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Subject[PATCH] crc32: Optimize inner loop.
Date
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>
---

As the slice by 8 CRC32 optimizations seems stalled, I figured
I send in this generic one.

lib/crc32.c | 21 +++++++++++----------
1 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/lib/crc32.c b/lib/crc32.c
index 4855995..b06d1e7 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)) {
--
1.7.3.4


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