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lavfi/nlmeans: add SIMD-friendly assumptions for compute_safe_ssd_integral_image 

SIMD code will not have to deal with padding itself. Overwriting in that
function may have been possible but involve large overreading of the
sources. Instead, we simply make sure the width to process is always a
multiple of 16. Additionally, there must be some actual area to process
so the SIMD code can have its boundary checks after processing the first
pixels.
This commit is contained in:
Clément Bœsch 2018-05-06 10:38:30 +02:00
parent f1248b7795
commit 26f02c51ce
1 changed files with 18 additions and 7 deletions
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25
libavfilter/vf_nlmeans.c
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@ -157,6 +157,9 @@ static void compute_safe_ssd_integral_image_c(uint32_t *dst, int dst_linesize_32
{
int x, y;
/* SIMD-friendly assumptions allowed here */
av_assert2(!(w & 0xf) && w >= 16 && h >= 1);
for (y = 0; y < h; y++) {
uint32_t acc = dst[-1] - dst[-dst_linesize_32 - 1];
@ -257,9 +260,16 @@ static void compute_ssd_integral_image(uint32_t *ii, int ii_linesize_32,
// to compare the 2 sources pixels
const int startx_safe = FFMAX(s1x, s2x);
const int starty_safe = FFMAX(s1y, s2y);
const int endx_safe = FFMIN(s1x + w, s2x + w);
const int u_endx_safe = FFMIN(s1x + w, s2x + w); // unaligned
const int endy_safe = FFMIN(s1y + h, s2y + h);
// deduce the safe area width and height
const int safe_pw = (u_endx_safe - startx_safe) & ~0xf;
const int safe_ph = endy_safe - starty_safe;
// adjusted end x position of the safe area after width of the safe area gets aligned
const int endx_safe = startx_safe + safe_pw;
// top part where only one of s1 and s2 is still readable, or none at all
compute_unsafe_ssd_integral_image(ii, ii_linesize_32,
0, 0,
@ -273,24 +283,25 @@ static void compute_ssd_integral_image(uint32_t *ii, int ii_linesize_32,
0, starty_safe,
src, linesize,
offx, offy, e, w, h,
startx_safe, endy_safe - starty_safe);
startx_safe, safe_ph);
// main and safe part of the integral
av_assert1(startx_safe - s1x >= 0); av_assert1(startx_safe - s1x < w);
av_assert1(starty_safe - s1y >= 0); av_assert1(starty_safe - s1y < h);
av_assert1(startx_safe - s2x >= 0); av_assert1(startx_safe - s2x < w);
av_assert1(starty_safe - s2y >= 0); av_assert1(starty_safe - s2y < h);
compute_safe_ssd_integral_image_c(ii + starty_safe*ii_linesize_32 + startx_safe, ii_linesize_32,
src + (starty_safe - s1y) * linesize + (startx_safe - s1x), linesize,
src + (starty_safe - s2y) * linesize + (startx_safe - s2x), linesize,
endx_safe - startx_safe, endy_safe - starty_safe);
if (safe_pw && safe_ph)
compute_safe_ssd_integral_image_c(ii + starty_safe*ii_linesize_32 + startx_safe, ii_linesize_32,
src + (starty_safe - s1y) * linesize + (startx_safe - s1x), linesize,
src + (starty_safe - s2y) * linesize + (startx_safe - s2x), linesize,
safe_pw, safe_ph);
// right part of the integral
compute_unsafe_ssd_integral_image(ii, ii_linesize_32,
endx_safe, starty_safe,
src, linesize,
offx, offy, e, w, h,
ii_w - endx_safe, endy_safe - starty_safe);
ii_w - endx_safe, safe_ph);
// bottom part where only one of s1 and s2 is still readable, or none at all
compute_unsafe_ssd_integral_image(ii, ii_linesize_32,