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

//        __

//   \\__/ o\    (C) 2007-2023  Robert Finch, Waterloo

//    \  __ /    All rights reserved.

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

//       ||

//

//      fpCompare64.sv

//    - floating point comparison unit

//    - IEEE 754 representation

//

//

// This source file is free software: you can redistribute it and/or modify

// it under the terms of the GNU Lesser General Public License as published

// by the Free Software Foundation, either version 3 of the License, or

// (at your option) any later version.

//

// This source file is distributed in the hope that it will be useful,

// but WITHOUT ANY WARRANTY; without even the implied warranty of

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

// GNU General Public License for more details.

//

// You should have received a copy of the GNU General Public License

// along with this program.  If not, see .

//

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

import fp64Pkg::*;

module fpCompare64(a, b, o, inf, nan, snan);

input FP64 a, b;

output [15:0] o;

reg [15:0] o;

output inf;

output nan;

output snan;

// Decompose the operands

wire sa;

wire sb;

wire [fp64Pkg::EMSB:0] xa;

wire [fp64Pkg::EMSB:0] xb;

wire [fp64Pkg::FMSB:0] ma;

wire [fp64Pkg::FMSB:0] mb;

wire az, bz;

wire nan_a, nan_b;

wire infa, infb;

fpDecomp64 u1(.i(a), .sgn(sa), .exp(xa), .man(ma), .vz(az), .inf(infa), .qnan(), .snan(), .nan(nan_a) );

fpDecomp64 u2(.i(b), .sgn(sb), .exp(xb), .man(mb), .vz(bz), .inf(infb), .qnan(), .snan(), .nan(nan_b) );

wire unordered = nan_a | nan_b;

wire eq = !unordered & ((az & bz) || (a==b));  // special test for zero

wire ne = !((az & bz) || (a==b));       // special test for zero

wire gt1 = ({xa,ma} > {xb,mb}) | (infa & ~infb);

wire lt1 = ({xa,ma} < {xb,mb}) | (infb & ~infa);

wire lt = sa ^ sb ? sa & !(az & bz): sa ? gt1 : lt1;

always_comb

begin

        o = 'd0;

        o[0] = eq;

        o[1] = lt & !unordered;

        o[2] = (lt|eq) & !unordered;

        o[3] = lt1;

        o[4] = unordered;

        o[7:5] = 3'd0;

        o[8] = ne;

        o[9] = ~lt & !unordered;

        o[10] = ~(lt|eq) & !unordered;

        o[11] = ~lt1;

        o[12] = ~unordered;

end

// an unorder comparison will signal a nan exception

//assign nanx = op!=`FCOR && op!=`FCUN && unordered;

assign nan = nan_a|nan_b|(infa & infb);

assign snan = (nan_a & ~ma[fp64Pkg::FMSB]) | (nan_b & ~mb[fp64Pkg::FMSB]);

assign inf = infa & infb;

endmodule