RISC-V splits widening multiply out into two instructions: one for the high bits and one for the low. Just like 64-bit ARM does.

Integer MAC doesn't exist, and is also hindered by a design decision not to require more than two source operands, so as to allow simple implementations to stay simple. The same reason also prevents RISC-V from having a true conditional move instruction: there is one but the second operand is hard-coded zero.

FMAC exists, but only because it is in the IEEE 754 spec ... and it requires significant op-code space.