Make the runtime entry for setting/changing accessors "atomic".

src/mips/full-codegen-mips.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1482 matching lines @@
         } else {
           __ Drop(3);
         }
         break;
       case ObjectLiteral::Property::GETTER:
       case ObjectLiteral::Property::SETTER:
         // Duplicate receiver on stack.
         __ lw(a0, MemOperand(sp));
         __ push(a0);
         VisitForStackValue(key);
-        __ li(a1, Operand(property->kind() == ObjectLiteral::Property::SETTER ?
-                           Smi::FromInt(1) :
-                           Smi::FromInt(0)));
-        __ push(a1);
-        VisitForStackValue(value);
+        if (property->kind() == ObjectLiteral::Property::GETTER) {
+          VisitForStackValue(value);
+          __ LoadRoot(a1, Heap::kNullValueRootIndex);
+          __ push(a1);
+        } else {
+          __ LoadRoot(a1, Heap::kNullValueRootIndex);
+          __ push(a1);
+          VisitForStackValue(value);
+        }
         __ li(a0, Operand(Smi::FromInt(NONE)));
         __ push(a0);
         __ CallRuntime(Runtime::kDefineOrRedefineAccessorProperty, 5);
         break;
     }
   }
 
   if (expr->has_function()) {
     ASSERT(result_saved);
     __ lw(a0, MemOperand(sp));
@@ skipping 2912 matching lines @@
   *context_length = 0;
   return previous_;
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_MIPS