re PR tree-optimization/81500 (ICE with -O3 in process_use, at tree-vect-stmts.c:506)

2017-06-21  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/81500
	* tree-vect-loop.c (vect_is_simple_reduction): Properly fail if
	we didn't identify a reduction path.

	* gcc.dg/torture/pr81500.c: New testcase.

From-SVN: r250423

gcc/ChangeLog

+2017-06-21  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/81500
+	* tree-vect-loop.c (vect_is_simple_reduction): Properly fail if
+	we didn't identify a reduction path.
+
 2017-07-21  Tom de Vries  <tom@codesourcery.com>
 	    Cesar Philippidis  <cesar@codesourcery.com>
 

gcc/testsuite/ChangeLog

+2017-06-21  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/81500
+	* gcc.dg/torture/pr81500.c: New testcase.
+
 2017-07-20  Nathan Sidwell  <nathan@acm.org>
 
 	* g++.dg/ext/anon-struct6.C: Adjust diag.

gcc/testsuite/gcc.dg/torture/pr81500.c

+/* { dg-do compile } */
+
+typedef int a;
+void c(int *b)
+{
+  int d;
+  a e, f, *g, *h = b;
+  for (; d; d--) {
+      f = *g & 1;
+      *h-- = *g-- | e;
+      e = f;
+  }
+}

gcc/tree-vect-loop.c

@@ -3243,7 +3243,7 @@ pop:
     }
 
   /* Check whether the reduction path detected is valid.  */
-  bool fail = false;
+  bool fail = path.length () == 0;
   bool neg = false;
   for (unsigned i = 1; i < path.length (); ++i)
     {
@@ -3276,9 +3276,7 @@ pop:
 
   if (dump_enabled_p ())
     {
-      report_vect_op (MSG_MISSED_OPTIMIZATION,
-		      SSA_NAME_DEF_STMT
-		        (USE_FROM_PTR (path[path.length ()-1].second)),
+      report_vect_op (MSG_MISSED_OPTIMIZATION, def_stmt,
 		      "reduction: unknown pattern: ");
     }