/* ffsll -- find first set bit in a word, counted from least significant end. For AMD x86-64. This file is part of the GNU C Library. Copyright (C) 1991-2018 Free Software Foundation, Inc. Contributed by Ulrich Drepper . The GNU C Library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 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 Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with the GNU C Library; if not, see . */ #define ffsl __something_else #include #undef ffsll int ffsll (long long int x) { long long int cnt; long long int tmp; asm ("bsfq %2,%0\n" /* Count low bits in X and store in %1. */ "cmoveq %1,%0\n" /* If number was zero, use -1 as result. */ : "=&r" (cnt), "=r" (tmp) : "rm" (x), "1" (-1)); return cnt + 1; } #ifndef __ILP32__ #undef ffsl weak_alias (ffsll, ffsl) #endif