On Sat, 27 Feb 2021 03:23:12 GMT, Jie Fu <ji...@openjdk.org> wrote:
>> Hi all,
>>
>> Vector API fails to work when:
>> - case 1: MaxVectorSize is set to <=8, or
>> - case 2: C2 is disabled
>>
>> The reason is that {max/preferred} VectorShape initialization fails in both
>> cases.
>> And the root cause is that VectorSupport_GetMaxLaneCount [1] returns
>> unreasonable values (0 for case 1 and -1 for case 2).
>>
>> Vector API should not depend on C2 to run.
>> It should work even there is no JIT compiler since it's a Java-level api.
>> So let's fix it.
>>
>> Testing:
>> - jdk/incubator/vector with -XX:MaxVectorSize=default/8 on Linux/x64
>>
>> Thanks.
>> Best regards,
>> Jie
>>
>> [1]
>> https://github.com/openjdk/jdk/blob/master/src/hotspot/share/prims/vectorSupport.cpp#L364
>
> Jie Fu has updated the pull request with a new target base due to a merge or
> a rebase. The incremental webrev excludes the unrelated changes brought in by
> the merge/rebase. The pull request contains seven additional commits since
> the last revision:
>
> - Fix in jdk/incubator/vector/VectorShape.java
> - Merge branch 'master' into JDK-8262096
> - Revert changes
> - Remove -XX:TieredStopAtLevel=3
> - Update the jtreg test
> - The numerator should be 8 (byte)
> - 8262096: Vector API fails to work due to VectorShape initialization
> exception
> For the updated fix, the {max/preferred} shape will be initialized as
> shape-64-bit if hotspot doesn't support vectorization.
Sounds reasonable.
test/jdk/jdk/incubator/vector/PreferredSpeciesTest.java line 42:
> 40: * @modules jdk.incubator.vector java.base/jdk.internal.vm.vector
> 41: * @run testng/othervm -XX:MaxVectorSize=8 PreferredSpeciesTest
> 42: * @run testng/othervm -XX:MaxVectorSize=4 PreferredSpeciesTest
`-XX:MaxVectorSize` is C2-specific. It's better to specify either
`-XX:-IgnoreUnrecognizedVMOptions` or `@requires vm.compiler2.enabled`.
-------------
Marked as reviewed by vlivanov (Reviewer).
PR: https://git.openjdk.java.net/jdk/pull/2722
