| // Copyright 2011 the V8 project authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef V8_DIY_FP_H_ |
| #define V8_DIY_FP_H_ |
| |
| #include <stdint.h> |
| |
| #include "src/base/logging.h" |
| |
| namespace v8 { |
| namespace internal { |
| |
| // 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 are not designed to contain special doubles (NaN and Infinity). |
| class DiyFp { |
| public: |
| static const int kSignificandSize = 64; |
| |
| DiyFp() : f_(0), e_(0) {} |
| DiyFp(uint64_t f, int e) : f_(f), e_(e) {} |
| |
| // this = this - other. |
| // The exponents of both numbers must be the same and the significand of this |
| // must be bigger than the significand of other. |
| // The result will not be normalized. |
| void Subtract(const DiyFp& other) { |
| DCHECK(e_ == other.e_); |
| DCHECK(f_ >= other.f_); |
| f_ -= other.f_; |
| } |
| |
| // Returns a - b. |
| // The exponents of both numbers must be the same and this must be bigger |
| // than other. The result will not be normalized. |
| static DiyFp Minus(const DiyFp& a, const DiyFp& b) { |
| DiyFp result = a; |
| result.Subtract(b); |
| return result; |
| } |
| |
| |
| // this = this * other. |
| void Multiply(const DiyFp& other); |
| |
| // returns a * b; |
| static DiyFp Times(const DiyFp& a, const DiyFp& b) { |
| DiyFp result = a; |
| result.Multiply(b); |
| return result; |
| } |
| |
| void Normalize() { |
| DCHECK_NE(f_, 0); |
| uint64_t f = f_; |
| int e = e_; |
| |
| // This method is mainly called for normalizing boundaries. In general |
| // boundaries need to be shifted by 10 bits. We thus optimize for this case. |
| const uint64_t k10MSBits = static_cast<uint64_t>(0x3FF) << 54; |
| while ((f & k10MSBits) == 0) { |
| f <<= 10; |
| e -= 10; |
| } |
| while ((f & kUint64MSB) == 0) { |
| f <<= 1; |
| e--; |
| } |
| f_ = f; |
| e_ = e; |
| } |
| |
| static DiyFp Normalize(const DiyFp& a) { |
| DiyFp result = a; |
| result.Normalize(); |
| return result; |
| } |
| |
| uint64_t f() const { return f_; } |
| int e() const { return e_; } |
| |
| void set_f(uint64_t new_value) { f_ = new_value; } |
| void set_e(int new_value) { e_ = new_value; } |
| |
| private: |
| static const uint64_t kUint64MSB = static_cast<uint64_t>(1) << 63; |
| |
| uint64_t f_; |
| int e_; |
| }; |
| |
| } // namespace internal |
| } // namespace v8 |
| |
| #endif // V8_DIY_FP_H_ |