perf: UninhabitedEnumBranching avoid n^2 #77597
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r? @estebank (rust_highfive has picked a reviewer for you, use r? to override) |
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@bors try @rust-timer queue |
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Awaiting bors try build completion |
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⌛ Trying commit de89fb67fb8292b1f27f59ea7d585a3e95c9d520 with merge c7115a3597a7b1fbced7d79b8a23e22359edc73d... |
| @@ -89,7 +91,7 @@ impl<'tcx> MirPass<'tcx> for UninhabitedEnumBranching { | |||
| let layout = tcx.layout_of(tcx.param_env(body.source.def_id()).and(discriminant_ty)); | |||
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| let allowed_variants = if let Ok(layout) = layout { | |||
| variant_discriminants(&layout, discriminant_ty, tcx) | |||
| FxHashSet::from_iter(variant_discriminants(&layout, discriminant_ty, tcx)) | |||
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| FxHashSet::from_iter(variant_discriminants(&layout, discriminant_ty, tcx)) | |
| variant_discriminants(&layout, discriminant_ty, tcx).collect() |
..then you can remove the FromIterator import
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variant_discriminants could be changed to return a FxHashSet directly which would avoid some overhead.
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Addressed in latest commit
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☀️ Try build successful - checks-actions, checks-azure |
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Queued c7115a3597a7b1fbced7d79b8a23e22359edc73d with parent a1dfd24, future comparison URL. |
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Finished benchmarking try commit (c7115a3597a7b1fbced7d79b8a23e22359edc73d): comparison url. Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. Please note that if the perf results are neutral, you should likely undo the rollup=never given below by specifying Importantly, though, if the results of this run are non-neutral do not roll this PR up -- it will mask other regressions or improvements in the roll up. @bors rollup=never |
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I interpret the perf results as being good. This PR should not change behavior, so in a perfect deterministic world I would only expect optimized_mir to be affected by this change. I therefore see all regressions reported in LLVM as noise. For match-stress-enum this is a clear win. All other benchmarks look neutral. |
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r=me with #77597 (comment) addressed |
jonas-schievink
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Avoid n² complexity. This showed up in a profile for match-stress-enum that has 8192 variants
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@bors r+ |
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📌 Commit e231c47 has been approved by |
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☀️ Test successful - checks-actions, checks-azure |
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As expected, a minor improvement on the match stress test (https://perf.rust-lang.org/compare.html?start=91a79fb29ac78d057d04dbe86be13d5dcc64309a&end=e055f87cdfcac1f4da6c518a547dee459de0aa26&stat=instructions:u). Slight (0.1%) wins on other benchmarks. Great work! |
Avoid n² complexity. This showed up in a profile for match-stress-enum that has 8192 variants
I have only profiled locally against
match-stress-enum, so we should have it perf tested to make sure it does not regress other crates.