This simple changeset enables the diagnostic flag `PrintFlatArrayLayout` in
product builds, similarly to other diagnostic flags such as `PrintFieldLayout`.
This was useful to quickly grasp what arrays are flattened when analyzing a
benchmark.
before:
$ java --enable-preview -XX:+UnlockDiagnosticVMOptions
-XX:+PrintFlatArrayLayout --version
openjdk 27-jep401ea2 2026-09-15
OpenJDK Runtime Environment (build 27-jep401ea2-rocastan.open)
OpenJDK 64-Bit Server VM (build 27-jep401ea2-rocastan.open, mixed mode)
after:
$ java --enable-preview -XX:+UnlockDiagnosticVMOptions
-XX:+PrintFlatArrayLayout --version
Flat Type Array: [Ljava.lang.Character; {0x0000000095040348}
- element klass: 'java/lang/Character'
- layout kind: NULLABLE_ATOMIC_FLAT
- array properties: DEFAULT (NULLABLE ATOMIC)
- element size 4 aligned layout size 4
Flat Type Array: [Ljava.lang.Integer; {0x000000009505d0a0}
- element klass: 'java/lang/Integer'
- layout kind: NULLABLE_ATOMIC_FLAT
- array properties: DEFAULT (NULLABLE ATOMIC)
- element size 8 aligned layout size 8
openjdk 27-jep401ea2 2026-09-15
OpenJDK Runtime Environment (build 27-jep401ea2-rocastan.open)
OpenJDK 64-Bit Server VM (build 27-jep401ea2-rocastan.open, mixed mode)
**Testing**: tier1-3, manually checked that flattened array info is shown on a
couple of scenarios.
-------------
Commit messages:
- Honor PrintFlatArrayLayout in product builds
Changes: https://git.openjdk.org/valhalla/pull/2090/files
Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=2090&range=00
Issue: https://bugs.openjdk.org/browse/JDK-8377799
Stats: 4 lines in 1 file changed: 0 ins; 4 del; 0 mod
Patch: https://git.openjdk.org/valhalla/pull/2090.diff
Fetch: git fetch https://git.openjdk.org/valhalla.git pull/2090/head:pull/2090
PR: https://git.openjdk.org/valhalla/pull/2090
