On Tue, 21 Mar 2023 16:16:31 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 incrementally with two additional
> commits since the last revision:
>
> - missing casts
> - clean up
src/jdk.incubator.vector/share/classes/jdk/incubator/vector/AbstractShuffle.java
line 118:
> 116: return (VectorShuffle<E>)
> v.rearrange(shuffle.cast(vspecies().asIntegral()))
> 117: .toShuffle()
> 118: .cast(vspecies());
Style issue. Suggest to change to:
return (VectorShuffle<E>) v.rearrange(shuffle.cast(vspecies().asIntegral()))
.toShuffle()
.cast(vspecies());
I also noticed that the similar shuffle cast code is used more frequently.
Could we wrap such code `toShuffle().cast(vspecies())` to a separate method?
src/jdk.incubator.vector/share/classes/jdk/incubator/vector/AbstractShuffle.java
line 130:
> 128: } else {
> 129: v = v.blend(v.lanewise(VectorOperators.ADD, length()),
> 130: v.compare(VectorOperators.LT, 0));
Style issue. Suggest to change to:
v = v.blend(v.lanewise(VectorOperators.ADD, length()),
v.compare(VectorOperators.LT, 0));
src/jdk.incubator.vector/share/classes/jdk/incubator/vector/AbstractVector.java
line 198:
> 196: if ((length() & (length() - 1)) != 0) {
> 197: return wrap ? shuffleFromOp(i ->
> (VectorIntrinsics.wrapToRange(i * step + start, length())))
> 198: : shuffleFromOp(i -> i * step + start);
Code style issue. Suggest to:
return wrap ? shuffleFromOp(i -> (VectorIntrinsics.wrapToRange(i * step +
start, length())))
: shuffleFromOp(i -> i * step + start);
src/jdk.incubator.vector/share/classes/jdk/incubator/vector/AbstractVector.java
line 204:
> 202: Vector iota = species.iota();
> 203: iota = iota.lanewise(VectorOperators.MUL, step)
> 204: .lanewise(VectorOperators.ADD, start);
Style issue. Same as above.
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/13093#discussion_r1144384585
PR Review Comment: https://git.openjdk.org/jdk/pull/13093#discussion_r1144389023
PR Review Comment: https://git.openjdk.org/jdk/pull/13093#discussion_r1144390218
PR Review Comment: https://git.openjdk.org/jdk/pull/13093#discussion_r1144390692
