RFR: 8304450: [vectorapi] Refactor VectorShuffle implementation [v5]

[Paul Sandoz]

On Thu, 30 Mar 2023 14:30:17 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 with a new target base due to a merge or a rebase. The pull request now contains 14 commits:
> 
>  - move implementations up
>  - Merge branch 'master' into shufflerefactor
>  - Merge branch 'master' into shufflerefactor
>  - reviews
>  - missing casts
>  - clean up
>  - fix Matcher::vector_needs_load_shuffle
>  - fix internal types, clean up
>  - optimise laneIsValid
>  - Merge branch 'master' into shufflerefactor
>  - ... and 4 more: https://git.openjdk.org/jdk/compare/d063b896...a4835c00

src/jdk.incubator.vector/share/classes/jdk/incubator/vector/X-VectorBits.java.template line 1106:

> 1104:         @Override
> 1105:         @ForceInline
> 1106:         public int laneSource(int i) {

Can this method be moved to `AbstractShuffle`?

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

PR Review Comment: https://git.openjdk.org/jdk/pull/13093#discussion_r1153902133