RFR: 8139457: Array bases are aligned at HeapWord granularity [v11]

[Roman Kennke]

On Thu, 19 Jan 2023 10:21:10 GMT, Stefan Karlsson <stefank at openjdk.org> wrote:

>> Roman Kennke has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 25 commits:
>> 
>>  - Merge branch 'master' into JDK-8139457
>>  - Fix gtest for correct base offsets in 32bit builds
>>  - Fix cast warning
>>  - Revert relaxation of array length
>>  - Add guards to ArrayBaseOffsets test to allow running with -UseCompressedClassPointers
>>  - Fix another cast warning
>>  - Clean cast warning from size_t to int
>>  - Clear leading 32bits in Z array allocator
>>  - SA adjustments
>>  - Test for 32bit build
>>  - ... and 15 more: https://git.openjdk.org/jdk/compare/500b45e1...c278a53b
>
> src/hotspot/cpu/x86/macroAssembler_x86.cpp line 4136:
> 
>> 4134:   assert(is_aligned(offset_in_bytes, BytesPerInt), "offset must be a multiple of BytesPerInt");
>> 4135: 
>> 4136:   // note: for the remaining code to work, index must be a multiple of BytesPerInt
> 
> Maybe move the comment to above the assert that checks the invariant described by the comment?

I think it is. The whole block below the comment is the runtime check for the described invariant. I re-worded it to be a bit clearer:
// For the remaining code to work, length must be a multiple of BytesPerInt.
// Check that here.

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