ftl/FTLWeight.h

   1 /*
   2  * Copyright (C) 2014 Apple Inc. All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
  14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  16  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
  17  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  18  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  20  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  21  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #ifndef FTLWeight_h
  27 #define FTLWeight_h
  28
  29 #if ENABLE(FTL_JIT)
  30
  31 #include <wtf/MathExtras.h>
  32 #include <wtf/StdLibExtras.h>
  33
  34 namespace JSC { namespace FTL {
  35
  36 class Weight {
  37 public:
  38     Weight()
  39         : m_value(std::numeric_limits<float>::quiet_NaN())
  40     {
  41     }
  42
  43     explicit Weight(float value)
  44         : m_value(value)
  45     {
  46     }
  47
  48     bool isSet() const { return m_value == m_value; }
  49     bool operator!() const { return !isSet(); }
  50
  51     float value() const { return m_value; }
  52
  53     unsigned scaleToTotal(double total) const
  54     {
  55         // LLVM accepts 32-bit unsigned branch weights but in dumps it might display them
  56         // as signed values. We don't need all 32 bits, so we just use the 31 bits.
  57         double result = static_cast<double>(m_value) * INT_MAX / total;
  58         if (result < 0)
  59             return 0;
  60         if (result > INT_MAX)
  61             return INT_MAX;
  62         return static_cast<unsigned>(result);
  63     }
  64
  65     // Inverse weight for a two-target branch.
  66     Weight inverse() const
  67     {
  68         if (!isSet())
  69             return Weight();
  70         if (value())
  71             return Weight(0);
  72         return Weight(1);
  73     }
  74
  75 private:
  76     float m_value;
  77 };
  78
  79 } } // namespace JSC::FTL
  80
  81 #endif // ENABLE(FTL_JIT)
  82
  83 #endif // FTLWeight_h
  84