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/* ===============================================================
        (C) 2006  Robert Finch
        All rights reserved.
        rob@birdcomputer.ca
 
        cntlz.v
                - count number of leading zeros in a byte
                - count number of leading ones in a byte
                - simple fast approach - lookup table
 
        This source code is free for use and modification for
        non-commercial or evaluation purposes, provided this
        copyright statement and disclaimer remains present in
        the file.
 
        If the code is modified, please state the origin and
        note that the code has been modified.
 
        NO WARRANTY.
        THIS Work, IS PROVIDEDED "AS IS" WITH NO WARRANTIES OF
        ANY KIND, WHETHER EXPRESS OR IMPLIED. The user must assume
        the entire risk of using the Work.
 
        IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
        ANY INCIDENTAL, CONSEQUENTIAL, OR PUNITIVE DAMAGES
        WHATSOEVER RELATING TO THE USE OF THIS WORK, OR YOUR
        RELATIONSHIP WITH THE AUTHOR.
 
        IN ADDITION, IN NO EVENT DOES THE AUTHOR AUTHORIZE YOU
        TO USE THE WORK IN APPLICATIONS OR SYSTEMS WHERE THE
        WORK'S FAILURE TO PERFORM CAN REASONABLY BE EXPECTED
        TO RESULT IN A SIGNIFICANT PHYSICAL INJURY, OR IN LOSS
        OF LIFE. ANY SUCH USE BY YOU IS ENTIRELY AT YOUR OWN RISK,
        AND YOU AGREE TO HOLD THE AUTHOR AND CONTRIBUTORS HARMLESS
        FROM ANY CLAIMS OR LOSSES RELATING TO SUCH UNAUTHORIZED
        USE.
 
        Ref: Webpack 8.1i Spartan3-4 xc3s1000-4ft256
        11 LUTs / 6 slices / 12.2 ns
 
=============================================================== */
 
module cntlz8(
        input [7:0] i,
        output reg [3:0] o
);
 
        always @(i)
                case (i)
                8'b00000000:    o = 8;
                8'b00000001:    o = 7;
                8'b00000010:    o = 6;
                8'b00000011:    o = 6;
                8'b00000100:    o = 5;
                8'b00000101:    o = 5;
                8'b00000110:    o = 5;
                8'b00000111:    o = 5;
                8'b00001000:    o = 4;
                8'b00001001:    o = 4;
                8'b00001010:    o = 4;
                8'b00001011:    o = 4;
                8'b00001100:    o = 4;
                8'b00001101:    o = 4;
                8'b00001110:    o = 4;
                8'b00001111:    o = 4;
 
                8'b00010000:    o = 3;
                8'b00010001:    o = 3;
                8'b00010010:    o = 3;
                8'b00010011:    o = 3;
                8'b00010100:    o = 3;
                8'b00010101:    o = 3;
                8'b00010110:    o = 3;
                8'b00010111:    o = 3;
                8'b00011000:    o = 3;
                8'b00011001:    o = 3;
                8'b00011010:    o = 3;
                8'b00011011:    o = 3;
                8'b00011100:    o = 3;
                8'b00011101:    o = 3;
                8'b00011110:    o = 3;
                8'b00011111:    o = 3;
 
                8'b00100000:    o = 2;
                8'b00100001:    o = 2;
                8'b00100010:    o = 2;
                8'b00100011:    o = 2;
                8'b00100100:    o = 2;
                8'b00100101:    o = 2;
                8'b00100110:    o = 2;
                8'b00100111:    o = 2;
                8'b00101000:    o = 2;
                8'b00101001:    o = 2;
                8'b00101010:    o = 2;
                8'b00101011:    o = 2;
                8'b00101100:    o = 2;
                8'b00101101:    o = 2;
                8'b00101110:    o = 2;
                8'b00101111:    o = 2;
 
                8'b00110000:    o = 2;
                8'b00110001:    o = 2;
                8'b00110010:    o = 2;
                8'b00110011:    o = 2;
                8'b00110100:    o = 2;
                8'b00110101:    o = 2;
                8'b00110110:    o = 2;
                8'b00110111:    o = 2;
                8'b00111000:    o = 2;
                8'b00111001:    o = 2;
                8'b00111010:    o = 2;
                8'b00111011:    o = 2;
                8'b00111100:    o = 2;
                8'b00111101:    o = 2;
                8'b00111110:    o = 2;
                8'b00111111:    o = 2;
 
                // 44 - 1       
                8'b01000000:    o = 1;
                8'b01000001:    o = 1;
                8'b01000010:    o = 1;
                8'b01000011:    o = 1;
                8'b01000100:    o = 1;
                8'b01000101:    o = 1;
                8'b01000110:    o = 1;
                8'b01000111:    o = 1;
                8'b01001000:    o = 1;
                8'b01001001:    o = 1;
                8'b01001010:    o = 1;
                8'b01001011:    o = 1;
                8'b01001100:    o = 1;
                8'b01001101:    o = 1;
                8'b01001110:    o = 1;
                8'b01001111:    o = 1;
 
                8'b01010000:    o = 1;
                8'b01010001:    o = 1;
                8'b01010010:    o = 1;
                8'b01010011:    o = 1;
                8'b01010100:    o = 1;
                8'b01010101:    o = 1;
                8'b01010110:    o = 1;
                8'b01010111:    o = 1;
                8'b01011000:    o = 1;
                8'b01011001:    o = 1;
                8'b01011010:    o = 1;
                8'b01011011:    o = 1;
                8'b01011100:    o = 1;
                8'b01011101:    o = 1;
                8'b01011110:    o = 1;
                8'b01011111:    o = 1;
 
                8'b01100000:    o = 1;
                8'b01100001:    o = 1;
                8'b01100010:    o = 1;
                8'b01100011:    o = 1;
                8'b01100100:    o = 1;
                8'b01100101:    o = 1;
                8'b01100110:    o = 1;
                8'b01100111:    o = 1;
                8'b01101000:    o = 1;
                8'b01101001:    o = 1;
                8'b01101010:    o = 1;
                8'b01101011:    o = 1;
                8'b01101100:    o = 1;
                8'b01101101:    o = 1;
                8'b01101110:    o = 1;
                8'b01101111:    o = 1;
 
                8'b01110000:    o = 1;
                8'b01110001:    o = 1;
                8'b01110010:    o = 1;
                8'b01110011:    o = 1;
                8'b01110100:    o = 1;
                8'b01110101:    o = 1;
                8'b01110110:    o = 1;
                8'b01110111:    o = 1;
                8'b01111000:    o = 1;
                8'b01111001:    o = 1;
                8'b01111010:    o = 1;
                8'b01111011:    o = 1;
                8'b01111100:    o = 1;
                8'b01111101:    o = 1;
                8'b01111110:    o = 1;
                8'b01111111:    o = 1;
 
                //  - 2 
                8'b10000000:    o = 0;
                8'b10000001:    o = 0;
                8'b10000010:    o = 0;
                8'b10000011:    o = 0;
                8'b10000100:    o = 0;
                8'b10000101:    o = 0;
                8'b10000110:    o = 0;
                8'b10000111:    o = 0;
                8'b10001000:    o = 0;
                8'b10001001:    o = 0;
                8'b10001010:    o = 0;
                8'b10001011:    o = 0;
                8'b10001100:    o = 0;
                8'b10001101:    o = 0;
                8'b10001110:    o = 0;
                8'b10001111:    o = 0;
 
                8'b10010000:    o = 0;
                8'b10010001:    o = 0;
                8'b10010010:    o = 0;
                8'b10010011:    o = 0;
                8'b10010100:    o = 0;
                8'b10010101:    o = 0;
                8'b10010110:    o = 0;
                8'b10010111:    o = 0;
                8'b10011000:    o = 0;
                8'b10011001:    o = 0;
                8'b10011010:    o = 0;
                8'b10011011:    o = 0;
                8'b10011100:    o = 0;
                8'b10011101:    o = 0;
                8'b10011110:    o = 0;
                8'b10011111:    o = 0;
 
                8'b10100000:    o = 0;
                8'b10100001:    o = 0;
                8'b10100010:    o = 0;
                8'b10100011:    o = 0;
                8'b10100100:    o = 0;
                8'b10100101:    o = 0;
                8'b10100110:    o = 0;
                8'b10100111:    o = 0;
                8'b10101000:    o = 0;
                8'b10101001:    o = 0;
                8'b10101010:    o = 0;
                8'b10101011:    o = 0;
                8'b10101100:    o = 0;
                8'b10101101:    o = 0;
                8'b10101110:    o = 0;
                8'b10101111:    o = 0;
 
                8'b10110000:    o = 0;
                8'b10110001:    o = 0;
                8'b10110010:    o = 0;
                8'b10110011:    o = 0;
                8'b10110100:    o = 0;
                8'b10110101:    o = 0;
                8'b10110110:    o = 0;
                8'b10110111:    o = 0;
                8'b10111000:    o = 0;
                8'b10111001:    o = 0;
                8'b10111010:    o = 0;
                8'b10111011:    o = 0;
                8'b10111100:    o = 0;
                8'b10111101:    o = 0;
                8'b10111110:    o = 0;
                8'b10111111:    o = 0;
 
                // 44 - 3       
                8'b11000000:    o = 0;
                8'b11000001:    o = 0;
                8'b11000010:    o = 0;
                8'b11000011:    o = 0;
                8'b11000100:    o = 0;
                8'b11000101:    o = 0;
                8'b11000110:    o = 0;
                8'b11000111:    o = 0;
                8'b11001000:    o = 0;
                8'b11001001:    o = 0;
                8'b11001010:    o = 0;
                8'b11001011:    o = 0;
                8'b11001100:    o = 0;
                8'b11001101:    o = 0;
                8'b11001110:    o = 0;
                8'b11001111:    o = 0;
 
                8'b11010000:    o = 0;
                8'b11010001:    o = 0;
                8'b11010010:    o = 0;
                8'b11010011:    o = 0;
                8'b11010100:    o = 0;
                8'b11010101:    o = 0;
                8'b11010110:    o = 0;
                8'b11010111:    o = 0;
                8'b11011000:    o = 0;
                8'b11011001:    o = 0;
                8'b11011010:    o = 0;
                8'b11011011:    o = 0;
                8'b11011100:    o = 0;
                8'b11011101:    o = 0;
                8'b11011110:    o = 0;
                8'b11011111:    o = 0;
 
                8'b11100000:    o = 0;
                8'b11100001:    o = 0;
                8'b11100010:    o = 0;
                8'b11100011:    o = 0;
                8'b11100100:    o = 0;
                8'b11100101:    o = 0;
                8'b11100110:    o = 0;
                8'b11100111:    o = 0;
                8'b11101000:    o = 0;
                8'b11101001:    o = 0;
                8'b11101010:    o = 0;
                8'b11101011:    o = 0;
                8'b11101100:    o = 0;
                8'b11101101:    o = 0;
                8'b11101110:    o = 0;
                8'b11101111:    o = 0;
 
                8'b11110000:    o = 0;
                8'b11110001:    o = 0;
                8'b11110010:    o = 0;
                8'b11110011:    o = 0;
                8'b11110100:    o = 0;
                8'b11110101:    o = 0;
                8'b11110110:    o = 0;
                8'b11110111:    o = 0;
                8'b11111000:    o = 0;
                8'b11111001:    o = 0;
                8'b11111010:    o = 0;
                8'b11111011:    o = 0;
                8'b11111100:    o = 0;
                8'b11111101:    o = 0;
                8'b11111110:    o = 0;
                8'b11111111:    o = 0;
 
                endcase
 
 
endmodule
 
 
module cntlz16(
        input [15:0] i,
        output [4:0] o
);
 
        wire [3:0] cnt1, cnt2;
 
        cntlz8 u1 (i[ 7:0],cnt1);
        cntlz8 u2 (i[15:8],cnt2);
 
        assign o = cnt2[3] ? cnt1 + 4'h8 : cnt2;
 
endmodule
 
 
// 39 slices / 67 LUTs / 19.3ns
module cntlz24(
        input [23:0] i,
        output [4:0] o
);
 
        wire [3:0] cnt1, cnt2, cnt3;
 
        // cntlz8 results in faster result than cntlz16
        cntlz8 u1 (i[ 7: 0],cnt1);
        cntlz8 u2 (i[15: 8],cnt2);
        cntlz8 u3 (i[23:16],cnt3);
 
        assign o =
                !cnt3[3] ? cnt3 :
                !cnt2[3] ? cnt2 + 5'd8 :
                 cnt1 + 5'd16;
 
endmodule
 
// 39 slices / 67 LUTs / 19.3ns
module cntlz32(
        input [31:0] i,
        output [5:0] o
);
 
        wire [3:0] cnt1, cnt2, cnt3, cnt4;
 
        // cntlz8 results in faster result than cntlz16
        cntlz8 u1 (i[ 7: 0],cnt1);
        cntlz8 u2 (i[15: 8],cnt2);
        cntlz8 u3 (i[23:16],cnt3);
        cntlz8 u4 (i[31:24],cnt4);
 
        assign o =
                !cnt4[3] ? cnt4 :
                !cnt3[3] ? cnt3 + 6'd8 :
                !cnt2[3] ? cnt2 + 6'd16 :
                 cnt1 + 6'd24;
 
endmodule
 
 
// 88 slices / 154 LUTs / 22.5 ns
module cntlz48(
        input [47:0] i,
        output [5:0] o
);
 
        wire [4:0] cnt1, cnt2, cnt3;
 
        cntlz16 u1 (i[15: 0],cnt1);
        cntlz16 u2 (i[31:16],cnt2);
        cntlz16 u3 (i[47:32],cnt3);
 
        assign o =
                !cnt3[4] ? cnt3 :
                !cnt2[4] ? cnt2 + 7'd16 :
                 cnt1 + 7'd32;
 
endmodule
 
 
// 88 slices / 154 LUTs / 22.5 ns
module cntlz64(
        input [63:0] i,
        output [6:0] o
);
 
        wire [4:0] cnt1, cnt2, cnt3, cnt4;
 
        cntlz16 u1 (i[15: 0],cnt1);
        cntlz16 u2 (i[31:16],cnt2);
        cntlz16 u3 (i[47:32],cnt3);
        cntlz16 u4 (i[63:48],cnt4);
 
        assign o =
                !cnt4[4] ? cnt4 :
                !cnt3[4] ? cnt3 + 7'd16 :
                !cnt2[4] ? cnt2 + 7'd32 :
                 cnt1 + 7'd48;
 
endmodule
 
 
module cntlz32Reg(
        input clk,
        input ce,
        input [31:0] i,
        output reg [5:0] o
);
 
        wire [5:0] o1;
        cntlz32 u1 (i,o1);
        always @(posedge clk)
                if (ce) o <= o1;
 
endmodule
 
 
module cntlz64Reg(
        input clk,
        input ce,
        input [63:0] i,
        output reg [6:0] o
);
 
        wire [6:0] o1;
        cntlz64 u1 (i,o1);
        always @(posedge clk)
                if (ce) o <= o1;
 
endmodule
 
// 5 slices / 10 LUTs / 7.702 ns
module cntlo8(
        input [7:0] i,
        output [3:0] o
);
 
        cntlz8 u1 (~i,o);
 
endmodule
 
 
module cntlo16(
        input [15:0] i,
        output [4:0] o
);
 
        cntlz16 u1 (~i,o);
 
endmodule
 
 
module cntlo32(
        input [31:0] i,
        output [5:0] o
);
 
        cntlz32 u1 (~i,o);
 
endmodule
 
 
module cntlo48(
        input [47:0] i,
        output [5:0] o
);
 
        cntlz48 u1 (~i,o);
 
endmodule
 
 
// 59 slices / 99 LUTs / 14.065 ns
module cntlo64(
        input [63:0] i,
        output [6:0] o
);
 
        cntlz64 u1 (~i,o);
 
endmodule
 
 

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[/] [ft816float/] [trunk/] [rtl/] [verilog/] [lib/] [cntlz.v] - Blame information for rev 5

Line No.	Rev	Author	Line
1	5	robfinch	`/* ===============================================================`
2			`(C) 2006 Robert Finch`
3			`All rights reserved.`
4			`rob@birdcomputer.ca`
5
6			`cntlz.v`
7			`- count number of leading zeros in a byte`
8			`- count number of leading ones in a byte`
9			`- simple fast approach - lookup table`
10
11			`This source code is free for use and modification for`
12			`non-commercial or evaluation purposes, provided this`
13			`copyright statement and disclaimer remains present in`
14			`the file.`
15
16			`If the code is modified, please state the origin and`
17			`note that the code has been modified.`
18
19			`NO WARRANTY.`
20			`THIS Work, IS PROVIDEDED "AS IS" WITH NO WARRANTIES OF`
21			`ANY KIND, WHETHER EXPRESS OR IMPLIED. The user must assume`
22			`the entire risk of using the Work.`
23
24			`IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR`
25			`ANY INCIDENTAL, CONSEQUENTIAL, OR PUNITIVE DAMAGES`
26			`WHATSOEVER RELATING TO THE USE OF THIS WORK, OR YOUR`
27			`RELATIONSHIP WITH THE AUTHOR.`
28
29			`IN ADDITION, IN NO EVENT DOES THE AUTHOR AUTHORIZE YOU`
30			`TO USE THE WORK IN APPLICATIONS OR SYSTEMS WHERE THE`
31			`WORK'S FAILURE TO PERFORM CAN REASONABLY BE EXPECTED`
32			`TO RESULT IN A SIGNIFICANT PHYSICAL INJURY, OR IN LOSS`
33			`OF LIFE. ANY SUCH USE BY YOU IS ENTIRELY AT YOUR OWN RISK,`
34			`AND YOU AGREE TO HOLD THE AUTHOR AND CONTRIBUTORS HARMLESS`
35			`FROM ANY CLAIMS OR LOSSES RELATING TO SUCH UNAUTHORIZED`
36			`USE.`
37
38			`Ref: Webpack 8.1i Spartan3-4 xc3s1000-4ft256`
39			`11 LUTs / 6 slices / 12.2 ns`
40
41			`=============================================================== */`
42
43			`module cntlz8(`
44			`input [7:0] i,`
45			`output reg [3:0] o`
46			`);`
47
48			`always @(i)`
49			`case (i)`
50			`8'b00000000: o = 8;`
51			`8'b00000001: o = 7;`
52			`8'b00000010: o = 6;`
53			`8'b00000011: o = 6;`
54			`8'b00000100: o = 5;`
55			`8'b00000101: o = 5;`
56			`8'b00000110: o = 5;`
57			`8'b00000111: o = 5;`
58			`8'b00001000: o = 4;`
59			`8'b00001001: o = 4;`
60			`8'b00001010: o = 4;`
61			`8'b00001011: o = 4;`
62			`8'b00001100: o = 4;`
63			`8'b00001101: o = 4;`
64			`8'b00001110: o = 4;`
65			`8'b00001111: o = 4;`
66
67			`8'b00010000: o = 3;`
68			`8'b00010001: o = 3;`
69			`8'b00010010: o = 3;`
70			`8'b00010011: o = 3;`
71			`8'b00010100: o = 3;`
72			`8'b00010101: o = 3;`
73			`8'b00010110: o = 3;`
74			`8'b00010111: o = 3;`
75			`8'b00011000: o = 3;`
76			`8'b00011001: o = 3;`
77			`8'b00011010: o = 3;`
78			`8'b00011011: o = 3;`
79			`8'b00011100: o = 3;`
80			`8'b00011101: o = 3;`
81			`8'b00011110: o = 3;`
82			`8'b00011111: o = 3;`
83
84			`8'b00100000: o = 2;`
85			`8'b00100001: o = 2;`
86			`8'b00100010: o = 2;`
87			`8'b00100011: o = 2;`
88			`8'b00100100: o = 2;`
89			`8'b00100101: o = 2;`
90			`8'b00100110: o = 2;`
91			`8'b00100111: o = 2;`
92			`8'b00101000: o = 2;`
93			`8'b00101001: o = 2;`
94			`8'b00101010: o = 2;`
95			`8'b00101011: o = 2;`
96			`8'b00101100: o = 2;`
97			`8'b00101101: o = 2;`
98			`8'b00101110: o = 2;`
99			`8'b00101111: o = 2;`
100
101			`8'b00110000: o = 2;`
102			`8'b00110001: o = 2;`
103			`8'b00110010: o = 2;`
104			`8'b00110011: o = 2;`
105			`8'b00110100: o = 2;`
106			`8'b00110101: o = 2;`
107			`8'b00110110: o = 2;`
108			`8'b00110111: o = 2;`
109			`8'b00111000: o = 2;`
110			`8'b00111001: o = 2;`
111			`8'b00111010: o = 2;`
112			`8'b00111011: o = 2;`
113			`8'b00111100: o = 2;`
114			`8'b00111101: o = 2;`
115			`8'b00111110: o = 2;`
116			`8'b00111111: o = 2;`
117
118			`// 44 - 1`
119			`8'b01000000: o = 1;`
120			`8'b01000001: o = 1;`
121			`8'b01000010: o = 1;`
122			`8'b01000011: o = 1;`
123			`8'b01000100: o = 1;`
124			`8'b01000101: o = 1;`
125			`8'b01000110: o = 1;`
126			`8'b01000111: o = 1;`
127			`8'b01001000: o = 1;`
128			`8'b01001001: o = 1;`
129			`8'b01001010: o = 1;`
130			`8'b01001011: o = 1;`
131			`8'b01001100: o = 1;`
132			`8'b01001101: o = 1;`
133			`8'b01001110: o = 1;`
134			`8'b01001111: o = 1;`
135
136			`8'b01010000: o = 1;`
137			`8'b01010001: o = 1;`
138			`8'b01010010: o = 1;`
139			`8'b01010011: o = 1;`
140			`8'b01010100: o = 1;`
141			`8'b01010101: o = 1;`
142			`8'b01010110: o = 1;`
143			`8'b01010111: o = 1;`
144			`8'b01011000: o = 1;`
145			`8'b01011001: o = 1;`
146			`8'b01011010: o = 1;`
147			`8'b01011011: o = 1;`
148			`8'b01011100: o = 1;`
149			`8'b01011101: o = 1;`
150			`8'b01011110: o = 1;`
151			`8'b01011111: o = 1;`
152
153			`8'b01100000: o = 1;`
154			`8'b01100001: o = 1;`
155			`8'b01100010: o = 1;`
156			`8'b01100011: o = 1;`
157			`8'b01100100: o = 1;`
158			`8'b01100101: o = 1;`
159			`8'b01100110: o = 1;`
160			`8'b01100111: o = 1;`
161			`8'b01101000: o = 1;`
162			`8'b01101001: o = 1;`
163			`8'b01101010: o = 1;`
164			`8'b01101011: o = 1;`
165			`8'b01101100: o = 1;`
166			`8'b01101101: o = 1;`
167			`8'b01101110: o = 1;`
168			`8'b01101111: o = 1;`
169
170			`8'b01110000: o = 1;`
171			`8'b01110001: o = 1;`
172			`8'b01110010: o = 1;`
173			`8'b01110011: o = 1;`
174			`8'b01110100: o = 1;`
175			`8'b01110101: o = 1;`
176			`8'b01110110: o = 1;`
177			`8'b01110111: o = 1;`
178			`8'b01111000: o = 1;`
179			`8'b01111001: o = 1;`
180			`8'b01111010: o = 1;`
181			`8'b01111011: o = 1;`
182			`8'b01111100: o = 1;`
183			`8'b01111101: o = 1;`
184			`8'b01111110: o = 1;`
185			`8'b01111111: o = 1;`
186
187			`// - 2`
188			`8'b10000000: o = 0;`
189			`8'b10000001: o = 0;`
190			`8'b10000010: o = 0;`
191			`8'b10000011: o = 0;`
192			`8'b10000100: o = 0;`
193			`8'b10000101: o = 0;`
194			`8'b10000110: o = 0;`
195			`8'b10000111: o = 0;`
196			`8'b10001000: o = 0;`
197			`8'b10001001: o = 0;`
198			`8'b10001010: o = 0;`
199			`8'b10001011: o = 0;`
200			`8'b10001100: o = 0;`
201			`8'b10001101: o = 0;`
202			`8'b10001110: o = 0;`
203			`8'b10001111: o = 0;`
204
205			`8'b10010000: o = 0;`
206			`8'b10010001: o = 0;`
207			`8'b10010010: o = 0;`
208			`8'b10010011: o = 0;`
209			`8'b10010100: o = 0;`
210			`8'b10010101: o = 0;`
211			`8'b10010110: o = 0;`
212			`8'b10010111: o = 0;`
213			`8'b10011000: o = 0;`
214			`8'b10011001: o = 0;`
215			`8'b10011010: o = 0;`
216			`8'b10011011: o = 0;`
217			`8'b10011100: o = 0;`
218			`8'b10011101: o = 0;`
219			`8'b10011110: o = 0;`
220			`8'b10011111: o = 0;`
221
222			`8'b10100000: o = 0;`
223			`8'b10100001: o = 0;`
224			`8'b10100010: o = 0;`
225			`8'b10100011: o = 0;`
226			`8'b10100100: o = 0;`
227			`8'b10100101: o = 0;`
228			`8'b10100110: o = 0;`
229			`8'b10100111: o = 0;`
230			`8'b10101000: o = 0;`
231			`8'b10101001: o = 0;`
232			`8'b10101010: o = 0;`
233			`8'b10101011: o = 0;`
234			`8'b10101100: o = 0;`
235			`8'b10101101: o = 0;`
236			`8'b10101110: o = 0;`
237			`8'b10101111: o = 0;`
238
239			`8'b10110000: o = 0;`
240			`8'b10110001: o = 0;`
241			`8'b10110010: o = 0;`
242			`8'b10110011: o = 0;`
243			`8'b10110100: o = 0;`
244			`8'b10110101: o = 0;`
245			`8'b10110110: o = 0;`
246			`8'b10110111: o = 0;`
247			`8'b10111000: o = 0;`
248			`8'b10111001: o = 0;`
249			`8'b10111010: o = 0;`
250			`8'b10111011: o = 0;`
251			`8'b10111100: o = 0;`
252			`8'b10111101: o = 0;`
253			`8'b10111110: o = 0;`
254			`8'b10111111: o = 0;`
255
256			`// 44 - 3`
257			`8'b11000000: o = 0;`
258			`8'b11000001: o = 0;`
259			`8'b11000010: o = 0;`
260			`8'b11000011: o = 0;`
261			`8'b11000100: o = 0;`
262			`8'b11000101: o = 0;`
263			`8'b11000110: o = 0;`
264			`8'b11000111: o = 0;`
265			`8'b11001000: o = 0;`
266			`8'b11001001: o = 0;`
267			`8'b11001010: o = 0;`
268			`8'b11001011: o = 0;`
269			`8'b11001100: o = 0;`
270			`8'b11001101: o = 0;`
271			`8'b11001110: o = 0;`
272			`8'b11001111: o = 0;`
273
274			`8'b11010000: o = 0;`
275			`8'b11010001: o = 0;`
276			`8'b11010010: o = 0;`
277			`8'b11010011: o = 0;`
278			`8'b11010100: o = 0;`
279			`8'b11010101: o = 0;`
280			`8'b11010110: o = 0;`
281			`8'b11010111: o = 0;`
282			`8'b11011000: o = 0;`
283			`8'b11011001: o = 0;`
284			`8'b11011010: o = 0;`
285			`8'b11011011: o = 0;`
286			`8'b11011100: o = 0;`
287			`8'b11011101: o = 0;`
288			`8'b11011110: o = 0;`
289			`8'b11011111: o = 0;`
290
291			`8'b11100000: o = 0;`
292			`8'b11100001: o = 0;`
293			`8'b11100010: o = 0;`
294			`8'b11100011: o = 0;`
295			`8'b11100100: o = 0;`
296			`8'b11100101: o = 0;`
297			`8'b11100110: o = 0;`
298			`8'b11100111: o = 0;`
299			`8'b11101000: o = 0;`
300			`8'b11101001: o = 0;`
301			`8'b11101010: o = 0;`
302			`8'b11101011: o = 0;`
303			`8'b11101100: o = 0;`
304			`8'b11101101: o = 0;`
305			`8'b11101110: o = 0;`
306			`8'b11101111: o = 0;`
307
308			`8'b11110000: o = 0;`
309			`8'b11110001: o = 0;`
310			`8'b11110010: o = 0;`
311			`8'b11110011: o = 0;`
312			`8'b11110100: o = 0;`
313			`8'b11110101: o = 0;`
314			`8'b11110110: o = 0;`
315			`8'b11110111: o = 0;`
316			`8'b11111000: o = 0;`
317			`8'b11111001: o = 0;`
318			`8'b11111010: o = 0;`
319			`8'b11111011: o = 0;`
320			`8'b11111100: o = 0;`
321			`8'b11111101: o = 0;`
322			`8'b11111110: o = 0;`
323			`8'b11111111: o = 0;`
324
325			`endcase`
326
327
328			`endmodule`
329
330
331			`module cntlz16(`
332			`input [15:0] i,`
333			`output [4:0] o`
334			`);`
335
336			`wire [3:0] cnt1, cnt2;`
337
338			`cntlz8 u1 (i[ 7:0],cnt1);`
339			`cntlz8 u2 (i[15:8],cnt2);`
340
341			`assign o = cnt2[3] ? cnt1 + 4'h8 : cnt2;`
342
343			`endmodule`
344
345
346			`// 39 slices / 67 LUTs / 19.3ns`
347			`module cntlz24(`
348			`input [23:0] i,`
349			`output [4:0] o`
350			`);`
351
352			`wire [3:0] cnt1, cnt2, cnt3;`
353
354			`// cntlz8 results in faster result than cntlz16`
355			`cntlz8 u1 (i[ 7: 0],cnt1);`
356			`cntlz8 u2 (i[15: 8],cnt2);`
357			`cntlz8 u3 (i[23:16],cnt3);`
358
359			`assign o =`
360			`!cnt3[3] ? cnt3 :`
361			`!cnt2[3] ? cnt2 + 5'd8 :`
362			`cnt1 + 5'd16;`
363
364			`endmodule`
365
366			`// 39 slices / 67 LUTs / 19.3ns`
367			`module cntlz32(`
368			`input [31:0] i,`
369			`output [5:0] o`
370			`);`
371
372			`wire [3:0] cnt1, cnt2, cnt3, cnt4;`
373
374			`// cntlz8 results in faster result than cntlz16`
375			`cntlz8 u1 (i[ 7: 0],cnt1);`
376			`cntlz8 u2 (i[15: 8],cnt2);`
377			`cntlz8 u3 (i[23:16],cnt3);`
378			`cntlz8 u4 (i[31:24],cnt4);`
379
380			`assign o =`
381			`!cnt4[3] ? cnt4 :`
382			`!cnt3[3] ? cnt3 + 6'd8 :`
383			`!cnt2[3] ? cnt2 + 6'd16 :`
384			`cnt1 + 6'd24;`
385
386			`endmodule`
387
388
389			`// 88 slices / 154 LUTs / 22.5 ns`
390			`module cntlz48(`
391			`input [47:0] i,`
392			`output [5:0] o`
393			`);`
394
395			`wire [4:0] cnt1, cnt2, cnt3;`
396
397			`cntlz16 u1 (i[15: 0],cnt1);`
398			`cntlz16 u2 (i[31:16],cnt2);`
399			`cntlz16 u3 (i[47:32],cnt3);`
400
401			`assign o =`
402			`!cnt3[4] ? cnt3 :`
403			`!cnt2[4] ? cnt2 + 7'd16 :`
404			`cnt1 + 7'd32;`
405
406			`endmodule`
407
408
409			`// 88 slices / 154 LUTs / 22.5 ns`
410			`module cntlz64(`
411			`input [63:0] i,`
412			`output [6:0] o`
413			`);`
414
415			`wire [4:0] cnt1, cnt2, cnt3, cnt4;`
416
417			`cntlz16 u1 (i[15: 0],cnt1);`
418			`cntlz16 u2 (i[31:16],cnt2);`
419			`cntlz16 u3 (i[47:32],cnt3);`
420			`cntlz16 u4 (i[63:48],cnt4);`
421
422			`assign o =`
423			`!cnt4[4] ? cnt4 :`
424			`!cnt3[4] ? cnt3 + 7'd16 :`
425			`!cnt2[4] ? cnt2 + 7'd32 :`
426			`cnt1 + 7'd48;`
427
428			`endmodule`
429
430
431			`module cntlz32Reg(`
432			`input clk,`
433			`input ce,`
434			`input [31:0] i,`
435			`output reg [5:0] o`
436			`);`
437
438			`wire [5:0] o1;`
439			`cntlz32 u1 (i,o1);`
440			`always @(posedge clk)`
441			`if (ce) o <= o1;`
442
443			`endmodule`
444
445
446			`module cntlz64Reg(`
447			`input clk,`
448			`input ce,`
449			`input [63:0] i,`
450			`output reg [6:0] o`
451			`);`
452
453			`wire [6:0] o1;`
454			`cntlz64 u1 (i,o1);`
455			`always @(posedge clk)`
456			`if (ce) o <= o1;`
457
458			`endmodule`
459
460			`// 5 slices / 10 LUTs / 7.702 ns`
461			`module cntlo8(`
462			`input [7:0] i,`
463			`output [3:0] o`
464			`);`
465
466			`cntlz8 u1 (~i,o);`
467
468			`endmodule`
469
470
471			`module cntlo16(`
472			`input [15:0] i,`
473			`output [4:0] o`
474			`);`
475
476			`cntlz16 u1 (~i,o);`
477
478			`endmodule`
479
480
481			`module cntlo32(`
482			`input [31:0] i,`
483			`output [5:0] o`
484			`);`
485
486			`cntlz32 u1 (~i,o);`
487
488			`endmodule`
489
490
491			`module cntlo48(`
492			`input [47:0] i,`
493			`output [5:0] o`
494			`);`
495
496			`cntlz48 u1 (~i,o);`
497
498			`endmodule`
499
500
501			`// 59 slices / 99 LUTs / 14.065 ns`
502			`module cntlo64(`
503			`input [63:0] i,`
504			`output [6:0] o`
505			`);`
506
507			`cntlz64 u1 (~i,o);`
508
509			`endmodule`
510
511