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Improved bitrev with approach suggested by Jens Arnold, gives 0.5%-1% speedup for tremor decoding on sansa c200 (PP) and a tiny speedup on coldfire as well

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git-svn-id: svn://svn.rockbox.org/rockbox/trunk@24102 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Nils Wallménius 2009-12-23 18:05:11 +00:00
parent 92eb0c1841
commit 87ecc7020e
1 changed files with 25 additions and 5 deletions
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30
apps/codecs/libtremor/codebook.c
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@ -140,11 +140,31 @@ int vorbis_staticbook_unpack(oggpack_buffer *opb,static_codebook *s){
be. The first-stage decode table catches most words so that be. The first-stage decode table catches most words so that
bitreverse is not in the main execution path. */ bitreverse is not in the main execution path. */
static inline ogg_uint32_t bitreverse(register ogg_uint32_t x){ static inline ogg_uint32_t bitreverse(register ogg_uint32_t x)
x= swap32(x); {
x= ((x>> 4)&0x0f0f0f0f) | ((x<< 4)&0xf0f0f0f0); unsigned int mask;
x= ((x>> 2)&0x33333333) | ((x<< 2)&0xcccccccc); #if defined(CPU_ARM) && ARM_ARCH >= 6
return((x>> 1)&0x55555555) | ((x<< 1)&0xaaaaaaaa); asm ("rev %[x], %[x]" : [x] "+r" (x)); /* swap bytes */
#else
#if defined(CPU_COLDFIRE)
asm ("swap %[x]" : [x] "+r" (x)); /* swap halfwords */
#else
x = (x>>16) | (x<<16);
#endif
mask = x&0x00ff00ff;
x ^= mask;
x = (x >> 8) | (mask << 8); /* bytes swapped */
#endif
mask = x&0x0f0f0f0f;
x ^= mask;
x = (x >> 4) | (mask << 4); /* 4-bit units swapped */
mask = x&0x33333333;
x ^= mask;
x = (x >> 2) | (mask << 2); /* 2-bit units swapped */
mask = x&0x55555555;
x ^= mask;
x = (x >> 1) | (mask << 1); /* done */
return x;
} }
STIN long decode_packed_entry_number(codebook *book, STIN long decode_packed_entry_number(codebook *book,