whesse@chromium.org | cec079d | 2010-03-22 14:44:04 +0000 | [diff] [blame] | 1 | // Copyright 2010 the V8 project authors. All rights reserved. |
| 2 | // Redistribution and use in source and binary forms, with or without |
| 3 | // modification, are permitted provided that the following conditions are |
| 4 | // met: |
| 5 | // |
| 6 | // * Redistributions of source code must retain the above copyright |
| 7 | // notice, this list of conditions and the following disclaimer. |
| 8 | // * Redistributions in binary form must reproduce the above |
| 9 | // copyright notice, this list of conditions and the following |
| 10 | // disclaimer in the documentation and/or other materials provided |
| 11 | // with the distribution. |
| 12 | // * Neither the name of Google Inc. nor the names of its |
| 13 | // contributors may be used to endorse or promote products derived |
| 14 | // from this software without specific prior written permission. |
| 15 | // |
| 16 | // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| 17 | // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| 18 | // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| 19 | // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| 20 | // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| 21 | // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| 22 | // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| 23 | // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| 24 | // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| 25 | // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| 26 | // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 27 | |
| 28 | #include "v8.h" |
| 29 | |
| 30 | #include "diy-fp.h" |
| 31 | |
| 32 | namespace v8 { |
| 33 | namespace internal { |
| 34 | |
| 35 | void DiyFp::Multiply(const DiyFp& other) { |
| 36 | // Simply "emulates" a 128 bit multiplication. |
| 37 | // However: the resulting number only contains 64 bits. The least |
| 38 | // significant 64 bits are only used for rounding the most significant 64 |
| 39 | // bits. |
| 40 | const uint64_t kM32 = 0xFFFFFFFFu; |
| 41 | uint64_t a = f_ >> 32; |
| 42 | uint64_t b = f_ & kM32; |
| 43 | uint64_t c = other.f_ >> 32; |
| 44 | uint64_t d = other.f_ & kM32; |
| 45 | uint64_t ac = a * c; |
| 46 | uint64_t bc = b * c; |
| 47 | uint64_t ad = a * d; |
| 48 | uint64_t bd = b * d; |
| 49 | uint64_t tmp = (bd >> 32) + (ad & kM32) + (bc & kM32); |
| 50 | // By adding 1U << 31 to tmp we round the final result. |
| 51 | // Halfway cases will be round up. |
| 52 | tmp += 1U << 31; |
| 53 | uint64_t result_f = ac + (ad >> 32) + (bc >> 32) + (tmp >> 32); |
| 54 | e_ += other.e_ + 64; |
| 55 | f_ = result_f; |
| 56 | } |
| 57 | |
| 58 | } } // namespace v8::internal |