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Subject: [Bug tree-optimization/48172] [4.5/4.6/4.7 Regression] incorrect vectorization of loop in GCC 4.5.* with -O3
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48172

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
                 CC|                            |irar at gcc dot gnu.org
         AssignedTo|unassigned at gcc dot       |rguenth at gcc dot gnu.org
                   |gnu.org                     |

--- Comment #3 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-03-18 10:00:34 UTC ---
Versioning for alias only seems to consider the case that DR_STEP is the
same for all DRs, right?

Index: gcc/tree-vect-data-refs.c
===================================================================
--- gcc/tree-vect-data-refs.c   (revision 171097)
+++ gcc/tree-vect-data-refs.c   (working copy)
@@ -528,6 +528,14 @@ vect_mark_for_runtime_alias_test (ddr_p
       print_generic_expr (vect_dump, DR_REF (DDR_B (ddr)), TDF_SLIM);
     }

+  if (!operand_equal_p (DR_STEP (DDR_A (ddr)), DR_STEP (DDR_B (ddr)), 0))
+    {
+      if (vect_print_dump_info (REPORT_DR_DETAILS))
+       fprintf (vect_dump, "versioning not supported for accesses with "
+                "different step.");
+      return false;
+    }
+
   if (optimize_loop_nest_for_size_p (loop))
     {
       if (vect_print_dump_info (REPORT_DR_DETAILS))

fixes it for me.