3 files changed, 85 insertions, 0 deletions
diff --git a/testsuite/synth/issue1645/ent.vhdl b/testsuite/synth/issue1645/ent.vhdl
new file mode 100644
index 000000000..05dfc5da4
--- /dev/null
+++ b/testsuite/synth/issue1645/ent.vhdl
@@ -0,0 +1,41 @@
+library ieee;
+use ieee.std_logic_1164.all;
+use ieee.numeric_std.all;
+
+entity ent is
+   generic (size : natural := 4);
+   port (
+      clk : in std_logic;
+      r   : out std_logic
+   );
+end entity ent;
+
+architecture rtl of ent is
+
+   type ram_type is array (0 to size-1) of std_logic_vector(7 downto 0);
+   subtype index_type is natural range ram_type'range;   -- This declaration leads to incorrect sign-extension
+--   subtype index_type is natural range 0 to size-1;      -- This declaration leads to correct unsigned comparison.
+   signal a : index_type := 0;
+
+begin
+
+   process (clk)
+   begin
+      if rising_edge(clk) then
+         if a = index_type'high then
+            a <= index_type'low;
+         else
+            a <= a + 1;
+         end if;
+      end if;
+   end process;
+
+   process (a)
+   begin
+      if a < 3 then
+         r <= '1';
+      else
+         r <= '0';
+      end if;
+   end process;
+end architecture rtl;
diff --git a/testsuite/synth/issue1645/tb_ent.vhdl b/testsuite/synth/issue1645/tb_ent.vhdl
new file mode 100644
index 000000000..bed9fcfc3
--- /dev/null
+++ b/testsuite/synth/issue1645/tb_ent.vhdl
@@ -0,0 +1,37 @@
+entity tb_ent is
+end tb_ent;
+
+library ieee;
+use ieee.std_logic_1164.all;
+
+architecture behav of tb_ent is
+  signal clk : std_logic;
+  signal r : std_logic;
+begin
+  dut: entity work.ent
+    port map (
+      clk => clk,
+      r => r);
+
+  process
+    procedure pulse is
+    begin
+      clk <= '0';
+      wait for 1 ns;
+      clk <= '1';
+      wait for 1 ns;
+    end pulse;
+  begin
+    wait for 1 ns;
+    assert r = '1' severity failure;
+    pulse;
+    assert r = '1' severity failure;
+    pulse;
+    assert r = '1' severity failure;
+    pulse;
+    assert r = '0' severity failure;
+    pulse;
+    assert r = '1' severity failure;
+    wait;
+  end process;
+end behav;
diff --git a/testsuite/synth/issue1645/testsuite.sh b/testsuite/synth/issue1645/testsuite.sh
new file mode 100755
index 000000000..5c1da263d
--- /dev/null
+++ b/testsuite/synth/issue1645/testsuite.sh
@@ -0,0 +1,7 @@
+#! /bin/sh
+
+. ../../testenv.sh
+
+synth_tb ent
+
+echo "Test successful"