Convert from Signed Binary Coded Decimal.
Converts a 128-bit Signed Packed Format (packed decimal - 31 decimal digits followed by a decimal sign) to a 128-bit decimal floating-point value.
_Decimal128 __signed_BCD_to_d128 ( unsigned long long upper, unsigned long long lower);
The signs 0xA, 0xC, 0xE, and 0xF are treated as positive. The signs 0xB and 0xD are treated as negative.