RFR: 8294198: Implement isFinite intrinsic for RISC-V

[Aleksei Voitylov]

On Thu, 22 Sep 2022 17:20:02 GMT, Joe Darcy <darcy at openjdk.org> wrote:

>> Unlike on x86 (see 8285868 and the discussion in review), isFinite intrinsic turned out to be profitable on RISC-V using the same fclass instruction as for 8293695 (isInfinite instrinsic). Therefore, I'm proposing to have it added on RISC-V in this PR.
>> 
>> benchmark results:
>> 
>> before:
>> 
>> Benchmark                              Mode  Cnt   Score   Error  Units
>> DoubleClassCheck.testIsFiniteBranch    avgt   15  52.824 ± 1.744  ns/op
>> DoubleClassCheck.testIsFiniteCMov      avgt   15  16.104 ± 0.358  ns/op
>> DoubleClassCheck.testIsFiniteStore     avgt   15  14.366 ± 2.174  ns/op
>> FloatClassCheck.testIsFiniteBranch     avgt   15  49.821 ± 0.330  ns/op
>> FloatClassCheck.testIsFiniteCMov       avgt   15  14.702 ± 0.335  ns/op
>> FloatClassCheck.testIsFiniteStore      avgt   15  14.749 ± 0.496  ns/op
>> 
>> after:
>> 
>> DoubleClassCheck.testIsFiniteBranch    avgt   15  48.921 ± 0.557  ns/op
>> DoubleClassCheck.testIsFiniteCMov      avgt   15  13.716 ± 0.304  ns/op
>> DoubleClassCheck.testIsFiniteStore     avgt   15   9.152 ± 0.158  ns/op
>> FloatClassCheck.testIsFiniteBranch     avgt   15  47.740 ± 2.028  ns/op
>> FloatClassCheck.testIsFiniteCMov       avgt   15  13.299 ± 0.282  ns/op
>> FloatClassCheck.testIsFiniteStore      avgt   15   9.185 ± 0.396  ns/op
>> 
>> Existing isInfinite jtreg test was altered to be able to use common code for isFinite test and fine-grained requires tag filtering. Existing benchmark was modified to include isFinite case. A typo ("Atleast" -> "At least") was fixed on the way.
>> 
>> Test passed on both release and fastdebug builds. Hotspot tier1 tests were run on x86_64 and RISC-V with no issues.
>
> The java.lang.* changes look fine if the rest of the work proceeds.

Thank you @jddarcy @RealFYang @vnkozlov for your reviews.

I also ran the benchmarks with -XX:LoopUnrollLimit=0 -XX:LoopMaxUnroll=0 and see the improvement with these flags as well.

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PR: https://git.openjdk.org/jdk/pull/10391