re PR tree-optimization/84803 (ICE from ifcvt_memrefs_wont_trap with -O3)

2018-03-12  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/84803
	* tree-if-conv.c (ifcvt_memrefs_wont_trap): Don't do anything
	for refs DR analysis didn't process.

	* gcc.dg/torture/pr84803.c: New testcase.

From-SVN: r258446

gcc/ChangeLog

 2018-03-12  Richard Biener  <rguenther@suse.de>
 
+	PR tree-optimization/84803
+	* tree-if-conv.c (ifcvt_memrefs_wont_trap): Don't do anything
+	for refs DR analysis didn't process.
+
+2018-03-12  Richard Biener  <rguenther@suse.de>
+
 	PR tree-optimization/84777
 	* tree-ssa-loop-ch.c (should_duplicate_loop_header_p): For
 	force-vectorize loops ignore whether we are optimizing for size.

gcc/testsuite/ChangeLog

+2018-03-12  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/84803
+	* gcc.dg/torture/pr84803.c: New testcase.
+
 2018-03-12  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c++/84813

gcc/testsuite/gcc.dg/torture/pr84803.c

+/* { dg-do compile } */
+
+long a;
+long *b;
+void c ();
+void d ();
+void
+e (long f)
+{
+  if (a)
+    *b = f;
+}
+void
+g ()
+{
+  c (g, e);
+}
+void
+c (int f, int h ())
+{
+  d (f, h, "");
+}
+void
+d (int f, int h (), char *i, char *k)
+{
+  int j;
+  d (f, h, i + 1, k);
+  while (--j)
+    h (*i);
+}

gcc/tree-if-conv.c

@@ -864,6 +864,11 @@ base_object_writable (tree ref)
 static bool
 ifcvt_memrefs_wont_trap (gimple *stmt, vec<data_reference_p> drs)
 {
+  /* If DR didn't see a reference here we can't use it to tell
+     whether the ref traps or not.  */
+  if (gimple_uid (stmt) == 0)
+    return false;
+
   data_reference_p *master_dr, *base_master_dr;
   data_reference_p a = drs[gimple_uid (stmt) - 1];