A microprocessor performs a fused multiply-accumulate operation of a form ±A*B±C. An evaluation is made to detect whether values of A, B, and/or C meet a sufficient condition for performing a joint accumulation of C with partial products of A and B. If so, a joint accumulation of C is done with partial products of A and B and result of the joint accumulation is rounded. If not, then a primary accumulation is done of the partial products of A and B. This generates an unrounded non-redundant result of the primary accumulation. The unrounded result is then truncated to generate an unrounded non-redundant intermediate result vector that excludes one or more least significant bits of the unrounded non-redundant result. A secondary accumulation is then performed, adding or subtracting C to the unrounded non-redundant intermediate result vector. Finally, the result of the secondary accumulation is rounded.