[llvm] [LoopIdiomRecognize] Enable clmul optimization for CRC loops (PR #203405)

[Sean Clarke via llvm-commits]

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xarkenz wrote:

I think `getLargestLegalIntType` does actually help in this case since on the four targets I've tested on (riscv32/64+zbc, aarch64+aes, x86_64+pclmul), clmul is `Legal` for the largest legal type. I think for now instead of using `getSmallestLegalIntType`, I'll promote to the largest legal type provided that `Ty->getBitWidth()` does not exceed the largest legal bitwidth.

https://github.com/llvm/llvm-project/pull/203405