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_ 46
