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8188046: java.lang.Math.mutliplyHigh does not run in constant time #4660

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@bplb bplb commented Jul 1, 2021

Please consider this proposal to remove the fast path in java.lang.Math.multiplyHigh() the small performance improvement of which is eclipsed by the branch penalty.


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  • Commit message must refer to an issue
  • Change must be properly reviewed

Issue

  • JDK-8188046: java.lang.Math.mutliplyHigh does not run in constant time

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Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.java.net/jdk pull/4660/head:pull/4660
$ git checkout pull/4660

Update a local copy of the PR:
$ git checkout pull/4660
$ git pull https://git.openjdk.java.net/jdk pull/4660/head

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Checkout this PR locally:
$ git pr checkout 4660

View PR using the GUI difftool:
$ git pr show -t 4660

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Download this PR as a diff file:
https://git.openjdk.java.net/jdk/pull/4660.diff

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@bridgekeeper bridgekeeper bot commented Jul 1, 2021

👋 Welcome back bpb! 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 openjdk bot added the rfr label Jul 1, 2021
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@bplb bplb commented Jul 1, 2021

Please refer to the issue for a benchmark and sample output from it.

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@openjdk openjdk bot commented Jul 1, 2021

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

  • core-libs

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 core-libs label Jul 1, 2021
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@mlbridge mlbridge bot commented Jul 1, 2021

Webrevs

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@openjdk openjdk bot commented Jul 2, 2021

@bplb 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:

8188046: java.lang.Math.mutliplyHigh does not run in constant time

Reviewed-by: rriggs, darcy

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 173 new commits pushed to the master branch:

  • 53ad903: 8269135: TestDifferentProtectionDomains runs into timeout in client VM
  • f8bcbf0: 8269596: Snapshot soft ref policy before marking/copying
  • 4107dcf: 8269466: Factor out the common code for initializing and starting internal VM JavaThreads
  • 2baf498: 8269743: test/hotspot/jtreg/vmTestbase/vm/mlvm/meth/stress/jni/nativeAndMH/Test.java crash with small heap (-Xmx50m)
  • 589f084: 8269110: ZGC: Remove dead code in zBarrier
  • b0e1867: Merge
  • a4d2a9a: 8269745: [JVMCI] restore original qualified exports to Graal
  • e377397: 8268566: java/foreign/TestResourceScope.java timed out
  • 6c76e77: 8260684: vmTestbase/gc/gctests/PhantomReference/phantom002/TestDescription.java timed out
  • 4bbf11d: 8269580: assert(is_valid()) failed: invalid register (-1)
  • ... and 163 more: https://git.openjdk.java.net/jdk/compare/cd20c01942dd8559a31e51ef2a595c6eba44b8ad...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.

@openjdk openjdk bot added the ready label Jul 2, 2021
jddarcy
jddarcy approved these changes Jul 2, 2021
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@bplb bplb commented Jul 2, 2021

/integrate

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@openjdk openjdk bot commented Jul 2, 2021

Going to push as commit cb79589.
Since your change was applied there have been 175 commits pushed to the master branch:

  • ca4bea4: 8188044: We need Math.unsignedMultiplyHigh
  • 3d84398: 8268364: jmethod clearing should be done during unloading
  • 53ad903: 8269135: TestDifferentProtectionDomains runs into timeout in client VM
  • f8bcbf0: 8269596: Snapshot soft ref policy before marking/copying
  • 4107dcf: 8269466: Factor out the common code for initializing and starting internal VM JavaThreads
  • 2baf498: 8269743: test/hotspot/jtreg/vmTestbase/vm/mlvm/meth/stress/jni/nativeAndMH/Test.java crash with small heap (-Xmx50m)
  • 589f084: 8269110: ZGC: Remove dead code in zBarrier
  • b0e1867: Merge
  • a4d2a9a: 8269745: [JVMCI] restore original qualified exports to Graal
  • e377397: 8268566: java/foreign/TestResourceScope.java timed out
  • ... and 165 more: https://git.openjdk.java.net/jdk/compare/cd20c01942dd8559a31e51ef2a595c6eba44b8ad...master

Your commit was automatically rebased without conflicts.

@openjdk openjdk bot closed this Jul 2, 2021
@openjdk openjdk bot added integrated and removed ready rfr labels Jul 2, 2021
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@openjdk openjdk bot commented Jul 2, 2021

@bplb Pushed as commit cb79589.

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

@bplb bplb deleted the Math-multiplyHigh-8188046 branch Jul 2, 2021
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