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

Sun Jun 6 07:09:48 PDT 2021

hyeongyukim added a comment.

In D99481#2790423 <https://reviews.llvm.org/D99481#2790423>, @lebedev.ri wrote:

> 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.

I fixed this problem. Could anyone can review it again?

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https://reviews.llvm.org/D99481