RFR: 8321371: SpinPause() not implemented for bsd_aarch64/macOS [v2]

[Fredrik Bredberg]

> The SpinPause() function only returns 0 on bsd_aarch64 (i.e. macOS)
> 
> This PR initially meant to implement SpinPause() for macOS on AArch64 by copying the source from linux_aarch64, but after having some internal discussions, it seems like the most reasonable thing to do is to implement SpinPause() using a single inline yield instruction.
> 
> Tested successfully on macosx-aarch64 tier1-tier5.

Fredrik Bredberg has updated the pull request incrementally with one additional commit since the last revision:

  SpinPause() is now configurable on bsd_aarch64/macOS

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/16994/files
  - new: https://git.openjdk.org/jdk/pull/16994/files/159244bd..addf22d0

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16994&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16994&range=00-01

  Stats: 32 lines in 1 file changed: 31 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/16994.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16994/head:pull/16994

PR: https://git.openjdk.org/jdk/pull/16994