1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/mfbt/double-conversion/diy-fp.cc Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,57 @@
1.4 +// Copyright 2010 the V8 project authors. All rights reserved.
1.5 +// Redistribution and use in source and binary forms, with or without
1.6 +// modification, are permitted provided that the following conditions are
1.7 +// met:
1.8 +//
1.9 +// * Redistributions of source code must retain the above copyright
1.10 +// notice, this list of conditions and the following disclaimer.
1.11 +// * Redistributions in binary form must reproduce the above
1.12 +// copyright notice, this list of conditions and the following
1.13 +// disclaimer in the documentation and/or other materials provided
1.14 +// with the distribution.
1.15 +// * Neither the name of Google Inc. nor the names of its
1.16 +// contributors may be used to endorse or promote products derived
1.17 +// from this software without specific prior written permission.
1.18 +//
1.19 +// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
1.20 +// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
1.21 +// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
1.22 +// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
1.23 +// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
1.24 +// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
1.25 +// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
1.26 +// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
1.27 +// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
1.28 +// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
1.29 +// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
1.30 +
1.31 +
1.32 +#include "diy-fp.h"
1.33 +#include "utils.h"
1.34 +
1.35 +namespace double_conversion {
1.36 +
1.37 +void DiyFp::Multiply(const DiyFp& other) {
1.38 + // Simply "emulates" a 128 bit multiplication.
1.39 + // However: the resulting number only contains 64 bits. The least
1.40 + // significant 64 bits are only used for rounding the most significant 64
1.41 + // bits.
1.42 + const uint64_t kM32 = 0xFFFFFFFFU;
1.43 + uint64_t a = f_ >> 32;
1.44 + uint64_t b = f_ & kM32;
1.45 + uint64_t c = other.f_ >> 32;
1.46 + uint64_t d = other.f_ & kM32;
1.47 + uint64_t ac = a * c;
1.48 + uint64_t bc = b * c;
1.49 + uint64_t ad = a * d;
1.50 + uint64_t bd = b * d;
1.51 + uint64_t tmp = (bd >> 32) + (ad & kM32) + (bc & kM32);
1.52 + // By adding 1U << 31 to tmp we round the final result.
1.53 + // Halfway cases will be round up.
1.54 + tmp += 1U << 31;
1.55 + uint64_t result_f = ac + (ad >> 32) + (bc >> 32) + (tmp >> 32);
1.56 + e_ += other.e_ + 64;
1.57 + f_ = result_f;
1.58 +}
1.59 +
1.60 +} // namespace double_conversion
