1 // Copyright 2014 the V8 project authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #ifndef V8_BASE_DIVISION_BY_CONSTANT_H_
6 #define V8_BASE_DIVISION_BY_CONSTANT_H_
7
8 #include <stdint.h>
9
10 #include "src/base/base-export.h"
11 #include "src/base/export-template.h"
12
13 namespace v8 {
14 namespace base {
15
16 // ----------------------------------------------------------------------------
17
18 // The magic numbers for division via multiplication, see Warren's "Hacker's
19 // Delight", chapter 10. The template parameter must be one of the unsigned
20 // integral types.
21 template <class T>
EXPORT_TEMPLATE_DECLARE(V8_BASE_EXPORT)22 struct EXPORT_TEMPLATE_DECLARE(V8_BASE_EXPORT) MagicNumbersForDivision {
23 MagicNumbersForDivision(T m, unsigned s, bool a)
24 : multiplier(m), shift(s), add(a) {}
25 bool operator==(const MagicNumbersForDivision& rhs) const {
26 return multiplier == rhs.multiplier && shift == rhs.shift && add == rhs.add;
27 }
28
29 T multiplier;
30 unsigned shift;
31 bool add;
32 };
33
34
35 // Calculate the multiplier and shift for signed division via multiplication.
36 // The divisor must not be -1, 0 or 1 when interpreted as a signed value.
37 template <class T>
38 EXPORT_TEMPLATE_DECLARE(V8_BASE_EXPORT)
39 MagicNumbersForDivision<T> SignedDivisionByConstant(T d);
40
41 // Calculate the multiplier and shift for unsigned division via multiplication,
42 // see Warren's "Hacker's Delight", chapter 10. The divisor must not be 0 and
43 // leading_zeros can be used to speed up the calculation if the given number of
44 // upper bits of the dividend value are known to be zero.
45 template <class T>
46 EXPORT_TEMPLATE_DECLARE(V8_BASE_EXPORT)
47 MagicNumbersForDivision<T> UnsignedDivisionByConstant(
48 T d, unsigned leading_zeros = 0);
49
50 // Explicit instantiation declarations.
51 extern template struct EXPORT_TEMPLATE_DECLARE(V8_BASE_EXPORT)
52 MagicNumbersForDivision<uint32_t>;
53 extern template struct EXPORT_TEMPLATE_DECLARE(V8_BASE_EXPORT)
54 MagicNumbersForDivision<uint64_t>;
55
56 extern template EXPORT_TEMPLATE_DECLARE(V8_BASE_EXPORT)
57 MagicNumbersForDivision<uint32_t> SignedDivisionByConstant(uint32_t d);
58 extern template EXPORT_TEMPLATE_DECLARE(V8_BASE_EXPORT)
59 MagicNumbersForDivision<uint64_t> SignedDivisionByConstant(uint64_t d);
60
61 extern template EXPORT_TEMPLATE_DECLARE(V8_BASE_EXPORT)
62 MagicNumbersForDivision<uint32_t> UnsignedDivisionByConstant(
63 uint32_t d, unsigned leading_zeros);
64 extern template EXPORT_TEMPLATE_DECLARE(V8_BASE_EXPORT)
65 MagicNumbersForDivision<uint64_t> UnsignedDivisionByConstant(
66 uint64_t d, unsigned leading_zeros);
67
68 } // namespace base
69 } // namespace v8
70
71 #endif // V8_BASE_DIVISION_BY_CONSTANT_H_
72