Simplify CheckPrototypeMaps.

src/ia32/lithium-codegen-ia32.cc

 // Copyright 2011 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 3137 matching lines @@
   } else {
     __ mov(result, prototype);
   }
 }
 
 
 void LCodeGen::DoCheckPrototypeMaps(LCheckPrototypeMaps* instr) {
   Register reg = ToRegister(instr->temp());
 
   Handle<JSObject> holder = instr->holder();
-  Handle<Map> receiver_map = instr->receiver_map();
-  Handle<JSObject> current_prototype(JSObject::cast(receiver_map->prototype()));
+  Handle<JSObject> current_prototype = instr->prototype();
 
   // Load prototype object.
   LoadPrototype(reg, current_prototype);
 
   // Check prototype maps up to the holder.
   while (!current_prototype.is_identical_to(holder)) {
     __ cmp(FieldOperand(reg, HeapObject::kMapOffset),
            Handle<Map>(current_prototype->map()));
     DeoptimizeIf(not_equal, instr->environment());
     current_prototype =
@@ skipping 306 matching lines @@
   ASSERT(!environment->HasBeenRegistered());
   RegisterEnvironmentForDeoptimization(environment);
   ASSERT(osr_pc_offset_ == -1);
   osr_pc_offset_ = masm()->pc_offset();
 }
 
 
 #undef __
 
 } }  // namespace v8::internal