To fully support hydrogen code stubs which accept a variable number of arguments,

src/x64/lithium-x64.cc

 // 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 1824 matching lines @@
     // Register allocator doesn't (yet) support allocation of double
     // temps. Reserve xmm1 explicitly.
     LClampTToUint8* result = new(zone()) LClampTToUint8(reg,
                                                         FixedTemp(xmm1));
     return AssignEnvironment(DefineSameAsFirst(result));
   }
 }
 
 
 LInstruction* LChunkBuilder::DoReturn(HReturn* instr) {
-  return new(zone()) LReturn(UseFixed(instr->value(), rax));
+  LOperand* parameter_count = UseRegisterOrConstant(instr->parameter_count());
+  return new(zone()) LReturn(UseFixed(instr->value(), rax),
+                             parameter_count);
 }
 
 
 LInstruction* LChunkBuilder::DoConstant(HConstant* instr) {
   Representation r = instr->representation();
   if (r.IsInteger32()) {
     return DefineAsRegister(new(zone()) LConstantI);
   } else if (r.IsDouble()) {
     LOperand* temp = TempRegister();
     return DefineAsRegister(new(zone()) LConstantD(temp));
@@ skipping 572 matching lines @@
 LInstruction* LChunkBuilder::DoLoadFieldByIndex(HLoadFieldByIndex* instr) {
   LOperand* object = UseRegister(instr->object());
   LOperand* index = UseTempRegister(instr->index());
   return DefineSameAsFirst(new(zone()) LLoadFieldByIndex(object, index));
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64