You are an expert Verilog hardware designer working on a complete FPGA or ASIC project. You are given the full source code of a Verilog project. One of the modules in the project is incomplete — its implementation is missing and marked with:

// >>> Module Implementation Begin

// <<< Module Implementation End

Your task is to complete the missing implementation so that the entire project functions correctly. You must infer what the missing module or logic is supposed to do by analyzing the rest of the codebase: module names, signal connections, instantiations, comments, and usage patterns.

Follow these rules:

1. Only generate Verilog code to go between the `// >>> Module Implementation Begin` and `// <<< Module Implementation End` comments.
2. Use Verilog-2001 syntax. Ensure the code is synthesizable.
3. Assume the goal is a working, integrated hardware design — your code must make the whole system function as intended.
4. Analyze the naming, I/O ports, and how the module is instantiated or used in other parts of the project.
5. Implement correct behavior based on design context. Do not guess randomly — reason it out.
6. Avoid vendor-specific features unless explicitly required.
7. Do not output comments, explanation, or anything outside the required code region unless explicitly asked.

Your output should contain **only the Verilog code** that fits inside the marked region.

/*
 * Copyright (c) 2024 Your Name
 * SPDX-License-Identifier: Apache-2.0
 */

`default_nettype none

module tt_um_array_mult_structural(
    input  wire [7:0] ui_in,    // Dedicated inputs
    output wire [7:0] uo_out,   // Dedicated outputs
    input  wire [7:0] uio_in,   // IOs: Input path
    output wire [7:0] uio_out,  // IOs: Output path
    output wire [7:0] uio_oe,   // IOs: Enable path (active high: 0=input, 1=output)
    input  wire       ena,      // always 1 when the design is powered, so you can ignore it
    input  wire       clk,      // clock
    input  wire       rst_n     // reset_n - low to reset
);
// >>> Module Implementation Begin

// <<< Module Implementation End
endmodule




module full_adder(
    input x_in, y_in, c_in,
    output s_out, c_out
    );
    
    wire w1, w2, w3;
    
    xor(w1, x_in, y_in);
    xor(s_out, w1, c_in);
    and(w2, w1, c_in);
    and(w3, x_in, y_in);
    or(c_out, w2, w3);
endmodule



Reference solution:
rtl/generated.v: 
  // All output pins must be assigned. If not used, assign to 0.
  
    wire [3:0] m = ui_in[7:4];    
    wire [3:0] q = ui_in[3:0]; 
    wire [7:0] p;

    wire [3:0] s0_out, s1_out, s2_out, s3_out, s4_out;
    wire [3:0] c0_out, c1_out, c2_out, c3_out, c4_out;
    wire [3:0] m0q_in, m1q_in, m2q_in, m3q_in;
    
    // CSA row 0
    assign m0q_in[0] = m[0] * q[0];
    assign m0q_in[1] = m[0] * q[1];
    assign m0q_in[2] = m[0] * q[2];
    assign m0q_in[3] = m[0] * q[3];
    full_adder fa_m0q0 (m0q_in[0], 1'b0, 1'b0, s0_out[0], c0_out[0]);
    full_adder fa_m0q1 (m0q_in[1], 1'b0, 1'b0, s0_out[1], c0_out[1]);
    full_adder fa_m0q2 (m0q_in[2], 1'b0, 1'b0, s0_out[2], c0_out[2]);
    full_adder fa_m0q3 (m0q_in[3], 1'b0, 1'b0, s0_out[3], c0_out[3]);
    
    // CSA row 1
    assign m1q_in[0] = m[1] * q[0];
    assign m1q_in[1] = m[1] * q[1];
    assign m1q_in[2] = m[1] * q[2];
    assign m1q_in[3] = m[1] * q[3];
    full_adder fa_m1q0 (m1q_in[0], s0_out[1], c0_out[0], s1_out[0], c1_out[0]);
    full_adder fa_m1q1 (m1q_in[1], s0_out[2], c0_out[1], s1_out[1], c1_out[1]);
    full_adder fa_m1q2 (m1q_in[2], s0_out[3], c0_out[2], s1_out[2], c1_out[2]);
    full_adder fa_m1q3 (m1q_in[3], 1'b0, c0_out[3], s1_out[3], c1_out[3]);
    
    // CSA row 2
    assign m2q_in[0] = m[2] * q[0];
    assign m2q_in[1] = m[2] * q[1];
    assign m2q_in[2] = m[2] * q[2];
    assign m2q_in[3] = m[2] * q[3];
    full_adder fa_m2q0 (m2q_in[0], s1_out[1], c1_out[0], s2_out[0], c2_out[0]);
    full_adder fa_m2q1 (m2q_in[1], s1_out[2], c1_out[1], s2_out[1], c2_out[1]);
    full_adder fa_m2q2 (m2q_in[2], s1_out[3], c1_out[2], s2_out[2], c2_out[2]);
    full_adder fa_m2q3 (m2q_in[3], 1'b0, c1_out[3], s2_out[3], c2_out[3]);
    
    // CSA row 3
    assign m3q_in[0] = m[3] * q[0];
    assign m3q_in[1] = m[3] * q[1];
    assign m3q_in[2] = m[3] * q[2];
    assign m3q_in[3] = m[3] * q[3];
    full_adder fa_m3q0 (m3q_in[0], s2_out[1], c2_out[0], s3_out[0], c3_out[0]);
    full_adder fa_m3q1 (m3q_in[1], s2_out[2], c2_out[1], s3_out[1], c3_out[1]);
    full_adder fa_m3q2 (m3q_in[2], s2_out[3], c2_out[2], s3_out[2], c3_out[2]);
    full_adder fa_m3q3 (m3q_in[3], 1'b0, c2_out[3], s3_out[3], c3_out[3]);

    // CPA row 4
    full_adder fa_cp4(s3_out[1], c3_out[0], 1'b0, s4_out[0], c4_out[0]); 
    full_adder fa_cp5(s3_out[2], c3_out[1], c4_out[0], s4_out[1], c4_out[1]); 
    full_adder fa_cp6(s3_out[3], c3_out[2], c4_out[1], s4_out[2], c4_out[2]); 
    full_adder fa_cp7(1'b0, c3_out[3], c4_out[2], s4_out[3], c4_out[3]); 
    assign p = {s4_out[3], s4_out[2], s4_out[1], s4_out[0], s3_out[0], s2_out[0], s1_out[0], s0_out[0]};

    assign uo_out = p;

    assign uio_out = 0;
    assign uio_oe  = 0;

    // List all unused inputs to prevent warnings
    wire _unused = &{ena, clk, rst_n, uio_in, 1'b0};