RFR: 8139457: Array bases are aligned at HeapWord granularity [v14]

[Coleen Phillimore]

On Mon, 23 Jan 2023 16:58:19 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)
>
> Roman Kennke has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Remove unused method

The linux-x64 product build complains about uncalled filler_array_min_size().
a3b95b83d456/workspace/open/src/hotspot/share/gc/shared/collectedHeap.hpp:209:24: error: inline function 'static size_t CollectedHeap::filler_array_min_size()' used but never defined [-Werror]
[2023-01-23T20:38:03,126Z]   209 |   static inline size_t filler_array_min_size();
[2023-01-23T20:38:03,126Z]       |                        ^~~~~~~~~~~~~~~~~~~~~
[2023-01-23T20:38:03,970Z] cc1plus: all warnings being treated as errors

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