RFR: 8356760: VectorAPI: Optimize VectorMask.fromLong for all-true/all-false cases [v3]

[Jatin Bhateja]

On Mon, 7 Jul 2025 03:43:44 GMT, erifan <duke at openjdk.org> wrote:

> > > > public static final VectorSpecies FSP = FloatVector.SPECIES_512;
> > > > public static long micro1(long a) {
> > > > long mask = Math.min(-1, Math.max(-1, a));
> > > > return VectorMask.fromLong(FSP, mask).toLong();
> > > > }
> > > > public static long micro2() {
> > > > return FSP.maskAll(true).toLong();
> > > > }
> > > 
> > > 
> > > With this JMH method we can not see obvious performance improvement, because the hot spots are other instructions. Adding a loop is better.
> > 
> > 
> > There is no hard and fast rule for the inclusion of a loop in a JMH micro in that case?
> 
> You mean adding a loop is not a block, right ?

Yes. If you see gains without loop go for it.

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PR Comment: https://git.openjdk.org/jdk/pull/25793#issuecomment-3044086773