[llvm] [InstCombine] Detect uadd with overflow idiom (PR #140178)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> Anyway, I would say it is better for now to catch these patterns here, rather than codegenprepare. @topperc what do you think?

It might be easier to add these cases, but it increase the number of places that now need to worry about the add overflow intrinsics. It would probably be better to rewrite this case into the add-with-overflow pattern that CodeGenPrepare does recognize, rather than writing directly to the intrinsics 


https://github.com/llvm/llvm-project/pull/140178