[PATCH] D34207: [IndVarSimplify] Add AShr exact flags using induction variables ranges.

[Dave Green via Phabricator via llvm-commits]

dmgreen added a comment.

Ping.  Anyone fancy taking a look at this, or suggesting a better place for it?

The definition of shifts past the bitwidth has recently been changed (or clarified?) to poison, not undef. I'm unsure how poison plays together with computeKnownBits, and whether the original cause of the regressions (back in https://reviews.llvm.org/rL297724) is now correct or not. It can still produce end to end compilation errors if it's reverted, which I guess is proof enough that it's needed! There may well be other ways to fix this though.


https://reviews.llvm.org/D34207