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

Nikita Popov via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Tue May 30 03:40:39 PDT 2023


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.


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https://reviews.llvm.org/D151691



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