Small optimization of generic ELF hash function

diff --git a/ChangeLog b/ChangeLog
index 0dfff5c..f4b3460 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,6 +1,7 @@
 2011-12-04  Ulrich Drepper  <drepper@gmail.com>
 
        * sysdeps/generic/dl-hash.h (_dl_elf_hash): Fix attribute.
+       Minor optimizations.
 
        * sunrpc/clnt_unix.c (clntunix_control): Fix aliasing issues.
        * sunrpc/clnt_tcp.c (clnttcp_control): Likewise.

diff --git a/sysdeps/generic/dl-hash.h b/sysdeps/generic/dl-hash.h
index e35bd25..28312ca 100644 (file)
--- a/sysdeps/generic/dl-hash.h
+++ b/sysdeps/generic/dl-hash.h
@@ -29,42 +29,39 @@ __attribute__ ((unused))
 _dl_elf_hash (const char *name_arg)
 {
   const unsigned char *name = (const unsigned char *) name_arg;
-  unsigned long int hash = 0;
-  if (*name != '\0')
+  unsigned long int hash = *name;
+  if (hash != 0 && name[1] != '\0')
     {
-      hash = *name++;
-      if (*name != '\0')
+      hash = (hash << 4) + name[1];
+      if (name[2] != '\0')
        {
-         hash = (hash << 4) + *name++;
-         if (*name != '\0')
+         hash = (hash << 4) + name[2];
+         if (name[3] != '\0')
            {
-             hash = (hash << 4) + *name++;
-             if (*name != '\0')
+             hash = (hash << 4) + name[3];
+             if (name[4] != '\0')
                {
-                 hash = (hash << 4) + *name++;
-                 if (*name != '\0')
+                 hash = (hash << 4) + name[4];
+                 name += 5;
+                 while (*name != '\0')
                    {
+                     unsigned long int hi;
                      hash = (hash << 4) + *name++;
-                     while (*name != '\0')
-                       {
-                         unsigned long int hi;
-                         hash = (hash << 4) + *name++;
-                         hi = hash & 0xf0000000;
+                     hi = hash & 0xf0000000;
 
-                         /* The algorithm specified in the ELF ABI is as
-                            follows:
+                     /* The algorithm specified in the ELF ABI is as
+                        follows:
 
-                            if (hi != 0)
-                              hash ^= hi >> 24;
+                        if (hi != 0)
+                          hash ^= hi >> 24;
 
-                            hash &= ~hi;
+                        hash &= ~hi;
 
-                            But the following is equivalent and a lot
-                            faster, especially on modern processors.  */
+                        But the following is equivalent and a lot
+                        faster, especially on modern processors.  */
 
-                         hash ^= hi;
-                         hash ^= hi >> 24;
-                       }
+                     hash ^= hi;
+                     hash ^= hi >> 24;
                    }
                }
            }