Add map-based read barrier to WeakCell

src/ia32/macro-assembler-ia32.h

 // 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.
 
 #ifndef V8_IA32_MACRO_ASSEMBLER_IA32_H_
 #define V8_IA32_MACRO_ASSEMBLER_IA32_H_
 
 #include "src/assembler.h"
 #include "src/bailout-reason.h"
 #include "src/frames.h"
@@ skipping 280 matching lines @@
     if (object->IsHeapObject()) {
       CmpHeapObject(reg, Handle<HeapObject>::cast(object));
     } else {
       cmp(reg, Immediate(object));
     }
   }
 
   // Compare the given value and the value of weak cell.
   void CmpWeakValue(Register value, Handle<WeakCell> cell, Register scratch);
 
-  void GetWeakValue(Register value, Handle<WeakCell> cell);
+  void GetWeakValue(Register value, Register scratch, Handle<WeakCell> cell);
+
+  // Gets the given value without triggering the read barrier (you must
+  // immediately discard the value returned). You might want to use
+  // CmpWeakValue instead.
+  void GetWeakValueNoReadBarrier(Register value, Handle<WeakCell> cell);
 
   // Load the value of the weak cell in the value register. Branch to the given
   // miss label if the weak cell was cleared.
-  void LoadWeakValue(Register value, Handle<WeakCell> cell, Label* miss);
+  void LoadWeakValue(Register value, Handle<WeakCell> cell, Register scratch,
+                     Label* miss);
+
+  // Load the value of the weak cell in the value register. Branch to the given
+  // miss label if the weak cell was cleared.
+  void LoadWeakValueNoReadBarrier(Register value, Handle<WeakCell> cell,
+                                  Label* miss);
 
   // ---------------------------------------------------------------------------
   // JavaScript invokes
 
   // Invoke the JavaScript function code by either calling or jumping.
   void InvokeCode(Register code,
                   const ParameterCount& expected,
                   const ParameterCount& actual,
                   InvokeFlag flag,
                   const CallWrapper& call_wrapper) {
@@ skipping 777 matching lines @@
   }                                                                       \
   masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_IA32_MACRO_ASSEMBLER_IA32_H_