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sgidec: make compiler optimize away memcpy call in inner loop.

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Using an always_inline function makes the memcpy length a constant,
any reasonable compiler will replace it by a single mov instruction
without us having to duplicate the actual code.

Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>
This commit is contained in:
Reimar Döffinger 2012-01-08 12:19:48 +01:00
parent efd6b80b40
commit 4231bbbf4c
1 changed files with 25 additions and 13 deletions
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38
libavcodec/sgidec.c
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@ -20,6 +20,7 @@
*/
#include "libavutil/imgutils.h"
#include "libavutil/avassert.h"
#include "avcodec.h"
#include "bytestream.h"
#include "sgi.h"
@ -113,6 +114,25 @@ static int read_rle_sgi(unsigned char* out_buf, const uint8_t *in_buf,
return 0;
}
static av_always_inline void copy_loop(uint8_t *out_buf, const uint8_t *in_buf,
unsigned offset, unsigned bytes_per_channel,
SgiState *s)
{
int x, y, z;
for (y = s->height - 1; y >= 0; y--) {
uint8_t *line = out_buf + (y * s->linesize);
for (x = s->width; x > 0; x--) {
const uint8_t *ptr = in_buf;
in_buf += bytes_per_channel;
for(z = 0; z < s->depth; z ++) {
memcpy(line, ptr, bytes_per_channel);
line += bytes_per_channel;
ptr += offset;
}
}
}
}
/**
* Read an uncompressed SGI image.
* @param out_buf output buffer
@ -125,8 +145,6 @@ static int read_rle_sgi(unsigned char* out_buf, const uint8_t *in_buf,
static int read_uncompressed_sgi(unsigned char* out_buf, uint8_t* out_end,
const uint8_t *in_buf, const uint8_t *in_end, SgiState* s)
{
int x, y, z;
const uint8_t *ptr;
unsigned int offset = s->height * s->width * s->bytes_per_channel;
/* Test buffer size. */
@ -134,17 +152,11 @@ static int read_uncompressed_sgi(unsigned char* out_buf, uint8_t* out_end,
return -1;
}
for (y = s->height - 1; y >= 0; y--) {
out_end = out_buf + (y * s->linesize);
for (x = s->width; x > 0; x--) {
ptr = in_buf;
in_buf += s->bytes_per_channel;
for(z = 0; z < s->depth; z ++) {
memcpy(out_end, ptr, s->bytes_per_channel);
out_end += s->bytes_per_channel;
ptr += offset;
}
}
if (s->bytes_per_channel == 2) {
copy_loop(out_buf, in_buf, offset, 2, s);
} else {
av_assert1(s->bytes_per_channel == 1);
copy_loop(out_buf, in_buf, offset, 1, s);
}
return 0;
}