diff --git a/clang/include/clang/AST/DeclObjC.h b/clang/include/clang/AST/DeclObjC.h
--- a/clang/include/clang/AST/DeclObjC.h
+++ b/clang/include/clang/AST/DeclObjC.h
@@ -25,8 +25,8 @@
 #include "clang/Basic/SourceLocation.h"
 #include "clang/Basic/Specifiers.h"
 #include "llvm/ADT/ArrayRef.h"
-#include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/DenseSet.h"
+#include "llvm/ADT/MapVector.h"
 #include "llvm/ADT/None.h"
 #include "llvm/ADT/PointerIntPair.h"
 #include "llvm/ADT/STLExtras.h"
@@ -1079,8 +1079,8 @@
                           ObjCPropertyQueryKind QueryKind) const;
 
   using PropertyMap =
-      llvm::DenseMap<std::pair<IdentifierInfo *, unsigned/*isClassProperty*/>,
-                     ObjCPropertyDecl *>;
+      llvm::MapVector<std::pair<IdentifierInfo *, unsigned /*isClassProperty*/>,
+                      ObjCPropertyDecl *>;
   using ProtocolPropertySet = llvm::SmallDenseSet<const ObjCProtocolDecl *, 8>;
   using PropertyDeclOrder = llvm::SmallVector<ObjCPropertyDecl *, 8>;
 
diff --git a/clang/include/clang/Sema/Scope.h b/clang/include/clang/Sema/Scope.h
--- a/clang/include/clang/Sema/Scope.h
+++ b/clang/include/clang/Sema/Scope.h
@@ -16,6 +16,7 @@
 #include "clang/AST/Decl.h"
 #include "clang/Basic/Diagnostic.h"
 #include "llvm/ADT/PointerIntPair.h"
+#include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/iterator_range.h"
@@ -196,7 +197,7 @@
   /// popped, these declarations are removed from the IdentifierTable's notion
   /// of current declaration.  It is up to the current Action implementation to
   /// implement these semantics.
-  using DeclSetTy = llvm::SmallPtrSet<Decl *, 32>;
+  using DeclSetTy = llvm::SmallSetVector<Decl *, 32>;
   DeclSetTy DeclsInScope;
 
   /// The DeclContext with which this scope is associated. For
@@ -321,9 +322,7 @@
     DeclsInScope.insert(D);
   }
 
-  void RemoveDecl(Decl *D) {
-    DeclsInScope.erase(D);
-  }
+  void RemoveDecl(Decl *D) { DeclsInScope.remove(D); }
 
   void incrementMSManglingNumber() {
     if (Scope *MSLMP = getMSLastManglingParent()) {
@@ -351,7 +350,9 @@
 
   /// isDeclScope - Return true if this is the scope that the specified decl is
   /// declared in.
-  bool isDeclScope(const Decl *D) const { return DeclsInScope.contains(D); }
+  bool isDeclScope(const Decl *D) const {
+    return DeclsInScope.contains(const_cast<Decl *>(D));
+  }
 
   /// Get the entity corresponding to this scope.
   DeclContext *getEntity() const {
diff --git a/clang/test/Sema/deterministic-diagnostics-order.m b/clang/test/Sema/deterministic-diagnostics-order.m
new file mode 100644
--- /dev/null
+++ b/clang/test/Sema/deterministic-diagnostics-order.m
@@ -0,0 +1,116 @@
+// RUN: %clang_cc1 %s -fsyntax-only -Wobjc-property-implementation -Watomic-property-with-user-defined-accessor -Wunused 2> %t.err
+// RUN: FileCheck -input-file=%t.err %s
+
+@interface I
+@end
+
+@interface I(cat)
+@property id prop1;
+@property id prop2;
+@property id prop3;
+@end
+
+@implementation I(cat)
+@end
+
+// CHECK: warning: property 'prop1' requires method
+// CHECK: warning: property 'prop2' requires method
+// CHECK: warning: property 'prop3' requires method
+
+@interface I2
+@property int prop1;
+@property int prop2;
+@property int prop3;
+@end
+
+@implementation I2
+@synthesize prop1, prop2, prop3;
+-(int) prop1 { return 0; }
+-(int) prop2 { return 0; }
+-(int) prop3 { return 0; }
+@end
+
+// CHECK: warning: writable atomic property 'prop1'
+// CHECK: warning: writable atomic property 'prop2'
+// CHECK: warning: writable atomic property 'prop3'
+
+void test_unused() {
+  // Add enough variables to exceed the small storage of Scope::DeclSetTy.
+  int v1;
+  int v2;
+  int v3;
+  int v4;
+  int v5;
+  int v6;
+  int v7;
+  int v8;
+  int v9;
+  int v10;
+  int v11;
+  int v12;
+  int v13;
+  int v14;
+  int v15;
+  int v16;
+  int v17;
+  int v18;
+  int v19;
+  int v20;
+  int v21;
+  int v22;
+  int v23;
+  int v24;
+  int v25;
+  int v26;
+  int v27;
+  int v28;
+  int v29;
+  int v30;
+  int v31;
+  int v32;
+  int v33;
+  int v34;
+  int v35;
+  int v36;
+  int v37;
+  int v38;
+}
+
+// CHECK: warning: unused variable 'v1'
+// CHECK: warning: unused variable 'v2'
+// CHECK: warning: unused variable 'v3'
+// CHECK: warning: unused variable 'v4'
+// CHECK: warning: unused variable 'v5'
+// CHECK: warning: unused variable 'v6'
+// CHECK: warning: unused variable 'v7'
+// CHECK: warning: unused variable 'v8'
+// CHECK: warning: unused variable 'v9'
+// CHECK: warning: unused variable 'v10'
+// CHECK: warning: unused variable 'v11'
+// CHECK: warning: unused variable 'v12'
+// CHECK: warning: unused variable 'v13'
+// CHECK: warning: unused variable 'v14'
+// CHECK: warning: unused variable 'v15'
+// CHECK: warning: unused variable 'v16'
+// CHECK: warning: unused variable 'v17'
+// CHECK: warning: unused variable 'v18'
+// CHECK: warning: unused variable 'v19'
+// CHECK: warning: unused variable 'v20'
+// CHECK: warning: unused variable 'v21'
+// CHECK: warning: unused variable 'v22'
+// CHECK: warning: unused variable 'v23'
+// CHECK: warning: unused variable 'v24'
+// CHECK: warning: unused variable 'v25'
+// CHECK: warning: unused variable 'v26'
+// CHECK: warning: unused variable 'v27'
+// CHECK: warning: unused variable 'v28'
+// CHECK: warning: unused variable 'v29'
+// CHECK: warning: unused variable 'v30'
+// CHECK: warning: unused variable 'v31'
+// CHECK: warning: unused variable 'v32'
+// CHECK: warning: unused variable 'v33'
+// CHECK: warning: unused variable 'v34'
+// CHECK: warning: unused variable 'v35'
+// CHECK: warning: unused variable 'v36'
+// CHECK: warning: unused variable 'v37'
+// CHECK: warning: unused variable 'v38'