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 // 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_NUMBERS_DIY_FP_H_ #define V8_NUMBERS_DIY_FP_H_ #include #include "src/base/logging.h" #include "src/base/macros.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. V8_EXPORT_PRIVATE 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(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(1) << 63; uint64_t f_; int e_; }; } // namespace internal } // namespace v8 #endif // V8_NUMBERS_DIY_FP_H_