Improve polymorphic loads on single slots.

src/x64/lithium-x64.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 53 matching lines @@
   V(CallFunction)                               \
   V(CallGlobal)                                 \
   V(CallKeyed)                                  \
   V(CallKnownGlobal)                            \
   V(CallNamed)                                  \
   V(CallNew)                                    \
   V(CallRuntime)                                \
   V(CallStub)                                   \
   V(CheckFunction)                              \
   V(CheckInstanceType)                          \
-  V(CheckMap)                                   \
+  V(CheckMaps)                                  \
   V(CheckNonSmi)                                \
   V(CheckPrototypeMaps)                         \
   V(CheckSmi)                                   \
   V(ClampDToUint8)                              \
   V(ClampIToUint8)                              \
   V(ClampTToUint8)                              \
   V(ClassOfTestAndBranch)                       \
   V(CmpConstantEqAndBranch)                     \
   V(CmpIDAndBranch)                             \
   V(CmpObjectEqAndBranch)                       \
@@ skipping 1733 matching lines @@
  public:
   explicit LCheckInstanceType(LOperand* value) {
     inputs_[0] = value;
   }
 
   DECLARE_CONCRETE_INSTRUCTION(CheckInstanceType, "check-instance-type")
   DECLARE_HYDROGEN_ACCESSOR(CheckInstanceType)
 };
 
 
-class LCheckMap: public LTemplateInstruction<0, 1, 0> {
+class LCheckMaps: public LTemplateInstruction<0, 1, 0> {
  public:
-  explicit LCheckMap(LOperand* value) {
+  explicit LCheckMaps(LOperand* value) {
     inputs_[0] = value;
   }
 
-  DECLARE_CONCRETE_INSTRUCTION(CheckMap, "check-map")
-  DECLARE_HYDROGEN_ACCESSOR(CheckMap)
+  DECLARE_CONCRETE_INSTRUCTION(CheckMaps, "check-maps")
+  DECLARE_HYDROGEN_ACCESSOR(CheckMaps)
 };
 
 
 class LCheckPrototypeMaps: public LTemplateInstruction<0, 0, 1> {
  public:
   explicit LCheckPrototypeMaps(LOperand* temp)  {
     temps_[0] = temp;
   }
 
   DECLARE_CONCRETE_INSTRUCTION(CheckPrototypeMaps, "check-prototype-maps")
@@ skipping 491 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(LChunkBuilder);
 };
 
 #undef DECLARE_HYDROGEN_ACCESSOR
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::int
 
 #endif  // V8_X64_LITHIUM_X64_H_