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8305324: C2: Wrong execution of vectorizing Interger.reverseBytes #13404

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8305324: C2: Wrong execution of vectorizing Interger.reverseBytes #13404

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quadhier
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@quadhier quadhier commented Apr 10, 2023

This patch should fix JDK-8305324.

SuperWord::compute_vector_element_type() propagates backward a narrower integer type when the upper bits of the value are not needed. However, Integer.reverseBytes() depends on higher order bits of an integer and should be prevented from being vectorized like Math.abs()( which is Op_AbsI in the following code).

if (same_type) {
// In any Java arithmetic operation, operands of small integer types
// (boolean, byte, char & short) should be promoted to int first. As
// vector elements of small types don't have upper bits of int, for
// RShiftI or AbsI operations, the compiler has to know the precise
// signedness info of the 1st operand. These operations shouldn't be
// vectorized if the signedness info is imprecise.
const Type* vt = vtn;
int op = in->Opcode();
if (VectorNode::is_shift_opcode(op) || op == Op_AbsI) {
Node* load = in->in(1);

I have tested this patch for tier 1-3 on x86-64.


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Issue

  • JDK-8305324: C2: Wrong execution of vectorizing Interger.reverseBytes

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Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/13404/head:pull/13404
$ git checkout pull/13404

Update a local copy of the PR:
$ git checkout pull/13404
$ git pull https://git.openjdk.org/jdk.git pull/13404/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 13404

View PR using the GUI difftool:
$ git pr show -t 13404

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/13404.diff

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bridgekeeper bot commented Apr 10, 2023

👋 Welcome back quadhier! 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 Apr 10, 2023

⚠️ @quadhier a branch with the same name as the source branch for this pull request (master) is present in the target repository. If you eventually integrate this pull request then the branch master in your personal fork will diverge once you sync your personal fork with the upstream repository.

To avoid this situation, create a new branch for your changes and reset the master branch. You can do this by running the following commands in a local repository for your personal fork. Note: you do not have to name the new branch NEW-BRANCH-NAME.

$ git checkout -b NEW-BRANCH-NAME
$ git branch -f master db174a15d18eb8ea9c826592b88f8e690112eaaf
$ git push -f origin master

Then proceed to create a new pull request with NEW-BRANCH-NAME as the source branch and close this one.

@openjdk openjdk bot added the rfr Pull request is ready for review label Apr 10, 2023
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openjdk bot commented Apr 10, 2023

@quadhier 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.

@openjdk openjdk bot added the hotspot-compiler hotspot-compiler-dev@openjdk.org label Apr 10, 2023
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mlbridge bot commented Apr 10, 2023

Webrevs

@quadhier
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Sorry, I forgot to enable the pre-submit test. I will close this PR and create a new one.

@quadhier quadhier closed this Apr 10, 2023
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Please refer to the new PR #13406. Thanks.

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