[llvm] [ISel] Introduce llvm.clmul[rh] intrinsics (PR #168731)

[Craig Topper via llvm-commits]

topperc wrote:

> Should the intrinsics be first introduced into llvm.experimental namespace?

There was a proposal to get rid of that namespace, but I'm not sure it reached a conclusion https://discourse.llvm.org/t/rfc-dont-use-llvm-experimental-intrinsics/85352

https://github.com/llvm/llvm-project/pull/168731