[PATCH] D140087: [X86] Replace (31/63 -/^ X) with (NOT X) and ignore (32/64 ^ X) when computing shift count

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

Also note that microcoded instructions (with more than 2 uops),
at least on older AMD CPU's, used to significantly affect decoder throughput,
which was shared by threads of a core. I'm also not quite sure `bts` would be a win.


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https://reviews.llvm.org/D140087