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

src/x64/lithium-x64.cc

Index: src/x64/lithium-x64.cc
===================================================================
--- src/x64/lithium-x64.cc	(revision 7071)
+++ src/x64/lithium-x64.cc	(working copy)
@@ -1728,14 +1728,17 @@
 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);
 }