From: "Darrick J. Wong" Subject: [PATCH 04/14] crc32: Speed up memory table access on powerpc Date: Fri, 06 Jan 2012 21:51:09 -0800 Message-ID: <20120107055109.31315.85783.stgit@elm3c44.beaverton.ibm.com> References: <20120107055042.31315.63119.stgit@elm3c44.beaverton.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Cc: Theodore Tso , Joakim Tjernlund , Bob Pearson , linux-kernel , Andreas Dilger , linux-crypto , linux-fsdevel , Mingming Cao , linux-ext4@vger.kernel.org To: Andrew Morton , Herbert Xu , "Darrick J. Wong" Return-path: In-Reply-To: <20120107055042.31315.63119.stgit@elm3c44.beaverton.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org Replace 2D array references by pointer references in loops. This change has no effect on X86 code but improves PPC performance. From: Bob Pearson Signed-off-by: Bob Pearson [djwong@us.ibm.com: Minor changelog tweaks] Signed-off-by: Darrick J. Wong --- lib/crc32.c | 21 +++++++++++---------- 1 files changed, 11 insertions(+), 10 deletions(-) diff --git a/lib/crc32.c b/lib/crc32.c index 7a0e5a9..c93c9ae 100644 --- a/lib/crc32.c +++ b/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)) {