whesse@chromium.org | cec079d | 2010-03-22 14:44:04 +0000 | [diff] [blame] | 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_ |