[PATCH] D46031: [DAGCombiner] Masked merge: if 'B' is constant, de-canonicalize the pattern (invert the mask).

[Sanjay Patel via Phabricator via llvm-commits]

spatel added a comment.

>>   Or is the problem that we should be ignoring 'not' ops as candidates for transforming in this function? Or both?
> 
> I don't think i'm able to answer that. Instcombine should certainly handle that, yes.

I may still not be seeing clearly, but I think this is the real problem - we should just bail out if the 'xor' is truly a 'not'. 
Nothing good is going to come out of us trying to improve on that here.

The 'andn' with constant for x86 is a small concern. It might be a win or not, but it's probably not going to make a big difference either way?


Repository:
  rL LLVM

https://reviews.llvm.org/D46031