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