[PATCH] D141464: [X86]: Match (xor TSize - 1, ctlz) to `bsr` instead of `lzcnt` + `xor`

[Noah Goldstein via Phabricator via llvm-commits]

goldstein.w.n added a comment.

In D141464#4042876 <https://reviews.llvm.org/D141464#4042876>, @RKSimon wrote:

> We have TuningFastLZCNT which should be a good enough predicate to control when NOT to perform this fold - you will need to add test coverage to clz.ll for fast/slow lzcnt

Done in V2 (I think, used `HasFastLZCNT`).


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