Reland "[Transforms] LoopIdiomRecognize recognize strlen and wcslen (#108985)" #131412
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Co-authored-by: Michael Kruse <github@meinersbur.de>
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✅ With the latest revision this PR passed the C/C++ code formatter. |
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Meinersbur
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Mar 17, 2025
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/18/builds/13294 Here is the relevant piece of the build log for the reference |
nikic
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| const ConstantInt *CmpZero = dyn_cast<ConstantInt>(Val); | ||
| if (!CmpZero || !CmpZero->isZero()) | ||
| return false; | ||
| return true; |
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This looks like match(Val, m_Zero()). Though I'm not super clear on why this patch has to add the pointer handling at all.
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Thank you for taking. You are right, it's no longer needed. We used to use this to condition the loop preheader on a nullptr comparison for the base of the string. I will clean this up
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| dbgs() << "loop exit phi scev: "; | ||
| Ev->print(dbgs()); | ||
| dbgs() << "\n"; |
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Can use << *Ev, no need for print().
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| ; RUN: opt -passes='loop(loop-idiom),verify' < %s -S | FileCheck %s | |||
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verify is redundant, it is scheduled automatically.
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Another small bug got passed testing without expensive checks and corresponding cleanups: #132421 |
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…lvm#108985)" (llvm#131412) Relands llvm#108985 This PR continues the effort made in https://discourse.llvm.org/t/rfc-strlen-loop-idiom-recognition-folding/55848 and https://reviews.llvm.org/D83392 and https://reviews.llvm.org/D88460 to extend `LoopIdiomRecognize` to find and replace loops of the form ```c base = str; while (*str) ++str; ``` and transforming the `strlen` loop idiom into the appropriate `strlen` and `wcslen` library call which will give a small performance boost if replaced. ```c str = base + strlen(base) len = str - base ```
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Relands #108985
Fixed the logic error in #108985 that does not bailout if the library function is not emitable.
Fixed this issue and added a test for checking emitable.