Use a WeakCell in the CallIC type vector.

src/x64/interface-descriptors-x64.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/interface-descriptors.h"
 
@@ skipping 83 matching lines @@
 void FastCloneShallowObjectDescriptor::Initialize(
     CallInterfaceDescriptorData* data) {
   Register registers[] = {rsi, rax, rbx, rcx, rdx};
   data->Initialize(arraysize(registers), registers, NULL);
 }
 
 
 void CreateAllocationSiteDescriptor::Initialize(
     CallInterfaceDescriptorData* data) {
   Register registers[] = {rsi, rbx, rdx};
-  data->Initialize(arraysize(registers), registers, NULL);
+  Representation representations[] = {Representation::Tagged(),
+                                      Representation::Tagged(),
+                                      Representation::Smi()};
+  data->Initialize(arraysize(registers), registers, representations);
 }
 
 
+void CreateWeakCellDescriptor::Initialize(CallInterfaceDescriptorData* data) {
+  Register registers[] = {rsi, rbx, rdx, rdi};
+  Representation representations[] = {
+      Representation::Tagged(), Representation::Tagged(), Representation::Smi(),
+      Representation::Tagged()};
+  data->Initialize(arraysize(registers), registers, representations);
+}
+
+
 void StoreArrayLiteralElementDescriptor::Initialize(
     CallInterfaceDescriptorData* data) {
   Register registers[] = {rsi, rcx, rax};
   data->Initialize(arraysize(registers), registers, NULL);
 }
 
 
 void CallFunctionDescriptor::Initialize(CallInterfaceDescriptorData* data) {
   Register registers[] = {rsi, rdi};
   data->Initialize(arraysize(registers), registers, NULL);
@@ skipping 221 matching lines @@
       Representation::Tagged(),    // call_data
       Representation::Tagged(),    // holder
       Representation::External(),  // api_function_address
   };
   data->Initialize(arraysize(registers), registers, representations);
 }
 }
 }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64