Remove the redundant load on every context lookup.

src/ia32/lithium-ia32.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 1667 matching lines @@
 }
 
 
 LInstruction* LChunkBuilder::DoLoadContextSlot(HLoadContextSlot* instr) {
   LOperand* context = UseRegisterAtStart(instr->value());
   return DefineAsRegister(new LLoadContextSlot(context));
 }
 
 
 LInstruction* LChunkBuilder::DoStoreContextSlot(HStoreContextSlot* instr) {
-  LOperand* context = UseTempRegister(instr->context());
+  LOperand* context;
   LOperand* value;
   LOperand* temp;
   if (instr->NeedsWriteBarrier()) {
+    context = UseTempRegister(instr->context());
     value = UseTempRegister(instr->value());
     temp = TempRegister();
   } else {
+    context = UseRegister(instr->context());
     value = UseRegister(instr->value());
     temp = NULL;
   }
   return new LStoreContextSlot(context, value, temp);
 }
 
 
 LInstruction* LChunkBuilder::DoLoadNamedField(HLoadNamedField* instr) {
   ASSERT(instr->representation().IsTagged());
   LOperand* obj = UseRegisterAtStart(instr->object());
@@ skipping 250 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_IA32