Remove the redundant load on every context lookup.

src/ia32/lithium-ia32.cc

Index: src/ia32/lithium-ia32.cc
diff --git a/src/ia32/lithium-ia32.cc b/src/ia32/lithium-ia32.cc
index 1d5cefcb4996e7e0fa1f5a0e2263854a555937b3..21cfcc6b9a0df3601b9737a0ab6767f09e191713 100644
--- a/src/ia32/lithium-ia32.cc
+++ b/src/ia32/lithium-ia32.cc
@@ -1685,14 +1685,16 @@ LInstruction* LChunkBuilder::DoLoadContextSlot(HLoadContextSlot* instr) {
 
 
 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 {
-    value = UseRegister(instr->value());
+    context = UseRegisterAtStart(instr->context());
+    value = UseRegisterAtStart(instr->value());

[fschneider, 2011/02/04 11:29:58]

This is perfectly valid, but i think the AtStart will not have any benefit since
there are no temps or result registers here.

[Kevin Millikin (Chromium), 2011/02/04 11:51:48]

I was trying to be consistent, but I guess UseRegister is a safer default so
I'll switch to that.

     temp = NULL;
   }
   return new LStoreContextSlot(context, value, temp);