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gtkcairoblur: Unroll inner loop for common radius values

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This unrolls the inner blur loop for radius 1-10, allowing
the compiler to use a divide-by-constant operation instead
of a generic division.

Here is the blur-performance output before:

Radius  1: 124.95 msec, 32.01 kpixels/msec:
Radius  2: 117.27 msec, 34.11 kpixels/msec:
Radius  3: 123.57 msec, 32.37 kpixels/msec:
Radius  4: 118.17 msec, 33.85 kpixels/msec:
Radius  5: 119.32 msec, 33.52 kpixels/msec:
Radius  6: 124.17 msec, 32.21 kpixels/msec:
Radius  7: 121.04 msec, 33.05 kpixels/msec:
Radius  8: 130.64 msec, 30.62 kpixels/msec:
Radius  9: 119.47 msec, 33.48 kpixels/msec:
Radius 10: 117.95 msec, 33.91 kpixels/msec:
Radius 11: 122.38 msec, 32.68 kpixels/msec:
Radius 12: 121.92 msec, 32.81 kpixels/msec:
Radius 13: 125.45 msec, 31.89 kpixels/msec:
Radius 14: 121.63 msec, 32.89 kpixels/msec:
Radius 15: 120.18 msec, 33.28 kpixels/msec:

And after:

Radius  1: 42.26 msec, 94.65 kpixels/msec:
Radius  2: 59.15 msec, 67.62 kpixels/msec:
Radius  3: 60.29 msec, 66.35 kpixels/msec:
Radius  4: 64.53 msec, 61.99 kpixels/msec:
Radius  5: 60.07 msec, 66.59 kpixels/msec:
Radius  6: 62.43 msec, 64.07 kpixels/msec:
Radius  7: 60.36 msec, 66.27 kpixels/msec:
Radius  8: 59.59 msec, 67.13 kpixels/msec:
Radius  9: 76.17 msec, 52.51 kpixels/msec:
Radius 10: 79.41 msec, 50.37 kpixels/msec:
Radius 11: 118.92 msec, 33.64 kpixels/msec:
Radius 12: 121.31 msec, 32.97 kpixels/msec:
Radius 13: 118.30 msec, 33.81 kpixels/msec:
Radius 14: 116.82 msec, 34.24 kpixels/msec:
Radius 15: 116.99 msec, 34.19 kpixels/msec:

I.e. almost double performance for the unrolled radius values.

https://bugzilla.gnome.org/show_bug.cgi?id=746468
This commit is contained in:
Alexander Larsson 2015-03-19 16:29:32 +01:00
parent ae21e08782
commit d0dc1f52cc
1 changed files with 30 additions and 11 deletions
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41
gtk/gtkcairoblur.c
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@ -73,18 +73,37 @@ blur_xspan (guchar *row,
* only divide down after all three passes. (SSE parallel implementation
* of the divide step is possible.)
*/
for (i = -d + offset; i < row_width + offset; i++)
#define BLUR_ROW_KERNEL(D) \
for (i = -(D) + offset; i < row_width + offset; i++) \
{ \
if (i >= 0 && i < row_width) \
sum += row[i]; \
\
if (i >= offset) \
{ \
if (i >= (D)) \
sum -= row[i - (D)]; \
\
tmp_buffer[i - offset] = (sum + (D) / 2) / (D); \
} \
} \
break;
/* We unroll the values for d for radius 2-10 to avoid a generic
* divide operation (not radius 1, because its a no-op) */
switch (d)
{
if (i >= 0 && i < row_width)
sum += row[i];
if (i >= offset)
{
if (i >= d)
sum -= row[i - d];
tmp_buffer[i - offset] = (sum + d / 2) / d;
}
case get_box_filter_size (2): BLUR_ROW_KERNEL (get_box_filter_size (2));
case get_box_filter_size (3): BLUR_ROW_KERNEL (get_box_filter_size (3));
case get_box_filter_size (4): BLUR_ROW_KERNEL (get_box_filter_size (4));
case get_box_filter_size (5): BLUR_ROW_KERNEL (get_box_filter_size (5));
case get_box_filter_size (6): BLUR_ROW_KERNEL (get_box_filter_size (6));
case get_box_filter_size (7): BLUR_ROW_KERNEL (get_box_filter_size (7));
case get_box_filter_size (8): BLUR_ROW_KERNEL (get_box_filter_size (8));
case get_box_filter_size (9): BLUR_ROW_KERNEL (get_box_filter_size (9));
case get_box_filter_size (10): BLUR_ROW_KERNEL (get_box_filter_size (10));
default: BLUR_ROW_KERNEL (d);
}
memcpy (row, tmp_buffer, row_width);