Messages in this thread Patch in this message | | | Date | Wed, 31 Aug 2011 17:30:06 -0500 | From | Bob Pearson <> | Subject | [PATCH v6 04/10] crc32-add-pointer-to-tab.diff |
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Replace 2D array references by pointer references in loops. This change has no effect on X86 code but improves PPC performance.
Signed-off-by: Bob Pearson <rpearson@systemfabricworks.com>
--- lib/crc32.c | 21 +++++++++++---------- 1 file changed, 11 insertions(+), 10 deletions(-)
Index: for-next/lib/crc32.c =================================================================== --- for-next.orig/lib/crc32.c +++ for-next/lib/crc32.c @@ -53,20 +53,21 @@ 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 = tab[0][(crc ^ (x)) & 255] ^ (crc >> 8) -# define DO_CRC4 crc = tab[3][(crc) & 255] ^ \ - tab[2][(crc >> 8) & 255] ^ \ - tab[1][(crc >> 16) & 255] ^ \ - tab[0][(crc >> 24) & 255] +# 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] # else -# define DO_CRC(x) crc = tab[0][((crc >> 24) ^ (x)) & 255] ^ (crc << 8) -# define DO_CRC4 crc = tab[0][(crc) & 255] ^ \ - tab[1][(crc >> 8) & 255] ^ \ - tab[2][(crc >> 16) & 255] ^ \ - tab[3][(crc >> 24) & 255] +# 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] # endif const u32 *b; size_t rem_len; + const u32 *t0 = tab[0], *t1 = tab[1], *t2 = tab[2], *t3 = tab[3]; /* Align it */ if (unlikely((long)buf & 3 && len)) {
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