[llvm] [CostModel][X86] Improve vXi1 mask broadcast cost handling (PR #222467)

[Simon Pilgrim via llvm-commits]

https://github.com/RKSimon requested changes to this pull request.

Please merge against trunk once #225070 lands - in future I'd recommend you add new tests in the first commit of a PR, so later commits in the chain can then show the diff to the test from your code changes. PR stacks for tests isn't usually necessary.

https://github.com/llvm/llvm-project/pull/222467