testsuite/synth: add a test for #1977

2 files changed, 56 insertions, 0 deletions

diff --git a/testsuite/synth/issue1977/testsuite.sh b/testsuite/synth/issue1977/testsuite.sh
new file mode 100755
index 000000000..665792ea1
--- /dev/null
+++ b/testsuite/synth/issue1977/testsuite.sh
@@ -0,0 +1,8 @@
+#! /bin/sh
+
+. ../../testenv.sh
+
+GHDL_STD_FLAGS=--std=08
+synth_only triangularcounter
+
+echo "Test successful"
diff --git a/testsuite/synth/issue1977/triangularcounter.vhdl b/testsuite/synth/issue1977/triangularcounter.vhdl
new file mode 100644
index 000000000..c1851de19
--- /dev/null
+++ b/testsuite/synth/issue1977/triangularcounter.vhdl
@@ -0,0 +1,48 @@
+library IEEE;
+context IEEE.IEEE_std_context;
+
+entity TriangularCounter is
+  generic (
+    g_Precision : natural := 11
+  );
+  port (
+    CLK     : in  std_logic;
+    RST     : in  std_logic;
+    EN      : in  std_logic;
+    REF     : out unsigned(g_Precision-1 downto 0);
+    TRIGGER : out std_logic
+  );
+end entity;
+
+architecture arch of TriangularCounter is
+
+  signal dir    : std_logic;
+  signal cnt    : unsigned(REF'range);
+  signal tg_max : std_logic;
+  signal tg_min : std_logic;
+
+begin
+
+    process(RST, CLK)
+    begin
+      if RST then
+        cnt <= (others=>'0');
+        dir <= '0';
+      elsif rising_edge(CLK) then
+        if EN then
+          cnt <= cnt-1 when dir else cnt+1;
+          if tg_min or tg_max then
+            dir <= not dir;
+          end if;
+        end if;
+      end if;
+    end process;
+
+    tg_max <= (not dir) and (cnt ?= to_unsigned(2**g_Precision-2, REF));
+    tg_min <= dir and (cnt ?= 1);
+
+    REF <= cnt;
+    TRIGGER <= tg_min;
+
+end architecture;
+