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// ============================================================================

//        __

//   \\__/ o\    (C) 2006-2022  Robert Finch, Waterloo

//    \  __ /    All rights reserved.

//     \/_//     robfinch@finitron.ca

//       ||

//

//      DFPDivide128.sv

//    - decimal floating point divider

//    - parameterized width

//

//

// 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.

//

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//    this list of conditions and the following disclaimer in the documentation

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//

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

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//

//      Floating Point Divider

//

//Properties:

//+-inf * +-inf = -+inf    (this is handled by exOver)

//+-inf * 0     = QNaN

//+-0 / +-0      = QNaN

// ============================================================================

import DFPPkg::*;

`define QINFDIV         4'd2

`define QZEROZERO       4'd3

module DFPDivide128(rst, clk, ce, ld, op, a, b, o, done, sign_exe, overflow, underflow);

parameter N=34;

// FADD is a constant that makes the divider width a multiple of four and includes eight extra bits.

input rst;

input clk;

input ce;

input ld;

input op;

input  DFP128 a, b;

output DFP128UD o;

output reg done;

output sign_exe;

output overflow;

output underflow;

// registered outputs

reg sign_exe=0;

reg inf=0;

reg     overflow=0;

reg     underflow=0;

reg so, sxo;

reg [13:0] xo;

reg [(N+1)*4*2-1:0] mo;

DFP128U au, bu;

DFPUnpack128 u01 (a, au);

DFPUnpack128 u02 (b, bu);

// constants

wire [13:0] infXp = 13'h2FFF;   // infinite / NaN - all ones

wire [13:0] bias = 14'h17FF;

// The following is the value for an exponent of zero, with the offset

// eg. 8'h7f for eight bit exponent, 11'h7ff for eleven bit exponent, etc.

// The following is a template for a quiet nan. (MSB=1)

wire [N*4-1:0] qNaN  = {4'h1,{(N-1)*4{1'b0}}};

// variables

wire [(N+2)*4*2-1:0] divo;

// Operands

reg sa, sb;                     // sign bit

reg [N*4-1:0] siga, sigb;

reg az, bz;

reg aInf, bInf;

reg aNan,bNan;

wire done1;

wire signed [7:0] lzcnt;

// -----------------------------------------------------------

// Clock #1

// - decode the input operands

// - derive basic information

// - calculate fraction

// -----------------------------------------------------------

reg ld1;

always @(posedge clk)

        if (ce) sa <= au.sign;

always @(posedge clk)

        if (ce) sb <= bu.sign;

always @(posedge clk)

        if (ce) siga <= au.sig;

always @(posedge clk)

        if (ce) sigb <= bu.sig;

always @(posedge clk)

        if (ce) az <= au.exp==14'd0 && au.sig==136'd0;

always @(posedge clk)

        if (ce) bz <= bu.exp==14'd0 && bu.sig==136'd0;

always @(posedge clk)

        if (ce) aInf <= au.infinity;

always @(posedge clk)

        if (ce) bInf <= bu.infinity;

always @(posedge clk)

        if (ce) aNan <= au.nan;

always @(posedge clk)

        if (ce) bNan <= bu.nan;

ft_delay #(.WID(1), .DEP(1)) udly1 (.clk(clk), .ce(ce), .i(ld), .o(ld1));

// -----------------------------------------------------------

// Clock #2 to N

// - calculate fraction

// -----------------------------------------------------------

wire done3a,done3;

// Perform divide

dfdiv #(N+2) u2 (.clk(clk), .ld(ld1), .a({siga,8'b0}), .b({sigb,8'b0}), .q(divo), .r(), .done(done1), .lzcnt(lzcnt));

wire [7:0] lzcnt_bin = lzcnt[3:0] + (lzcnt[7:4] * 10);

wire [(N+2)*4*2-1:0] divo1 = divo[(N+2)*4*2-1:0] << ({lzcnt_bin,2'b0}+N*4);//WAS FPWID=128?+44

ft_delay #(.WID(1), .DEP(3)) u3 (.clk(clk), .ce(ce), .i(done1), .o(done3a));

assign done3 = done1&done3a;

// -----------------------------------------------------------

// Clock #N+1

// - calculate exponent

// - calculate fraction

// - determine when a NaN is output

// -----------------------------------------------------------

// Compute the exponent.

// - correct the exponent for denormalized operands

// - adjust the difference by the bias (add 127)

// - also factor in the different decimal position for division

reg [15:0] ex1; // sum of exponents

reg qNaNOut;

always @(posedge clk)

  if (ce) ex1 <= au.exp - bu.exp + bias - lzcnt_bin;

always @(posedge clk)

  if (ce) qNaNOut <= (az&bz)|(aInf&bInf);

wire over = 1'b0;

wire under = &ex1[15:14];

reg [3:0] st;

// -----------------------------------------------------------

// Clock #N+3

// -----------------------------------------------------------

always @(posedge clk)

// Simulation likes to see these values reset to zero on reset. Otherwise the

// values propagate in sim as X's.

if (rst) begin

        xo <= 1'd0;

        mo <= 1'd0;

        so <= 1'd0;

        sign_exe <= 1'd0;

        overflow <= 1'd0;

        underflow <= 1'd0;

        done <= 1'b1;

end

else if (ce) begin

  done <= 1'b0;

        if (done3&done1) begin

          done <= 1'b1;

                casez({qNaNOut|aNan|bNan,bInf,bz,over,under})

                5'b1????:               xo <= infXp;    // NaN exponent value

                5'b01???:               xo <= 1'd0;             // divide by inf

                5'b001??:               xo <= infXp;    // divide by zero

                5'b0001?:               xo <= infXp;    // overflow

                5'b00001:               xo <= 1'd0;             // underflow

                default:                xo <= ex1;      // normal or underflow: passthru neg. exp. for normalization

                endcase

                casez({aNan,bNan,qNaNOut,bInf,bz,over,aInf&bInf,az&bz})

                8'b1???????:  begin mo <= {4'h1,au[N*4-1:0],{(N+1)*4-1{1'b0}}}; st[3] <= 1'b1; end

                8'b01??????:  begin mo <= {4'h1,bu[N*4-1:0],{(N+1)*4-1{1'b0}}}; st[3] <= 1'b1; end

                8'b001?????:    begin mo <= {4'h1,qNaN[N*4-1:0]|{aInf,1'b0}|{az,bz},{(N+1)*4-1{1'b0}}}; st[3] <= 1'b1; end

                8'b0001????:    begin mo <= {(N+1)*4*2-1{1'd0}};        st[3] <= 1'b0; end      // div by inf

                8'b00001???:    begin mo <= {(N+1)*4*2-1{1'd0}};        st[3] <= 1'b0; end      // div by zero

                8'b000001??:    begin mo <= {(N+1)*4*2-1{1'd0}};        st[3] <= 1'b0; end      // Inf exponent

                8'b0000001?:    begin mo <= {4'h1,qNaN|`QINFDIV,{(N+1)*4-1{1'b0}}};     st[3] <= 1'b1; end      // infinity / infinity

                8'b00000001:    begin mo <= {4'h1,qNaN|`QZEROZERO,{(N+1)*4-1{1'b0}}};   st[3] <= 1'b1; end      // zero / zero

                default:                begin mo <= divo1[(N+2)*4*2-1:8];       st[3] <= 1'b0; end      // plain div

                endcase

                sign_exe        <= sa & sb;

                overflow        <= over;

                underflow       <= under;

                o.nan <= aNan|bNan|qNaNOut;

                o.snan <= aNan|bNan|qNaNOut;

                o.qnan <= 1'b0;

                o.infinity <= over|aInf;

                o.sign <= sa ^ sb;

                o.exp <= xo;

                o.sig <= mo;

        end

end

endmodule

module DFPDivide128nr(rst, clk, ce, ld, op, a, b, o, rm, done, sign_exe, inf, overflow, underflow);

parameter N=34;

input rst;

input clk;

input ce;

input ld;

input op;

input  DFP128 a, b;

output DFP128 o;

input [2:0] rm;

output sign_exe;

output done;

output inf;

output overflow;

output underflow;

DFP128UD o1;

wire sign_exe1, inf1, overflow1, underflow1;

DFP128UN fpn0;

wire done1, done1a;

DFPDivide128    #(.N(N)) u1 (rst, clk, ce, ld, op, a, b, o1, done1, sign_exe1, overflow1, underflow1);

DFPNormalize128 #(.N(N)) u2(.clk(clk), .ce(ce), .under_i(underflow1), .i(o1), .o(fpn0) );

DFPRound128     #(.N(N)) u3(.clk(clk), .ce(ce), .rm(rm), .i(fpn0), .o(o) );

delay2      #(1)   u4(.clk(clk), .ce(ce), .i(sign_exe1), .o(sign_exe));

delay2      #(1)   u5(.clk(clk), .ce(ce), .i(inf1), .o(inf));

delay2      #(1)   u6(.clk(clk), .ce(ce), .i(overflow1), .o(overflow));

delay2      #(1)   u7(.clk(clk), .ce(ce), .i(underflow1), .o(underflow));

ft_delay        #(.WID(1),.DEP(11))   u8(.clk(clk), .ce(ce), .i(done1), .o(done1a));

assign done = done1&done1a;

endmodule