Florian Hahn
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a5d3522c13
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[SCEV] Rewrite A - B = UMin(1, A - B) lazily for A != B loop guards. (#163787)
Follow-up to 2d027260b0f8
(https://github.com/llvm/llvm-project/pull/160500)
Creating the SCEV subtraction eagerly is very expensive. To soften the
blow, just collect a map with inequalities and check if we can apply the
subtract rewrite when rewriting SCEVAddExpr.
Restores most of the regression:
http://llvm-compile-time-tracker.com/compare.php?from=0792478e4e133be96650444f3264e89d002fc058&to=7fca35db60fe6f423ea6051b45226046c067c252&stat=instructions:u
stage1-O3: -0.10%
stage1-ReleaseThinLTO: -0.09%
stage1-ReleaseLTO-g: -0.10%
stage1-O0-g: +0.02%
stage1-aarch64-O3: -0.09%
stage1-aarch64-O0-g: +0.00%
stage2-O3: -0.17%
stage2-O0-g: -0.05%
stage2-clang: -0.07%
There is still some negative impact compared to before 2d027260b0f8, but
there's probably not much we could do reduce this even more.
Compile-time improvement with 2d027260b0f8 reverted on top of the
current PR:
http://llvm-compile-time-tracker.com/compare.php?from=7fca35db60fe6f423ea6051b45226046c067c252&to=98dd152bdfc76b30d00190d3850d89406ca3c21f&stat=instructions:u
stage1-O3: 60628M (-0.03%)
stage1-ReleaseThinLTO: 76388M (-0.04%)
stage1-ReleaseLTO-g: 89228M (-0.02%)
stage1-O0-g: 18523M (-0.03%)
stage1-aarch64-O3: 67623M (-0.03%)
stage1-aarch64-O0-g: 22595M (+0.01%)
stage2-O3: 52336M (+0.01%)
stage2-O0-g: 16174M (+0.00%)
stage2-clang: 34890032M (-0.03%)
PR: https://github.com/llvm/llvm-project/pull/163787
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2025-10-18 13:32:40 +01:00 |
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Florian Hahn
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0590c9e828
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[IndVars] Add additional tests with ICMP_NE loop guards.
Extra test coverage for
https://github.com/llvm/llvm-project/pull/163787.
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2025-10-17 12:56:25 +01:00 |
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Florian Hahn
|
2d027260b0
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[SCEV] Collect guard info for ICMP NE w/o constants. (#160500)
When collecting information from loop guards, use UMax(1, %b - %a) for
ICMP NE %a, %b, if neither are constant.
This improves results in some cases, and will be even more useful
together with
* https://github.com/llvm/llvm-project/pull/160012
* https://github.com/llvm/llvm-project/pull/159942
https://alive2.llvm.org/ce/z/YyBvoT
PR: https://github.com/llvm/llvm-project/pull/160500
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2025-10-14 14:20:34 +00:00 |
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Florian Hahn
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f8a7f36a61
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[IndVars,LV] Add tests with pointer-based loop guards.
Add tests with pointer-based loop guards.
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2025-09-22 14:14:52 +01:00 |
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