8339063: [aarch64] Skip verify_sve_vector_length after native calls if SVE supports 128 bits VL only #20724

JoshuaZhuwj · 2024-08-27T09:28:52Z

Please review this minor enhancement that skips verify_sve_vector_length after native calls.
It works on SVE micro-architecture that only supports 128-bit vector length.

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Issue

JDK-8339063: [aarch64] Skip verify_sve_vector_length after native calls if SVE supports 128 bits VL only (Enhancement - P4)

Reviewers

Andrew Dinn (@adinn - Reviewer)
Fei Gao (@fg1417 - Committer)

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$ git fetch https://git.openjdk.org/jdk.git pull/20724/head:pull/20724
$ git checkout pull/20724

Update a local copy of the PR:
$ git checkout pull/20724
$ git pull https://git.openjdk.org/jdk.git pull/20724/head

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$ git pr checkout 20724

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$ git pr show -t 20724

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https://git.openjdk.org/jdk/pull/20724.diff

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…ports 128 bits VL only

bridgekeeper · 2024-08-27T09:29:25Z

👋 Welcome back jzhu! 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 · 2024-08-27T09:30:54Z

@JoshuaZhuwj 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:

8339063: [aarch64] Skip verify_sve_vector_length after native calls if SVE supports 128 bits VL only

Reviewed-by: adinn, fgao

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 66 new commits pushed to the master branch:

b1163bc: 8256211: assert fired in java/net/httpclient/DependentPromiseActionsTest (infrequent)
03ba37e: 8339169: Remove NaiveHuffman coder
a136a85: 8338768: Introduce runtime lookup to check for static builds
9d7d85a: 8339298: Remove unused function declaration poll_for_safepoint
92aafb4: 8338934: vmTestbase/nsk/jvmti/FieldWatch/TestDescription.java tests timeout intermittently
392bdd5: 8339248: RISC-V: Remove li64 macro assembler routine and related code
4f071ce: 8311163: Parallel: Improve large object handling during evacuation
b840b13: 8338882: Clarify matching order of MessageFormat subformat factory styles
25e03b5: 8339115: Rename TypeKind enum constants to follow code style
fef1ef7: 6426678: (spec) File.createTempFile(prefix, suffix, dir) needs clarification for illegal symbols in suffix
... and 56 more: https://git.openjdk.org/jdk/compare/b704bfa205bbd8c56f128ce5d727d40c8a3ec613...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.

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openjdk · 2024-08-27T09:31:17Z

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

hotspot

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 · 2024-08-27T09:35:31Z

Webrevs

JoshuaZhuwj · 2024-08-27T12:05:21Z

Add some more background.

The maximum SVE vector length "VLmax" is determined by the hardware: 16 <= VLmax <= 256.
The value of VL can be configured at runtime: 16 <= VL <= VLmax, where VL must be a multiple of 16.

Once we find cpu's VLMax is 16 bytes only, the verification "verify_sve_vector_length()" after native calls is not required - in other words, VL cannot be configured to a value other than 16.

JoshuaZhuwj · 2024-08-28T08:53:40Z

/label add hotspot-compiler

openjdk · 2024-08-28T08:53:58Z

@JoshuaZhuwj
The hotspot-compiler label was successfully added.

adinn

The code changes look ok. What have you done to test it?

JoshuaZhuwj · 2024-08-28T14:14:56Z

The code changes look ok. What have you done to test it?

@adinn Thanks for your review!

The maximum SVE vector length "VLmax" is determined by the hardware: 16 <= VLmax <= 256. The value of VL can be configured at runtime: 16 <= VL <= VLmax, where VL must be a multiple of 16.

Once we find cpu's VLMax is 16 bytes only, the verification "verify_sve_vector_length()" after native calls is not required - in other words, VL cannot be configured to a value other than 16.

I checked the behavior of prctl(PR_SVE_SET_VL, value) by a separated C case.
https://github.com/JoshuaZhuwj/openjdk_cases/blob/master/8339063/setSVEVL.c
The output is aligned with the above expectation.
https://github.com/JoshuaZhuwj/openjdk_cases/blob/master/8339063/output

I have an aarch64 hardware at hand with only 128-bit SVE vector length.
With this change applied, the generated native wrapper and native entry no longer check SVE VL change after native calls in the machine.

I also ensure no regression failures by jtreg case:
test/hotspot/jtreg/compiler/c2/aarch64/TestSVEWithJNI.java
Also no regression failures when JVM starts up by specifying different MaxVectorSize.

adinn · 2024-08-28T15:52:16Z

Ok, that sounds like it is sufficient.

fg1417 · 2024-08-29T09:50:33Z

src/hotspot/cpu/aarch64/aarch64_vector.ad

@@ -155,7 +155,7 @@ source %{
    }

    int length_in_bytes = vlen * type2aelembytes(bt);
-    if (UseSVE == 0 && length_in_bytes > 16) {
+    if (UseSVE == 0 && length_in_bytes > FloatRegister::neon_vl) {


Should we also update aarch64_vector_ad.m4 to avoid any mismatch :) ?

Nice catch! I overlooked this place. Thanks for your reminder!

fg1417

LGTM! Thanks for the update.

adinn

still good

JoshuaZhuwj · 2024-09-02T15:13:58Z

Thank you for the reviews! @adinn @fg1417

JoshuaZhuwj · 2024-09-02T15:14:59Z

/integrate

openjdk · 2024-09-02T15:15:23Z

@JoshuaZhuwj
Your change (at version d191085) is now ready to be sponsored by a Committer.

adinn · 2024-09-02T15:36:45Z

/sponsor

openjdk · 2024-09-02T15:37:59Z

Going to push as commit 0e6bb51.
Since your change was applied there have been 66 commits pushed to the master branch:

b1163bc: 8256211: assert fired in java/net/httpclient/DependentPromiseActionsTest (infrequent)
03ba37e: 8339169: Remove NaiveHuffman coder
a136a85: 8338768: Introduce runtime lookup to check for static builds
9d7d85a: 8339298: Remove unused function declaration poll_for_safepoint
92aafb4: 8338934: vmTestbase/nsk/jvmti/FieldWatch/TestDescription.java tests timeout intermittently
392bdd5: 8339248: RISC-V: Remove li64 macro assembler routine and related code
4f071ce: 8311163: Parallel: Improve large object handling during evacuation
b840b13: 8338882: Clarify matching order of MessageFormat subformat factory styles
25e03b5: 8339115: Rename TypeKind enum constants to follow code style
fef1ef7: 6426678: (spec) File.createTempFile(prefix, suffix, dir) needs clarification for illegal symbols in suffix
... and 56 more: https://git.openjdk.org/jdk/compare/b704bfa205bbd8c56f128ce5d727d40c8a3ec613...master

Your commit was automatically rebased without conflicts.

openjdk · 2024-09-02T15:38:09Z

@adinn @JoshuaZhuwj Pushed as commit 0e6bb51.

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

[aarch64] Skip verify_sve_vector_length after native calls if SVE sup…

b825cba

…ports 128 bits VL only

openjdk bot added the hotspot hotspot-dev@openjdk.org label Aug 27, 2024

JoshuaZhuwj changed the title ~~[aarch64] Skip verify_sve_vector_length after native calls if SVE supports 128 bits VL only~~ 8339063: [aarch64] Skip verify_sve_vector_length after native calls if SVE supports 128 bits VL only Aug 27, 2024

openjdk bot added the rfr Pull request is ready for review label Aug 27, 2024

Fix compilation failure with --disable-precompiled-headers

c0ec549

openjdk bot added the hotspot-compiler hotspot-compiler-dev@openjdk.org label Aug 28, 2024

adinn reviewed Aug 28, 2024

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adinn approved these changes Aug 28, 2024

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openjdk bot added the ready Pull request is ready to be integrated label Aug 28, 2024

fg1417 reviewed Aug 29, 2024

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Fix mismatch issue in ad m4 file

d191085

openjdk bot removed the ready Pull request is ready to be integrated label Aug 30, 2024

fg1417 approved these changes Sep 2, 2024

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adinn approved these changes Sep 2, 2024

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openjdk bot added the ready Pull request is ready to be integrated label Sep 2, 2024

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openjdk bot closed this Sep 2, 2024

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 Sep 2, 2024

JoshuaZhuwj deleted the 8339063 branch September 3, 2024 07:55

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8339063: [aarch64] Skip verify_sve_vector_length after native calls if SVE supports 128 bits VL only #20724

8339063: [aarch64] Skip verify_sve_vector_length after native calls if SVE supports 128 bits VL only #20724

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8339063: [aarch64] Skip verify_sve_vector_length after native calls if SVE supports 128 bits VL only #20724

8339063: [aarch64] Skip verify_sve_vector_length after native calls if SVE supports 128 bits VL only #20724

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