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

[Florian Hahn via llvm-commits]

https://github.com/fhahn commented:

To add maybe a bit more context, commuting the ops may allow the insert to happen earlier, while if we do it after the mul we need to wait for the mul (and its other operand) to be completed.

It should not increase the critial path I think, so in the worst case should not make things worse

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