[LLVMdev] ConstantFold 'undef xor undef'

Chris Lattner clattner at apple.com
Wed Jul 7 08:49:58 PDT 2010

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.


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