re PR bootstrap/77768 (LTO/PGO -O3 bootstrap broken: tree-vrp.c:11053:0:…

re PR bootstrap/77768 (LTO/PGO -O3 bootstrap broken: tree-vrp.c:11053:0: internal compiler error: Segmentation fault)

2016-09-29  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/77768
	* tree-ssa-pre.c (eliminate_dom_walker::before_dom_children):
	Handle stores to readonly memory when removing redundant stores.

	* gcc.dg/torture/pr77768.c: New testcase.

From-SVN: r240617

gcc/ChangeLog

 2016-09-29  Richard Biener  <rguenther@suse.de>
 
+	PR tree-optimization/77768
+	* tree-ssa-pre.c (eliminate_dom_walker::before_dom_children):
+	Handle stores to readonly memory when removing redundant stores.
+
+2016-09-29  Richard Biener  <rguenther@suse.de>
+
 	PR middle-end/77407
 	* match.pd: Add X / abs (X) -> X < 0 ? -1 : 1 and
 	X / -X -> -1 simplifications.

gcc/testsuite/ChangeLog

+2016-09-29  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/77768
+	* gcc.dg/torture/pr77768.c: New testcase.
+
 2016-09-28  Richard Biener  <rguenther@suse.de>
 
 	PR middle-end/77407

gcc/testsuite/gcc.dg/torture/pr77768.c

+/* { dg-do run } */
+
+static const int a;
+int b;
+int *c, *d;
+int main()
+{
+  c = (int *)&a;
+  c == d ?: __builtin_exit(0); 
+  for (; b; b++ >= (*d = a))
+    ;
+  return 0;
+}

gcc/tree-ssa-pre.c

@@ -4443,9 +4443,11 @@ eliminate_dom_walker::before_dom_children (basic_block b)
 	      && operand_equal_p (val, rhs, 0))
 	    {
 	      /* We can only remove the later store if the former aliases
-		 at least all accesses the later one does.  */
+		 at least all accesses the later one does or if the store
+		 was to readonly memory storing the same value.  */
 	      alias_set_type set = get_alias_set (lhs);
-	      if (vnresult->set == set
+	      if (! vnresult
+		  || vnresult->set == set
 		  || alias_set_subset_of (set, vnresult->set))
 		{
 		  if (dump_file && (dump_flags & TDF_DETAILS))