The terms RISC and CISC don't mean as much as they used to. RISC architectures became more CISC-like when their designers realized the performance penalties of forcing developers to implement missing functionality in software.
A good example of this in MIPS would be the ei/di (atomically enable/disable interrupts) instructions added to MIPS32 rev.2. According to RISC dogma, such instructions would be considered frivolous.
More generally, the simplest possible interface is rarely optimal.