forked from OSchip/llvm-project
36 lines
1.3 KiB
C
36 lines
1.3 KiB
C
//===-- 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 int __ctzsi2(si_int);
|
|
#endif
|
|
|
|
// Precondition: a != 0
|
|
|
|
COMPILER_RT_ABI int __ctzdi2(di_int a) {
|
|
dwords x;
|
|
x.all = a;
|
|
const si_int f = -(x.s.low == 0);
|
|
return ctzsi((x.s.high & f) | (x.s.low & ~f)) +
|
|
(f & ((si_int)(sizeof(si_int) * CHAR_BIT)));
|
|
}
|