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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-exception6//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-bits16 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 native21// ctz instruction, gcc resolves __builtin_ctz to __ctzdi2 rather than22// __ctzsi2, leading to infinite recursion.23#define __builtin_ctz(a) __ctzsi2(a)24extern int __ctzsi2(si_int);25#endif26 27// Precondition: a != 028 29COMPILER_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