8305690: [X86] Do not emit two REX prefixes in Assembler::prefix

[lgxbslgx]

Hi all,

This patch prevents Assembler::prefix from emitting two REX prefixes.

Low risk:
It is a corner case which is not triggered by the current code.
In order to avoid bugs in the future, it is good to backport it.

Thanks for taking the time to review.

Best Regards,
-- Guoxiong

---

Progress

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Issue

• JDK-8305690: [X86] Do not emit two REX prefixes in Assembler::prefix

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[bridgekeeper]

👋 Welcome back gli! 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]

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

[openjdk]

@lgxbslgx 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:

8305690: [X86] Do not emit two REX prefixes in Assembler::prefix

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[mlbridge]

Webrevs

• 00: Full (d9fa7390)

[lgxbslgx]

The fix request was approved. Could I get your help to sponsor this patch?

/integrate

[openjdk]

@lgxbslgx
Your change (at version d9fa739) is now ready to be sponsored by a Committer.

[DamonFool]

/sponsor

[openjdk]

Going to push as commit 6a84974.

[openjdk]

@DamonFool @lgxbslgx Pushed as commit 6a84974.

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

[lgxbslgx]

@DamonFool Thanks for the sponsor!