Function floatx80_tan

src/softfloat/softfloat_fpsp.cpp:1911–2084

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

floatx80 floatx80_tan(floatx80 a, float_status *status)
{
	flag aSign, xSign;
	int32_t aExp, xExp;
	uint64_t aSig, xSig;
	
	int32_t compact, l, n, j;
	floatx80 fp0, fp1, fp2, fp3, fp4, fp5, invtwopi, twopi1, twopi2;
	float32 twoto63;
	flag endflag;
	
	aSig = extractFloatx80Frac(a);
	aExp = extractFloatx80Exp(a);
	aSign = extractFloatx80Sign(a);
	
	if (aExp == 0x7FFF) {
		if ((uint64_t) (aSig<<1)) return propagateFloatx80NaNOneArg(a, status);
		float_raise(float_flag_invalid, status);
		return floatx80_default_nan(status);
	}
	
	if (aExp == 0 && aSig == 0) {
		return packFloatx80(aSign, 0, 0);
	}
	
	SET_PREC;
	
	compact = floatx80_make_compact(aExp, aSig);
	
	fp0 = a;
	
	if (compact < 0x3FD78000 || compact > 0x4004BC7E) { // 2^(-40) > |X| > 15 PI
		if (compact > 0x3FFF8000) { // |X| >= 15 PI
			// REDUCEX
			fp1 = packFloatx80(0, 0, 0);
			if (compact == 0x7FFEFFFF) {
				twopi1 = packFloatx80(aSign ^ 1, 0x7FFE, LIT64(0xC90FDAA200000000));
				twopi2 = packFloatx80(aSign ^ 1, 0x7FDC, LIT64(0x85A308D300000000));
				fp0 = floatx80_add(fp0, twopi1, status);
				fp1 = fp0;
				fp0 = floatx80_add(fp0, twopi2, status);
				fp1 = floatx80_sub(fp1, fp0, status);
				fp1 = floatx80_add(fp1, twopi2, status);
			}
		loop:
			xSign = extractFloatx80Sign(fp0);
			xExp = extractFloatx80Exp(fp0);
			xExp -= 0x3FFF;
			if (xExp <= 28) {
				l = 0;
				endflag = 1;
			} else {
				l = xExp - 27;
				endflag = 0;
			}
			invtwopi = packFloatx80(0, 0x3FFE - l, LIT64(0xA2F9836E4E44152A)); // INVTWOPI
			twopi1 = packFloatx80(0, 0x3FFF + l, LIT64(0xC90FDAA200000000));
			twopi2 = packFloatx80(0, 0x3FDD + l, LIT64(0x85A308D300000000));