RFR: 8289604: compiler/vectorapi/VectorLogicalOpIdentityTest.java failed on x86 AVX1 system

[Vladimir Kozlov]

On Tue, 5 Jul 2022 07:47:58 GMT, Xiaohong Gong <xgong at openjdk.org> wrote:

> The sub-test "`testMaskAndZero()`" failed on x86 systems when
> `UseAVX=1` with the IR check failure:
> 
>   - counts: Graph contains wrong number of nodes:
>      * Regex 1: (\\d+(\\s){2}(StoreVector.*)+(\\s){2}===.*)
>         - Failed comparison: [found] 0 >= 1 [given]
>         - No nodes matched!
> 
> The root cause is the `VectorMask.fromArray/intoArray` APIs
> are not intrinsified when "`UseAVX=1`" for long type vectors
> with following reasons:
>  1) The system supported max vector size is 128 bits for
> integral vector operations when "`UseAVX=1`".
>  2) The match rule of `VectorLoadMaskNode/VectorStoreMaskNode`
> are not supported for vectors with 2 elements (see [1]).
> 
> Note that `VectorMask.fromArray()` needs to be intrinsified
> with "`LoadVector+VectorLoadMask`". And `VectorMask.intoArray()`
> needs to be intrinsified with "`VectorStoreMask+StoreVector`".
> Either "`VectorStoreMask`" or "`StoreVector`" not supported by the
> compiler backend will forbit the relative API intrinsification.
> 
> Replacing the vector type from Long to other integral types
> in the test case can fix the issue.
> 
> [1] https://github.com/openjdk/jdk/blob/master/src/hotspot/cpu/x86/x86.ad#L1861

Including @chhagedorn for discussion.

I was wondering why our testing with `UseAVX=1` did not catch this issue (test passed).
But then I remember that IR framework skip testing if such flag is used by testing. It is not on whitelist:
https://github.com/openjdk/jdk/blob/master/test/hotspot/jtreg/compiler/lib/ir_framework/TestFramework.java#L104

We are adding more IR framework testing for vectors. I think it is important to test them with different CPU's features **if needed**.

https://github.com/openjdk/jdk/pull/8999 added filter to run some sub-tests if CPU's feature is present/absent. But it relies on testing infrastructure to be executed on corresponding machine. It is not reliable (how many machines left with only AVX1).

I suggest to allow a test add flags to whitelist with which it allows to run. It (together with #8999 and `@requires`) will allow test's author to specify range of CPU features which can be used for test and make sure they will be run.

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PR: https://git.openjdk.org/jdk/pull/9373