[PATCH] D151878: [GlobalIsel][X86] Update legalization of G_ADD/G_SUB

[Matt Arsenault via Phabricator via llvm-commits]

arsenm added a comment.

> I'm not certain if the legalizer API has a better way we can do this?

I'm not super happy with the legalize rules API. I think it's over-constraining. In particular I don't see the point of having separate fewer/more actions. We could just have one ChangeType/ChangeElement action.

The clamping is also really annoying in the common case where you don't want intermediate non-power-of-2s as you've noticed. Some of the existing rule orderings are also working around missing paths in the legalizer, some of which are fixed. For example if you clamp a non-power-of-2 operation, the requested type ends up being the upper bound of the range and fails for implementations that only handle evenly divisible cases


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D151878/new/

https://reviews.llvm.org/D151878