[llvm] [ISel] Commute FMUL and inserting zero into vector lane (PR #146096)

[Julian Nagele via llvm-commits]

juliannagele wrote:

> I was just checking through - does this need nnan and ninf? And maybe nsz?

Ah yes, all three I think, thanks! Added checks and a test.

https://github.com/llvm/llvm-project/pull/146096