Author: stefan2
Date: Thu May 16 16:15:28 2013
New Revision: 1483434
URL: http://svn.apache.org/r1483434
Log:
On machines that allow for unaligned access, speed up hash ops
with known key length at the expense of those where the key length
is unknown.
Background: Efficient hash functions computation is essential for
performance in many parts of SVN. Many of the frequently callers
them have already been changed to provide the key length in.
* subversion/libsvn_subr/hash.c
(hashfunc_compatible): use a slightly different but faster
formula when the CPU supports that
Modified:
subversion/trunk/subversion/libsvn_subr/hash.c
Modified: subversion/trunk/subversion/libsvn_subr/hash.c
URL:
http://svn.apache.org/viewvc/subversion/trunk/subversion/libsvn_subr/hash.c?rev=1483434&r1=1483433&r2=1483434&view=diff
==============================================================================
--- subversion/trunk/subversion/libsvn_subr/hash.c (original)
+++ subversion/trunk/subversion/libsvn_subr/hash.c Thu May 16 16:15:28 2013
@@ -600,37 +600,26 @@ hashfunc_compatible(const char *char_key
apr_ssize_t i;
if (*klen == APR_HASH_KEY_STRING)
- {
- for (p = key; ; p+=4)
- {
- unsigned int new_hash = hash * 33 * 33 * 33 * 33;
- if (!p[0]) break;
- new_hash += p[0] * 33 * 33 * 33;
- if (!p[1]) break;
- new_hash += p[1] * 33 * 33;
- if (!p[2]) break;
- new_hash += p[2] * 33;
- if (!p[3]) break;
- hash = new_hash + p[3];
- }
- for (; *p; p++)
- hash = hash * 33 + *p;
+ *klen = strlen(char_key);
- *klen = p - key;
+#if SVN_UNALIGNED_ACCESS_IS_OK
+ for (p = key, i = *klen; i >= 4; i-=4, p+=4)
+ {
+ hash = hash * 33 * 33 * 33 * 33
+ + *(apr_uint32_t *)p;
}
- else
+#else
+ for (p = key, i = *klen; i >= 4; i-=4, p+=4)
{
- for (p = key, i = *klen; i >= 4; i-=4, p+=4)
- {
- hash = hash * 33 * 33 * 33 * 33
- + p[0] * 33 * 33 * 33
- + p[1] * 33 * 33
- + p[2] * 33
- + p[3];
- }
- for (; i; i--, p++)
- hash = hash * 33 + *p;
+ hash = hash * 33 * 33 * 33 * 33
+ + p[0] * 33 * 33 * 33
+ + p[1] * 33 * 33
+ + p[2] * 33
+ + p[3];
}
+#endif
+ for (; i; i--, p++)
+ hash = hash * 33 + *p;
return hash;
}
