Suppose you are implementing a BCD multiplier. Google says there are reasonably efficient known circuits for this. Say 8x8 -> 16 digits, and trying for a reasonable compromise between speed and number of logic gates.
And suppose the CPU in which this unit is located, also wants reasonably fast binary 32x32 -> 64 bit multiplication. Same input and output registers, same width operands, as the BCD counterpart.
Can the BCD and binary multipliers share circuitry? I know the answer to the corresponding question for adders is yes, because that was done in the 6502, but I have no idea whether the same is true for multipliers.
