7 files changed, 28 insertions, 4 deletions
diff --git a/lib/AST/Decl.cpp b/lib/AST/Decl.cpp
index ffdcb471d0..09bdc15280 100644
--- a/lib/AST/Decl.cpp
+++ b/lib/AST/Decl.cpp
@@ -1596,6 +1596,7 @@ RecordDecl::RecordDecl(Kind DK, TagKind TK, DeclContext *DC, SourceLocation L,
   HasFlexibleArrayMember = false;
   AnonymousStructOrUnion = false;
   HasObjectMember = false;
+  InvisibleToADL = false;
   assert(classof(static_cast<Decl*>(this)) && "Invalid Kind!");
 }
 
diff --git a/lib/Basic/Targets.cpp b/lib/Basic/Targets.cpp
index 92fd417173..871bac9743 100644
--- a/lib/Basic/Targets.cpp
+++ b/lib/Basic/Targets.cpp
@@ -1272,7 +1272,7 @@ public:
            "  unsigned fp_offset;"
            "  void* overflow_arg_area;"
            "  void* reg_save_area;"
-           "} __va_list_tag;"
+           "} __attribute__((adl_invisible)) __va_list_tag;"
            "typedef __va_list_tag __builtin_va_list[1];";
   }
   
diff --git a/lib/Frontend/PCHReaderDecl.cpp b/lib/Frontend/PCHReaderDecl.cpp
index 1ef0441ebf..8af146d676 100644
--- a/lib/Frontend/PCHReaderDecl.cpp
+++ b/lib/Frontend/PCHReaderDecl.cpp
@@ -171,6 +171,7 @@ void PCHDeclReader::VisitRecordDecl(RecordDecl *RD) {
   RD->setHasFlexibleArrayMember(Record[Idx++]);
   RD->setAnonymousStructOrUnion(Record[Idx++]);
   RD->setHasObjectMember(Record[Idx++]);
+  RD->setInvisibleToADL(Record[Idx++]);
 }
 
 void PCHDeclReader::VisitValueDecl(ValueDecl *VD) {
diff --git a/lib/Frontend/PCHWriterDecl.cpp b/lib/Frontend/PCHWriterDecl.cpp
index cc58e8ee46..0ce7d8fcae 100644
--- a/lib/Frontend/PCHWriterDecl.cpp
+++ b/lib/Frontend/PCHWriterDecl.cpp
@@ -169,6 +169,7 @@ void PCHDeclWriter::VisitRecordDecl(RecordDecl *D) {
   Record.push_back(D->hasFlexibleArrayMember());
   Record.push_back(D->isAnonymousStructOrUnion());
   Record.push_back(D->hasObjectMember());
+  Record.push_back(D->isInvisibleToADL());
   Code = pch::DECL_RECORD;
 }
 
diff --git a/lib/Parse/AttributeList.cpp b/lib/Parse/AttributeList.cpp
index 1ebff22e44..333a09cac7 100644
--- a/lib/Parse/AttributeList.cpp
+++ b/lib/Parse/AttributeList.cpp
@@ -120,6 +120,7 @@ AttributeList::Kind AttributeList::getKind(const IdentifierInfo *Name) {
     .Case("cf_returns_retained", AT_cf_returns_retained)
     .Case("reqd_work_group_size", AT_reqd_wg_size)
     .Case("no_instrument_function", AT_no_instrument_function)
+    .Case("adl_invisible", AT_adl_invisible)
     .Case("thiscall", AT_thiscall)
     .Case("__cdecl", AT_cdecl)
     .Case("__stdcall", AT_stdcall)
diff --git a/lib/Sema/SemaDeclAttr.cpp b/lib/Sema/SemaDeclAttr.cpp
index c6dcc3b97b..90d5308168 100644
--- a/lib/Sema/SemaDeclAttr.cpp
+++ b/lib/Sema/SemaDeclAttr.cpp
@@ -703,7 +703,7 @@ static void HandleObjCExceptionAttr(Decl *D, const AttributeList &Attr,
 
 static void HandleObjCNSObject(Decl *D, const AttributeList &Attr, Sema &S) {
   if (Attr.getNumArgs() != 0) {
-    S.Diag(Attr.getLoc(), diag::err_attribute_wrong_number_arguments) << 1;
+    S.Diag(Attr.getLoc(), diag::err_attribute_wrong_number_arguments) << 0;
     return;
   }
   if (TypedefDecl *TD = dyn_cast<TypedefDecl>(D)) {
@@ -720,7 +720,7 @@ static void HandleObjCNSObject(Decl *D, const AttributeList &Attr, Sema &S) {
 static void
 HandleOverloadableAttr(Decl *D, const AttributeList &Attr, Sema &S) {
   if (Attr.getNumArgs() != 0) {
-    S.Diag(Attr.getLoc(), diag::err_attribute_wrong_number_arguments) << 1;
+    S.Diag(Attr.getLoc(), diag::err_attribute_wrong_number_arguments) << 0;
     return;
   }
 
@@ -732,6 +732,21 @@ HandleOverloadableAttr(Decl *D, const AttributeList &Attr, Sema &S) {
   D->addAttr(::new (S.Context) OverloadableAttr());
 }
 
+static void HandleADLInvisibleAttr(Decl *d, const AttributeList &Attr, Sema &S) {
+  if (Attr.getNumArgs() != 0) {
+    S.Diag(Attr.getLoc(), diag::err_attribute_wrong_number_arguments) << 0;
+    return;
+  }
+
+  if (!isa<RecordDecl>(d)) {
+    S.Diag(Attr.getLoc(), diag::err_attribute_wrong_decl_type)
+      << "adl_invisible" << 12;
+    return;
+  }
+
+  cast<RecordDecl>(d)->setInvisibleToADL();
+}
+
 static void HandleBlocksAttr(Decl *d, const AttributeList &Attr, Sema &S) {
   if (!Attr.getParameterName()) {
     S.Diag(Attr.getLoc(), diag::err_attribute_argument_n_not_string)
@@ -941,7 +956,7 @@ static void HandleReqdWorkGroupSize(Decl *D, const AttributeList &Attr,
                                     Sema &S) {
   // Attribute has 3 arguments.
   if (Attr.getNumArgs() != 3) {
-    S.Diag(Attr.getLoc(), diag::err_attribute_wrong_number_arguments) << 1;
+    S.Diag(Attr.getLoc(), diag::err_attribute_wrong_number_arguments) << 3;
     return;
   }
 
@@ -1969,6 +1984,7 @@ static void ProcessDeclAttribute(Scope *scope, Decl *D,
     HandleObjCExceptionAttr(D, Attr, S);
     break;
   case AttributeList::AT_overloadable:HandleOverloadableAttr(D, Attr, S); break;
+  case AttributeList::AT_adl_invisible: HandleADLInvisibleAttr(D, Attr, S); break;
   case AttributeList::AT_nsobject:    HandleObjCNSObject    (D, Attr, S); break;
   case AttributeList::AT_blocks:      HandleBlocksAttr      (D, Attr, S); break;
   case AttributeList::AT_sentinel:    HandleSentinelAttr    (D, Attr, S); break;
diff --git a/lib/Sema/SemaLookup.cpp b/lib/Sema/SemaLookup.cpp
index 16d7305867..8710c496de 100644
--- a/lib/Sema/SemaLookup.cpp
+++ b/lib/Sema/SemaLookup.cpp
@@ -1500,6 +1500,10 @@ addAssociatedClassesAndNamespaces(CXXRecordDecl *Class,
                                   ASTContext &Context,
                             Sema::AssociatedNamespaceSet &AssociatedNamespaces,
                             Sema::AssociatedClassSet &AssociatedClasses) {
+
+  // Some classes are invisible to ADL.
+  if (Class->isInvisibleToADL()) return;
+
   // C++ [basic.lookup.koenig]p2:
   //   [...]
   //     -- If T is a class type (including unions), its associated