The following adds a testcase that illustrates a defect in
compute_control_dep_chain and its attempt to identify loop
exits as special to continue walking post-dominators but failing
to do so for following post-dominators. On trunk there is now
simple_control_dep_chain saving the day, avoiding the false
positive but with GCC 12 we get a bogus diagnostic.
Pushed.
* gcc.dg/uninit-pred-11.c: New testcase.
---
gcc/testsuite/gcc.dg/uninit-pred-11.c | 27 +++++++++++++++++++++++++++
1 file changed, 27 insertions(+)
create mode 100644 gcc/testsuite/gcc.dg/uninit-pred-11.c
diff --git a/gcc/testsuite/gcc.dg/uninit-pred-11.c
b/gcc/testsuite/gcc.dg/uninit-pred-11.c
new file mode 100644
index 00000000000..734df379ef7
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/uninit-pred-11.c
@@ -0,0 +1,27 @@
+/* { dg-do compile } */
+/* { dg-options "-O -Wmaybe-uninitialized" } */
+
+extern unsigned bar (void);
+extern void quux (void);
+int z;
+unsigned foo (unsigned v, int y)
+{
+ unsigned u;
+ if (v != 1)
+ u = bar ();
+
+ // Prevent the "dom" pass from changing the CFG layout based on the inference
+ // 'if (v != 1) is false then (v != 2) is true'. (Now it would have to
+ // duplicate the loop in order to do so, which is deemed expensive.)
+ for (int i = 0; i < 10; i++)
+ quux ();
+
+ // This variation from uninit-25.c causes compute_control_dep_chain
+ // to run into a defect but simple_control_dep_chain saves us here
+ if (y)
+ z = 1;
+ if (v != 1)
+ return u; /* { dg-bogus "may be used uninitialized" } */
+
+ return 0;
+}
--
2.35.3
