Use a WeakCell in the CallIC type vector.

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 ca1afcda97d7b3b2ed6fa5e737149613294bcdcd..b7fa9aef445b0caa249930182ec75498b575d0a6 100644
--- a/src/ia32/code-stubs-ia32.cc
+++ b/src/ia32/code-stubs-ia32.cc
@@ -2245,10 +2245,30 @@ void CallICStub::Generate(MacroAssembler* masm) {
   ParameterCount actual(argc);
 
   // The checks. First, does edi match the recorded monomorphic target?
-  __ cmp(edi, FieldOperand(ebx, edx, times_half_pointer_size,
+  __ mov(ecx, FieldOperand(ebx, edx, times_half_pointer_size,
                            FixedArray::kHeaderSize));
+
+  // We don't know that we have a weak cell. We might have a private symbol
+  // or an AllocationSite, but the memory is safe to examine.
+  // AllocationSite::kTransitionInfoOffset - contains a Smi or pointer to
+  // FixedArray.
+  // WeakCell::kValueOffset - contains a JSFunction or Smi(0)
+  // Symbol::kHashFieldSlot - if the low bit is 1, then the hash is not
+  // computed, meaning that it can't appear to be a pointer. If the low bit is
+  // 0, then hash is computed, but the 0 bit prevents the field from appearing
+  // to be a pointer.
+  STATIC_ASSERT(WeakCell::kSize >= kPointerSize);
+  STATIC_ASSERT(AllocationSite::kTransitionInfoOffset ==
+                    WeakCell::kValueOffset &&
+                WeakCell::kValueOffset == Symbol::kHashFieldSlot);
+
+  __ cmp(edi, FieldOperand(ecx, WeakCell::kValueOffset));
   __ j(not_equal, &extra_checks_or_miss);
 
+  // The compare above could have been a SMI/SMI comparison. Guard against this
+  // convincing us that we have a monomorphic JSFunction.
+  __ JumpIfSmi(edi, &extra_checks_or_miss);
+
   __ bind(&have_js_function);
   if (CallAsMethod()) {
     EmitContinueIfStrictOrNative(masm, &cont);
@@ -2277,8 +2297,6 @@ void CallICStub::Generate(MacroAssembler* masm) {
   __ bind(&extra_checks_or_miss);
   Label uninitialized, miss;
 
-  __ mov(ecx, FieldOperand(ebx, edx, times_half_pointer_size,
-                           FixedArray::kHeaderSize));
   __ cmp(ecx, Immediate(TypeFeedbackVector::MegamorphicSentinel(isolate)));
   __ j(equal, &slow_start);
 
@@ -2322,15 +2340,18 @@ void CallICStub::Generate(MacroAssembler* masm) {
   // Update stats.
   __ add(FieldOperand(ebx, with_types_offset), Immediate(Smi::FromInt(1)));
 
-  // Store the function.
-  __ mov(
-      FieldOperand(ebx, edx, times_half_pointer_size, FixedArray::kHeaderSize),
-      edi);
+  // Store the function. Use a stub since we need a frame for allocation.
+  // ebx - vector
+  // edx - slot
+  // edi - function
+  {
+    FrameScope scope(masm, StackFrame::INTERNAL);
+    CreateWeakCellStub create_stub(isolate);
+    __ push(edi);
+    __ CallStub(&create_stub);
+    __ pop(edi);
+  }
 
-  // Update the write barrier.
-  __ mov(eax, edi);
-  __ RecordWriteArray(ebx, eax, edx, kDontSaveFPRegs, EMIT_REMEMBERED_SET,
-                      OMIT_SMI_CHECK);
   __ jmp(&have_js_function);
 
   // We are here because tracing is on or we encountered a MISS case we can't
@@ -2393,6 +2414,7 @@ void CodeStub::GenerateStubsAheadOfTime(Isolate* isolate) {
   // It is important that the store buffer overflow stubs are generated first.
   ArrayConstructorStubBase::GenerateStubsAheadOfTime(isolate);
   CreateAllocationSiteStub::GenerateAheadOfTime(isolate);
+  CreateWeakCellStub::GenerateAheadOfTime(isolate);
   BinaryOpICStub::GenerateAheadOfTime(isolate);
   BinaryOpICWithAllocationSiteStub::GenerateAheadOfTime(isolate);
 }