[PATCH] D138814: [InstCombine] Combine a/lshr of add -> uadd.with.overflow

[Pierre van Houtryve via Phabricator via llvm-commits]

Pierre-vh added a comment.

In D138814#3973599 <https://reviews.llvm.org/D138814#3973599>, @nikic wrote:

> FWIW our historical stance has always been that uadd.with.overflow is non-canonical, and the canonical pattern is `a + b < a` (for non-constant `b`). uadd.with.overflow generally has worse optimization support, which is why we only form it during CGP for backend purposes.

Interesting, not sure what other reviewers think?
Maybe adding a TII hook so targets can enable/disable the combine is a good idea? e.g. something like `allowUAddoCanonicalForm`?


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