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[sfnt] Speed up PNG image loading. 

This reduces the overhead of `premultiply_data' by 60%.

* src/sfnt/pngshim.c (premultiply_data): Provide code which uses
gcc's (and clang's) `vector_byte' attribute to process 4 pixels at a
time.
This commit is contained in:
Behdad Esfahbod 2017-08-15 08:48:17 +02:00 committed by Werner Lemberg
parent f53ccf6f8f
commit c9d7c03fa1
2 changed files with 60 additions and 3 deletions
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10
ChangeLog
View File

@ -1,3 +1,13 @@
2017-08-15 Behdad Esfahbod <behdad@behdad.org>
[sfnt] Speed up PNG image loading.
This reduces the overhead of `premultiply_data' by 60%.
* src/sfnt/pngshim.c (premultiply_data): Provide code which uses
gcc's (and clang's) `vector_byte' attribute to process 4 pixels at a
time.
2017-08-11 Werner Lemberg <wl@gnu.org>
[sfnt, truetype] Improve handling of missing sbits.

53
src/sfnt/pngshim.c
View File

@ -49,18 +49,65 @@
}
/* Premultiplies data and converts RGBA bytes => native endian. */
/* Premultiplies data and converts RGBA bytes => BGRA. */
static void
premultiply_data( png_structp png,
png_row_infop row_info,
png_bytep data )
{
unsigned int i;
unsigned int i = 0, limit;
FT_UNUSED( png );
/* the `vector_size' attribute was introduced in gcc 3.1, which */
/* predates clang; the `__BYTE_ORDER__' preprocessor symbol was */
/* introduced in gcc 4.6 and clang 3.2, respectively */
#if ( ( defined( __GNUC__ ) && \
( ( __GNUC__ >= 5 ) || \
( ( __GNUC__ == 4 ) && ( __GNUC_MINOR__ >= 6 ) ) ) ) || \
( defined( __clang__ ) && \
( ( __clang_major__ >= 4 ) || \
( ( __clang_major__ == 3 ) && ( __clang_minor__ >= 2 ) ) ) ) ) && \
defined( __OPTIMIZE__ ) && \
__BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
for ( i = 0; i < row_info->rowbytes; i += 4 )
typedef unsigned short v82 __attribute__(( vector_size( 16 ) ));
/* process blocks of 16 bytes in one rush, which gives a nice speed-up */
limit = row_info->rowbytes - 16 + 1;
for ( ; i < limit; i += 16 )
{
char* base = &data[i];
v82 s, s0, s1, a;
v82 ma = { 1, 1, 3, 3, 5, 5, 7, 7 };
v82 o1 = { 0, 0xFF, 0, 0xFF, 0, 0xFF, 0, 0xFF };
v82 m0 = { 1, 0, 3, 2, 5, 4, 7, 6 };
memcpy( &s, base, 16 ); /* RGBA RGBA RGBA RGBA */
s0 = s & 0xFF; /* R B R B R B R B */
s1 = s >> 8; /* G A G A G A G A */
a = __builtin_shuffle( s1, ma ); /* A A A A A A A A */
s1 |= o1; /* G 1 G 1 G 1 G 1 */
s0 = __builtin_shuffle( s0, m0 ); /* B R B R B R B R */
s0 *= a;
s1 *= a;
s0 += 0x80;
s1 += 0x80;
s0 = ( s0 + ( s0 >> 8 ) ) >> 8;
s1 = ( s1 + ( s1 >> 8 ) ) >> 8;
s = s0 | ( s1 << 8 );
memcpy( base, &s, 16 );
}
#endif /* use `vector_size' */
limit = row_info->rowbytes;
for ( ; i < limit; i += 4 )
{
unsigned char* base = &data[i];
unsigned int alpha = base[3];