src/base/sat_counter.hh - public/gem5 - Git at Google

 /*
  * Copyright (c) 2019 Inria
  * All rights reserved.
  *
  * The license below extends only to copyright in the software and shall
  * not be construed as granting a license to any other intellectual
  * property including but not limited to intellectual property relating
  * to a hardware implementation of the functionality of the software
  * licensed hereunder.  You may use the software subject to the license
  * terms below provided that you ensure that this notice is replicated
  * unmodified and in its entirety in all distributions of the software,
  * modified or unmodified, in source code or in binary form.
  *
  * Copyright (c) 2005-2006 The Regents of The University of Michigan
  * 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 disclaimer in the
  * documentation and/or other materials provided with the distribution;
  * neither the name of the copyright holders 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
  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #ifndef __BASE_SAT_COUNTER_HH__
 #define __BASE_SAT_COUNTER_HH__

 #include <cassert>
 #include <cstdint>

 #include "base/logging.hh"
 #include "base/types.hh"

 /**
  * Implements an n bit saturating counter and provides methods to
  * increment, decrement, and read it.
  */
 class SatCounter
 {
   public:
     /** The default constructor should never be used. */
     SatCounter() = delete;

     /**
      * Constructor for the counter. The explicit keyword is used to make
      * sure the user does not assign a number to the counter thinking it
      * will be used as a counter value when it is in fact used as the number
      * of bits.
      *
      * @param bits How many bits the counter will have.
      * @param initial_val Starting value for the counter.
      *
      * @ingroup api_sat_counter
      */
     explicit SatCounter(unsigned bits, uint8_t initial_val = 0)
         : initialVal(initial_val), maxVal((1 << bits) - 1),
           counter(initial_val)
     {
         fatal_if(bits > 8*sizeof(uint8_t),
                  "Number of bits exceeds counter size");
         fatal_if(initial_val > maxVal,
                  "Saturating counter's Initial value exceeds max value.");
     }

     /**
      * Copy constructor.
      *
      * @ingroup api_sat_counter
      */
     SatCounter(const SatCounter& other)
         : initialVal(other.initialVal), maxVal(other.maxVal),
           counter(other.counter)
     {
     }

     /**
      * Copy assignment.
      *
      * @ingroup api_sat_counter
      */
     SatCounter& operator=(const SatCounter& other) {
         if (this != &other) {
             SatCounter temp(other);
             this->swap(temp);
         }
         return *this;
     }

     /**
      * Move constructor.
      *
      * @ingroup api_sat_counter
      */
     SatCounter(SatCounter&& other)
     {
         initialVal = other.initialVal;
         maxVal = other.maxVal;
         counter = other.counter;
         SatCounter temp(0);
         other.swap(temp);
     }

     /**
      * Move assignment.
      *
      * @ingroup api_sat_counter
      */
     SatCounter& operator=(SatCounter&& other) {
         if (this != &other) {
             initialVal = other.initialVal;
             maxVal = other.maxVal;
             counter = other.counter;
             SatCounter temp(0);
             other.swap(temp);
         }
         return *this;
     }

     /**
      * Swap the contents of every member of the class. Used for the default
      * copy-assignment created by the compiler.
      *
      * @param other The other object to swap contents with.
      *
      * @ingroup api_sat_counter
      */
     void
     swap(SatCounter& other)
     {
         std::swap(initialVal, other.initialVal);
         std::swap(maxVal, other.maxVal);
         std::swap(counter, other.counter);
     }

     /**
      * Pre-increment operator.
      *
      * @ingroup api_sat_counter
      */
     SatCounter&
     operator++()
     {
         if (counter < maxVal) {
             ++counter;
         }
         return *this;
     }

     /**
      * Post-increment operator.
      *
      * @ingroup api_sat_counter
      */
     SatCounter
     operator++(int)
     {
         SatCounter old_counter = *this;
         ++*this;
         return old_counter;
     }

     /**
      * Pre-decrement operator.
      *
      * @ingroup api_sat_counter
      */
     SatCounter&
     operator--()
     {
         if (counter > 0) {
             --counter;
         }
         return *this;
     }

     /**
      * Post-decrement operator.
      *
      * @ingroup api_sat_counter
      */
     SatCounter
     operator--(int)
     {
         SatCounter old_counter = *this;
         --*this;
         return old_counter;
     }

     /**
      * Shift-right-assignment.
      *
      * @ingroup api_sat_counter
      */
     SatCounter&
     operator>>=(const int& shift)
     {
         assert(shift >= 0);
         this->counter >>= shift;
         return *this;
     }

     /**
      * Shift-left-assignment.
      *
      * @ingroup api_sat_counter
      */
     SatCounter&
     operator<<=(const int& shift)
     {
         assert(shift >= 0);
         this->counter <<= shift;
         if (this->counter > maxVal) {
             this->counter = maxVal;
         }
         return *this;
     }

     /**
      * Add-assignment.
      *
      * @ingroup api_sat_counter
      */
     SatCounter&
     operator+=(const int& value)
     {
         if (value >= 0) {
             if (maxVal - this->counter >= value) {
                 this->counter += value;
             } else {
                 this->counter = maxVal;
             }
         } else {
             *this -= -value;
         }
         return *this;
     }

     /**
      * Subtract-assignment.
      *
      * @ingroup api_sat_counter
      */
     SatCounter&
     operator-=(const int& value)
     {
         if (value >= 0) {
             if (this->counter > value) {
                 this->counter -= value;
             } else {
                 this->counter = 0;
             }
         } else {
             *this += -value;
         }
         return *this;
     }

     /**
      * Read the counter's value.
      *
      * @ingroup api_sat_counter
      */
     operator uint8_t() const { return counter; }

     /**
      * Reset the counter to its initial value.
      *
      * @ingroup api_sat_counter
      */
     void reset() { counter = initialVal; }

     /**
      * Calculate saturation percentile of the current counter's value
      * with regard to its maximum possible value.
      *
      * @return A value between 0.0 and 1.0 to indicate which percentile of
      *         the maximum value the current value is.
      *
      * @ingroup api_sat_counter
      */
     double calcSaturation() const { return (double) counter / maxVal; }

     /**
      * Whether the counter has achieved its maximum value or not.
      *
      * @return True if the counter saturated.
      *
      * @ingroup api_sat_counter
      */
     bool isSaturated() const { return counter == maxVal; }

     /**
      * Saturate the counter.
      *
      * @return The value added to the counter to reach saturation.
      *
      * @ingroup api_sat_counter
      */
     uint8_t saturate()
     {
         const uint8_t diff = maxVal - counter;
         counter = maxVal;
         return diff;
     }

   private:
     uint8_t initialVal;
     uint8_t maxVal;
     uint8_t counter;
 };

 #endif // __BASE_SAT_COUNTER_HH__
	/*
	* Copyright (c) 2019 Inria
	* All rights reserved.
	*
	* The license below extends only to copyright in the software and shall
	* not be construed as granting a license to any other intellectual
	* property including but not limited to intellectual property relating
	* to a hardware implementation of the functionality of the software
	* licensed hereunder. You may use the software subject to the license
	* terms below provided that you ensure that this notice is replicated
	* unmodified and in its entirety in all distributions of the software,
	* modified or unmodified, in source code or in binary form.
	*
	* Copyright (c) 2005-2006 The Regents of The University of Michigan
	* 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 disclaimer in the
	* documentation and/or other materials provided with the distribution;
	* neither the name of the copyright holders 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
	* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
	* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#ifndef __BASE_SAT_COUNTER_HH__
	#define __BASE_SAT_COUNTER_HH__

	#include <cassert>
	#include <cstdint>

	#include "base/logging.hh"
	#include "base/types.hh"

	/**
	* Implements an n bit saturating counter and provides methods to
	* increment, decrement, and read it.
	*/
	class SatCounter
	{
	public:
	/** The default constructor should never be used. */
	SatCounter() = delete;

	/**
	* Constructor for the counter. The explicit keyword is used to make
	* sure the user does not assign a number to the counter thinking it
	* will be used as a counter value when it is in fact used as the number
	* of bits.
	*
	* @param bits How many bits the counter will have.
	* @param initial_val Starting value for the counter.
	*
	* @ingroup api_sat_counter
	*/
	explicit SatCounter(unsigned bits, uint8_t initial_val = 0)
	: initialVal(initial_val), maxVal((1 << bits) - 1),
	counter(initial_val)
	{
	fatal_if(bits > 8*sizeof(uint8_t),
	"Number of bits exceeds counter size");
	fatal_if(initial_val > maxVal,
	"Saturating counter's Initial value exceeds max value.");
	}

	/**
	* Copy constructor.
	*
	* @ingroup api_sat_counter
	*/
	SatCounter(const SatCounter& other)
	: initialVal(other.initialVal), maxVal(other.maxVal),
	counter(other.counter)
	{
	}

	/**
	* Copy assignment.
	*
	* @ingroup api_sat_counter
	*/
	SatCounter& operator=(const SatCounter& other) {
	if (this != &other) {
	SatCounter temp(other);
	this->swap(temp);
	}
	return *this;
	}

	/**
	* Move constructor.
	*
	* @ingroup api_sat_counter
	*/
	SatCounter(SatCounter&& other)
	{
	initialVal = other.initialVal;
	maxVal = other.maxVal;
	counter = other.counter;
	SatCounter temp(0);
	other.swap(temp);
	}

	/**
	* Move assignment.
	*
	* @ingroup api_sat_counter
	*/
	SatCounter& operator=(SatCounter&& other) {
	if (this != &other) {
	initialVal = other.initialVal;
	maxVal = other.maxVal;
	counter = other.counter;
	SatCounter temp(0);
	other.swap(temp);
	}
	return *this;
	}

	/**
	* Swap the contents of every member of the class. Used for the default
	* copy-assignment created by the compiler.
	*
	* @param other The other object to swap contents with.
	*
	* @ingroup api_sat_counter
	*/
	void
	swap(SatCounter& other)
	{
	std::swap(initialVal, other.initialVal);
	std::swap(maxVal, other.maxVal);
	std::swap(counter, other.counter);
	}

	/**
	* Pre-increment operator.
	*
	* @ingroup api_sat_counter
	*/
	SatCounter&
	operator++()
	{
	if (counter < maxVal) {
	++counter;
	}
	return *this;
	}

	/**
	* Post-increment operator.
	*
	* @ingroup api_sat_counter
	*/
	SatCounter
	operator++(int)
	{
	SatCounter old_counter = *this;
	++*this;
	return old_counter;
	}

	/**
	* Pre-decrement operator.
	*
	* @ingroup api_sat_counter
	*/
	SatCounter&
	operator--()
	{
	if (counter > 0) {
	--counter;
	}
	return *this;
	}

	/**
	* Post-decrement operator.
	*
	* @ingroup api_sat_counter
	*/
	SatCounter
	operator--(int)
	{
	SatCounter old_counter = *this;
	--*this;
	return old_counter;
	}

	/**
	* Shift-right-assignment.
	*
	* @ingroup api_sat_counter
	*/
	SatCounter&
	operator>>=(const int& shift)
	{
	assert(shift >= 0);
	this->counter >>= shift;
	return *this;
	}

	/**
	* Shift-left-assignment.
	*
	* @ingroup api_sat_counter
	*/
	SatCounter&
	operator<<=(const int& shift)
	{
	assert(shift >= 0);
	this->counter <<= shift;
	if (this->counter > maxVal) {
	this->counter = maxVal;
	}
	return *this;
	}

	/**
	* Add-assignment.
	*
	* @ingroup api_sat_counter
	*/
	SatCounter&
	operator+=(const int& value)
	{
	if (value >= 0) {
	if (maxVal - this->counter >= value) {
	this->counter += value;
	} else {
	this->counter = maxVal;
	}
	} else {
	*this -= -value;
	}
	return *this;
	}

	/**
	* Subtract-assignment.
	*
	* @ingroup api_sat_counter
	*/
	SatCounter&
	operator-=(const int& value)
	{
	if (value >= 0) {
	if (this->counter > value) {
	this->counter -= value;
	} else {
	this->counter = 0;
	}
	} else {
	*this += -value;
	}
	return *this;
	}

	/**
	* Read the counter's value.
	*
	* @ingroup api_sat_counter
	*/
	operator uint8_t() const { return counter; }

	/**
	* Reset the counter to its initial value.
	*
	* @ingroup api_sat_counter
	*/
	void reset() { counter = initialVal; }

	/**
	* Calculate saturation percentile of the current counter's value
	* with regard to its maximum possible value.
	*
	* @return A value between 0.0 and 1.0 to indicate which percentile of
	* the maximum value the current value is.
	*
	* @ingroup api_sat_counter
	*/
	double calcSaturation() const { return (double) counter / maxVal; }

	/**
	* Whether the counter has achieved its maximum value or not.
	*
	* @return True if the counter saturated.
	*
	* @ingroup api_sat_counter
	*/
	bool isSaturated() const { return counter == maxVal; }

	/**
	* Saturate the counter.
	*
	* @return The value added to the counter to reach saturation.
	*
	* @ingroup api_sat_counter
	*/
	uint8_t saturate()
	{
	const uint8_t diff = maxVal - counter;
	counter = maxVal;
	return diff;
	}

	private:
	uint8_t initialVal;
	uint8_t maxVal;
	uint8_t counter;
	};

	#endif // __BASE_SAT_COUNTER_HH__