src/cpu/o3/sat_counter.hh

   1 /*
   2  * Copyright (c) 2005-2006 The Regents of The University of Michigan
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions are
   7  * met: redistributions of source code must retain the above copyright
   8  * notice, this list of conditions and the following disclaimer;
   9  * 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  * neither the name of the copyright holders nor the names of its
  13  * contributors may be used to endorse or promote products derived from
  14  * this software without specific prior written permission.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  17  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  18  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  19  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  20  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  21  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  22  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  26  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 #ifndef __CPU_O3_SAT_COUNTER_HH__
  30 #define __CPU_O3_SAT_COUNTER_HH__
  31
  32 #include "base/misc.hh"
  33 #include "sim/host.hh"
  34
  35 /**
  36  * Private counter class for the internal saturating counters.
  37  * Implements an n bit saturating counter and provides methods to
  38  * increment, decrement, and read it.
  39  * @todo Consider making this something that more closely mimics a
  40  * built in class so you can use ++ or --.
  41  */
  42 class SatCounter
  43 {
  44   public:
  45     /**
  46      * Constructor for the counter.
  47      */
  48     SatCounter()
  49         : initialVal(0), counter(0)
  50     { }
  51
  52     /**
  53      * Constructor for the counter.
  54      * @param bits How many bits the counter will have.
  55      */
  56     SatCounter(unsigned bits)
  57         : initialVal(0), maxVal((1 << bits) - 1), counter(0)
  58     { }
  59
  60     /**
  61      * Constructor for the counter.
  62      * @param bits How many bits the counter will have.
  63      * @param initial_val Starting value for each counter.
  64      */
  65     SatCounter(unsigned bits, uint8_t initial_val)
  66         : initialVal(initialVal), maxVal((1 << bits) - 1), counter(initial_val)
  67     {
  68         // Check to make sure initial value doesn't exceed the max
  69         // counter value.
  70         if (initial_val > maxVal) {
  71             fatal("BP: Initial counter value exceeds max size.");
  72         }
  73     }
  74
  75     /**
  76      * Sets the number of bits.
  77      */
  78     void setBits(unsigned bits) { maxVal = (1 << bits) - 1; }
  79
  80     void reset() { counter = initialVal; }
  81
  82     /**
  83      * Increments the counter's current value.
  84      */
  85     void increment()
  86     {
  87         if (counter < maxVal) {
  88             ++counter;
  89         }
  90     }
  91
  92     /**
  93      * Decrements the counter's current value.
  94      */
  95     void decrement()
  96     {
  97         if (counter > 0) {
  98             --counter;
  99         }
 100     }
 101
 102     /**
 103      * Read the counter's value.
 104      */
 105     const uint8_t read() const
 106     { return counter; }
 107
 108   private:
 109     uint8_t initialVal;
 110     uint8_t maxVal;
 111     uint8_t counter;
 112 };
 113
 114 #endif // __CPU_O3_SAT_COUNTER_HH__