RFR: 8367694: Fix jtreg test failure when Intel APX is enabled for KNL platforms [v2]

[Sandhya Viswanathan]

On Mon, 15 Sep 2025 20:08:10 GMT, Srinivas Vamsi Parasa <sparasa at openjdk.org> wrote:

>> This goal of this PR is fix the jtreg test failure observed in compiler test: `test/hotspot/jtreg/compiler/loopopts/superword/TestDependencyOffsets.java`
>> 
>> The test failure is occurring specifically for the tests with ids = {avx512-v064-A, avx512-v064-U, avx512-v032-A, avx512-v032-U}. These tests are run with KNL hardware features enabled (`-XX:+UseKNLSetting`). 
>> 
>> The two main causes of test failure are: 
>> 1. KNL does not support Intel APX. Currently, APX is not turned off when using KNL. This PR fixes this issue.
>> 2. BMI2 instructions like sarxl are encoded incorrectly with `uses_vl=true` (use vector length). This PR fixes the encoding to use the correct one:`uses_vl=false`.
>> 
>> After fixing these two bugs, `TestDependencyOffsets.java` is passing using the SDE emulator when APX is enabled.
>
> Srinivas Vamsi Parasa has updated the pull request incrementally with one additional commit since the last revision:
> 
>   change the location of APX feature check

Looks good to me.

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Marked as reviewed by sviswanathan (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/27299#pullrequestreview-3226157178