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

[Vladimir Ivanov]

http://cr.openjdk.java.net/~vlivanov/panama/vector.generalized_intrinsics/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