[15] RFR (S): 8238696: x86: Enumerate all detected CPU features in VM_Version feature string

[Vladimir Ivanov]

Thanks for taking a look, David.

Updated webrev:
   http://cr.openjdk.java.net/~vlivanov/8238696/webrev.01/

>> http://cr.openjdk.java.net/~vlivanov/8238696/webrev.00/
>> https://bugs.openjdk.java.net/browse/JDK-8238696
>>
>> Abstract_VM_Version::features_string() doesn't contain all the CPU 
>> features detected by the JVM on x86 (for example, for AVX-512 only 
>> AVX-512F is included as "evex").
>>
>> The fix adds missing features to the list [1].
> 
> The function naming that you have changed for supports_avx512_vpclmulqdq 
> was explicitly requested by Vladimir K.:
> 
> http://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2019-December/036326.html 
> 
> 
> If anything I would suggest supports_vpopcntdq() should have the avx512 
> part added.

Makes sense. Also, decided to rename VNNI, VAES, and VBMI2. They are 
listed in the manual as part of AVX512.

> The actual expansion of the feature string seems okay. It does make me 
> wonder why these items have been left out previously.

I believe it was just overlooked. Added a comment near cpu feature 
constant declarations.

Also, introduced a check to ensure the temporary on-stack buffer is 
large enough.

Best regards,
Vladimir Ivanov
> 
> Thanks,
> David
> 
>> Testing: manual (-Xlog:os+cpu=trace output on different hardware),
>>           hs-precheckin-comp, hs-tier1, hs-tier2
>>
>> Best regards,
>> Vladimir Ivanov
>>
>> [1] $ java -Xlog:os+cpu=trace -XX:UseAVX=3 -version
>>
>> ...
>> [0.010s][info][os,cpu] UseSSE=4  UseAVX=3  UseAES=1  MaxVectorSize=64
>> ...
>> [0.011s][info][os,cpu] CPU:total 8 (initial active 8) (4 cores per 
>> cpu, 2 threads per core) family 6 model 85 stepping 4, cmov, cx8, 
>> fxsr, mmx, sse, sse2, sse3, ssse3, sse4.1, sse4.2, popcnt, vzeroupper, 
>> avx, avx2, aes, clmul, erms, rtm, 3dnowpref, lzcnt, ht, tsc, bmi1, 
>> bmi2, adx, avx512f, avx512dq, avx512cd, avx512bw, avx512vl, fma, 
>> clflush, clflushopt, clwb
>> ...
>> [0.011s][info][os,cpu] flags        : fpu vme de pse tsc msr pae mce 
>> cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss 
>> ht syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon rep_good 
>> nopl xtopology cpuid tsc_known_freq pni pclmulqdq vmx ssse3 fma cx16 
>> pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave 
>> avx f16c rdrand hypervisor lahf_lm abm 3dnowprefetch cpuid_fault 
>> invpcid_single pti ssbd ibrs ibpb stibp tpr_shadow vnmi flexpriority 
>> ept vpid fsgsbase tsc_adjust bmi1 hle avx2 smep bmi2 erms invpcid rtm 
>> mpx avx512f avx512dq rdseed adx smap clflushopt clwb avx512cd avx512bw 
>> avx512vl xsaveopt xsavec xgetbv1 xsaves arat umip pku ospke md_clear
>> ...