[PATCH] D99481: [InstCombine] Fix miscompile on GEP+load to icmp fold (PR45210)

Mon May 31 18:37:33 PDT 2021

mdchen added subscribers: kuhar, mdchen.
mdchen added a comment.

In D99481#2790122 <https://reviews.llvm.org/D99481#2790122>, @aqjune wrote:

> Reduced .ll: F17146264: reduce.ll <https://reviews.llvm.org/F17146264>
>
>   $ opt -instcombine -S -o - reduce.ll
>   LLVM ERROR: Instruction Combining seems stuck in an infinite loop after 100 iterations.
>   ...

@kuhar @spatel @lebedev.ri 
I tested the case locally and saw the iteration number is exactly 1001. I've met a similar problem before, which also required 1001 iterations(but I can only reproduce it in our local codebase), which I don't know a coincidence or something resulted from an internal algorithm issue. I think this is a good chance to discuss if the threshold and fatal behavior introduced in https://reviews.llvm.org/D71673.

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https://reviews.llvm.org/D99481