[llvm] [X86] Use BMM for bitreverse without GFNI (PR #209223)

[via llvm-commits]

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ganeshgit wrote:

Potential horizontal case. ISD::CTLZ which can be computed as CTTZ(BITREVERSE(x))!
We can do similar code change there from hasGFNI() to (hasGFNI() || hasBMM())

I am okay if you consider to do that separately. 

This patch LGTM!

https://github.com/llvm/llvm-project/pull/209223