Update.

1998-12-25  Ulrich Drepper  <drepper@cygnus.com>

	* elf/dl-hash.h: Move to...
	* sysdeps/generic/dl-hash.h: ...here.  Correct parameter type (must
	be unsigned char).  Remove conditional from inner loop and rearrange
	binary operations (12-22% performance increase).
	* sysdeps/i386/i686/dl-hash.h: New file.  Yet 10% faster than
	optimized generic version.

1 files changed, 74 insertions, 0 deletions

diff --git a/sysdeps/generic/dl-hash.h b/sysdeps/generic/dl-hash.h
new file mode 100644
index 0000000000..fc17793324
--- /dev/null
+++ b/sysdeps/generic/dl-hash.h
@@ -0,0 +1,74 @@
+/* Compute hash alue for given string according to ELF standard.
+   Copyright (C) 1995, 1996, 1997, 1998 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Library General Public License as
+   published by the Free Software Foundation; either version 2 of the
+   License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Library General Public License for more details.
+
+   You should have received a copy of the GNU Library General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  If not,
+   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+   Boston, MA 02111-1307, USA.  */
+
+#ifndef _DL_HASH_H
+#define _DL_HASH_H	1
+
+
+/* This is the hashing function specified by the ELF ABI.  In the
+   first five operations no overflow is possible so we optimized it a
+   bit.  */
+static inline unsigned int
+_dl_elf_hash (const unsigned char *name)
+{
+  unsigned long int hash = 0;
+  if (*name != '\0')
+    {
+      hash = *name++;
+      if (*name != '\0')
+	{
+	  hash = (hash << 4) + *name++;
+	  if (*name != '\0')
+	    {
+	      hash = (hash << 4) + *name++;
+	      if (*name != '\0')
+		{
+		  hash = (hash << 4) + *name++;
+		  if (*name != '\0')
+		    {
+		      hash = (hash << 4) + *name++;
+		      while (*name != '\0')
+			{
+			  unsigned long int hi;
+			  hash = (hash << 4) + *name++;
+			  hi = hash & 0xf0000000;
+
+			  /* The algorithm specified in the ELF ABI is as
+			     follows:
+
+			     if (hi != 0)
+			       hash ^= hi >> 24;
+
+			     hash &= ~hi;
+
+			     But the following is equivalent and a lot
+			     faster, especially on modern processors.  */
+
+			  hash ^= hi;
+			  hash ^= hi >> 24;
+			}
+		    }
+		}
+	    }
+	}
+    }
+  return hash;
+}
+
+#endif /* dl-hash.h */