@ static void GenerateRecordCallTarget(MacroAssembler* masm) {
 
 void CallFunctionStub::Generate(MacroAssembler* masm) {
   // ebx : feedback vector
-  // edx : (only if ebx is not undefined) slot in feedback vector (Smi)
+  // edx : (only if ebx is not the megamorphic symbol) slot in feedback
+  //       vector (Smi)
   // edi : the function to call
   Isolate* isolate = masm->isolate();
   Label slow, non_function, wrap, cont;
@@ -2481,7 +2482,7 @@ void CallFunctionStub::Generate(MacroAssembler* masm) {
     if (RecordCallTarget()) {
       // If there is a call target cache, mark it megamorphic in the
       // non-function case.  MegamorphicSentinel is an immortal immovable
-      // object (undefined) so no write barrier is needed.
+      // object (megamorphic symbol) so no write barrier is needed.
       __ mov(FieldOperand(ebx, edx, times_half_pointer_size,
                           FixedArray::kHeaderSize),
              Immediate(TypeFeedbackInfo::MegamorphicSentinel(isolate)));
@@ -2529,7 +2530,8 @@ void CallFunctionStub::Generate(MacroAssembler* masm) {
 void CallConstructStub::Generate(MacroAssembler* masm) {
   // eax : number of arguments
   // ebx : feedback vector
-  // edx : (only if ebx is not undefined) slot in feedback vector (Smi)
+  // edx : (only if ebx is not the megamorphic symbol) slot in feedback
+  //       vector (Smi)
   // edi : constructor function
   Label slow, non_function_call;
 
@@ -5152,15 +5154,14 @@ void ArrayConstructorStub::GenerateDispatchToArrayStub(
 void ArrayConstructorStub::Generate(MacroAssembler* masm) {
   // ----------- S t a t e -------------
   //  -- eax : argc (only if argument_count_ == ANY)
-  //  -- ebx : feedback vector (fixed array or undefined)
+  //  -- ebx : feedback vector (fixed array or megamorphic symbol)
   //  -- edx : slot index (if ebx is fixed array)
   //  -- edi : constructor
   //  -- esp[0] : return address
   //  -- esp[4] : last argument
   // -----------------------------------
-  Handle<Object> undefined_sentinel(
-      masm->isolate()->heap()->undefined_value(),
-      masm->isolate());
+  Handle<Object> megamorphic_sentinel =
+      TypeFeedbackInfo::MegamorphicSentinel(masm->isolate());
 
   if (FLAG_debug_code) {
     // The array construct code is only set for the global and natives
@@ -5174,24 +5175,26 @@ void ArrayConstructorStub::Generate(MacroAssembler* masm) {
     __ CmpObjectType(ecx, MAP_TYPE, ecx);
     __ Assert(equal, kUnexpectedInitialMapForArrayFunction);
 
-    // We should either have undefined in ebx or a valid fixed array.
+    // We should either have the megamorphic symbol in ebx or a valid
+    // fixed array.
     Label okay_here;
     Handle<Map> fixed_array_map = masm->isolate()->factory()->fixed_array_map();
-    __ cmp(ebx, Immediate(undefined_sentinel));
+    __ cmp(ebx, Immediate(megamorphic_sentinel));
     __ j(equal, &okay_here);
     __ cmp(FieldOperand(ebx, 0), Immediate(fixed_array_map));
     __ Assert(equal, kExpectedFixedArrayInRegisterEbx);
 
-    // edx should be a smi if we don't have undefined in ebx.
+    // edx should be a smi if we don't have the megamorphic symbol in ebx.
     __ AssertSmi(edx);
 
     __ bind(&okay_here);
   }
 
   Label no_info;
-  // If the feedback vector is undefined, or contains anything other than an
-  // AllocationSite, call an array constructor that doesn't use AllocationSites.
-  __ cmp(ebx, Immediate(undefined_sentinel));
+  // If the feedback vector is the megamorphic sentinel, or contains anything
+  // other than an AllocationSite, call an array constructor that doesn't use
+  // AllocationSites.
+  __ cmp(ebx, Immediate(megamorphic_sentinel));
   __ j(equal, &no_info);
   __ mov(ebx, FieldOperand(ebx, edx, times_half_pointer_size,
                            FixedArray::kHeaderSize));