Function floatx80_logn

src/softfloat/softfloat_fpsp.cpp:1084–1211

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

floatx80 floatx80_logn(floatx80 a, float_status *status)
{
	flag aSign;
	int32_t aExp;
	uint64_t aSig, fSig;
	
	int32_t compact, j, k, adjk;
	floatx80 fp0, fp1, fp2, fp3, f, logof2, klog2, saveu;
	
	aSig = extractFloatx80Frac(a);
	aExp = extractFloatx80Exp(a);
	aSign = extractFloatx80Sign(a);
	
	if (aExp == 0x7FFF) {
		if ((uint64_t) (aSig<<1)) return propagateFloatx80NaNOneArg(a, status);
		if (aSign == 0)
			return a;
	}
	
	adjk = 0;
	
	if (aExp == 0) {
		if (aSig == 0) { // zero
			float_raise(float_flag_divbyzero, status);
			return packFloatx80(1, 0x7FFF, floatx80_default_infinity_low);
		}
#if 1
		if ((aSig & one_sig) == 0) { // denormal
			normalizeFloatx80Subnormal(aSig, &aExp, &aSig);
			adjk = -100;
			aExp += 100;
			a = packFloatx80(aSign, aExp, aSig);
		}
#else
		normalizeFloatx80Subnormal(aSig, &aExp, &aSig);
#endif
	}
	
	if (aSign) {
		float_raise(float_flag_invalid, status);
		return floatx80_default_nan(status);
	}
	
	SET_PREC;
	
	compact = floatx80_make_compact(aExp, aSig);
	
	if (compact < 0x3FFEF07D || compact > 0x3FFF8841) { // |X| < 15/16 or |X| > 17/16
		k = aExp - 0x3FFF;
		k += adjk;
		fp1 = int32_to_floatx80(k);
		
		fSig = (aSig & LIT64(0xFE00000000000000)) | LIT64(0x0100000000000000);
		j = (fSig >> 56) & 0x7E; // DISPLACEMENT FOR 1/F
		
		f = packFloatx80(0, 0x3FFF, fSig); // F
		fp0 = packFloatx80(0, 0x3FFF, aSig); // Y