[llvm] 554b1bc - [InstCombine] ~(C + X) --> ~C - X (PR50308)

[Florian Hahn via llvm-commits]

Hi,


> On May 12, 2021, at 14:11, Roman Lebedev via llvm-commits <llvm-commits at lists.llvm.org> wrote:
> 
> 
> Author: Roman Lebedev
> Date: 2021-05-12T16:10:55+03:00
> New Revision: 554b1bced325a8d860ad00bd59020d66d01c95f8
> 
> URL: https://github.com/llvm/llvm-project/commit/554b1bced325a8d860ad00bd59020d66d01c95f8
> DIFF: https://github.com/llvm/llvm-project/commit/554b1bced325a8d860ad00bd59020d66d01c95f8.diff
> 
> LOG: [InstCombine] ~(C + X) --> ~C - X (PR50308)
> 
> We can not rely on (C+X)-->(X+C) already happening,
> because we might not have visited that `add` yet.
> The added testcase would get stuck in an endless combine loop.
> 

Unfortunately this exposed another infinite loop. Please see https://bugs.llvm.org/show_bug.cgi?id=50370 <https://bugs.llvm.org/show_bug.cgi?id=50370> for a reproducer.


Cheers,
Florian
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