RFR: 8360520: RISC-V: C1: Fix primitive array clone intrinsic regression after JDK-8333154 [v2]
Feilong Jiang
fjiang at openjdk.org
Fri Jun 27 01:03:48 UTC 2025
On Thu, 26 Jun 2025 14:27:21 GMT, Feilong Jiang <fjiang at openjdk.org> wrote:
>> Hi, please consider.
>> [JDK-8333154](https://bugs.openjdk.org/browse/JDK-8333154) Implemented C1 clone intrinsic that reuses arraycopy code for primitive arrays for RISC-V.
>> The new instruction flag `OmitChecksFlag` (introduced by [JDK-8302850](https://bugs.openjdk.org/browse/JDK-8302850)) is used to avoid instantiation of array copy stubs for primitive array clones.
>> If `OmitChecksFlag` is set, all flags (including the `unaligned` flag) will be cleared before generating the `LIR_OpArrayCopy` node.
>> This may lead to incorrect selection of the arraycopy function when `-XX:+UseCompactObjectHeaders` is enabled, causing the `unaligned` flag to be set for arraycopy.
>> We observed performance regression on P550 SBC through the corresponding JMH tests when COH is enabled.
>>
>> This pr keeps the `unaligned` flag on RISC-V to ensure the arraycopy function is selected correctly. And keep the flag of other platforms always be `0` when `OmitChecksFlag` is true.
>>
>> Test on linux-riscv64:
>> - [ ] Tier1-3
>>
>> JMH data on P550 SBC for reference (w/o and w/ the patch):
>>
>> Before:
>>
>> Without COH:
>>
>> Benchmark (size) Mode Cnt Score Error Units
>> ArrayClone.byteArraycopy 0 avgt 15 50.854 ± 0.379 ns/op
>> ArrayClone.byteArraycopy 10 avgt 15 74.294 ± 0.449 ns/op
>> ArrayClone.byteArraycopy 100 avgt 15 81.847 ± 0.082 ns/op
>> ArrayClone.byteArraycopy 1000 avgt 15 480.106 ± 0.369 ns/op
>> ArrayClone.byteClone 0 avgt 15 90.146 ± 0.299 ns/op
>> ArrayClone.byteClone 10 avgt 15 130.525 ± 0.384 ns/op
>> ArrayClone.byteClone 100 avgt 15 251.942 ± 0.122 ns/op
>> ArrayClone.byteClone 1000 avgt 15 407.580 ± 0.318 ns/op
>> ArrayClone.intArraycopy 0 avgt 15 49.984 ± 0.436 ns/op
>> ArrayClone.intArraycopy 10 avgt 15 76.302 ± 1.388 ns/op
>> ArrayClone.intArraycopy 100 avgt 15 267.487 ± 0.329 ns/op
>> ArrayClone.intArraycopy 1000 avgt 15 1157.444 ± 1.588 ns/op
>> ArrayClone.intClone 0 avgt 15 90.130 ± 0.257 ns/op
>> ArrayClone.intClone 10 avgt 15 183.619 ± 0.588 ns/op
>> ArrayClone.intClone 100 avgt 15 296.491 ± 0.246 ns/op
>> ArrayClone.intClone 1000 avgt 15 828.695 ± 1.501 ns/op
>>
>> -------------------------------------------------------------------------
>> With COH:
>>
>> Benchmark (size) Mode Cnt Score Error Units
>> ArrayClon...
>
> Feilong Jiang 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 three additional commits since the last revision:
>
> - Merge branch 'master' of https://github.com/openjdk/jdk into riscv-fix-c1-primitive-clone
> - check unaligned flag at LIR_OpArrayCopy to avoid using AvoidUnalignedAccesses
> - riscv: fix c1 primitive array clone intrinsic regression
Since this changed C1 shared code, can I have another reviewer, please? Maybe the original author of this work @galderz @rwestrel could take a look?
-------------
PR Comment: https://git.openjdk.org/jdk/pull/25976#issuecomment-3010950199
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