Patchwork Ignore uninit warnings if ssa_undefined_value_p is TREE_NO_WARNING (PR tree-optimization/57149)

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Submitter Jakub Jelinek
Date May 7, 2013, 10 a.m.
Message ID <20130507100030.GY28963@tucnak.redhat.com>
Download mbox | patch
Permalink /patch/242179/
State New
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Comments

Jakub Jelinek - May 7, 2013, 10 a.m.
Hi!

On the attached testcase we started to give false positive warnings
when critedge has been changed to only use SSA_NAME_VAR for PHI result
if all PHI arguments use that SSA_NAME_VAR.

The fn3 function (inlined) contains a retval variable which has
false positive uninit warning disabled through the int retval = retval;
trick, so we set TREE_NO_WARNING on the VAR_DECL.  Previously
the PHI result was also result_NN and the uninit pass doesn't warn
for vars that are used possibly uninitialized and that are TREE_NO_WARNING.
But since the changes, the PHI result is just an anonymous SSA_NAME and
later on merged with the err var, which isn't TREE_NO_WARNING, the
only thing that is TREE_NO_WARNING is the result_NN(D) used in one of the
PHIs.

The following patch fixes it by not considering TREE_NO_WARNING
SSA_NAME_VARs as undefined for the purposes of uninit pass (other passes
still IMHO want the previous ssa_undefined_value_p behavior, which is
why I haven't changed ssa_undefined_value_p directly).

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk/4.8?

2013-05-07  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/57149
	* tree-ssa-uninit.c (uninit_undefined_value_p): New inline.
	(can_skip_redundant_opnd, compute_uninit_opnds_pos,
	collect_phi_def_edges, execute_late_warn_uninitialized): Use
	uninit_undefined_value_p instead of ssa_undefined_value_p.

	* gcc.dg/pr57149.c: New test.


	Jakub

Patch

--- gcc/tree-ssa-uninit.c.jj	2013-04-26 15:14:19.000000000 +0200
+++ gcc/tree-ssa-uninit.c	2013-05-07 08:57:37.538444516 +0200
@@ -101,6 +101,19 @@  ssa_undefined_value_p (tree t)
               && pointer_set_contains (possibly_undefined_names, t)));
 }
 
+/* Like ssa_undefined_value_p, but don't return true if TREE_NO_WARNING
+   is set on SSA_NAME_VAR.  */
+
+static inline bool
+uninit_undefined_value_p (tree t)
+{
+  if (!ssa_undefined_value_p (t))
+    return false;
+  if (SSA_NAME_VAR (t) && TREE_NO_WARNING (SSA_NAME_VAR (t)))
+    return false;
+  return true;
+}
+
 /* Checks if the operand OPND of PHI is defined by 
    another phi with one operand defined by this PHI, 
    but the rest operands are all defined. If yes, 
@@ -124,7 +137,7 @@  can_skip_redundant_opnd (tree opnd, gimp
       tree op = gimple_phi_arg_def (op_def, i);
       if (TREE_CODE (op) != SSA_NAME)
         continue;
-      if (op != phi_def && ssa_undefined_value_p (op))
+      if (op != phi_def && uninit_undefined_value_p (op))
         return false;
     }
 
@@ -149,7 +162,7 @@  compute_uninit_opnds_pos (gimple phi)
     {
       tree op = gimple_phi_arg_def (phi, i);
       if (TREE_CODE (op) == SSA_NAME
-          && ssa_undefined_value_p (op)
+          && uninit_undefined_value_p (op)
           && !can_skip_redundant_opnd (op, phi))
 	{
 	  /* Ignore SSA_NAMEs on abnormal edges to setjmp
@@ -518,7 +531,7 @@  collect_phi_def_edges (gimple phi, basic
                                  gimple_bb (def), cd_root))
             collect_phi_def_edges (def, cd_root, edges,
                                    visited_phis);
-          else if (!ssa_undefined_value_p (opnd))
+          else if (!uninit_undefined_value_p (opnd))
             {
               if (dump_file && (dump_flags & TDF_DETAILS))
                 {
@@ -2002,7 +2015,7 @@  execute_late_warn_uninitialized (void)
           {
             tree op = gimple_phi_arg_def (phi, i);
             if (TREE_CODE (op) == SSA_NAME
-                && ssa_undefined_value_p (op))
+                && uninit_undefined_value_p (op))
               {
                 worklist.safe_push (phi);
 		pointer_set_insert (added_to_worklist, phi);
--- gcc/testsuite/gcc.dg/pr57149.c.jj	2013-05-07 09:00:02.253621530 +0200
+++ gcc/testsuite/gcc.dg/pr57149.c	2013-05-07 08:59:42.000000000 +0200
@@ -0,0 +1,50 @@ 
+/* PR tree-optimization/57149 */
+/* { dg-do compile } */
+/* { dg-options "-Os -Wuninitialized" } */
+
+struct A { struct A *a, *b; };
+struct D { struct A e; };
+struct E { unsigned char f; struct { struct A e; } g; };
+struct F { struct E i[32]; };
+
+extern int fn0 (void);
+extern int fn1 (struct E *, struct D *);
+
+static inline __attribute__ ((always_inline)) int
+fn2 (const struct A *x)
+{
+  return x->a == x;
+}
+
+static int
+fn3 (struct E *x)
+{
+  struct D *l, *m;
+  int retval = retval;
+  if (fn2 (&x->g.e))
+    return 0;
+  for (l = (struct D *) x->g.e.a, m = (struct D *) l->e.a;
+       &l->e != &x->g.e;
+       l = m, m = (struct D *) m->e.a)
+    retval = fn1 (x, l);
+  return retval;
+}
+
+void
+fn4 (struct F *x, unsigned k)
+{
+  unsigned i;
+  for (i = 0; i < k; i++)
+    {
+      struct E *y = &x->i[i];
+      int err = -22;
+      err = fn3 (y);
+      if (y->f == 0)
+	{
+	  if (err > 0)
+	    err = fn0 ();
+	  if (err < 0)	/* { dg-bogus "may be used uninitialized in this function" } */
+	    fn0 ();
+	}
+    }
+}