8294816: C2: Math.min/max vectorization miscompilation #10944

Bhavana-Kilambi · 2022-11-02T12:06:14Z

C2 miscompiles during auto-vectorization of MinI/MaxI nodes when "short" type operands are involved. When a short and an integer value is compared, C2 generates vector min/max nodes for "short" types which does not result in correct output as it disregards the higher order bits of the integer input. Java API for Math.min/max also only supports the int, long, float and double types but not the subword integer types namely - char, byte and short. Hence, char/short/byte min/max vector instructions should not be generated.
This patch ensures that MaxV and MinV vector nodes are only generated for the "int" type for MaxI and MinI nodes during auto-vectorization.

Progress

Change must be properly reviewed (1 review required, with at least 1 Reviewer)
Change must not contain extraneous whitespace
Commit message must refer to an issue

Issue

JDK-8294816: C2: Math.min/max vectorization miscompilation

Reviewers

Tobias Hartmann (@TobiHartmann - Reviewer)
Nick Gasson (@nick-arm - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk pull/10944/head:pull/10944
$ git checkout pull/10944

Update a local copy of the PR:
$ git checkout pull/10944
$ git pull https://git.openjdk.org/jdk pull/10944/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 10944

View PR using the GUI difftool:
$ git pr show -t 10944

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/10944.diff

C2 miscompiles during auto-vectorization of MinI/MaxI nodes when "short" type operands are involved. When a short and an integer value is compared, C2 generates vector min/max nodes for "short" types which does not result in correct output as it disregards the higher order bits of the integer input. Java API for Math.min/max also only supports the int, long, float and double types but not the subword integer types namely - char, byte and short. Hence, char/short/byte min/max vector instructions should not be generated. This patch ensures that MaxV and MinV vector nodes are only generated for the "int" type for MaxI and MinI nodes during auto-vectorization.

bridgekeeper · 2022-11-02T12:08:15Z

👋 Welcome back bkilambi! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

openjdk · 2022-11-02T12:10:29Z

@Bhavana-Kilambi 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.

mlbridge · 2022-11-02T12:13:20Z

Webrevs

01: Full - Incremental (74d9886c)
00: Full (064dbc1e)

TobiHartmann

Looks good to me. I'll run testing and report back once it passed.

openjdk · 2022-11-02T12:31:23Z

@Bhavana-Kilambi 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:

8294816: C2: Math.min/max vectorization miscompilation

Reviewed-by: thartmann, ngasson

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 46 new commits pushed to the master branch:

c206f28: 8283101: serviceability/jvmti/thread/GetFrameCount/framecnt01/framecnt01.java failing #VirtualThread-Frozen: number of frames expected: 14, got: 9
97c5a64: 8296287: Improve documentation for Types.directSupertypes()
f9c7cda: 8294109: JavaDoc search should search whole index
5622b09: 8200337: Generalize see and link tags for user-defined anchors
22347e4: 8277775: Fixup bugids in RemoveDropTargetCrashTest.java - add 4357905
1231682: 8296305: Remove unimplemented deoptimized_wrt_marked_nmethods
3378bfe: 8296224: G1: Remove unnecessary update in VM_G1CollectForAllocation
8ee0f7d: 8296231: Fix MEMFLAGS for CHeapBitMaps
bd729e6: 8296380: IGV: Shortcut for quick search not working
c116ae7: 8295967: RISC-V: Support negVI/negVL instructions for Vector API
... and 36 more: https://git.openjdk.org/jdk/compare/1a58cb1c023c876594e8a53d00703e564a922d36...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, @nick-arm) 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).

TobiHartmann · 2022-11-02T13:37:46Z

test/hotspot/jtreg/compiler/c2/TestMinMaxSubword.java

+    // as Java APIs for Math.min/max do not support integer subword types and superword
+    // should not generate vectorized Min/Max nodes for them.
+    @Test
+    @IR(failOn = {IRNode.Min_V})


The test currently fails compilation because the IRNodes were renamed by #10695 to MIN_V.

Thanks for letting me know. I have updated the code accordingly. Please review..

TobiHartmann

All tests passed. Looks good to me.

Bhavana-Kilambi · 2022-11-04T14:31:44Z

/integrate

openjdk · 2022-11-04T14:33:58Z

@Bhavana-Kilambi
Your change (at version 74d9886) is now ready to be sponsored by a Committer.

nick-arm · 2022-11-04T17:20:51Z

/sponsor

openjdk · 2022-11-04T17:23:09Z

Going to push as commit b49bdae.
Since your change was applied there have been 46 commits pushed to the master branch:

c206f28: 8283101: serviceability/jvmti/thread/GetFrameCount/framecnt01/framecnt01.java failing #VirtualThread-Frozen: number of frames expected: 14, got: 9
97c5a64: 8296287: Improve documentation for Types.directSupertypes()
f9c7cda: 8294109: JavaDoc search should search whole index
5622b09: 8200337: Generalize see and link tags for user-defined anchors
22347e4: 8277775: Fixup bugids in RemoveDropTargetCrashTest.java - add 4357905
1231682: 8296305: Remove unimplemented deoptimized_wrt_marked_nmethods
3378bfe: 8296224: G1: Remove unnecessary update in VM_G1CollectForAllocation
8ee0f7d: 8296231: Fix MEMFLAGS for CHeapBitMaps
bd729e6: 8296380: IGV: Shortcut for quick search not working
c116ae7: 8295967: RISC-V: Support negVI/negVL instructions for Vector API
... and 36 more: https://git.openjdk.org/jdk/compare/1a58cb1c023c876594e8a53d00703e564a922d36...master

Your commit was automatically rebased without conflicts.

openjdk · 2022-11-04T17:23:31Z

@nick-arm @Bhavana-Kilambi Pushed as commit b49bdae.

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

openjdk bot added the rfr Pull request is ready for review label Nov 2, 2022

openjdk bot added the hotspot-compiler hotspot-compiler-dev@openjdk.org label Nov 2, 2022

Bhavana-Kilambi mentioned this pull request Nov 2, 2022

8288107: Auto-vectorization for integer min/max #9466

Closed

3 tasks

TobiHartmann approved these changes Nov 2, 2022

View reviewed changes

openjdk bot added the ready Pull request is ready to be integrated label Nov 2, 2022

TobiHartmann suggested changes Nov 2, 2022

View reviewed changes

openjdk bot removed the ready Pull request is ready to be integrated label Nov 2, 2022

Updated string names for Min and Max IR nodes

74d9886

TobiHartmann approved these changes Nov 4, 2022

View reviewed changes

openjdk bot added the ready Pull request is ready to be integrated label Nov 4, 2022

openjdk bot added the sponsor Pull request is ready to be sponsored label Nov 4, 2022

nick-arm approved these changes Nov 4, 2022

View reviewed changes

openjdk bot added the integrated Pull request has been integrated label Nov 4, 2022

openjdk bot closed this Nov 4, 2022

openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review sponsor Pull request is ready to be sponsored labels Nov 4, 2022

8294816: C2: Math.min/max vectorization miscompilation #10944

8294816: C2: Math.min/max vectorization miscompilation #10944

Uh oh!

Conversation

Bhavana-Kilambi commented Nov 2, 2022 • edited by openjdk bot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Progress

Issue

Reviewers

Reviewing

Uh oh!

bridgekeeper bot commented Nov 2, 2022

Uh oh!

openjdk bot commented Nov 2, 2022

Uh oh!

mlbridge bot commented Nov 2, 2022 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Webrevs

Uh oh!

TobiHartmann left a comment

Choose a reason for hiding this comment

Uh oh!

openjdk bot commented Nov 2, 2022 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

TobiHartmann Nov 2, 2022

Choose a reason for hiding this comment

Uh oh!

Bhavana-Kilambi Nov 2, 2022

Choose a reason for hiding this comment

Uh oh!

TobiHartmann left a comment

Choose a reason for hiding this comment

Uh oh!

Bhavana-Kilambi commented Nov 4, 2022

Uh oh!

openjdk bot commented Nov 4, 2022

Uh oh!

nick-arm commented Nov 4, 2022

Uh oh!

openjdk bot commented Nov 4, 2022

Uh oh!

openjdk bot commented Nov 4, 2022

Uh oh!

Reviewers

Assignees

Labels

Milestone

Development

Uh oh!

3 participants

Bhavana-Kilambi commented Nov 2, 2022 •

edited by openjdk bot

Loading

mlbridge bot commented Nov 2, 2022 •

edited

Loading

openjdk bot commented Nov 2, 2022 •

edited

Loading