TrueCloudLab/tzhash
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Optimize AVX2 implementation

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We use 6 instructions only to calculate mask based on single bit value.
Use only 3 now and calculate multiple masks in parallel.

Also `VPSUB*` is faster than VPBROADCAST*,
see https://www.intel.com/content/www/us/en/docs/intrinsics-guide/index.html .

```
name                     old time/op    new time/op    delta
Sum/AVX2Inline_digest-8    1.83ms ± 0%    1.62ms ± 1%  -11.23%  (p=0.000 n=46+42)

name                     old speed      new speed      delta
Sum/AVX2Inline_digest-8  54.7MB/s ± 0%  61.6MB/s ± 1%  +12.65%  (p=0.000 n=46+42)
```

Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>
This commit is contained in:
Evgenii Stratonikov 2021-12-28 20:24:59 +03:00 committed by Alex Vanin
parent a370c525ba
commit c8a32b25ec
1 changed files with 12 additions and 9 deletions
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21
tz/avx2_amd64.s
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@ -1,12 +1,9 @@
#include "textflag.h"
#define mask(bit, src, tmp, to1, to2) \
MOVQ src, tmp \
SHRQ bit, tmp \
ANDQ $1, tmp \
NEGQ tmp \
MOVQ tmp, to1 \
VPBROADCASTB to1, to2
#define mask(bit, tmp, to) \
VPSRLW bit, Y10, tmp \
VPAND Y12, tmp, to \ // to2 = 0x000<bit>000<bit>...
VPSUBW to, Y13, to // to2 = 0xFFFF.. or 0x0000 depending on bit
#define mulBit(bit) \
VPSLLQ $1, Y0, Y1 \
@ -17,7 +14,7 @@
VPSLLQ $63, Y3, Y3 \
VPUNPCKHQDQ Y3, Y3, Y3 \
VPXOR Y2, Y3, Y3 \
mask(bit, CX, DX, X1, Y2) \
mask(bit, Y11, Y2) \
VPXOR Y3, Y8, Y3 \
VPAND Y3, Y2, Y4 \
VPXOR Y4, Y0, Y8 \
@ -29,7 +26,13 @@ TEXT ·mulByteRightx2(SB),NOSPLIT,$0
VMOVDQA (AX), Y0
MOVQ c01c11+8(FP), BX
VMOVDQA (BX), Y8
MOVB b+16(FP), CX
VPXOR Y13, Y13, Y13 // Y13 = 0x0000...
VPCMPEQB Y12, Y12, Y12 // Y12 = 0xFFFF...
VPSUBW Y12, Y13, Y12 // Y12 = 0x00010001... (packed words of 1)
VPBROADCASTB b+16(FP), X10 // X10 = packed bytes of b.
VPMOVZXBW X10, Y10 // Extend with zeroes to packed words.
mulBit($7)
mulBit($6)