| 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 | |
|---|
