ctzdi2.c revision 77ed6142daed1e068fbda64405d0de9845e40e1a 
1/* ===-- ctzdi2.c - Implement __ctzdi2 -------------------------------------===
2 *
3 *                     The LLVM Compiler Infrastructure
4 *
5 * This file is distributed under the University of Illinois Open Source
6 * License. See LICENSE.TXT for details.
7 *
8 * ===----------------------------------------------------------------------===
9 *
10 * This file implements __ctzdi2 for the compiler_rt library.
11 *
12 * ===----------------------------------------------------------------------===
13 */
14
15#include "int_lib.h"
16
17/* Returns: the number of trailing 0-bits  */
18
19/* Precondition: a != 0 */
20
21si_int
22__ctzdi2(di_int a)
23{
24    dwords x;
25    x.all = a;
26    const si_int f = -(x.s.low == 0);
27    return __builtin_ctz((x.s.high & f) | (x.s.low & ~f)) +
28              (f & ((si_int)(sizeof(si_int) * CHAR_BIT)));
29}
30