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

[Philip Reames via Phabricator via llvm-commits]

reames added a comment.

I may be missing something but isn't this a pessimization for the case where the mask is an immediate that can be directly encoded into the and instruction?  Why should we prefer dual shifts over something like an AND RAX, 0xfff?


Repository:
  rL LLVM

https://reviews.llvm.org/D48768