[PR67828] don't unswitch on default defs of non-parms

for  gcc/ChangeLog

	PR rtl-optimizatoin/67828
	* tree-ssa-loop-unswitch.c: Include tree-ssa.h.
	(tree_may_unswitch_on): Don't unswitch on expressions
	involving undefined values.

for  gcc/testsuite/ChangeLog

	PR rtl-optimization/67828
	* gcc.dg/torture/pr67828.c: New.

From-SVN: r228650

gcc/ChangeLog

+2015-10-09  Alexandre Oliva <aoliva@redhat.com>
+
+	PR rtl-optimization/67828
+	* tree-ssa-loop-unswitch.c: Include tree-ssa.h.
+	(tree_may_unswitch_on): Don't unswitch on expressions
+	involving undefined values.
+
 2015-10-09  Richard Biener  <rguenther@suse.de>
 
 	* genmatch.c (print_operand): Fix formatting.

gcc/testsuite/ChangeLog

+2015-10-09  Alexandre Oliva <aoliva@redhat.com>
+
+	PR rtl-optimization/67828
+	* gcc.dg/torture/pr67828.c: New.
+
 2015-10-09  Ramana Radhakrishnan  <ramana.radhakrishnan@arm.com>
 
 	PR target/67366

gcc/testsuite/gcc.dg/torture/pr67828.c

+/* Check that we don't misoptimize the final value of d.  We used to
+   apply loop unswitching on if(j), introducing undefined behavior
+   that the original code wouldn't exercise, and this undefined
+   behavior would get later passes to misoptimize the loop.  */
+
+/* { dg-do run } */
+
+#include <stdio.h>
+#include <stdlib.h>
+
+int x;
+
+int __attribute__ ((noinline, noclone))
+xprintf (int d) {
+  if (d)
+    {
+      if (x)
+	printf ("%d", d);
+      abort ();
+    }
+}
+
+int a, b;
+short c;
+
+int
+main ()
+{
+  int j, d = 1;
+  for (; c >= 0; c++)
+    {
+      a = d;
+      d = 0;
+      if (b)
+	{
+	  xprintf (0);
+	  if (j)
+	    xprintf (0);
+	}
+    }
+  xprintf (d);
+  exit (0);
+}

gcc/tree-ssa-loop-unswitch.c

@@ -32,6 +32,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "internal-fn.h"
 #include "gimplify.h"
 #include "tree-cfg.h"
+#include "tree-ssa.h"
 #include "tree-ssa-loop-niter.h"
 #include "tree-ssa-loop.h"
 #include "tree-into-ssa.h"
@@ -139,6 +140,10 @@ tree_may_unswitch_on (basic_block bb, struct loop *loop)
   /* Condition must be invariant.  */
   FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_USE)
     {
+      /* Unswitching on undefined values would introduce undefined
+	 behavior that the original program might never exercise.  */
+      if (ssa_undefined_value_p (use, true))
+	return NULL_TREE;
       def = SSA_NAME_DEF_STMT (use);
       def_bb = gimple_bb (def);
       if (def_bb