require assistance with emiting instructions

["Alex Hill via gcc-help" <gcc-help@xxxxxxxxxxx>]

(define_insn "*<GPR:mode>_load_index"
[
(set
(match_operand:GPR 0 "register_operand" "=r,m")
(mem:GPR
(plus:GPR
(mult:GPR
(match_operand:GPR 1 "register_operand" "%r,m")
(const_int 4))
(match_operand:GPR 2 "register_operand" "r,m"))))
]
""
"ld %0, (%2, %1)"
[(set_attr "mode" "<MODE>")]
)
i try to implement instruction load array variable, or just load_index

i create some kind of instruction but it will emit only on 32bit system, i use it for risc-v 64
when i try use 64-bit it will not emit, if i try const_int 8 GCC wont even compile.

Kind regards Alex Hill.