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library ieee;
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use ieee.std_logic_1164.all;
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use ieee.numeric_std.all;
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package float is
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constant SIGN : std_logic_vector( 31 downto 31 ) := ( others => '0' );
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constant EXP : std_logic_vector( 30 downto 23 ) := ( others => '0' );
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constant MANTISSA : std_logic_vector( 22 downto 0 ) := ( others => '0' );
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function find_leftmost( arg : unsigned; value : std_ulogic ) return integer;
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function count_leading_digits( arg : unsigned; value : std_ulogic ) return integer;
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function to_float( arg : std_logic_vector ) return std_logic_vector;
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function to_fixed( arg : std_logic_vector ) return std_logic_vector;
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end package float;
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package body float is
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function find_leftmost( arg : unsigned; value : std_ulogic ) return integer is
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begin
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for i in arg'left downto arg'right loop
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if ( arg( i ) = value ) then
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return i;
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end if;
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end loop;
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return -1;
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end function find_leftmost;
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function count_leading_digits( arg : unsigned; value : std_ulogic ) return integer is
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variable left_most_value : integer range -1 to arg'high;
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variable leading_values : integer range 0 to arg'high;
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begin
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left_most_value := find_leftmost( arg, not value );
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leading_values := 0;
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if ( left_most_value /= -1 ) then
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leading_values := arg'high - left_most_value;
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end if;
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return leading_values;
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end function count_leading_digits;
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function to_float( arg : std_logic_vector ) return std_logic_vector is
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variable y : std_logic_vector( 31 downto 0 );
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variable s : std_logic;
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variable e : unsigned( 7 downto 0 );
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variable m : unsigned( 22 downto 0 );
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variable value : unsigned( 30 downto 0 );
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variable leading_sign_digits : integer range 0 to value'high;
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variable reminding : integer range 0 to value'high;
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begin
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s := arg( 31 );
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if ( s = '0' ) then
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value := unsigned( arg( 30 downto 0 ) );
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else
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value := not unsigned( arg( 30 downto 0 ) );
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value := value +1;
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end if;
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leading_sign_digits := count_leading_digits( value, '0' );
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reminding := value'high - leading_sign_digits;
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e := to_unsigned( 126 - leading_sign_digits, e'length );
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if ( reminding > m'length ) then
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m := value( reminding - 1 downto reminding - m'length );
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elsif ( reminding > 1 ) then
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m := ( others => '0' );
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m( m'high downto m'high - reminding + 1 ) := value( reminding - 1 downto 0 );
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else
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m := ( others => '0' );
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end if;
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if (arg = x"00000000") then
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y := (others => '0');
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else
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y := s & std_logic_vector( e ) & std_logic_vector( m );
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end if;
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return y;
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end function to_float;
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function to_fixed( arg : std_logic_vector ) return std_logic_vector is
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variable y : unsigned( 31 downto 0 );
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variable s : std_logic;
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variable e : unsigned( 7 downto 0 );
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variable m_index_max : integer range -127 to 128;
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begin
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s := arg( 31 );
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e := unsigned(arg(30 downto 23));
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m_index_max := to_integer(signed(30-(126-e)));
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if (arg = x"00000000") then
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y := (others => '0');
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else
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y := (others => '0');
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case m_index_max is
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when 30 => y(30 downto 7):= '1' & unsigned( arg(22 downto 0) );
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when 29 => y(29 downto 6):= '1' & unsigned( arg(22 downto 0) );
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when 28 => y(28 downto 5):= '1' & unsigned( arg(22 downto 0) );
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when 27 => y(27 downto 4):= '1' & unsigned( arg(22 downto 0) );
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when 26 => y(26 downto 3):= '1' & unsigned( arg(22 downto 0) );
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when 25 => y(25 downto 2):= '1' & unsigned( arg(22 downto 0) );
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when 24 => y(24 downto 1):= '1' & unsigned( arg(22 downto 0) );
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when 23 => y(23 downto 0):= '1' & unsigned( arg(22 downto 0) );
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when 22 => y(22 downto 0):= '1' & unsigned( arg(22 downto 1) );
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when 21 => y(21 downto 0):= '1' & unsigned( arg(22 downto 2) );
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when 20 => y(20 downto 0):= '1' & unsigned( arg(22 downto 3) );
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when 19 => y(19 downto 0):= '1' & unsigned( arg(22 downto 4) );
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when 18 => y(18 downto 0):= '1' & unsigned( arg(22 downto 5) );
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when 17 => y(17 downto 0):= '1' & unsigned( arg(22 downto 6) );
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when 16 => y(16 downto 0):= '1' & unsigned( arg(22 downto 7) );
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when 15 => y(15 downto 0):= '1' & unsigned( arg(22 downto 8) );
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when 14 => y(14 downto 0):= '1' & unsigned( arg(22 downto 9) );
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when 13 => y(13 downto 0):= '1' & unsigned( arg(22 downto 10) );
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when 12 => y(12 downto 0):= '1' & unsigned( arg(22 downto 11) );
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when 11 => y(11 downto 0):= '1' & unsigned( arg(22 downto 12) );
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when 10 => y(10 downto 0):= '1' & unsigned( arg(22 downto 13) );
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when 9 => y(9 downto 0):= '1' & unsigned( arg(22 downto 14) );
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when 8 => y(8 downto 0):= '1' & unsigned( arg(22 downto 15) );
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when 7 => y(7 downto 0):= '1' & unsigned( arg(22 downto 16) );
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when 6 => y(6 downto 0):= '1' & unsigned( arg(22 downto 17) );
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when 5 => y(5 downto 0):= '1' & unsigned( arg(22 downto 18) );
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when 4 => y(4 downto 0):= '1' & unsigned( arg(22 downto 19) );
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when 3 => y(3 downto 0):= '1' & unsigned( arg(22 downto 20) );
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when 2 => y(2 downto 0):= '1' & unsigned( arg(22 downto 21) );
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when 1 => y(1 downto 0):= '1' & unsigned( arg(22 downto 22) );
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when 0 => y(0):= '1';
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when others => null;
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end case;
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if ( s = '1' ) then
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y := not(y);
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y:= y + x"00000001";
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end if;
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end if;
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return std_logic_vector( y );
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end function to_fixed;
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end package body float;
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