Make map check in NamedStoreHandlerCompiler::GenerateFieldTypeChecks weak.

src/ic/x64/handler-compiler-x64.cc

 // Copyright 2014 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/ic/call-optimization.h"
 #include "src/ic/handler-compiler.h"
@@ skipping 359 matching lines @@
   __ movp(scratch,
           FieldOperand(scratch, DescriptorArray::GetValueOffset(descriptor)));
   __ cmpp(value_reg, scratch);
   __ j(not_equal, miss_label);
 }
 
 
 void NamedStoreHandlerCompiler::GenerateFieldTypeChecks(HeapType* field_type,
                                                         Register value_reg,
                                                         Label* miss_label) {
+  Register map_reg = scratch1();
+  Register scratch = scratch2();
+  DCHECK(!value_reg.is(map_reg));
+  DCHECK(!value_reg.is(scratch));
   __ JumpIfSmi(value_reg, miss_label);
   HeapType::Iterator<Map> it = field_type->Classes();
   if (!it.Done()) {
     Label do_store;
+    __ movp(map_reg, FieldOperand(value_reg, HeapObject::kMapOffset));
     while (true) {
-      __ CompareMap(value_reg, it.Current());
+      __ CmpWeakValue(map_reg, Map::WeakCellForMap(it.Current()), scratch);
       it.Advance();
       if (it.Done()) {
         __ j(not_equal, miss_label);
         break;
       }
       __ j(equal, &do_store, Label::kNear);
     }
     __ bind(&do_store);
   }
 }
@@ skipping 341 matching lines @@
   // Return the generated code.
   return GetCode(kind(), Code::NORMAL, name);
 }
 
 
 #undef __
 }
 }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64