58 lines
2.4 KiB
C++
58 lines
2.4 KiB
C++
// 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
|
|
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
|
|
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
|
|
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
|
|
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
|
|
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
|
|
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
|
|
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
|
|
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
|
|
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
|
|
|
|
|
#include "diy-fp.h"
|
|
#include "utils.h"
|
|
|
|
namespace double_conversion {
|
|
|
|
void DiyFp::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;
|
|
uint64_t a = f_ >> 32;
|
|
uint64_t b = f_ & kM32;
|
|
uint64_t c = other.f_ >> 32;
|
|
uint64_t d = other.f_ & kM32;
|
|
uint64_t ac = a * c;
|
|
uint64_t bc = b * c;
|
|
uint64_t ad = a * d;
|
|
uint64_t bd = b * d;
|
|
uint64_t tmp = (bd >> 32) + (ad & kM32) + (bc & kM32);
|
|
// By adding 1U << 31 to tmp we round the final result.
|
|
// Halfway cases will be round up.
|
|
tmp += 1U << 31;
|
|
uint64_t result_f = ac + (ad >> 32) + (bc >> 32) + (tmp >> 32);
|
|
e_ += other.e_ + 64;
|
|
f_ = result_f;
|
|
}
|
|
|
|
} // namespace double_conversion
|