helpers.vhdl

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

library work;

package helpers is
	function fls_32 (val: std_ulogic_vector(31 downto 0)) return integer;
	function ffs_32 (val: std_ulogic_vector(31 downto 0)) return integer;

	function fls_64 (val: std_ulogic_vector(63 downto 0)) return integer;
	function ffs_64 (val: std_ulogic_vector(63 downto 0)) return integer;

	function popcnt8(val: std_ulogic_vector(7 downto 0)) return std_ulogic_vector;
	function popcnt32(val: std_ulogic_vector(31 downto 0)) return std_ulogic_vector;
	function popcnt64(val: std_ulogic_vector(63 downto 0)) return std_ulogic_vector;

	function cmp_one_byte(a, b: std_ulogic_vector(7 downto 0)) return std_ulogic_vector;

	function ppc_signed_compare(a, b: signed(63 downto 0)) return std_ulogic_vector;
	function ppc_unsigned_compare(a, b: unsigned(63 downto 0)) return std_ulogic_vector;

	function ra_or_zero(ra: std_ulogic_vector(63 downto 0); reg: std_ulogic_vector(4 downto 0)) return std_ulogic_vector;

	function byte_reverse(val: std_ulogic_vector(63 downto 0); size: integer) return std_ulogic_vector;

	function sign_extend(val: std_ulogic_vector(63 downto 0); size: natural) return std_ulogic_vector;
end package helpers;

package body helpers is
	function fls_32 (val: std_ulogic_vector(31 downto 0)) return integer is
		variable ret: integer;
	begin
		ret := 32;
		for i in val'range loop
			if val(i) = '1' then
				ret := 31 - i;
				exit;
			end if;
		end loop;

		return ret;
	end;

	function ffs_32 (val: std_ulogic_vector(31 downto 0)) return integer is
		variable ret: integer;
	begin
		ret := 32;
		for i in val'reverse_range loop
			if val(i) = '1' then
				ret := i;
				exit;
			end if;
		end loop;

		return ret;
	end;

	function fls_64 (val: std_ulogic_vector(63 downto 0)) return integer is
		variable ret: integer;
	begin
		ret := 64;
		for i in val'range loop
			if val(i) = '1' then
				ret := 63 - i;
				exit;
			end if;
		end loop;

		return ret;
	end;

	function ffs_64 (val: std_ulogic_vector(63 downto 0)) return integer is
		variable ret: integer;
	begin
		ret := 64;
		for i in val'reverse_range loop
			if val(i) = '1' then
				ret := i;
				exit;
			end if;
		end loop;

		return ret;
	end;

	function popcnt8(val: std_ulogic_vector(7 downto 0)) return std_ulogic_vector is
		variable ret: unsigned(3 downto 0) := (others => '0');
	begin
		for i in val'range loop
			ret := ret + ("000" & val(i));
		end loop;

		return std_ulogic_vector(resize(ret, val'length));
	end;

	function popcnt32(val: std_ulogic_vector(31 downto 0)) return std_ulogic_vector is
		variable ret: unsigned(5 downto 0) := (others => '0');
	begin
		for i in val'range loop
			ret := ret + ("00000" & val(i));
		end loop;

		return std_ulogic_vector(resize(ret, val'length));
	end;

	function popcnt64(val: std_ulogic_vector(63 downto 0)) return std_ulogic_vector is
		variable ret: unsigned(6 downto 0) := (others => '0');
	begin
		for i in val'range loop
			ret := ret + ("000000" & val(i));
		end loop;

		return std_ulogic_vector(resize(ret, val'length));
	end;

	function cmp_one_byte(a, b: std_ulogic_vector(7 downto 0)) return std_ulogic_vector is
		variable ret: std_ulogic_vector(7 downto 0);
	begin
		if a = b then
			ret := x"ff";
		else
			ret := x"00";
		end if;

		return ret;
	end;

	function ppc_signed_compare(a, b: signed(63 downto 0)) return std_ulogic_vector is
		variable ret: std_ulogic_vector(3 downto 0);
	begin
		if a < b then
			ret := "1000";
		elsif a > b then
			ret := "0100";
		else
			ret := "0010";
		end if;

		return ret;
	end;

	function ppc_unsigned_compare(a, b: unsigned(63 downto 0)) return std_ulogic_vector is
		variable ret: std_ulogic_vector(3 downto 0);
	begin
		if a < b then
			ret := "1000";
		elsif a > b then
			ret := "0100";
		else
			ret := "0010";
		end if;

		return ret;
	end;

	function ra_or_zero(ra: std_ulogic_vector(63 downto 0); reg: std_ulogic_vector(4 downto 0)) return std_ulogic_vector is
	begin
		if to_integer(unsigned(reg)) = 0 then
			return x"0000000000000000";
		else
			return ra;
		end if;
	end;

	function byte_reverse(val: std_ulogic_vector(63 downto 0); size: integer) return std_ulogic_vector is
		variable ret : std_ulogic_vector(63 downto 0) := (others => '0');
	begin
		-- Vivado doesn't support non constant vector slices, so we have to code
		-- each of these.
		case_0: case size is
		when 2 =>
			for_2 : for k in 0 to 1 loop
			    ret(((8*k)+7) downto (8*k)) := val((8*(1-k)+7) downto (8*(1-k)));
		    end loop;
		when 4 =>
			for_4 : for k in 0 to 3 loop
			    ret(((8*k)+7) downto (8*k)) := val((8*(3-k)+7) downto (8*(3-k)));
		    end loop;
		when 8 =>
			for_8 : for k in 0 to 7 loop
			    ret(((8*k)+7) downto (8*k)) := val((8*(7-k)+7) downto (8*(7-k)));
		    end loop;
		when others =>
				report "bad byte reverse length " & integer'image(size) severity failure;
		end case;

		return ret;
	end;

	function sign_extend(val: std_ulogic_vector(63 downto 0); size: natural) return std_ulogic_vector is
		variable ret : signed(63 downto 0) := (others => '0');
		variable upper : integer := 0;
	begin
		case_0: case size is
			when 2 =>
				upper := 15;
			when 4 =>
				upper := 31;
			when 8 =>
				upper := 63;
			when others =>
				report "bad byte reverse length " & integer'image(size) severity failure;
		end case;

		ret := resize(signed(val(upper downto 0)), 64);
		return std_ulogic_vector(ret);
	end;
end package body helpers;