[PATCH] D121147: [x86] try harder to use shift instead of test if it can save some immediate bytes

[Matthias Braun via Phabricator via llvm-commits]

MatzeB added a comment.

I was thinking about the same thing, though looking around `https://www.uops.info/table.html` it seems that many CPUs can only schedule shifts on 1 or 2 of their ports while `and` typically can be scheduled on all of them. I'm not really sure whether that means we should only perform this transformation when going for code-size or whether it's unlikely anyway to hit port constraints so we should always do it...


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