Commit cf07323d authored by Alex Bennée's avatar Alex Bennée
Browse files

fpu/softfloat: re-factor div 



We can now add float16_div and use the common decompose and
canonicalize functions to have a single implementation for
float16/32/64 versions.

Signed-off-by: default avatarAlex Bennée <alex.bennee@linaro.org>
Signed-off-by: default avatarRichard Henderson <richard.henderson@linaro.org>
Reviewed-by: default avatarPeter Maydell <peter.maydell@linaro.org>
parent 74d707e2

fpu/softfloat-macros.h

+48 −0
Original line number Diff line number Diff line
@@ -625,6 +625,54 @@ static uint64_t estimateDiv128To64( uint64_t a0, uint64_t a1, uint64_t b ) 


}



/* From the GNU Multi Precision Library - longlong.h __udiv_qrnnd

 * (https://gmplib.org/repo/gmp/file/tip/longlong.h)

 *

 * Licensed under the GPLv2/LGPLv3

 */

static uint64_t div128To64(uint64_t n0, uint64_t n1, uint64_t d)

{

    uint64_t d0, d1, q0, q1, r1, r0, m;



    d0 = (uint32_t)d;

    d1 = d >> 32;



    r1 = n1 % d1;

    q1 = n1 / d1;

    m = q1 * d0;

    r1 = (r1 << 32) | (n0 >> 32);

    if (r1 < m) {

        q1 -= 1;

        r1 += d;

        if (r1 >= d) {

            if (r1 < m) {

                q1 -= 1;

                r1 += d;

            }

        }

    }

    r1 -= m;



    r0 = r1 % d1;

    q0 = r1 / d1;

    m = q0 * d0;

    r0 = (r0 << 32) | (uint32_t)n0;

    if (r0 < m) {

        q0 -= 1;

        r0 += d;

        if (r0 >= d) {

            if (r0 < m) {

                q0 -= 1;

                r0 += d;

            }

        }

    }

    r0 -= m;



    /* Return remainder in LSB */

    return (q1 << 32) | q0 | (r0 != 0);

}



/*----------------------------------------------------------------------------

| Returns an approximation to the square root of the 32-bit significand given

| by `a'.  Considered as an integer, `a' must be at least 2^31.  If bit 0 of

fpu/softfloat.c

+88 −148
Original line number Diff line number Diff line
@@ -816,6 +816,94 @@ float64 __attribute__((flatten)) float64_mul(float64 a, float64 b, 
    return float64_round_pack_canonical(pr, status);

}



/*

 * Returns the result of dividing the floating-point value `a' by the

 * corresponding value `b'. The operation is performed according to

 * the IEC/IEEE Standard for Binary Floating-Point Arithmetic.

 */



static FloatParts div_floats(FloatParts a, FloatParts b, float_status *s)

{

    bool sign = a.sign ^ b.sign;



    if (a.cls == float_class_normal && b.cls == float_class_normal) {

        uint64_t temp_lo, temp_hi;

        int exp = a.exp - b.exp;

        if (a.frac < b.frac) {

            exp -= 1;

            shortShift128Left(0, a.frac, DECOMPOSED_BINARY_POINT + 1,

                              &temp_hi, &temp_lo);

        } else {

            shortShift128Left(0, a.frac, DECOMPOSED_BINARY_POINT,

                              &temp_hi, &temp_lo);

        }

        /* LSB of quot is set if inexact which roundandpack will use

         * to set flags. Yet again we re-use a for the result */

        a.frac = div128To64(temp_lo, temp_hi, b.frac);

        a.sign = sign;

        a.exp = exp;

        return a;

    }

    /* handle all the NaN cases */

    if (is_nan(a.cls) || is_nan(b.cls)) {

        return pick_nan(a, b, s);

    }

    /* 0/0 or Inf/Inf */

    if (a.cls == b.cls

        &&

        (a.cls == float_class_inf || a.cls == float_class_zero)) {

        s->float_exception_flags |= float_flag_invalid;

        a.cls = float_class_dnan;

        return a;

    }

    /* Div 0 => Inf */

    if (b.cls == float_class_zero) {

        s->float_exception_flags |= float_flag_divbyzero;

        a.cls = float_class_inf;

        a.sign = sign;

        return a;

    }

    /* Inf / x or 0 / x */

    if (a.cls == float_class_inf || a.cls == float_class_zero) {

        a.sign = sign;

        return a;

    }

    /* Div by Inf */

    if (b.cls == float_class_inf) {

        a.cls = float_class_zero;

        a.sign = sign;

        return a;

    }

    g_assert_not_reached();

}



float16 float16_div(float16 a, float16 b, float_status *status)

{

    FloatParts pa = float16_unpack_canonical(a, status);

    FloatParts pb = float16_unpack_canonical(b, status);

    FloatParts pr = div_floats(pa, pb, status);



    return float16_round_pack_canonical(pr, status);

}



float32 float32_div(float32 a, float32 b, float_status *status)

{

    FloatParts pa = float32_unpack_canonical(a, status);

    FloatParts pb = float32_unpack_canonical(b, status);

    FloatParts pr = div_floats(pa, pb, status);



    return float32_round_pack_canonical(pr, status);

}



float64 float64_div(float64 a, float64 b, float_status *status)

{

    FloatParts pa = float64_unpack_canonical(a, status);

    FloatParts pb = float64_unpack_canonical(b, status);

    FloatParts pr = div_floats(pa, pb, status);



    return float64_round_pack_canonical(pr, status);

}



/*----------------------------------------------------------------------------

| Takes a 64-bit fixed-point value `absZ' with binary point between bits 6

| and 7, and returns the properly rounded 32-bit integer corresponding to the
@@ -2627,77 +2715,6 @@ float32 float32_round_to_int(float32 a, float_status *status) 


}





/*----------------------------------------------------------------------------

| Returns the result of dividing the single-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.

*----------------------------------------------------------------------------*/



float32 float32_div(float32 a, float32 b, float_status *status)

{

    flag aSign, bSign, zSign;

    int aExp, bExp, zExp;

    uint32_t aSig, bSig, zSig;

    a = float32_squash_input_denormal(a, status);

    b = float32_squash_input_denormal(b, status);



    aSig = extractFloat32Frac( a );

    aExp = extractFloat32Exp( a );

    aSign = extractFloat32Sign( a );

    bSig = extractFloat32Frac( b );

    bExp = extractFloat32Exp( b );

    bSign = extractFloat32Sign( b );

    zSign = aSign ^ bSign;

    if ( aExp == 0xFF ) {

        if (aSig) {

            return propagateFloat32NaN(a, b, status);

        }

        if ( bExp == 0xFF ) {

            if (bSig) {

                return propagateFloat32NaN(a, b, status);

            }

            float_raise(float_flag_invalid, status);

            return float32_default_nan(status);

        }

        return packFloat32( zSign, 0xFF, 0 );

    }

    if ( bExp == 0xFF ) {

        if (bSig) {

            return propagateFloat32NaN(a, b, status);

        }

        return packFloat32( zSign, 0, 0 );

    }

    if ( bExp == 0 ) {

        if ( bSig == 0 ) {

            if ( ( aExp | aSig ) == 0 ) {

                float_raise(float_flag_invalid, status);

                return float32_default_nan(status);

            }

            float_raise(float_flag_divbyzero, status);

            return packFloat32( zSign, 0xFF, 0 );

        }

        normalizeFloat32Subnormal( bSig, &bExp, &bSig );

    }

    if ( aExp == 0 ) {

        if ( aSig == 0 ) return packFloat32( zSign, 0, 0 );

        normalizeFloat32Subnormal( aSig, &aExp, &aSig );

    }

    zExp = aExp - bExp + 0x7D;

    aSig = ( aSig | 0x00800000 )<<7;

    bSig = ( bSig | 0x00800000 )<<8;

    if ( bSig <= ( aSig + aSig ) ) {

        aSig >>= 1;

        ++zExp;

    }

    zSig = ( ( (uint64_t) aSig )<<32 ) / bSig;

    if ( ( zSig & 0x3F ) == 0 ) {

        zSig |= ( (uint64_t) bSig * zSig != ( (uint64_t) aSig )<<32 );

    }

    return roundAndPackFloat32(zSign, zExp, zSig, status);



}



/*----------------------------------------------------------------------------

| Returns the remainder of the single-precision floating-point value `a'

| with respect to the corresponding value `b'.  The operation is performed
@@ -4159,83 +4176,6 @@ float64 float64_trunc_to_int(float64 a, float_status *status) 
    return res;

}



/*----------------------------------------------------------------------------

| 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, float_status *status)

{

    flag aSign, bSign, zSign;

    int aExp, bExp, zExp;

    uint64_t aSig, bSig, zSig;

    uint64_t rem0, rem1;

    uint64_t term0, term1;

    a = float64_squash_input_denormal(a, status);

    b = float64_squash_input_denormal(b, status);



    aSig = extractFloat64Frac( a );

    aExp = extractFloat64Exp( a );

    aSign = extractFloat64Sign( a );

    bSig = extractFloat64Frac( b );

    bExp = extractFloat64Exp( b );

    bSign = extractFloat64Sign( b );

    zSign = aSign ^ bSign;

    if ( aExp == 0x7FF ) {

        if (aSig) {

            return propagateFloat64NaN(a, b, status);

        }

        if ( bExp == 0x7FF ) {

            if (bSig) {

                return propagateFloat64NaN(a, b, status);

            }

            float_raise(float_flag_invalid, status);

            return float64_default_nan(status);

        }

        return packFloat64( zSign, 0x7FF, 0 );

    }

    if ( bExp == 0x7FF ) {

        if (bSig) {

            return propagateFloat64NaN(a, b, status);

        }

        return packFloat64( zSign, 0, 0 );

    }

    if ( bExp == 0 ) {

        if ( bSig == 0 ) {

            if ( ( aExp | aSig ) == 0 ) {

                float_raise(float_flag_invalid, status);

                return float64_default_nan(status);

            }

            float_raise(float_flag_divbyzero, status);

            return packFloat64( zSign, 0x7FF, 0 );

        }

        normalizeFloat64Subnormal( bSig, &bExp, &bSig );

    }

    if ( aExp == 0 ) {

        if ( aSig == 0 ) return packFloat64( zSign, 0, 0 );

        normalizeFloat64Subnormal( aSig, &aExp, &aSig );

    }

    zExp = aExp - bExp + 0x3FD;

    aSig = ( aSig | LIT64( 0x0010000000000000 ) )<<10;

    bSig = ( bSig | LIT64( 0x0010000000000000 ) )<<11;

    if ( bSig <= ( aSig + aSig ) ) {

        aSig >>= 1;

        ++zExp;

    }

    zSig = estimateDiv128To64( aSig, 0, bSig );

    if ( ( zSig & 0x1FF ) <= 2 ) {

        mul64To128( bSig, zSig, &term0, &term1 );

        sub128( aSig, 0, term0, term1, &rem0, &rem1 );

        while ( (int64_t) rem0 < 0 ) {

            --zSig;

            add128( rem0, rem1, 0, bSig, &rem0, &rem1 );

        }

        zSig |= ( rem1 != 0 );

    }

    return roundAndPackFloat64(zSign, zExp, zSig, status);



}



/*----------------------------------------------------------------------------

| Returns the remainder of the double-precision floating-point value `a'

include/fpu/softfloat.h

+1 −0
Original line number Diff line number Diff line
@@ -240,6 +240,7 @@ float64 float16_to_float64(float16 a, flag ieee, float_status *status); 
float16 float16_add(float16, float16, float_status *status);

float16 float16_sub(float16, float16, float_status *status);

float16 float16_mul(float16, float16, float_status *status);

float16 float16_div(float16, float16, float_status *status);



int float16_is_quiet_nan(float16, float_status *status);

int float16_is_signaling_nan(float16, float_status *status);