Simplify Hydrogen code stubs with variable argument count

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 2395 matching lines @@
 LInstruction* LChunkBuilder::DoParameter(HParameter* instr) {
   LParameter* result = new(zone()) LParameter;
   if (instr->kind() == HParameter::STACK_PARAMETER) {
     int spill_index = chunk()->GetParameterStackSlot(instr->index());
     return DefineAsSpilled(result, spill_index);
   } else {
     ASSERT(info()->IsStub());
     CodeStubInterfaceDescriptor* descriptor =
         info()->code_stub()->GetInterfaceDescriptor(info()->isolate());
     int index = static_cast<int>(instr->index());
-    Register reg = DESCRIPTOR_GET_PARAMETER_REGISTER(descriptor, index);
+    Register reg = descriptor->GetParameterRegister(index);
     return DefineFixed(result, reg);
   }
 }
 
 
 LInstruction* LChunkBuilder::DoUnknownOSRValue(HUnknownOSRValue* instr) {
   // Use an index that corresponds to the location in the unoptimized frame,
   // which the optimized frame will subsume.
   int env_index = instr->index();
   int spill_index = 0;
@@ skipping 175 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