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 // Copyright 2010 the V8 project authors. All rights reserved.

 // Redistribution and use in source and binary forms, with or without

 // modification, are permitted provided that the following conditions are

 // met:

 //

 //     * Redistributions of source code must retain the above copyright

 //       notice, this list of conditions and the following disclaimer.

 //     * Redistributions in binary form must reproduce the above

 //       copyright notice, this list of conditions and the following

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 //       with the distribution.

 //     * Neither the name of Google Inc. nor the names of its

 //       contributors may be used to endorse or promote products derived

 //       from this software without specific prior written permission.

 //

 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

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 #include "diy-fp.h"

 #include "utils.h"

 namespace double_conversion {

 void DiyFp::Multiply(const DiyFp& other) {

   // Simply "emulates" a 128 bit multiplication.

   // However: the resulting number only contains 64 bits. The least

   // significant 64 bits are only used for rounding the most significant 64

   // bits.

   const uint64_t kM32 = 0xFFFFFFFFU;

   uint64_t a = f_ >> 32;

   uint64_t b = f_ & kM32;

   uint64_t c = other.f_ >> 32;

   uint64_t d = other.f_ & kM32;

   uint64_t ac = a * c;

   uint64_t bc = b * c;

   uint64_t ad = a * d;

   uint64_t bd = b * d;

   uint64_t tmp = (bd >> 32) + (ad & kM32) + (bc & kM32);

   // By adding 1U << 31 to tmp we round the final result.

   // Halfway cases will be round up.

   tmp += 1U << 31;

   uint64_t result_f = ac + (ad >> 32) + (bc >> 32) + (tmp >> 32);

   e_ += other.e_ + 64;

   f_ = result_f;

 }

 }  // namespace double_conversion