Code cleanup in GenerateRecordCallTarget.

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 c640a29c10db12c9959479b72d4b8f7afabeb89e..910c8253e1d89ab31c9c5c97ed6c64920d59a696 100644
--- a/src/ia32/code-stubs-ia32.cc
+++ b/src/ia32/code-stubs-ia32.cc
@@ -1920,7 +1920,7 @@ static void CallStubInRecordCallTarget(MacroAssembler* masm, CodeStub* stub) {
   // edi : the function to call
   FrameScope scope(masm, StackFrame::INTERNAL);
 
-  // Arguments register must be smi-tagged to call out.
+  // Number-of-arguments register must be smi-tagged to call out.
   __ SmiTag(eax);
   __ push(eax);
   __ push(edi);
@@ -1954,16 +1954,19 @@ static void GenerateRecordCallTarget(MacroAssembler* masm) {
 
   // A monomorphic cache hit or an already megamorphic state: invoke the
   // function without changing the state.
+  // We don't know if ecx is a WeakCell or a Symbol, but it's harmless to read
+  // at this position in a symbol (see static asserts in
+  // type-feedback-vector.h).
   Label check_allocation_site;
   __ cmp(edi, FieldOperand(ecx, WeakCell::kValueOffset));
   __ j(equal, &done, Label::kFar);
   __ CompareRoot(ecx, Heap::kmegamorphic_symbolRootIndex);
   __ j(equal, &done, Label::kFar);
-  __ CompareRoot(FieldOperand(ecx, 0), Heap::kWeakCellMapRootIndex);
+  __ CompareRoot(FieldOperand(ecx, HeapObject::kMapOffset),
+                 Heap::kWeakCellMapRootIndex);
   __ j(not_equal, FLAG_pretenuring_call_new ? &miss : &check_allocation_site);
 
-  // If edi is not equal to the weak cell value, and the weak cell value is
-  // cleared, we have a new chance to become monomorphic.
+  // If the weak cell is cleared, we have a new chance to become monomorphic.
   __ JumpIfSmi(FieldOperand(ecx, WeakCell::kValueOffset), &initialize);
   __ jmp(&megamorphic);
 
@@ -1972,7 +1975,7 @@ static void GenerateRecordCallTarget(MacroAssembler* masm) {
     // If we came here, we need to see if we are the array function.
     // If we didn't have a matching function, and we didn't find the megamorph
     // sentinel, then we have in the slot either some other function or an
-    // AllocationSite. Do a map check on the object in ecx.
+    // AllocationSite.
     __ CompareRoot(FieldOperand(ecx, 0), Heap::kAllocationSiteMapRootIndex);
     __ j(not_equal, &miss);