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

//                                                              //

//  Functions for Amber 2 Core                                  //

//                                                              //

//  This file is part of the Amber project                      //

//  http://www.opencores.org/project,amber                      //

//                                                              //

//  Description                                                 //

//  Functions used in more than one module                      //

//                                                              //

//  Author(s):                                                  //

//      - Conor Santifort, csantifort.amber@gmail.com           //

//                                                              //

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

//                                                              //

// Copyright (C) 2010 Authors and OPENCORES.ORG                 //

//                                                              //

// This source file may be used and distributed without         //

// restriction provided that this copyright statement is not    //

// removed from the file and that any derivative work contains  //

// the original copyright notice and the associated disclaimer. //

//                                                              //

// 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 2.1 of the License, or (at your option) any   //

// later version.                                               //

//                                                              //

// This source 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 Lesser General Public License for more //

// details.                                                     //

//                                                              //

// You should have received a copy of the GNU Lesser General    //

// Public License along with this source; if not, download it   //

// from http://www.opencores.org/lgpl.shtml                     //

//                                                              //

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

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

// PC Filter - Remove the status bits 

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

function [31:0] pcf;

input [31:0] pc_reg;

    begin

    pcf = {6'd0, pc_reg[25:2], 2'd0};

    end

endfunction

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

// 4-bit to 16-bit 1-hot decode

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

function [14:0] decode;

input [3:0] reg_sel;

begin

case ( reg_sel )

    4'h0:    decode = 15'h0001;

    4'h1:    decode = 15'h0002;

    4'h2:    decode = 15'h0004;

    4'h3:    decode = 15'h0008;

    4'h4:    decode = 15'h0010;

    4'h5:    decode = 15'h0020;

    4'h6:    decode = 15'h0040;

    4'h7:    decode = 15'h0080;

    4'h8:    decode = 15'h0100;

    4'h9:    decode = 15'h0200;

    4'ha:    decode = 15'h0400;

    4'hb:    decode = 15'h0800;

    4'hc:    decode = 15'h1000;

    4'hd:    decode = 15'h2000;

    4'he:    decode = 15'h4000;

    default: decode = 15'h0000;

endcase

end

endfunction

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

// Convert Stats Bits Mode to one-hot encoded version

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

function [3:0] oh_status_bits_mode;

input [1:0] fn_status_bits_mode;

begin

oh_status_bits_mode =

    fn_status_bits_mode == SVC  ? 1'd1 << OH_SVC  :

    fn_status_bits_mode == IRQ  ? 1'd1 << OH_IRQ  :

    fn_status_bits_mode == FIRQ ? 1'd1 << OH_FIRQ :

                                  1'd1 << OH_USR  ;

end

endfunction

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

// Convert mode into ascii name

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

function [(14*8)-1:0]  mode_name;

input [4:0] mode;

begin

mode_name    = mode == USR  ? "User          " :

               mode == SVC  ? "Supervisor    " :

               mode == IRQ  ? "Interrupt     " :

               mode == FIRQ ? "Fast Interrupt" :

                              "UNKNOWN       " ;

end

endfunction

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

// Conditional Execution Function

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

// EQ Z set

// NE Z clear

// CS C set

// CC C clear

// MI N set

// PL N clear

// VS V set

// VC V clear

// HI C set and Z clear

// LS C clear or Z set

// GE N == V

// LT N != V

// GT Z == 0,N == V

// LE Z == 1 or N != V

// AL Always (unconditional)

// NV Never

function conditional_execute;

input [3:0] condition;

input [3:0] flags;

begin

conditional_execute

               = ( condition == AL                                        ) ||

                 ( condition == EQ  &&  flags[2]                          ) ||

                 ( condition == NE  && !flags[2]                          ) ||

                 ( condition == CS  &&  flags[1]                          ) ||

                 ( condition == CC  && !flags[1]                          ) ||

                 ( condition == MI  &&  flags[3]                          ) ||

                 ( condition == PL  && !flags[3]                          ) ||

                 ( condition == VS  &&  flags[0]                          ) ||

                 ( condition == VC  && !flags[0]                          ) ||

                 ( condition == HI  &&    flags[1] && !flags[2]           ) ||

                 ( condition == LS  &&  (!flags[1] ||  flags[2])          ) ||

                 ( condition == GE  &&  flags[3] == flags[0]              ) ||

                 ( condition == LT  &&  flags[3] != flags[0]              ) ||

                 ( condition == GT  &&  !flags[2] && flags[3] == flags[0] ) ||

                 ( condition == LE  &&  (flags[2] || flags[3] != flags[0])) ;

end

endfunction

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

// Log 2

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

function [31:0] log2;

input    [31:0] num;

integer i;

integer out;

begin

  out = 32'd0;

  for (i=0; i<30; i=i+1)

    if ((2**i > num) && (out == 0))

      out = i-1;

  log2 = out;

end

endfunction