[PATCH] D113291: [AggressiveInstCombine] Lower Table Based CTTZ and enable it for AARCH64 in -O3

[Sanjay Patel via Phabricator via llvm-commits]

spatel added a comment.

AggressiveInstCombine is an extension of InstCombine. That is, it's a target-independent canonicalization pass. Therefore, we shouldn't use any target-specific cost model to enable the transform. Since we have a generic intrinsic for cttz, it's fine to create that for all targets as long as we can guarantee that a generic expansion of that intrinsic in the backend will not be worse than the original code.

But I'm not sure if we can make that guarantee? If not, this should be implemented as a late IR or codegen pass (as it was when first posted).


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D113291/new/

https://reviews.llvm.org/D113291