[llvm] [SelectionDAG] Scalarize binary ops of splats before legal types (PR #100749)

[Luke Lau via llvm-commits]

https://github.com/lukel97 approved this pull request.

LGTM, I remember being stumped on this when I filed the issue but this patch handles it very elegantly :)

Also I hope you don't mind but I updated the PR title to add a tag, https://llvm.org/docs/DeveloperPolicy.html#id18

Do you need someone to land this for you?

https://github.com/llvm/llvm-project/pull/100749