Line data    Source code

       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             : #include "src/base/export-template.h"
      12             : 
      13             : namespace v8 {
      14             : namespace base {
      15             : 
      16             : // ----------------------------------------------------------------------------
      17             : 
      18             : // The magic numbers for division via multiplication, see Warren's "Hacker's
      19             : // Delight", chapter 10. The template parameter must be one of the unsigned
      20             : // integral types.
      21             : template <class T>
      22             : struct EXPORT_TEMPLATE_DECLARE(V8_BASE_EXPORT) MagicNumbersForDivision {
      23           0 :   MagicNumbersForDivision(T m, unsigned s, bool a)
      24        1840 :       : multiplier(m), shift(s), add(a) {}
      25           0 :   bool operator==(const MagicNumbersForDivision& rhs) const {
      26         328 :     return multiplier == rhs.multiplier && shift == rhs.shift && add == rhs.add;
      27             :   }
      28             : 
      29             :   T multiplier;
      30             :   unsigned shift;
      31             :   bool add;
      32             : };
      33             : 
      34             : 
      35             : // Calculate the multiplier and shift for signed division via multiplication.
      36             : // The divisor must not be -1, 0 or 1 when interpreted as a signed value.
      37             : template <class T>
      38             : EXPORT_TEMPLATE_DECLARE(V8_BASE_EXPORT)
      39             : MagicNumbersForDivision<T> SignedDivisionByConstant(T d);
      40             : 
      41             : // Calculate the multiplier and shift for unsigned division via multiplication,
      42             : // see Warren's "Hacker's Delight", chapter 10. The divisor must not be 0 and
      43             : // leading_zeros can be used to speed up the calculation if the given number of
      44             : // upper bits of the dividend value are known to be zero.
      45             : template <class T>
      46             : EXPORT_TEMPLATE_DECLARE(V8_BASE_EXPORT)
      47             : MagicNumbersForDivision<T> UnsignedDivisionByConstant(
      48             :     T d, unsigned leading_zeros = 0);
      49             : 
      50             : // Explicit instantiation declarations.
      51             : extern template struct EXPORT_TEMPLATE_DECLARE(V8_BASE_EXPORT)
      52             :     MagicNumbersForDivision<uint32_t>;
      53             : extern template struct EXPORT_TEMPLATE_DECLARE(V8_BASE_EXPORT)
      54             :     MagicNumbersForDivision<uint64_t>;
      55             : 
      56             : extern template EXPORT_TEMPLATE_DECLARE(V8_BASE_EXPORT)
      57             :     MagicNumbersForDivision<uint32_t> SignedDivisionByConstant(uint32_t d);
      58             : extern template EXPORT_TEMPLATE_DECLARE(V8_BASE_EXPORT)
      59             :     MagicNumbersForDivision<uint64_t> SignedDivisionByConstant(uint64_t d);
      60             : 
      61             : extern template EXPORT_TEMPLATE_DECLARE(V8_BASE_EXPORT)
      62             :     MagicNumbersForDivision<uint32_t> UnsignedDivisionByConstant(
      63             :         uint32_t d, unsigned leading_zeros);
      64             : extern template EXPORT_TEMPLATE_DECLARE(V8_BASE_EXPORT)
      65             :     MagicNumbersForDivision<uint64_t> UnsignedDivisionByConstant(
      66             :         uint64_t d, unsigned leading_zeros);
      67             : 
      68             : }  // namespace base
      69             : }  // namespace v8
      70             : 
      71             : #endif  // V8_BASE_DIVISION_BY_CONSTANT_H_