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Do the clipping with inline asm instead of a huge lookup table. Tiny speedup, and saves ~7.5KB of IRAM.

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git-svn-id: svn://svn.rockbox.org/rockbox/trunk@10493 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Jens Arnold 2006-08-08 22:56:35 +00:00
parent e559cdb916
commit b888fb2531
1 changed files with 28 additions and 0 deletions
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28
apps/plugins/mpegplayer/idct.c
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@ -47,8 +47,34 @@ void (* mpeg2_idct_add) (int last, int16_t * block,
* to +-3826 - this is the worst case for a column IDCT where the * to +-3826 - this is the worst case for a column IDCT where the
* column inputs are 16-bit values. * column inputs are 16-bit values.
*/ */
#ifdef CPU_COLDFIRE
static inline unsigned CLIP(int value)
{
asm ( /* Note: Uses knowledge that only the low byte of the result is used */
"cmp.l #255,%[v] \n" /* overflow? */
"bls.b 1f \n" /* no: return value */
"spl.b %[v] \n" /* yes: set low byte to appropriate boundary */
"1: \n"
: /* outputs */
[v]"+d"(value)
);
return value;
}
#elif defined CPU_ARM
static inline unsigned CLIP(int value)
{
asm ( /* Note: Uses knowledge that only the low byte of the result is used */
"cmp %[v], #255 \n"
"mvnhi %[v], %[v], asr #31 \n"
: /* outputs */
[v]"+r"(value)
);
return value;
}
#else
uint8_t mpeg2_clip[3840 * 2 + 256] IBSS_ATTR; uint8_t mpeg2_clip[3840 * 2 + 256] IBSS_ATTR;
#define CLIP(i) ((mpeg2_clip + 3840)[i]) #define CLIP(i) ((mpeg2_clip + 3840)[i])
#endif
#if 0 #if 0
#define BUTTERFLY(t0,t1,W0,W1,d0,d1) \ #define BUTTERFLY(t0,t1,W0,W1,d0,d1) \
@ -275,8 +301,10 @@ void mpeg2_idct_init (uint32_t accel)
mpeg2_idct_copy = mpeg2_idct_copy_c; mpeg2_idct_copy = mpeg2_idct_copy_c;
mpeg2_idct_add = mpeg2_idct_add_c; mpeg2_idct_add = mpeg2_idct_add_c;
#if !defined(CPU_COLDFIRE) && !defined(CPU_ARM)
for (i = -3840; i < 3840 + 256; i++) for (i = -3840; i < 3840 + 256; i++)
CLIP(i) = (i < 0) ? 0 : ((i > 255) ? 255 : i); CLIP(i) = (i < 0) ? 0 : ((i > 255) ? 255 : i);
#endif
for (i = 0; i < 64; i++) { for (i = 0; i < 64; i++) {
j = mpeg2_scan_norm[i]; j = mpeg2_scan_norm[i];
mpeg2_scan_norm[i] = ((j & 0x36) >> 1) | ((j & 0x09) << 2); mpeg2_scan_norm[i] = ((j & 0x36) >> 1) | ((j & 0x09) << 2);