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