RFR: 8293547: Add relaxed add_and_fetch for macos aarch64 atomics

Fri May 5 06:05:16 UTC 2023

Atomic::add_and_fetch currently doesn't honor the relaxed memory order hint. I suggest that we change the code to do so. We initially found this issue when looking into why one of our parallel iterators were slower than expected. We have been using this for a while in the Generational ZGC repository.

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Commit messages:
 - 8293547: Add relaxed add_and_fetch for macos aarch64 atomics

Changes: https://git.openjdk.org/jdk/pull/13823/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13823&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8293547
  Stats: 7 lines in 1 file changed: 4 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/13823.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13823/head:pull/13823

PR: https://git.openjdk.org/jdk/pull/13823