[PATCH] D150517: [WIP][ValueTracking] Make use of CtxI info in programUndefinedIfUndefOrPoison

Mon May 15 00:36:12 PDT 2023

StephenFan added a comment.

In D150517#4340663 <https://reviews.llvm.org/D150517#4340663>, @nikic wrote:

> I don't understand the example from the patch description. At the point sdiv is hoisted, the zext will be in the preheader and as such should not satisfy programUndefinedIfUndefOrPoison().
>
> Generally, the way this function is implemented requires the scan to start at the instruction. Simplify starting from a different place doesn't really make sense, because the YieldsPoison set will not be populated correctly.

You are right. I reimplemented a patch in D150542 <https://reviews.llvm.org/D150542>. I hope the description of that patch is clear. And I think we still can optimize `programUndefinedIfUndefOrPoison` to make use of CtxI.

Repository:
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  https://reviews.llvm.org/D150517/new/

https://reviews.llvm.org/D150517