[PATCH] D109194: [InstCombine] Optimize (a & b) | (~a & c)

[Matthias Braun via Phabricator via llvm-commits]

MatzeB added a comment.

> It looks like have a reverse fold to this in DAG: DAGCombiner::unfoldMaskedMerge

Notice that too. It depends on `TargetLower::hasAndNot()` to return `true`. I tried implementing `hasAndNot()` in the ARM and SystemZ backend trying to eliminate the differences here, unfortunately that has ripple effects in other areas and I am not sure how deep I want to dig (patterns like `select(x < 0, 0, x)` are DAGCombined into `(x & ~(x >>s 31))` making the targets fail to select specialized saturation instructions...). Though I could probably refactor things to make it possible to independently unfold masked merge separately from the and-not zero saturation.


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https://reviews.llvm.org/D109194