[ScalarizeMaskedMemIntrin][ProfCheck] Correctly annotate branch weights (part 2) (#219286)
https://github.com/llvm/llvm-project/pull/218753 broke LLVM CI because
it added a new test in `ScalarizeMaskedMemIntrin` that was not opted out
of during profcheck. Profcheck failed because this pass creates new
branches that did not attach branch weight metadata. We don't have any
information on the distribution of masks at runtime, so we have to mark
branch weights as explicitly unknown.
This basically extends https://github.com/llvm/llvm-project/pull/181568,
Aiden am I missing something for why you didn't add the branch weight
metadata for all branch creation before?
Tested the `ScalarizeMaskedMemIntrin` tests with profcheck locally and
they all pass.