glibc/sysdeps/s390/ffs.c

/* ffs -- find first set bit in a word, counted from least significant end.
   This file is part of the GNU C Library.
   Copyright (C) 2000 Free Software Foundation, Inc.
   Contributed by Martin Schwidefsky (schwidefsky@de.ibm.com).

   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.  */

#define ffsl __something_else
#include <string.h>

#undef	ffs

/*
 * ffs: find first bit set. This is defined the same way as
 * the libc and compiler builtin ffs routines, therefore
 * differs in spirit from the above ffz (man ffs).
 */

int
__ffs (x)
     int x;
{
  int r;

  if (x == 0)
    return 0;
  __asm__("    lr   %%r1,%1\n"
	  "    sr   %0,%0\n"
	  "    tml  %%r1,0xFFFF\n"
	  "    jnz  0f\n"
	  "    ahi  %0,16\n"
	  "    srl  %%r1,16\n"
	  "0:  tml  %%r1,0x00FF\n"
	  "    jnz  1f\n"
	  "    ahi  %0,8\n"
	  "    srl  %%r1,8\n"
	  "1:  tml  %%r1,0x000F\n"
	  "    jnz  2f\n"
	  "    ahi  %0,4\n"
	  "    srl  %%r1,4\n"
	  "2:  tml  %%r1,0x0003\n"
	  "    jnz  3f\n"
	  "    ahi  %0,2\n"
	  "    srl  %%r1,2\n"
	  "3:  tml  %%r1,0x0001\n"
	  "    jnz  4f\n"
	  "    ahi  %0,1\n"
	  "4:"
	  : "=&d" (r) : "d" (x) : "cc", "1" );
  return r+1;
}

weak_alias (__ffs, ffs)
#undef ffsl
weak_alias (__ffs, ffsl)