Improve polymorphic loads on single slots.

src/ia32/lithium-ia32.h

 // 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 48 matching lines @@
   V(CallGlobal)                                 \
   V(CallKeyed)                                  \
   V(CallKnownGlobal)                            \
   V(CallNamed)                                  \
   V(CallNew)                                    \
   V(CallRuntime)                                \
   V(CallStub)                                   \
   V(CheckFunction)                              \
   V(CheckInstanceType)                          \
   V(CheckMap)                                   \
+  V(CheckMapSet)                                \
   V(CheckNonSmi)                                \
   V(CheckPrototypeMaps)                         \
   V(CheckSmi)                                   \
   V(ClampDToUint8)                              \
   V(ClampIToUint8)                              \
   V(ClampTToUint8)                              \
   V(ClassOfTestAndBranch)                       \
   V(CmpIDAndBranch)                             \
   V(CmpObjectEqAndBranch)                       \
   V(CmpMapAndBranch)                            \
@@ skipping 1839 matching lines @@
  public:
   explicit LCheckMap(LOperand* value) {
     inputs_[0] = value;
   }
 
   DECLARE_CONCRETE_INSTRUCTION(CheckMap, "check-map")
   DECLARE_HYDROGEN_ACCESSOR(CheckMap)
 };
 
 
+class LCheckMapSet: public LTemplateInstruction<0, 1, 0> {
+ public:
+  explicit LCheckMapSet(LOperand* value) {
+    inputs_[0] = value;
+  }
+
+  DECLARE_CONCRETE_INSTRUCTION(CheckMapSet, "check-map-set")
+  DECLARE_HYDROGEN_ACCESSOR(CheckMapSet)
+};
+
+
 class LCheckPrototypeMaps: public LTemplateInstruction<0, 0, 1> {
  public:
   explicit LCheckPrototypeMaps(LOperand* temp)  {
     temps_[0] = temp;
   }
 
   DECLARE_CONCRETE_INSTRUCTION(CheckPrototypeMaps, "check-prototype-maps")
   DECLARE_HYDROGEN_ACCESSOR(CheckPrototypeMaps)
 
   Handle<JSObject> prototype() const { return hydrogen()->prototype(); }
@@ skipping 536 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(LChunkBuilder);
 };
 
 #undef DECLARE_HYDROGEN_ACCESSOR
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_IA32_LITHIUM_IA32_H_