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crc32: add slice-by-8 algorithm to existing code

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Add slicing-by-8 algorithm to the existing slicing-by-4 algorithm.  This
consists of:

- extend largest BITS size from 32 to 64
- extend tables from tab[4][256] to up to tab[8][256]
- Add code for inner loop.

[djwong@us.ibm.com: Minor changelog tweaks]
Signed-off-by: Bob Pearson <rpearson@systemfabricworks.com>
Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Bob Pearson
2012-03-23 15:02:24 -07:00
committed by Linus Torvalds
parent 9a1dbf6a29
commit 324eb0f17d
3 changed files with 75 additions and 35 deletions
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38
lib/crc32.c
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@@ -47,25 +47,28 @@ MODULE_LICENSE("GPL");
#if CRC_LE_BITS > 8 || CRC_BE_BITS > 8
/* implements slicing-by-4 or slicing-by-8 algorithm */
static inline u32
crc32_body(u32 crc, unsigned char const *buf, size_t len, const u32 (*tab)[256])
{
# ifdef __LITTLE_ENDIAN
# define DO_CRC(x) crc = t0[(crc ^ (x)) & 255] ^ (crc >> 8)
# define DO_CRC4 crc = t3[(crc) & 255] ^ \
t2[(crc >> 8) & 255] ^ \
t1[(crc >> 16) & 255] ^ \
t0[(crc >> 24) & 255]
# define DO_CRC4 (t3[(q) & 255] ^ t2[(q >> 8) & 255] ^ \
t1[(q >> 16) & 255] ^ t0[(q >> 24) & 255])
# define DO_CRC8 (t7[(q) & 255] ^ t6[(q >> 8) & 255] ^ \
t5[(q >> 16) & 255] ^ t4[(q >> 24) & 255])
# else
# define DO_CRC(x) crc = t0[((crc >> 24) ^ (x)) & 255] ^ (crc << 8)
# define DO_CRC4 crc = t0[(crc) & 255] ^ \
t1[(crc >> 8) & 255] ^ \
t2[(crc >> 16) & 255] ^ \
t3[(crc >> 24) & 255]
# define DO_CRC4 (t0[(q) & 255] ^ t1[(q >> 8) & 255] ^ \
t2[(q >> 16) & 255] ^ t3[(q >> 24) & 255])
# define DO_CRC8 (t4[(q) & 255] ^ t5[(q >> 8) & 255] ^ \
t6[(q >> 16) & 255] ^ t7[(q >> 24) & 255])
# endif
const u32 *b;
size_t rem_len;
const u32 *t0=tab[0], *t1=tab[1], *t2=tab[2], *t3=tab[3];
const u32 *t4 = tab[4], *t5 = tab[5], *t6 = tab[6], *t7 = tab[7];
u32 q;
/* Align it */
if (unlikely((long)buf & 3 && len)) {
@@ -73,13 +76,25 @@ crc32_body(u32 crc, unsigned char const *buf, size_t len, const u32 (*tab)[256])
DO_CRC(*buf++);
} while ((--len) && ((long)buf)&3);
}
# if CRC_LE_BITS == 32
rem_len = len & 3;
/* load data 32 bits wide, xor data 32 bits wide. */
len = len >> 2;
# else
rem_len = len & 7;
len = len >> 3;
# endif
b = (const u32 *)buf;
for (--b; len; --len) {
crc ^= *++b; /* use pre increment for speed */
DO_CRC4;
q = crc ^ *++b; /* use pre increment for speed */
# if CRC_LE_BITS == 32
crc = DO_CRC4;
# else
crc = DO_CRC8;
q = *++b;
crc ^= DO_CRC4;
# endif
}
len = rem_len;
/* And the last few bytes */
@@ -92,6 +107,7 @@ crc32_body(u32 crc, unsigned char const *buf, size_t len, const u32 (*tab)[256])
return crc;
#undef DO_CRC
#undef DO_CRC4
#undef DO_CRC8
}
#endif