[llvm-dev] Optimize from 'for' to 'do-while' when setting #pragma clang loop min(1) (original) (raw)

Finkel, Hal J. via llvm-dev llvm-dev at lists.llvm.org
Mon Oct 15 19:50:57 PDT 2018

Hi, Klarke,

Does adding __builtin_assume(n > 0); before the loop currently accomplish what you're trying to do?

-Hal

On 10/15/2018 09:37 PM, Qianyi (Compiler) via llvm-dev wrote: To whom it may concern,

I’m implementing one pragma to optimize “for” loop. We assume the loop will run at least 1 times when we set following pragma: #pragma clang loop min(1) for(i = 0; i < n; I ++) Then we can remove the first branch which go to exit block when “n < =0”.

This is one picture which show llvm how to do loop rotation. [cid:part1.E82CD81F.F5E8AB60 at anl.gov]

Is it the proper place(LoopRotation.cpp) to implement my feature? Or is there more suitable place to do it?

Best regards, Klarke

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-- Hal Finkel Lead, Compiler Technology and Programming Languages Leadership Computing Facility Argonne National Laboratory -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20181016/eff0ff04/attachment.html> -------------- next part -------------- A non-text attachment was scrubbed... Name: image001.jpg Type: image/jpeg Size: 19260 bytes Desc: image001.jpg URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20181016/eff0ff04/attachment.jpg>

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