JIT: Pick some low-hanging fruit in physical promotion throughput #86792
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* Skip any IR traversals entirely if there are no candidates locals for physical promotion * During accounting, do a quick pre-check for candidates in each statement using the linked locals list, before doing the tree walk. Result: Diff JIT options: JitEnablePhysicalPromotion=1 FullOpts (+0.25% to +0.82%) |Collection|PDIFF| |---|--:| |aspnet.run.windows.x64.checked.mch |+0.82%| |benchmarks.run.windows.x64.checked.mch |+0.35%| |benchmarks.run_pgo.windows.x64.checked.mch |+0.58%| |benchmarks.run_tiered.windows.x64.checked.mch |+0.59%| |coreclr_tests.run.windows.x64.checked.mch |+0.25%| |libraries.crossgen2.windows.x64.checked.mch |+0.40%| |libraries.pmi.windows.x64.checked.mch |+0.54%| |libraries_tests.pmi.windows.x64.checked.mch |+0.32%|
Process scalar uses via the linked list and struct uses with the tree walk. The tree walk can skip any entire subtree without GTF_CALL/GTF_ASG. Diff JIT options: JitEnablePhysicalPromotion=1 FullOpts (+0.25% to +0.85%) |Collection |PDIFF | |--- | --:| |aspnet.run.windows.x64.checked.mch |+0.85%| |benchmarks.run.windows.x64.checked.mch |+0.36%| |benchmarks.run_pgo.windows.x64.checked.mch |+0.61%| |benchmarks.run_tiered.windows.x64.checked.mch |+0.62%| |coreclr_tests.run.windows.x64.checked.mch |+0.25%| |libraries.crossgen2.windows.x64.checked.mch |+0.40%| |libraries.pmi.windows.x64.checked.mch |+0.55%| |libraries_tests.pmi.windows.x64.checked.mch |+0.33%|
This reverts commit a5ed498. This is worse than the existing approach.
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Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch Issue Details
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cc @dotnet/jit-contrib PTAL @EgorBo
Throughput cost of enabling this by default looks reasonable, but I definitely need to study more cases, especially on linux-x64 and win-x86. Hopefully benchmarks will help to prioritize where to look. |
EgorBo
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May 26, 2023
Agree 👍 |
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physical promotion
statement using the linked locals list, before doing the tree walk.