Accessing all the variables in an Instruction

Can anyone tell me how can I access the defining variable in an instruction?
For example:
%rem = srem i32 %i.0, 10

Using getOperand() in the above instruction gives me only the operands on the LHS, i.e. i.0 and i32 10. How can I access %rem?

Because LLVM IR is in SSA form, the instruction /is/ the 'defining
variable', there is no distinction between the two. Just ask the
instruction for its name.

- David