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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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