Add HLoadRoot hydrogen instruction.

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 102 matching lines @@
   V(IsConstructCallAndBranch)                   \
   V(IsObjectAndBranch)                          \
   V(IsStringAndBranch)                          \
   V(IsSmiAndBranch)                             \
   V(IsNumberAndBranch)                          \
   V(IsUndetectableAndBranch)                    \
   V(Label)                                      \
   V(LazyBailout)                                \
   V(LoadContextSlot)                            \
   V(LoadExternalArrayPointer)                   \
+  V(LoadRoot)                                   \
   V(LoadFieldByIndex)                           \
   V(LoadFunctionPrototype)                      \
   V(LoadGlobalCell)                             \
   V(LoadGlobalGeneric)                          \
   V(LoadKeyed)                                  \
   V(LoadKeyedGeneric)                           \
   V(LoadNamedField)                             \
   V(LoadNamedGeneric)                           \
   V(MapEnumLength)                              \
   V(MathAbs)                                    \
@@ skipping 1395 matching lines @@
     inputs_[0] = function;
   }
 
   DECLARE_CONCRETE_INSTRUCTION(LoadFunctionPrototype, "load-function-prototype")
   DECLARE_HYDROGEN_ACCESSOR(LoadFunctionPrototype)
 
   LOperand* function() { return inputs_[0]; }
 };
 
 
+class LLoadRoot V8_FINAL : public LTemplateInstruction<1, 0, 0> {
+ public:
+  DECLARE_CONCRETE_INSTRUCTION(LoadRoot, "load-root")
+  DECLARE_HYDROGEN_ACCESSOR(LoadRoot)
+
+  Heap::RootListIndex index() const { return hydrogen()->index(); }
+};
+
+
 class LLoadExternalArrayPointer V8_FINAL
     : public LTemplateInstruction<1, 1, 0> {
  public:
   explicit LLoadExternalArrayPointer(LOperand* object) {
     inputs_[0] = object;
   }
 
   LOperand* object() { return inputs_[0]; }
 
   DECLARE_CONCRETE_INSTRUCTION(LoadExternalArrayPointer,
@@ skipping 1171 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(LChunkBuilder);
 };
 
 #undef DECLARE_HYDROGEN_ACCESSOR
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::int
 
 #endif  // V8_X64_LITHIUM_X64_H_