[LLVMdev] ConstantFold 'undef xor undef'

[Chris Lattner]

On Jul 7, 2010, at 8:45 AM, Jianzhou Zhao wrote:

>> 
>> I don't really understand your question here.  Are you asking about C or LLVM IR, or something else?
> 
> Sorry for the confusion. Does ConstantFoldBinaryInstruction also fold
> x ^ y into 0 if both x and y are undef?

That's a poorly formed question.  ConstantFoldBinaryInstruction doesn't do any real analysis - if there is a symbolic operand, it doesn't do the fold.  It only folds when the two operands *are* undef.  It has no idea if they came from the "same" variable or not.

-Chris