[all-commits] [llvm/llvm-project] de18fa: Revert "[InstSimplify] Bypass no-op `and`-mask, us...

[Nikita Popov via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: de18fa9e52a439798edf89df6fee807908814416
      https://github.com/llvm/llvm-project/commit/de18fa9e52a439798edf89df6fee807908814416
  Author: Nikita Popov <nikita.ppv at gmail.com>
  Date:   2021-04-21 (Wed, 21 Apr 2021)

  Changed paths:
    M llvm/lib/Analysis/InstructionSimplify.cpp
    M llvm/test/Transforms/InstSimplify/AndOrXor.ll

  Log Message:
  -----------
  Revert "[InstSimplify] Bypass no-op `and`-mask, using known bits (PR49543)"

This reverts commit ea1a0d7c9ae3e5232a4163fc67efad4aabd51f2b.

While this is strictly more powerful, it is also strictly slower.
InstSimplify intentionally does not perform many folds that it
is allowed to perform, if doing so requires a KnownBits calculation
that will be repeated in InstCombine.

Maybe it's worthwhile to do this here, but that needs a more
explicitly stated motivation, evaluated in a review.