sysdeps/i386/i686/dl-hash.h

   1 /* Compute hash alue for given string according to ELF standard.
   2    Copyright (C) 1998-2014 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #ifndef _DL_HASH_H
  21 #define _DL_HASH_H      1
  22
  23
  24 /* This is the hashing function specified by the ELF ABI.  It is highly
  25    optimized for the PII processors.  Though it will run on i586 it
  26    would be much slower than the generic C implementation.  So don't
  27    use it.  */
  28 static unsigned int
  29 _dl_elf_hash (const char *name)
  30 {
  31   unsigned int result;
  32   unsigned int temp0;
  33   unsigned int temp1;
  34
  35   __asm__ __volatile__
  36     ("movzbl (%1),%2\n\t"
  37      "testl %2, %2\n\t"
  38      "jz 1f\n\t"
  39      "movl %2, %0\n\t"
  40      "movzbl 1(%1), %2\n\t"
  41      "jecxz 1f\n\t"
  42      "shll $4, %0\n\t"
  43      "addl %2, %0\n\t"
  44      "movzbl 2(%1), %2\n\t"
  45      "jecxz 1f\n\t"
  46      "shll $4, %0\n\t"
  47      "addl %2, %0\n\t"
  48      "movzbl 3(%1), %2\n\t"
  49      "jecxz 1f\n\t"
  50      "shll $4, %0\n\t"
  51      "addl %2, %0\n\t"
  52      "movzbl 4(%1), %2\n\t"
  53      "jecxz 1f\n\t"
  54      "shll $4, %0\n\t"
  55      "addl $5, %1\n\t"
  56      "addl %2, %0\n\t"
  57      "movzbl (%1), %2\n\t"
  58      "jecxz 1f\n"
  59      "2:\t"
  60      "shll $4, %0\n\t"
  61      "movl $0xf0000000, %3\n\t"
  62      "incl %1\n\t"
  63      "addl %2, %0\n\t"
  64      "andl %0, %3\n\t"
  65      "andl $0x0fffffff, %0\n\t"
  66      "shrl $24, %3\n\t"
  67      "movzbl (%1), %2\n\t"
  68      "xorl %3, %0\n\t"
  69      "testl %2, %2\n\t"
  70      "jnz 2b\n"
  71      "1:\t"
  72      : "=&r" (result), "=r" (name), "=&c" (temp0), "=&r" (temp1)
  73      : "0" (0), "1" ((const unsigned char *) name));
  74
  75   return result;
  76 }
  77
  78 #endif /* dl-hash.h */