diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 2c0554b..5faa5ca 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,14 @@
+2013-11-12  Cong Hou  <congh@google.com>
+
+ * tree-vectorizer.h (struct dr_with_seg_len): Remove the base
+ address field as it can be obtained from dr.  Rename the struct.
+ * tree-vect-data-refs.c (comp_dr_with_seg_len_pair): Consider
+ steps of data references during sort.
+ (vect_prune_runtime_alias_test_list): Adjust with the change to
+ struct dr_with_seg_len.
+ * tree-vect-loop-manip.c (vect_create_cond_for_alias_checks):
+ Adjust with the change to struct dr_with_seg_len.
+
 2013-11-12  Jeff Law  <law@redhat.com>

  * tree-ssa-threadedge.c (thread_around_empty_blocks): New
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 09c7f20..8075409 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2013-11-12  Cong Hou  <congh@google.com>
+
+ * gcc.dg/vect/vect-alias-check.c: Update.
+
 2013-11-12  Balaji V. Iyer  <balaji.v.iyer@intel.com>

  * gcc.dg/cilk-plus/cilk-plus.exp: Added a check for LTO before running
diff --git a/gcc/testsuite/gcc.dg/vect/vect-alias-check.c
b/gcc/testsuite/gcc.dg/vect/vect-alias-check.c
index 64a4e0c..c1bffed 100644
--- a/gcc/testsuite/gcc.dg/vect/vect-alias-check.c
+++ b/gcc/testsuite/gcc.dg/vect/vect-alias-check.c
@@ -1,17 +1,17 @@
 /* { dg-require-effective-target vect_int } */
 /* { dg-do compile } */
-/* { dg-options "-O2 -ftree-vectorize
--param=vect-max-version-for-alias-checks=2 -fdump-tree-vect-details"
} */
+/* { dg-additional-options "--param=vect-max-version-for-alias-checks=2" } */

-/* A test case showing three potential alias checks between
-   a[i] and b[i], b[i+7], b[i+14]. With alias checks merging
-   enabled, those tree checks can be merged into one, and the
-   loop will be vectorized with vect-max-version-for-alias-checks=2.  */
+/* A test case showing four potential alias checks between a[i] and b[0], b[1],
+   b[i+1] and b[i+2].  With alias check merging enabled, those four checks
+   can be merged into two, and the loop will be vectorized with
+   vect-max-version-for-alias-checks=2.  */

 void foo (int *a, int *b)
 {
   int i;
   for (i = 0; i < 1000; ++i)
-    a[i] = b[i] + b[i+7] + b[i+14];
+    a[i] = b[0] + b[1] + b[i+1] + b[i+2];
 }

 /* { dg-final { scan-tree-dump-times "vectorized 1 loops" 1 "vect" } } */
diff --git a/gcc/tree-vect-data-refs.c b/gcc/tree-vect-data-refs.c
index c479775..7f0920d 100644
--- a/gcc/tree-vect-data-refs.c
+++ b/gcc/tree-vect-data-refs.c
@@ -2620,7 +2620,7 @@ vect_analyze_data_ref_accesses (loop_vec_info
loop_vinfo, bb_vec_info bb_vinfo)
 }


-/* Operator == between two dr_addr_with_seg_len objects.
+/* Operator == between two dr_with_seg_len objects.

    This equality operator is used to make sure two data refs
    are the same one so that we will consider to combine the
@@ -2628,62 +2628,51 @@ vect_analyze_data_ref_accesses (loop_vec_info
loop_vinfo, bb_vec_info bb_vinfo)
    refs.  */

 static bool
-operator == (const dr_addr_with_seg_len& d1,
-     const dr_addr_with_seg_len& d2)
+operator == (const dr_with_seg_len& d1,
+     const dr_with_seg_len& d2)
 {
-  return operand_equal_p (d1.basic_addr, d2.basic_addr, 0)
- && compare_tree (d1.offset, d2.offset) == 0
- && compare_tree (d1.seg_len, d2.seg_len) == 0;
+  return operand_equal_p (DR_BASE_ADDRESS (d1.dr),
+  DR_BASE_ADDRESS (d2.dr), 0)
+   && compare_tree (d1.offset, d2.offset) == 0
+   && compare_tree (d1.seg_len, d2.seg_len) == 0;
 }

-/* Function comp_dr_addr_with_seg_len_pair.
+/* Function comp_dr_with_seg_len_pair.

-   Comparison function for sorting objects of dr_addr_with_seg_len_pair_t
+   Comparison function for sorting objects of dr_with_seg_len_pair_t
    so that we can combine aliasing checks in one scan.  */

 static int
-comp_dr_addr_with_seg_len_pair (const void *p1_, const void *p2_)
+comp_dr_with_seg_len_pair (const void *p1_, const void *p2_)
 {
-  const dr_addr_with_seg_len_pair_t* p1 =
-    (const dr_addr_with_seg_len_pair_t *) p1_;
-  const dr_addr_with_seg_len_pair_t* p2 =
-    (const dr_addr_with_seg_len_pair_t *) p2_;
-
-  const dr_addr_with_seg_len &p11 = p1->first,
-     &p12 = p1->second,
-     &p21 = p2->first,
-     &p22 = p2->second;
-
-  int comp_res = compare_tree (p11.basic_addr, p21.basic_addr);
-  if (comp_res != 0)
+  const dr_with_seg_len_pair_t* p1 = (const dr_with_seg_len_pair_t *) p1_;
+  const dr_with_seg_len_pair_t* p2 = (const dr_with_seg_len_pair_t *) p2_;
+
+  const dr_with_seg_len &p11 = p1->first,
+ &p12 = p1->second,
+ &p21 = p2->first,
+ &p22 = p2->second;
+
+  /* For DR pairs (a, b) and (c, d), we only consider to merge the alias checks
+     if a and c have the same basic address snd step, and b and d have the same
+     address and step.  Therefore, if any a&c or b&d don't have the
same address
+     and step, we don't care the order of those two pairs after sorting.  */
+  int comp_res;
+
+  if ((comp_res = compare_tree (DR_BASE_ADDRESS (p11.dr),
+ DR_BASE_ADDRESS (p21.dr))) != 0)
     return comp_res;
-
-  comp_res = compare_tree (p12.basic_addr, p22.basic_addr);
-  if (comp_res != 0)
+  if ((comp_res = compare_tree (DR_BASE_ADDRESS (p12.dr),
+ DR_BASE_ADDRESS (p22.dr))) != 0)
+    return comp_res;
+  if ((comp_res = compare_tree (DR_STEP (p11.dr), DR_STEP (p21.dr))) != 0)
+    return comp_res;
+  if ((comp_res = compare_tree (DR_STEP (p12.dr), DR_STEP (p22.dr))) != 0)
+    return comp_res;
+  if ((comp_res = compare_tree (p11.offset, p21.offset)) != 0)
+    return comp_res;
+  if ((comp_res = compare_tree (p12.offset, p22.offset)) != 0)
     return comp_res;
-
-  if (TREE_CODE (p11.offset) != INTEGER_CST
-      || TREE_CODE (p21.offset) != INTEGER_CST)
-    {
-      comp_res = compare_tree (p11.offset, p21.offset);
-      if (comp_res != 0)
- return comp_res;
-    }
-  else if (tree_int_cst_compare (p11.offset, p21.offset) < 0)
-    return -1;
-  else if (tree_int_cst_compare (p11.offset, p21.offset) > 0)
-    return 1;
-  if (TREE_CODE (p12.offset) != INTEGER_CST
-      || TREE_CODE (p22.offset) != INTEGER_CST)
-    {
-      comp_res = compare_tree (p12.offset, p22.offset);
-      if (comp_res != 0)
- return comp_res;
-    }
-  else if (tree_int_cst_compare (p12.offset, p22.offset) < 0)
-    return -1;
-  else if (tree_int_cst_compare (p12.offset, p22.offset) > 0)
-    return 1;

   return 0;
 }
@@ -2718,11 +2707,11 @@ vect_vfa_segment_size (struct data_reference
*dr, tree length_factor)
     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));
+ fold_convert (sizetype, DR_STEP (dr)),
+ fold_convert (sizetype, length_factor));

   if (vect_supportable_dr_alignment (dr, false)
-        == dr_explicit_realign_optimized)
+ == dr_explicit_realign_optimized)
     {
       tree vector_size = TYPE_SIZE_UNIT
   (STMT_VINFO_VECTYPE (vinfo_for_stmt (DR_STMT (dr))));
@@ -2744,7 +2733,7 @@ vect_prune_runtime_alias_test_list
(loop_vec_info loop_vinfo)
 {
   vec<ddr_p> may_alias_ddrs =
     LOOP_VINFO_MAY_ALIAS_DDRS (loop_vinfo);
-  vec<dr_addr_with_seg_len_pair_t>& comp_alias_ddrs =
+  vec<dr_with_seg_len_pair_t>& comp_alias_ddrs =
     LOOP_VINFO_COMP_ALIAS_DDRS (loop_vinfo);
   int vect_factor = LOOP_VINFO_VECT_FACTOR (loop_vinfo);
   tree scalar_loop_iters = LOOP_VINFO_NITERS (loop_vinfo);
@@ -2823,18 +2812,11 @@ vect_prune_runtime_alias_test_list
(loop_vec_info loop_vinfo)
       segment_length_a = vect_vfa_segment_size (dr_a, length_factor);
       segment_length_b = vect_vfa_segment_size (dr_b, length_factor);

-      dr_addr_with_seg_len_pair_t dr_with_seg_len_pair
-  (dr_addr_with_seg_len
-       (dr_a, DR_BASE_ADDRESS (dr_a),
- size_binop (PLUS_EXPR, DR_OFFSET (dr_a), DR_INIT (dr_a)),
- segment_length_a),
-   dr_addr_with_seg_len
-       (dr_b, DR_BASE_ADDRESS (dr_b),
- size_binop (PLUS_EXPR, DR_OFFSET (dr_b), DR_INIT (dr_b)),
- segment_length_b));
-
-      if (compare_tree (dr_with_seg_len_pair.first.basic_addr,
- dr_with_seg_len_pair.second.basic_addr) > 0)
+      dr_with_seg_len_pair_t dr_with_seg_len_pair
+  (dr_with_seg_len (dr_a, segment_length_a),
+   dr_with_seg_len (dr_b, segment_length_b));
+
+      if (compare_tree (DR_BASE_ADDRESS (dr_a), DR_BASE_ADDRESS (dr_b)) > 0)
  swap (dr_with_seg_len_pair.first, dr_with_seg_len_pair.second);

       comp_alias_ddrs.safe_push (dr_with_seg_len_pair);
@@ -2842,17 +2824,17 @@ vect_prune_runtime_alias_test_list
(loop_vec_info loop_vinfo)

   /* Second, we sort the collected data ref pairs so that we can scan
      them once to combine all possible aliasing checks.  */
-  comp_alias_ddrs.qsort (comp_dr_addr_with_seg_len_pair);
+  comp_alias_ddrs.qsort (comp_dr_with_seg_len_pair);

   /* Third, we scan the sorted dr pairs and check if we can combine
      alias checks of two neighbouring dr pairs.  */
   for (size_t i = 1; i < comp_alias_ddrs.length (); ++i)
     {
       /* Deal with two ddrs (dr_a1, dr_b1) and (dr_a2, dr_b2).  */
-      dr_addr_with_seg_len *dr_a1 = &comp_alias_ddrs[i-1].first,
-   *dr_b1 = &comp_alias_ddrs[i-1].second,
-   *dr_a2 = &comp_alias_ddrs[i].first,
-   *dr_b2 = &comp_alias_ddrs[i].second;
+      dr_with_seg_len *dr_a1 = &comp_alias_ddrs[i-1].first,
+      *dr_b1 = &comp_alias_ddrs[i-1].second,
+      *dr_a2 = &comp_alias_ddrs[i].first,
+      *dr_b2 = &comp_alias_ddrs[i].second;

       /* Remove duplicate data ref pairs.  */
       if (*dr_a1 == *dr_a2 && *dr_b1 == *dr_b2)
@@ -2889,7 +2871,9 @@ vect_prune_runtime_alias_test_list
(loop_vec_info loop_vinfo)
       swap (dr_a2, dr_b2);
     }

-  if (!operand_equal_p (dr_a1->basic_addr, dr_a2->basic_addr, 0)
+  if (!operand_equal_p (DR_BASE_ADDRESS (dr_a1->dr),
+ DR_BASE_ADDRESS (dr_a2->dr),
+ 0)
       || !host_integerp (dr_a1->offset, 0)
       || !host_integerp (dr_a2->offset, 0))
     continue;
@@ -2916,8 +2900,8 @@ vect_prune_runtime_alias_test_list
(loop_vec_info loop_vinfo)

   HOST_WIDE_INT
   min_seg_len_b = (TREE_CODE (dr_b1->seg_len) == INTEGER_CST) ?
-      TREE_INT_CST_LOW (dr_b1->seg_len) :
-      vect_factor;
+     TREE_INT_CST_LOW (dr_b1->seg_len) :
+     vect_factor;

   if (diff <= min_seg_len_b
       || (TREE_CODE (dr_a1->seg_len) == INTEGER_CST
diff --git a/gcc/tree-vect-loop-manip.c b/gcc/tree-vect-loop-manip.c
index 15227856..b8e56c4 100644
--- a/gcc/tree-vect-loop-manip.c
+++ b/gcc/tree-vect-loop-manip.c
@@ -2242,7 +2242,7 @@ vect_create_cond_for_align_checks (loop_vec_info
loop_vinfo,
 void
 vect_create_cond_for_alias_checks (loop_vec_info loop_vinfo, tree * cond_expr)
 {
-  vec<dr_addr_with_seg_len_pair_t> comp_alias_ddrs =
+  vec<dr_with_seg_len_pair_t> comp_alias_ddrs =
     LOOP_VINFO_COMP_ALIAS_DDRS (loop_vinfo);
   tree part_cond_expr;

@@ -2260,15 +2260,15 @@ vect_create_cond_for_alias_checks
(loop_vec_info loop_vinfo, tree * cond_expr)

   for (size_t i = 0, s = comp_alias_ddrs.length (); i < s; ++i)
     {
-      const dr_addr_with_seg_len& dr_a = comp_alias_ddrs[i].first;
-      const dr_addr_with_seg_len& dr_b = comp_alias_ddrs[i].second;
+      const dr_with_seg_len& dr_a = comp_alias_ddrs[i].first;
+      const dr_with_seg_len& dr_b = comp_alias_ddrs[i].second;
       tree segment_length_a = dr_a.seg_len;
       tree segment_length_b = dr_b.seg_len;

       tree addr_base_a
- = fold_build_pointer_plus (dr_a.basic_addr, dr_a.offset);
+ = fold_build_pointer_plus (DR_BASE_ADDRESS (dr_a.dr), dr_a.offset);
       tree addr_base_b
- = fold_build_pointer_plus (dr_b.basic_addr, dr_b.offset);
+ = fold_build_pointer_plus (DR_BASE_ADDRESS (dr_b.dr), dr_b.offset);

       if (dump_enabled_p ())
  {
diff --git a/gcc/tree-vectorizer.h b/gcc/tree-vectorizer.h
index bbd50e1..0ce78d9 100644
--- a/gcc/tree-vectorizer.h
+++ b/gcc/tree-vectorizer.h
@@ -176,32 +176,33 @@ typedef struct _slp_oprnd_info


 /* This struct is used to store the information of a data reference,
-   including the data ref itself, its basic address, the access offset
-   and the segment length for aliasing checks.  This is used to generate
-   alias checks.  */
+   including the data ref itself, the access offset (calculated by summing its
+   offset and init) and the segment length for aliasing checks.
+   This is used to merge alias checks.  */

-struct dr_addr_with_seg_len
+struct dr_with_seg_len
 {
-  dr_addr_with_seg_len (data_reference* d, tree addr, tree off, tree len)
-    : dr (d), basic_addr (addr), offset (off), seg_len (len) {}
+  dr_with_seg_len (data_reference_p d, tree len)
+    : dr (d),
+      offset (size_binop (PLUS_EXPR, DR_OFFSET (d), DR_INIT (d))),
+      seg_len (len) {}

-  data_reference *dr;
-  tree basic_addr;
+  data_reference_p dr;
   tree offset;
   tree seg_len;
 };

-/* This struct contains two dr_addr_with_seg_len objects with aliasing data
+/* This struct contains two dr_with_seg_len objects with aliasing data
    refs.  Two comparisons are generated from them.  */

-struct dr_addr_with_seg_len_pair_t
+struct dr_with_seg_len_pair_t
 {
-  dr_addr_with_seg_len_pair_t (const dr_addr_with_seg_len& d1,
-       const dr_addr_with_seg_len& d2)
+  dr_with_seg_len_pair_t (const dr_with_seg_len& d1,
+       const dr_with_seg_len& d2)
     : first (d1), second (d2) {}

-  dr_addr_with_seg_len first;
-  dr_addr_with_seg_len second;
+  dr_with_seg_len first;
+  dr_with_seg_len second;
 };


@@ -306,7 +307,7 @@ typedef struct _loop_vec_info {

   /* Data Dependence Relations defining address ranges together with segment
      lengths from which the run-time aliasing check is built.  */
-  vec<dr_addr_with_seg_len_pair_t> comp_alias_ddrs;
+  vec<dr_with_seg_len_pair_t> comp_alias_ddrs;

   /* Statements in the loop that have data references that are candidates for a
      runtime (loop versioning) misalignment check.  */
