|
/* filter_sse2_intrinsics.c - SSE2 optimized filter functions
|
*
|
* Copyright (c) 2018 Cosmin Truta
|
* Copyright (c) 2016-2017 Glenn Randers-Pehrson
|
* Written by Mike Klein and Matt Sarett
|
* Derived from arm/filter_neon_intrinsics.c
|
*
|
* This code is released under the libpng license.
|
* For conditions of distribution and use, see the disclaimer
|
* and license in png.h
|
*/
|
|
#include "../pngpriv.h"
|
|
#ifdef PNG_READ_SUPPORTED
|
|
#if PNG_INTEL_SSE_IMPLEMENTATION > 0
|
|
#include <immintrin.h>
|
|
/* Functions in this file look at most 3 pixels (a,b,c) to predict the 4th (d).
|
* They're positioned like this:
|
* prev: c b
|
* row: a d
|
* The Sub filter predicts d=a, Avg d=(a+b)/2, and Paeth predicts d to be
|
* whichever of a, b, or c is closest to p=a+b-c.
|
*/
|
|
static __m128i load4(const void* p) {
|
int tmp;
|
memcpy(&tmp, p, sizeof(tmp));
|
return _mm_cvtsi32_si128(tmp);
|
}
|
|
static void store4(void* p, __m128i v) {
|
int tmp = _mm_cvtsi128_si32(v);
|
memcpy(p, &tmp, sizeof(int));
|
}
|
|
static __m128i load3(const void* p) {
|
png_uint_32 tmp = 0;
|
memcpy(&tmp, p, 3);
|
return _mm_cvtsi32_si128(tmp);
|
}
|
|
static void store3(void* p, __m128i v) {
|
int tmp = _mm_cvtsi128_si32(v);
|
memcpy(p, &tmp, 3);
|
}
|
|
void png_read_filter_row_sub3_sse2(png_row_infop row_info, png_bytep row,
|
png_const_bytep prev)
|
{
|
/* The Sub filter predicts each pixel as the previous pixel, a.
|
* There is no pixel to the left of the first pixel. It's encoded directly.
|
* That works with our main loop if we just say that left pixel was zero.
|
*/
|
size_t rb;
|
|
__m128i a, d = _mm_setzero_si128();
|
|
png_debug(1, "in png_read_filter_row_sub3_sse2");
|
|
rb = row_info->rowbytes;
|
while (rb >= 4) {
|
a = d; d = load4(row);
|
d = _mm_add_epi8(d, a);
|
store3(row, d);
|
|
row += 3;
|
rb -= 3;
|
}
|
if (rb > 0) {
|
a = d; d = load3(row);
|
d = _mm_add_epi8(d, a);
|
store3(row, d);
|
|
row += 3;
|
rb -= 3;
|
}
|
PNG_UNUSED(prev)
|
}
|
|
void png_read_filter_row_sub4_sse2(png_row_infop row_info, png_bytep row,
|
png_const_bytep prev)
|
{
|
/* The Sub filter predicts each pixel as the previous pixel, a.
|
* There is no pixel to the left of the first pixel. It's encoded directly.
|
* That works with our main loop if we just say that left pixel was zero.
|
*/
|
size_t rb;
|
|
__m128i a, d = _mm_setzero_si128();
|
|
png_debug(1, "in png_read_filter_row_sub4_sse2");
|
|
rb = row_info->rowbytes+4;
|
while (rb > 4) {
|
a = d; d = load4(row);
|
d = _mm_add_epi8(d, a);
|
store4(row, d);
|
|
row += 4;
|
rb -= 4;
|
}
|
PNG_UNUSED(prev)
|
}
|
|
void png_read_filter_row_avg3_sse2(png_row_infop row_info, png_bytep row,
|
png_const_bytep prev)
|
{
|
/* The Avg filter predicts each pixel as the (truncated) average of a and b.
|
* There's no pixel to the left of the first pixel. Luckily, it's
|
* predicted to be half of the pixel above it. So again, this works
|
* perfectly with our loop if we make sure a starts at zero.
|
*/
|
|
size_t rb;
|
|
const __m128i zero = _mm_setzero_si128();
|
|
__m128i b;
|
__m128i a, d = zero;
|
|
png_debug(1, "in png_read_filter_row_avg3_sse2");
|
rb = row_info->rowbytes;
|
while (rb >= 4) {
|
__m128i avg;
|
b = load4(prev);
|
a = d; d = load4(row );
|
|
/* PNG requires a truncating average, so we can't just use _mm_avg_epu8 */
|
avg = _mm_avg_epu8(a,b);
|
/* ...but we can fix it up by subtracting off 1 if it rounded up. */
|
avg = _mm_sub_epi8(avg, _mm_and_si128(_mm_xor_si128(a,b),
|
_mm_set1_epi8(1)));
|
d = _mm_add_epi8(d, avg);
|
store3(row, d);
|
|
prev += 3;
|
row += 3;
|
rb -= 3;
|
}
|
if (rb > 0) {
|
__m128i avg;
|
b = load3(prev);
|
a = d; d = load3(row );
|
|
/* PNG requires a truncating average, so we can't just use _mm_avg_epu8 */
|
avg = _mm_avg_epu8(a,b);
|
/* ...but we can fix it up by subtracting off 1 if it rounded up. */
|
avg = _mm_sub_epi8(avg, _mm_and_si128(_mm_xor_si128(a,b),
|
_mm_set1_epi8(1)));
|
|
d = _mm_add_epi8(d, avg);
|
store3(row, d);
|
|
prev += 3;
|
row += 3;
|
rb -= 3;
|
}
|
}
|
|
void png_read_filter_row_avg4_sse2(png_row_infop row_info, png_bytep row,
|
png_const_bytep prev)
|
{
|
/* The Avg filter predicts each pixel as the (truncated) average of a and b.
|
* There's no pixel to the left of the first pixel. Luckily, it's
|
* predicted to be half of the pixel above it. So again, this works
|
* perfectly with our loop if we make sure a starts at zero.
|
*/
|
size_t rb;
|
const __m128i zero = _mm_setzero_si128();
|
__m128i b;
|
__m128i a, d = zero;
|
|
png_debug(1, "in png_read_filter_row_avg4_sse2");
|
|
rb = row_info->rowbytes+4;
|
while (rb > 4) {
|
__m128i avg;
|
b = load4(prev);
|
a = d; d = load4(row );
|
|
/* PNG requires a truncating average, so we can't just use _mm_avg_epu8 */
|
avg = _mm_avg_epu8(a,b);
|
/* ...but we can fix it up by subtracting off 1 if it rounded up. */
|
avg = _mm_sub_epi8(avg, _mm_and_si128(_mm_xor_si128(a,b),
|
_mm_set1_epi8(1)));
|
|
d = _mm_add_epi8(d, avg);
|
store4(row, d);
|
|
prev += 4;
|
row += 4;
|
rb -= 4;
|
}
|
}
|
|
/* Returns |x| for 16-bit lanes. */
|
static __m128i abs_i16(__m128i x) {
|
#if PNG_INTEL_SSE_IMPLEMENTATION >= 2
|
return _mm_abs_epi16(x);
|
#else
|
/* Read this all as, return x<0 ? -x : x.
|
* To negate two's complement, you flip all the bits then add 1.
|
*/
|
__m128i is_negative = _mm_cmplt_epi16(x, _mm_setzero_si128());
|
|
/* Flip negative lanes. */
|
x = _mm_xor_si128(x, is_negative);
|
|
/* +1 to negative lanes, else +0. */
|
x = _mm_sub_epi16(x, is_negative);
|
return x;
|
#endif
|
}
|
|
/* Bytewise c ? t : e. */
|
static __m128i if_then_else(__m128i c, __m128i t, __m128i e) {
|
#if PNG_INTEL_SSE_IMPLEMENTATION >= 3
|
return _mm_blendv_epi8(e,t,c);
|
#else
|
return _mm_or_si128(_mm_and_si128(c, t), _mm_andnot_si128(c, e));
|
#endif
|
}
|
|
void png_read_filter_row_paeth3_sse2(png_row_infop row_info, png_bytep row,
|
png_const_bytep prev)
|
{
|
/* Paeth tries to predict pixel d using the pixel to the left of it, a,
|
* and two pixels from the previous row, b and c:
|
* prev: c b
|
* row: a d
|
* The Paeth function predicts d to be whichever of a, b, or c is nearest to
|
* p=a+b-c.
|
*
|
* The first pixel has no left context, and so uses an Up filter, p = b.
|
* This works naturally with our main loop's p = a+b-c if we force a and c
|
* to zero.
|
* Here we zero b and d, which become c and a respectively at the start of
|
* the loop.
|
*/
|
size_t rb;
|
const __m128i zero = _mm_setzero_si128();
|
__m128i c, b = zero,
|
a, d = zero;
|
|
png_debug(1, "in png_read_filter_row_paeth3_sse2");
|
|
rb = row_info->rowbytes;
|
while (rb >= 4) {
|
/* It's easiest to do this math (particularly, deal with pc) with 16-bit
|
* intermediates.
|
*/
|
__m128i pa,pb,pc,smallest,nearest;
|
c = b; b = _mm_unpacklo_epi8(load4(prev), zero);
|
a = d; d = _mm_unpacklo_epi8(load4(row ), zero);
|
|
/* (p-a) == (a+b-c - a) == (b-c) */
|
|
pa = _mm_sub_epi16(b,c);
|
|
/* (p-b) == (a+b-c - b) == (a-c) */
|
pb = _mm_sub_epi16(a,c);
|
|
/* (p-c) == (a+b-c - c) == (a+b-c-c) == (b-c)+(a-c) */
|
pc = _mm_add_epi16(pa,pb);
|
|
pa = abs_i16(pa); /* |p-a| */
|
pb = abs_i16(pb); /* |p-b| */
|
pc = abs_i16(pc); /* |p-c| */
|
|
smallest = _mm_min_epi16(pc, _mm_min_epi16(pa, pb));
|
|
/* Paeth breaks ties favoring a over b over c. */
|
nearest = if_then_else(_mm_cmpeq_epi16(smallest, pa), a,
|
if_then_else(_mm_cmpeq_epi16(smallest, pb), b,
|
c));
|
|
/* Note `_epi8`: we need addition to wrap modulo 255. */
|
d = _mm_add_epi8(d, nearest);
|
store3(row, _mm_packus_epi16(d,d));
|
|
prev += 3;
|
row += 3;
|
rb -= 3;
|
}
|
if (rb > 0) {
|
/* It's easiest to do this math (particularly, deal with pc) with 16-bit
|
* intermediates.
|
*/
|
__m128i pa,pb,pc,smallest,nearest;
|
c = b; b = _mm_unpacklo_epi8(load3(prev), zero);
|
a = d; d = _mm_unpacklo_epi8(load3(row ), zero);
|
|
/* (p-a) == (a+b-c - a) == (b-c) */
|
pa = _mm_sub_epi16(b,c);
|
|
/* (p-b) == (a+b-c - b) == (a-c) */
|
pb = _mm_sub_epi16(a,c);
|
|
/* (p-c) == (a+b-c - c) == (a+b-c-c) == (b-c)+(a-c) */
|
pc = _mm_add_epi16(pa,pb);
|
|
pa = abs_i16(pa); /* |p-a| */
|
pb = abs_i16(pb); /* |p-b| */
|
pc = abs_i16(pc); /* |p-c| */
|
|
smallest = _mm_min_epi16(pc, _mm_min_epi16(pa, pb));
|
|
/* Paeth breaks ties favoring a over b over c. */
|
nearest = if_then_else(_mm_cmpeq_epi16(smallest, pa), a,
|
if_then_else(_mm_cmpeq_epi16(smallest, pb), b,
|
c));
|
|
/* Note `_epi8`: we need addition to wrap modulo 255. */
|
d = _mm_add_epi8(d, nearest);
|
store3(row, _mm_packus_epi16(d,d));
|
|
prev += 3;
|
row += 3;
|
rb -= 3;
|
}
|
}
|
|
void png_read_filter_row_paeth4_sse2(png_row_infop row_info, png_bytep row,
|
png_const_bytep prev)
|
{
|
/* Paeth tries to predict pixel d using the pixel to the left of it, a,
|
* and two pixels from the previous row, b and c:
|
* prev: c b
|
* row: a d
|
* The Paeth function predicts d to be whichever of a, b, or c is nearest to
|
* p=a+b-c.
|
*
|
* The first pixel has no left context, and so uses an Up filter, p = b.
|
* This works naturally with our main loop's p = a+b-c if we force a and c
|
* to zero.
|
* Here we zero b and d, which become c and a respectively at the start of
|
* the loop.
|
*/
|
size_t rb;
|
const __m128i zero = _mm_setzero_si128();
|
__m128i pa,pb,pc,smallest,nearest;
|
__m128i c, b = zero,
|
a, d = zero;
|
|
png_debug(1, "in png_read_filter_row_paeth4_sse2");
|
|
rb = row_info->rowbytes+4;
|
while (rb > 4) {
|
/* It's easiest to do this math (particularly, deal with pc) with 16-bit
|
* intermediates.
|
*/
|
c = b; b = _mm_unpacklo_epi8(load4(prev), zero);
|
a = d; d = _mm_unpacklo_epi8(load4(row ), zero);
|
|
/* (p-a) == (a+b-c - a) == (b-c) */
|
pa = _mm_sub_epi16(b,c);
|
|
/* (p-b) == (a+b-c - b) == (a-c) */
|
pb = _mm_sub_epi16(a,c);
|
|
/* (p-c) == (a+b-c - c) == (a+b-c-c) == (b-c)+(a-c) */
|
pc = _mm_add_epi16(pa,pb);
|
|
pa = abs_i16(pa); /* |p-a| */
|
pb = abs_i16(pb); /* |p-b| */
|
pc = abs_i16(pc); /* |p-c| */
|
|
smallest = _mm_min_epi16(pc, _mm_min_epi16(pa, pb));
|
|
/* Paeth breaks ties favoring a over b over c. */
|
nearest = if_then_else(_mm_cmpeq_epi16(smallest, pa), a,
|
if_then_else(_mm_cmpeq_epi16(smallest, pb), b,
|
c));
|
|
/* Note `_epi8`: we need addition to wrap modulo 255. */
|
d = _mm_add_epi8(d, nearest);
|
store4(row, _mm_packus_epi16(d,d));
|
|
prev += 4;
|
row += 4;
|
rb -= 4;
|
}
|
}
|
|
#endif /* PNG_INTEL_SSE_IMPLEMENTATION > 0 */
|
#endif /* READ */
|
