tnum_arshift
struct tnum tnum_arshift(struct tnum a, u8 min_shift, u8 insn_bitness);
dst_reg->var_off = tnum_arshift(tnum_subreg(dst_reg->var_off), umin_val, 32);
dst_reg->var_off = tnum_arshift(dst_reg->var_off, umin_val, 64);