[llvm] [SelectionDAG] Flags are dropped when creating a new FMUL (PR #66701)

[Jay Foad via llvm-commits]

https://github.com/jayfoad commented:

Code change looks good. Could you pre-commit the new test case (no review required) and then rebase this patch on it?

https://github.com/llvm/llvm-project/pull/66701