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