[Vector API] Question about SPECIES_64 for DoubleVector and LongVector

[jiefu(傅杰)]

Hi all,

According to the JVM specification, both double and long are 64-bit.
So Double64Vector and Long64Vector are vectors which contain just 1 lane only.

But none of the 1-lane vectors would be get vectorized in HotSpot.
People who use Double64Vector and Long64Vector may encounter performance drop of their programs.

I didn't see any benefit of SPECIES_64 for DoubleVector and LongVector.
So why we provide them for programmers?

Thanks.
Best regards,
Jie