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| 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_ |
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