[PATCH] D63065: [InstSimplify] Fix addo/subo undef folds (PR42209)

[Nikita Popov via Phabricator via llvm-commits]

nikic created this revision.
nikic added reviewers: nlopes, lebedev.ri, spatel.
Herald added subscribers: llvm-commits, hiraditya.
Herald added a project: LLVM.

Fix folds of addo and subo with an undef operand to be:

- `subo(X, undef)` folds to `{ 0, false }` (holds for `undef = X`).
- `addo(X, undef)` folds to `{ -1, false }` (holds for `undef = ~X`).
- Same for commuted variants.

These are consistent with the folds we use for subsat and addsat.


Repository:
  rL LLVM

https://reviews.llvm.org/D63065

Files:
  llvm/lib/Analysis/InstructionSimplify.cpp
  llvm/test/Transforms/InstCombine/with_overflow.ll
  llvm/test/Transforms/InstSimplify/call.ll

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