softfloat.c

来自「基于4个mips核的noc设计」· C语言 代码 · 共 1,846 行 · 第 1/5 页

        lastBitMask = 1;
        lastBitMask = ( lastBitMask<<( 0x432 - aExp ) )<<1;
        roundBitsMask = lastBitMask - 1;
        z = a;
        roundingMode = float_rounding_mode;
        if ( roundingMode == float_round_nearest_even ) {
            if ( lastBitMask ) {
                add64( z.high, z.low, 0, lastBitMask>>1, (unsigned int *) &z.high, (unsigned int *) &z.low );
                if ( ( z.low & roundBitsMask ) == 0 ) z.low &= ~ lastBitMask;
            }
            else {
                if ( (sbits32) z.low < 0 ) {
                    ++z.high;
                    if ( (bits32) ( z.low<<1 ) == 0 ) z.high &= ~1;
                }
            }
        }
        else if ( roundingMode != float_round_to_zero ) {
            if (   extractFloat64Sign( z )
                 ^ ( roundingMode == float_round_up ) ) {
                add64( z.high, z.low, 0, roundBitsMask, (unsigned int *) &z.high, (unsigned int *) &z.low );
            }
        }
        z.low &= ~ roundBitsMask;
    }
    else {
        if ( aExp <= 0x3FE ) {
            if ( ( ( (bits32) ( a.high<<1 ) ) | a.low ) == 0 ) return a;
            float_exception_flags |= float_flag_inexact;
            aSign = extractFloat64Sign( a );
            switch ( float_rounding_mode ) {
             case float_round_nearest_even:
                if (    ( aExp == 0x3FE )
                     && ( extractFloat64Frac0( a ) | extractFloat64Frac1( a ) )
                   ) {
                    return packFloat64( aSign, 0x3FF, 0, 0 );
                }
                break;
             case float_round_down:
                return
                      aSign ? packFloat64( 1, 0x3FF, 0, 0 )
                    : packFloat64( 0, 0, 0, 0 );
             case float_round_up:
                return
                      aSign ? packFloat64( 1, 0, 0, 0 )
                    : packFloat64( 0, 0x3FF, 0, 0 );
            }
            return packFloat64( aSign, 0, 0, 0 );
        }
        lastBitMask = 1;
        lastBitMask <<= 0x413 - aExp;
        roundBitsMask = lastBitMask - 1;
        z.low = 0;
        z.high = a.high;
        roundingMode = float_rounding_mode;
        if ( roundingMode == float_round_nearest_even ) {
            z.high += lastBitMask>>1;
            if ( ( ( z.high & roundBitsMask ) | a.low ) == 0 ) {
                z.high &= ~ lastBitMask;
            }
        }
        else if ( roundingMode != float_round_to_zero ) {
            if (   extractFloat64Sign( z )
                 ^ ( roundingMode == float_round_up ) ) {
                z.high |= ( a.low != 0 );
                z.high += roundBitsMask;
            }
        }
        z.high &= ~ roundBitsMask;
    }
    if ( ( z.low != a.low ) || ( z.high != a.high ) ) {
        float_exception_flags |= float_flag_inexact;
    }
    return z;

}

/*----------------------------------------------------------------------------
| Returns the result of adding the absolute values of the double-precision
| floating-point values `a' and `b'.  If `zSign' is 1, the sum is negated
| before being returned.  `zSign' is ignored if the result is a NaN.
| The addition is performed according to the IEC/IEEE Standard for Binary
| Floating-Point Arithmetic.
*----------------------------------------------------------------------------*/

static float64 addFloat64Sigs( float64 a, float64 b, flag zSign )
{
    int16 aExp, bExp, zExp;
    bits32 aSig0, aSig1, bSig0, bSig1, zSig0, zSig1, zSig2;
    int16 expDiff;

    aSig1 = extractFloat64Frac1( a );
    aSig0 = extractFloat64Frac0( a );
    aExp = extractFloat64Exp( a );
    bSig1 = extractFloat64Frac1( b );
    bSig0 = extractFloat64Frac0( b );
    bExp = extractFloat64Exp( b );
    expDiff = aExp - bExp;
    if ( 0 < expDiff ) {
        if ( aExp == 0x7FF ) {
            if ( aSig0 | aSig1 ) return propagateFloat64NaN( a, b );
            return a;
        }
        if ( bExp == 0 ) {
            --expDiff;
        }
        else {
            bSig0 |= 0x00100000;
        }
        shift64ExtraRightJamming(
            bSig0, bSig1, 0, expDiff, &bSig0, &bSig1, &zSig2 );
        zExp = aExp;
    }
    else if ( expDiff < 0 ) {
        if ( bExp == 0x7FF ) {
            if ( bSig0 | bSig1 ) return propagateFloat64NaN( a, b );
            return packFloat64( zSign, 0x7FF, 0, 0 );
        }
        if ( aExp == 0 ) {
            ++expDiff;
        }
        else {
            aSig0 |= 0x00100000;
        }
        shift64ExtraRightJamming(
            aSig0, aSig1, 0, - expDiff, &aSig0, &aSig1, &zSig2 );
        zExp = bExp;
    }
    else {
        if ( aExp == 0x7FF ) {
            if ( aSig0 | aSig1 | bSig0 | bSig1 ) {
                return propagateFloat64NaN( a, b );
            }
            return a;
        }
        add64( aSig0, aSig1, bSig0, bSig1, &zSig0, &zSig1 );
        if ( aExp == 0 ) return packFloat64( zSign, 0, zSig0, zSig1 );
        zSig2 = 0;
        zSig0 |= 0x00200000;
        zExp = aExp;
        goto shiftRight1;
    }
    aSig0 |= 0x00100000;
    add64( aSig0, aSig1, bSig0, bSig1, &zSig0, &zSig1 );
    --zExp;
    if ( zSig0 < 0x00200000 ) goto roundAndPack;
    ++zExp;
 shiftRight1:
    shift64ExtraRightJamming( zSig0, zSig1, zSig2, 1, &zSig0, &zSig1, &zSig2 );
 roundAndPack:
    return roundAndPackFloat64( zSign, zExp, zSig0, zSig1, zSig2 );

}

/*----------------------------------------------------------------------------
| Returns the result of subtracting the absolute values of the double-
| precision floating-point values `a' and `b'.  If `zSign' is 1, the
| difference is negated before being returned.  `zSign' is ignored if the
| result is a NaN.  The subtraction is performed according to the IEC/IEEE
| Standard for Binary Floating-Point Arithmetic.
*----------------------------------------------------------------------------*/

static float64 subFloat64Sigs( float64 a, float64 b, flag zSign )
{
    int16 aExp, bExp, zExp;
    bits32 aSig0, aSig1, bSig0, bSig1, zSig0, zSig1;
    int16 expDiff;
    float64 z;

    aSig1 = extractFloat64Frac1( a );
    aSig0 = extractFloat64Frac0( a );
    aExp = extractFloat64Exp( a );
    bSig1 = extractFloat64Frac1( b );
    bSig0 = extractFloat64Frac0( b );
    bExp = extractFloat64Exp( b );
    expDiff = aExp - bExp;
    shortShift64Left( aSig0, aSig1, 10, &aSig0, &aSig1 );
    shortShift64Left( bSig0, bSig1, 10, &bSig0, &bSig1 );
    if ( 0 < expDiff ) goto aExpBigger;
    if ( expDiff < 0 ) goto bExpBigger;
    if ( aExp == 0x7FF ) {
        if ( aSig0 | aSig1 | bSig0 | bSig1 ) {
            return propagateFloat64NaN( a, b );
        }
        float_raise( float_flag_invalid );
        z.low = float64_default_nan_low;
        z.high = float64_default_nan_high;
        return z;
    }
    if ( aExp == 0 ) {
        aExp = 1;
        bExp = 1;
    }
    if ( bSig0 < aSig0 ) goto aBigger;
    if ( aSig0 < bSig0 ) goto bBigger;
    if ( bSig1 < aSig1 ) goto aBigger;
    if ( aSig1 < bSig1 ) goto bBigger;
    return packFloat64( float_rounding_mode == float_round_down, 0, 0, 0 );
 bExpBigger:
    if ( bExp == 0x7FF ) {
        if ( bSig0 | bSig1 ) return propagateFloat64NaN( a, b );
        return packFloat64( zSign ^ 1, 0x7FF, 0, 0 );
    }
    if ( aExp == 0 ) {
        ++expDiff;
    }
    else {
        aSig0 |= 0x40000000;
    }
    shift64RightJamming( aSig0, aSig1, - expDiff, &aSig0, &aSig1 );
    bSig0 |= 0x40000000;
 bBigger:
    sub64( bSig0, bSig1, aSig0, aSig1, &zSig0, &zSig1 );
    zExp = bExp;
    zSign ^= 1;
    goto normalizeRoundAndPack;
 aExpBigger:
    if ( aExp == 0x7FF ) {
        if ( aSig0 | aSig1 ) return propagateFloat64NaN( a, b );
        return a;
    }
    if ( bExp == 0 ) {
        --expDiff;
    }
    else {
        bSig0 |= 0x40000000;
    }
    shift64RightJamming( bSig0, bSig1, expDiff, &bSig0, &bSig1 );
    aSig0 |= 0x40000000;
 aBigger:
    sub64( aSig0, aSig1, bSig0, bSig1, &zSig0, &zSig1 );
    zExp = aExp;
 normalizeRoundAndPack:
    --zExp;
    return normalizeRoundAndPackFloat64( zSign, zExp - 10, zSig0, zSig1 );

}

/*----------------------------------------------------------------------------
| Returns the result of adding the double-precision floating-point values `a'
| and `b'.  The operation is performed according to the IEC/IEEE Standard for
| Binary Floating-Point Arithmetic.
*----------------------------------------------------------------------------*/

float64 float64_add( float64 a, float64 b )
{
    flag aSign, bSign;

    aSign = extractFloat64Sign( a );
    bSign = extractFloat64Sign( b );
    if ( aSign == bSign ) {
        return addFloat64Sigs( a, b, aSign );
    }
    else {
        return subFloat64Sigs( a, b, aSign );
    }

}

/*----------------------------------------------------------------------------
| Returns the result of subtracting the double-precision floating-point values
| `a' and `b'.  The operation is performed according to the IEC/IEEE Standard
| for Binary Floating-Point Arithmetic.
*----------------------------------------------------------------------------*/

float64 float64_sub( float64 a, float64 b )
{
    flag aSign, bSign;

    aSign = extractFloat64Sign( a );
    bSign = extractFloat64Sign( b );
    if ( aSign == bSign ) {
        return subFloat64Sigs( a, b, aSign );
    }
    else {
        return addFloat64Sigs( a, b, aSign );
    }

}

/*----------------------------------------------------------------------------
| Returns the result of multiplying the double-precision floating-point values
| `a' and `b'.  The operation is performed according to the IEC/IEEE Standard
| for Binary Floating-Point Arithmetic.
*----------------------------------------------------------------------------*/

float64 float64_mul( float64 a, float64 b )
{
    flag aSign, bSign, zSign;
    int16 aExp, bExp, zExp;
    bits32 aSig0, aSig1, bSig0, bSig1, zSig0, zSig1, zSig2, zSig3;
    float64 z;

    aSig1 = extractFloat64Frac1( a );
    aSig0 = extractFloat64Frac0( a );
    aExp = extractFloat64Exp( a );
    aSign = extractFloat64Sign( a );
    bSig1 = extractFloat64Frac1( b );
    bSig0 = extractFloat64Frac0( b );
    bExp = extractFloat64Exp( b );
    bSign = extractFloat64Sign( b );
    zSign = aSign ^ bSign;
    if ( aExp == 0x7FF ) {
        if (    ( aSig0 | aSig1 )
             || ( ( bExp == 0x7FF ) && ( bSig0 | bSig1 ) ) ) {
            return propagateFloat64NaN( a, b );
        }
        if ( ( bExp | bSig0 | bSig1 ) == 0 ) goto invalid;
        return packFloat64( zSign, 0x7FF, 0, 0 );
    }
    if ( bExp == 0x7FF ) {
        if ( bSig0 | bSig1 ) return propagateFloat64NaN( a, b );
        if ( ( aExp | aSig0 | aSig1 ) == 0 ) {
 invalid:
            float_raise( float_flag_invalid );
            z.low = float64_default_nan_low;
            z.high = float64_default_nan_high;
            return z;
        }
        return packFloat64( zSign, 0x7FF, 0, 0 );
    }
    if ( aExp == 0 ) {
        if ( ( aSig0 | aSig1 ) == 0 ) return packFloat64( zSign, 0, 0, 0 );
        normalizeFloat64Subnormal( aSig0, aSig1, &aExp, &aSig0, &aSig1 );
    }
    if ( bExp == 0 ) {
        if ( ( bSig0 | bSig1 ) == 0 ) return packFloat64( zSign, 0, 0, 0 );
        normalizeFloat64Subnormal( bSig0, bSig1, &bExp, &bSig0, &bSig1 );
    }
    zExp = aExp + bExp - 0x400;
    aSig0 |= 0x00100000;
    shortShift64Left( bSig0, bSig1, 12, &bSig0, &bSig1 );
    mul64To128( aSig0, aSig1, bSig0, bSig1, &zSig0, &zSig1, &zSig2, &zSig3 );
    add64( zSig0, zSig1, aSig0, aSig1, &zSig0, &zSig1 );
    zSig2 |= ( zSig3 != 0 );
    if ( 0x00200000 <= zSig0 ) {
        shift64ExtraRightJamming(
            zSig0, zSig1, zSig2, 1, &zSig0, &zSig1, &zSig2 );
        ++zExp;
    }
    return roundAndPackFloat64( zSign, zExp, zSig0, zSig1, zSig2 );

}

/*----------------------------------------------------------------------------
| Returns the result of dividing the double-precision floating-point value `a'
| by the corresponding value `b'.  The operation is performed according to the
| IEC/IEEE Standard for Binary Floating-Point Arithmetic.
*----------------------------------------------------------------------------*/

float64 float64_div( float64 a, float64 b )
{
    flag aSign, bSign, zSign;
    int16 aExp, bExp, zExp;
    bits32 aSig0, aSig1, bSig0, bSig1, zSig0, zSig1, zSig2;
    bits32 rem0, rem1, rem2, rem3, term0, term1, term2, term3;
    float64 z;

    aSig1 = extractFloat64Frac1( a );
    aSig0 = extractFloat64Frac0( a );
    aExp = extractFloat64Exp( a );
    aSign = extractFloat64Sign( a );
    bSig1 = extractFloat64Frac1( b );
    bSig0 = extractFloat64Frac0( b );
    bExp = extractFloat64Exp( b );
    bSign