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

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri planned changes to this revision.
lebedev.ri added a comment.

In https://reviews.llvm.org/D48768#1148439, @craig.topper wrote:

> Is it possible to reverse this as a DAG combine? I'd rather not produce 2 instructions from one pattern if we can avoid it.


Probably? I will take a look.
It will still need to produce two instructions (which is safe, since there is one-use check on the mask).


Repository:
  rL LLVM

https://reviews.llvm.org/D48768