Lithium: avoid registers for constants when possible.

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 2656 matching lines @@
   MUST_USE_RESULT LOperand* UseAtStart(HValue* value);
 
   // An input operand in a register, stack slot or a constant operand.
   MUST_USE_RESULT LOperand* UseOrConstant(HValue* value);
   MUST_USE_RESULT LOperand* UseOrConstantAtStart(HValue* value);
 
   // An input operand in a register or a constant operand.
   MUST_USE_RESULT LOperand* UseRegisterOrConstant(HValue* value);
   MUST_USE_RESULT LOperand* UseRegisterOrConstantAtStart(HValue* value);
 
+  // An input operand in a constant operand.
+  MUST_USE_RESULT LOperand* UseConstant(HValue* value);
+
   // An input operand in register, stack slot or a constant operand.
   // Will not be moved to a register even if one is freely available.
   MUST_USE_RESULT LOperand* UseAny(HValue* value);
 
   // Temporary operand that must be in a register.
   MUST_USE_RESULT LUnallocated* TempRegister();
   MUST_USE_RESULT LOperand* FixedTemp(Register reg);
   MUST_USE_RESULT LOperand* FixedTemp(XMMRegister reg);
 
   // Methods for setting up define-use relationships.
@@ skipping 59 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(LChunkBuilder);
 };
 
 #undef DECLARE_HYDROGEN_ACCESSOR
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::int
 
 #endif  // V8_X64_LITHIUM_X64_H_