RFR: 8367780: Enable UseAPX on Intel CPUs only when both APX_F and APX_NCI_NDD_NF cpuid features are present [v3]

[Srinivas Vamsi Parasa]

On Wed, 17 Sep 2025 00:26:32 GMT, Sandhya Viswanathan <sviswanathan at openjdk.org> wrote:

>> Srinivas Vamsi Parasa has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   update KNL check
>
> src/hotspot/cpu/x86/vm_version_x86.cpp line 1083:
> 
>> 1081:   if (!UseAPX) {
>> 1082:     _features.clear_feature(CPU_APX_F);
>> 1083:     _features.clear_feature(CPU_APX_NCI_NDD_NF);
> 
> We don't need separate CPU_APX_NCI_NDD_NF feature and the related changes as CPU_APX_F feature is set only when both bits (sefsl1_cpuid7_edx.bits.apx_f and std_cpuid29_ebx.bits.apx_nci_ndd_nf) are set.

Please see the updated changes which removes CPU_APX_NCI_NDD_NF as an explicit feature.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/27320#discussion_r2356297066