glibc/sysdeps/i386/i686/dl-hash.h
Ulrich Drepper 85f72e9c2a 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.
1998-12-26 09:30:54 +00:00

81 lines
2.3 KiB
C

/* Compute hash alue for given string according to ELF standard.
Copyright (C) 1998 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.
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. It is highly
optimized for the PII processors. Though it will run on i586 it
would be much slower than the generic C implementation. So don't
use it. */
static inline unsigned int
_dl_elf_hash (const unsigned char *name)
{
unsigned int result;
unsigned int temp0;
unsigned int temp1;
__asm__ __volatile__
("movzbl (%1),%2\n\t"
"testl %2, %2\n\t"
"jz 1f\n\t"
"movl %2, %0\n\t"
"movzbl 1(%1), %2\n\t"
"jecxz 1f\n\t"
"shll $4, %0\n\t"
"addl %2, %0\n\t"
"movzbl 2(%1), %2\n\t"
"jecxz 1f\n\t"
"shll $4, %0\n\t"
"addl %2, %0\n\t"
"movzbl 3(%1), %2\n\t"
"jecxz 1f\n\t"
"shll $4, %0\n\t"
"addl %2, %0\n\t"
"movzbl 4(%1), %2\n\t"
"jecxz 1f\n\t"
"shll $4, %0\n\t"
"addl $5, %1\n\t"
"addl %2, %0\n\t"
"movzbl (%1), %2\n\t"
"jecxz 1f\n"
"2:\t"
"shll $4, %0\n\t"
"movl $0xf0000000, %3\n\t"
"incl %1\n\t"
"addl %2, %0\n\t"
"andl %0, %3\n\t"
"andl $0x0fffffff, %0\n\t"
"shrl $24, %3\n\t"
"movzbl (%1), %2\n\t"
"xorl %3, %0\n\t"
"testl %2, %2\n\t"
"jnz 2b\n"
"1:\t"
: "=&r" (result), "=r" (name), "=&c" (temp0), "=&r" (temp1)
: "0" (0), "1" (name));
return result;
}
#endif /* dl-hash.h */