1 // Copyright 2011 the V8 project authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
10 #include "src/base/logging.h"
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).
22 static const int kSignificandSize = 64;
24 DiyFp() : f_(0), e_(0) {}
25 DiyFp(uint64_t f, int e) : f_(f), e_(e) {}
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) {
32 DCHECK(e_ == other.e_);
33 DCHECK(f_ >= other.f_);
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) {
47 // this = this * other.
48 void Multiply(const DiyFp& other);
51 static DiyFp Times(const DiyFp& a, const DiyFp& b) {
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.
64 const uint64_t k10MSBits = static_cast<uint64_t>(0x3FF) << 54;
65 while ((f & k10MSBits) == 0) {
69 while ((f & kUint64MSB) == 0) {
77 static DiyFp Normalize(const DiyFp& a) {
83 uint64_t f() const { return f_; }
84 int e() const { return e_; }
86 void set_f(uint64_t new_value) { f_ = new_value; }
87 void set_e(int new_value) { e_ = new_value; }
90 static const uint64_t kUint64MSB = static_cast<uint64_t>(1) << 63;
96 } } // namespace v8::internal
98 #endif // V8_DIY_FP_H_