[vector] RFR (L): Generalized intrinsics for vector operations (first batch)

[Lupusoru, Razvan A]

Hi Vladimir,

The patch looks great and you have my +1 as well.

--Razvan

-----Original Message-----
From: panama-dev [mailto:panama-dev-bounces at openjdk.java.net] On Behalf Of Vladimir Ivanov
Sent: Friday, February 09, 2018 2:55 PM
To: 'panama-dev at openjdk.java.net' <panama-dev at openjdk.java.net>
Subject: Re: [vector] RFR (L): Generalized intrinsics for vector operations (first batch)

One thing I forgot to mention: original memory vector operations
(fromArray/intoArray) miss bounds checks.

The patch put them in place, but current shape of the checks has significant performance overhead (up to 2x on simple benchmarks).

I proposed some ideas how to improve them [1] and believe it's possible to optimize them as ordinary array OOB checks, but it's a task for future exploration.

Meanwhile, there's a temporary flag to turn OOB checks off (by default, the checks are turned on):

   -Djdk.incubator.vector.VECTOR_ACCESS_OOB_CHECK=false

Best regards,
Vladimir Ivanov

[1]
http://mail.openjdk.java.net/pipermail/panama-dev/2017-December/000889.html

On 2/10/18 12:38 AM, Vladimir Ivanov wrote:
> http://cr.openjdk.java.net/~vlivanov/panama/vector.generalized_intrins
> ics/webrev.06/
> 
> 
> Here's the first batch of rewritten intrinsics for vector operations.
> 
> Main motivation for new implementation is:
>    * reduce number of intrinsic needed;
>    * improve intrinsification robustness;
>    * minimize changes needed in shared C2 code.
> 
> The idea of generalized intrinsics is to parameterize them with 
> additional information (passed as constant arguments), so JIT-compiler 
> has enough information to dispatch to proper implementation during 
> intrinsification.
> 
> For example, binary vector operation can be represented as:
> 
>    // (V,V) -> V
>    @HotSpotIntrinsicCandidate
>    static <V> V binaryOp(int oprId, Class<V> vectorClass,
>                          Class<?> elementType, int vlen,
>                          V v1, V v2,
>                          BiFunction<V,V,V> defaultImpl) {
>        return defaultImpl.apply(v1, v2);
>    }
> 
> and used as:
> 
>    // (Int256Vector,Int256Vector) -> Int256Vector
> 
>    public Int256Vector add(Vector<Integer,Shapes.S256Bit> v) {
>      return (Int256Vector) VectorIntrinsics.binaryOp(
>              VECTOR_OP_ADD,
>              Int256Vector.class, int.class, 8,
>              this, (Int256Vector)v,
>              (v1, v2) -> ((Int256Vector)v1).bOp(v2,
>                                     (i, a, b) -> (int)(a+b)));
>    }
> 
> where:
>    oprId encodes actual operation (VECTOR_OP_ADD);
> 
>    vectorClass, elementType, vlen describe concrete vector class 
> (Int256Vector);
> 
>    v1, v2 are actual arguments of vector binary operations;
> 
>    defaultImpl - scalar implementation which is used when 
> intrinsification fails.
> 
> 
> Generalized intrinsics are declared on 
> jdk.incubator.vector.VectorIntrinsics and the patch contains 6 of them:
>    * broadcastCoerced
>    * reductionCoerced
>    * binaryOp
>    * load/store
>    * test
> 
> The following vector operations were ported to new mechanism:
>    * broadcast: zero, broadcast, trueMask, falseMask
>    * reduction: addAll, mulAll
>    * binaryOp: add, sub, mul, div, and, or, xor
>    * load/store: intoArray, fromArray
>    * test: anyTrue, allTrue
> 
> There's new flag added to turn new intrinsics on/off:
> 
> +  product(bool, UseVectorApiGeneralizedIntrinsics, true,
> 
> Previous discussions [1] [2].
> 
> The patch adds alternative implementations, but doesn't remove 
> existing ones, since there are some code dependencies on them. Once 
> the dependencies are broken, the code will go away.
> 
> Thanks!
> 
> Best regards,
> Vladimir Ivanov
> 
> [1]
> http://mail.openjdk.java.net/pipermail/panama-dev/2017-November/000748
> .html
> 
> [2]
> http://mail.openjdk.java.net/pipermail/panama-dev/2017-December/000884
> .html