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1 // Copyright 2011 the V8 project authors. All rights reserved. | 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 | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
| 5 #include "src/diy-fp.h" |
| 6 |
5 #include <stdint.h> | 7 #include <stdint.h> |
6 #include "src/base/logging.h" | |
7 #include "src/diy-fp.h" | |
8 #include "src/globals.h" | |
9 | 8 |
10 namespace v8 { | 9 namespace v8 { |
11 namespace internal { | 10 namespace internal { |
12 | 11 |
13 void DiyFp::Multiply(const DiyFp& other) { | 12 void DiyFp::Multiply(const DiyFp& other) { |
14 // Simply "emulates" a 128 bit multiplication. | 13 // Simply "emulates" a 128 bit multiplication. |
15 // However: the resulting number only contains 64 bits. The least | 14 // However: the resulting number only contains 64 bits. The least |
16 // significant 64 bits are only used for rounding the most significant 64 | 15 // significant 64 bits are only used for rounding the most significant 64 |
17 // bits. | 16 // bits. |
18 const uint64_t kM32 = 0xFFFFFFFFu; | 17 const uint64_t kM32 = 0xFFFFFFFFu; |
19 uint64_t a = f_ >> 32; | 18 uint64_t a = f_ >> 32; |
20 uint64_t b = f_ & kM32; | 19 uint64_t b = f_ & kM32; |
21 uint64_t c = other.f_ >> 32; | 20 uint64_t c = other.f_ >> 32; |
22 uint64_t d = other.f_ & kM32; | 21 uint64_t d = other.f_ & kM32; |
23 uint64_t ac = a * c; | 22 uint64_t ac = a * c; |
24 uint64_t bc = b * c; | 23 uint64_t bc = b * c; |
25 uint64_t ad = a * d; | 24 uint64_t ad = a * d; |
26 uint64_t bd = b * d; | 25 uint64_t bd = b * d; |
27 uint64_t tmp = (bd >> 32) + (ad & kM32) + (bc & kM32); | 26 uint64_t tmp = (bd >> 32) + (ad & kM32) + (bc & kM32); |
28 // By adding 1U << 31 to tmp we round the final result. | 27 // By adding 1U << 31 to tmp we round the final result. |
29 // Halfway cases will be round up. | 28 // Halfway cases will be round up. |
30 tmp += 1U << 31; | 29 tmp += 1U << 31; |
31 uint64_t result_f = ac + (ad >> 32) + (bc >> 32) + (tmp >> 32); | 30 uint64_t result_f = ac + (ad >> 32) + (bc >> 32) + (tmp >> 32); |
32 e_ += other.e_ + 64; | 31 e_ += other.e_ + 64; |
33 f_ = result_f; | 32 f_ = result_f; |
34 } | 33 } |
35 | 34 |
36 } // namespace internal | 35 } // namespace internal |
37 } // namespace v8 | 36 } // namespace v8 |
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