X64 Crankshaft: Revert r7071 and fix DoStoreContextSlot in a different way.

src/x64/lithium-x64.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
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@@ skipping 1710 matching lines @@
 
 LInstruction* LChunkBuilder::DoLoadContextSlot(HLoadContextSlot* instr) {
   LOperand* context = UseRegisterAtStart(instr->value());
   return DefineAsRegister(new LLoadContextSlot(context));
 }
 
 
 LInstruction* LChunkBuilder::DoStoreContextSlot(HStoreContextSlot* instr) {
   LOperand* context;
   LOperand* value;
+  LOperand* temp;
   if (instr->NeedsWriteBarrier()) {
     context = UseTempRegister(instr->context());
     value = UseTempRegister(instr->value());
+    temp = TempRegister();

[Rico, 2011/03/07 11:19:21]

Do we gain anything from not just initializing temp to TempRegister in all
cases?

[William Hesse, 2011/03/07 11:44:31]

We do not allocate a temp register, and thus do not possible spill a register.

   } else {
     context = UseRegister(instr->context());
     value = UseRegister(instr->value());
+    temp = NULL;
   }
-  return new LStoreContextSlot(context, value);
+  return new LStoreContextSlot(context, value, temp);
 }
 
 
 LInstruction* LChunkBuilder::DoLoadNamedField(HLoadNamedField* instr) {
   ASSERT(instr->representation().IsTagged());
   LOperand* obj = UseRegisterAtStart(instr->object());
   return DefineAsRegister(new LLoadNamedField(obj));
 }
 
 
@@ skipping 285 matching lines @@
 
 LInstruction* LChunkBuilder::DoLeaveInlined(HLeaveInlined* instr) {
   HEnvironment* outer = current_block_->last_environment()->outer();
   current_block_->UpdateEnvironment(outer);
   return NULL;
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64