From dedacffd78c0b4b04b51053f1eb7e901aa1ac6dc Mon Sep 17 00:00:00 2001
From: Nick Gasson <nick@nickg.me.uk>
Date: Tue, 2 Jan 2024 19:47:24 +0000
Subject: [PATCH] Fix crash simplifying if-statement. Issue #821

---
 src/simp.c             | 16 +++++++++-------
 test/simp/issue821.vhd | 21 +++++++++++++++++++++
 test/test_simp.c       | 20 ++++++++++++++++++++
 3 files changed, 50 insertions(+), 7 deletions(-)
 create mode 100644 test/simp/issue821.vhd

diff --git a/src/simp.c b/src/simp.c
index 590bce94..3eed61d7 100644
--- a/src/simp.c
+++ b/src/simp.c
@@ -942,20 +942,22 @@ static tree_t simp_if(tree_t t)
          simp_find_drivers(c, &drivers);
    }
 
-   if (drivers.count > 0 && tree_conds(new) > 0)
-      simp_make_dummy_drivers(tree_cond(new, 0), &drivers);
-   else if (drivers.count > 0) {
+   if (drivers.count > 0) {
        tree_t b = tree_new(T_SEQUENCE);
        tree_set_loc(b, tree_loc(t));
-       if (tree_has_ident(t))
-          tree_set_ident(b, tree_ident(t));
 
+       if (tree_conds(new) > 0)
+          tree_add_stmt(b, new);
+       else if (tree_has_ident(new))
+          tree_set_ident(b, tree_ident(new));
 
        simp_make_dummy_drivers(b, &drivers);
        return b;
    }
-
-   return tree_conds(new) > 0 ? new : NULL;
+   else if (tree_conds(new) > 0)
+      return new;
+   else
+      return NULL;
 }
 
 static tree_t simp_while(tree_t t)
diff --git a/test/simp/issue821.vhd b/test/simp/issue821.vhd
new file mode 100644
index 00000000..93e9ca8c
--- /dev/null
+++ b/test/simp/issue821.vhd
@@ -0,0 +1,21 @@
+entity issue821 is
+end entity;
+
+architecture test of issue821 is
+    signal x : integer;
+begin
+
+    g: for i in 1 to 2 generate
+    begin
+        p: process is
+        begin
+            if i > 1 then
+                x <= 1;
+            elsif x < 100 then
+                x <= 2;
+            end if;
+            wait;
+        end process;
+    end generate;
+
+end architecture;
diff --git a/test/test_simp.c b/test/test_simp.c
index 9df89eb9..1a2e48c0 100644
--- a/test/test_simp.c
+++ b/test/test_simp.c
@@ -1655,6 +1655,25 @@ START_TEST(test_issue812)
 }
 END_TEST
 
+START_TEST(test_issue821)
+{
+   input_from_file(TESTDIR "/simp/issue821.vhd");
+
+   tree_t top = run_elab();
+
+   tree_t g1 = tree_stmt(tree_stmt(top, 0), 0);
+   fail_unless(tree_kind(g1) == T_BLOCK);
+
+   tree_t seq = tree_stmt(tree_stmt(g1, 0), 0);
+   fail_unless(tree_kind(seq) == T_SEQUENCE);
+   fail_unless(tree_stmts(seq) == 2);
+   fail_unless(tree_kind(tree_stmt(seq, 0)) == T_IF);
+   fail_unless(tree_kind(tree_stmt(seq, 1)) == T_DUMMY_DRIVER);
+
+   fail_if_errors();
+}
+END_TEST
+
 Suite *get_simp_tests(void)
 {
    Suite *s = suite_create("simplify");
@@ -1720,6 +1739,7 @@ Suite *get_simp_tests(void)
    tcase_add_test(tc_core, test_issue782);
    tcase_add_test(tc_core, test_order2);
    tcase_add_test(tc_core, test_issue812);
+   tcase_add_test(tc_core, test_issue821);
    suite_add_tcase(s, tc_core);
 
    return s;
-- 
2.39.2