[PATCH] D117912: [IR] document and update ctlz/cttz intrinsics to optionally return poison rather than undef

[Eli Friedman via Phabricator via llvm-commits]

efriedma added a comment.

Seems fine.  This is technically not bitcode backwards-compatible, but that seems unlikely to matter.

> Hopefully, we are approaching a point where we can stop caring about the legacy behavior

You mean, we might reach a point where we could make clang emit is_zero_poison=false without anyone caring?  Don't think we're quite there yet.  x86-64-v2 doesn't include lzcnt.  And not sure about the current state of the compiler-rt/libgcc intrinsics.


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https://reviews.llvm.org/D117912