[llvm] [RFC][X86] Allow speculative BSR/BSF instructions on targets with CMOV (PR #102885)

[Simon Pilgrim via llvm-commits]

RKSimon wrote:

Hmm, we already have TuningLZCNTFalseDeps - would it be worth a separate PR adding TuningBitScanFalseDeps and zeroing out the destination register?

https://github.com/llvm/llvm-project/pull/102885