scfx_ieee.hh

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  scfx_ieee.h -

  Original Author: Martin Janssen, Synopsys, Inc.

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// $Log: scfx_ieee.h,v $
// Revision 1.3  2011/08/24 22:05:43  acg
//  Torsten Maehne: initialization changes to remove warnings.
//
// Revision 1.2  2011/08/07 18:55:24  acg
//  Philipp A. Hartmann: added guard for __clang__ to get the clang platform
//  working.
//
// Revision 1.1.1.1  2006/12/15 20:20:04  acg
// SystemC 2.3
//
// Revision 1.3  2006/01/13 18:53:58  acg
// Andy Goodrich: added $Log command so that CVS comments are reproduced in
// the source.
//

#ifndef __SYSTEMC_EXT_DT_FX_SCFX_IEEE_HH__
#define __SYSTEMC_EXT_DT_FX_SCFX_IEEE_HH__

#include "../../utils/endian.hh"
#include "sc_fxdefs.hh"

namespace sc_dt
{

// classes defined in this module
union ieee_double;
class scfx_ieee_double;
union ieee_float;
class scfx_ieee_float;

#define SCFX_MASK_(Size) ((1u << (Size))-1u)

// ----------------------------------------------------------------------------
//  UNION : ieee_double
//
//  IEEE 754 double-precision format.
// ----------------------------------------------------------------------------

union ieee_double
{
    double d;

    struct
    {
#if defined(SC_BOOST_BIG_ENDIAN)
        unsigned negative:1;
        unsigned exponent:11;
        unsigned mantissa0:20;
        unsigned mantissa1:32;
#elif defined(SC_BOOST_LITTLE_ENDIAN)
        unsigned mantissa1:32;
        unsigned mantissa0:20;
        unsigned exponent:11;
        unsigned negative:1;
#endif
    } s;
};


const unsigned int SCFX_IEEE_DOUBLE_BIAS = 1023U;

const int SCFX_IEEE_DOUBLE_E_MAX = 1023;
const int SCFX_IEEE_DOUBLE_E_MIN = -1022;

const unsigned int SCFX_IEEE_DOUBLE_M_SIZE = 52;
const unsigned int SCFX_IEEE_DOUBLE_M0_SIZE = 20;
const unsigned int SCFX_IEEE_DOUBLE_M1_SIZE = 32;
const unsigned int SCFX_IEEE_DOUBLE_E_SIZE = 11;


// ----------------------------------------------------------------------------
//  CLASS : scfx_ieee_double
//
//  Convenient interface to union ieee_double.
// ----------------------------------------------------------------------------

class scfx_ieee_double
{
    ieee_double m_id;
  public:
    scfx_ieee_double();
    scfx_ieee_double(double);
    scfx_ieee_double(const scfx_ieee_double &);

    scfx_ieee_double &operator = (double);
    scfx_ieee_double &operator = (const scfx_ieee_double &);

    operator double() const;

    unsigned int negative() const;
    void negative(unsigned int);
    int exponent() const;
    void exponent(int);
    unsigned int mantissa0() const;
    void mantissa0(unsigned int);
    unsigned int mantissa1() const;
    void mantissa1(unsigned int);

    bool is_zero() const;
    bool is_subnormal() const;
    bool is_normal() const;
    bool is_inf() const;
    bool is_nan() const;

    void set_inf();
    void set_nan();

    int msb() const; // most significant non-zero bit
    int lsb() const; // least significant non-zero bit

    static const scfx_ieee_double nan();
    static const scfx_ieee_double inf(int);
};


// IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII

inline scfx_ieee_double::scfx_ieee_double() : m_id()
{
    m_id.d = 0.0;
}

inline scfx_ieee_double::scfx_ieee_double(double d) : m_id()
{
    m_id.d = d;
}

inline scfx_ieee_double::scfx_ieee_double(const scfx_ieee_double &a) :
        m_id(a.m_id)
{
    // m_id.d = a.m_id.d;
}

inline scfx_ieee_double &
scfx_ieee_double::operator = (double d)
{
    m_id.d = d;
    return *this;
}

inline scfx_ieee_double &
scfx_ieee_double::operator = (const scfx_ieee_double &a)
{
    m_id.d = a.m_id.d;
    return *this;
}

inline scfx_ieee_double::operator double() const
{
    return m_id.d;
}

inline unsigned int
scfx_ieee_double::negative() const
{
    return m_id.s.negative;
}

inline void
scfx_ieee_double::negative(unsigned int a)
{
    m_id.s.negative = a & SCFX_MASK_(1);
}

inline int
scfx_ieee_double::exponent() const
{
    return m_id.s.exponent - SCFX_IEEE_DOUBLE_BIAS;
}

inline void
scfx_ieee_double::exponent(int a)
{
    m_id.s.exponent = (SCFX_IEEE_DOUBLE_BIAS + a)
                      & SCFX_MASK_(SCFX_IEEE_DOUBLE_E_SIZE);
}

inline unsigned int
scfx_ieee_double::mantissa0() const
{
    return m_id.s.mantissa0;
}

inline void
scfx_ieee_double::mantissa0(unsigned int a)
{
    m_id.s.mantissa0 = a & SCFX_MASK_(SCFX_IEEE_DOUBLE_M0_SIZE);
}

inline unsigned int
scfx_ieee_double::mantissa1() const
{
    return m_id.s.mantissa1;
}

inline void
scfx_ieee_double::mantissa1(unsigned int a)
{
    m_id.s.mantissa1 = a; // & SCFX_MASK_(SCFX_IEEE_DOUBLE_M1_SIZE);
}

inline bool
scfx_ieee_double::is_zero() const
{
    return (exponent() == SCFX_IEEE_DOUBLE_E_MIN - 1 &&
            mantissa0() == 0U && mantissa1() == 0U);
}

inline bool
scfx_ieee_double::is_subnormal() const
{
    return (exponent() == SCFX_IEEE_DOUBLE_E_MIN - 1 &&
            (mantissa0() != 0U || mantissa1() != 0U));
}

inline bool
scfx_ieee_double::is_normal() const
{
    return (exponent() >= SCFX_IEEE_DOUBLE_E_MIN &&
            exponent() <= SCFX_IEEE_DOUBLE_E_MAX);
}

inline bool
scfx_ieee_double::is_inf() const
{
    return (exponent() == SCFX_IEEE_DOUBLE_E_MAX + 1 &&
            mantissa0() == 0U && mantissa1() == 0U);
}

inline bool
scfx_ieee_double::is_nan() const
{
    return (exponent() == SCFX_IEEE_DOUBLE_E_MAX + 1 &&
             (mantissa0() != 0U || mantissa1() != 0U));
}

inline void
scfx_ieee_double::set_inf()
{
    exponent(SCFX_IEEE_DOUBLE_E_MAX + 1);
    mantissa0(0U);
    mantissa1(0U);
}

inline void
scfx_ieee_double::set_nan()
{
    exponent(SCFX_IEEE_DOUBLE_E_MAX + 1);
    mantissa0((unsigned int)-1);
    mantissa1((unsigned int)-1);
}

#define MSB_STATEMENT(x,n) if ( x >> n ) { x >>= n; i += n; }

inline int
scfx_ieee_double::msb() const
{
    unsigned int m0 = mantissa0();
    unsigned int m1 = mantissa1();
    if (m0 != 0) {
        int i = 0;
        MSB_STATEMENT(m0, 16);
        MSB_STATEMENT(m0, 8);
        MSB_STATEMENT(m0, 4);
        MSB_STATEMENT(m0, 2);
        MSB_STATEMENT(m0, 1);
        return (i - 20);
    } else if (m1 != 0) {
        int i = 0;
        MSB_STATEMENT(m1, 16);
        MSB_STATEMENT(m1, 8);
        MSB_STATEMENT(m1, 4);
        MSB_STATEMENT(m1, 2);
        MSB_STATEMENT(m1, 1);
        return (i - 52);
    } else {
        return 0;
    }
}

#undef MSB_STATEMENT

#define LSB_STATEMENT(x,n) if ( x << n ) { x <<= n; i -= n; }

inline int
scfx_ieee_double::lsb() const
{
    unsigned int m0 = mantissa0();
    unsigned int m1 = mantissa1();
    if (m1 != 0) {
        int i = 31;
        LSB_STATEMENT(m1, 16);
        LSB_STATEMENT(m1, 8);
        LSB_STATEMENT(m1, 4);
        LSB_STATEMENT(m1, 2);
        LSB_STATEMENT(m1, 1);
        return (i - 52);
    } else if (m0 != 0) {
        int i = 31;
        LSB_STATEMENT(m0, 16);
        LSB_STATEMENT(m0, 8);
        LSB_STATEMENT(m0, 4);
        LSB_STATEMENT(m0, 2);
        LSB_STATEMENT(m0, 1);
        return (i - 20);
    } else {
        return 0;
    }
}

#undef LSB_STATEMENT

inline const scfx_ieee_double
scfx_ieee_double::nan()
{
    scfx_ieee_double id;
    id.set_nan();
    return id;
}

inline const scfx_ieee_double
scfx_ieee_double::inf(int sign)
{
    scfx_ieee_double id(sign);
    id.set_inf();
    return id;
}


// ----------------------------------------------------------------------------
//  UNION : ieee_float
//
//  IEEE 754 single-precision format.
// ----------------------------------------------------------------------------

union ieee_float
{
    float f;
    struct
    {
#if defined(SC_BOOST_BIG_ENDIAN)
        unsigned negative:1;
        unsigned exponent:8;
        unsigned mantissa:23;
#elif defined(SC_BOOST_LITTLE_ENDIAN)
        unsigned mantissa:23;
        unsigned exponent:8;
        unsigned negative:1;
#endif
    } s;
};


const unsigned int SCFX_IEEE_FLOAT_BIAS = 127U;

const int SCFX_IEEE_FLOAT_E_MAX = 127;
const int SCFX_IEEE_FLOAT_E_MIN = -126;

const unsigned int SCFX_IEEE_FLOAT_M_SIZE = 23;
const unsigned int SCFX_IEEE_FLOAT_E_SIZE = 8;


// ----------------------------------------------------------------------------
//  CLASS : scfx_ieee_float
//
// Convenient wrapper to union ieee_float.
// ----------------------------------------------------------------------------

class scfx_ieee_float
{
    ieee_float m_if;

  public:
    scfx_ieee_float();
    scfx_ieee_float(float);
    scfx_ieee_float(const scfx_ieee_float &);

    scfx_ieee_float &operator = (float);
    scfx_ieee_float &operator = (const scfx_ieee_float &);

    operator float() const;

    unsigned int negative() const;
    void negative(unsigned int);
    int exponent() const;
    void exponent(int);
    unsigned int mantissa() const;
    void mantissa(unsigned int);

    bool is_zero() const;
    bool is_subnormal() const;
    bool is_normal() const;
    bool is_inf() const;
    bool is_nan() const;

    void set_inf();
    void set_nan();
};


// IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII

inline scfx_ieee_float::scfx_ieee_float() : m_if()
{
    m_if.f = 0.0;
}

inline scfx_ieee_float::scfx_ieee_float(float f) : m_if()
{
    m_if.f = f;
}

inline scfx_ieee_float::scfx_ieee_float(const scfx_ieee_float &a) :
        m_if(a.m_if)
{
    // m_if.f = a.m_if.f;
}


inline scfx_ieee_float &
scfx_ieee_float::operator = (float f)
{
    m_if.f = f;
    return *this;
}

inline scfx_ieee_float &
scfx_ieee_float::operator = (const scfx_ieee_float &a)
{
    m_if.f = a.m_if.f;
    return *this;
}

inline scfx_ieee_float::operator float() const
{
    return m_if.f;
}

inline unsigned int
scfx_ieee_float::negative() const
{
    return m_if.s.negative;
}

inline void
scfx_ieee_float::negative(unsigned int a)
{
    m_if.s.negative = a & SCFX_MASK_(1);
}

inline int
scfx_ieee_float::exponent() const
{
    return m_if.s.exponent - SCFX_IEEE_FLOAT_BIAS;
}

inline void
scfx_ieee_float::exponent(int a)
{
    m_if.s.exponent = (SCFX_IEEE_FLOAT_BIAS + a) &
                      SCFX_MASK_(SCFX_IEEE_FLOAT_E_SIZE);
}

inline unsigned int
scfx_ieee_float::mantissa() const
{
    return m_if.s.mantissa;
}

inline void
scfx_ieee_float::mantissa(unsigned int a)
{
    m_if.s.mantissa = a & SCFX_MASK_(SCFX_IEEE_FLOAT_M_SIZE);
}


inline bool
scfx_ieee_float::is_zero() const
{
    return (exponent() == SCFX_IEEE_FLOAT_E_MIN - 1 && mantissa() == 0U);
}

inline bool
scfx_ieee_float::is_subnormal() const
{
    return (exponent() == SCFX_IEEE_FLOAT_E_MIN - 1 && mantissa() != 0U);
}

inline bool
scfx_ieee_float::is_normal() const
{
    return (exponent() >= SCFX_IEEE_FLOAT_E_MIN &&
            exponent() <= SCFX_IEEE_FLOAT_E_MAX);
}

inline bool
scfx_ieee_float::is_inf() const
{
    return (exponent() == SCFX_IEEE_FLOAT_E_MAX + 1 && mantissa() == 0U);
}

inline bool
scfx_ieee_float::is_nan() const
{
    return (exponent() == SCFX_IEEE_FLOAT_E_MAX + 1 && mantissa() != 0U);
}

inline void
scfx_ieee_float::set_inf()
{
    exponent(SCFX_IEEE_FLOAT_E_MAX + 1);
    mantissa(0U);
}

inline void
scfx_ieee_float::set_nan()
{
    exponent(SCFX_IEEE_FLOAT_E_MAX + 1);
    mantissa((unsigned int)-1);
}


// ----------------------------------------------------------------------------
//  FUNCTION : scfx_pow2
//
//  Computes 2.0**exp in double-precision.
// ----------------------------------------------------------------------------

inline double
scfx_pow2(int exp)
{
    scfx_ieee_double r;
    if (exp < SCFX_IEEE_DOUBLE_E_MIN) {
        r = 0.0;
        // handle subnormal case
        exp -= SCFX_IEEE_DOUBLE_E_MIN;
        if ((exp += 20) >= 0) {
            r.mantissa0(1U << exp);
        } else if ((exp += 32) >= 0) {
            r.mantissa1(1U << exp);
        }
    } else if (exp > SCFX_IEEE_DOUBLE_E_MAX) {
        r.set_inf();
    } else {
        r = 1.0;
        r.exponent(exp);
    }
    return r;
}


// ----------------------------------------------------------------------------
//  FUNCTION : uint64_to_double
//
//  Platform independent conversion from double uint64 to double.
//  Needed because VC++6 doesn't support this conversion.
// ----------------------------------------------------------------------------

inline double
uint64_to_double(uint64 a)
{
#if defined(__clang__)
    // conversion from uint64 to double not implemented; use int64
    double tmp = static_cast<double>(static_cast<int64>(a));
    return (tmp >= 0) ? tmp : tmp + sc_dt::scfx_pow2(64);
#else
    return static_cast<double>(a);
#endif
}

} // namespace sc_dt

#undef SCFX_MASK_

#endif // __SYSTEMC_EXT_DT_FX_SCFX_IEEE_HH__