[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 added a comment.

In https://reviews.llvm.org/D48768#1148450, @craig.topper wrote:

> If you do the one use check in the DAG combine to qualify the reverse, then we can use existing isel patterns to select each shift individually right?


I'm not sure i understand the question.
I would expect that the DAG combine reverse would fully replace these
`X86InstrCompiler.td` changes, while keeping the same test output.


Repository:
  rL LLVM

https://reviews.llvm.org/D48768