RFR 8248043: Need to eliminate excessive i2l conversions

[Boris Ulasevich]

Hi Igor,

By BoolNode I mean the canonicalization that is already in place:
https://hg.openjdk.java.net/jdk/jdk/file/de6ad5f86276/src/hotspot/share/opto/subnode.cpp#l1391

thanks,
Boris

On Wed, Jul 1, 2020 at 5:07 AM Igor Veresov <igor.veresov at oracle.com> wrote:

> I think you forgot to include changes to BoolNode in the webrev.
>
> igor
>
>
>
> On Jun 30, 2020, at 11:04 AM, Boris Ulasevich <boris.ulasevich at bell-sw.com>
> wrote:
>
> Hi Claes,
>
> > Seems like the optimization is mostly effective, but not getting all the
> way.
>
> Good point about LHS, thanks! CmpL turned to be not canonized on the
> moment.
> I moved the optimization to CmpLNode::Ideal and transformations now works
> as follows:
> 1. CmpINode::Ideal: CmpI(CmpL3)->CmpL
> 2. BoolNode::Ideal:
> Bool(CmpL(const,val),test)->Bool(CmpL(val,const),test_invert)
> 3. CmpLNode::Ideal: CmpL(ConvI2L(val),ConL)->CmpI(val,ConI)
>
> I applied your test to the benchmark. The result is:
> Benchmark                            Mode  Cnt   Score   Error Units
> SkipIntToLongCast.skipCastTestLeft   avgt    5  14.288 ± 0.052 ns/op
> SkipIntToLongCast.skipCastTestRight  avgt    5  14.338 ± 0.088 ns/op
>
> Updated webrev:
> http://cr.openjdk.java.net/~bulasevich/8248043/webrev.02b
>
> thanks,
> Boris
>
> On 26.06.2020 21:31, Claes Redestad wrote:
>
> Hi Boris,
>
> this looks like a nice improvement! I just have some comments about the
> micro.
>
> I was curious whether the optimization works when the constant is on
> the LHS and added a variant of the micro to try that[1]. Results are
> interesting (Intel Xeon):
>
> Benchmark                            Mode  Cnt   Score   Error Units
> SkipIntToLongCast.skipCastTest       avgt    5  30.937 ± 0.056 ns/op
> SkipIntToLongCast.skipCastTestLeft   avgt    5  30.937 ± 0.140 ns/op
>
> With your patch:
> Benchmark                            Mode  Cnt   Score   Error Units
> SkipIntToLongCast.skipCastTest       avgt    5  14.123 ± 0.035 ns/op
> SkipIntToLongCast.skipCastTestLeft   avgt    5  17.420 ± 0.044 ns/op
>
> Seems like the optimization is mostly effective, but not getting all
> the way. I wouldn't worry about it for this RFE, but perhaps something
> to investigate in a follow-up. Feel free to include such a variant in
> your patch though (no attribution necessary).
>
> The micro also stabilizes very quickly, so you might want to provide
> some default tuning to keep runtime in check, e.g., something like:
>
> @Warmup(iterations = 10, time = 500, timeUnit = TimeUnit.MILLISECONDS)
> @Measurement(iterations = 5, time = 1000, timeUnit = TimeUnit.MILLISECONDS)
> @Fork(3)
>
> Thanks!
>
> /Claes
>
> [1]
>     @Benchmark
>     public int skipCastTestLeft() {
>         for (int i = 0; i < ARRAYSIZE_L; i++) {
>             if (ARRAYSIZE_L == intValues[i]) {
>                 return i;
>             }
>         }
>         return 0;
>     }
>
> On 2020-06-26 17:05, Boris Ulasevich wrote:
>
> Hi all,
>
> Please review the change to eliminate the unnecessary i2l conversion
> for expressions like this: "if (intValue == 1L)".
>
> http://bugs.openjdk.java.net/browse/JDK-8248043
> http://cr.openjdk.java.net/~bulasevich/8248043/webrev.01
>
> The provided benchmark shows performance boost on all platforms:
> - Intel Xeon: 32.705 --> 14.234 ns/op
> - arm64: 42.060 --> 25.456 ns/op
> - arm32: 618.763 --> 314.040 ns/op
> - ppc8:  81.218 --> 63.026 ns/op
>
> Testing done: jtreg, jck.
>
> thanks,
> Boris
>
>
>
>