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-- This -*- vhdl -*- file is part of GHDL.
-- IEEE 1076.3 compliant numeric bit package body.
-- The implementation is based only on the specifications.
-- Copyright (C) 2015 Tristan Gingold
--
-- GHDL is free software; you can redistribute it and/or modify it under
-- the terms of the GNU General Public License as published by the Free
-- Software Foundation; either version 2, or (at your option) any later
-- version.
--
-- GHDL 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 General Public License
-- for more details.
--
-- You should have received a copy of the GNU General Public License
-- along with GCC; see the file COPYING2. If not see
-- <http://www.gnu.org/licenses/>.
package body NUMERIC_BIT is
constant NO_WARNING : Boolean := False;
constant null_unsigned : unsigned (0 downto 1) := (others => '0');
constant null_signed : signed (0 downto 1) := (others => '0');
subtype nat1 is natural range 0 to 1;
type nat1_to_sl_type is array (nat1) of bit;
constant nat1_to_01 : nat1_to_sl_type := (0 => '0', 1 => '1');
subtype sl_01 is bit;
type carry_array is array (sl_01, sl_01, sl_01) of sl_01;
constant compute_carry : carry_array :=
('0' => ('0' => ('0' => '0', '1' => '0'),
'1' => ('0' => '0', '1' => '1')),
'1' => ('0' => ('0' => '0', '1' => '1'),
'1' => ('0' => '1', '1' => '1')));
constant compute_sum : carry_array :=
('0' => ('0' => ('0' => '0', '1' => '1'),
'1' => ('0' => '1', '1' => '0')),
'1' => ('0' => ('0' => '1', '1' => '0'),
'1' => ('0' => '0', '1' => '1')));
type compare_type is (compare_unknown,
compare_lt,
compare_eq,
compare_gt);
function MAX (L, R : natural) return natural is
begin
if L > R then
return L;
else
return R;
end if;
end MAX;
function TO_INTEGER (ARG : UNSIGNED) return NATURAL
is
variable res : natural := 0;
begin
if arg'length = 0 then
assert NO_WARNING
report "NUMERIC_BIT.TO_INTEGER: null array detected, returning 0"
severity warning;
return 0;
end if;
for i in arg'range loop
res := res + res;
if arg (i) = '1' then
res := res + 1;
end if;
end loop;
return res;
end TO_INTEGER;
function TO_INTEGER (ARG : SIGNED) return INTEGER
is
alias argn : SIGNED (ARG'Length -1 downto 0) is arg;
variable res : integer := 0;
variable b : bit;
begin
if argn'length = 0 then
assert NO_WARNING
report "NUMERIC_BIT.TO_INTEGER: null array detected, returning 0"
severity warning;
return 0;
end if;
if argn (argn'left) = '1' then
-- Negative value
b := '0';
else
b := '1';
end if;
for i in argn'range loop
res := res + res;
if argn (i) = b then
res := res + 1;
end if;
end loop;
if b = '0' then
-- Avoid overflow.
res := -res - 1;
end if;
return res;
end TO_INTEGER;
function TO_UNSIGNED (ARG, SIZE : NATURAL) return UNSIGNED
is
variable res : UNSIGNED (SIZE - 1 downto 0);
variable a : natural := arg;
variable d : nat1;
begin
if size = 0 then
return null_unsigned;
end if;
for i in res'reverse_range loop
d := a rem 2;
res (i) := nat1_to_01 (d);
a := a / 2;
end loop;
if a /= 0 then
assert NO_WARNING
report "NUMERIC_BIT.TO_UNSIGNED: vector is truncated"
severity warning;
end if;
return res;
end TO_UNSIGNED;
function TO_SIGNED (ARG : INTEGER; SIZE : NATURAL) return SIGNED
is
variable res : SIGNED (SIZE - 1 downto 0);
variable v : integer := arg;
variable b0, b1 : bit;
variable d : nat1;
begin
if size = 0 then
return null_signed;
end if;
if arg < 0 then
-- Use one complement to avoid overflow:
-- -v = (not v) + 1
-- not v = -v - 1
-- not v = -(v + 1)
v := -(arg + 1);
b0 := '1';
b1 := '0';
else
v := arg;
b0 := '0';
b1 := '1';
end if;
for i in res'reverse_range loop
d := v rem 2;
v := v / 2;
if d = 0 then
res (i) := b0;
else
res (i) := b1;
end if;
end loop;
if v /= 0 or res (res'left) /= b0 then
assert NO_WARNING
report "NUMERIC_BIT.TO_SIGNED: vector is truncated"
severity warning;
end if;
return res;
end TO_SIGNED;
@ARITH
@LOG
end NUMERIC_BIT;
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