1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
|
//===----------------------------------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
#ifndef _LIBCPP___STRING_CONSTEXPR_C_FUNCTIONS_H
#define _LIBCPP___STRING_CONSTEXPR_C_FUNCTIONS_H
#include <__config>
#include <__type_traits/is_constant_evaluated.h>
#include <__type_traits/is_equality_comparable.h>
#include <__type_traits/is_same.h>
#include <__type_traits/is_trivially_lexicographically_comparable.h>
#include <cstddef>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
#endif
_LIBCPP_BEGIN_NAMESPACE_STD
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 size_t __constexpr_strlen(const char* __str) {
// GCC currently doesn't support __builtin_strlen for heap-allocated memory during constant evaluation.
// https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70816
#ifdef _LIBCPP_COMPILER_GCC
if (__libcpp_is_constant_evaluated()) {
size_t __i = 0;
for (; __str[__i] != '\0'; ++__i)
;
return __i;
}
#endif
return __builtin_strlen(__str);
}
// Because of __libcpp_is_trivially_lexicographically_comparable we know that comparing the object representations is
// equivalent to a std::memcmp. Since we have multiple objects contiguously in memory, we can call memcmp once instead
// of invoking it on every object individually.
template <class _Tp, class _Up>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 int
__constexpr_memcmp(const _Tp* __lhs, const _Up* __rhs, size_t __count) {
static_assert(__libcpp_is_trivially_lexicographically_comparable<_Tp, _Up>::value,
"_Tp and _Up have to be trivially lexicographically comparable");
if (__libcpp_is_constant_evaluated()) {
#ifdef _LIBCPP_COMPILER_CLANG_BASED
if (sizeof(_Tp) == 1 && !is_same<_Tp, bool>::value)
return __builtin_memcmp(__lhs, __rhs, __count);
#endif
while (__count != 0) {
if (*__lhs < *__rhs)
return -1;
if (*__rhs < *__lhs)
return 1;
__count -= sizeof(_Tp);
++__lhs;
++__rhs;
}
return 0;
} else {
return __builtin_memcmp(__lhs, __rhs, __count);
}
}
// Because of __libcpp_is_trivially_equality_comparable we know that comparing the object representations is equivalent
// to a std::memcmp(...) == 0. Since we have multiple objects contiguously in memory, we can call memcmp once instead
// of invoking it on every object individually.
template <class _Tp, class _Up>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 bool
__constexpr_memcmp_equal(const _Tp* __lhs, const _Up* __rhs, size_t __count) {
static_assert(__libcpp_is_trivially_equality_comparable<_Tp, _Up>::value,
"_Tp and _Up have to be trivially equality comparable");
if (__libcpp_is_constant_evaluated()) {
#ifdef _LIBCPP_COMPILER_CLANG_BASED
if (sizeof(_Tp) == 1 && is_integral<_Tp>::value && !is_same<_Tp, bool>::value)
return __builtin_memcmp(__lhs, __rhs, __count) == 0;
#endif
while (__count != 0) {
if (*__lhs != *__rhs)
return false;
__count -= sizeof(_Tp);
++__lhs;
++__rhs;
}
return true;
} else {
return __builtin_memcmp(__lhs, __rhs, __count) == 0;
}
}
inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 const char*
__constexpr_char_memchr(const char* __str, int __char, size_t __count) {
#if __has_builtin(__builtin_char_memchr)
return __builtin_char_memchr(__str, __char, __count);
#else
if (!__libcpp_is_constant_evaluated())
return static_cast<const char*>(__builtin_memchr(__str, __char, __count));
for (; __count; --__count) {
if (*__str == __char)
return __str;
++__str;
}
return nullptr;
#endif
}
_LIBCPP_END_NAMESPACE_STD
#endif // _LIBCPP___STRING_CONSTEXPR_C_FUNCTIONS_H
|
