[llvm-commits] CVS: llvm/lib/Transforms/Scalar/InstructionCombining.cpp

[Chris Lattner]

>>> @@ -5681,7 +5677,7 @@
>>>  /// evaluate the expression.
>>>  Value *InstCombiner::EvaluateInDifferentType(Value *V, const Type
>>> *Ty) {
>>>    if (Constant *C = dyn_cast<Constant>(V))
>>> -    return ConstantExpr::getCast(C, Ty);
>>> +    return ConstantExpr::getIntegerCast(C, Ty, C->getType()-
>>>> isSigned());
>>
>> This looks extremely unsafe.  Why is it ok?
>
> The only place EvaluateInDifferentType is called is from
> commonIntCastTransforms. Those casts are guaranteed to only involve
> integer operands. Therefore, the only kind of cast that could be
> involved is an integer cast.
>
> What looks "extremely" unsafe about it?

I'm specifically concerned that there is nothing controlling whether  
a zext or sext gets generated other than C->getType()->isSigned(),  
which I'm not convinced is the right thing.  Getting the wrong one is  
bad :)

-Chris