[src/trunk]: src/common/lib/libc/hash/murmurhash murmurhash2: add an optimise...

[rmind <rmind%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/25211182b50d
branches:  trunk
changeset: 790920:25211182b50d
user:      rmind <rmind%NetBSD.org@localhost>
date:      Sat Oct 26 21:06:38 2013 +0000

description:
murmurhash2: add an optimised path for the aligned pointer case.

diffstat:

 common/lib/libc/hash/murmurhash/murmurhash.c |  49 ++++++++++++++++++---------
 1 files changed, 33 insertions(+), 16 deletions(-)

diffs (84 lines):

diff -r 4356846ab804 -r 25211182b50d common/lib/libc/hash/murmurhash/murmurhash.c
--- a/common/lib/libc/hash/murmurhash/murmurhash.c      Sat Oct 26 20:31:23 2013 +0000
+++ b/common/lib/libc/hash/murmurhash/murmurhash.c      Sat Oct 26 21:06:38 2013 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: murmurhash.c,v 1.5 2013/06/30 12:20:32 rmind Exp $     */
+/*     $NetBSD: murmurhash.c,v 1.6 2013/10/26 21:06:38 rmind Exp $     */
 
 /*
  * MurmurHash2 -- from the original code:
@@ -14,18 +14,19 @@
 #include <sys/cdefs.h>
 
 #if defined(_KERNEL) || defined(_STANDALONE)
-__KERNEL_RCSID(0, "$NetBSD: murmurhash.c,v 1.5 2013/06/30 12:20:32 rmind Exp $");
+__KERNEL_RCSID(0, "$NetBSD: murmurhash.c,v 1.6 2013/10/26 21:06:38 rmind Exp $");
 
 #else
 
 #if defined(LIBC_SCCS) && !defined(lint)
-__RCSID("$NetBSD: murmurhash.c,v 1.5 2013/06/30 12:20:32 rmind Exp $");
+__RCSID("$NetBSD: murmurhash.c,v 1.6 2013/10/26 21:06:38 rmind Exp $");
 #endif /* LIBC_SCCS and not lint */
 
 #include "namespace.h"
 #endif
 
 #include <sys/types.h>
+#include <sys/param.h>
 #include <sys/hash.h>
 
 #if !defined(_KERNEL) && !defined(_STANDALONE)
@@ -48,23 +49,39 @@
        const uint8_t *data = key;
        uint32_t h = seed ^ (uint32_t)len;
 
-       while (len >= sizeof(uint32_t)) {
-               uint32_t k;
+       if (__predict_true(ALIGNED_POINTER(key, uint32_t))) {
+               while (len >= sizeof(uint32_t)) {
+                       uint32_t k = *(const uint32_t *)data;
 
-               k  = data[0];
-               k |= data[1] << 8;
-               k |= data[2] << 16;
-               k |= data[3] << 24;
+                       k *= m;
+                       k ^= k >> r;
+                       k *= m;
+
+                       h *= m;
+                       h ^= k;
 
-               k *= m;
-               k ^= k >> r;
-               k *= m;
+                       data += sizeof(uint32_t);
+                       len -= sizeof(uint32_t);
+               }
+       } else {
+               while (len >= sizeof(uint32_t)) {
+                       uint32_t k;
 
-               h *= m;
-               h ^= k;
+                       k  = data[0];
+                       k |= data[1] << 8;
+                       k |= data[2] << 16;
+                       k |= data[3] << 24;
 
-               data += sizeof(uint32_t);
-               len -= sizeof(uint32_t);
+                       k *= m;
+                       k ^= k >> r;
+                       k *= m;
+
+                       h *= m;
+                       h ^= k;
+
+                       data += sizeof(uint32_t);
+                       len -= sizeof(uint32_t);
+               }
        }
 
        /* Handle the last few bytes of the input array. */