// Copyright 2011 the V8 project authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. #include "src/diy-fp.h" #include <stdint.h> namespace v8 { namespace internal { 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 internal } // namespace v8