RFR: Fix allocate aligned [v2]

[Kelvin Nilsen]

On Thu, 5 Jan 2023 01:20:59 GMT, William Kemper <wkemper at openjdk.org> wrote:

>> Kelvin Nilsen has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Refinements during code review
>
> src/hotspot/share/gc/shenandoah/shenandoahFreeSet.cpp line 319:
> 
>> 317:       assert(req.actual_size() % CardTable::card_size_in_words() == 0, "PLAB start must align with card boundary");
>> 318:       assert(((uintptr_t) result) % CardTable::card_size_in_words() == 0, "PLAB start must align with card boundary");
>> 319:       if (result != nullptr && free > usable_free) {
> 
> Line 315 asserts that `result` cannot be `nullptr`, do we need to check for non-null again here?

Thanks for this catch.  Making this change and testing on pipeline before integration.

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PR: https://git.openjdk.org/shenandoah/pull/192