diff --git a/clang/lib/CodeGen/CodeGenPGO.cpp b/clang/lib/CodeGen/CodeGenPGO.cpp
--- a/clang/lib/CodeGen/CodeGenPGO.cpp
+++ b/clang/lib/CodeGen/CodeGenPGO.cpp
@@ -747,8 +747,11 @@
     return Working;
 
   // Check for remaining work in Working.
-  if (Working)
-    MD5.update(Working);
+  if (Working) {
+    using namespace llvm::support;
+    uint64_t Swapped = endian::byte_swap<uint64_t, little>(Working);
+    MD5.update(llvm::makeArrayRef((uint8_t *)&Swapped, sizeof(Swapped)));
+  }
 
   // Finalize the MD5 and return the hash.
   llvm::MD5::MD5Result Result;
diff --git a/clang/test/Profile/c-collision.c b/clang/test/Profile/c-collision.c
new file mode 100644
--- /dev/null
+++ b/clang/test/Profile/c-collision.c
@@ -0,0 +1,26 @@
+// Test that a slight change in the code leads to a different hash.
+// RUN: %clang_cc1 -UEXTRA -triple x86_64-unknown-linux-gnu -main-file-name c-collision.c %s -o - -emit-llvm -fprofile-instrument=llvm | FileCheck %s --check-prefix=CHECK-NOEXTRA
+// RUN: %clang_cc1 -DEXTRA -triple x86_64-unknown-linux-gnu -main-file-name c-collision.c %s -o - -emit-llvm -fprofile-instrument=llvm | FileCheck %s --check-prefix=CHECK-EXTRA
+
+// CHECK-NOEXTRA: @__profd_main = private global { {{.*}} } { i64 -2624081020897602054, i64 88870893692,
+// CHECK-EXTRA:   @__profd_main = private global { {{.*}} } { i64 -2624081020897602054, i64 101970072141,
+
+int main(int n, char **v) {
+  if (n)
+    n += 1;
+  if (n)
+    n += 1;
+  if (n)
+    n += 1;
+  if (n)
+    n += 1;
+  if (n)
+    n += 1;
+  if (n)
+    n += 1;
+#ifdef EXTRA
+  if (n)
+    n += 1;
+#endif
+  return n;
+}