Simplify the layout access var handles to be direct in some common cases. Also made `VarHandle::isAccessModeSupported` report if an access mode is supported for a VH.
Reduces the instructions to execute this code in a simple main by 47%: long[] arr = new long[8]; var ms = MemorySegment.ofArray(arr); ms.setAtIndex(ValueLayout.JAVA_BYTE, 12, (byte) 3); Main overheads in FFM are identified to be: 1. Eager initialization of direct MethodHandle; can be CDS archived 2. MH combinator forms via LambdaFormEditor, not cached right now and always have large overhead Still need other measures to deal with common user patterns of `MethodHandles.insertCoordinates(vh, 1, 0L)` which currently is still very slow. Tests: tier 1-3 running ------------- Commit messages: - More cleanup - Merge branch 'master' of https://github.com/openjdk/jdk into feature/ffm-vh-inline - Make sure the form impl class is initialized - Reduce MT initialization work - MH linkToStatic stall - Merge branch 'master' of https://github.com/openjdk/jdk into feature/ffm-vh-inline - Merge branch 'master' of https://github.com/openjdk/jdk into feature/ffm-vh-inline - Enhance cache for basic value layouts - More stuff - VH inline stuff stage Changes: https://git.openjdk.org/jdk/pull/23720/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23720&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8350118 Stats: 1869 lines in 16 files changed: 1056 ins; 215 del; 598 mod Patch: https://git.openjdk.org/jdk/pull/23720.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/23720/head:pull/23720 PR: https://git.openjdk.org/jdk/pull/23720
