re PR tree-optimization/58228 (wrong code (with vectorization?) at -O3 on x86_64-linux-gnu)

2013-08-30  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/58228
	* tree-vect-data-refs.c (vect_analyze_data_ref_access): Do not
	allow invariant loads in nested loop vectorization.

	* gcc.dg/torture/pr58228.c: New testcase.

From-SVN: r202097

gcc/ChangeLog

 2013-08-30  Richard Biener  <rguenther@suse.de>
 
+	PR tree-optimization/58228
+	* tree-vect-data-refs.c (vect_analyze_data_ref_access): Do not
+	allow invariant loads in nested loop vectorization.
+
+2013-08-30  Richard Biener  <rguenther@suse.de>
+
 	PR tree-optimization/58223
 	* tree-loop-distribution.c (has_anti_dependence): Rename to ...
 	(has_anti_or_output_dependence): ... this and adjust to also

gcc/testsuite/ChangeLog

 2013-08-30  Richard Biener  <rguenther@suse.de>
 
+	PR tree-optimization/58228
+	* gcc.dg/torture/pr58228.c: New testcase.
+
+2013-08-30  Richard Biener  <rguenther@suse.de>
+
 	PR tree-optimization/58223
 	* gcc.dg/torture/pr58223.c: New testcase.
 	* gcc.dg/tree-ssa/ldist-16.c: Flip expected behavior.

gcc/testsuite/gcc.dg/torture/pr58228.c

+/* { dg-do run } */
+
+extern void abort (void);
+int a[8][8] = {{1}};
+int b, c, d, e;
+
+int main ()
+{
+  for (c = 0; c < 8; c++)
+    for (b = 0; b < 2; b++)
+      a[b + 4][c] = a[c][0];
+  if (a[4][4] != 1)
+    abort ();
+  return 0;
+}

gcc/tree-vect-data-refs.c

@@ -2271,10 +2271,17 @@ vect_analyze_data_ref_access (struct data_reference *dr)
       return false;
     }
 
-  /* Allow invariant loads in loops.  */
+  /* Allow invariant loads in not nested loops.  */
   if (loop_vinfo && integer_zerop (step))
     {
       GROUP_FIRST_ELEMENT (vinfo_for_stmt (stmt)) = NULL;
+      if (nested_in_vect_loop_p (loop, stmt))
+	{
+	  if (dump_enabled_p ())
+	    dump_printf_loc (MSG_NOTE, vect_location,
+			     "zero step in inner loop of nest");
+	  return false;
+	}
       return DR_IS_READ (dr);
     }