Avoid -Wuninitialized false negatives with sanitization and VLAs.

Resolves:
PR tree-optimization/93100 - gcc -fsanitize=address inhibits -Wuninitialized
PR middle-end/98583 - missing -Wuninitialized reading from a second VLA in its own block

gcc/ChangeLog:

	PR tree-optimization/93100
	PR middle-end/98583
	* tree-ssa-uninit.c (check_defs): Exclude intrinsic functions that
	don't modify referenced objects.

gcc/testsuite/ChangeLog:

	PR tree-optimization/93100
	PR middle-end/98583
	* g++.dg/warn/uninit-pr93100.C: New test.
	* gcc.dg/uninit-pr93100.c: New test.
	* gcc.dg/uninit-pr98583.c: New test.

3 files changed, 164 insertions, 0 deletions

diff --git a/gcc/testsuite/g++.dg/warn/uninit-pr93100.C b/gcc/testsuite/g++.dg/warn/uninit-pr93100.C
new file mode 100644
index 0000000..c9cd3ef
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/uninit-pr93100.C
@@ -0,0 +1,59 @@
+/* PR tree-optimization/98508 - Sanitizer disable -Wall and -Wextra
+   { dg-do compile }
+   { dg-options "-O0 -Wall -fsanitize=address" } */
+
+struct S
+{
+  int a;
+};
+
+void warn_init_self_O0 ()
+{
+  S s = S (s);      // { dg-warning "\\\[-Wuninitialized" }
+  (void)&s;
+}
+
+
+void warn_init_self_use_O0 ()
+{
+  S s = S (s);      // { dg-warning "\\\[-Wuninitialized" }
+
+  void sink (void*);
+  sink (&s);
+}
+
+
+#pragma GCC optimize ("1")
+
+void warn_init_self_O1 ()
+{
+  S s = S (s);      // { dg-warning "\\\[-Wuninitialized" }
+  (void)&s;
+}
+
+
+void warn_init_self_use_O1 ()
+{
+  S s = S (s);      // { dg-warning "\\\[-Wuninitialized" }
+
+  void sink (void*);
+  sink (&s);
+}
+
+
+#pragma GCC optimize ("2")
+
+void warn_init_self_O2 ()
+{
+  S s = S (s);      // { dg-warning "\\\[-Wuninitialized" }
+  (void)&s;
+}
+
+
+void warn_init_self_use_O2 ()
+{
+  S s = S (s);      // { dg-warning "\\\[-Wuninitialized" }
+
+  void sink (void*);
+  sink (&s);
+}
diff --git a/gcc/testsuite/gcc.dg/uninit-pr93100.c b/gcc/testsuite/gcc.dg/uninit-pr93100.c
new file mode 100644
index 0000000..61b7e43
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/uninit-pr93100.c
@@ -0,0 +1,74 @@
+/* PR tree-optimization/93100 - gcc -fsanitize=address inhibits -Wuninitialized
+   { dg-do compile }
+   { dg-options "-Wall -fsanitize=address" } */
+
+struct A
+{
+  _Bool b;
+  int i;
+};
+
+void warn_A_b_O0 (void)
+{
+  struct A a;
+
+  if (a.b)          // { dg-warning "\\\[-Wuninitialized" }
+    {
+      (void)&a;
+    }
+}
+
+void warn_A_i_O0 (void)
+{
+  struct A a;
+
+  if (a.i)          // { dg-warning "\\\[-Wuninitialized" }
+    {
+      (void)&a;
+    }
+}
+
+#pragma GCC optimize ("1")
+
+void warn_A_b_O1 (void)
+{
+  struct A a;
+
+  if (a.b)          // { dg-warning "\\\[-Wuninitialized" }
+    {
+      (void)&a;
+    }
+}
+
+void warn_A_i_O1 (void)
+{
+  struct A a;
+
+  if (a.i)          // { dg-warning "\\\[-Wuninitialized" }
+    {
+      (void)&a;
+    }
+}
+
+
+#pragma GCC optimize ("2")
+
+void warn_A_b_O2 (void)
+{
+  struct A a;
+
+  if (a.b)          // { dg-warning "\\\[-Wuninitialized" }
+    {
+      (void)&a;
+    }
+}
+
+void warn_A_i_O2 (void)
+{
+  struct A a;
+
+  if (a.i)          // { dg-warning "\\\[-Wuninitialized" }
+    {
+      (void)&a;
+    }
+}
diff --git a/gcc/testsuite/gcc.dg/uninit-pr98583.c b/gcc/testsuite/gcc.dg/uninit-pr98583.c
new file mode 100644
index 0000000..638b029
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/uninit-pr98583.c
@@ -0,0 +1,31 @@
+/* PR middle-end/98583 - missing -Wuninitialized reading from a second VLA
+   in its own block
+   { dg-do compile }
+   { dg-options "-O2 -Wall" } */
+
+void f (int*);
+void g (int);
+
+void h1 (int n)
+{
+  int a[n];
+  f (a);
+
+  int b[n];
+  g (b[1]);         // { dg-warning "\\\[-Wuninitialized" }
+}
+
+void h2 (int n, int i, int j)
+{
+  if (i)
+    {
+      int a[n];
+      f (a);
+    }
+
+  if (j)
+    {
+      int b[n];
+      g (b[1]);     // { dg-warning "\\\[-Wmaybe-uninitialized" }
+    }
+}