RFR: 8139457: Array bases are aligned at HeapWord granularity [v7]
Roman Kennke
rkennke at openjdk.org
Thu Dec 15 19:05:34 UTC 2022
> See [JDK-8139457](https://bugs.openjdk.org/browse/JDK-8139457) for details.
>
> Basically, when running with -XX:-UseCompressedClassPointers, arrays will have a gap between the length field and the first array element, because array elements will only start at word-aligned offsets. This is not necessary for smaller-than-word elements.
>
> Also, while it is not very important now, it will become very important with Lilliput, which eliminates the Klass field and would always put the length field at offset 8, and leave a gap between offset 12 and 16.
>
> Testing:
> - [x] runtime/FieldLayout/ArrayBaseOffsets.java (x86_64, x86_32, aarch64, arm, riscv, s390)
> - [x] bootcycle (x86_64, x86_32, aarch64, arm, riscv, s390)
> - [x] tier1 (x86_64, x86_32, aarch64, riscv)
> - [x] tier2 (x86_64, aarch64, riscv)
> - [x] tier3 (x86_64, riscv)
Roman Kennke has updated the pull request incrementally with one additional commit since the last revision:
Fix another cast warning
-------------
Changes:
- all: https://git.openjdk.org/jdk/pull/11044/files
- new: https://git.openjdk.org/jdk/pull/11044/files/77e2ace4..4ec977cf
Webrevs:
- full: https://webrevs.openjdk.org/?repo=jdk&pr=11044&range=06
- incr: https://webrevs.openjdk.org/?repo=jdk&pr=11044&range=05-06
Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
Patch: https://git.openjdk.org/jdk/pull/11044.diff
Fetch: git fetch https://git.openjdk.org/jdk pull/11044/head:pull/11044
PR: https://git.openjdk.org/jdk/pull/11044
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