| // Copyright 2010 the V8 project authors. All rights reserved. |
| // Redistribution and use in source and binary forms, with or without |
| // modification, are permitted provided that the following conditions are |
| // met: |
| // |
| // * Redistributions of source code must retain the above copyright |
| // notice, this list of conditions and the following disclaimer. |
| // * Redistributions in binary form must reproduce the above |
| // copyright notice, this list of conditions and the following |
| // disclaimer in the documentation and/or other materials provided |
| // with the distribution. |
| // * Neither the name of Google Inc. nor the names of its |
| // contributors may be used to endorse or promote products derived |
| // from this software without specific prior written permission. |
| // |
| // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
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| // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| |
| #ifndef DOUBLE_CONVERSION_DIY_FP_H_ |
| #define DOUBLE_CONVERSION_DIY_FP_H_ |
| |
| #include "utils.h" |
| |
| namespace double_conversion { |
| |
| // This "Do It Yourself Floating Point" class implements a floating-point number |
| // with a uint64 significand and an int exponent. Normalized DiyFp numbers will |
| // have the most significant bit of the significand set. |
| // Multiplication and Subtraction do not normalize their results. |
| // DiyFp store only non-negative numbers and are not designed to contain special |
| // doubles (NaN and Infinity). |
| class DiyFp { |
| public: |
| static const int kSignificandSize = 64; |
| |
| DiyFp() : f_(0), e_(0) {} |
| DiyFp(const uint64_t significand, const int32_t exponent) : f_(significand), e_(exponent) {} |
| |
| // this -= other. |
| // The exponents of both numbers must be the same and the significand of this |
| // must be greater or equal than the significand of other. |
| // The result will not be normalized. |
| void Subtract(const DiyFp& other) { |
| DOUBLE_CONVERSION_ASSERT(e_ == other.e_); |
| DOUBLE_CONVERSION_ASSERT(f_ >= other.f_); |
| f_ -= other.f_; |
| } |
| |
| // Returns a - b. |
| // The exponents of both numbers must be the same and a must be greater |
| // or equal than b. The result will not be normalized. |
| static DiyFp Minus(const DiyFp& a, const DiyFp& b) { |
| DiyFp result = a; |
| result.Subtract(b); |
| return result; |
| } |
| |
| // this *= other. |
| void Multiply(const DiyFp& other) { |
| // Simply "emulates" a 128 bit multiplication. |
| // However: the resulting number only contains 64 bits. The least |
| // significant 64 bits are only used for rounding the most significant 64 |
| // bits. |
| const uint64_t kM32 = 0xFFFFFFFFU; |
| const uint64_t a = f_ >> 32; |
| const uint64_t b = f_ & kM32; |
| const uint64_t c = other.f_ >> 32; |
| const uint64_t d = other.f_ & kM32; |
| const uint64_t ac = a * c; |
| const uint64_t bc = b * c; |
| const uint64_t ad = a * d; |
| const uint64_t bd = b * d; |
| // By adding 1U << 31 to tmp we round the final result. |
| // Halfway cases will be rounded up. |
| const uint64_t tmp = (bd >> 32) + (ad & kM32) + (bc & kM32) + (1U << 31); |
| e_ += other.e_ + 64; |
| f_ = ac + (ad >> 32) + (bc >> 32) + (tmp >> 32); |
| } |
| |
| // returns a * b; |
| static DiyFp Times(const DiyFp& a, const DiyFp& b) { |
| DiyFp result = a; |
| result.Multiply(b); |
| return result; |
| } |
| |
| void Normalize() { |
| DOUBLE_CONVERSION_ASSERT(f_ != 0); |
| uint64_t significand = f_; |
| int32_t exponent = e_; |
| |
| // This method is mainly called for normalizing boundaries. In general, |
| // boundaries need to be shifted by 10 bits, and we optimize for this case. |
| const uint64_t k10MSBits = DOUBLE_CONVERSION_UINT64_2PART_C(0xFFC00000, 00000000); |
| while ((significand & k10MSBits) == 0) { |
| significand <<= 10; |
| exponent -= 10; |
| } |
| while ((significand & kUint64MSB) == 0) { |
| significand <<= 1; |
| exponent--; |
| } |
| f_ = significand; |
| e_ = exponent; |
| } |
| |
| static DiyFp Normalize(const DiyFp& a) { |
| DiyFp result = a; |
| result.Normalize(); |
| return result; |
| } |
| |
| uint64_t f() const { return f_; } |
| int32_t e() const { return e_; } |
| |
| void set_f(uint64_t new_value) { f_ = new_value; } |
| void set_e(int32_t new_value) { e_ = new_value; } |
| |
| private: |
| static const uint64_t kUint64MSB = DOUBLE_CONVERSION_UINT64_2PART_C(0x80000000, 00000000); |
| |
| uint64_t f_; |
| int32_t e_; |
| }; |
| |
| } // namespace double_conversion |
| |
| #endif // DOUBLE_CONVERSION_DIY_FP_H_ |