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`timescale 1ns / 1ps
// ============================================================================
//        __
//   \\__/ o\    (C) 2006-2022  Robert Finch, Waterloo
//    \  __ /    All rights reserved.
//     \/_//     robfinch<remove>@finitron.ca
//       ||
//
//      cntlz.v
//      - count number of leading zeros in a byte
//      - count number of leading ones in a byte
//      - simple fast approach - lookup table
//
// BSD 3-Clause License
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this
//    list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright notice,
//    this list of conditions and the following disclaimer in the documentation
//    and/or other materials provided with the distribution.
//
// 3. Neither the name of the copyright holder nor the names of its
//    contributors may be used to endorse or promote products derived from
//    this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//                                                                          
// ============================================================================

module cntlz8(
        input [7:0] i,
        output reg [3:0] o
);

        always_comb
                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 cntlz80(
        input [79:0] i,
        output [6:0] o
);

    wire [4:0] cnt3;
        wire [5:0] cnt1, cnt2;

        cntlz32 u1 (i[31: 0],cnt1);
        cntlz32 u2 (i[63:32],cnt2);
        cntlz16 u3 (i[79:64],cnt3);

        assign o =
                !cnt3[4] ? {2'b0,cnt3} :
                !cnt2[5] ? {1'b0,cnt2} + 8'd16 :
                 {1'b0,cnt1} + 7'd48;

endmodule


module cntlz96(
        input [95:0] i,
        output [7:0] o
);

        wire [5:0] cnt1, cnt2, cnt3;

        cntlz32 u1 (i[31: 0],cnt1);
        cntlz32 u2 (i[63:32],cnt2);
        cntlz32 u3 (i[95:64],cnt3);

        assign o =
                !cnt3[5] ? cnt3 :
                !cnt2[5] ? cnt2 + 8'd32 :
                 cnt1 + 8'd64;

endmodule


module cntlz128(
        input [127:0] i,
        output [7:0] o
);

        wire [5:0] cnt1, cnt2, cnt3, cnt4;

        cntlz32 u1 (i[31: 0],cnt1);
        cntlz32 u2 (i[63:32],cnt2);
        cntlz32 u3 (i[95:64],cnt3);
        cntlz32 u4 (i[127:96],cnt4);

        assign o =
                !cnt4[5] ? cnt4 :
                !cnt3[5] ? cnt3 + 8'd32 :
                !cnt2[5] ? cnt2 + 8'd64 :
                 cnt1 + 8'd96;

endmodule


module cntlz192(
        input [191:0] i,
        output [7:0] o
);

        wire [5:0] cnt1, cnt2, cnt3, cnt4, cnt5, cnt6;

        cntlz32 u1 (i[31: 0],cnt1);
        cntlz32 u2 (i[63:32],cnt2);
        cntlz32 u3 (i[95:64],cnt3);
        cntlz32 u4 (i[127:96],cnt4);
        cntlz32 u5 (i[159:128],cnt5);
        cntlz32 u6 (i[191:160],cnt6);

        assign o =
                !cnt6[5] ? cnt6 :
                !cnt5[5] ? cnt5 + 8'd32 :
                !cnt4[5] ? cnt4 + 8'd64:
                !cnt3[5] ? cnt3 + 8'd96 :
                !cnt2[5] ? cnt2 + 8'd128 :
                 cnt1 + 8'd160;

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

module cntlz80Reg(
        input clk,
        input ce,
        input [79:0] i,
        output reg [6:0] o
);

        wire [6:0] o1;
        cntlz80 u1 (i,o1);
        always @(posedge clk)
                if (ce) o <= o1;

endmodule

module cntlz96Reg(
        input clk,
        input ce,
        input [95:0] i,
        output reg [7:0] o
);

        wire [7:0] o1;
        cntlz96 u1 (i,o1);
        always @(posedge clk)
                if (ce) o <= o1;

endmodule

module cntlz128Reg(
        input clk,
        input ce,
        input [127:0] i,
        output reg [7:0] o
);

        wire [7:0] o1;
        cntlz128 u1 (i,o1);
        always @(posedge clk)
                if (ce) o <= o1;

endmodule

module cntlz192Reg(
        input clk,
        input ce,
        input [191:0] i,
        output reg [7:0] o
);

        wire [7:0] o1;
        cntlz192 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

module cntlo80(
        input [79:0] i,
        output [6:0] o
);

        cntlz80 u1 (~i,o);

endmodule

module cntlo128(
        input [127:0] i,
        output [7:0] o
);

        cntlz128 u1 (~i,o);

endmodule