On Mon, 10 Apr 2023 15:16:59 GMT, Jatin Bhateja <jbhat...@openjdk.org> wrote:
>> Yes I think it is a drawback of this approach, however currently we do not
>> support shuffling for 256-bit vectors on AVX1 machines either, and AVX1
>> seems to be a special case in this regard. This species of float and double
>> may also be less common in the usage of Vector API since it is larger than
>> SPECIES_PREFERRED.
>
> Hi @merykitty , Agree with you that SPECIES_PREFERRED is preferred for vector
> algorithms intercepting both integral and floating point vectors.
>
> FTR, we see a perf regression with Float256 based micro now on AVX=1 targets,
>
>
> public static short micro() {
> VectorShuffle<Float> iota = FloatVector.SPECIES_256.iotaShuffle(0, 1,
> true);
> return
> iota.cast(ShortVector.SPECIES_128).toVector().reinterpretAsShorts().lane(1);
> }
>
> CPROMPT>javad --add-modules=jdk.incubator.vector -XX:UseAVX=1
> -XX:+PrintIntrinsics -XX:CompileCommand=compileonly,shufflef::micro -cp .
> shufflef
> CompileCommand: compileonly shufflef.micro bool compileonly = true
> ** not supported: arity=1 op=reinterpret/1 vlen1=8 etype1=int ismask=0
> ** not supported: arity=1 op=cast/1 vlen1=8 etype1=int ismask=0
> @ 17 java.lang.Object::getClass (0
> bytes) (intrinsic)
> @ 24 java.lang.Object::getClass (0
> bytes) (intrinsic)
> @ 45
> jdk.internal.vm.vector.VectorSupport::convert (36 bytes) failed to inline
> (intrinsic)
> @ 34 java.lang.Object::getClass (0 bytes)
> (intrinsic)
> @ 54
> jdk.internal.vm.vector.VectorSupport::convert (36 bytes) failed to inline
> (intrinsic)
> @ 17 java.lang.Object::getClass (0
> bytes) (intrinsic)
> @ 24 java.lang.Object::getClass (0
> bytes) (intrinsic)
> @ 45
> jdk.internal.vm.vector.VectorSupport::convert (36 bytes) (intrinsic)
> @ 292 java.lang.Object::getClass (0
> bytes) (intrinsic)
> @ 298 java.lang.Object::getClass (0
> bytes) (intrinsic)
> @ 322
> jdk.internal.vm.vector.VectorSupport::convert (36 bytes) (intrinsic)
> @ 292 java.lang.Object::getClass (0
> bytes) (intrinsic)
> @ 298 java.lang.Object::getClass (0
> bytes) (intrinsic)
> @ 322
> jdk.internal.vm.vector.VectorSupport::convert (36 bytes) (intrinsic)
> @ 16
> jdk.internal.vm.vector.VectorSupport::extract (35 bytes) (intrinsic)
> [time] 386ms [res]3392
> CPROMPT>export JAVA_HOME=/home/jatinbha/softwares/jdk-20/
> CPROMPT>export PATH=$JAVA_HOME/bin:$PATH
> CPROMPT>javad --add-modules=jdk.incubator.vector -XX:UseAVX=1
> -XX:+PrintIntrinsics -XX:CompileCommand=compileonly,shufflef::micro -cp .
> shufflef
> CompileCommand: compileonly shufflef.micro bool compileonly = true
> WARNING: Using incubator modules: jdk.incubator.vector
> @ 3
> jdk.internal.misc.Unsafe::loadFence (5 bytes) (intrinsic)
> @ 3
> jdk.internal.misc.Unsafe::loadFence (5 bytes) (intrinsic)
> @ 17
> jdk.internal.vm.vector.VectorSupport::shuffleToVector (33 bytes) (intrinsic)
> @ 292 java.lang.Object::getClass (0
> bytes) (intrinsic)
> @ 298 java.lang.Object::getClass (0
> bytes) (intrinsic)
> @ 322
> jdk.internal.vm.vector.VectorSupport::convert (36 bytes) (intrinsic)
> @ 16
> jdk.internal.vm.vector.VectorSupport::extract (35 bytes) (intrinsic)
> [time] 7ms [res]3392
@jatin-bhateja Since `Float256Shuffle` is represented as a 256-bit int vector,
which is not supported by AVX1, the compiled code falls back to Java
implementation, which explains the regression. However, having a
`VectorShuffle` but not for `Vector::rearrange` is not really useful, and the
code snippet is similar to `ShortVector.SPECIES_128.iotaShuffle(0, 1,
true).toVector().reinterpretAsShorts().lane(1)`. As a result, I think having
some regressions in edge cases of AVX1 is acceptable in contrast with the
improvement in all other operations on all platforms.
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/13093#discussion_r1162555106
