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

---

Progress

• Change must not contain extraneous whitespace
• 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

Using git

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:
$ git checkout pull/129
$ git pull https://git.openjdk.java.net/jdk16u pull/129/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 129

View PR using the GUI difftool:
$ git pr show -t 129

Using diff file

Download this PR as a diff file:
https://git.openjdk.java.net/jdk16u/pull/129.diff

[bridgekeeper]

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[openjdk]

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

[openjdk]

@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]

Webrevs

• 00: Full (4bdbe845)