Subversion Repositories nios2ci

--

-- FLS - Find last (most-significant) set bit in word

--

-- Custom instruction for Nios II

--

-- Copyright (C) 2012 Tobias Klauser <tklauser@distanz.ch>

--

-- 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

--

library ieee;

  use ieee.std_logic_1164.all;

  use ieee.std_logic_unsigned.all;

  use ieee.numeric_std.all;

entity fls is

  port(

    signal dataa  : in std_logic_vector(31 downto 0);

    signal result : out std_logic_vector(31 downto 0)

  );

end entity fls;

architecture rtl of fls is

begin

  process(dataa)

    variable word : unsigned(result'range);

    variable ret  : unsigned(result'range);

  begin

    ret := to_unsigned(33, ret'length);

    for i in dataa'reverse_range loop

      if dataa(i) = '1' then

        ret := to_unsigned(i + 1, ret'length);

      end if;

    end loop;

    result <= std_logic_vector(ret);

  end process;

end architecture rtl;