... ? imm_ext : reg_read_data_2;
// ALU
alu alu_unit(.a(reg_read_data_1),.b(read_data2),.alu_control(ALU_Control),.result(ALU_out),.zero(zero_flag));
// immediate shift 1
assign im_shift_1 = {imm_ext[14:0],1'b0};
//
&nb...