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cdecimate2xuint8x8.c
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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2020 Justine Alexandra Roberts Tunney │
│ │
│ Permission to use, copy, modify, and/or distribute this software for │
│ any purpose with or without fee is hereby granted, provided that the │
│ above copyright notice and this permission notice appear in all copies. │
│ │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/macros.h"
#include "libc/nexgen32e/x86feature.h"
#include "libc/str/str.h"
#include "third_party/intel/immintrin.internal.h"
/**
* Performs 2D Motion Picture Convolution Acceleration by Leveraging SSSE3.
*
* @note H/T John Costella, Jean-Baptiste Joseph Fourier
* @note RIP Huixiang Chen
*/
void *cDecimate2xUint8x8(unsigned long n, unsigned char A[n],
const signed char K[8]) {
#ifdef __x86_64__
#define TAPS 8
#define RATIO 2
#define OFFSET 3
#define STRIDE 8
#define SPREAD (STRIDE * RATIO + TAPS - OFFSET)
#define OVERLAP (SPREAD - STRIDE * RATIO)
#define LOOKBEHIND OFFSET
#define LOOKAHEAD (SPREAD - LOOKBEHIND)
#define SCALE 5
#define ROUND (1 << (SCALE - 1))
__m128i kRound = _mm_set1_epi16(ROUND);
__m128i kMadd1 = _mm_set_epi8(K[1], K[0], K[1], K[0], K[1], K[0], K[1], K[0],
K[1], K[0], K[1], K[0], K[1], K[0], K[1], K[0]);
__m128i kMadd2 = _mm_set_epi8(K[3], K[2], K[3], K[2], K[3], K[2], K[3], K[2],
K[3], K[2], K[3], K[2], K[3], K[2], K[3], K[2]);
__m128i kMadd3 = _mm_set_epi8(K[5], K[4], K[5], K[4], K[5], K[4], K[5], K[4],
K[5], K[4], K[5], K[4], K[5], K[4], K[5], K[4]);
__m128i kMadd4 = _mm_set_epi8(K[7], K[6], K[7], K[6], K[7], K[6], K[7], K[6],
K[7], K[6], K[7], K[6], K[7], K[6], K[7], K[6]);
__m128i bv0, bv1, bv2, bv3;
__m128i in1, in2, in3;
__m128i wv0, wv1, wv2, wv3;
unsigned long i, j, w;
if (n >= STRIDE) {
i = 0;
w = (n + RATIO / 2) / RATIO;
in1 = _mm_set1_epi8(A[0]);
in2 = _mm_set1_epi8(A[n - 1]);
_mm_storeu_si128((__m128i *)&in2, _mm_loadu_si128((__m128i *)A));
for (; i < w; i += STRIDE) {
j = i * RATIO + 16;
if (j + 16 <= n) {
in3 = _mm_loadu_si128((__m128i *)&A[j]);
} else {
in3 = _mm_set1_epi8(A[n - 1]);
if (j < n) {
// SSSE3-compatible way to handle partial loads
__m128i mask = _mm_loadu_si128((__m128i *)&A[j]);
__m128i shuffle_mask = _mm_set_epi8(15, 14, 13, 12, 11, 10, 9, 8, 7,
6, 5, 4, 3, 2, 1, 0);
__m128i index = _mm_set1_epi8(n - j);
__m128i cmp = _mm_cmplt_epi8(shuffle_mask, index);
in3 = _mm_or_si128(_mm_and_si128(cmp, mask),
_mm_andnot_si128(cmp, in3));
}
}
bv0 = _mm_alignr_epi8(in2, in1, 13);
bv1 = _mm_alignr_epi8(in2, in1, 15);
bv2 = _mm_alignr_epi8(in3, in2, 1);
bv3 = _mm_alignr_epi8(in3, in2, 3);
wv0 = _mm_maddubs_epi16(bv0, kMadd1);
wv1 = _mm_maddubs_epi16(bv1, kMadd2);
wv2 = _mm_maddubs_epi16(bv2, kMadd3);
wv3 = _mm_maddubs_epi16(bv3, kMadd4);
wv0 = _mm_add_epi16(wv0, kRound);
wv0 = _mm_add_epi16(wv0, wv1);
wv0 = _mm_add_epi16(wv0, wv2);
wv0 = _mm_add_epi16(wv0, wv3);
wv0 = _mm_srai_epi16(wv0, SCALE);
bv2 = _mm_packus_epi16(wv0, wv0);
_mm_storel_epi64((__m128i *)&A[i], bv2);
in1 = in2;
in2 = in3;
}
}
return A;
#else
long h, i;
if (n < 2)
return A;
unsigned char M[3 + n + 4];
unsigned char *q = M;
q[0] = A[0];
q[1] = A[0];
q[2] = A[0];
memcpy(q + 3, A, n);
q[3 + n + 0] = A[n - 1];
q[3 + n + 1] = A[n - 1];
q[3 + n + 2] = A[n - 1];
q[3 + n + 3] = A[n - 1];
q += 3;
h = (n + 1) >> 1;
for (i = 0; i < h; ++i) {
short x0, x1, x2, x3, x4, x5, x6, x7;
x0 = q[i * 2 - 3];
x1 = q[i * 2 - 2];
x2 = q[i * 2 - 1];
x3 = q[i * 2 + 0];
x4 = q[i * 2 + 1];
x5 = q[i * 2 + 2];
x6 = q[i * 2 + 3];
x7 = q[i * 2 + 4];
x0 *= K[0];
x1 *= K[1];
x2 *= K[2];
x3 *= K[3];
x4 *= K[4];
x5 *= K[5];
x6 *= K[6];
x7 *= K[7];
x0 += x1;
x2 += x3;
x4 += x5;
x6 += x7;
x0 += x2;
x4 += x6;
x0 += x4;
x0 += 1 << 4;
x0 >>= 5;
A[i] = MIN(255, MAX(0, x0));
}
return A;
#endif
}