Index: llvm/lib/Support/StringRef.cpp
===================================================================
--- llvm/lib/Support/StringRef.cpp
+++ llvm/lib/Support/StringRef.cpp
@@ -374,9 +374,14 @@
   size_t N = Str.size();
   if (N > Length)
     return 0;
-  for (size_t i = 0, e = Length - N + 1; i != e; ++i)
-    if (substr(i, N).equals(Str))
+  for (size_t i = 0, e = Length - N + 1; i < e;) {
+    if (substr(i, N).equals(Str)) {
       ++Count;
+      i += N;
+    }
+    else
+      ++i;
+  }
   return Count;
 }
 
Index: llvm/unittests/ADT/StringRefTest.cpp
===================================================================
--- llvm/unittests/ADT/StringRefTest.cpp
+++ llvm/unittests/ADT/StringRefTest.cpp
@@ -505,6 +505,13 @@
   EXPECT_EQ(1U, Str.count("hello"));
   EXPECT_EQ(1U, Str.count("ello"));
   EXPECT_EQ(0U, Str.count("zz"));
+
+  StringRef OverlappingAbba("abbabba");
+  EXPECT_EQ(1U, OverlappingAbba.count("abba"));
+  StringRef NonOverlappingAbba("abbaabba");
+  EXPECT_EQ(2U, NonOverlappingAbba.count("abba"));
+  StringRef ComplexAbba("abbabbaxyzabbaxyz");
+  EXPECT_EQ(2U, ComplexAbba.count("abba"));
 }
 
 TEST(StringRefTest, EditDistance) {