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.

// Generator : SpinalHDL v1.10.1    git head : 2527c7c6b0fb0f95e5e1a5722a0be732b364ce43
// Component : PiMAC
// Git hash  : 82e1b4b4426cb20a6f387f1686876bda014c9247

`timescale 1ns/1ps

module PiMAC (
  input  wire [3:0]    a,
  input  wire [3:0]    b,
  input  wire [3:0]    c,
  output wire [7:0]    result,
  input  wire          clk,
  input  wire          reset
);
// >>> Module Implementation Begin

// <<< Module Implementation End
endmodule




/*
 * Copyright (c) 2024 Steffen Reith 
 * SPDX-License-Identifier: Apache-2.0
 */

`define default_netname none

module tt_um_SteffenReith_PiMACTop (
    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,      // will go high when the design is enabled
    input  wire       clk,      // clock
    input  wire       rst_n     // reset_n - low to reset
);

   // A reset signal for the MAC-unit
  wire reset = !(rst_n && ena);

  // Don't use the IOs as outputs
  assign uio_out = 8'b0000_0000;

  // Set the directions for the IOs 
  assign uio_oe = 8'bZZZZ_0000;

  //Instantiate the PiMAC and connect the signals
  PiMAC piMAC (
    .a(ui_in[3:0]),
    .b(ui_in[7:4]),
    .c(uio_in[3:0]),
    .result(uo_out),
    .reset(reset),
    .clk(clk)
  );

endmodule


Reference solution:
rtl/generated.v: 
  wire       [4:0]    _zz_nodes_1_ACC_1;
  wire       [5:0]    _zz_nodes_2_ACC_2;
  wire       [6:0]    _zz_nodes_3_ACC_3;
  reg        [3:0]    nodes_3_B;
  reg        [3:0]    nodes_3_A;
  reg        [6:0]    nodes_3_ACC_2;
  wire       [7:0]    nodes_3_ACC_3;
  reg        [3:0]    nodes_2_B;
  reg        [3:0]    nodes_2_A;
  reg        [5:0]    nodes_2_ACC_1;
  wire       [6:0]    nodes_2_ACC_2;
  reg        [3:0]    nodes_1_B;
  reg        [3:0]    nodes_1_A;
  reg        [4:0]    nodes_1_ACC_0;
  wire       [5:0]    nodes_1_ACC_1;
  wire       [4:0]    nodes_0_ACC_0;
  wire       [3:0]    nodes_0_C;
  wire       [3:0]    nodes_0_B;
  wire       [3:0]    nodes_0_A;

  assign _zz_nodes_1_ACC_1 = ({1'd0,nodes_1_A} <<< 1'd1);
  assign _zz_nodes_2_ACC_2 = ({2'd0,nodes_2_A} <<< 2'd2);
  assign _zz_nodes_3_ACC_3 = ({3'd0,nodes_3_A} <<< 2'd3);
  assign nodes_0_A = a;
  assign nodes_0_B = b;
  assign nodes_0_C = c;
  assign nodes_0_ACC_0 = ({1'b0,nodes_0_C} + {1'b0,(nodes_0_B[0] ? nodes_0_A : 4'b0000)});
  assign nodes_1_ACC_1 = ({1'b0,nodes_1_ACC_0} + {1'b0,(nodes_1_B[1] ? _zz_nodes_1_ACC_1 : 5'h00)});
  assign nodes_2_ACC_2 = ({1'b0,nodes_2_ACC_1} + {1'b0,(nodes_2_B[2] ? _zz_nodes_2_ACC_2 : 6'h00)});
  assign nodes_3_ACC_3 = ({1'b0,nodes_3_ACC_2} + {1'b0,(nodes_3_B[3] ? _zz_nodes_3_ACC_3 : 7'h00)});
  assign result = nodes_3_ACC_3;
  always @(posedge clk) begin
    nodes_1_A <= nodes_0_A;
    nodes_1_B <= nodes_0_B;
    nodes_1_ACC_0 <= nodes_0_ACC_0;
    nodes_2_A <= nodes_1_A;
    nodes_2_B <= nodes_1_B;
    nodes_2_ACC_1 <= nodes_1_ACC_1;
    nodes_3_A <= nodes_2_A;
    nodes_3_B <= nodes_2_B;
    nodes_3_ACC_2 <= nodes_2_ACC_2;
  end