re PR tree-optimization/49771 (wrong code with -ftree-vectorize)

        PR tree-optimization/49771
        * tree-vect-loop-manip.c (vect_vfa_segment_size): In case of
        zero step, set segment length to the size of the data-ref's type.

From-SVN: r176434

gcc/ChangeLog

+2011-07-19  Ira Rosen  <ira.rosen@linaro.org>
+
+	PR tree-optimization/49771
+	* tree-vect-loop-manip.c (vect_vfa_segment_size): In case of
+	zero step, set segment length to the size of the data-ref's type.
+
 2011-07-18  Martin Jambor  <mjambor@suse.cz>
 
 	* ipa-prop.h: Include alloc-pool.h, all sorts of updates to general

gcc/testsuite/ChangeLog

+2011-07-19  Ira Rosen  <ira.rosen@linaro.org>
+
+	PR tree-optimization/49771
+	* gcc.dg/vect/pr49771.c: New test.
+
 2011-07-18  Martin Jambor  <mjambor@suse.cz>
 
 	* gcc.dg/ipa/ipa-1.c: Updated testcase dump scan.

gcc/testsuite/gcc.dg/vect/pr49771.c

+#include <stdlib.h>
+#include <stdarg.h>
+
+static int a[1000];
+
+int
+foo (void)
+{
+  int j;
+  int i;
+  for (i = 0; i < 1000; i++)
+    for (j = 0; j < 1000; j++)
+      a[j] = a[i] + 1;
+  return a[0];
+}
+
+int
+main (void)
+{
+  int res = foo ();
+  if (res != 1999)
+    abort ();
+  return 0;
+}
+
+/* { dg-final { cleanup-tree-dump "vect" } } */

gcc/tree-vect-loop-manip.c

@@ -2356,9 +2356,14 @@ static tree
 vect_vfa_segment_size (struct data_reference *dr, tree length_factor)
 {
   tree segment_length;
-  segment_length = size_binop (MULT_EXPR,
-			       fold_convert (sizetype, DR_STEP (dr)),
-			       fold_convert (sizetype, length_factor));
+
+  if (!compare_tree_int (DR_STEP (dr), 0))
+    segment_length = TYPE_SIZE_UNIT (TREE_TYPE (DR_REF (dr)));
+  else
+    segment_length = size_binop (MULT_EXPR,
+                                 fold_convert (sizetype, DR_STEP (dr)),
+                                 fold_convert (sizetype, length_factor));
+
   if (vect_supportable_dr_alignment (dr, false)
         == dr_explicit_realign_optimized)
     {