RFR: 8304450: [vectorapi] Refactor VectorShuffle implementation [v4]

[Xiaohong Gong]

On Wed, 22 Mar 2023 12:46:33 GMT, Quan Anh Mai <qamai at openjdk.org> wrote:

>> Hi,
>> 
>> This patch reimplements `VectorShuffle` implementations to be a vector of the bit type. Currently, VectorShuffle is stored as a byte array, and would be expanded upon usage. This poses several drawbacks:
>> 
>> 1. Inefficient conversions between a shuffle and its corresponding vector. This hinders the performance when the shuffle indices are not constant and are loaded or computed dynamically.
>> 2. Redundant expansions in `rearrange` operations. On all platforms, it seems that a shuffle index vector is always expanded to the correct type before executing the `rearrange` operations.
>> 3. Some redundant intrinsics are needed to support this handling as well as special considerations in the C2 compiler.
>> 4. Range checks are performed using `VectorShuffle::toVector`, which is inefficient for FP types since both FP conversions and FP comparisons are more expensive than the integral ones.
>> 
>> Upon these changes, a `rearrange` can emit more efficient code:
>> 
>>     var species = IntVector.SPECIES_128;
>>     var v1 = IntVector.fromArray(species, SRC1, 0);
>>     var v2 = IntVector.fromArray(species, SRC2, 0);
>>     v1.rearrange(v2.toShuffle()).intoArray(DST, 0);
>> 
>>     Before:
>>     movabs $0x751589fa8,%r10            ;   {oop([I{0x0000000751589fa8})}
>>     vmovdqu 0x10(%r10),%xmm2
>>     movabs $0x7515a0d08,%r10            ;   {oop([I{0x00000007515a0d08})}
>>     vmovdqu 0x10(%r10),%xmm1
>>     movabs $0x75158afb8,%r10            ;   {oop([I{0x000000075158afb8})}
>>     vmovdqu 0x10(%r10),%xmm0
>>     vpand  -0xddc12(%rip),%xmm0,%xmm0        # Stub::vector_int_to_byte_mask
>>                                                             ;   {external_word}
>>     vpackusdw %xmm0,%xmm0,%xmm0
>>     vpackuswb %xmm0,%xmm0,%xmm0
>>     vpmovsxbd %xmm0,%xmm3
>>     vpcmpgtd %xmm3,%xmm1,%xmm3
>>     vtestps %xmm3,%xmm3
>>     jne    0x00007fc2acb4e0d8
>>     vpmovzxbd %xmm0,%xmm0
>>     vpermd %ymm2,%ymm0,%ymm0
>>     movabs $0x751588f98,%r10            ;   {oop([I{0x0000000751588f98})}
>>     vmovdqu %xmm0,0x10(%r10)
>> 
>>     After:
>>     movabs $0x751589c78,%r10            ;   {oop([I{0x0000000751589c78})}
>>     vmovdqu 0x10(%r10),%xmm1
>>     movabs $0x75158ac88,%r10            ;   {oop([I{0x000000075158ac88})}
>>     vmovdqu 0x10(%r10),%xmm2
>>     vpxor  %xmm0,%xmm0,%xmm0
>>     vpcmpgtd %xmm2,%xmm0,%xmm3
>>     vtestps %xmm3,%xmm3
>>     jne    0x00007fa818b27cb1
>>     vpermd %ymm1,%ymm2,%ymm0
>>     movabs $0x751588c68,%r10            ;   {oop([I{0x0000000751588c68})}
>>     vmovdqu %xmm0,0x10(%r10)
>>     
>> Please take a look and leave reviews. Thanks a lot.
>
> Quan Anh Mai has updated the pull request incrementally with one additional commit since the last revision:
> 
>   reviews

src/jdk.incubator.vector/share/classes/jdk/incubator/vector/Byte128Vector.java line 868:

> 866:             return (Byte128Vector) Byte128Vector.VSPECIES.dummyVector()
> 867:                     .vectorFactory(s.indices());
> 868:         }

Move the implementation details to the super class?

src/jdk.incubator.vector/share/classes/jdk/incubator/vector/ByteMaxVector.java line 862:

> 860:             v.convertShape(VectorOperators.B2I, species, 3)
> 861:                     .reinterpretAsInts()
> 862:                     .intoArray(a, offset + species.length() * 3);

Can we add a method like `intoIntArray()` in `ByteVector` and move these common code there? The same to other vector types.

src/jdk.incubator.vector/share/classes/jdk/incubator/vector/ByteMaxVector.java line 919:

> 917:                     }
> 918:                     return false;
> 919:                 }

Same as `intoArray()`. Any possible that moving this function to `ByteVector` and rename it to something like `shuffleIndicesInRange` ?

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

PR Review Comment: https://git.openjdk.org/jdk/pull/13093#discussion_r1145769798
PR Review Comment: https://git.openjdk.org/jdk/pull/13093#discussion_r1145781044
PR Review Comment: https://git.openjdk.org/jdk/pull/13093#discussion_r1145782910