From 60dcb7772b2af623961a96f0bfde4cf3df2c2a1b Mon Sep 17 00:00:00 2001
From: Nick Gasson <nick@nickg.me.uk>
Date: Mon, 8 Jan 2024 21:29:46 +0000
Subject: [PATCH] Further restrictions on collapsing output ports. Issue #824

---
 src/lower.c               | 17 +++++++++++++++++
 test/regress/issue824.vhd | 37 +++++++++++++++++++++++++++++++++++++
 test/regress/testlist.txt |  1 +
 3 files changed, 55 insertions(+)
 create mode 100644 test/regress/issue824.vhd

diff --git a/src/lower.c b/src/lower.c
index 37399953..9ef03ac5 100644
--- a/src/lower.c
+++ b/src/lower.c
@@ -11794,6 +11794,23 @@ static void lower_direct_mapped_port(lower_unit_t *lu, driver_set_t *ds,
 
    if (type_is_unconstrained(port_type))
       return;   // Not supported for now
+   else if (tree_subkind(port) == PORT_OUT) {
+      tree_t ref = name_to_ref(value);
+      assert(ref != NULL);
+
+      tree_t signal = tree_ref(ref);
+
+      // Ensure that the default value of the port is the same as the
+      // signal it is connected to
+
+      tree_t def1 = tree_has_value(signal) ? tree_value(signal) : NULL;
+      tree_t def2 = tree_has_value(port) ? tree_value(port) : NULL;
+
+      if (def1 != NULL && def2 != NULL && !same_tree(def1, def2))
+         return;
+      else if ((def1 != NULL) ^ (def2 != NULL))
+         return;
+   }
 
    int hops = 0;
    vcode_var_t var = VCODE_INVALID_VAR;
diff --git a/test/regress/issue824.vhd b/test/regress/issue824.vhd
new file mode 100644
index 00000000..60425149
--- /dev/null
+++ b/test/regress/issue824.vhd
@@ -0,0 +1,37 @@
+entity issue824 is
+end entity;
+
+library ieee;
+use ieee.std_logic_1164.all;
+
+architecture test of issue824 is
+    type t_rec is record
+        x, y : std_logic;
+    end record;
+
+    procedure update (signal r : inout t_rec) is
+    begin
+        r.y <= '1';
+    end procedure;
+
+    signal s : t_rec := ('Z', 'Z');
+begin
+
+    p1: process is
+    begin
+        --s.x <= 'Z';
+        wait for 1 ns;
+        update(s);
+        wait for 1 ns;
+        assert s.x = 'Z';
+        wait;
+    end process;
+
+    b1: block is
+        port ( o : out t_rec );
+        port map ( s );
+    begin
+        o <= ('Z', 'Z');
+    end block;
+
+end architecture;
diff --git a/test/regress/testlist.txt b/test/regress/testlist.txt
index 5e0b8d8d..b48b9af1 100644
--- a/test/regress/testlist.txt
+++ b/test/regress/testlist.txt
@@ -917,3 +917,4 @@ issue816        fail,gold
 gentype7        normal,2019
 issue819        normal,2008
 issue820        normal
+issue824        normal
-- 
2.39.2