float_pkg_c.vhdl

something i got you may find this useful

-- --------------------------------------------------------------------
-- "float_pkg" package contains functions for floating point math.
-- Please see the documentation for the floating point package.
-- This package should be compiled into "ieee_proposed" and used as follows:
-- use ieee.std_logic_1164.all;
-- use ieee.numeric_std.all;
-- use ieee_proposed.math_utility.all;
-- use ieee_proposed.fixed_pkg.all;
-- use ieee_proposed.float_pkg.all;
--
--  This verison is designed to work with the VHDL-2002 compilers.  Please
--  note the "%%%" comments.  These are where we diverge from the
--  VHDL-200X LRM.
--
-- --------------------------------------------------------------------
-- Version    : $Revision: 1.7 $
-- Date       : $Date: 2007-02-28 10:25:01-05 $
-- --------------------------------------------------------------------

use STD.TEXTIO.all;
library IEEE;
use IEEE.STD_LOGIC_1164.all;
use IEEE.NUMERIC_STD.all;
library ieee_proposed;
use ieee_proposed.math_utility_pkg.all;
use ieee_proposed.fixed_pkg.all;

package float_pkg is
-- generic (
    -- Defaults for sizing routines, when you do a "to_float" this will be
    -- the default size.  Example float32 would be 8 and 23 (8 downto -23)
    constant float_exponent_width : NATURAL    := 8;
    constant float_fraction_width : NATURAL    := 23;
    -- Rounding algorithm, "round_nearest" is default, other valid values
    -- are "round_zero" (truncation), "round_inf" (round up), and
    -- "round_neginf" (round down)
    constant float_round_style    : round_type := round_nearest;
    -- Denormal numbers (very small numbers near zero) true or false
    constant float_denormalize    : BOOLEAN    := true;
    -- Turns on NAN processing (invalid numbers and overflow) true of false
    constant float_check_error    : BOOLEAN    := true;
    -- Guard bits are added to the bottom of every operation for rounding.
    -- any natural number (including 0) are valid.
    constant float_guard_bits     : NATURAL    := 3;
    -- If TRUE, then turn off warnings on "X" propagation
    constant no_warning           : BOOLEAN    := (false
    );

  -- Author David Bishop ([e-mail])
  constant CopyRightNotice : STRING :=
    "Copyright 2006 by IEEE. All rights reserved.";

  -- Note that the size of the vector is not defined here, but in
  -- the package which calls this one.
  type UNRESOLVED_float is array (INTEGER range <>) of STD_ULOGIC;  -- main type
  subtype U_float is UNRESOLVED_float;

  subtype float is UNRESOLVED_float;
  -----------------------------------------------------------------------------
  -- Use the float type to define your own floating point numbers.
  -- There must be a negative index or the packages will error out.
  -- Minimum supported is "subtype float7 is float (3 downto -3);"
  -- "subtype float16 is float (6 downto -9);" is probably the smallest
  -- practical one to use.
  -----------------------------------------------------------------------------

  -- IEEE 754 single precision
  subtype UNRESOLVED_float32 is UNRESOLVED_float (8 downto -23);
--  alias U_float32 is UNRESOLVED_float32;
  subtype U_float32 is UNRESOLVED_float32;
  subtype float32 is float (8 downto -23);
  -----------------------------------------------------------------------------
  -- IEEE-754 single precision floating point.  This is a "float"
  -- in C, and a FLOAT in Fortran.  The exponent is 8 bits wide, and
  -- the fraction is 23 bits wide.  This format can hold roughly 7 decimal
  -- digits.  Infinity is 2**127 = 1.7E38 in this number system.
  -- The bit representation is as follows:
  -- 1 09876543 21098765432109876543210
  -- 8 76543210 12345678901234567890123
  -- 0 00000000 00000000000000000000000
  -- 8 7      0 -1                  -23
  -- +/-   exp.  fraction
  -----------------------------------------------------------------------------

  -- IEEE 754 double precision
  subtype UNRESOLVED_float64 is UNRESOLVED_float (11 downto -52);
--  alias U_float64 is UNRESOLVED_float64;
  subtype U_float64 is UNRESOLVED_float64;
  subtype float64 is float (11 downto -52);
  -----------------------------------------------------------------------------
  -- IEEE-754 double precision floating point.  This is a "double float"
  -- in C, and a FLOAT*8 in Fortran.  The exponent is 11 bits wide, and
  -- the fraction is 52 bits wide.  This format can hold roughly 15 decimal
  -- digits.  Infinity is 2**2047 in this number system.
  -- The bit representation is as follows:
  --  3 21098765432 1098765432109876543210987654321098765432109876543210
  --  1 09876543210 1234567890123456789012345678901234567890123456789012
  --  S EEEEEEEEEEE FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
  -- 11 10        0 -1                                               -52
  -- +/-  exponent    fraction
  -----------------------------------------------------------------------------

  -- IEEE 854 & C extended precision
  subtype UNRESOLVED_float128 is UNRESOLVED_float (15 downto -112);
--  alias U_float128 is UNRESOLVED_float128;
  subtype U_float128 is UNRESOLVED_float128;
  subtype float128 is float (15 downto -112);
  -----------------------------------------------------------------------------
  -- The 128 bit floating point number is "long double" in C (on
  -- some systems this is a 70 bit floating point number) and FLOAT*32
  -- in Fortran.  The exponent is 15 bits wide and the fraction is 112
  -- bits wide. This number can handle approximately 33 decimal digits.
  -- Infinity is 2**32,767 in this number system.
  -----------------------------------------------------------------------------

  -- purpose: Checks for a valid floating point number
  type valid_fpstate is (nan,           -- Signaling NaN (C FP_NAN)
                         quiet_nan,     -- Quiet NaN (C FP_NAN)
                         neg_inf,       -- Negative infinity (C FP_INFINITE)
                         neg_normal,    -- negative normalized nonzero
                         neg_denormal,  -- negative denormalized (FP_SUBNORMAL)
                         neg_zero,      -- -0 (C FP_ZERO)
                         pos_zero,      -- +0 (C FP_ZERO)
                         pos_denormal,  -- Positive denormalized (FP_SUBNORMAL)
                         pos_normal,    -- positive normalized nonzero
                         pos_inf,       -- positive infinity
                         isx);          -- at least one input is unknown

  -- This deferred constant will tell you if the package body is synthesizable
  -- or implemented as real numbers.
  constant fphdlsynth_or_real : BOOLEAN;  -- deferred constant

  -- Returns the class which X falls into
  function Classfp (
    x           : UNRESOLVED_float;              -- floating point input
    check_error : BOOLEAN := float_check_error)  -- check for errors
    return valid_fpstate;

  -- Arithmetic functions, these operators do not require parameters.
  function "abs" (arg : UNRESOLVED_float) return UNRESOLVED_float;
  function "-"   (arg : UNRESOLVED_float) return UNRESOLVED_float;

  -- These allows the base math functions to use the default values
  -- of their parameters.  Thus they do full IEEE floating point.

  function "+"   (l, r : UNRESOLVED_float) return UNRESOLVED_float;
  function "-"   (l, r : UNRESOLVED_float) return UNRESOLVED_float;
  function "*"   (l, r : UNRESOLVED_float) return UNRESOLVED_float;
  function "/"   (l, r : UNRESOLVED_float) return UNRESOLVED_float;
  function "rem" (l, r : UNRESOLVED_float) return UNRESOLVED_float;
  function "mod" (l, r : UNRESOLVED_float) return UNRESOLVED_float;

  -- Basic parameter list
  -- round_style - Selects the rounding algorithm to use
  -- guard - extra bits added to the end if the operation to add precision
  -- check_error - When "false" turns off NAN and overflow checks
  -- denormalize - When "false" turns off denormal number processing

  function add (
    l, r                 : UNRESOLVED_float;  -- floating point input
    constant round_style : round_type := float_round_style;  -- rounding option
    constant guard       : NATURAL    := float_guard_bits;  -- number of guard bits
    constant check_error : BOOLEAN    := float_check_error;  -- check for errors
    constant denormalize : BOOLEAN    := float_denormalize)  -- Use IEEE extended FP
    return UNRESOLVED_float;

  function subtract (
    l, r                 : UNRESOLVED_float;  -- floating point input
    constant round_style : round_type := float_round_style;  -- rounding option
    constant guard       : NATURAL    := float_guard_bits;  -- number of guard bits
    constant check_error : BOOLEAN    := float_check_error;  -- check for errors
    constant denormalize : BOOLEAN    := float_denormalize)  -- Use IEEE extended FP
    return UNRESOLVED_float;

  function multiply (
    l, r                 : UNRESOLVED_float;  -- floating point input
    constant round_style : round_type := float_round_style;  -- rounding option
    constant guard       : NATURAL    := float_guard_bits;  -- number of guard bits
    constant check_error : BOOLEAN    := float_check_error;  -- check for errors
    constant denormalize : BOOLEAN    := float_denormalize)  -- Use IEEE extended FP
    return UNRESOLVED_float;

  function divide (
    l, r                 : UNRESOLVED_float;  -- floating point input
    constant round_style : round_type := float_round_style;  -- rounding option
    constant guard       : NATURAL    := float_guard_bits;  -- number of guard bits
    constant check_error : BOOLEAN    := float_check_error;  -- check for errors
    constant denormalize : BOOLEAN    := float_denormalize)  -- Use IEEE extended FP
    return UNRESOLVED_float;

  function remainder (
    l, r                 : UNRESOLVED_float;  -- floating point input
    constant round_style : round_type := float_round_style;  -- rounding option
    constant guard       : NATURAL    := float_guard_bits;  -- number of guard bits
    constant check_error : BOOLEAN    := float_check_error;  -- check for errors
    constant denormalize : BOOLEAN    := float_denormalize)  -- Use IEEE extended FP
    return UNRESOLVED_float;

  function modulo (
    l, r                 : UNRESOLVED_float;  -- floating point input
    constant round_style : round_type := float_round_style;  -- rounding option
    constant guard       : NATURAL    := float_guard_bits;  -- number of guard bits
    constant check_error : BOOLEAN    := float_check_error;  -- check for errors
    constant denormalize : BOOLEAN    := float_denormalize)  -- Use IEEE extended FP
    return UNRESOLVED_float;

  -- reciprocal
  function reciprocal (
    arg                  : UNRESOLVED_float;  -- floating point input
    constant round_style : round_type := float_round_style;  -- rounding option
    constant guard       : NATURAL    := float_guard_bits;  -- number of guard bits
    constant check_error : BOOLEAN    := float_check_error;  -- check for errors
    constant denormalize : BOOLEAN    := float_denormalize)  -- Use IEEE extended FP
    return UNRESOLVED_float;

  function dividebyp2 (
    l, r                 : UNRESOLVED_float;  -- floating point input
    constant round_style : round_type := float_round_style;  -- rounding option
    constant guard       : NATURAL    := float_guard_bits;  -- number of guard bits
    constant check_error : BOOLEAN    := float_check_error;  -- check for errors
    constant denormalize : BOOLEAN    := float_denormalize)  -- Use IEEE extended FP
    return UNRESOLVED_float;

  -- Multiply accumulate  result = l*r + c
  function mac (
    l, r, c              : UNRESOLVED_float;  -- floating point input
    constant round_style : round_type := float_round_style;  -- rounding option
    constant guard       : NATURAL    := float_guard_bits;  -- number of guard bits
    constant check_error : BOOLEAN    := float_check_error;  -- check for errors
    constant denormalize : BOOLEAN    := float_denormalize)  -- Use IEEE extended FP
    return UNRESOLVED_float;

  -- Square root (all 754 based implementations need this)
  function sqrt (
    arg                  : UNRESOLVED_float;       -- floating point input
    constant round_style : round_type := float_round_style;
    constant guard       : NATURAL    := float_guard_bits;
    constant check_error : BOOLEAN    := float_check_error;
    constant denormalize : BOOLEAN    := float_denormalize)
    return UNRESOLVED_float;

  function Is_Negative (arg : UNRESOLVED_float) return BOOLEAN;

  -----------------------------------------------------------------------------
  -- compare functions
  -- =, /=, >=, <=, <, >, maximum, minimum

  function eq (                               -- equal =
    l, r                 : UNRESOLVED_float;  -- floating point input
    constant check_error : BOOLEAN := float_check_error;
    constant denormalize : BOOLEAN := float_denormalize)
    return BOOLEAN;

  function ne (                               -- not equal /=
    l, r                 : UNRESOLVED_float;  -- floating point input
    constant check_error : BOOLEAN := float_check_error;
    constant denormalize : BOOLEAN := float_denormalize)
    return BOOLEAN;

  function lt (                               -- less than <
    l, r                 : UNRESOLVED_float;  -- floating point input
    constant check_error : BOOLEAN := float_check_error;
    constant denormalize : BOOLEAN := float_denormalize)
    return BOOLEAN;

  function gt (                               -- greater than >
    l, r                 : UNRESOLVED_float;  -- floating point input
    constant check_error : BOOLEAN := float_check_error;
    constant denormalize : BOOLEAN := float_denormalize)
    return BOOLEAN;

  function le (                               -- less than or equal to <=
    l, r                 : UNRESOLVED_float;  -- floating point input
    constant check_error : BOOLEAN := float_check_error;
    constant denormalize : BOOLEAN := float_denormalize)
    return BOOLEAN;

  function ge (                               -- greater than or equal to >=
    l, r                 : UNRESOLVED_float;  -- floating point input
    constant check_error : BOOLEAN := float_check_error;
    constant denormalize : BOOLEAN := float_denormalize)
    return BOOLEAN;