Vector API: VectorMask.fromLong is not intrinsified

[Jakub Okoński]

Hi,

I noticed that the following code doesn't get intrinsified:

    VectorMask.fromLong(ByteVector.SPECIES_128, someInt)

Profiling with JFR reveals that this method falls back to fromArray and
allocates a boolean[], which is undesirable.

It has to be this fallback code:
https://github.com/openjdk/jdk/blob/41ee582df8c65f2f26b21e46784cf0bc4ece0585/src/jdk.incubator.vector/share/classes/jdk/incubator/vector/VectorMask.java#L252

With PrintIntrin, I'm seeing this message

** missing constant: vclass=DecodeN etype=ConP vlen=LoadI bitwise=ConI

I modified the logging and narrowed it down to vector_klass->const_oop()
being a nullptr

https://github.com/openjdk/jdk/blob/41ee582df8c65f2f26b21e46784cf0bc4ece0585/src/hotspot/share/opto/vectorIntrinsics.cpp#L833

I then tried to cheat and hardcode the vector class and lane count in
VectorMask.java so it knows the arguments statically, like so:

        return VectorSupport.fromBitsCoerced((Class<? extends
AbstractMask<E>>) (Class<?>) Byte128Vector.Byte128Mask.class,
vsp.elementType(), 16, bits, ...

While this did make inlining happen (as reported by PrintIntrin at least),
I couldn't get rid of the boolean[] allocations.

I'm testing on 41ee582df8c65f2f26b21e46784cf0bc4ece0585 amd64 Linux.

Regards,
Jakub
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