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8282231: x86-32: runtime call to SharedRuntime::ldiv corrupts registers #7575

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@theRealAph theRealAph commented Feb 22, 2022

In x86_32.ad, a call to SharedRuntime::ldiv doesn't save all of the call-clobbered registers. Also SharedRuntime::lrem.
effect(CALL) is the simplest way to fix this, and AFAIK the most efficient too.

This is by no means the only bug in this area, but it's trivial to fix and allows a bootcycle build to complete on recent Linuxes.


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  • JDK-8282231: x86-32: runtime call to SharedRuntime::ldiv corrupts registers

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👋 Welcome back aph! 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.

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openjdk bot commented Feb 22, 2022

⚠️ @theRealAph This pull request contains merges that bring in commits not present in the target repository. Since this is not a "merge style" pull request, these changes will be squashed when this pull request in integrated. If this is your intention, then please ignore this message. If you want to preserve the commit structure, you must change the title of this pull request to Merge <project>:<branch> where <project> is the name of another project in the OpenJDK organization (for example Merge jdk:master).

@openjdk openjdk bot added the rfr Pull request is ready for review label Feb 22, 2022
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@theRealAph The following label will be automatically applied to this pull request:

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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.

@openjdk openjdk bot added the hotspot-compiler hotspot-compiler-dev@openjdk.org label Feb 22, 2022
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mlbridge bot commented Feb 22, 2022

Webrevs

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Yeah, I did a similar thing here: #7498 -- I think we can drop cr, cx, bx from match rule arguments too. Also drop spaces between parentheses, while we are at it. That change passed tier{1,2,3} on x86_32, I am sure this one passes it too.

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Yeah, I did a similar thing here: #7498 -- I think we can drop cr, cx, bx from match rule arguments too. Also drop spaces between parentheses, while we are at it. That change passed tier{1,2,3} on x86_32, I am sure this one passes it too.

Yes, we seem to have collided. Suggest we go ahead with this one, OK? I've put you in as a co-author, so I guess someone else will have to review it.

cr, cx, and bx are call-clobbered, so we don't need them as an effect, I believe.

@@ -7827,7 +7827,7 @@ instruct divI_eReg(eAXRegI rax, eDXRegI rdx, eCXRegI div, eFlagsReg cr) %{
// Divide Register Long
instruct divL_eReg( eADXRegL dst, eRegL src1, eRegL src2, eFlagsReg cr, eCXRegI cx, eBXRegI bx ) %{
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I agree with @shipilev that we can remove eFlagsReg cr, eCXRegI cx, eBXRegI bx here, right?

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Done. I deleted them in the effect list but forgot to delete the corresponding args.

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So how did you find this bug?
Is it possible to add a jtreg test for this fix?

Please also update the copyright year.
Thanks.

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theRealAph commented Feb 22, 2022

So how did you find this bug?

Found during testing of a new OS build. Fails bootstrap.

Is it possible to add a jtreg test for this fix?

No, because it corrupts registers in arbitrary places, causing seemingly-random crashes.
If you're lucky it'll corrupt a pointer value, in which case you're almost guaranteed a crash.
If you're unlucky it'll corrupt some data value somewhere. It's a Heisenbug.

Please also update the copyright year. Thanks.

OK.

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Looks good to me.
Thanks for the update.

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openjdk bot commented Feb 22, 2022

@theRealAph 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:

8282231: x86-32: runtime call to SharedRuntime::ldiv corrupts registers

Reviewed-by: shade, jiefu

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 298 new commits pushed to the master branch:

  • e1060be: 8281615: Deadlock caused by jdwp agent
  • 6f882de: 8280964: [Linux aarch64] : drawImage dithers TYPE_BYTE_INDEXED images incorrectly
  • 2557ef8: 8282276: Problem list failing two Robot Screen Capture tests
  • 6445ee4: 5041655: (ch) FileLock: negative param and overflow issues
  • 7feabee: 8261407: ReflectionFactory.checkInitted() is not thread-safe
  • 58e1882: 8282042: [testbug] FileEncodingTest.java depends on default encoding
  • 3cb3867: 8281315: Unicode, (?i) flag and backreference throwing IndexOutOfBounds Exception
  • 957dae0: 8280958: G1/Parallel: Unify marking code structure
  • e44d067: 8244593: Clean up GNM/NM after JEP 381
  • 41355e2: 8276686: Malformed Javadoc inline tags in JDK source in /java/util/regex/Pattern.java
  • ... and 288 more: https://git.openjdk.java.net/jdk/compare/f34f8d4d6a9b3e24a93a322b985c1413c27311cc...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.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

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/integrate

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openjdk bot commented Feb 23, 2022

Going to push as commit ecd85e6.
Since your change was applied there have been 299 commits pushed to the master branch:

  • 378fa50: 8281962: Avoid unnecessary native calls in InflaterInputStream
  • e1060be: 8281615: Deadlock caused by jdwp agent
  • 6f882de: 8280964: [Linux aarch64] : drawImage dithers TYPE_BYTE_INDEXED images incorrectly
  • 2557ef8: 8282276: Problem list failing two Robot Screen Capture tests
  • 6445ee4: 5041655: (ch) FileLock: negative param and overflow issues
  • 7feabee: 8261407: ReflectionFactory.checkInitted() is not thread-safe
  • 58e1882: 8282042: [testbug] FileEncodingTest.java depends on default encoding
  • 3cb3867: 8281315: Unicode, (?i) flag and backreference throwing IndexOutOfBounds Exception
  • 957dae0: 8280958: G1/Parallel: Unify marking code structure
  • e44d067: 8244593: Clean up GNM/NM after JEP 381
  • ... and 289 more: https://git.openjdk.java.net/jdk/compare/f34f8d4d6a9b3e24a93a322b985c1413c27311cc...master

Your commit was automatically rebased without conflicts.

@openjdk openjdk bot added the integrated Pull request has been integrated label Feb 23, 2022
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@openjdk openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels Feb 23, 2022
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@theRealAph Pushed as commit ecd85e6.

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