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[InstCombine] Commuted pattern is not handled #121696

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dtcxzyw opened this issue Jan 5, 2025 · 5 comments
Open

[InstCombine] Commuted pattern is not handled #121696

dtcxzyw opened this issue Jan 5, 2025 · 5 comments
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llvm:instcombine metabug Issue to collect references to a group of similar or related issues. missed-optimization

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dtcxzyw commented Jan 5, 2025 •
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This issue lists all the missed optimization issues related to commutative patterns in InstCombine.
@dtcxzyw dtcxzyw self-assigned this Jan 5, 2025
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@dtcxzyw dtcxzyw added the metabug Issue to collect references to a group of similar or related issues. label Jan 5, 2025
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dtcxzyw commented Jan 5, 2025

@nikic @goldsteinn
What is the policy for these issues? There is no reason not to support the commuted versions of these patterns.
However, as these issues have existed for a long time and there are no reports from downstream users, can we just delete the code entirely if there is no evidence of real-world usefulness?

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nikic commented Jan 5, 2025

I don't think it's possible to answer this in general. Adding support for the commuted pattern is always safe. To drop the transform we should do some investigation (like try to find out why it was added in the first place) on a case by case basis.

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