re PR tree-optimization/49038 (-ftree-vectorise introduces reads past end of array)

        PR tree-optimization/49038
        * tree-vect-loop-manip.c (vect_generate_tmps_on_preheader):
        Ensure at least one epilogue iteration if required by data
        accesses with gaps.
        * tree-vectorizer.h (struct _loop_vec_info): Add new field 
        to mark loops that require peeling for gaps.
        * tree-vect-loop.c (new_loop_vec_info): Initialize new field.
        (vect_get_known_peeling_cost): Take peeling for gaps into 
        account.
        (vect_transform_loop): Generate epilogue if required by data
        access with gaps.
        * tree-vect-data-refs.c (vect_analyze_group_access): Mark the
        loop as requiring an epilogue if there are gaps in the end of
        the strided group.

From-SVN: r174265

1 files changed, 23 insertions, 1 deletions

diff --git a/gcc/tree-vect-data-refs.c b/gcc/tree-vect-data-refs.c
index 8d3b253..ee05997 100644
--- a/gcc/tree-vect-data-refs.c
+++ b/gcc/tree-vect-data-refs.c
@@ -2043,7 +2043,7 @@ vect_analyze_group_access (struct data_reference *dr)
   loop_vec_info loop_vinfo = STMT_VINFO_LOOP_VINFO (stmt_info);
   bb_vec_info bb_vinfo = STMT_VINFO_BB_VINFO (stmt_info);
   HOST_WIDE_INT dr_step = TREE_INT_CST_LOW (step);
-  HOST_WIDE_INT stride;
+  HOST_WIDE_INT stride, last_accessed_element = 1;
   bool slp_impossible = false;
 
   /* For interleaving, STRIDE is STEP counted in elements, i.e., the size of the
@@ -2072,6 +2072,16 @@ vect_analyze_group_access (struct data_reference *dr)
 	      fprintf (vect_dump, " step ");
 	      print_generic_expr (vect_dump, step, TDF_SLIM);
 	    }
+
+	  if (loop_vinfo)
+	    {
+	      LOOP_VINFO_PEELING_FOR_GAPS (loop_vinfo) = true;
+
+	      if (vect_print_dump_info (REPORT_DETAILS))
+		fprintf (vect_dump, "Data access with gaps requires scalar "
+				    "epilogue loop");
+	    }
+
 	  return true;
 	}
 
@@ -2137,6 +2147,7 @@ vect_analyze_group_access (struct data_reference *dr)
               next = GROUP_NEXT_ELEMENT (vinfo_for_stmt (next));
               continue;
             }
+
           prev = next;
 
           /* Check that all the accesses have the same STEP.  */
@@ -2167,6 +2178,8 @@ vect_analyze_group_access (struct data_reference *dr)
               gaps += diff - 1;
 	    }
 
+	  last_accessed_element += diff;
+
           /* Store the gap from the previous member of the group. If there is no
              gap in the access, GROUP_GAP is always 1.  */
           GROUP_GAP (vinfo_for_stmt (next)) = diff;
@@ -2245,6 +2258,15 @@ vect_analyze_group_access (struct data_reference *dr)
             VEC_safe_push (gimple, heap, BB_VINFO_STRIDED_STORES (bb_vinfo),
                            stmt);
         }
+
+      /* There is a gap in the end of the group.  */
+      if (stride - last_accessed_element > 0 && loop_vinfo)
+	{
+	  LOOP_VINFO_PEELING_FOR_GAPS (loop_vinfo) = true;
+	  if (vect_print_dump_info (REPORT_DETAILS))
+	    fprintf (vect_dump, "Data access with gaps requires scalar "
+				"epilogue loop");
+	}
     }
 
   return true;