[master] RFR: Load narrowKlass from header, AArch64 assembler implementation [v2]

[Roman Kennke]

On Thu, 27 Jan 2022 14:25:40 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> Roman Kennke has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Add asserts
>
> src/hotspot/cpu/aarch64/macroAssembler_aarch64.cpp line 3718:
> 
>> 3716:   eor(tmp, tmp, markWord::unlocked_value);
>> 3717:   tst(tmp, markWord::lock_mask_in_place);
>> 3718:   br(Assembler::NE, slow);
> 
> Suggestion:
> 
>   tbnz(tmp, exact_log2(markWord::lock_mask_in_place), slow);

Would that work, though? I need to test if the lowest *two* bits are zero (or, together with the preceding eor, test if the lowest two bits are exactly 01). TBNZ only tests a single bit, afaik.

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PR: https://git.openjdk.java.net/lilliput/pull/36