RFR: 8346989: C2: deoptimization and re-compilation cycle with Math.*Exact in case of frequent overflow [v2]
Marc Chevalier
mchevalier at openjdk.org
Wed Mar 26 08:33:58 UTC 2025
> `Math.*Exact` intrinsics can cause many deopt when used repeatedly with problematic arguments.
> This fix proposes not to rely on intrinsics after `too_many_traps()` has been reached.
>
> Benchmark show that this issue affects every Math.*Exact functions. And this fix improve them all.
>
> tl;dr:
> - C1: no problem, no change
> - C2:
> - with intrinsics:
> - with overflow: clear improvement. Was way worse than C1, now is similar (~4s => ~600ms)
> - without overflow: no problem, no change
> - without intrinsics: no problem, no change
>
> Before the fix:
>
> Benchmark (SIZE) Mode Cnt Score Error Units
> MathExact.C1_1.loopAddIInBounds 1000000 avgt 3 1.272 ± 0.048 ms/op
> MathExact.C1_1.loopAddIOverflow 1000000 avgt 3 641.917 ± 58.238 ms/op
> MathExact.C1_1.loopAddLInBounds 1000000 avgt 3 1.402 ± 0.842 ms/op
> MathExact.C1_1.loopAddLOverflow 1000000 avgt 3 671.013 ± 229.425 ms/op
> MathExact.C1_1.loopDecrementIInBounds 1000000 avgt 3 3.722 ± 22.244 ms/op
> MathExact.C1_1.loopDecrementIOverflow 1000000 avgt 3 653.341 ± 279.003 ms/op
> MathExact.C1_1.loopDecrementLInBounds 1000000 avgt 3 2.525 ± 0.810 ms/op
> MathExact.C1_1.loopDecrementLOverflow 1000000 avgt 3 656.750 ± 141.792 ms/op
> MathExact.C1_1.loopIncrementIInBounds 1000000 avgt 3 4.621 ± 12.822 ms/op
> MathExact.C1_1.loopIncrementIOverflow 1000000 avgt 3 651.608 ± 274.396 ms/op
> MathExact.C1_1.loopIncrementLInBounds 1000000 avgt 3 2.576 ± 3.316 ms/op
> MathExact.C1_1.loopIncrementLOverflow 1000000 avgt 3 662.216 ± 71.879 ms/op
> MathExact.C1_1.loopMultiplyIInBounds 1000000 avgt 3 1.402 ± 0.587 ms/op
> MathExact.C1_1.loopMultiplyIOverflow 1000000 avgt 3 615.836 ± 252.137 ms/op
> MathExact.C1_1.loopMultiplyLInBounds 1000000 avgt 3 2.906 ± 5.718 ms/op
> MathExact.C1_1.loopMultiplyLOverflow 1000000 avgt 3 655.576 ± 147.432 ms/op
> MathExact.C1_1.loopNegateIInBounds 1000000 avgt 3 2.023 ± 0.027 ms/op
> MathExact.C1_1.loopNegateIOverflow 1000000 avgt 3 639.136 ± 30.841 ms/op
> MathExact.C1_1.loopNegateLInBounds 1000000 avgt 3 2.422 ± 3.59...
Marc Chevalier has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:
- Use builtin_throw
- Merge branch 'master' into fix/Deoptimization-and-re-compilation-cycle-with-C2-compiled-code
- More exhaustive bench
- Limit inlining of math Exact operations in case of too many deopts
-------------
Changes:
- all: https://git.openjdk.org/jdk/pull/23916/files
- new: https://git.openjdk.org/jdk/pull/23916/files/2317919f..9372228d
Webrevs:
- full: https://webrevs.openjdk.org/?repo=jdk&pr=23916&range=01
- incr: https://webrevs.openjdk.org/?repo=jdk&pr=23916&range=00-01
Stats: 66384 lines in 1241 files changed: 32808 ins; 21395 del; 12181 mod
Patch: https://git.openjdk.org/jdk/pull/23916.diff
Fetch: git fetch https://git.openjdk.org/jdk.git pull/23916/head:pull/23916
PR: https://git.openjdk.org/jdk/pull/23916
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