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1 // Copyright 2010 the V8 project authors. All rights reserved. | 1 // Copyright 2010 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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57 // The exponents of both numbers must be the same and this must be bigger | 57 // The exponents of both numbers must be the same and this must be bigger |
58 // than other. The result will not be normalized. | 58 // than other. The result will not be normalized. |
59 static DiyFp Minus(const DiyFp& a, const DiyFp& b) { | 59 static DiyFp Minus(const DiyFp& a, const DiyFp& b) { |
60 DiyFp result = a; | 60 DiyFp result = a; |
61 result.Subtract(b); | 61 result.Subtract(b); |
62 return result; | 62 return result; |
63 } | 63 } |
64 | 64 |
65 | 65 |
66 // this = this * other. | 66 // this = this * other. |
67 void Multiply(const DiyFp& other) { | 67 void Multiply(const DiyFp& other); |
68 // Simply "emulates" a 128 bit multiplication. | |
69 // However: the resulting number only contains 64 bits. The least | |
70 // significant 64 bits are only used for rounding the most significant 64 | |
71 // bits. | |
72 const uint64_t kM32 = 0xFFFFFFFFu; | |
73 uint64_t a = f_ >> 32; | |
74 uint64_t b = f_ & kM32; | |
75 uint64_t c = other.f_ >> 32; | |
76 uint64_t d = other.f_ & kM32; | |
77 uint64_t ac = a * c; | |
78 uint64_t bc = b * c; | |
79 uint64_t ad = a * d; | |
80 uint64_t bd = b * d; | |
81 uint64_t tmp = (bd >> 32) + (ad & kM32) + (bc & kM32); | |
82 tmp += 1U << 31; // round | |
83 uint64_t result_f = ac + (ad >> 32) + (bc >> 32) + (tmp >> 32); | |
84 e_ += other.e_ + 64; | |
85 f_ = result_f; | |
86 } | |
87 | 68 |
88 // returns a * b; | 69 // returns a * b; |
89 static DiyFp Times(const DiyFp& a, const DiyFp& b) { | 70 static DiyFp Times(const DiyFp& a, const DiyFp& b) { |
90 DiyFp result = a; | 71 DiyFp result = a; |
91 result.Multiply(b); | 72 result.Multiply(b); |
92 return result; | 73 return result; |
93 } | 74 } |
94 | 75 |
95 void Normalize() { | 76 void Normalize() { |
96 ASSERT(f_ != 0); | 77 ASSERT(f_ != 0); |
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127 private: | 108 private: |
128 static const uint64_t kUint64MSB = V8_2PART_UINT64_C(0x80000000, 00000000); | 109 static const uint64_t kUint64MSB = V8_2PART_UINT64_C(0x80000000, 00000000); |
129 | 110 |
130 uint64_t f_; | 111 uint64_t f_; |
131 int e_; | 112 int e_; |
132 }; | 113 }; |
133 | 114 |
134 } } // namespace v8::internal | 115 } } // namespace v8::internal |
135 | 116 |
136 #endif // V8_DIY_FP_H_ | 117 #endif // V8_DIY_FP_H_ |
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