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58 lines
1.1 KiB
Verilog
58 lines
1.1 KiB
Verilog
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(* techmap_celltype = "$lcu" *)
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module _85_lcu_han_carlson (P, G, CI, CO);
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parameter WIDTH = 2;
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(* force_downto *)
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input [WIDTH-1:0] P, G;
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input CI;
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(* force_downto *)
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output [WIDTH-1:0] CO;
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integer i, j;
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(* force_downto *)
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reg [WIDTH-1:0] p, g;
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always @* begin
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i = 0;
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p = P;
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g = G;
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// in almost all cases CI will be constant zero
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g[0] = g[0] | (p[0] & CI);
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if (i < $clog2(WIDTH)) begin
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// First layer: BK
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for (j = WIDTH - 1; j >= 0; j = j - 1) begin
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if (j % 2 == 1) begin
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g[j] = g[j] | p[j] & g[j - 1];
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p[j] = p[j] & p[j - 1];
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end
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end
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// Inner (log(WIDTH) - 1) layers: KS
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for (i = 1; i < $clog2(WIDTH); i = i + 1) begin
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for (j = WIDTH - 1; j >= 2**i; j = j - 1) begin
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if (j % 2 == 1) begin
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g[j] = g[j] | p[j] & g[j - 2**i];
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p[j] = p[j] & p[j - 2**i];
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end
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end
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end
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// Last layer: BK
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if (i < ($clog2(WIDTH) + 1)) begin
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for (j = WIDTH - 1; j >= 0; j = j - 1) begin
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if ((j % 2 == 0) && (j > 0)) begin
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g[j] = g[j] | p[j] & g[j - 1];
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p[j] = p[j] & p[j - 1];
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end
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end
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end
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end
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end
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assign CO = g;
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endmodule
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