Function subFloatx80Sigs

src/softfloat/softfloat.cpp:2402–2463

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

static floatx80 subFloatx80Sigs(floatx80 a, floatx80 b, flag zSign,
                                float_status *status)
{
    int32_t aExp, bExp, zExp;
    uint64_t aSig, bSig, zSig0, zSig1;
    int32_t expDiff;

    aSig = extractFloatx80Frac( a );
    aExp = extractFloatx80Exp( a );
    bSig = extractFloatx80Frac( b );
    bExp = extractFloatx80Exp( b );
    expDiff = aExp - bExp;
    if ( 0 < expDiff ) goto aExpBigger;
    if ( expDiff < 0 ) goto bExpBigger;
    if ( aExp == 0x7FFF ) {
        if ( (uint64_t) ( ( aSig | bSig )<<1 ) ) {
            return propagateFloatx80NaN(a, b, status);
        }
        float_raise(float_flag_invalid, status);
        return floatx80_default_nan(status);
    }
 #ifndef SOFTFLOAT_68K
	if ( aExp == 0 ) {
		aExp = 1;
		bExp = 1;
	}
#endif
    zSig1 = 0;
    if ( bSig < aSig ) goto aBigger;
    if ( aSig < bSig ) goto bBigger;
    return packFloatx80(status->float_rounding_mode == float_round_down, 0, 0);
 bExpBigger:
    if ( bExp == 0x7FFF ) {
		if ((uint64_t)(bSig << 1)) return propagateFloatx80NaN(a, b, status);
		if (inf_clear_intbit(status)) bSig = 0;
		return packFloatx80(zSign ^ 1, bExp, bSig);
	}
#ifndef SOFTFLOAT_68K
	if ( aExp == 0 ) ++expDiff;
#endif
    shift128RightJamming( aSig, 0, - expDiff, &aSig, &zSig1 );
 bBigger:
    sub128( bSig, 0, aSig, zSig1, &zSig0, &zSig1 );
    zExp = bExp;
    zSign ^= 1;
    goto normalizeRoundAndPack;
 aExpBigger:
    if ( aExp == 0x7FFF ) {
		if ((uint64_t)(aSig << 1)) return propagateFloatx80NaN(a, b, status);
		return inf_clear_intbit(status) ? packFloatx80(extractFloatx80Sign(a), aExp, 0) : a;
	}
#ifndef SOFTFLOAT_68K
	if ( bExp == 0 ) --expDiff;
#endif
    shift128RightJamming( bSig, 0, expDiff, &bSig, &zSig1 );
 aBigger:
    sub128( aSig, 0, bSig, zSig1, &zSig0, &zSig1 );
    zExp = aExp;