Introduce a hydrogen value for contexts, support context slot assignment.

src/x64/lithium-x64.h

 // 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 1262 matching lines @@
  public:
   explicit LStoreGlobal(LOperand* value) {
     inputs_[0] = value;
   }
 
   DECLARE_CONCRETE_INSTRUCTION(StoreGlobal, "store-global")
   DECLARE_HYDROGEN_ACCESSOR(StoreGlobal)
 };
 
 
-class LLoadContextSlot: public LTemplateInstruction<1, 0, 0> {
+class LLoadContextSlot: public LTemplateInstruction<1, 1, 0> {
  public:
+  explicit LLoadContextSlot(LOperand* context) {
+    inputs_[0] = context;
+  }
+
   DECLARE_CONCRETE_INSTRUCTION(LoadContextSlot, "load-context-slot")
   DECLARE_HYDROGEN_ACCESSOR(LoadContextSlot)
 
-  int context_chain_length() { return hydrogen()->context_chain_length(); }
+  LOperand* context() { return InputAt(0); }
   int slot_index() { return hydrogen()->slot_index(); }
 
   virtual void PrintDataTo(StringStream* stream);
 };
 
 
 class LPushArgument: public LTemplateInstruction<0, 1, 0> {
  public:
   explicit LPushArgument(LOperand* value) {
     inputs_[0] = value;
@@ skipping 688 matching lines @@
   DISALLOW_COPY_AND_ASSIGN(LChunkBuilder);
 };
 
 #undef DECLARE_HYDROGEN_ACCESSOR
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::int
 
 #endif  // V8_X64_LITHIUM_X64_H_