[PATCH] D151691: Revert "[InstCombine] Handle undef when pruning unreachable code"

[Nikita Popov via Phabricator via llvm-commits]

nikic requested changes to this revision.
nikic added a comment.
This revision now requires changes to proceed.

Branch on undef is undefined behavior, see https://llvm.org/docs/LangRef.html#id33:

> If ‘cond’ is poison or undef, this instruction has undefined behavior.

Either your source program has undefined behavior, or some optimization incorrectly introduced the branch on undef. If the latter, you may want to look through the print-after-all trace to identify when the br undef first appears. It's possible that some optimization is failing to `freeze` the condition.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D151691/new/

https://reviews.llvm.org/D151691