[PATCH] D59066: [TargetLowering] improve the default expansion of uaddsat/usubsat

[Nikita Popov via Phabricator via llvm-commits]

nikic added a comment.

@spatel D59174 <https://reviews.llvm.org/D59174> is not AArch64 specific and covers what this patch does, but only for the case where VSELECT is expanded. An alternative would be to add a combine for `vselect zero_or_neg_one, neg_one, x -> zero_or_neg_one | x` and `vselect zero_or_neg_one, 0, x -> ~zero_or_neg_one & x`, though it's arguable whether the latter is an improvement in general.

Also okay with what this patch does, but the other test changes from D59174 <https://reviews.llvm.org/D59174> show that the pattern can also occur in other cases, so we might want to handle it more generally.


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  https://reviews.llvm.org/D59066/new/

https://reviews.llvm.org/D59066