[PATCH] D101142: [SimplifyCFG/JumpThreading] Do not simplify empty blocks with unconditional branches if this causes loop metadata confusion.

Fri Apr 23 01:52:56 PDT 2021

jeroen.dobbelaere added a comment.

In D101142#2711453 <https://reviews.llvm.org/D101142#2711453>, @lebedev.ri wrote:

> In D101142#2711394 <https://reviews.llvm.org/D101142#2711394>, @Meinersbur wrote:
>
>> In D101142#2711283 <https://reviews.llvm.org/D101142#2711283>, @jeroen.dobbelaere wrote:
>>
>>> Did you verify the effect of this on the performance ? In a similar (but different) trial where I tried to block merging of blocks when that would result in a conflict with loop annotations, I noticed unacceptable regressions.
>>
>> I did not. This is a correctness fix. Arguing for performance over correctness feels weird.

It indeed feels weird and maybe your testing shows that it is not that big of a problem. My feeling was that maybe a different approach in describing loop information might be more appropriate, resulting in accurate information, without the observed performance impact. That given, I have no idea yet how that could look like :(.

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  https://reviews.llvm.org/D101142/new/

https://reviews.llvm.org/D101142