8384636: Parallel: Remove redundant PSAdjustTask claim counter initialization loop

[albertnetymk]

PSAdjustTask currently initializes _claim_counters with a placement-new loop in the constructor body. The array elements are already constructed before the constructor body runs, and this is sufficient because the default constructor of Atomic<uint> initializes the value to zero.

This trivial patch removes the redundant loop and adds an explicit _claim_counters{} member initializer.

The generated release assembly is not byte-identical: the new form uses a vector zero store for the counter array instead of separate scalar stores. The effective initialization is the same.

Test: tier1

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Issue

• JDK-8384636: Parallel: Remove redundant PSAdjustTask claim counter initialization loop (Enhancement - P4)

Reviewers

• Stefan Karlsson (@stefank - Reviewer)

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