RFR: 8319408: RISC-V: MaxVectorSize is not consistently checked in several situations [v2]

[Hamlin Li]

On Tue, 7 Nov 2023 09:03:44 GMT, Hamlin Li <mli at openjdk.org> wrote:

>> Hi,
>> Can you review the change to fix the MaxVectorSize checking in vm_version_riscv.cpp?
>> Thanks!
>> 
>> Current logic will not check whether (MaxVectorSize < 16), after the assignment `MaxVectorSize = _initial_vector_length;`, in following situation.
>> a) if FLAG_IS_DEFAULT(MaxVectorSize) == true
>> b) if FLAG_IS_DEFAULT(MaxVectorSize) == false and (MaxVectorSize >= 16) and is_power_of_2(MaxVectorSize) and (MaxVectorSize > _initial_vector_length)
>> 
>> And in original code, the logic is not consistent for the situations between MaxVectorSize < 16 and MaxVectorSize >= 16, when is_power_of_2(MaxVectorSize) == false; for the former (<16) it's to disable RVV, for the latter (>=16) it's vm_exit.
>
> Hamlin Li has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Refine log

Thanks @luhenry @RealFYang for your reviewing.

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PR Comment: https://git.openjdk.org/jdk/pull/16498#issuecomment-1798155894