1 // Copyright 2015, VIXL authors
2 // All rights reserved.
3 //
4 // Redistribution and use in source and binary forms, with or without
5 // modification, are permitted provided that the following conditions are met:
6 //
7 // * Redistributions of source code must retain the above copyright notice,
8 // this list of conditions and the following disclaimer.
9 // * Redistributions in binary form must reproduce the above copyright notice,
10 // this list of conditions and the following disclaimer in the documentation
11 // and/or other materials provided with the distribution.
12 // * Neither the name of ARM Limited nor the names of its contributors may be
13 // used to endorse or promote products derived from this software without
14 // specific prior written permission.
15 //
16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS CONTRIBUTORS "AS IS" AND
17 // ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
18 // WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
19 // DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
20 // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
22 // SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
23 // CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 // OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
25 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26
27
28 #ifndef VIXL_COMPILER_INTRINSICS_H
29 #define VIXL_COMPILER_INTRINSICS_H
30
31 #include <limits.h>
32 #include "globals-vixl.h"
33
34 namespace vixl {
35
36 // Helper to check whether the version of GCC used is greater than the specified
37 // requirement.
38 #define MAJOR 1000000
39 #define MINOR 1000
40 #if defined(__GNUC__) && defined(__GNUC_MINOR__) && defined(__GNUC_PATCHLEVEL__)
41 #define GCC_VERSION_OR_NEWER(major, minor, patchlevel) \
42 ((__GNUC__ * (MAJOR) + __GNUC_MINOR__ * (MINOR) + __GNUC_PATCHLEVEL__) >= \
43 ((major) * (MAJOR) + ((minor)) * (MINOR) + (patchlevel)))
44 #elif defined(__GNUC__) && defined(__GNUC_MINOR__)
45 #define GCC_VERSION_OR_NEWER(major, minor, patchlevel) \
46 ((__GNUC__ * (MAJOR) + __GNUC_MINOR__ * (MINOR)) >= \
47 ((major) * (MAJOR) + ((minor)) * (MINOR) + (patchlevel)))
48 #else
49 #define GCC_VERSION_OR_NEWER(major, minor, patchlevel) 0
50 #endif
51
52
53 #if defined(__clang__) && !defined(VIXL_NO_COMPILER_BUILTINS)
54
55 // clang-format off
56 #define COMPILER_HAS_BUILTIN_CLRSB (__has_builtin(__builtin_clrsb))
57 #define COMPILER_HAS_BUILTIN_CLZ (__has_builtin(__builtin_clz))
58 #define COMPILER_HAS_BUILTIN_CTZ (__has_builtin(__builtin_ctz))
59 #define COMPILER_HAS_BUILTIN_FFS (__has_builtin(__builtin_ffs))
60 #define COMPILER_HAS_BUILTIN_POPCOUNT (__has_builtin(__builtin_popcount))
61 // clang-format on
62
63 #elif defined(__GNUC__) && !defined(VIXL_NO_COMPILER_BUILTINS)
64 // The documentation for these builtins is available at:
65 // https://gcc.gnu.org/onlinedocs/gcc-$MAJOR.$MINOR.$PATCHLEVEL/gcc//Other-Builtins.html
66
67 // clang-format off
68 # define COMPILER_HAS_BUILTIN_CLRSB (GCC_VERSION_OR_NEWER(4, 7, 0))
69 # define COMPILER_HAS_BUILTIN_CLZ (GCC_VERSION_OR_NEWER(3, 4, 0))
70 # define COMPILER_HAS_BUILTIN_CTZ (GCC_VERSION_OR_NEWER(3, 4, 0))
71 # define COMPILER_HAS_BUILTIN_FFS (GCC_VERSION_OR_NEWER(3, 4, 0))
72 # define COMPILER_HAS_BUILTIN_POPCOUNT (GCC_VERSION_OR_NEWER(3, 4, 0))
73 // clang-format on
74
75 #else
76 // One can define VIXL_NO_COMPILER_BUILTINS to force using the manually
77 // implemented C++ methods.
78
79 // clang-format off
80 #define COMPILER_HAS_BUILTIN_BSWAP false
81 #define COMPILER_HAS_BUILTIN_CLRSB false
82 #define COMPILER_HAS_BUILTIN_CLZ false
83 #define COMPILER_HAS_BUILTIN_CTZ false
84 #define COMPILER_HAS_BUILTIN_FFS false
85 #define COMPILER_HAS_BUILTIN_POPCOUNT false
86 // clang-format on
87
88 #endif
89
90
91 template <typename V>
IsPowerOf2(V value)92 inline bool IsPowerOf2(V value) {
93 return (value != 0) && ((value & (value - 1)) == 0);
94 }
95
96
97 // Declaration of fallback functions.
98 int CountLeadingSignBitsFallBack(int64_t value, int width);
99 int CountLeadingZerosFallBack(uint64_t value, int width);
100 int CountSetBitsFallBack(uint64_t value, int width);
101 int CountTrailingZerosFallBack(uint64_t value, int width);
102
103
104 // Implementation of intrinsics functions.
105 // TODO: The implementations could be improved for sizes different from 32bit
106 // and 64bit: we could mask the values and call the appropriate builtin.
107
108 // Return the number of leading bits that match the topmost (sign) bit,
109 // excluding the topmost bit itself.
110 template <typename V>
111 inline int CountLeadingSignBits(V value, int width = (sizeof(V) * 8)) {
112 VIXL_ASSERT(IsPowerOf2(width) && (width <= 64));
113 #if COMPILER_HAS_BUILTIN_CLRSB
114 VIXL_ASSERT((LLONG_MIN <= value) && (value <= LLONG_MAX));
115 int ll_width = sizeof(long long) * kBitsPerByte; // NOLINT(runtime/int)
116 int result = __builtin_clrsbll(value) - (ll_width - width);
117 // Check that the value fits in the specified width.
118 VIXL_ASSERT(result >= 0);
119 return result;
120 #else
121 VIXL_ASSERT((INT64_MIN <= value) && (value <= INT64_MAX));
122 return CountLeadingSignBitsFallBack(value, width);
123 #endif
124 }
125
126
127 template <typename V>
128 inline int CountLeadingZeros(V value, int width = (sizeof(V) * 8)) {
129 #if COMPILER_HAS_BUILTIN_CLZ
130 if (width == 32) {
131 return (value == 0) ? 32 : __builtin_clz(static_cast<unsigned>(value));
132 } else if (width == 64) {
133 return (value == 0) ? 64 : __builtin_clzll(value);
134 }
135 #endif
136 return CountLeadingZerosFallBack(value, width);
137 }
138
139
140 template <typename V>
141 inline int CountSetBits(V value, int width = (sizeof(V) * 8)) {
142 #if COMPILER_HAS_BUILTIN_POPCOUNT
143 if (width == 32) {
144 return __builtin_popcount(static_cast<unsigned>(value));
145 } else if (width == 64) {
146 return __builtin_popcountll(value);
147 }
148 #endif
149 return CountSetBitsFallBack(value, width);
150 }
151
152
153 template <typename V>
154 inline int CountTrailingZeros(V value, int width = (sizeof(V) * 8)) {
155 #if COMPILER_HAS_BUILTIN_CTZ
156 if (width == 32) {
157 return (value == 0) ? 32 : __builtin_ctz(static_cast<unsigned>(value));
158 } else if (width == 64) {
159 return (value == 0) ? 64 : __builtin_ctzll(value);
160 }
161 #endif
162 return CountTrailingZerosFallBack(value, width);
163 }
164
165 } // namespace vixl
166
167 #endif // VIXL_COMPILER_INTRINSICS_H
168