On Thu, 30 Mar 2023 14:30:17 GMT, Quan Anh Mai <qa...@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
The changes look very good to me. It would be useful if @jatin-bhateja could
also take a look.
src/jdk.incubator.vector/share/classes/jdk/incubator/vector/X-VectorBits.java.template
line 1158:
> 1156: }
> 1157:
> 1158: private static $bitstype$[] prepare(int[] indices, int offset) {
If we want to reduce code duplication further I suspect we could move these
static methods to IntVector etc. Up to you.
-------------
Marked as reviewed by psandoz (Reviewer).
PR Review: https://git.openjdk.org/jdk/pull/13093#pullrequestreview-1366098245
PR Review Comment: https://git.openjdk.org/jdk/pull/13093#discussion_r1153904271
