[llvm] [DAG] visitCLMUL - fold (clmul x, c_pow2) -> (shl x, log2(c_pow2)) (PR #184049)

[Simon Pilgrim via llvm-commits]

RKSimon wrote:

> does this also work for `(clmul x, 1) -> x` etc? If not, it probably should.

Its mentioned in the summary that it does and there is a test for it as well in clmul_i32_one

https://github.com/llvm/llvm-project/pull/184049