RFR: 8267969: Add vectorized implementation for VectorMask.eq()

[Paul Sandoz]

On Mon, 31 May 2021 10:25:26 GMT, Xiaohong Gong <xgong at openjdk.org> wrote:

> Currently `"VectorMask.eq()" `is not vectorized:
> 
>     public VectorMask<E> eq(VectorMask<E> m) {
>         // FIXME: Generate good code here.
>         return bOp(m, (i, a, b) -> a == b);
>     }
> 
> This can be implemented by calling `"xor(m.not())"` directly.
> 
> The performance improved about 1.4x ~ 1.9x for the following benchmark with different basic types:
> 
> @Benchmark
> public Object eq() {
>     boolean[] ma = fm.apply(size);
>     boolean[] mb = fmb.apply(size);
>     boolean[] mt = fmt.apply(size);
>     VectorMask<Byte> m = VectorMask.fromArray(SPECIES, mt, 0);
> 
>     for (int ic = 0; ic < INVOC_COUNT; ic++) {
>         for (int i = 0; i < ma.length; i += SPECIES.length()) {
>             var av = SPECIES.loadMask(ma, i);
>             var bv = SPECIES.loadMask(mb, i);
> 
>             // accumulate results, so JIT can't eliminate relevant computations
>             m = m.and(av.eq(bv));
>         }
>     }
> 
>     return m;
> }

Looks. Later we may want to consider pushing this down as an intrinsic, perhaps reusing `VectorSupport.compare`.

-------------

Marked as reviewed by psandoz (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/4272