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-- This -*- vhdl -*- file is part of GHDL.
-- IEEE 1076.3 compliant numeric std package body.
-- The implementation is based only on the specifications.
-- Copyright (C) 2015-2021 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 GHDL; see the file COPYING.md. If not see
-- <http://www.gnu.org/licenses/>.
package body NUMERIC_STD 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 std_ulogic;
constant nat1_to_01 : nat1_to_sl_type := (0 => '0', 1 => '1');
subtype sl_01 is std_ulogic range '0' to '1';
subtype sl_x01 is std_ulogic range 'X' to '1';
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 sl_to_x01_array is array (std_ulogic) of sl_x01;
constant sl_to_x01 : sl_to_x01_array :=
('0' | 'L' => '0', '1' | 'H' => '1', others => 'X');
type compare_type is (compare_unknown,
compare_lt,
compare_eq,
compare_gt);
-- Match.
-- '-' matches with everything.
-- '0'/'L' matches, '1'/'H' matches.
type match_table_type is array (std_ulogic, std_ulogic) of boolean;
constant match_table: match_table_type :=
('0' | 'L' => ('0' | 'L' | '-' => true, others => false),
'1' | 'H' => ('1' | 'H' | '-' => true, others => false),
'-' => (others => true),
others => ('-' => true, others => false));
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 argn : UNSIGNED (ARG'Length -1 downto 0);
variable res : natural := 0;
begin
if argn'length = 0 then
assert NO_WARNING
report "NUMERIC_STD.TO_INTEGER: null array detected, returning 0"
severity warning;
return 0;
end if;
argn := TO_01 (ARG, 'X');
if argn (0) = 'X' then
assert NO_WARNING
report
"NUMERIC_STD.TO_INTEGER: non logical value detected, returning 0"
severity warning;
return 0;
end if;
for i in argn'range loop
res := res + res;
if argn (i) = '1' then
res := res + 1;
end if;
end loop;
return res;
end TO_INTEGER;
function TO_INTEGER (ARG : SIGNED) return INTEGER
is
variable argn : SIGNED (ARG'Length -1 downto 0);
variable res : integer := 0;
variable b : STD_ULOGIC;
begin
if argn'length = 0 then
assert NO_WARNING
report "NUMERIC_STD.TO_INTEGER: null array detected, returning 0"
severity warning;
return 0;
end if;
argn := TO_01 (ARG, 'X');
if argn (0) = 'X' then
assert NO_WARNING
report
"NUMERIC_STD.TO_INTEGER: non logical value 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_01 (S : SIGNED; XMAP : STD_LOGIC := '0') return SIGNED
is
subtype res_type is SIGNED (S'Length - 1 downto 0);
variable res : res_type;
alias snorm: res_type is S;
begin
if S'length = 0 then
assert NO_WARNING
report "NUMERIC_STD.TO_01: null array detected"
severity warning;
return null_signed;
else
for i in res_type'range loop
case snorm (i) is
when '0' | 'L' => res (i) := '0';
when '1' | 'H' => res (i) := '1';
when others =>
assert NO_WARNING
report "NUMERIC_STD.TO_01: non logical value detected"
severity warning;
res := (others => XMAP);
exit;
end case;
end loop;
end if;
return res;
end TO_01;
function TO_01 (S : UNSIGNED; XMAP : STD_LOGIC := '0') return UNSIGNED
is
subtype res_type is UNSIGNED (S'Length - 1 downto 0);
variable res : res_type;
alias snorm: res_type is S;
begin
if S'length = 0 then
assert NO_WARNING
report "NUMERIC_STD.TO_01: null array detected"
severity warning;
return null_unsigned;
else
for i in res_type'range loop
case snorm (i) is
when '0' | 'L' => res (i) := '0';
when '1' | 'H' => res (i) := '1';
when others =>
assert NO_WARNING
report "NUMERIC_STD.TO_01: non logical value detected"
severity warning;
res := (others => XMAP);
exit;
end case;
end loop;
end if;
return res;
end TO_01;
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_STD.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 : std_ulogic;
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_STD.TO_SIGNED: vector is truncated"
severity warning;
end if;
return res;
end TO_SIGNED;
function std_match (l, r : std_ulogic) return boolean is
begin
return match_table (l, r);
end std_match;
@MATCH
@ARITH
@LOG
end NUMERIC_STD;
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