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
13namespace v8 {
14namespace 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.
21template <class T>
22struct 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.
37template <class T>
38EXPORT_TEMPLATE_DECLARE(V8_BASE_EXPORT)
39MagicNumbersForDivision<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.
45template <class T>
46EXPORT_TEMPLATE_DECLARE(V8_BASE_EXPORT)
47MagicNumbersForDivision<T> UnsignedDivisionByConstant(
48    T d, unsigned leading_zeros = 0);
49
50// Explicit instantiation declarations.
51extern template struct EXPORT_TEMPLATE_DECLARE(V8_BASE_EXPORT)
52    MagicNumbersForDivision<uint32_t>;
53extern template struct EXPORT_TEMPLATE_DECLARE(V8_BASE_EXPORT)
54    MagicNumbersForDivision<uint64_t>;
55
56extern template EXPORT_TEMPLATE_DECLARE(V8_BASE_EXPORT)
57    MagicNumbersForDivision<uint32_t> SignedDivisionByConstant(uint32_t d);
58extern template EXPORT_TEMPLATE_DECLARE(V8_BASE_EXPORT)
59    MagicNumbersForDivision<uint64_t> SignedDivisionByConstant(uint64_t d);
60
61extern template EXPORT_TEMPLATE_DECLARE(V8_BASE_EXPORT)
62    MagicNumbersForDivision<uint32_t> UnsignedDivisionByConstant(
63        uint32_t d, unsigned leading_zeros);
64extern 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