RFR 8248043: Need to eliminate excessive i2l conversions

[Igor Veresov]

> 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
>>> 
>>> 
>>> 
>>>