[llvm] [X86][test] Add -combiner-topological-sorting to X86 CodeGen tests (NFC) (PR #189947)

[Simon Pilgrim via llvm-commits]

RKSimon wrote:

> I started looking at regressions related to carry propagation. I will try to send a DAG combiner change which handles one regression there. I just found the `// TODO: Just match ISD::ABDU once the DAG is topological sorted.` comment so I think I can apply the same approach if you think this is good.

OK - I'm expecting we will have to have a few of those TODOs in place for some time - allowing us to match with either sorting order - I am finding plenty of cases with the current ordering that benefits from the "topological" matching as well, so its not like much would be redundant code prior to the (eventual flip over)

If you do think another target would be easier to work on, please give it a go - x86 has the most regression test coverage to help us check the most combines but other targets might benefit more quickly.


https://github.com/llvm/llvm-project/pull/189947