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 "sim/host.hh"
  33
  34 /**
  35  * Private counter class for the internal saturating counters.
  36  * Implements an n bit saturating counter and provides methods to
  37  * increment, decrement, and read it.
  38  * @todo Consider making this something that more closely mimics a
  39  * built in class so you can use ++ or --.
  40  */
  41 class SatCounter
  42 {
  43   public:
  44     /**
  45      * Constructor for the counter.
  46      */
  47     SatCounter()
  48         : initialVal(0), counter(0)
  49     { }
  50
  51     /**
  52      * Constructor for the counter.
  53      * @param bits How many bits the counter will have.
  54      */
  55     SatCounter(unsigned bits)
  56         : initialVal(0), maxVal((1 << bits) - 1), counter(0)
  57     { }
  58
  59     /**
  60      * Constructor for the counter.
  61      * @param bits How many bits the counter will have.
  62      * @param initial_val Starting value for each counter.
  63      */
  64     SatCounter(unsigned bits, uint8_t initial_val)
  65         : initialVal(initialVal), maxVal((1 << bits) - 1), counter(initial_val)
  66     {
  67         // Check to make sure initial value doesn't exceed the max
  68         // counter value.
  69         if (initial_val > maxVal) {
  70             fatal("BP: Initial counter value exceeds max size.");
  71         }
  72     }
  73
  74     /**
  75      * Sets the number of bits.
  76      */
  77     void setBits(unsigned bits) { maxVal = (1 << bits) - 1; }
  78
  79     void reset() { counter = initialVal; }
  80
  81     /**
  82      * Increments the counter's current value.
  83      */
  84     void increment()
  85     {
  86         if (counter < maxVal) {
  87             ++counter;
  88         }
  89     }
  90
  91     /**
  92      * Decrements the counter's current value.
  93      */
  94     void decrement()
  95     {
  96         if (counter > 0) {
  97             --counter;
  98         }
  99     }
 100
 101     /**
 102      * Read the counter's value.
 103      */
 104     const uint8_t read() const
 105     { return counter; }
 106
 107   private:
 108     uint8_t initialVal;
 109     uint8_t maxVal;
 110     uint8_t counter;
 111 };
 112
 113 #endif // __CPU_O3_SAT_COUNTER_HH__