RFR 8248043: Need to eliminate excessive i2l conversions

[Boris Ulasevich]

Hi,

I'm deeply sorry. Yes, webrev.02b is certainly wrong!
Correct link is webrev.02c:
http://cr.openjdk.java.net/~bulasevich/8248043/webrev.02
<http://cr.openjdk.java.net/~bulasevich/8248043/webrev.02b/src/hotspot/share/opto/subnode.cpp.udiff.html>
c
- this is the change I described in my mail and wanted to review.

my apologies,
Boris

On Wednesday, July 1, 2020, Igor Veresov <igor.veresov at oracle.com> wrote:

> > On Jun 30, 2020, at 10:15 PM, Vladimir Kozlov <
> vladimir.kozlov at oracle.com> wrote:
> >
> > I think Igor said that you can't swap arguments of compare without
> changing condition test. For example, if it was CC_LT it should be CC_GT
> after swap.
>
> Yes, that’s exactly what I had in mind.  Condition must be inverted.
> Otherwise your transformation [3] is not valid for anything else but
> equality, so that’s not going to work. May be if [3] didn’t work, perhaps
> there is another user of  the CmpLNode in addition to BoolNode ?
>
> igor
>
> >
> > It is not clear why you need swapping in CmpLNode::Ideal() if
> BoolNode::Ideal() should do it already. If it does not you need to
> investigate why.
> >
> > Also your list of steps 1.-3. does not reflect changes in webrev.02b:
> > http://cr.openjdk.java.net/~bulasevich/8248043/webrev.02b/
> src/hotspot/share/opto/subnode.cpp.udiff.html
> >
> > Regards,
> > Vladimir
> >
> > On 6/30/20 9:33 PM, Boris Ulasevich wrote:
> >> 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
> >>>
> >>>
> >>>
> >>>
>
>