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Missing loop vectorization due to optimization in InstrCombine #139050

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thevar1able opened this issue May 8, 2025 · 0 comments
Open

Missing loop vectorization due to optimization in InstrCombine #139050

thevar1able opened this issue May 8, 2025 · 0 comments
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regression vectorizers

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@thevar1able
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thevar1able commented May 8, 2025 •
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Loop vectorization that worked with clang-19 stopped with clang-20.

Minimal repro:
https://godbolt.org/z/Yd4KjG9Yo
https://godbolt.org/z/cP5jeeo5Y

I bisected the regression to this PR. Looks like wrapping inside select(...) confuses LoopVectorizer.

Backreference: ClickHouse/ClickHouse#77352 (comment)
@thevar1able thevar1able changed the title Missing masked loop vectorization due to optimization in InstrCombine Missing loop vectorization due to optimization in InstrCombine May 8, 2025
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@fhahn @thevar1able @llvmbot