Pollard-s-p-1-algorithm/GCD.v at master · BoolLi/Pollard-s-p-1-algorithm · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
`timescale 1ns / 1ps
//////////////////////////////////////////////////////////////////////////////////
// Company:
// Engineer:
//
// Create Date:    12:59:33 04/09/2015
// Design Name:
// Module Name:    GCD
// Project Name:
// Target Devices:
// Tool versions:
// Description:
//
// Dependencies:
//
// Revision:
// Revision 0.01 - File Created
// Additional Comments:
//
//////////////////////////////////////////////////////////////////////////////////
module GCD(input [31:0] a, input [31:0] b, input reset, input clk, output reg [31:0] gcd, output reg isDone
    );

	reg [31:0] nextInputA;
	reg [31:0] nextInputB;
	reg [31:0] inputA;
	reg [31:0] inputB;
	reg [31:0] nextExponent;
	reg [31:0] exponent;
	reg [31:0] nextGcd;
	reg nextIsDone;

	initial begin
		nextInputA = 0;
		nextInputB = 0;
		inputA = 0;
		inputB = 0;
		nextExponent = 0;
		exponent = 0;
		nextIsDone = 0;
		isDone = 0;
		nextGcd = 0;
		gcd = 0;
	end

	always @(posedge clk) begin
		inputA <= nextInputA;
		inputB <= nextInputB;
		exponent <= nextExponent;
		isDone <= nextIsDone;
		gcd <= nextGcd;
	end

	always @(*) begin
		nextInputA = inputA;
		nextInputB = inputB;
		nextIsDone = isDone;
		nextExponent = exponent;
		nextGcd = gcd;

		if (reset == 1) begin
			nextInputA = 0;
			nextInputB = 0;
			nextExponent = 0;
			nextIsDone = 0;
		end

		else begin
			if (inputA == 0) begin
				nextInputA = a;
				nextInputB = b;
			end

			else begin

				if ((inputA == inputB) & isDone == 0 & inputA > 0) begin
					nextGcd = inputA << exponent;
					nextIsDone = 1;
				end

				else begin
					if ((inputA[0] == 0) & (inputB [0] == 0)) begin
						nextExponent = exponent + 1;
						nextInputA = inputA >> 1;
						nextInputB = inputB >> 1;
					end

					else begin
						nextExponent = exponent;

						if (inputA[0] == 0) begin
							nextInputA = inputA >> 1;
						end

						else begin
							if (inputB[0] ==  0) begin
								nextInputB = inputB >> 1;
							end

							else begin
								if (inputA > inputB) begin
									nextInputA = (inputA - inputB) >> 1;
								end

								else begin
									nextInputB = (inputB - inputA) >> 1;
								end

							end

						end

					end

				end

			end

		end

	end


endmodule