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

//        __

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

//    \  __ /    All rights reserved.

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

//       ||

//

//      df128Toi.sv

//  - convert decimal floating point to integer

//

// BSD 3-Clause License

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

import DFPPkg::*;

module df128Toi (rst, clk, ce, ld, op, i, o, overflow, done);

input rst;

input clk;

input ce;

input ld;

input op;                                               // 1 = signed, 0 = unsigned

input [127:0] i;                // float input

output [127:0] o;               // integer output

output overflow;

output done;

wire done1;

reg done2;

assign done = done1 & done2;

wire [127:0] sig;

DFP128U ui;

DFPUnpack128 uunpk1 (i, ui);

wire [127:0] maxInt = op ? {1'd0,{127{1'b1}}} : {128{1'b1}};            // maximum integer value

wire [13:0] zeroXp = {1'd0,{13{1'b1}}};

reg sgn;                                                                        // sign

always @(posedge clk)

        if (ce) sgn = ui.sign;

wire [13:0] exp = ui.exp;               // exponent

wire iz = i[126:0]==0;                  // zero value (special)

wire [14:0] ovx = exp - zeroXp;

assign overflow  = ovx > 32 && !ovx[14];   // lots of numbers are too big - don't forget one less bit is available due to signed values

wire underflow = exp < zeroXp - 2'd1;                   // value less than 1/2

wire [7:0] shamt = 8'd172 - {(exp - zeroXp),2'd0};      // exp - zeroXp will be <= MSB

wire [176:0] o1 = {ui.sig,41'b0} >> shamt;      // keep an extra bit for rounding

wire [127:0] o2;                // round up

reg [127:0] o3;

DDBCDToBin ub2b1

(

        .rst(rst),

        .clk(clk),

        .ld(ld),

        .bcd({o1[172:1]+o1[0]}),

        .bin(o2),

        .done(done1)

);

always @(posedge clk)

        if (ce) begin

                if (underflow|iz)

                        o3 <= 0;

                else if (overflow)

                        o3 <= maxInt;

                // value between 1/2 and 1 - round up

                else if (exp==zeroXp-1)

                        o3 <= 128'd1;

                // value > 1

                else

                        o3 <= o2;

        end

always @(posedge clk)

        if (ce) done2 <= done1;

assign o = (op & sgn) ? -o3 : o3;                                        // adjust output for correct signed value

endmodule