8386889: [lworld] Redundant StoreStore membar after FlatValuePayload::read

[jsikstro]

Hello,

This is (yet another) cleanup to remove redundant memory barriers after the new ValuePayload abstraction API in the runtime. The ValuePayload API's (including FlatValuePayload::read) does the necessary calls to order stores of the copy before the oop is published (OrderAccess::storestore), making the platform-specific memory barriers redundant.

I don't have hardware access to RISCV or PPC, but looking at the runtime implementations of OrderAccess::storestore, they achieve the same thing as the platform-specific memory barriers that I suggest we remove in this PR. GHA will show that this compiles at least. Edit: looks like linux-cross-compile is not enabled for the lworld branch yet.

membar(Assembler::StoreStore | Assembler::LoadLoad); and OrderAccess::storestore() both boil down to lwsync on PPC.

The C1 call to load_flat_array already omits the memory barrier, so we don't need to remove it here.

Testing:

• Oracle's tier1-3 linux-aarch64
• GHA

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Issue

• JDK-8386889: [lworld] Redundant StoreStore membar after FlatValuePayload::read (Bug - P4)

Reviewers

• Martin Doerr (@TheRealMDoerr - no project role)
• Axel Boldt-Christmas (@xmas92 - Committer)
• Frederic Parain (@fparain - Committer)

Reviewing

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[openjdk]

@jsikstro This change now passes all automated pre-integration checks.

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After integration, the commit message for the final commit will be:

8386889: [lworld] Redundant StoreStore membar after FlatValuePayload::read

Reviewed-by: mdoerr, aboldtch, fparain

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At the time when this comment was updated there had been 1 new commit pushed to the lworld branch:

• 59019cf: 8387192: [lworld] Review comment drop for core libs

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• 01: Full - Incremental (0186aa78)
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[TheRealMDoerr]

This makes sense. Thanks for taking care of all platforms! I prefer a small change for PPC64.

[TheRealMDoerr]

Thank you! I appreciate it! LGTM.

[xmas92]

lgtm. Thanks for fixing.

[fparain]

LGTM

[jsikstro]

Thank you for the reviews @TheRealMDoerr, @xmas92, and @fparain!
/integrate

[openjdk]

Going to push as commit b508893.
Since your change was applied there have been 69 commits pushed to the lworld branch:

• f0a7ef2: Merge
• 193de1b: 8387185: Locale does not respect numeric singletons
• e8aaa9e: 8387214: TraceJavaAssertions is unused
• ... and 66 more: https://git.openjdk.org/valhalla/compare/42fc9c97c4d0937de785f23546afe178a1799f15...lworld

Your commit was automatically rebased without conflicts.

[openjdk]

@jsikstro Pushed as commit b508893.

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