8276162: Optimise unsigned comparison pattern #6101

merykitty · 2021-10-25T10:15:42Z

This patch changes operations in the form x +- Integer.MIN_VALUE <=> y +- Integer.MIN_VALUE, which is a pattern used to do unsigned comparisons, into x u<=> y.

In addition to being basic operations, they may be utilised to implement range checks such as the methods in jdk.internal.util.Preconditions, or in places where the compiler cannot deduce the non-negativeness of the bound as in java.util.ArrayList.

Thank you very much.

Progress

Change must not contain extraneous whitespace
Commit message must refer to an issue
Change must be properly reviewed

Issue

JDK-8276162: Optimise unsigned comparison pattern

Reviewers

Tobias Hartmann (@TobiHartmann - Reviewer)
Vladimir Kozlov (@vnkozlov - Reviewer) ⚠️ Review applies to 4dada5f

Reviewing

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Checkout this PR locally:
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$ git checkout pull/6101

Update a local copy of the PR:
$ git checkout pull/6101
$ git pull https://git.openjdk.java.net/jdk pull/6101/head

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Checkout this PR locally:
$ git pr checkout 6101

View PR using the GUI difftool:
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Download this PR as a diff file:
https://git.openjdk.java.net/jdk/pull/6101.diff

bridgekeeper · 2021-10-25T10:15:59Z

Hi @merykitty, welcome to this OpenJDK project and thanks for contributing!

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merykitty · 2021-10-25T10:16:16Z

/signed

bridgekeeper · 2021-10-25T10:17:44Z

Thank you! Please allow for up to two weeks to process your OCA, although it is usually done within one to two business days. Also, please note that pull requests that are pending an OCA check will not usually be evaluated, so your patience is appreciated!

openjdk · 2021-10-25T10:17:47Z

@merykitty The following label will be automatically applied to this pull request:

hotspot-compiler

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.

DamonFool · 2021-10-29T03:59:27Z

It would be better if you can provide a micro benchmark to show us the performance improvement.
Thanks.

merykitty · 2021-10-29T07:23:56Z

I created a simple benchmark, the benchmark is run on Intel i7-7700HQ, the result is as follow:

Before:
Benchmark    Mode  Cnt  Score   Error  Units
App.runInt   avgt   25  3.963 ± 0.181  ns/op
App.runLong  avgt   25  4.431 ± 0.101  ns/op

After:
Benchmark    Mode  Cnt  Score   Error  Units
App.runInt   avgt   25  3.678 ± 0.192  ns/op
App.runLong  avgt   25  3.814 ± 0.085  ns/op

This is the source code of the benchmark:

package io.github.merykitty.simplebenchmark;

import java.io.IOException;
import java.util.concurrent.TimeUnit;

import org.openjdk.jmh.annotations.*;
import org.openjdk.jmh.infra.Blackhole;

@BenchmarkMode(Mode.AverageTime)
@State(Scope.Benchmark)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
@Warmup(iterations = 5)
@Measurement(iterations = 5)
public class App {
    @CompilerControl(CompilerControl.Mode.DONT_INLINE)
    public long test(int arg0, int arg1) {
        return arg0 + Integer.MIN_VALUE < arg1 + Integer.MIN_VALUE ? 1 : 0;
    }

    @CompilerControl(CompilerControl.Mode.DONT_INLINE)
    public long test(long arg0, long arg1) {
        return arg0 + Long.MIN_VALUE < arg1 + Long.MIN_VALUE ? 1 : 0;
    }

    @Benchmark
    public void runInt() {
        test(0, -1);
        test(-1, 0);
    }

    @Benchmark
    public void runLong() {
        test(0L, -1L);
        test(-1L, 0L);
    }

    public static void main( String[] args ) throws IOException {
        org.openjdk.jmh.Main.main(args);
    }
}

Do I need to add the benchmark to the patch? If yes then where should I put it in?

Thank you very much.

DamonFool · 2021-10-29T07:49:25Z

I created a simple benchmark, the benchmark is run on Intel i7-7700HQ, the result is as follow:

Before:
Benchmark    Mode  Cnt  Score   Error  Units
App.runInt   avgt   25  3.963 ± 0.181  ns/op
App.runLong  avgt   25  4.431 ± 0.101  ns/op

After:
Benchmark    Mode  Cnt  Score   Error  Units
App.runInt   avgt   25  3.678 ± 0.192  ns/op
App.runLong  avgt   25  3.814 ± 0.085  ns/op

This is the source code of the benchmark:

package io.github.merykitty.simplebenchmark;

import java.io.IOException;
import java.util.concurrent.TimeUnit;

import org.openjdk.jmh.annotations.*;
import org.openjdk.jmh.infra.Blackhole;

@BenchmarkMode(Mode.AverageTime)
@State(Scope.Benchmark)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
@Warmup(iterations = 5)
@Measurement(iterations = 5)
public class App {
    @CompilerControl(CompilerControl.Mode.DONT_INLINE)
    public long test(int arg0, int arg1) {
        return arg0 + Integer.MIN_VALUE < arg1 + Integer.MIN_VALUE ? 1 : 0;
    }

    @CompilerControl(CompilerControl.Mode.DONT_INLINE)
    public long test(long arg0, long arg1) {
        return arg0 + Long.MIN_VALUE < arg1 + Long.MIN_VALUE ? 1 : 0;
    }

    @Benchmark
    public void runInt() {
        test(0, -1);
        test(-1, 0);
    }

    @Benchmark
    public void runLong() {
        test(0L, -1L);
        test(-1L, 0L);
    }

    public static void main( String[] args ) throws IOException {
        org.openjdk.jmh.Main.main(args);
    }
}

Do I need to add the benchmark to the patch? If yes then where should I put it in?

Thank you very much.

I think you can put it under test/micro/org/openjdk/bench/vm/compiler with a more meaningful class name.
Please note that the jcheck failed in your PR, which seems to prevent the RFR email from sending out.

merykitty · 2021-10-29T08:37:48Z

I have just pushed the microbenchmark, I am not sure what to put in the copyright line, though.

The check failure seems to be due to this PR does not refer to an existing issue.

Thank you very much.

DamonFool · 2021-10-29T09:38:37Z

I have just pushed the microbenchmark, I am not sure what to put in the copyright line, though.

The check failure seems to be due to this PR does not refer to an existing issue.

Thank you very much.

Filed https://bugs.openjdk.java.net/browse/JDK-8276162 for you.
Thanks.

mlbridge · 2021-10-29T09:48:32Z

Webrevs

merykitty · 2021-11-10T09:21:48Z

Hi, may someone take a look at this PR, please.
Thank you very much.

src/hotspot/share/opto/subnode.cpp

test/micro/org/openjdk/bench/vm/compiler/UnsignedComparison.java

src/hotspot/share/opto/subnode.cpp

vnkozlov · 2021-11-10T20:37:53Z

src/hotspot/share/opto/subnode.cpp

+  const int cmp1_op = cmp1->Opcode();
+  const int cmp2_op = cmp2->Opcode();
+
+  // Change x +- Integer.MIN_VALUE <=> y +- Integer.MIN_VALUE into x u<=> y


The comment should include cmp2_op == Op_ConI case.
Also it is not clear from comment and code if different operations are allowed on both side: x - MIN_INT <= y + MIN_INT

vnkozlov · 2021-11-10T20:37:53Z

src/hotspot/share/opto/subnode.cpp

+      (cmp1_op == Op_AddI || cmp1_op == Op_SubI) &&
+      phase->type(cmp1->in(2)) == TypeInt::MIN) {
+    if (cmp2_op == Op_ConI) {
+      Node *ncmp2 = phase->intcon(java_add(cmp2->get_int(), min_jint));


What if cmp1_op == Op_SubI ?

Since x + MIN_VALUE == x - MIN_VALUE, the operation is the same with addition and subtraction operations. However, I realised that x - MIN_VALUE is idealised into x + MIN_VALUE beforehand, so I have removed the check for Op_SubI here.

vnkozlov · 2021-11-10T20:37:53Z

src/hotspot/share/opto/subnode.cpp

+      Node *ncmp2 = phase->intcon(java_add(cmp2->get_int(), min_jint));
+      Node *ncmp = phase->transform(new CmpUNode(cmp1->in(1), ncmp2));
+      return new BoolNode(ncmp, _test._test);
+    } else if ((cmp2_op == Op_AddI || cmp2_op == Op_SubI) &&


Again the question about mismatching cmp1_op and cmp2_op.

TobiHartmann

Given that there is Integer/Long.compareUnsigned using this idiom, it seems reasonable to optimize. Some general comments:

Your benchmark does not cover all the cases you are optimizing. Maybe you should also add the Integer.compareUnsigned variants.
You need a correctness test as well, ideally using the IR verification framework to also verify that the optimizations are actually performed.

TobiHartmann · 2021-11-11T08:33:25Z

src/hotspot/share/opto/subnode.cpp

@@ -1529,10 +1531,43 @@ Node *BoolNode::Ideal(PhaseGVN *phase, bool can_reshape) {
    }
  }

+  // Change x + Integer.MIN_VALUE <=> y + Integer.MIN_VALUE into x u<=> y


The <=> in the comment is confusing because it usually denotes logical equality. Also, you are only handling < and > below. What about the other variants? Shouldn't they be canonicalized in idealize_test (see ifnode.cpp)?

I would recommend making it explicit in the comment and use brackets for readability:

// Change (x + Integer.MIN_VALUE < y + Integer.MIN_VALUE) into (x u< y) and // (x + Integer.MIN_VALUE > y + Integer.MIN_VALUE) into (x u> y).

I have added eq and ne to the transformation, leaving the comment simply as cmp (add X min_jint) (add Y min_jint).

TobiHartmann · 2021-11-11T08:33:25Z

src/hotspot/share/opto/subnode.cpp

+      return new BoolNode(ncmp, _test._test);
+    } else if (cmp2_op == Op_AddI &&
+               phase->type(cmp2->in(2)) == TypeInt::MIN) {
+      Node *ncmp = phase->transform(new CmpUNode(cmp1->in(1), cmp2->in(1)));


Node *ncmp -> Node* ncmp

vnkozlov

Thank you for addressing my comments.

I am tentatively approve these changes leaving final approval and testing to @TobiHartmann

openjdk · 2021-11-12T17:32:10Z

⚠️ @merykitty the full name on your profile does not match the author name in this pull requests' HEAD commit. If this pull request gets integrated then the author name from this pull requests' HEAD commit will be used for the resulting commit. If you wish to push a new commit with a different author name, then please run the following commands in a local repository of your personal fork:

$ git checkout compareUnsignedMatcher
$ git commit -c user.name='Preferred Full Name' --allow-empty -m 'Update full name'
$ git push

openjdk · 2021-11-12T17:32:14Z

@merykitty This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8276162: Optimise unsigned comparison pattern

Reviewed-by: thartmann, kvn

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 297 new commits pushed to the master branch:

9a9a157: 8276905: Use appropriate macosx_version_minimum value while compiling metal shaders
7906eb0: 8277119: Add asserts in GenericTaskQueueSet methods
1c45c8a: 8274757: Cleanup unnecessary calls to Throwable.initCause() in java.management module
c06df25: 8274662: Replace 'while' cycles with iterator with enhanced-for in jdk.hotspot.agent
9629627: 8274163: Use String.equals instead of String.compareTo in jdk.jcmd
0bc2683: 8274190: Use String.equals instead of String.compareTo in jdk.internal.jvmstat
a9cb8bd: 8274168: Avoid String.compareTo == 0 to check String equality in java.management
20f3872: 8274261: Use enhanced-for instead of plain 'for' in jdk.jcmd
b8d33a2: 8277029: JMM GetDiagnosticXXXInfo APIs should verify output array sizes
1d79cfd: 8276229: Stop allowing implicit updates in G1BlockOffsetTable
... and 287 more: https://git.openjdk.java.net/jdk/compare/5bbe4cae8746765d2ce965b06fd1e5cf512326ae...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

As you do not have Committer status in this project an existing Committer must agree to sponsor your change. Possible candidates are the reviewers of this PR (@TobiHartmann, @vnkozlov) but any other Committer may sponsor as well.

➡️ To flag this PR as ready for integration with the above commit message, type /integrate in a new comment. (Afterwards, your sponsor types /sponsor in a new comment to perform the integration).

merykitty · 2021-11-13T05:22:56Z

@TobiHartmann Thank you very much for the review, I have added the correctness test as well as revised the microbenchmark to cover all the situations including calling to [Integer/Long].compareUnsigned. The result of the benchmark is as follow:

Before:
Benchmark                         Mode  Cnt     Score    Error  Units
UnsignedComparison.intConDirect   avgt   10   927.540 ± 19.142  ns/op
UnsignedComparison.intConLibGT    avgt   10   916.753 ±  4.502  ns/op
UnsignedComparison.intConLibLT    avgt   10   927.911 ± 15.027  ns/op
UnsignedComparison.intVarDirect   avgt   10  1005.895 ± 14.030  ns/op
UnsignedComparison.intVarLibGT    avgt   10   999.216 ±  1.528  ns/op
UnsignedComparison.intVarLibLT    avgt   10  1000.501 ±  4.117  ns/op
UnsignedComparison.longConDirect  avgt   10  1082.950 ±  8.166  ns/op
UnsignedComparison.longConLibGT   avgt   10  1081.340 ±  6.883  ns/op
UnsignedComparison.longConLibLT   avgt   10  1079.599 ±  4.229  ns/op
UnsignedComparison.longVarDirect  avgt   10  1131.605 ± 76.268  ns/op
UnsignedComparison.longVarLibGT   avgt   10  1180.006 ±  7.018  ns/op
UnsignedComparison.longVarLibLT   avgt   10  1178.463 ±  0.809  ns/op

After:
Benchmark                         Mode  Cnt    Score    Error  Units
UnsignedComparison.intConDirect   avgt   10  740.951 ±  5.020  ns/op
UnsignedComparison.intConLibGT    avgt   10  808.425 ±  2.989  ns/op
UnsignedComparison.intConLibLT    avgt   10  740.029 ±  1.332  ns/op
UnsignedComparison.intVarDirect   avgt   10  911.489 ±  4.700  ns/op
UnsignedComparison.intVarLibGT    avgt   10  979.338 ±  8.130  ns/op
UnsignedComparison.intVarLibLT    avgt   10  910.429 ±  3.452  ns/op
UnsignedComparison.longConDirect  avgt   10  750.174 ±  5.915  ns/op
UnsignedComparison.longConLibGT   avgt   10  828.144 ± 53.091  ns/op
UnsignedComparison.longConLibLT   avgt   10  771.493 ± 52.902  ns/op
UnsignedComparison.longVarDirect  avgt   10  882.139 ±  2.091  ns/op
UnsignedComparison.longVarLibGT   avgt   10  952.862 ± 10.248  ns/op
UnsignedComparison.longVarLibLT   avgt   10  881.623 ±  1.895  ns/op

TobiHartmann

Nice IR verification test. Your changes look good to me and all testing passed.

merykitty · 2021-11-16T13:42:41Z

/integrate

openjdk · 2021-11-16T13:44:29Z

@merykitty
Your change (at version 92e92cf) is now ready to be sponsored by a Committer.

merykitty · 2021-11-16T13:57:49Z

Thank @vnkozlov and @TobiHartmann for your reviews and suggestions, thank @DamonFool for your initial supports.
May I have this PR sponsored, please?

Thank you very much.

TobiHartmann · 2021-11-16T14:08:57Z

/sponsor

openjdk · 2021-11-16T14:10:12Z

Going to push as commit f3eb501.
Since your change was applied there have been 297 commits pushed to the master branch:

9a9a157: 8276905: Use appropriate macosx_version_minimum value while compiling metal shaders
7906eb0: 8277119: Add asserts in GenericTaskQueueSet methods
1c45c8a: 8274757: Cleanup unnecessary calls to Throwable.initCause() in java.management module
c06df25: 8274662: Replace 'while' cycles with iterator with enhanced-for in jdk.hotspot.agent
9629627: 8274163: Use String.equals instead of String.compareTo in jdk.jcmd
0bc2683: 8274190: Use String.equals instead of String.compareTo in jdk.internal.jvmstat
a9cb8bd: 8274168: Avoid String.compareTo == 0 to check String equality in java.management
20f3872: 8274261: Use enhanced-for instead of plain 'for' in jdk.jcmd
b8d33a2: 8277029: JMM GetDiagnosticXXXInfo APIs should verify output array sizes
1d79cfd: 8276229: Stop allowing implicit updates in G1BlockOffsetTable
... and 287 more: https://git.openjdk.java.net/jdk/compare/5bbe4cae8746765d2ce965b06fd1e5cf512326ae...master

Your commit was automatically rebased without conflicts.

openjdk · 2021-11-16T14:10:35Z

@TobiHartmann @merykitty Pushed as commit f3eb501.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

TobiHartmann · 2021-11-17T08:11:44Z

This introduced a regression on 32-bit x86, @merykitty could you please have a look?
JDK-8277324

TobiHartmann · 2021-11-17T09:27:37Z

The problem is missing match rules on x86-32: #6427

DamonFool · 2021-12-02T06:57:15Z

This introduced a regression on 32-bit x86 for Vector API tests, could someone help to review it?
#6533
Thanks.

merykitty added 2 commits Oct 25, 2021

unsigned comparison optimisation

c783acf

remove long optimisation

6ee7042

bridgekeeper bot added the oca label Oct 25, 2021

bridgekeeper bot added the oca-verify label Oct 25, 2021

openjdk bot added the hotspot-compiler label Oct 25, 2021

merykitty added 2 commits Oct 25, 2021

use min_jint instead of TypeInt::MIN->get_con()

c490d72

add long unsigned comparison

ed97b95

bridgekeeper bot removed oca oca-verify labels Oct 28, 2021

add microbenchmark

426abe8

merykitty changed the title ~~Optimise unsigned comparison pattern~~ 8276162: Optimise unsigned comparison pattern Oct 29, 2021

openjdk bot added the rfr label Oct 29, 2021

fix copyright declaration

69842df

vnkozlov reviewed Nov 10, 2021

View changes

merykitty added 2 commits Nov 11, 2021

address reviews, remove checks for subtraction operatios

88722be

replace cmpx->Opcode() with cmpx_op

4dada5f

TobiHartmann suggested changes Nov 11, 2021

View changes

add eq/ne, add correction test, refine micro

4cb9faf

vnkozlov approved these changes Nov 12, 2021

View changes

openjdk bot added the ready label Nov 12, 2021

add tests cover constant comparison and calling library

92e92cf

TobiHartmann approved these changes Nov 16, 2021

View changes

openjdk bot added the sponsor label Nov 16, 2021

openjdk bot closed this Nov 16, 2021

openjdk bot added integrated and removed ready rfr sponsor labels Nov 16, 2021

merykitty deleted the compareUnsignedMatcher branch Nov 30, 2021

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8276162: Optimise unsigned comparison pattern #6101

8276162: Optimise unsigned comparison pattern #6101

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8276162: Optimise unsigned comparison pattern #6101

8276162: Optimise unsigned comparison pattern #6101

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merykitty commented Oct 25, 2021 • edited by openjdk[bot] bot

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Webrevs

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