| // 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 |
