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
8namespace v8 {
9namespace base {
10
11// ----------------------------------------------------------------------------
12
13// The magic numbers for division via multiplication, see Warren's "Hacker's
14// Delight", chapter 10. The template parameter must be one of the unsigned
15// integral types.
16template <class T>
17struct MagicNumbersForDivision {
18  MagicNumbersForDivision(T m, unsigned s, bool a)
19      : multiplier(m), shift(s), add(a) {}
20  bool operator==(const MagicNumbersForDivision& rhs) const;
21
22  T multiplier;
23  unsigned shift;
24  bool add;
25};
26
27
28// Calculate the multiplier and shift for signed division via multiplication.
29// The divisor must not be -1, 0 or 1 when interpreted as a signed value.
30template <class T>
31MagicNumbersForDivision<T> SignedDivisionByConstant(T d);
32
33
34// Calculate the multiplier and shift for unsigned division via multiplication,
35// see Warren's "Hacker's Delight", chapter 10. The divisor must not be 0 and
36// leading_zeros can be used to speed up the calculation if the given number of
37// upper bits of the dividend value are known to be zero.
38template <class T>
39MagicNumbersForDivision<T> UnsignedDivisionByConstant(
40    T d, unsigned leading_zeros = 0);
41
42}  // namespace base
43}  // namespace v8
44
45#endif  // V8_BASE_DIVISION_BY_CONSTANT_H_
46