re PR tree-optimization/59651 (Vectorizer failing to spot dependence causes…

re PR tree-optimization/59651 (Vectorizer failing to spot dependence causes incorrect code generation.)

2014-01-03  Bingfeng Mei <bmei@broadcom.com>

	PR tree-optimization/59651
	* tree-vect-loop-manip.c (vect_create_cond_for_alias_checks): 
	Address	range for negative step should be added by TYPE_SIZE_UNIT.

	PR tree-optimization/59651
	* gcc.dg/torture/pr59651.c: New test.
	* gcc.dg/vect/pr59651.c: Ditto.

From-SVN: r206319

gcc/ChangeLog

+2014-01-03  Bingfeng Mei <bmei@broadcom.com>
+
+	PR tree-optimization/59651
+	* tree-vect-loop-manip.c (vect_create_cond_for_alias_checks): 
+	Address	range for negative step should be added by TYPE_SIZE_UNIT.
+
 2014-01-03  Andreas Schwab  <schwab@linux-m68k.org>
 
 	* config/m68k/m68k.c (handle_move_double): Handle pushes with

gcc/testsuite/ChangeLog

+2014-01-03  Bingfeng Mei  <bmei@broadcom.com>
+
+	PR tree-optimization/59651
+	* gcc.dg/torture/pr59651.c: New test.
+	* gcc.dg/vect/pr59651.c: Ditto.
+
 2014-01-03  Jakub Jelinek  <jakub@redhat.com>
 
 	PR target/59625

gcc/testsuite/gcc.dg/torture/pr59651.c

+/* PR tree-optimization/59561 */
+/* { dg-do run } */
+
+extern void abort (void);
+int a[] = { 0, 0, 0, 0, 0, 0, 0, 6 };
+
+int b;
+int
+main ()
+{
+  for (;;)
+    {
+      for (b = 7; b; --b)
+	a[b] = a[7] > 1;
+      break;
+    }
+  if (a[1] != 0)
+    abort ();
+  return 0;
+}

gcc/testsuite/gcc.dg/vect/pr59651.c

+/* PR tree-optimization/59561 */
+#include "../torture/pr59651.c"
+
+/* { dg-final { cleanup-tree-dump "vect" } } */

gcc/tree-vect-loop-manip.c

@@ -2240,13 +2240,24 @@ vect_create_cond_for_alias_checks (loop_vec_info loop_vinfo, tree * cond_expr)
 
       tree seg_a_min = addr_base_a;
       tree seg_a_max = fold_build_pointer_plus (addr_base_a, segment_length_a);
+      /* For negative step, we need to adjust address range by TYPE_SIZE_UNIT
+	 bytes, e.g., int a[3] -> a[1] range is [a+4, a+16) instead of
+	 [a, a+12) */
       if (tree_int_cst_compare (DR_STEP (dr_a.dr), size_zero_node) < 0)
-	seg_a_min = seg_a_max, seg_a_max = addr_base_a;
+	{
+	  tree unit_size = TYPE_SIZE_UNIT (TREE_TYPE (DR_REF (dr_a.dr)));
+	  seg_a_min = fold_build_pointer_plus (seg_a_max, unit_size);
+	  seg_a_max = fold_build_pointer_plus (addr_base_a, unit_size);
+	}
 
       tree seg_b_min = addr_base_b;
       tree seg_b_max = fold_build_pointer_plus (addr_base_b, segment_length_b);
       if (tree_int_cst_compare (DR_STEP (dr_b.dr), size_zero_node) < 0)
-	seg_b_min = seg_b_max, seg_b_max = addr_base_b;
+	{
+	  tree unit_size = TYPE_SIZE_UNIT (TREE_TYPE (DR_REF (dr_b.dr)));
+	  seg_b_min = fold_build_pointer_plus (seg_b_max, unit_size);
+	  seg_b_max = fold_build_pointer_plus (addr_base_b, unit_size);
+	}
 
       part_cond_expr =
       	fold_build2 (TRUTH_OR_EXPR, boolean_type_node,