Merge pull request #99 from paulusmack/logical

Logical

Makefile

@@ -3,7 +3,7 @@ GHDLFLAGS=--std=08 -Psim-unisim
 CFLAGS=-O2 -Wall
 
 all = core_tb simple_ram_behavioural_tb soc_reset_tb icache_tb multiply_tb dmi_dtm_tb divider_tb \
-	rotator_tb
+	rotator_tb countzero_tb
 
 # XXX
 # loadstore_tb fetch_tb
@@ -19,6 +19,7 @@ core_tb.o: common.o wishbone_types.o core.o soc.o sim_jtag.o
 core.o: common.o wishbone_types.o fetch1.o fetch2.o icache.o decode1.o decode2.o register_file.o cr_file.o execute1.o execute2.o loadstore1.o loadstore2.o multiply.o writeback.o core_debug.o divider.o
 core_debug.o: common.o
 countzero.o:
+countzero_tb.o: common.o glibc_random.o countzero.o
 cr_file.o: common.o
 crhelpers.o: common.o
 decode1.o: common.o decode_types.o
@@ -95,6 +96,9 @@ divider_tb: divider_tb.o
 rotator_tb: rotator_tb.o
 	$(GHDL) -e $(GHDLFLAGS) $@
 
+countzero_tb: countzero_tb.o
+	$(GHDL) -e $(GHDLFLAGS) $@
+
 simple_ram_tb: simple_ram_tb.o
 	$(GHDL) -e $(GHDLFLAGS) $@
 

countzero.vhdl

@@ -14,98 +14,101 @@ entity zero_counter is
 end entity zero_counter;
 
 architecture behaviour of zero_counter is
-begin
-    zerocounter0: process(all)
-        variable l32, r32 : std_ulogic;
-        variable v32      : std_ulogic_vector(31 downto 0);
-        variable v16      : std_ulogic_vector(15 downto 0);
-        variable v8       : std_ulogic_vector(7 downto 0);
-        variable v4       : std_ulogic_vector(3 downto 0);
-        variable sel      : std_ulogic_vector(5 downto 0);
-    begin
-        l32 := '0';
-        r32 := '0';
-        v32 := (others => '0');
-        v16 := (others => '0');
-        v8  := (others => '0');
-        v4  := (others => '0');
-        sel := (others => '0');
+    signal y, z     : std_ulogic_vector(3 downto 0);
+    signal v16      : std_ulogic_vector(15 downto 0);
+    signal v4       : std_ulogic_vector(3 downto 0);
+    signal sel      : std_ulogic_vector(5 downto 0);
 
-	l32 := or (rs(63 downto 32));
-	r32 := or (rs(31 downto 0));
-	if (l32 = '0' or is_32bit = '1') and r32 = '0' then
-	    -- operand is zero, return 32 for 32-bit, else 64
-	    result <= x"00000000000000" & '0' & not is_32bit & is_32bit & "00000";
-	else
-
-	    if count_right = '0' then
-		sel(5) := l32 and (not is_32bit);
+    -- Return the index of the leftmost or rightmost 1 in a set of 4 bits.
+    -- Assumes v is not "0000"; if it is, return (right ? "11" : "00").
+    function encoder(v: std_ulogic_vector(3 downto 0); right: std_ulogic) return std_ulogic_vector is
+    begin
+	if right = '0' then
+	    if v(3) = '1' then
+		return "11";
+	    elsif v(2) = '1' then
+		return "10";
+	    elsif v(1) = '1' then
+		return "01";
 	    else
-		sel(5) := (not r32) and (not is_32bit);
+		return "00";
 	    end if;
-	    if sel(5) = '1' then
-		v32 := rs(63 downto 32);
 	else
-		v32 := rs(31 downto 0);
-	    end if;
-
-	    if count_right = '0' then
-		sel(4) := or (v32(31 downto 16));
+	    if v(0) = '1' then
+		return "00";
+	    elsif v(1) = '1' then
+		return "01";
+	    elsif v(2) = '1' then
+		return "10";
 	    else
-		sel(4) := not (or (v32(15 downto 0)));
+		return "11";
 	    end if;
-	    if sel(4) = '1' then
-		v16 := v32(31 downto 16);
-	    else
-		v16 := v32(15 downto 0);
 	end if;
+    end;
 
-	    if count_right = '0' then
-		sel(3) := or (v16(15 downto 8));
-	    else
-		sel(3) := not (or (v16(7 downto 0)));
-	    end if;
-	    if sel(3) = '1' then
-		v8 := v16(15 downto 8);
+begin
+    zerocounter0: process(all)
+    begin
+	-- Test 4 groups of 16 bits each.
+	-- The top 2 groups are considered to be zero in 32-bit mode.
+	z(0) <= or (rs(15 downto 0));
+	z(1) <= or (rs(31 downto 16));
+	z(2) <= or (rs(47 downto 32));
+	z(3) <= or (rs(63 downto 48));
+        if is_32bit = '0' then
+            sel(5 downto 4) <= encoder(z, count_right);
         else
-		v8 := v16(7 downto 0);
-	    end if;
-
+            sel(5) <= '0';
             if count_right = '0' then
-		sel(2) := or (v8(7 downto 4));
+                sel(4) <= z(1);
             else
-		sel(2) := not (or (v8(3 downto 0)));
+                sel(4) <= not z(0);
             end if;
-	    if sel(2) = '1' then
-		v4 := v8(7 downto 4);
-	    else
-		v4 := v8(3 downto 0);
         end if;
 
-	    if count_right = '0' then
-		if v4(3) = '1' then
-		    sel(1 downto 0) := "11";
-		elsif v4(2) = '1' then
-		    sel(1 downto 0) := "10";
-		elsif v4(1) = '1' then
-		    sel(1 downto 0) := "01";
-		else
-		    sel(1 downto 0) := "00";
-		end if;
+	-- Select the leftmost/rightmost non-zero group of 16 bits
+	case sel(5 downto 4) is
+	    when "00" =>
+		v16 <= rs(15 downto 0);
+	    when "01" =>
+		v16 <= rs(31 downto 16);
+	    when "10" =>
+		v16 <= rs(47 downto 32);
+	    when others =>
+		v16 <= rs(63 downto 48);
+	end case;
+
+	-- Test 4 groups of 4 bits
+	y(0) <= or (v16(3 downto 0));
+	y(1) <= or (v16(7 downto 4));
+	y(2) <= or (v16(11 downto 8));
+	y(3) <= or (v16(15 downto 12));
+	sel(3 downto 2) <= encoder(y, count_right);
+
+	-- Select the leftmost/rightmost non-zero group of 4 bits
+	case sel(3 downto 2) is
+	    when "00" =>
+		v4 <= v16(3 downto 0);
+	    when "01" =>
+		v4 <= v16(7 downto 4);
+	    when "10" =>
+		v4 <= v16(11 downto 8);
+	    when others =>
+		v4 <= v16(15 downto 12);
+	end case;
+
+	sel(1 downto 0) <= encoder(v4, count_right);
+
+	-- sel is now the index of the leftmost/rightmost 1 bit in rs
+	if v4 = "0000" then
+	    -- operand is zero, return 32 for 32-bit, else 64
+	    result <= x"00000000000000" & '0' & not is_32bit & is_32bit & "00000";
+	elsif count_right = '0' then
+	    -- return (63 - sel), trimmed to 5 bits in 32-bit mode
 	    result <= x"00000000000000" & "00" & (not sel(5) and not is_32bit) & not sel(4 downto 0);
 	else
-		if v4(0) = '1' then
-		    sel(1 downto 0) := "00";
-		elsif v4(1) = '1' then
-		    sel(1 downto 0) := "01";
-		elsif v4(2) = '1' then
-		    sel(1 downto 0) := "10";
-		else
-		    sel(1 downto 0) := "11";
-		end if;
 	    result <= x"00000000000000" & "00" & sel;
 	end if;
-	end if;
 
     end process;
 end behaviour;

countzero_tb.vhdl

@@ -0,0 +1,105 @@
+library ieee;
+use ieee.std_logic_1164.all;
+use ieee.numeric_std.all;
+
+library work;
+use work.common.all;
+use work.glibc_random.all;
+
+entity countzero_tb is
+end countzero_tb;
+
+architecture behave of countzero_tb is
+    constant clk_period: time := 10 ns;
+    signal rs: std_ulogic_vector(63 downto 0);
+    signal is_32bit, count_right: std_ulogic := '0';
+    signal result: std_ulogic_vector(63 downto 0);
+    signal randno: std_ulogic_vector(63 downto 0);
+
+begin
+    zerocounter_0: entity work.zero_counter
+	port map (
+	    rs => rs,
+	    result => result,
+	    count_right => count_right,
+	    is_32bit => is_32bit
+	);
+
+    stim_process: process
+        variable r: std_ulogic_vector(63 downto 0);
+    begin
+        -- test with input = 0
+        report "test zero input";
+        rs <= (others => '0');
+        is_32bit <= '0';
+        count_right <= '0';
+        wait for clk_period;
+        assert result = x"0000000000000040"
+            report "bad cntlzd 0 = " & to_hstring(result);
+        count_right <= '1';
+        wait for clk_period;
+        assert result = x"0000000000000040"
+            report "bad cnttzd 0 = " & to_hstring(result);
+        is_32bit <= '1';
+        count_right <= '0';
+        wait for clk_period;
+        assert result = x"0000000000000020"
+            report "bad cntlzw 0 = " & to_hstring(result);
+        count_right <= '1';
+        wait for clk_period;
+        assert result = x"0000000000000020"
+            report "bad cnttzw 0 = " & to_hstring(result);
+
+        report "test cntlzd/w";
+        count_right <= '0';
+        for j in 0 to 100 loop
+            r := pseudorand(64);
+            r(63) := '1';
+            for i in 0 to 63 loop
+                rs <= r;
+                is_32bit <= '0';
+                wait for clk_period;
+                assert to_integer(unsigned(result)) = i
+                    report "bad cntlzd " & to_hstring(rs) & " -> " & to_hstring(result);
+                rs <= r(31 downto 0) & r(63 downto 32);
+                is_32bit <= '1';
+                wait for clk_period;
+                if i < 32 then
+                    assert to_integer(unsigned(result)) = i
+                        report "bad cntlzw " & to_hstring(rs) & " -> " & to_hstring(result);
+                else
+                    assert to_integer(unsigned(result)) = 32
+                        report "bad cntlzw " & to_hstring(rs) & " -> " & to_hstring(result);
+                end if;
+                r := '0' & r(63 downto 1);
+            end loop;
+        end loop;
+
+        report "test cnttzd/w";
+        count_right <= '1';
+        for j in 0 to 100 loop
+            r := pseudorand(64);
+            r(0) := '1';
+            for i in 0 to 63 loop
+                rs <= r;
+                is_32bit <= '0';
+                wait for clk_period;
+                assert to_integer(unsigned(result)) = i
+                    report "bad cnttzd " & to_hstring(rs) & " -> " & to_hstring(result);
+                is_32bit <= '1';
+                wait for clk_period;
+                if i < 32 then
+                    assert to_integer(unsigned(result)) = i
+                        report "bad cnttzw " & to_hstring(rs) & " -> " & to_hstring(result);
+                else
+                    assert to_integer(unsigned(result)) = 32
+                        report "bad cnttzw " & to_hstring(rs) & " -> " & to_hstring(result);
+                end if;
+                r := r(62 downto 0) & '0';
+            end loop;
+        end loop;
+
+        assert false report "end of test" severity failure;
+        wait;
+    end process;
+end behave;