1 // Copyright 2011 the V8 project authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
6 #include "src/base/logging.h"
7 #include "src/diy-fp.h"
8 #include "src/globals.h"
13 void DiyFp::Multiply(const DiyFp& other) {
14 // Simply "emulates" a 128 bit multiplication.
15 // However: the resulting number only contains 64 bits. The least
16 // significant 64 bits are only used for rounding the most significant 64
18 const uint64_t kM32 = 0xFFFFFFFFu;
19 uint64_t a = f_ >> 32;
20 uint64_t b = f_ & kM32;
21 uint64_t c = other.f_ >> 32;
22 uint64_t d = other.f_ & kM32;
27 uint64_t tmp = (bd >> 32) + (ad & kM32) + (bc & kM32);
28 // By adding 1U << 31 to tmp we round the final result.
29 // Halfway cases will be round up.
31 uint64_t result_f = ac + (ad >> 32) + (bc >> 32) + (tmp >> 32);
36 } } // namespace v8::internal