From 5742332dea5560d6c449b007d9539dbdc8ee531b Mon Sep 17 00:00:00 2001 From: Joakim Tjernlund Date: Tue, 10 Jan 2012 15:10:18 -0800 Subject: crc32: optimize inner loop Taking a pointer reference to each row in the crc table matrix, one can reduce the inner loop with a few insn's Signed-off-by: Joakim Tjernlund Cc: Bob Pearson Cc: Frank Zago Cc: Eric Dumazet Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- lib/crc32.c | 21 +++++++++++---------- 1 file changed, 11 insertions(+), 10 deletions(-) (limited to 'lib') diff --git a/lib/crc32.c b/lib/crc32.c index a6e633a48ce..4b35d2b4437 100644 --- a/lib/crc32.c +++ b/lib/crc32.c @@ -51,20 +51,21 @@ 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)) { -- cgit v1.2.3