Index: lib/Sema/SemaExprCXX.cpp
===================================================================
--- lib/Sema/SemaExprCXX.cpp	(revision 182601)
+++ lib/Sema/SemaExprCXX.cpp	(working copy)
@@ -1554,14 +1554,29 @@
                                /*AllowMissing=*/true, OperatorNew))
       return true;
   }
+
   if (!OperatorNew) {
     // Didn't find a member overload. Look for a global one.
     DeclareGlobalNewDelete();
     DeclContext *TUDecl = Context.getTranslationUnitDecl();
+    bool FallbackEnabled = IsArray && Context.getLangOpts().MicrosoftMode;
     if (FindAllocationOverload(StartLoc, Range, NewName, AllocArgs, TUDecl,
+                               /*AllowMissing=*/FallbackEnabled, OperatorNew,
+                               /*Diagnose=*/!FallbackEnabled)) {
+      if (!FallbackEnabled)
+        return true;
+
+      // MSVC will fall back on trying to find a matching global operator new
+      // if operator new[] cannot be found.  Also, MSVC will leak by not
+      // generating a call to operator delete or operator delete[], but we
+      // will not replicate that bug.
+      NewName = Context.DeclarationNames.getCXXOperatorName(OO_New);
+      DeleteName = Context.DeclarationNames.getCXXOperatorName(OO_Delete);
+      if (FindAllocationOverload(StartLoc, Range, NewName, AllocArgs, TUDecl,
                                /*AllowMissing=*/false, OperatorNew))
       return true;
   }
+  }
 
   // We don't need an operator delete if we're running under
   // -fno-exceptions.
Index: test/CodeGenCXX/microsoft-new.cpp
===================================================================
--- test/CodeGenCXX/microsoft-new.cpp	(revision 0)
+++ test/CodeGenCXX/microsoft-new.cpp	(working copy)
@@ -0,0 +1,37 @@
+// RUN: %clang_cc1 -triple i686-pc-win32 -fms-compatibility %s -emit-llvm -o - | FileCheck %s
+
+struct arbitrary_t {} arbitrary;
+void *operator new(unsigned int size, arbitrary_t);
+
+struct arbitrary2_t {} arbitrary2;
+void *operator new[](unsigned int size, arbitrary2_t);
+
+namespace PR13164 {
+  void f() {
+	// MSVC will fall back on the non-array operator new.
+    void *a;
+    int *p = new(arbitrary) int[4];
+    // CHECK: call i8* @_Znwj11arbitrary_t(i32 16, %struct.arbitrary_t*
+  }
+
+  struct S {
+    void *operator new[](unsigned int size, arbitrary_t);
+  };
+
+  void g() {
+    S *s = new(arbitrary) S[2];
+    // CHECK: call i8* @_ZN7PR131641SnaEj11arbitrary_t(i32 2, %struct.arbitrary_t*
+    S *s1 = new(arbitrary) S;
+    // CHECK: call i8* @_Znwj11arbitrary_t(i32 1, %struct.arbitrary_t*
+  }
+
+  struct T {
+    void *operator new(unsigned int size, arbitrary2_t);
+  };
+
+  void h() {
+    // This should still call the global operator new[].
+    T *t = new(arbitrary2) T[2];
+    // CHECK: call i8* @_Znaj12arbitrary2_t(i32 2, %struct.arbitrary2_t*
+  }
+}
Index: test/SemaCXX/microsoft-new-delete.cpp
===================================================================
--- test/SemaCXX/microsoft-new-delete.cpp	(revision 0)
+++ test/SemaCXX/microsoft-new-delete.cpp	(working copy)
@@ -0,0 +1,10 @@
+// RUN: %clang_cc1 -fms-compatibility -fsyntax-only -verify %s
+// expected-no-diagnostics
+
+struct arbitrary_t {} arbitrary;
+void *operator new(unsigned int size, arbitrary_t);
+
+void f() {
+  // Expect no error in MSVC compatibility mode
+  int *p = new(arbitrary) int[4];
+}