RFR: 8139457: Array bases are aligned at HeapWord granularity [v38]

[Aleksey Shipilev]

On Tue, 4 Jul 2023 07:00:31 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

>> src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/oops/Array.java line 68:
>> 
>>> 66:         return !VM.getVM().isCompressedOopsEnabled();
>>> 67:       }
>>> 68:     }
>> 
>> I think `isCompressedOopsEnabled` already does the right thing, so:
>> 
>> Suggestion:
>> 
>>     if (type == BasicType.T_OBJECT || type == BasicType.T_ARRAY) {
>>       return !VM.getVM().isCompressedOopsEnabled();
>>     }
>
> On 32-bit, isCompressedOopsEnabled() would be false, so the method returns true, which means we would 8-byte align reference array elements? That doesn't seem right.

Right, nevermind. I keep tripping over this. `isLP64` is actually symmetric to `#ifdef _LP64`.

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PR Review Comment: https://git.openjdk.org/jdk/pull/11044#discussion_r1252979322