RFR: 8334843: RISC-V: Fix wraparound checking for r_array_index in lookup_secondary_supers_table_slow_path

[Gui Cao]

On Mon, 24 Jun 2024 09:25:31 GMT, Gui Cao <gcao at openjdk.org> wrote:

> Branch condition for r_array_index wraparound checking in lookup_secondary_supers_table_slow_path is wrong.
> 
>     // Check for wraparound.
>     Label skip;
>     bge(r_array_length, r_array_index, skip);
>     mv(r_array_index, zr);
>     bind(skip);
> 
> As discussed at https://github.com/openjdk/jdk/pull/19320/files#r1650548279 . If length == index, then we must set index to 0. That is `blt(r_array_index,r_array_length,skip);`.
> 
> ### Correctness testing:
> - [ ] Run tier1-3 tests on SOPHON SG2042 (release)
> 
> ### JMH tested on SOPHON SG2042 (has not Zbb)
> without this patch:
> 
> Benchmark                             Mode  Cnt    Score   Error  Units
> SecondarySupersLookup.testNegative00  avgt   15   20.649 ± 0.147  ns/op
> SecondarySupersLookup.testNegative01  avgt   15   20.649 ± 0.117  ns/op
> SecondarySupersLookup.testNegative02  avgt   15   20.637 ± 0.116  ns/op
> SecondarySupersLookup.testNegative03  avgt   15   20.638 ± 0.113  ns/op
> SecondarySupersLookup.testNegative04  avgt   15   20.638 ± 0.127  ns/op
> SecondarySupersLookup.testNegative05  avgt   15   20.639 ± 0.115  ns/op
> SecondarySupersLookup.testNegative06  avgt   15   20.638 ± 0.119  ns/op
> SecondarySupersLookup.testNegative07  avgt   15   20.850 ± 0.457  ns/op
> SecondarySupersLookup.testNegative08  avgt   15   20.842 ± 0.459  ns/op
> SecondarySupersLookup.testNegative09  avgt   15   20.650 ± 0.124  ns/op
> SecondarySupersLookup.testNegative10  avgt   15   20.642 ± 0.127  ns/op
> SecondarySupersLookup.testNegative16  avgt   15   20.657 ± 0.157  ns/op
> SecondarySupersLookup.testNegative20  avgt   15   20.669 ± 0.152  ns/op
> SecondarySupersLookup.testNegative30  avgt   15   20.668 ± 0.166  ns/op
> SecondarySupersLookup.testNegative32  avgt   15   20.669 ± 0.168  ns/op
> SecondarySupersLookup.testNegative40  avgt   15   20.668 ± 0.174  ns/op
> SecondarySupersLookup.testNegative50  avgt   15   20.682 ± 0.194  ns/op
> SecondarySupersLookup.testNegative55  avgt   15  113.369 ± 3.792  ns/op
> SecondarySupersLookup.testNegative56  avgt   15  113.888 ± 3.769  ns/op
> SecondarySupersLookup.testNegative57  avgt   15  115.320 ± 4.271  ns/op
> SecondarySupersLookup.testNegative58  avgt   15  115.648 ± 2.985  ns/op
> SecondarySupersLookup.testNegative59  avgt   15  117.730 ± 3.370  ns/op
> SecondarySupersLookup.testNegative60  avgt   15  142.533 ± 3.636  ns/op
> SecondarySupersLookup.testNegative61  avgt   15  144.901 ± 5.267  ns/op
> SecondarySupersLookup.testNegative62  avgt   15  145.926 ± 3.799  ns/op
> SecondarySupersLookup.testNegative63  avgt   15  207.704 ± 5....

@theRealAph Could you please take a look？

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PR Comment: https://git.openjdk.org/jdk/pull/19852#issuecomment-2186684595