Ben Murdoch | b8a8cc1 | 2014-11-26 15:28:44 +0000 | [diff] [blame] | 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 | namespace v8 { |
| 9 | namespace 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. |
| 16 | template <class T> |
| 17 | struct 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. |
| 30 | template <class T> |
| 31 | MagicNumbersForDivision<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. |
| 38 | template <class T> |
| 39 | MagicNumbersForDivision<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_ |