sysdeps/s390/ffs.c

   1 /* ffs -- find first set bit in a word, counted from least significant end.
   2    S/390 version.
   3    Copyright (C) 2000-2023 Free Software Foundation, Inc.
   4    This file is part of the GNU C Library.
   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    <https://www.gnu.org/licenses/>.  */
  19
  20 #include <limits.h>
  21 #define ffsl __something_else
  22 #include <string.h>
  23
  24 #undef  ffs
  25
  26 /* ffs: find first bit set. This is defined the same way as
  27    the libc and compiler builtin ffs routines, therefore
  28    differs in spirit from the above ffz (man ffs).  */
  29
  30 int
  31 __ffs (int x)
  32 {
  33         int r;
  34
  35         if (x == 0)
  36           return 0;
  37         __asm__("    lr   %%r1,%1\n"
  38                 "    sr   %0,%0\n"
  39                 "    tml  %%r1,0xFFFF\n"
  40                 "    jnz  0f\n"
  41                 "    ahi  %0,16\n"
  42                 "    srl  %%r1,16\n"
  43                 "0:  tml  %%r1,0x00FF\n"
  44                 "    jnz  1f\n"
  45                 "    ahi  %0,8\n"
  46                 "    srl  %%r1,8\n"
  47                 "1:  tml  %%r1,0x000F\n"
  48                 "    jnz  2f\n"
  49                 "    ahi  %0,4\n"
  50                 "    srl  %%r1,4\n"
  51                 "2:  tml  %%r1,0x0003\n"
  52                 "    jnz  3f\n"
  53                 "    ahi  %0,2\n"
  54                 "    srl  %%r1,2\n"
  55                 "3:  tml  %%r1,0x0001\n"
  56                 "    jnz  4f\n"
  57                 "    ahi  %0,1\n"
  58                 "4:"
  59                 : "=&d" (r) : "d" (x) : "cc", "1" );
  60         return r+1;
  61 }
  62
  63 weak_alias (__ffs, ffs)
  64 libc_hidden_def (__ffs)
  65 libc_hidden_builtin_def (ffs)
  66 #if ULONG_MAX == UINT_MAX
  67 #undef ffsl
  68 weak_alias (__ffs, ffsl)
  69 #endif