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27
28#include "../include/v8stdint.h"
29#include "globals.h"
30#include "checks.h"
31#include "diy-fp.h"
32
33namespace v8 {
34namespace internal {
35
36void DiyFp::Multiply(const DiyFp& other) {
37  // Simply "emulates" a 128 bit multiplication.
38  // However: the resulting number only contains 64 bits. The least
39  // significant 64 bits are only used for rounding the most significant 64
40  // bits.
41  const uint64_t kM32 = 0xFFFFFFFFu;
42  uint64_t a = f_ >> 32;
43  uint64_t b = f_ & kM32;
44  uint64_t c = other.f_ >> 32;
45  uint64_t d = other.f_ & kM32;
46  uint64_t ac = a * c;
47  uint64_t bc = b * c;
48  uint64_t ad = a * d;
49  uint64_t bd = b * d;
50  uint64_t tmp = (bd >> 32) + (ad & kM32) + (bc & kM32);
51  // By adding 1U << 31 to tmp we round the final result.
52  // Halfway cases will be round up.
53  tmp += 1U << 31;
54  uint64_t result_f = ac + (ad >> 32) + (bc >> 32) + (tmp >> 32);
55  e_ += other.e_ + 64;
56  f_ = result_f;
57}
58
59} }  // namespace v8::internal
60