SMADD64#
Format: SMADD64 dest, source1, source2, source3RHS, source3LHS, sourcePredCarryIn
Phase0: SMADD64 FT0, S0{.NEG}{.ABS}, S1{.NEG}{.ABS}, S2{.NEG}{.ABS}, IS0{.NEG}{.ABS}, (P0|_)
Phase1: -
Phase2: -
Description: Signed 64-bit multiply and add with carry-in bit.
FT0 = S0 * S1 + (IS0<<32 | S2) [+P0]