Use weak cells in map checks in polymorphic ICs.

src/ic/x64/ic-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/ic.h"
 #include "src/ic/ic-compiler.h"
@@ skipping 89 matching lines @@
   // Polymorphic keyed stores may use the map register
   Register map_reg = scratch1();
   DCHECK(kind() != Code::KEYED_STORE_IC ||
          map_reg.is(ElementTransitionAndStoreDescriptor::MapRegister()));
   __ movp(map_reg, FieldOperand(receiver(), HeapObject::kMapOffset));
   int receiver_count = types->length();
   int number_of_handled_maps = 0;
   for (int current = 0; current < receiver_count; ++current) {
     Handle<HeapType> type = types->at(current);
     Handle<Map> map = IC::TypeToMap(*type, isolate());
+    Handle<WeakCell> cell = Map::WeakCellForMap(map);
     if (!map->is_deprecated()) {
       number_of_handled_maps++;
       // Check map and tail call if there's a match
-      __ Cmp(map_reg, map);
+      __ CmpWeakValue(map_reg, scratch2(), cell);
       if (type->Is(HeapType::Number())) {
         DCHECK(!number_case.is_unused());
         __ bind(&number_case);
       }
       __ j(equal, handlers->at(current), RelocInfo::CODE_TARGET);
     }
   }
   DCHECK(number_of_handled_maps > 0);
 
   __ bind(&miss);
   TailCallBuiltin(masm(), MissBuiltin(kind()));
 
   // Return the generated code.
   InlineCacheState state =
       number_of_handled_maps > 1 ? POLYMORPHIC : MONOMORPHIC;
   return GetCode(kind(), type, name, state);
 }
 
 
 #undef __
 }
 }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64