[llvm] [SelectionDAG] Use ExpandIntRes_CLMUL to expand vector CLMUL via narrower legal types (PR #184468)

[via llvm-commits]

AbdallahRashed wrote:

> I don't think "Karatsuba" is a good name for this, unless there is some precedent for it? For regular multiplication the Karatsuba algorithm specifically involves doing only _three_ half-width multiplications in the divide and conquer step.

@jayfoad  I was taking ExpandIntRes_CLMUL as reference, I was under the impression it is karatsuba, but you are right it is normal divide and conquer. I have renamed it. 

https://github.com/llvm/llvm-project/pull/184468