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
12namespace v8 {
13namespace base {
14
15// ----------------------------------------------------------------------------
16
17// The magic numbers for division via multiplication, see Warren's "Hacker's
18// Delight", chapter 10. The template parameter must be one of the unsigned
19// integral types.
20template <class T>
21struct V8_BASE_EXPORT MagicNumbersForDivision {
22  MagicNumbersForDivision(T m, unsigned s, bool a)
23      : multiplier(m), shift(s), add(a) {}
24  bool operator==(const MagicNumbersForDivision& rhs) const {
25    return multiplier == rhs.multiplier && shift == rhs.shift && add == rhs.add;
26  }
27
28  T multiplier;
29  unsigned shift;
30  bool add;
31};
32
33
34// Calculate the multiplier and shift for signed division via multiplication.
35// The divisor must not be -1, 0 or 1 when interpreted as a signed value.
36template <class T>
37V8_BASE_EXPORT MagicNumbersForDivision<T> SignedDivisionByConstant(T d);
38
39// Calculate the multiplier and shift for unsigned division via multiplication,
40// see Warren's "Hacker's Delight", chapter 10. The divisor must not be 0 and
41// leading_zeros can be used to speed up the calculation if the given number of
42// upper bits of the dividend value are known to be zero.
43template <class T>
44V8_BASE_EXPORT MagicNumbersForDivision<T> UnsignedDivisionByConstant(
45    T d, unsigned leading_zeros = 0);
46
47extern template V8_BASE_EXPORT MagicNumbersForDivision<uint32_t>
48SignedDivisionByConstant(uint32_t d);
49extern template V8_BASE_EXPORT MagicNumbersForDivision<uint64_t>
50SignedDivisionByConstant(uint64_t d);
51
52extern template V8_BASE_EXPORT MagicNumbersForDivision<uint32_t>
53UnsignedDivisionByConstant(uint32_t d, unsigned leading_zeros);
54extern template V8_BASE_EXPORT MagicNumbersForDivision<uint64_t>
55UnsignedDivisionByConstant(uint64_t d, unsigned leading_zeros);
56
57}  // namespace base
58}  // namespace v8
59
60#endif  // V8_BASE_DIVISION_BY_CONSTANT_H_
61