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

Issue 2396933002: Revert of Reland "Turn libbase into a component" (Closed)
Patch Set: 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
12 namespace v8 { 8 namespace v8 {
13 namespace base { 9 namespace base {
14 10
15 // ---------------------------------------------------------------------------- 11 // ----------------------------------------------------------------------------
16 12
17 // The magic numbers for division via multiplication, see Warren's "Hacker's 13 // 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 14 // Delight", chapter 10. The template parameter must be one of the unsigned
19 // integral types. 15 // integral types.
20 template <class T> 16 template <class T>
21 struct V8_BASE_EXPORT MagicNumbersForDivision { 17 struct MagicNumbersForDivision {
22 MagicNumbersForDivision(T m, unsigned s, bool a) 18 MagicNumbersForDivision(T m, unsigned s, bool a)
23 : multiplier(m), shift(s), add(a) {} 19 : multiplier(m), shift(s), add(a) {}
24 bool operator==(const MagicNumbersForDivision& rhs) const { 20 bool operator==(const MagicNumbersForDivision& rhs) const;
25 return multiplier == rhs.multiplier && shift == rhs.shift && add == rhs.add;
26 }
27 21
28 T multiplier; 22 T multiplier;
29 unsigned shift; 23 unsigned shift;
30 bool add; 24 bool add;
31 }; 25 };
32 26
33 27
34 // Calculate the multiplier and shift for signed division via multiplication. 28 // 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. 29 // The divisor must not be -1, 0 or 1 when interpreted as a signed value.
36 template <class T> 30 template <class T>
37 V8_BASE_EXPORT MagicNumbersForDivision<T> SignedDivisionByConstant(T d); 31 MagicNumbersForDivision<T> SignedDivisionByConstant(T d);
32
38 33
39 // Calculate the multiplier and shift for unsigned division via multiplication, 34 // 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 35 // 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 36 // 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. 37 // upper bits of the dividend value are known to be zero.
43 template <class T> 38 template <class T>
44 V8_BASE_EXPORT MagicNumbersForDivision<T> UnsignedDivisionByConstant( 39 MagicNumbersForDivision<T> UnsignedDivisionByConstant(
45 T d, unsigned leading_zeros = 0); 40 T d, unsigned leading_zeros = 0);
46 41
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
60 } // namespace base 42 } // namespace base
61 } // namespace v8 43 } // namespace v8
62 44
63 #endif // V8_BASE_DIVISION_BY_CONSTANT_H_ 45 #endif // V8_BASE_DIVISION_BY_CONSTANT_H_
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