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Side by Side Diff: src/base/division-by-constant.h

Issue 2381273002: Turn libbase into a component (Closed)
Patch Set: updates Created 4 years, 2 months ago
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1 // Copyright 2014 the V8 project authors. All rights reserved. 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 2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file. 3 // found in the LICENSE file.
4 4
5 #ifndef V8_BASE_DIVISION_BY_CONSTANT_H_ 5 #ifndef V8_BASE_DIVISION_BY_CONSTANT_H_
6 #define V8_BASE_DIVISION_BY_CONSTANT_H_ 6 #define V8_BASE_DIVISION_BY_CONSTANT_H_
7 7
8 #include <stdint.h>
9
10 #include "src/base/base-export.h"
11
8 namespace v8 { 12 namespace v8 {
9 namespace base { 13 namespace base {
10 14
11 // ---------------------------------------------------------------------------- 15 // ----------------------------------------------------------------------------
12 16
13 // The magic numbers for division via multiplication, see Warren's "Hacker's 17 // 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 18 // Delight", chapter 10. The template parameter must be one of the unsigned
15 // integral types. 19 // integral types.
16 template <class T> 20 template <class T>
17 struct MagicNumbersForDivision { 21 struct V8_BASE_EXPORT MagicNumbersForDivision {
18 MagicNumbersForDivision(T m, unsigned s, bool a) 22 MagicNumbersForDivision(T m, unsigned s, bool a)
19 : multiplier(m), shift(s), add(a) {} 23 : multiplier(m), shift(s), add(a) {}
20 bool operator==(const MagicNumbersForDivision& rhs) const; 24 bool operator==(const MagicNumbersForDivision& rhs) const {
25 return multiplier == rhs.multiplier && shift == rhs.shift && add == rhs.add;
26 }
21 27
22 T multiplier; 28 T multiplier;
23 unsigned shift; 29 unsigned shift;
24 bool add; 30 bool add;
25 }; 31 };
26 32
27 33
28 // Calculate the multiplier and shift for signed division via multiplication. 34 // 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. 35 // The divisor must not be -1, 0 or 1 when interpreted as a signed value.
30 template <class T> 36 template <class T>
31 MagicNumbersForDivision<T> SignedDivisionByConstant(T d); 37 V8_BASE_EXPORT MagicNumbersForDivision<T> SignedDivisionByConstant(T d);
32
33 38
34 // Calculate the multiplier and shift for unsigned division via multiplication, 39 // 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 40 // 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 41 // 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. 42 // upper bits of the dividend value are known to be zero.
38 template <class T> 43 template <class T>
39 MagicNumbersForDivision<T> UnsignedDivisionByConstant( 44 V8_BASE_EXPORT MagicNumbersForDivision<T> UnsignedDivisionByConstant(
40 T d, unsigned leading_zeros = 0); 45 T d, unsigned leading_zeros = 0);
41 46
47 template struct V8_BASE_EXPORT MagicNumbersForDivision<uint32_t>;
48 template struct V8_BASE_EXPORT MagicNumbersForDivision<uint64_t>;
49
50 extern template V8_BASE_EXPORT MagicNumbersForDivision<uint32_t>
51 SignedDivisionByConstant(uint32_t d);
52 extern template V8_BASE_EXPORT MagicNumbersForDivision<uint64_t>
53 SignedDivisionByConstant(uint64_t d);
54
55 extern template V8_BASE_EXPORT MagicNumbersForDivision<uint32_t>
56 UnsignedDivisionByConstant(uint32_t d, unsigned leading_zeros);
57 extern template V8_BASE_EXPORT MagicNumbersForDivision<uint64_t>
58 UnsignedDivisionByConstant(uint64_t d, unsigned leading_zeros);
59
42 } // namespace base 60 } // namespace base
43 } // namespace v8 61 } // namespace v8
44 62
45 #endif // V8_BASE_DIVISION_BY_CONSTANT_H_ 63 #endif // V8_BASE_DIVISION_BY_CONSTANT_H_
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