Fold pointer operations in GVN #120405
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Fold pointer operations in GVN #120405
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Some changes occurred to the CTFE / Miri engine cc @rust-lang/miri Some changes occurred to MIR optimizations cc @rust-lang/wg-mir-opt |
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@bors try @rust-timer queue |
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Fold pointer operations in GVN This PR proposes 2 combinations of cast operations in MIR GVN: - a chain of `PtrToPtr` or `MutToConstPointer` casts can be folded together into a single `PtrToPtr` cast; - we attempt to evaluate more ptr ops when there is no provenance. In particular, this allows to read from static slices. This is not yet sufficient to see through slice operations that use `PtrComponents` (because that's a union), but still a step forward. r? `@ghost`
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☀️ Try build successful - checks-actions |
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Finished benchmarking commit (bf3fe6c): comparison URL. Overall result: ❌✅ regressions and improvements - ACTION NEEDEDBenchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf. Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @bors rollup=never Instruction countThis is a highly reliable metric that was used to determine the overall result at the top of this comment.
Max RSS (memory usage)ResultsThis is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.
CyclesResultsThis is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.
Binary sizeResultsThis is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.
Bootstrap: 659.743s -> 662.688s (0.45%) |
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-18% instructions and -27.5% cycles on the Looks like it was able to see through more stuff and optimize better: |
RalfJung
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Jan 27, 2024
RalfJung
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Jan 27, 2024
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r? @oli-obk |
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@bors r+ rollup=never |
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Fold pointer operations in GVN This PR proposes 2 combinations of cast operations in MIR GVN: - a chain of `PtrToPtr` or `MutToConstPointer` casts can be folded together into a single `PtrToPtr` cast; - we attempt to evaluate more ptr ops when there is no provenance. In particular, this allows to read from static slices. This is not yet sufficient to see through slice operations that use `PtrComponents` (because that's a union), but still a step forward. r? `@ghost`
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💔 Test failed - checks-actions |
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Fold pointer operations in GVN This PR proposes 2 combinations of cast operations in MIR GVN: - a chain of `PtrToPtr` or `MutToConstPointer` casts can be folded together into a single `PtrToPtr` cast; - we attempt to evaluate more ptr ops when there is no provenance. In particular, this allows to read from static slices. This is not yet sufficient to see through slice operations that use `PtrComponents` (because that's a union), but still a step forward. r? `@ghost`
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The job Click to see the possible cause of the failure (guessed by this bot) |
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💔 Test failed - checks-actions |
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@bors retry invalid r_symbolnum |
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Fold pointer operations in GVN This PR proposes 2 combinations of cast operations in MIR GVN: - a chain of `PtrToPtr` or `MutToConstPointer` casts can be folded together into a single `PtrToPtr` cast; - we attempt to evaluate more ptr ops when there is no provenance. In particular, this allows to read from static slices. This is not yet sufficient to see through slice operations that use `PtrComponents` (because that's a union), but still a step forward. r? `@ghost`
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The job Click to see the possible cause of the failure (guessed by this bot) |
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💔 Test failed - checks-actions |
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@bors retry invalid r_symbolnum |
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☀️ Test successful - checks-actions |
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Finished benchmarking commit (9aa232e): comparison URL. Overall result: ❌✅ regressions and improvements - ACTION NEEDEDNext Steps: If you can justify the regressions found in this perf run, please indicate this with @rustbot label: +perf-regression Instruction countThis is a highly reliable metric that was used to determine the overall result at the top of this comment.
Max RSS (memory usage)ResultsThis is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.
CyclesResultsThis is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.
Binary sizeResultsThis is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.
Bootstrap: 668.04s -> 665.965s (-0.31%) |
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The binary size results aren't good here, though the worst of the regressions are on secondary benchmarks. Was that expected? Can anything be done to improve it? |
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The metadata got larger, binary size not at all, or just very slightly. I think that's fine. @rustbot label: +perf-regression-triaged |
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This PR proposes 2 combinations of cast operations in MIR GVN:
PtrToPtrorMutToConstPointercasts can be folded together into a singlePtrToPtrcast;In particular, this allows to read from static slices.
This is not yet sufficient to see through slice operations that use
PtrComponents(because that's a union), but still a step forward.r? @ghost