X64 Crankshaft: Implement LValueOf and (dummy) LArgumentsObject.

src/arm/lithium-arm.cc

 // 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 1900 matching lines @@
 }
 
 
 LInstruction* LChunkBuilder::DoCallStub(HCallStub* instr) {
   argument_count_ -= instr->argument_count();
   return MarkAsCall(DefineFixed(new LCallStub, r0), instr);
 }
 
 
 LInstruction* LChunkBuilder::DoArgumentsObject(HArgumentsObject* instr) {
-  // There are no real uses of the arguments object (we bail out in all other
-  // cases).
+  // There are no real uses of the arguments object.
+  // arguments.length and element access are supported directly on
+  // stack arguments, and any real arguments object use causes a bailout.
+  // So this value is never used.
   return NULL;
 }
 
 
 LInstruction* LChunkBuilder::DoAccessArgumentsAt(HAccessArgumentsAt* instr) {
   LOperand* arguments = UseRegister(instr->arguments());
   LOperand* length = UseTempRegister(instr->length());
   LOperand* index = UseRegister(instr->index());
   LAccessArgumentsAt* result = new LAccessArgumentsAt(arguments, length, index);
   return AssignEnvironment(DefineAsRegister(result));
@@ skipping 68 matching lines @@
 
 
 LInstruction* LChunkBuilder::DoLeaveInlined(HLeaveInlined* instr) {
   HEnvironment* outer = current_block_->last_environment()->outer();
   current_block_->UpdateEnvironment(outer);
   return NULL;
 }
 
 
 } }  // namespace v8::internal