diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 8429b46d638a42d1c0a89c5b2a3e74c48979697e..5fca7dcde8ced11f8d79f873a45bdab6f6f2a8f8 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2017-05-31  Bin Cheng  <bin.cheng@arm.com>
+
+	* tree-data-ref.c (prune_runtime_alias_test_list): Relax minimal
+	segment length for dr_b and compute it in wide_int.
+
 2017-05-31  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/80906
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index e336489188c5e62ba4e4f8173571f380d9eaf3db..9fec6120618f4fecf908f98663772a3693a23128 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2017-05-31  Bin Cheng  <bin.cheng@arm.com>
+
+	* gcc.dg/vect/pr80815-3.c: New test.
+
 2017-05-31  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/80906
diff --git a/gcc/testsuite/gcc.dg/vect/pr80815-3.c b/gcc/testsuite/gcc.dg/vect/pr80815-3.c
new file mode 100644
index 0000000000000000000000000000000000000000..dae01fa7af712fe171294d05d21d9651b6dd2fca
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr80815-3.c
@@ -0,0 +1,45 @@
+/* { dg-require-effective-target vect_int } */
+
+#include "tree-vect.h"
+int arr[2048];
+int res[100] = { 2148, 2146, 2144, 2142, 2140, 2138, 2136, 2134, 2132, 2130,
+		 2128, 2126, 2124, 2122, 2120, 2118, 2116, 2114, 2112, 2110,
+		 2108, 2106, 2104, 2102, 2100, 2098, 2096, 2094, 2092, 2090,
+		 2088, 2086, 2084, 2082, 2080, 2078, 2076, 2074, 2072, 2070,
+		 2068, 2066, 2064, 2062, 2060, 2058, 2056, 2054, 3078, 2050};
+
+__attribute__ ((noinline)) int
+foo (int *a, int *b, int len)
+{
+  int i;
+  int *a1 = a;
+  int *a0 = a1 - 4;
+  for (i = 0; i < len; i++)
+    {
+      *b = *a0 + *a1;
+      b--;
+      a0++;
+      a1++;
+    }
+  return 0;
+}
+
+int main (void)
+{
+  int *a = &arr[1027];
+  int *b = &arr[1024];
+
+  int i;
+  for (i = 0; i < 2048; i++)
+    arr[i] = i;
+
+  foo (a, b, 50);
+
+  for (i = 975; i < 1025; i++)
+    if (arr[i] != res[i - 975])
+      abort ();
+
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump "improved number of alias checks from \[0-9\]* to 1" "vect" } } */
diff --git a/gcc/tree-data-ref.c b/gcc/tree-data-ref.c
index cfff7c2a45c00a5d24fd9f330452b7988a08d2b9..c4275e2ce20b9853d8fd6f0a032c2ce60afff3de 100644
--- a/gcc/tree-data-ref.c
+++ b/gcc/tree-data-ref.c
@@ -1361,14 +1361,10 @@ prune_runtime_alias_test_list (vec<dr_with_seg_len_pair_t> *alias_pairs,
 	  wide_int min_seg_len_b;
 	  tree new_seg_len;
 
-	  if (tree_fits_uhwi_p (dr_b1->seg_len))
-	    {
-	      min_seg_len_b = dr_b1->seg_len;
-	      if (tree_int_cst_sign_bit (dr_b1->seg_len))
-		min_seg_len_b = wi::neg (min_seg_len_b);
-	    }
+	  if (TREE_CODE (dr_b1->seg_len) == INTEGER_CST)
+	    min_seg_len_b = wi::abs (dr_b1->seg_len);
 	  else
-	    min_seg_len_b = wi::uhwi (factor, TYPE_PRECISION (sizetype));
+	    min_seg_len_b = wi::mul (factor, wi::abs (DR_STEP (dr_b1->dr)));
 
 	  /* Now we try to merge alias check dr_a1 & dr_b and dr_a2 & dr_b.