1 : // Copyright 2010 the V8 project authors. All rights reserved.
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3 : // modification, are permitted provided that the following conditions are
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8 : // * Redistributions in binary form must reproduce the above
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27 :
28 : #include "v8.h"
29 :
30 : #include "diy-fp.h"
31 :
32 : namespace v8 {
33 : namespace internal {
34 :
35 772005 : 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 772005 : const uint64_t kM32 = 0xFFFFFFFFu;
41 772005 : uint64_t a = f_ >> 32;
42 772005 : uint64_t b = f_ & kM32;
43 772005 : uint64_t c = other.f_ >> 32;
44 772005 : uint64_t d = other.f_ & kM32;
45 772005 : uint64_t ac = a * c;
46 772005 : uint64_t bc = b * c;
47 772005 : uint64_t ad = a * d;
48 772005 : uint64_t bd = b * d;
49 772005 : 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 772005 : tmp += 1U << 31;
53 772005 : uint64_t result_f = ac + (ad >> 32) + (bc >> 32) + (tmp >> 32);
54 772005 : e_ += other.e_ + 64;
55 772005 : f_ = result_f;
56 772005 : }
57 :
58 : } } // namespace v8::internal
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