RFR: 8367780: Enable UseAPX on Intel CPUs only when both APX_F and APX_NCI_NDD_NF cpuid features are present [v4]

[Jatin Bhateja]

On Fri, 19 Sep 2025 16:24:44 GMT, Srinivas Vamsi Parasa <sparasa at openjdk.org> wrote:

>> Thanks for answering my questions.. things we checked:
>> - double-checked reg parameter values of cpuid against the spec
>> - double-checked endianness of bitset variables in C grammar
>> - double-checked how offset to the field std_cpuid29_ebx is computed
>> 
>> Change looks good to me
>
>> Change looks good to me
>> 
> Thanks Vlad for going through the changes and reviewing the PR!

Hi @vamsi-parasa ,

Before this PR, we could validate APX support using the publicly available latest version 9.58 of Intel software development emulator.


EMR>sde64 --version
Intel(R) Software Development Emulator.  Version:  9.58.0 external (0)
Copyright (C) 2008-2025, Intel Corporation. All rights reserved.

EMR>sde64 -dmr -ptr_raise -- java -XX:+PrintFlagsFinal -XX:+UnlockExperimentalVMOptions -XX:+UseAPX --version | grep APX
     bool UseAPX                                   = true                            {ARCH experimental} {command line}


After this PR, UseAPX support is false, I think we should only upstream the support which can be validated. 


EMR>sde64 -dmr -ptr_raise -- java -XX:+PrintFlagsFinal -XX:+UnlockExperimentalVMOptions -XX:+UseAPX --version | grep APX
OpenJDK 64-Bit Server VM warning: UseAPX is not supported on this CPU, setting it to false
     bool UseAPX                                   = false                           {ARCH experimental} {command line}


Best Regards,
Jatin

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PR Comment: https://git.openjdk.org/jdk/pull/27320#issuecomment-3323431153