8295124: Atomic::add to pointer type may return wrong value

[kimbarrett]

Please review this change to the handling of Atomic pointer arithmetic. When
the value being modified is a pointer P*, the type of the value in the
destination passed to the platform operation is const char*, so a pointer
type whose pointee is size 1. This allows the platform operation to just treat
the arithmetic as a simple byte adjustment.

To demonstrate the problem described in the bug (possible incorrect result for
Atomic pointer arithmetic) and show that it is now fixed, this change also
includes some gtests for Atomic operations, including pointer arithmetic which
fails before the change and succeeds after.

Testing: mach5 tier1-3

---

Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Commit message must refer to an issue

Issue

• JDK-8295124: Atomic::add to pointer type may return wrong value

Reviewers

• Thomas Schatzl (@tschatzl - Reviewer) ⚠️ Review applies to e44e81cd
• Coleen Phillimore (@coleenp - Reviewer) ⚠️ Review applies to e44e81cd

Reviewing

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[bridgekeeper]

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[openjdk]

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[mlbridge]

Webrevs

• 02: Full - Incremental (87d98eee)
• 01: Full - Incremental (e44e81cd)
• 00: Full (9dbb07a6)

[kimbarrett]

Poke - any takers.

[tschatzl]

Lgtm.

[openjdk]

@kimbarrett 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:

8295124: Atomic::add to pointer type may return wrong value

Reviewed-by: tschatzl, coleenp

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[coleenp]

I get it! Looks good.

[kimbarrett]

Thanks @tschatzl and @coleenp for reviews.

[kimbarrett]

/integrate

[openjdk]

Going to push as commit 1164258.

[openjdk]

@kimbarrett Pushed as commit 1164258.

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