Index: llvm/tools/clang/include/clang/Sema/Sema.h
===================================================================
--- llvm/tools/clang/include/clang/Sema/Sema.h
+++ llvm/tools/clang/include/clang/Sema/Sema.h
@@ -3110,6 +3110,7 @@
   void ProcessPragmaWeak(Scope *S, Decl *D);
   // Decl attributes - this routine is the top level dispatcher.
   void ProcessDeclAttributes(Scope *S, Decl *D, const Declarator &PD);
+  void ProcessDeclAttributeDelayed(Decl *D, const AttributeList *AttrList);
   void ProcessDeclAttributeList(Scope *S, Decl *D, const AttributeList *AL,
                                 bool IncludeCXX11Attributes = true);
   bool ProcessAccessDeclAttributeList(AccessSpecDecl *ASDecl,
Index: llvm/tools/clang/lib/Parse/ParseDeclCXX.cpp
===================================================================
--- llvm/tools/clang/lib/Parse/ParseDeclCXX.cpp
+++ llvm/tools/clang/lib/Parse/ParseDeclCXX.cpp
@@ -1885,6 +1885,9 @@
       ParseStructUnionBody(StartLoc, TagType, TagOrTempResult.get());
   }
 
+  if (!TagOrTempResult.isInvalid())
+    Actions.ProcessDeclAttributeDelayed(TagOrTempResult.get(), attrs.getList());
+
   const char *PrevSpec = nullptr;
   unsigned DiagID;
   bool Result;
Index: llvm/tools/clang/lib/Sema/SemaDeclAttr.cpp
===================================================================
--- llvm/tools/clang/lib/Sema/SemaDeclAttr.cpp
+++ llvm/tools/clang/lib/Sema/SemaDeclAttr.cpp
@@ -3193,8 +3193,9 @@
   }
 
   if (!RD->isCompleteDefinition()) {
-    S.Diag(Attr.getLoc(),
-        diag::warn_transparent_union_attribute_not_definition);
+    if (RD->isBeingDefined())
+      S.Diag(Attr.getLoc(),
+             diag::warn_transparent_union_attribute_not_definition);
     return;
   }
 
@@ -6282,6 +6283,15 @@
   }
 }
 
+// Helper for delayed proccessing TransparentUnion attribute.
+void Sema::ProcessDeclAttributeDelayed(Decl *D, const AttributeList *AttrList) {
+  for (const AttributeList* l = AttrList; l; l = l->getNext())
+    if (l->getKind() == AttributeList::AT_TransparentUnion) {
+      handleTransparentUnionAttr(*this, D, *l);
+      break;
+    }
+}
+
 // Annotation attributes are the only attributes allowed after an access
 // specifier.
 bool Sema::ProcessAccessDeclAttributeList(AccessSpecDecl *ASDecl,
Index: llvm/tools/clang/test/CodeGen/transparent-union.c
===================================================================
--- llvm/tools/clang/test/CodeGen/transparent-union.c
+++ llvm/tools/clang/test/CodeGen/transparent-union.c
@@ -3,10 +3,21 @@
 // RUN: %clang_cc1 -Werror -triple armv7-linux -emit-llvm -o - %s | FileCheck %s --check-prefix=ARM
 // RUN: %clang_cc1 -Werror -triple powerpc64le-linux -emit-llvm -o - %s | FileCheck %s
 // RUN: %clang_cc1 -Werror -triple aarch64-linux -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 -DINFRONT -Werror -triple x86_64-linux -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 -DINFRONT -Werror -triple i386-linux -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 -DINFRONT -Werror -triple armv7-linux -emit-llvm -o - %s | FileCheck %s --check-prefix=ARM
+// RUN: %clang_cc1 -DINFRONT -Werror -triple powerpc64le-linux -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 -DINFRONT -Werror -triple aarch64-linux -emit-llvm -o - %s | FileCheck %s
 
+#ifdef INFRONT
+typedef union __attribute__((transparent_union)) {
+  void *f0;
+} transp_t0;
+#else
 typedef union {
   void *f0;
 } transp_t0 __attribute__((transparent_union));
+#endif
 
 void f0(transp_t0 obj);
 
Index: llvm/tools/clang/test/Sema/transparent-union.c
===================================================================
--- llvm/tools/clang/test/Sema/transparent-union.c
+++ llvm/tools/clang/test/Sema/transparent-union.c
@@ -98,3 +98,17 @@
 union pr30520s { struct stb b; } __attribute__((transparent_union)); // expected-error {{field has incomplete type 'struct stb'}}
 
 union pr30520s2 { int *v; struct stb b; } __attribute__((transparent_union)); // expected-error {{field has incomplete type 'struct stb'}}
+
+typedef union __attribute__((__transparent_union__)) {
+  int *i;
+  struct st *s;
+} TU6;
+
+void bar(TU6);
+
+void foo11(int *i) {
+  bar(i);
+}
+void foo2(struct st *s) {
+  bar(s);
+}