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

// Project Monophony

//   Wire-Frame 3D Graphics Accelerator IP Core

//

// File:

//   fm_3d_norm.v

//

// Abstract:

//   22-bit floating point normalize function

//

// Author:

//   Kenji Ishimaru (info.info.wf3d@gmail.com)

//

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

//

// Copyright (c) 2015, Kenji Ishimaru

// All rights reserved.

//

// Redistribution and use in source and binary forms, with or without

// modification, are permitted provided that the following conditions are met:

//

//  -Redistributions of source code must retain the above copyright notice,

//   this list of conditions and the following disclaimer.

//  -Redistributions in binary form must reproduce the above copyright notice,

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

//   and/or other materials provided with the distribution.

//

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

// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,

// THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

// PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR

// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,

// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,

// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;

// OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,

// WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR

// OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,

// EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

//

// Revision History

module fm_3d_norm (

  i_s,

  i_e,

  i_f,

  o_b

);

///////////////////////////////////////////

//  port definition

///////////////////////////////////////////

    input         i_s;          // input s1, e5, f2.15

    input  [4:0]  i_e;          // input s1, e5, f2.15

    input  [16:0] i_f;          // input s1, e5, f2.15

    output [21:0] o_b;          // normalized out

///////////////////////////////////////////

//  wire definition

///////////////////////////////////////////

    // intermidiate wire

    wire        w_carry;       // fraction carry bit

    wire [3:0]  w_penc;        // result of priority encode

    wire        w_c_zero;      // fraction zero flag

    wire        w_ce_zero;     // exp zero flag

    wire [15:0] w_lshifted;    // left shifted fraction value

    wire [4:0]  w_lshift_val;  // left shift value

    wire [15:0] w_c_fraction;

    wire [15:0] w_c_frac;

    wire [4:0]  w_c_exp;       // normalized final exp

    wire        w_c_sign;      // final exp

    wire [5:0]  w_incdec_out;  // result of exp incdec

///////////////////////////////////////////

//  assign statement

///////////////////////////////////////////

    assign w_carry  = i_f[16];

// normalize

    // fraction zero flag

    assign w_c_zero = (i_f == 17'h0);

    // fraction priority encode

    assign w_penc = f_prenc(i_f[15:0]);

    // if w_incdec_out[5] == 1, under flow

    assign w_incdec_out = f_incdec(i_e, w_penc, w_carry);

    // left shift value for normalize

    assign  w_lshift_val = w_penc;

    // left shift for nornamize

    assign w_lshifted = i_f[15:0] << w_lshift_val;

    // decide final fraction

    assign w_c_frac = (w_carry) ? i_f[16:1] : w_lshifted;

    // decide final exp

    assign w_c_exp = (w_c_zero|w_incdec_out[5]) ? 5'h0 : w_incdec_out[4:0];

    // exp zero flag

    assign w_ce_zero = (w_c_exp == 5'h0);

    // decide final sign

    assign w_c_sign = i_s & !w_ce_zero;

    // decide final fraction

    assign w_c_fraction = (w_ce_zero) ? 16'h0 : w_c_frac;

    // output port connection

    assign o_b = {w_c_sign, w_c_exp, w_c_fraction};

///////////////////////////////////////////

//  function statement

///////////////////////////////////////////

function [3:0] f_prenc;

  input [15:0] mat;

  begin

    if (mat[15] == 1'b1) begin

      f_prenc = 4'h0;

    end else if (mat[14] == 1'b1) begin

      f_prenc = 4'h1;

    end else if (mat[13] == 1'b1) begin

      f_prenc = 4'h2;

    end else if (mat[12] == 1'b1) begin

      f_prenc = 4'h3;

    end else if (mat[11] == 1'b1) begin

      f_prenc = 4'h4;

    end else if (mat[10] == 1'b1) begin

      f_prenc = 4'h5;

    end else if (mat[9] == 1'b1) begin

      f_prenc = 4'h6;

    end else if (mat[8] == 1'b1) begin

      f_prenc = 4'h7;

    end else if (mat[7] == 1'b1) begin

      f_prenc = 4'h8;

    end else if (mat[6] == 1'b1) begin

      f_prenc = 4'h9;

    end else if (mat[5] == 1'b1) begin

      f_prenc = 4'ha;

    end else if (mat[4] == 1'b1) begin

      f_prenc = 4'hb;

    end else if (mat[3] == 1'b1) begin

      f_prenc = 4'hc;

    end else if (mat[2] == 1'b1) begin

      f_prenc = 4'hd;

    end else if (mat[1] == 1'b1) begin

      f_prenc = 4'he;

    end else begin

      f_prenc = 4'hf;

    end

  end

endfunction

function [5:0] f_incdec;

  input [4:0] a;

  input [3:0] b;

  input       inc;

  reg   [5:0] r_inc;

  reg   [5:0] r_dec;

  reg         r_1f_flag;

  begin

    r_1f_flag = (a == 5'h1f);

    r_inc = a + !r_1f_flag;

    r_dec = a - b;

    f_incdec = (inc) ? r_inc : r_dec;

/*

    if (inc) begin

      if (a == 5'h1f) f_incdec = a;

      else f_incdec = a + 1'b1;

    end else begin

      f_incdec = a - b;

    end

*/

  end

endfunction

endmodule