[PATCH] D93065: [InstCombine] Disable optimizations of select instructions that causes propagation of poison values

[Juneyoung Lee via Phabricator via llvm-commits]

aqjune added a comment.

>   for (i=0; some_bool && i < limit; ++i) {
>   ...
>   }

Assuming that all relevant optimizations are fully implemented in both scenarios (and/or with freeze vs. select), I think their performance diff should be zero because C/C++ constrains variables to have well-defined values.
Currently, this isn't enforced by clang. We already have !noundef, and simply attaching it to loads will do the trick.
Should we move toward the direction and suggest it to llvm-dev? The diff in clang src won't be big, but people might worry about their program being more undefined (which are written in that way due to a practical reason).


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https://reviews.llvm.org/D93065