[llvm] [SelectionDAG] Expand CLMUL of zero-extended all-ones operand via parallel prefix XOR (PR #207339)

[Jan Schultke via llvm-commits]

eisenwave wrote:

@RKSimon I've bumped both commits to make sure this is still up-to-date.

Can you give it a look?

https://github.com/llvm/llvm-project/pull/207339