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
@@ -747,13 +747,15 @@
     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;
   MD5.final(Result);
-  using namespace llvm::support;
   return Result.low();
 }
 
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 +1,22 @@
+// 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=clang | 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=clang | FileCheck %s --check-prefix=CHECK-EXTRA
+
+// CHECK-NOEXTRA: @__profd_foo = private global { {{.*}} } { i64 6699318081062747564, i64 7156072912471487002,
+// CHECK-EXTRA:   @__profd_foo = private global { {{.*}} } { i64 6699318081062747564, i64 -4383447408116050035,
+
+extern int bar;
+void foo() {
+  if (bar) {
+  }
+  if (bar) {
+  }
+  if (bar) {
+    if (bar) {
+#ifdef EXTRA
+      if (bar) {
+      }
+#endif
+    }
+  }
+}