Integrated: 8139457: Relax alignment of array elements

[Roman Kennke]

On Tue, 8 Nov 2022 20:18:09 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

> 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)

This pull request has now been integrated.

Changeset: 336bbbe3
Author:    Roman Kennke <rkennke at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/336bbbe3895214a772e0f3aafb36277c46645ded
Stats:     645 lines in 33 files changed: 474 ins; 85 del; 86 mod

8139457: Relax alignment of array elements

Co-authored-by: Fei Yang <fyang at openjdk.org>
Co-authored-by: Thomas Stuefe <stuefe at openjdk.org>
Reviewed-by: stuefe, stefank, shade, coleenp, kdnilsen, aboldtch

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PR: https://git.openjdk.org/jdk/pull/11044