[llvm] [AArch64][GlobalISel] Select UMULL instruction (PR #65469)

[Amara Emerson via llvm-commits]

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

Sorry, for some reason this doesn't appear on my "Review Requested" page.

That's unfortunate about the artifacts, I hadn't considered that issue when using LegalizerHelper at the lowering phase. In fact in the general case not running the artifact combiner can be a fatal error since we rely on the combines to eliminate un-selectable operations. In this case it doesn't result in that issue however.

To fix that we can schedule artifact combining after lowering, either as a new pass or just append it to the end of lowering's `runOnMachineFunction()`. It's not ideal but we may need to do that eventually anyway for other reasons.

Don't need to fix that right now though, it can be follow up later.


https://github.com/llvm/llvm-project/pull/65469