Commit c9d7c03fa1b5c6244759ade814c546da04080646
2017-08-15T08:48:17
[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.
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diff --git a/ChangeLog b/ChangeLog
index 4091498..06ea99e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -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.
diff --git a/src/sfnt/pngshim.c b/src/sfnt/pngshim.c
index b9b296e..90a5669 100644
--- a/src/sfnt/pngshim.c
+++ b/src/sfnt/pngshim.c
@@ -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];