insn_pref
[insn_pref] = {M(mm_pool32c_op, 0, 0, (mm_pref_func << 1), 0, 0), RT | RS | SIMM},
[insn_pref] = {M(pref_op, 0, 0, 0, 0, 0), RS | RT | SIMM},
[insn_pref] = {M6(spec3_op, 0, 0, 0, pref6_op), RS | RT | SIMM9},
build_insn(buf, insn_pref, c, 28, b);
build_insn(buf, insn_pref, c, a, b);