[PATCH] D48768: [X86] When have BMI2, prefer shifts to clear low/high bits, rather than variable mask.

[Craig Topper via Phabricator via llvm-commits]

craig.topper added a comment.

This specifically looks for (and (shl -1, X), Y) or (and (shr -1, X), Y).  If Y in either of those is a constant, I think we would have rewritten the LHS side of the shift already and removed the 'and' entirely.


Repository:
  rL LLVM

https://reviews.llvm.org/D48768