8267652: c2 loop unrolling by 8 results in reading memory past array

[VladimirKempik]

This fixes a p2 issue in jdk16. the issue is intermitent. Happens when array object located at the very end of a mapped heap region Backport applies cleanly

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Progress

• [x] Change must not contain extraneous whitespace
• [x] Commit message must refer to an issue
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Issue

• JDK-8267652: c2 loop unrolling by 8 results in reading memory past array

Reviewing

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Checkout this PR locally:
$ git fetch https://git.openjdk.java.net/jdk16u pull/129/head:pull/129
$ git checkout pull/129

Update a local copy of the PR:
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$ git pr checkout 129

View PR using the GUI difftool:
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https://git.openjdk.java.net/jdk16u/pull/129.diff

[bridgekeeper[bot]]

:wave: Welcome back vkempik! 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[bot]]

This backport pull request has now been updated with issue from the original commit.

[openjdk[bot]]

@VladimirKempik 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:

8267652: c2 loop unrolling by 8 results in reading memory past array

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[mlbridge[bot]]

Webrevs

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