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1 // Copyright 2010 the V8 project authors. All rights reserved. | |
2 // Redistribution and use in source and binary forms, with or without | |
3 // modification, are permitted provided that the following conditions are | |
4 // met: | |
5 // | |
6 // * Redistributions of source code must retain the above copyright | |
7 // notice, this list of conditions and the following disclaimer. | |
8 // * Redistributions in binary form must reproduce the above | |
9 // copyright notice, this list of conditions and the following | |
10 // disclaimer in the documentation and/or other materials provided | |
11 // with the distribution. | |
12 // * Neither the name of Google Inc. nor the names of its | |
13 // contributors may be used to endorse or promote products derived | |
14 // from this software without specific prior written permission. | |
15 // | |
16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS | |
17 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT | |
18 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR | |
19 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT | |
20 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, | |
21 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT | |
22 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
23 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
25 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE | |
26 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
27 | |
28 #ifndef V8_DIY_FP_H_ | |
29 #define V8_DIY_FP_H_ | |
30 | |
31 namespace v8 { | |
32 namespace internal { | |
33 | |
34 // This "Do It Yourself Floating Point" class implements a floating-point number | |
35 // with a uint64 significand and an int exponent. Normalized DiyFp numbers will | |
36 // have the most significant bit of the significand set. | |
37 // Multiplication and Subtraction do not normalize their results. | |
38 // DiyFp are not designed to contain special doubles (NaN and Infinity). | |
39 class DiyFp { | |
40 public: | |
41 static const int kSignificandSize = 64; | |
42 | |
43 DiyFp() : f_(0), e_(0) {} | |
44 DiyFp(uint64_t f, int e) : f_(f), e_(e) {} | |
45 | |
46 // this = this - other. | |
47 // The exponents of both numbers must be the same and the significand of this | |
48 // must be bigger than the significand of other. | |
49 // The result will not be normalized. | |
50 void Subtract(const DiyFp& other) { | |
51 ASSERT(e_ == other.e_); | |
52 ASSERT(f_ >= other.f_); | |
53 f_ -= other.f_; | |
54 } | |
55 | |
56 // Returns a - b. | |
57 // The exponents of both numbers must be the same and this must be bigger | |
58 // than other. The result will not be normalized. | |
59 static DiyFp Minus(const DiyFp& a, const DiyFp& b) { | |
60 DiyFp result = a; | |
61 result.Subtract(b); | |
62 return result; | |
63 } | |
64 | |
65 | |
66 // this = this * other. | |
67 void Multiply(const DiyFp& other); | |
68 | |
69 // returns a * b; | |
70 static DiyFp Times(const DiyFp& a, const DiyFp& b) { | |
71 DiyFp result = a; | |
72 result.Multiply(b); | |
73 return result; | |
74 } | |
75 | |
76 void Normalize() { | |
77 ASSERT(f_ != 0); | |
78 uint64_t f = f_; | |
79 int e = e_; | |
80 | |
81 // This method is mainly called for normalizing boundaries. In general | |
82 // boundaries need to be shifted by 10 bits. We thus optimize for this case. | |
83 const uint64_t k10MSBits = V8_2PART_UINT64_C(0xFFC00000, 00000000); | |
84 while ((f & k10MSBits) == 0) { | |
85 f <<= 10; | |
86 e -= 10; | |
87 } | |
88 while ((f & kUint64MSB) == 0) { | |
89 f <<= 1; | |
90 e--; | |
91 } | |
92 f_ = f; | |
93 e_ = e; | |
94 } | |
95 | |
96 static DiyFp Normalize(const DiyFp& a) { | |
97 DiyFp result = a; | |
98 result.Normalize(); | |
99 return result; | |
100 } | |
101 | |
102 uint64_t f() const { return f_; } | |
103 int e() const { return e_; } | |
104 | |
105 void set_f(uint64_t new_value) { f_ = new_value; } | |
106 void set_e(int new_value) { e_ = new_value; } | |
107 | |
108 private: | |
109 static const uint64_t kUint64MSB = V8_2PART_UINT64_C(0x80000000, 00000000); | |
110 | |
111 uint64_t f_; | |
112 int e_; | |
113 }; | |
114 | |
115 } } // namespace v8::internal | |
116 | |
117 #endif // V8_DIY_FP_H_ | |
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