[jdk17] RFR: 8269825: [TESTBUG] Missing testing for x86 KNL platforms

[Vladimir Kozlov]

Knights family of X86 Intel CPU (KNL) does not support some of avx512 features (AVX512VL/BW) and have other restrictions. We may not have such kind of machines in our testing environment and may miss bugs as JBS history shows (look recent fixes for KNL).
On other hand we have some Windows VM instances which seem emulate KNL configuration and limit avx512 instructions on CPU which supports full set. Recent bug JDK-8269775 shows such example.
I suggest to add -XX:+UseKNLSetting x86 diagnostic flag to emulate KNL settings in HotSpot VM to test such configuration.

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Commit messages:
 - 8269825: [TESTBUG] Missing testing for x86 KNL platforms

Changes: https://git.openjdk.java.net/jdk17/pull/205/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk17&pr=205&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8269825
  Stats: 4 lines in 2 files changed: 3 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk17/pull/205.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk17 pull/205/head:pull/205

PR: https://git.openjdk.java.net/jdk17/pull/205