On Tue, 24 Sep 2024 07:10:24 GMT, Jatin Bhateja <jbhat...@openjdk.org> wrote:
>> Hi All,
>>
>> As per the discussion on panama-dev mailing list[1], patch adds the support
>> for following new two vector permutation APIs.
>>
>>
>> Declaration:-
>> Vector<E>.selectFrom(Vector<E> v1, Vector<E> v2)
>>
>>
>> Semantics:-
>> Using index values stored in the lanes of "this" vector, assemble the
>> values stored in first (v1) and second (v2) vector arguments. Thus, first
>> and second vector serves as a table, whose elements are selected based on
>> index value vector. API is applicable to all integral and floating-point
>> types. The result of this operation is semantically equivalent to
>> expression v1.rearrange(this.toShuffle(), v2). Values held in index vector
>> lanes must lie within valid two vector index range [0, 2*VLEN) else an
>> IndexOutOfBoundException is thrown.
>>
>> Summary of changes:
>> - Java side implementation of new selectFrom API.
>> - C2 compiler IR and inline expander changes.
>> - In absence of direct two vector permutation instruction in target ISA, a
>> lowering transformation dismantles new IR into constituent IR supported by
>> target platforms.
>> - Optimized x86 backend implementation for AVX512 and legacy target.
>> - Function tests covering new API.
>>
>> JMH micro included with this patch shows around 10-15x gain over existing
>> rearrange API :-
>> Test System: Intel(R) Xeon(R) Platinum 8480+ [ Sapphire Rapids Server]
>>
>>
>> Benchmark (size) Mode Cnt
>> Score Error Units
>> SelectFromBenchmark.rearrangeFromByteVector 1024 thrpt 2 2041.762
>> ops/ms
>> SelectFromBenchmark.rearrangeFromByteVector 2048 thrpt 2 1028.550
>> ops/ms
>> SelectFromBenchmark.rearrangeFromIntVector 1024 thrpt 2 962.605
>> ops/ms
>> SelectFromBenchmark.rearrangeFromIntVector 2048 thrpt 2 479.004
>> ops/ms
>> SelectFromBenchmark.rearrangeFromLongVector 1024 thrpt 2 359.758
>> ops/ms
>> SelectFromBenchmark.rearrangeFromLongVector 2048 thrpt 2 178.192
>> ops/ms
>> SelectFromBenchmark.rearrangeFromShortVector 1024 thrpt 2 1463.459
>> ops/ms
>> SelectFromBenchmark.rearrangeFromShortVector 2048 thrpt 2 727.556
>> ops/ms
>> SelectFromBenchmark.selectFromByteVector 1024 thrpt 2 33254.830
>> ops/ms
>> SelectFromBenchmark.selectFromByteVector 2048 thrpt 2 17313.174
>> ops/ms
>> SelectFromBenchmark.selectFromIntVector 1024 thrpt 2 10756.804
>> ops/ms
>> S...
>
> Jatin Bhateja has updated the pull request incrementally with one additional
> commit since the last revision:
>
> Handling NPOT vector length for AArch64 SVE with vector sizes varying b/w
> 128 and 2048 bits at 128 bit increments.
src/hotspot/share/opto/vectorIntrinsics.cpp line 2689:
> 2687: !arch_supports_vector(cast_vopc, num_elem, T_BYTE,
> VecMaskNotUsed) ||
> 2688: !arch_supports_vector(Op_VectorLoadShuffle, num_elem,
> index_elem_bt, VecMaskNotUsed) ||
> 2689: !arch_supports_vector(Op_Replicate, num_elem, T_BYTE,
> VecMaskNotUsed)) {
Where SelectFromTwoVector is not supported, the alternate implementation is as
part of SelectFromTwoVectorNode::Ideal() instead of right here. A comment both
here as well as in the Ideal() implementation is needed to keep these checks in
sync.
src/hotspot/share/opto/vectornode.cpp line 2120:
> 2118: // are held in a byte vector which are later transformed to target
> specific permutation
> 2119: // index format by subsequent VectorLoadShuffle.
> 2120: int cast_vopc = VectorCastNode::opcode(0, index_elem_bt, true);
Good to use -1 when we are not sending an actual opcode:
int cast_vopc = VectorCastNode::opcode(-1, index_elem_bt, true);
src/hotspot/share/opto/vectornode.cpp line 2126:
> 2124: Node* bcast_lane_cnt_m1_vec =
> phase->transform(VectorNode::scalar2vector(lane_cnt_m1, num_elem,
> Type::get_const_basic_type(T_BYTE), false));
> 2125:
> 2126: // Compute the blend mask for merging two indipendently permututed
> vectors
Typo indipendently -> independently
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/20508#discussion_r1781867326
PR Review Comment: https://git.openjdk.org/jdk/pull/20508#discussion_r1781873682
PR Review Comment: https://git.openjdk.org/jdk/pull/20508#discussion_r1781888912
