Instruction selection: multiple patterns for single instruction

Hi everyone! I’m in the process of adding support for some custom instructions to the MIPS target, and I’d like to add some intrinsics. In particular, I’d like to have these intrinsics to generate instructions which are already selected via their regular patterns. Take for example this format:

class shift_rotate_imm<string opstr, Operand ImmOpnd,
                       RegisterOperand RO, InstrItinClass itin,
                       SDPatternOperator OpNode = null_frag,
                       SDPatternOperator PF = null_frag> :
  InstSE<(outs RO:$rd), (ins RO:$rt, ImmOpnd:$shamt),
         !strconcat(opstr, "\t$rd, $rt, $shamt"),
         [(set RO:$rd, (OpNode RO:$rt, PF:$shamt))], itin, FrmR, opstr> {
  let TwoOperandAliasConstraint = "$rt = $rd";
}

How can I make it so that it is also selected for the pattern (set RO:$rd, (int_mips_mybuiltin RO:$rt, PF:$shamt))?

Thanks!