| /* ===-- ctzdi2.c - Implement __ctzdi2 -------------------------------------=== |
| * |
| * Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| * See https://llvm.org/LICENSE.txt for license information. |
| * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| * |
| * ===----------------------------------------------------------------------=== |
| * |
| * This file implements __ctzdi2 for the compiler_rt library. |
| * |
| * ===----------------------------------------------------------------------=== |
| */ |
| |
| #include "int_lib.h" |
| |
| /* Returns: the number of trailing 0-bits */ |
| |
| #if !defined(__clang__) && \ |
| ((defined(__sparc__) && defined(__arch64__)) || \ |
| defined(__mips64) || \ |
| (defined(__riscv) && __SIZEOF_POINTER__ >= 8)) |
| /* On 64-bit architectures with neither a native clz instruction nor a native |
| * ctz instruction, gcc resolves __builtin_ctz to __ctzdi2 rather than |
| * __ctzsi2, leading to infinite recursion. */ |
| #define __builtin_ctz(a) __ctzsi2(a) |
| extern si_int __ctzsi2(si_int); |
| #endif |
| |
| /* Precondition: a != 0 */ |
| |
| COMPILER_RT_ABI si_int |
| __ctzdi2(di_int a) |
| { |
| dwords x; |
| x.all = a; |
| const si_int f = -(x.s.low == 0); |
| return __builtin_ctz((x.s.high & f) | (x.s.low & ~f)) + |
| (f & ((si_int)(sizeof(si_int) * CHAR_BIT))); |
| } |