This code makes an intrinsic stub for `Unsafe::setMemory`. See [this PR](https://github.com/openjdk/jdk/pull/16760) for discussion around this change.
Overall, making this an intrinsic improves overall performance of `Unsafe::setMemory` by up to 4x for all buffer sizes. Tested with tier-1 (and full CI). I've added a table of the before and after numbers for the JMH I ran (`MemorySegmentZeroUnsafe`). [setMemoryBM.txt](https://github.com/openjdk/jdk/files/14808974/setMemoryBM.txt) ------------- Commit messages: - Clean up code for PR - Fixed bug - incorrect interface to *_fill_entry - Address review comment - Restore intrinsic - Add benchmark - Test removing intrinsic - Removed setMemory1; debugged intrinsic code - Added actual intrinsic - Add Unsafe.setMemory as intrinsic Changes: https://git.openjdk.org/jdk/pull/18555/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18555&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8329331 Stats: 362 lines in 21 files changed: 311 ins; 49 del; 2 mod Patch: https://git.openjdk.org/jdk/pull/18555.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/18555/head:pull/18555 PR: https://git.openjdk.org/jdk/pull/18555
