sat_counter.hh

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#ifndef __BASE_SAT_COUNTER_HH__
#define __BASE_SAT_COUNTER_HH__
 
#include <cassert>
#include <cstdint>
 
#include "base/logging.hh"
#include "base/types.hh"
 
namespace gem5
{
 
template <class T>
class GenericSatCounter
{
  public:
    GenericSatCounter() = delete;
 
    explicit GenericSatCounter(unsigned bits, T initial_val = 0)
        : initialVal(initial_val), maxVal((1ULL << bits) - 1),
          counter(initial_val)
    {
        fatal_if(bits > 8*sizeof(T),
                 "Number of bits exceeds counter size");
        fatal_if(initial_val > maxVal,
                 "Saturating counter's initial value exceeds max value.");
    }
 
    GenericSatCounter(const GenericSatCounter& other)
        : initialVal(other.initialVal), maxVal(other.maxVal),
          counter(other.counter)
    {
    }
 
    GenericSatCounter& operator=(const GenericSatCounter& other) {
        if (this != &other) {
            GenericSatCounter temp(other);
            this->swap(temp);
        }
        return *this;
    }
 
    GenericSatCounter(GenericSatCounter&& other)
    {
        initialVal = other.initialVal;
        maxVal = other.maxVal;
        counter = other.counter;
        GenericSatCounter temp(0);
        other.swap(temp);
    }
 
    GenericSatCounter& operator=(GenericSatCounter&& other) {
        if (this != &other) {
            initialVal = other.initialVal;
            maxVal = other.maxVal;
            counter = other.counter;
            GenericSatCounter temp(0);
            other.swap(temp);
        }
        return *this;
    }
 
    void
    swap(GenericSatCounter& other)
    {
        std::swap(initialVal, other.initialVal);
        std::swap(maxVal, other.maxVal);
        std::swap(counter, other.counter);
    }
 
    GenericSatCounter&
    operator++()
    {
        if (counter < maxVal) {
            ++counter;
        }
        return *this;
    }
 
    GenericSatCounter
    operator++(int)
    {
        GenericSatCounter old_counter = *this;
        ++*this;
        return old_counter;
    }
 
    GenericSatCounter&
    operator--()
    {
        if (counter > 0) {
            --counter;
        }
        return *this;
    }
 
    GenericSatCounter
    operator--(int)
    {
        GenericSatCounter old_counter = *this;
        --*this;
        return old_counter;
    }
 
    GenericSatCounter&
    operator>>=(const int& shift)
    {
        assert(shift >= 0);
        this->counter >>= shift;
        return *this;
    }
 
    GenericSatCounter&
    operator<<=(const int& shift)
    {
        assert(shift >= 0);
        this->counter <<= shift;
        if (this->counter > maxVal) {
            this->counter = maxVal;
        }
        return *this;
    }
 
    GenericSatCounter&
    operator+=(const long long& value)
    {
        if (value >= 0) {
            if (maxVal - this->counter >= value) {
                this->counter += value;
            } else {
                this->counter = maxVal;
            }
        } else {
            *this -= -value;
        }
        return *this;
    }
 
    GenericSatCounter&
    operator-=(const long long& value)
    {
        if (value >= 0) {
            if (this->counter > value) {
                this->counter -= value;
            } else {
                this->counter = 0;
            }
        } else {
            *this += -value;
        }
        return *this;
    }
 
    operator T() const { return counter; }
 
    void reset() { counter = initialVal; }
 
    double calcSaturation() const { return (double) counter / maxVal; }
 
    bool isSaturated() const { return counter == maxVal; }
 
    T saturate()
    {
        const T diff = maxVal - counter;
        counter = maxVal;
        return diff;
    }
 
  private:
    T initialVal;
    T maxVal;
    T counter;
};
 
typedef GenericSatCounter<uint8_t> SatCounter8;
typedef GenericSatCounter<uint16_t> SatCounter16;
typedef GenericSatCounter<uint32_t> SatCounter32;
typedef GenericSatCounter<uint64_t> SatCounter64;
} // namespace gem5
 
#endif // __BASE_SAT_COUNTER_HH__