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`timescale 1ns / 1ps

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

//        __

//   \\__/ o\    (C) 2020-2022  Robert Finch, Waterloo

//    \  __ /    All rights reserved.

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

//       ||

//

//      DFPAddsub96.sv

//

// BSD 3-Clause License

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// 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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//

// 3. Neither the name of the copyright holder nor the names of its

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//    this software without specific prior written permission.

//

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

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//

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

import DFPPkg::*;

module DFPAddsub96(clk, ce, rm, op, a, b, o);

input clk;

input ce;

input [2:0] rm;

input op;

input DFP96 a;

input DFP96 b;

output DFP96UD o;

localparam N=25;                        // number of BCD digits

localparam RIP_STAGES = 3;

parameter TRUE = 1'b1;

parameter FALSE = 1'b0;

DFP96U au;

DFP96U bu;

DFPUnpack96 u00 (a, au);

DFPUnpack96 u01 (b, bu);

reg [(N+1)*4-1:0] oaa10;

reg [(N+1)*4-1:0] obb10;

wire [(N+1)*4-1:0] oss10;

wire oss10c;

BCDAddNClk #(.N(N+1)) ubcdadn1

(

        .clk(clk),

        .a({4'h0,oaa10}),

        .b({4'h0,obb10}),

        .o(oss10),

        .ci(1'b0),

        .co(oss10c)

);

wire [(N+1)*4-1:0] odd10;

wire odd10c;

BCDSubtract #(.N(N+1)) ubcdsubn1

(

        .clk(clk),

        .a({4'h00,oaa10}),

        .b({4'h00,obb10}),

        .o(odd10),

        .sgn(odd10c)

);

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

// Clock #1

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

reg op1;

reg az, bz;

always_ff @(posedge clk)

        op1 <= op;

always_ff @(posedge clk)

        az <= au.sig==100'd0 && au.exp==12'd0;

always_ff @(posedge clk)

        bz <= bu.sig==100'd0 && bu.exp==12'd0;

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

// Clock #2

//

// Figure out which operation is really needed an add or subtract ?

// If the signs are the same, use the orignal op,

// otherwise flip the operation

//  a +  b = add,+

//  a + -b = sub, so of larger

// -a +  b = sub, so of larger

// -a + -b = add,-

//  a -  b = sub, so of larger

//  a - -b = add,+

// -a -  b = add,-

// -a - -b = sub, so of larger

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

reg realOp2;

reg op2;

reg [13:0] xa2, xb2;

reg az2, bz2;

reg xa_gt_xb2;

reg [N*4-1:0] siga2, sigb2;

reg sigeq, siga_gt_sigb;

reg expeq;

always_ff @(posedge clk)

  if (ce) realOp2 = op1 ^ au.sign ^ bu.sign;

always_ff @(posedge clk)

  if (ce) op2 <= op1;

always_ff @(posedge clk)

  if (ce) xa2 <= au.exp;

always_ff @(posedge clk)

  if (ce) xb2 <= bu.exp;

always_ff @(posedge clk)

  if (ce) siga2 <= au.sig;

always_ff @(posedge clk)

  if (ce) sigb2 <= bu.sig;

always_ff @(posedge clk)

  if (ce) az2 <= az;

always_ff @(posedge clk)

  if (ce) bz2 <= bz;

always_ff @(posedge clk)

  if (ce)

        xa_gt_xb2 <= au.exp > bu.exp;

always_ff @(posedge clk)

  if (ce) sigeq <= au.sig==bu.sig;

always_ff @(posedge clk)

  if (ce) siga_gt_sigb <= au.sig > bu.sig;

always_ff @(posedge clk)

  if (ce) expeq <= au.exp==bu.exp;

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

// Clock #3

//

// Find out if the result will be zero.

// Determine which fraction to denormalize

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

//

reg [11:0] xa3, xb3;

reg resZero3;

reg xa_gt_xb3;

reg a_gt_b3;

reg op3;

wire sa3, sb3;

wire [2:0] rm3;

reg [N*4-1:0] mfs3;

always_ff @(posedge clk)

  if (ce) resZero3 <= (realOp2 & expeq & sigeq) ||      // subtract, same magnitude

                           (az2 & bz2);               // both a,b zero

always_ff @(posedge clk)

  if (ce) xa3 <= xa2;

always_ff @(posedge clk)

  if (ce) xb3 <= xb2;

always_ff @(posedge clk)

  if (ce) xa_gt_xb3 <= xa_gt_xb2;

always_ff @(posedge clk)

  if (ce) a_gt_b3 <= xa_gt_xb2 | (expeq & siga_gt_sigb);

always_ff @(posedge clk)

  if (ce) op3 <= op2;

always_ff @(posedge clk)

  if (ce) mfs3 = xa_gt_xb2 ? sigb2 : siga2;

ft_delay #(.WID(1), .DEP(2)) udly3c (.clk(clk), .ce(ce), .i(au.sign), .o(sa3));

ft_delay #(.WID(1), .DEP(2)) udly3d (.clk(clk), .ce(ce), .i(bu.sign), .o(sb3));

ft_delay #(.WID(3), .DEP(3)) udly3e (.clk(clk), .ce(ce), .i(rm), .o(rm3));

ft_delay #(.WID(1), .DEP(3)) udly3f (.clk(clk), .ce(ce), .i(au.infinity), .o(aInf3));

ft_delay #(.WID(1), .DEP(3)) udly3g (.clk(clk), .ce(ce), .i(bu.infinity), .o(bInf3));

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

// Clock #4

//

// Compute output exponent

//

// The output exponent is the larger of the two exponents,

// unless a subtract operation is in progress and the two

// numbers are equal, in which case the exponent should be

// zero.

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

reg [11:0] xa4, xb4;

reg [11:0] xo4;

reg xa_gt_xb4;

always_ff @(posedge clk)

  if (ce) xa4 <= xa3;

always_ff @(posedge clk)

  if (ce) xb4 <= xb3;

always_ff @(posedge clk)

        if (ce) xo4 <= resZero3 ? 12'd0 : xa_gt_xb3 ? xa3 : xb3;

always_ff @(posedge clk)

  if (ce) xa_gt_xb4 <= xa_gt_xb3;

// Compute output sign

reg so4;

always_comb

        case ({resZero3,sa3,op3,sb3})   // synopsys full_case parallel_case

        4'b0000: so4 <= 0;                      // + + + = +

        4'b0001: so4 <= !a_gt_b3;       // + + - = sign of larger

        4'b0010: so4 <= !a_gt_b3;       // + - + = sign of larger

        4'b0011: so4 <= 0;                      // + - - = +

        4'b0100: so4 <= a_gt_b3;                // - + + = sign of larger

        4'b0101: so4 <= 1;                      // - + - = -

        4'b0110: so4 <= 1;                      // - - + = -

        4'b0111: so4 <= a_gt_b3;                // - - - = sign of larger

        4'b1000: so4 <= 0;                      //  A +  B, sign = +

        4'b1001: so4 <= (rm3==3'd3);            //  A + -B, sign = + unless rounding down

        4'b1010: so4 <= (rm3==3'd3);            //  A - B, sign = + unless rounding down

        4'b1011: so4 <= 0;                      // A - -B, sign = +

        4'b1100: so4 <= (rm3==3'd3);            // -A -  -B, sign = + unless rounding down

        4'b1101: so4 <= 1;                      // -A + -B, sign = -

        4'b1110: so4 <= 1;                      // -A - +B, sign = -

        4'b1111: so4 <= (rm3==3'd3);            // A - B, sign = + unless rounding down

        endcase

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

// Clock #5

//

// Compute the difference in exponents, provides shift amount

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

reg [11:0] xdiff5;

always_ff @(posedge clk)

  if (ce) xdiff5 <= xa_gt_xb4 ? xa4 - xb4 : xb4 - xa4;

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

// Clock #6

//

// Compute the difference in exponents, provides shift amount

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

// If the difference in the exponent is 24 or greater (assuming 24 nybble dfp or

// less) then all of the bits will be shifted out to zero. There is no need to

// keep track of a difference more than 24.

reg [6:0] xdif6;

wire [N*4-1:0] mfs6;

always_ff @(posedge clk)

  if (ce) xdif6 <= xdiff5 > N ? N : xdiff5[6:0];

ft_delay #(.WID(N*4), .DEP(3)) udly6a (.clk(clk), .ce(ce), .i(mfs3), .o(mfs6));

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

// Clock #7

//

// Determine the sticky bit. The sticky bit is the bitwise or of all the bits

// being shifted out the right side. The sticky bit is computed here to

// reduce the number of regs required.

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

reg sticky6;

wire sticky7;

wire [7:0] xdif7;

wire [N*4-1:0] mfs7;

wire [8:0] xdif6a = {xdif6,2'b00};      // *4

integer n;

always @*

begin

        sticky6 = 1'b0;

        for (n = 0; n < N*4; n = n + 4)

                if (n <= xdif6a)

                        sticky6 = sticky6| mfs6[n]|mfs6[n+1]|mfs6[n+2]|mfs6[n+3];       // non-zero nybble

end

// register inputs to shifter and shift

delay1 #(1)  d16(.clk(clk), .ce(ce), .i(sticky6), .o(sticky7) );

delay1 #(9)  d15(.clk(clk), .ce(ce), .i(xdif6a),   .o(xdif7) );

delay1 #(N*4) d14(.clk(clk), .ce(ce), .i(mfs6),    .o(mfs7) );

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

// Clock #8

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

reg [(N+1)*4-1:0] md8;

wire [N*4-1:0] siga8, sigb8;

wire xa_gt_xb8;

wire a_gt_b8;

always_ff @(posedge clk)

  if (ce) md8 <= ({mfs7,4'b0} >> xdif7)|sticky7; // xdif7 is a multiple of four

// sync control signals

ft_delay #(.WID(1), .DEP(4)) udly8a (.clk(clk), .ce(ce), .i(xa_gt_xb4), .o(xa_gt_xb8));

ft_delay #(.WID(1), .DEP(5)) udly8b (.clk(clk), .ce(ce), .i(a_gt_b3), .o(a_gt_b8));

ft_delay #(.WID(N*4), .DEP(6)) udly8d (.clk(clk), .ce(ce), .i(siga2), .o(siga8));

ft_delay #(.WID(N*4), .DEP(6)) udly8e (.clk(clk), .ce(ce), .i(sigb2), .o(sigb8));

ft_delay #(.WID(1), .DEP(5)) udly8j (.clk(clk), .ce(ce), .i(op3), .o(op8));

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

// Clock #9

// Sort operands and perform add/subtract

// addition can generate an extra bit, subtract can't go negative

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

reg [(N+1)*4-1:0] oa9, ob9;

reg a_gt_b9;

always_ff @(posedge clk)

  if (ce) oa9 <= xa_gt_xb8 ? {siga8,4'b0} : md8;

always_ff @(posedge clk)

  if (ce) ob9 <= xa_gt_xb8 ? md8 : {sigb8,4'b0};

always_ff @(posedge clk)

  if (ce) a_gt_b9 <= a_gt_b8;

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

// Clock #10

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

wire realOp10;

reg [11:0] xo10;

always_ff @(posedge clk)

  if (ce) oaa10 <= a_gt_b9 ? oa9 : ob9;

always_ff @(posedge clk)

  if (ce) obb10 <= a_gt_b9 ? ob9 : oa9;

ft_delay #(.WID(1), .DEP(8)) udly10a (.clk(clk), .ce(ce), .i(realOp2), .o(realOp10));

ft_delay #(.WID(12), .DEP(6)) udly10b (.clk(clk), .ce(ce), .i(xo4), .o(xo10));

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

// Clock #11

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

wire [(N+1)*4-1:0] mab11;

wire mab11c;

wire [N*4-1:0] siga11, sigb11;

wire abInf11;

wire aNan11, bNan11;

wire xoinf11;

wire op11;

ft_delay #(.WID(1), .DEP(8+RIP_STAGES)) udly11a (.clk(clk), .ce(ce), .i(aInf3&bInf3), .o(abInf11));

ft_delay #(.WID(1), .DEP(10+RIP_STAGES)) udly11c (.clk(clk), .ce(ce), .i(au.nan), .o(aNan11));

ft_delay #(.WID(1), .DEP(10+RIP_STAGES)) udly11d (.clk(clk), .ce(ce), .i(bu.nan), .o(bNan11));

ft_delay #(.WID(1), .DEP(3+RIP_STAGES)) udly11e (.clk(clk), .ce(ce), .i(op8), .o(op11));

ft_delay #(.WID(N*4), .DEP(3+RIP_STAGES)) udly11f (.clk(clk), .ce(ce), .i(siga8), .o(siga11));

ft_delay #(.WID(N*4), .DEP(3+RIP_STAGES)) udly11g (.clk(clk), .ce(ce), .i(sigb8), .o(sigb11));

ft_delay #(.WID(1), .DEP(1+RIP_STAGES)) udly11h (.clk(clk), .ce(ce), .i(xo10==12'hBFF), .o(xoinf11));

ft_delay #(.WID((N+1)*4+1), .DEP(1+RIP_STAGES)) udly11i (.clk(clk), .ce(ce), .i(realOp10 ? {odd10c,odd10} : {oss10c,oss10}), .o({mab11c,mab11}));

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

// Clock #12+RIP_STAGES

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

reg [(N+1)*4*2-1:0] mo12;       // mantissa output

reg nan12;

reg qnan12;

reg infinity12;

wire so11;

ft_delay #(.WID(1), .DEP(7)) udly12b (.clk(clk), .ce(ce), .i(so4), .o(so11));

always_ff @(posedge clk)

if (ce)

        nan12 <= aNan11|bNan11;

always_ff @(posedge clk)

if (ce) begin

        infinity12 <= 1'b0;

        qnan12 <= 1'b0;

        casez({abInf11,aNan11,bNan11,xoinf11})

        4'b1???:        // inf +/- inf - generate QNaN on subtract, inf on add

                if (op11) begin

                        mo12 <= {4'h9,{(N+1)*4*2-4{1'd0}}};

                        qnan12 <= 1'b1;

                end

                else begin

                        mo12 <= {(N+1)*2{4'h9}};

                        infinity12 <= 1'b1;

                end

        4'b01??:        mo12 <= {4'b0,siga11[87:0],{(N+1)*4{1'd0}}};

        4'b001?:        mo12 <= {4'b0,sigb11[87:0],{(N+1)*4{1'd0}}};

        4'b0001:        begin mo12 <= {(N+1)*4*2{1'd0}}; infinity12 <= 1'b1; end

        default:        mo12 <= {3'b0,mab11c,mab11,{N*4{1'd0}}};        // mab has an extra lead bit and four trailing bits

        endcase

end

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

// Clock #13

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

ft_delay #(.WID(1), .DEP(1)) u13c (.clk(clk), .ce(ce), .i(nan12), .o(o.nan) );

ft_delay #(.WID(1), .DEP(1)) u13d (.clk(clk), .ce(ce), .i(qnan12), .o(o.qnan) );

ft_delay #(.WID(1), .DEP(1)) u13e (.clk(clk), .ce(ce), .i(infinity12), .o(o.infinity) );

ft_delay #(.WID(1), .DEP(9)) udly13a (.clk(clk), .ce(ce), .i(so4), .o(o.sign));

ft_delay #(.WID(12), .DEP(3)) udly13b (.clk(clk), .ce(ce), .i(xo10), .o(o.exp));

ft_delay #(.WID((N+1)*4*2), .DEP(1)) u13f (.clk(clk), .ce(ce), .i(mo12), .o(o.sig));

ft_delay #(.WID(1), .DEP(1)) udly13g (.clk(clk), .ce(ce), .i(1'b0), .o(o.snan));

endmodule

module DFPAddsub96nr(clk, ce, rm, op, a, b, o);

input clk;              // system clock

input ce;               // core clock enable

input [2:0] rm; // rounding mode

input op;               // operation 0 = add, 1 = subtract

input DFP96 a;  // operand a

input DFP96 b;  // operand b

output DFP96 o; // output

wire DFP96UD o1;

wire DFP96UN fpn0;

DFPAddsub96             u1 (clk, ce, rm, op, a, b, o1);

DFPNormalize96  u2(.clk(clk), .ce(ce), .under_i(1'b0), .i(o1), .o(fpn0) );

DFPRound96              u3(.clk(clk), .ce(ce), .rm(rm), .i(fpn0), .o(o) );

endmodule