Use weak cell to embed known map in CompareIC

src/x64/code-stubs-x64.cc

 // Copyright 2013 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/bootstrapper.h"
 #include "src/code-stubs.h"
@@ skipping 3700 matching lines @@
   __ subp(rax, rdx);
   __ ret(0);
 
   __ bind(&miss);
   GenerateMiss(masm);
 }
 
 
 void CompareICStub::GenerateKnownObjects(MacroAssembler* masm) {
   Label miss;
+  Handle<WeakCell> cell = Map::WeakCellForMap(known_map_);
   Condition either_smi = masm->CheckEitherSmi(rdx, rax);
   __ j(either_smi, &miss, Label::kNear);
 
+  __ GetWeakValue(rdi, cell);
   __ movp(rcx, FieldOperand(rax, HeapObject::kMapOffset));
   __ movp(rbx, FieldOperand(rdx, HeapObject::kMapOffset));
-  __ Cmp(rcx, known_map_);
+  __ cmpp(rcx, rdi);
   __ j(not_equal, &miss, Label::kNear);
-  __ Cmp(rbx, known_map_);
+  __ cmpp(rbx, rdi);
   __ j(not_equal, &miss, Label::kNear);
 
   __ subp(rax, rdx);
   __ ret(0);
 
   __ bind(&miss);
   GenerateMiss(masm);
 }
 
 
@@ skipping 1295 matching lines @@
   CallApiFunctionAndReturn(masm, api_function_address, thunk_ref, getter_arg,
                            kStackSpace, nullptr, return_value_operand, NULL);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64