Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td	(revision 110572)
+++ include/clang/Basic/DiagnosticSemaKinds.td	(working copy)
@@ -932,6 +932,8 @@
 def warn_gnu_inline_attribute_requires_inline : Warning<
   "'gnu_inline' attribute requires function to be marked 'inline',"
   " attribute ignored">;
+def err_attribute_vecreturn_only_vector_member : Error<
+  "the vecreturn attribute can only be used on a structure with one vector member">;
 def err_cconv_change : Error<
   "function declared '%0' here was previously declared "
   "%select{'%2'|without calling convention}1">;
Index: lib/Sema/SemaDeclAttr.cpp
===================================================================
--- lib/Sema/SemaDeclAttr.cpp	(revision 110609)
+++ lib/Sema/SemaDeclAttr.cpp	(working copy)
@@ -723,6 +723,17 @@
     return;
   }
 
+  CXXRecordDecl *record = static_cast<CXXRecordDecl*>(d);
+  int count = 0;
+
+  for (CXXRecordDecl::field_iterator iter = record->field_begin(); iter != record->field_end(); iter++) {
+    if ((count == 1) || !iter->getType()->isVectorType()) {
+      S.Diag(Attr.getLoc(), diag::err_attribute_vecreturn_only_vector_member);
+      return;
+    }
+    count++;
+  }
+
   d->addAttr(::new (S.Context) VecReturnAttr());
 }