RFR: 8323116: [REDO] Computational test more than 2x slower when AVX instructions are used [v5]

[Sandhya Viswanathan]

On Fri, 5 Apr 2024 15:57:03 GMT, Srinivas Vamsi Parasa <duke at openjdk.org> wrote:

>> src/hotspot/cpu/x86/assembler_x86.cpp line 11713:
>> 
>>> 11711:   }
>>> 11712: 
>>> 11713:   if (UseAVX > 2 && !attributes->uses_vl()) {
>> 
>> This is already coved by below assertion
>
> Without this check, the test is failing for KNL (-XX:UseAVX=3 -XX:+UnlockDiagnosticVMOptions -XX:+UseKNLSetting) as Vladimir mentioned. Is there a better way to handle the KNL case?

Yes, there is an easy way. For the instructs where you added the pxor instruction generation, you could change the dst register type from regF to  vlRegF. This restricts the xmm register to xmm0-xmm15 for KNL, thereby not needing the evex encoding and in-turn not needing the avx512vl support for pxor.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18503#discussion_r1554045455