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comparison: mfbt/double-conversion/diy-fp.cc
mfbt/double-conversion/diy-fp.cc
- branch
- TOR_BUG_9701
- changeset 14
- 925c144e1f1f
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| -1:000000000000 | 0:49f95a9f808f |
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| 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 | |
| 29 #include "diy-fp.h" | |
| 30 #include "utils.h" | |
| 31 | |
| 32 namespace double_conversion { | |
| 33 | |
| 34 void DiyFp::Multiply(const DiyFp& other) { | |
| 35 // Simply "emulates" a 128 bit multiplication. | |
| 36 // However: the resulting number only contains 64 bits. The least | |
| 37 // significant 64 bits are only used for rounding the most significant 64 | |
| 38 // bits. | |
| 39 const uint64_t kM32 = 0xFFFFFFFFU; | |
| 40 uint64_t a = f_ >> 32; | |
| 41 uint64_t b = f_ & kM32; | |
| 42 uint64_t c = other.f_ >> 32; | |
| 43 uint64_t d = other.f_ & kM32; | |
| 44 uint64_t ac = a * c; | |
| 45 uint64_t bc = b * c; | |
| 46 uint64_t ad = a * d; | |
| 47 uint64_t bd = b * d; | |
| 48 uint64_t tmp = (bd >> 32) + (ad & kM32) + (bc & kM32); | |
| 49 // By adding 1U << 31 to tmp we round the final result. | |
| 50 // Halfway cases will be round up. | |
| 51 tmp += 1U << 31; | |
| 52 uint64_t result_f = ac + (ad >> 32) + (bc >> 32) + (tmp >> 32); | |
| 53 e_ += other.e_ + 64; | |
| 54 f_ = result_f; | |
| 55 } | |
| 56 | |
| 57 } // namespace double_conversion |
