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| author | Joakim Tjernlund <Joakim.Tjernlund@transmode.se> | 2012-01-10 15:10:18 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-01-10 16:30:51 -0800 |
| commit | 5742332dea5560d6c449b007d9539dbdc8ee531b (patch) | |
| tree | 64f4516b733638c966d6e66613e6ae016839d3f2 /lib/crc32.c | |
| parent | bfcb2cc798a14230d22b6dd999e2e680623de622 (diff) | |
| download | lwn-5742332dea5560d6c449b007d9539dbdc8ee531b.tar.gz lwn-5742332dea5560d6c449b007d9539dbdc8ee531b.zip | |
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 <Joakim.Tjernlund@transmode.se>
Cc: Bob Pearson <rpearson@systemfabricworks.com>
Cc: Frank Zago <fzago@systemfabricworks.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'lib/crc32.c')
| -rw-r--r-- | lib/crc32.c | 21 |
1 files changed, 11 insertions, 10 deletions
diff --git a/lib/crc32.c b/lib/crc32.c index a6e633a48cea..4b35d2b4437c 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)) { |