Change the x64 optimizing compiler to stop using the fixed context register rsi.

src/x64/lithium-codegen-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 156 matching lines @@
                        RelocInfo::Mode mode,
                        LInstruction* instr,
                        SafepointMode safepoint_mode,
                        int argc);
 
 
   void CallCode(Handle<Code> code,
                 RelocInfo::Mode mode,
                 LInstruction* instr);
 
+  // CallRuntime assumes that the context is already in rsi.
   void CallRuntime(const Runtime::Function* function,
                    int num_arguments,
                    LInstruction* instr);
 
   void CallRuntime(Runtime::FunctionId id,
                    int num_arguments,
                    LInstruction* instr) {
     const Runtime::Function* function = Runtime::FunctionForId(id);
     CallRuntime(function, num_arguments, instr);
   }
 
+  // Call runtime from deferred code, where the context has not yet been
+  // moved to rsi.
   void CallRuntimeFromDeferred(Runtime::FunctionId id,
                                int argc,
-                               LInstruction* instr);
+                               LInstruction* instr,
+                               LOperand* context);
 
 
   // Generate a direct call to a known function.  Expects the function
   // to be in edi.
   void CallKnownFunction(Handle<JSFunction> function,
                          int arity,
                          LInstruction* instr,
                          CallKind call_kind);
 
   void LoadHeapObject(Register result, Handle<HeapObject> object);
@@ skipping 162 matching lines @@
  private:
   LCodeGen* codegen_;
   Label entry_;
   Label exit_;
   Label* external_exit_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_LITHIUM_CODEGEN_X64_H_