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

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

In D99481#2790131 <https://reviews.llvm.org/D99481#2790131>, @mdchen wrote:

> 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.

It fails even if i bump those limits to 0.1M iterations.
This is clearly an infinite combine cycle.


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