Ben Murdoch | 3fb3ca8 | 2011-12-02 17:19:32 +0000 | [diff] [blame] | 1 | // Copyright 2011 the V8 project authors. All rights reserved. |
Ben Murdoch | b8a8cc1 | 2014-11-26 15:28:44 +0000 | [diff] [blame] | 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. |
Steve Block | 6ded16b | 2010-05-10 14:33:55 +0100 | [diff] [blame] | 4 | |
| 5 | #ifndef V8_DIY_FP_H_ |
| 6 | #define V8_DIY_FP_H_ |
| 7 | |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 8 | #include <stdint.h> |
| 9 | |
| 10 | #include "src/base/logging.h" |
| 11 | |
Steve Block | 6ded16b | 2010-05-10 14:33:55 +0100 | [diff] [blame] | 12 | namespace v8 { |
| 13 | namespace internal { |
| 14 | |
| 15 | // This "Do It Yourself Floating Point" class implements a floating-point number |
| 16 | // with a uint64 significand and an int exponent. Normalized DiyFp numbers will |
| 17 | // have the most significant bit of the significand set. |
| 18 | // Multiplication and Subtraction do not normalize their results. |
| 19 | // DiyFp are not designed to contain special doubles (NaN and Infinity). |
| 20 | class DiyFp { |
| 21 | public: |
| 22 | static const int kSignificandSize = 64; |
| 23 | |
| 24 | DiyFp() : f_(0), e_(0) {} |
| 25 | DiyFp(uint64_t f, int e) : f_(f), e_(e) {} |
| 26 | |
| 27 | // this = this - other. |
| 28 | // The exponents of both numbers must be the same and the significand of this |
| 29 | // must be bigger than the significand of other. |
| 30 | // The result will not be normalized. |
| 31 | void Subtract(const DiyFp& other) { |
Ben Murdoch | b8a8cc1 | 2014-11-26 15:28:44 +0000 | [diff] [blame] | 32 | DCHECK(e_ == other.e_); |
| 33 | DCHECK(f_ >= other.f_); |
Steve Block | 6ded16b | 2010-05-10 14:33:55 +0100 | [diff] [blame] | 34 | f_ -= other.f_; |
| 35 | } |
| 36 | |
| 37 | // Returns a - b. |
| 38 | // The exponents of both numbers must be the same and this must be bigger |
| 39 | // than other. The result will not be normalized. |
| 40 | static DiyFp Minus(const DiyFp& a, const DiyFp& b) { |
| 41 | DiyFp result = a; |
| 42 | result.Subtract(b); |
| 43 | return result; |
| 44 | } |
| 45 | |
| 46 | |
| 47 | // this = this * other. |
| 48 | void Multiply(const DiyFp& other); |
| 49 | |
| 50 | // returns a * b; |
| 51 | static DiyFp Times(const DiyFp& a, const DiyFp& b) { |
| 52 | DiyFp result = a; |
| 53 | result.Multiply(b); |
| 54 | return result; |
| 55 | } |
| 56 | |
| 57 | void Normalize() { |
Ben Murdoch | b8a8cc1 | 2014-11-26 15:28:44 +0000 | [diff] [blame] | 58 | DCHECK(f_ != 0); |
Steve Block | 6ded16b | 2010-05-10 14:33:55 +0100 | [diff] [blame] | 59 | uint64_t f = f_; |
| 60 | int e = e_; |
| 61 | |
| 62 | // This method is mainly called for normalizing boundaries. In general |
| 63 | // boundaries need to be shifted by 10 bits. We thus optimize for this case. |
Ben Murdoch | 3fb3ca8 | 2011-12-02 17:19:32 +0000 | [diff] [blame] | 64 | const uint64_t k10MSBits = static_cast<uint64_t>(0x3FF) << 54; |
Steve Block | 6ded16b | 2010-05-10 14:33:55 +0100 | [diff] [blame] | 65 | while ((f & k10MSBits) == 0) { |
| 66 | f <<= 10; |
| 67 | e -= 10; |
| 68 | } |
| 69 | while ((f & kUint64MSB) == 0) { |
| 70 | f <<= 1; |
| 71 | e--; |
| 72 | } |
| 73 | f_ = f; |
| 74 | e_ = e; |
| 75 | } |
| 76 | |
| 77 | static DiyFp Normalize(const DiyFp& a) { |
| 78 | DiyFp result = a; |
| 79 | result.Normalize(); |
| 80 | return result; |
| 81 | } |
| 82 | |
| 83 | uint64_t f() const { return f_; } |
| 84 | int e() const { return e_; } |
| 85 | |
| 86 | void set_f(uint64_t new_value) { f_ = new_value; } |
| 87 | void set_e(int new_value) { e_ = new_value; } |
| 88 | |
| 89 | private: |
Ben Murdoch | 3fb3ca8 | 2011-12-02 17:19:32 +0000 | [diff] [blame] | 90 | static const uint64_t kUint64MSB = static_cast<uint64_t>(1) << 63; |
Steve Block | 6ded16b | 2010-05-10 14:33:55 +0100 | [diff] [blame] | 91 | |
| 92 | uint64_t f_; |
| 93 | int e_; |
| 94 | }; |
| 95 | |
Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 96 | } // namespace internal |
| 97 | } // namespace v8 |
Steve Block | 6ded16b | 2010-05-10 14:33:55 +0100 | [diff] [blame] | 98 | |
| 99 | #endif // V8_DIY_FP_H_ |