NumberUntagD is faster when untagging in a temp register

src/ia32/lithium-ia32.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
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 //
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@@ skipping 1915 matching lines @@
     from = Representation::Tagged();
   }
   // Only mark conversions that might need to allocate as calling rather than
   // all changes. This makes simple, non-allocating conversion not have to force
   // building a stack frame.
   if (from.IsTagged()) {
     if (to.IsDouble()) {
       info()->MarkAsDeferredCalling();
       LOperand* value = UseRegister(instr->value());
       // Temp register only necessary for minus zero check.
-      LOperand* temp = instr->deoptimize_on_minus_zero()
-                       ? TempRegister()
-                       : NULL;
+      LOperand* temp = TempRegister();

[ulan, 2013/09/12 08:35:04]

Doesn't this increase register pressure?

       LNumberUntagD* res = new(zone()) LNumberUntagD(value, temp);
       return AssignEnvironment(DefineAsRegister(res));
     } else if (to.IsSmi()) {
       HValue* val = instr->value();
       LOperand* value = UseRegister(val);
       if (val->type().IsSmi()) {
         return DefineSameAsFirst(new(zone()) LDummyUse(value));
       }
       return AssignEnvironment(DefineSameAsFirst(new(zone()) LCheckSmi(value)));
     } else {
@@ skipping 785 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_IA32