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
|
// Copyright 2006-2008 the V8 project authors. All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following
// disclaimer in the documentation and/or other materials provided
// with the distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived
// from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#ifndef V8_COMPILER_INTRINSICS_H_
#define V8_COMPILER_INTRINSICS_H_
namespace v8 {
namespace internal {
class CompilerIntrinsics {
public:
// Returns number of zero bits preceding least significant 1 bit.
// Undefined for zero value.
INLINE(static int CountTrailingZeros(uint32_t value));
// Returns number of zero bits following most significant 1 bit.
// Undefined for zero value.
INLINE(static int CountLeadingZeros(uint32_t value));
// Returns the number of bits set.
INLINE(static int CountSetBits(uint32_t value));
};
#ifdef __GNUC__
int CompilerIntrinsics::CountTrailingZeros(uint32_t value) {
return __builtin_ctz(value);
}
int CompilerIntrinsics::CountLeadingZeros(uint32_t value) {
return __builtin_clz(value);
}
int CompilerIntrinsics::CountSetBits(uint32_t value) {
return __builtin_popcount(value);
}
#elif defined(_MSC_VER)
#pragma intrinsic(_BitScanForward)
#pragma intrinsic(_BitScanReverse)
int CompilerIntrinsics::CountTrailingZeros(uint32_t value) {
unsigned long result; //NOLINT
_BitScanForward(&result, static_cast<long>(value)); //NOLINT
return static_cast<int>(result);
}
int CompilerIntrinsics::CountLeadingZeros(uint32_t value) {
unsigned long result; //NOLINT
_BitScanReverse(&result, static_cast<long>(value)); //NOLINT
return 31 - static_cast<int>(result);
}
int CompilerIntrinsics::CountSetBits(uint32_t value) {
// Manually count set bits.
value = ((value >> 1) & 0x55555555) + (value & 0x55555555);
value = ((value >> 2) & 0x33333333) + (value & 0x33333333);
value = ((value >> 4) & 0x0f0f0f0f) + (value & 0x0f0f0f0f);
value = ((value >> 8) & 0x00ff00ff) + (value & 0x00ff00ff);
value = ((value >> 16) & 0x0000ffff) + (value & 0x0000ffff);
return value;
}
#else
#error Unsupported compiler
#endif
} } // namespace v8::internal
#endif // V8_COMPILER_INTRINSICS_H_
|
