Index: include/clang/AST/DeclBase.h
===================================================================
--- include/clang/AST/DeclBase.h
+++ include/clang/AST/DeclBase.h
@@ -481,13 +481,7 @@
 
   const AttrVec &getAttrs() const;
   void dropAttrs();
-
-  void addAttr(Attr *A) {
-    if (hasAttrs())
-      getAttrs().push_back(A);
-    else
-      setAttrs(AttrVec(1, A));
-  }
+  void addAttr(Attr *A);
 
   using attr_iterator = AttrVec::const_iterator;
   using attr_range = llvm::iterator_range<attr_iterator>;
Index: lib/AST/DeclBase.cpp
===================================================================
--- lib/AST/DeclBase.cpp
+++ lib/AST/DeclBase.cpp
@@ -836,6 +836,29 @@
   getASTContext().eraseDeclAttrs(this);
 }
 
+void Decl::addAttr(Attr *A) {
+  if (!hasAttrs()) {
+    setAttrs(AttrVec(1, A));
+    return;
+  }
+
+  AttrVec &Attrs = getAttrs();
+  if (!A->isInherited()) {
+    Attrs.push_back(A);
+    return;
+  }
+
+  // Attribute inheritance is processed after attribute parsing. To keep the
+  // order as in the source code, add inherited attributes before non-inherited
+  // ones.
+  auto I = Attrs.begin(), E = Attrs.end();
+  for (; I != E; ++I) {
+    if (!(*I)->isInherited())
+      break;
+  }
+  Attrs.insert(I, A);
+}
+
 const AttrVec &Decl::getAttrs() const {
   assert(HasAttrs && "No attrs to get!");
   return getASTContext().getDeclAttrs(this);
Index: test/Misc/ast-dump-attr.cpp
===================================================================
--- test/Misc/ast-dump-attr.cpp
+++ test/Misc/ast-dump-attr.cpp
@@ -209,3 +209,24 @@
       }
     }
 }
+
+// Verify the order of attributes in the Ast. It must reflect the order
+// in the parsed source.
+int mergeAttrTest() __attribute__((deprecated)) __attribute__((warn_unused_result));
+int mergeAttrTest() __attribute__((annotate("test")));
+int mergeAttrTest() __attribute__((unused,no_thread_safety_analysis));
+// CHECK: FunctionDecl{{.*}} mergeAttrTest
+// CHECK-NEXT: DeprecatedAttr
+// CHECK-NEXT: WarnUnusedResultAttr
+
+// CHECK: FunctionDecl{{.*}} mergeAttrTest
+// CHECK-NEXT: DeprecatedAttr{{.*}} Inherited
+// CHECK-NEXT: WarnUnusedResultAttr{{.*}} Inherited
+// CHECK-NEXT: AnnotateAttr{{.*}}
+
+// CHECK: FunctionDecl{{.*}} mergeAttrTest
+// CHECK-NEXT: DeprecatedAttr{{.*}} Inherited
+// CHECK-NEXT: WarnUnusedResultAttr{{.*}} Inherited
+// CHECK-NEXT: AnnotateAttr{{.*}} Inherited
+// CHECK-NEXT: UnusedAttr
+// CHECK-NEXT: NoThreadSafetyAnalysisAttr
Index: test/Sema/attr-availability-ios.c
===================================================================
--- test/Sema/attr-availability-ios.c
+++ test/Sema/attr-availability-ios.c
@@ -7,8 +7,8 @@
 void f4(int) __attribute__((availability(macosx,introduced=10.1,deprecated=10.3,obsoleted=10.5), availability(ios,introduced=2.0,deprecated=2.1,obsoleted=3.0))); // expected-note{{explicitly marked unavailable}}
 
 void f5(int) __attribute__((availability(ios,introduced=2.0))) __attribute__((availability(ios,deprecated=3.0))); // expected-note {{'f5' has been explicitly marked deprecated here}}
-void f6(int) __attribute__((availability(ios,deprecated=3.0)));
-void f6(int) __attribute__((availability(iOS,introduced=2.0))); // expected-note {{'f6' has been explicitly marked deprecated here}}
+void f6(int) __attribute__((availability(ios,deprecated=3.0))); // expected-note {{'f6' has been explicitly marked deprecated here}}
+void f6(int) __attribute__((availability(iOS,introduced=2.0)));
 
 void test() {
   f0(0); // expected-warning{{'f0' is deprecated: first deprecated in iOS 2.1}}
Index: test/Sema/attr-availability-tvos.c
===================================================================
--- test/Sema/attr-availability-tvos.c
+++ test/Sema/attr-availability-tvos.c
@@ -7,8 +7,8 @@
 void f4(int) __attribute__((availability(macosx,introduced=10.1,deprecated=10.3,obsoleted=10.5), availability(tvos,introduced=2.0,deprecated=2.1,obsoleted=3.0))); // expected-note{{explicitly marked unavailable}}
 
 void f5(int) __attribute__((availability(tvos,introduced=2.0))) __attribute__((availability(tvos,deprecated=3.0))); // expected-note {{'f5' has been explicitly marked deprecated here}}
-void f6(int) __attribute__((availability(tvos,deprecated=3.0)));
-void f6(int) __attribute__((availability(tvos,introduced=2.0))); // expected-note {{'f6' has been explicitly marked deprecated here}}
+void f6(int) __attribute__((availability(tvos,deprecated=3.0))); // expected-note {{'f6' has been explicitly marked deprecated here}}
+void f6(int) __attribute__((availability(tvos,introduced=2.0)));
 
 void test() {
   f0(0); // expected-warning{{'f0' is deprecated: first deprecated in tvOS 2.1}}
@@ -41,8 +41,8 @@
 void f5_attr_reversed_tvos(int) __attribute__((availability(ios, deprecated=3.0))) __attribute__((availability(tvos,introduced=2.0)));
 void f5b_tvos(int) __attribute__((availability(tvos,introduced=2.0))) __attribute__((availability(tvos,deprecated=3.0))); // expected-note {{'f5b_tvos' has been explicitly marked deprecated here}}
 void f5c_tvos(int) __attribute__((availability(ios,introduced=2.0))) __attribute__((availability(ios,deprecated=3.0))); // expected-note {{'f5c_tvos' has been explicitly marked deprecated here}}
-void f6_tvos(int) __attribute__((availability(tvos,deprecated=3.0)));
-void f6_tvos(int) __attribute__((availability(tvOS,introduced=2.0))); // expected-note {{'f6_tvos' has been explicitly marked deprecated here}}
+void f6_tvos(int) __attribute__((availability(tvos,deprecated=3.0))); // expected-note {{'f6_tvos' has been explicitly marked deprecated here}}
+void f6_tvos(int) __attribute__((availability(tvOS,introduced=2.0)));
 
 void test_tvos() {
   f0_tvos(0); // expected-warning{{'f0_tvos' is deprecated: first deprecated in tvOS 2.1}}
Index: test/Sema/attr-availability-watchos.c
===================================================================
--- test/Sema/attr-availability-watchos.c
+++ test/Sema/attr-availability-watchos.c
@@ -32,8 +32,8 @@
 void f5_attr_reversed_watchos(int) __attribute__((availability(ios, deprecated=3.0))) __attribute__((availability(watchos,introduced=2.0)));
 void f5b_watchos(int) __attribute__((availability(watchos,introduced=2.0))) __attribute__((availability(watchos,deprecated=3.0))); // expected-note {{'f5b_watchos' has been explicitly marked deprecated here}}
 void f5c_watchos(int) __attribute__((availability(ios,introduced=2.0))) __attribute__((availability(ios,deprecated=3.0))); // expected-note {{'f5c_watchos' has been explicitly marked deprecated here}}
-void f6_watchos(int) __attribute__((availability(watchos,deprecated=3.0)));
-void f6_watchos(int) __attribute__((availability(watchOS,introduced=2.0))); // expected-note {{'f6_watchos' has been explicitly marked deprecated here}}
+void f6_watchos(int) __attribute__((availability(watchos,deprecated=3.0))); // expected-note {{'f6_watchos' has been explicitly marked deprecated here}}
+void f6_watchos(int) __attribute__((availability(watchOS,introduced=2.0)));
 
 void test_watchos() {
   f0_watchos(0); // expected-warning{{'f0_watchos' is deprecated: first deprecated in watchOS 2.1}}