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1 // Copyright 2012 the V8 project authors. All rights reserved. | 1 // Copyright 2012 the V8 project authors. All rights reserved. |
2 // Redistribution and use in source and binary forms, with or without | 2 // Redistribution and use in source and binary forms, with or without |
3 // modification, are permitted provided that the following conditions are | 3 // modification, are permitted provided that the following conditions are |
4 // met: | 4 // met: |
5 // | 5 // |
6 // * Redistributions of source code must retain the above copyright | 6 // * Redistributions of source code must retain the above copyright |
7 // notice, this list of conditions and the following disclaimer. | 7 // notice, this list of conditions and the following disclaimer. |
8 // * Redistributions in binary form must reproduce the above | 8 // * Redistributions in binary form must reproduce the above |
9 // copyright notice, this list of conditions and the following | 9 // copyright notice, this list of conditions and the following |
10 // disclaimer in the documentation and/or other materials provided | 10 // disclaimer in the documentation and/or other materials provided |
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98 x >>= 8; | 98 x >>= 8; |
99 } | 99 } |
100 if (x & 0xf0) { | 100 if (x & 0xf0) { |
101 nibble += 4; | 101 nibble += 4; |
102 x >>= 4; | 102 x >>= 4; |
103 } | 103 } |
104 return nibble + msb4[x]; | 104 return nibble + msb4[x]; |
105 } | 105 } |
106 | 106 |
107 | 107 |
| 108 // Magic numbers for integer division. |
| 109 // These are kind of 2's complement reciprocal of the divisors. |
| 110 // Details and proofs can be found in: |
| 111 // - Hacker's Delight, Henry S. Warren, Jr. |
| 112 // - The PowerPC Compiler Writer’s Guide |
| 113 // and probably many others. |
| 114 // See details in the implementation of the algorithm in |
| 115 // lithium-codegen-arm.cc : LCodeGen::TryEmitSignedIntegerDivisionByConstant(). |
| 116 struct DivMagicNumbers { |
| 117 unsigned M; |
| 118 unsigned s; |
| 119 }; |
| 120 |
| 121 const DivMagicNumbers InvalidDivMagicNumber= {0, 0}; |
| 122 const DivMagicNumbers DivMagicNumberFor3 = {0x55555556, 0}; |
| 123 const DivMagicNumbers DivMagicNumberFor5 = {0x66666667, 1}; |
| 124 const DivMagicNumbers DivMagicNumberFor7 = {0x92492493, 2}; |
| 125 const DivMagicNumbers DivMagicNumberFor9 = {0x38e38e39, 1}; |
| 126 const DivMagicNumbers DivMagicNumberFor11 = {0x2e8ba2e9, 1}; |
| 127 const DivMagicNumbers DivMagicNumberFor25 = {0x51eb851f, 3}; |
| 128 const DivMagicNumbers DivMagicNumberFor125 = {0x10624dd3, 3}; |
| 129 const DivMagicNumbers DivMagicNumberFor625 = {0x68db8bad, 8}; |
| 130 |
| 131 const DivMagicNumbers DivMagicNumberFor(int32_t divisor); |
| 132 |
| 133 |
108 // The C++ standard leaves the semantics of '>>' undefined for | 134 // The C++ standard leaves the semantics of '>>' undefined for |
109 // negative signed operands. Most implementations do the right thing, | 135 // negative signed operands. Most implementations do the right thing, |
110 // though. | 136 // though. |
111 inline int ArithmeticShiftRight(int x, int s) { | 137 inline int ArithmeticShiftRight(int x, int s) { |
112 return x >> s; | 138 return x >> s; |
113 } | 139 } |
114 | 140 |
115 | 141 |
116 // Compute the 0-relative offset of some absolute value x of type T. | 142 // Compute the 0-relative offset of some absolute value x of type T. |
117 // This allows conversion of Addresses and integral types into | 143 // This allows conversion of Addresses and integral types into |
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1202 iterator end() { return container_->end(); } | 1228 iterator end() { return container_->end(); } |
1203 reverse_iterator rbegin() { return container_->rbegin(); } | 1229 reverse_iterator rbegin() { return container_->rbegin(); } |
1204 reverse_iterator rend() { return container_->rend(); } | 1230 reverse_iterator rend() { return container_->rend(); } |
1205 private: | 1231 private: |
1206 C* container_; | 1232 C* container_; |
1207 }; | 1233 }; |
1208 | 1234 |
1209 } } // namespace v8::internal | 1235 } } // namespace v8::internal |
1210 | 1236 |
1211 #endif // V8_UTILS_H_ | 1237 #endif // V8_UTILS_H_ |
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