1/* ===-- ctzdi2.c - Implement __ctzdi2 -------------------------------------===
2 *
3 * The LLVM Compiler Infrastructure
4 *
5 * This file is dual licensed under the MIT and the University of Illinois Open
6 * Source Licenses. 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#if !defined(__clang__) && \
20 ((defined(__sparc__) && defined(__arch64__)) || \
21 defined(__mips64) || \
22 (defined(__riscv) && __SIZEOF_POINTER__ >= 8))
23/* On 64-bit architectures with neither a native clz instruction nor a native
24 * ctz instruction, gcc resolves __builtin_ctz to __ctzdi2 rather than
25 * __ctzsi2, leading to infinite recursion. */
26#define __builtin_ctz(a) __ctzsi2(a)
27extern si_int __ctzsi2(si_int);
28#endif
29
30/* Precondition: a != 0 */
31
32COMPILER_RT_ABI si_int
33__ctzdi2(di_int a)
34{
35 dwords x;
36 x.all = a;
37 const si_int f = -(x.s.low == 0);
38 return __builtin_ctz((x.s.high & f) | (x.s.low & ~f)) +
39 (f & ((si_int)(sizeof(si_int) * CHAR_BIT)));
40}