[llvm] [RISCV][GISel] Lower G_SSUBE (PR #157855)

[Craig Topper via llvm-commits]

topperc wrote:

> By the way, @topperc , RISCV enables lowering for `G_USUBE` via `getActionDefinitionsBuilder({G_UADDE, G_UADDO, G_USUBE, G_USUBO}).lower()` , but there’s no corresponding legalizer test. I think:(1) a small PR adding `G_USUBE` tests;(2) a follow-up PR that merges `G_UADDE, G_USUBE, G_SADDE, G_SSUBE` tests into a single file. First PR adds coverage; second is a mechanical cleanup. Is it a good idea?

I don't think we need legalizer tests for every instruction. If we have IR tests that cover it that's probably enough. We probably have too many legalizer tests.

https://github.com/llvm/llvm-project/pull/157855