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/* verilator lint_off WIDTH */
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/* verilator lint_off UNUSED */
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/* verilator lint_off COMBDLY */
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module arithbox (arithop,calc_sz,ci,co,af,ai,sa,sb,opa,opb,resa,cmp);
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input [3:0] arithop;
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input [3:0] calc_sz;
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input [31:0] opa,opb;
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output reg [31:0] resa;
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input ci,ai;
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output reg co,af,sa,sb,cmp;
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wire [4:0] af2,af3,af4,af5;
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assign af2 = opa[3:0]+opb[3:0];
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assign af3 = opa[3:0]+opb[3:0]+ci;
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assign af4 = opa[3:0]-opb[3:0];
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assign af5 = opa[3:0]-opb[3:0]-ci;
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always @(*)
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case (arithop)
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4'b0000 : if (calc_sz==4) begin {co,resa[31:0]} <= opa[31:0] + opb[31:0]; sa<=opa[31]; sb<=opb[31]; af <= af2[4]; cmp <=0; end else
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if (calc_sz==2) begin {co,resa[15:0]} <= opa[15:0] + opb[15:0]; sa<=opa[15]; sb<=opb[15]; af <= af2[4]; resa[31:16] <= opa[31:16]; cmp <=0; end else
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begin {co,resa[ 7:0]} <= opa[ 7:0] + opb[ 7:0]; sa<=opa[ 7]; sb<=opb[ 7]; af <= af2[4]; resa[31: 8] <= opa[31: 8]; cmp <=0; end // add
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4'b0001 : begin resa[31:0] <= opa[31:0] | opb[31:0]; sa<= 1 ; sb<= 0 ; af <= ai ; co <= 0; cmp <=0; end // or
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4'b0010 : if (calc_sz==4) begin {co,resa[31:0]} <= opa[31:0] + opb[31:0] + ci; sa<=opa[31]; sb<=opb[31]; af <= af3[4]; cmp <=0; end else
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if (calc_sz==2) begin {co,resa[15:0]} <= opa[15:0] + opb[15:0] + ci; sa<=opa[15]; sb<=opb[15]; af <= af3[4]; resa[31:16] <= opa[31:16]; cmp <=0; end else
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begin {co,resa[ 7:0]} <= opa[ 7:0] + opb[ 7:0] + ci; sa<=opa[ 7]; sb<=opb[ 7]; af <= af3[4]; resa[31: 8] <= opa[31: 8]; cmp <=0; end // adc
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4'b0011 : if (calc_sz==4) begin {co,resa[31:0]} <= opa[31:0] - opb[31:0] - ci; sa<=opa[31]; sb<=~opb[31];af <= af5[4]; cmp <=0; end else
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if (calc_sz==2) begin {co,resa[15:0]} <= opa[15:0] - opb[15:0] - ci; sa<=opa[15]; sb<=~opb[15];af <= af5[4]; resa[31:16] <= opa[31:16]; cmp <=0; end else
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begin {co,resa[ 7:0]} <= opa[ 7:0] - opb[ 7:0] - ci; sa<=opa[ 7]; sb<=~opb[ 7];af <= af5[4]; resa[31: 8] <= opa[31: 8]; cmp <=0; end // sbc & cmp
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4'b0100 : begin resa[31:0] <= opa[31:0] & opb[31:0]; sa<=1 ; sb<= 0 ; af <= ai ; co <= 0; cmp <= 0; end // and
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4'b0111 : begin
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if (calc_sz==4) begin {co,resa[31:0]} <= opa[31:0] - opb[31:0]; sa<=opa[31]; sb<=~opb[31]; af <= af4[4]; cmp <=1; end else
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if (calc_sz==2) begin {co,resa[15:0]} <= opa[15:0] - opb[15:0]; sa<=opa[15]; sb<=~opb[15]; af <= af4[4]; cmp <=1; resa[31:16] <= opa[31:16]; end else
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begin {co,resa[ 7:0]} <= opa[ 7:0] - opb[ 7:0]; sa<=opa[ 7]; sb<=~opb[ 7]; af <= af4[4]; cmp <=1; resa[31: 8] <= opa[31: 8]; end // sub
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end
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4'b0101 : if (calc_sz==4) begin {co,resa[31:0]} <= opa[31:0] - opb[31:0]; sa<=opa[31]; sb<=~opb[31]; af <= af4[4]; cmp <=0; end else
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if (calc_sz==2) begin {co,resa[15:0]} <= opa[15:0] - opb[15:0]; sa<=opa[15]; sb<=~opb[15]; af <= af4[4]; cmp <=0; resa[31:16] <= opa[31:16]; end else
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begin {co,resa[ 7:0]} <= opa[ 7:0] - opb[ 7:0]; sa<=opa[ 7]; sb<=~opb[ 7]; af <= af4[4]; cmp <=0; resa[31: 8] <= opa[31: 8]; end // sub
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4'b0110 : begin resa[31:0] <= opa[31:0] ^ opb[31:0]; sa<= 1 ; sb<= 0 ; af <= ai; co <= 0; cmp <=0; end // xor
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default : begin resa[31:0] <= opa[31:0] ; sa <= 0 ; sb<= 0 ; af <= ai; co <= ci; cmp <=1; end
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endcase
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endmodule
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