1 //===-- ctzdi2.c - Implement __ctzdi2 -------------------------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file implements __ctzdi2 for the compiler_rt library. 10 // 11 //===----------------------------------------------------------------------===// 12 13 #include "int_lib.h" 14 15 // Returns: the number of trailing 0-bits 16 17 #if !defined(__clang__) && \ 18 ((defined(__sparc__) && defined(__arch64__)) || defined(__mips64) || \ 19 (defined(__riscv) && __SIZEOF_POINTER__ >= 8)) 20 // On 64-bit architectures with neither a native clz instruction nor a native 21 // ctz instruction, gcc resolves __builtin_ctz to __ctzdi2 rather than 22 // __ctzsi2, leading to infinite recursion. 23 #define __builtin_ctz(a) __ctzsi2(a) 24 extern int __ctzsi2(si_int); 25 #endif 26 27 // Precondition: a != 0 28 29 COMPILER_RT_ABI int __ctzdi2(di_int a) { 30 dwords x; 31 x.all = a; 32 const si_int f = -(x.s.low == 0); 33 return ctzsi((x.s.high & f) | (x.s.low & ~f)) + 34 (f & ((si_int)(sizeof(si_int) * CHAR_BIT))); 35 } 36