5 files changed, 12 insertions, 2 deletions
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 51b5ae91d6a..0b3e60f82a8 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -5028,8 +5028,11 @@ Decl *Sema::ActOnFinishFunctionBody(Decl *dcl, Stmt *Body,
     // Verify that we have no forward references left.  If so, there was a goto
     // or address of a label taken, but no definition of it.  Label fwd
     // definitions are indicated with a null substmt.
-    if (L->getSubStmt() != 0)
+    if (L->getSubStmt() != 0) {
+      if (!L->isUsed())
+        Diag(L->getIdentLoc(), diag::warn_unused_label) << L->getName();
       continue;
+    }
 
     // Emit error.
     Diag(L->getIdentLoc(), diag::err_undeclared_label_use) << L->getName();
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 4bd596b6728..40009844482 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -6871,6 +6871,7 @@ ExprResult Sema::ActOnAddrLabel(SourceLocation OpLoc,
   if (LabelDecl == 0)
     LabelDecl = new (Context) LabelStmt(LabLoc, LabelII, 0);
 
+  LabelDecl->setUsed();
   // Create the AST node.  The address of a label always has type 'void*'.
   return Owned(new (Context) AddrLabelExpr(OpLoc, LabLoc, LabelDecl,
                                        Context.getPointerType(Context.VoidTy)));
@@ -7355,8 +7356,11 @@ ExprResult Sema::ActOnBlockStmtExpr(SourceLocation CaretLoc,
 
     // Verify that we have no forward references left.  If so, there was a goto
     // or address of a label taken, but no definition of it.
-    if (L->getSubStmt() != 0)
+    if (L->getSubStmt() != 0) {
+      if (!L->isUsed())
+        Diag(L->getIdentLoc(), diag::warn_unused_label) << L->getName();
       continue;
+    }
 
     // Emit error.
     Diag(L->getIdentLoc(), diag::err_undeclared_label_use) << L->getName();
diff --git a/clang/lib/Sema/SemaStmt.cpp b/clang/lib/Sema/SemaStmt.cpp
index 47ea4f2c253..24489544e06 100644
--- a/clang/lib/Sema/SemaStmt.cpp
+++ b/clang/lib/Sema/SemaStmt.cpp
@@ -994,6 +994,7 @@ Sema::ActOnGotoStmt(SourceLocation GotoLoc, SourceLocation LabelLoc,
   if (LabelDecl == 0)
     LabelDecl = new (Context) LabelStmt(LabelLoc, LabelII, 0);
 
+  LabelDecl->setUsed();
   return Owned(new (Context) GotoStmt(LabelDecl, GotoLoc, LabelLoc));
 }
 
diff --git a/clang/lib/Serialization/ASTReaderStmt.cpp b/clang/lib/Serialization/ASTReaderStmt.cpp
index 6e8ad4fc447..7b0845d5e7b 100644
--- a/clang/lib/Serialization/ASTReaderStmt.cpp
+++ b/clang/lib/Serialization/ASTReaderStmt.cpp
@@ -219,6 +219,7 @@ void ASTStmtReader::VisitLabelStmt(LabelStmt *S) {
   S->setID(Reader.GetIdentifierInfo(Record, Idx));
   S->setSubStmt(Reader.ReadSubStmt());
   S->setIdentLoc(SourceLocation::getFromRawEncoding(Record[Idx++]));
+  S->setUsed(Record[Idx++]);
   Reader.RecordLabelStmt(S, Record[Idx++]);
 }
 
diff --git a/clang/lib/Serialization/ASTWriterStmt.cpp b/clang/lib/Serialization/ASTWriterStmt.cpp
index 7a5b9497a82..edd8002d47c 100644
--- a/clang/lib/Serialization/ASTWriterStmt.cpp
+++ b/clang/lib/Serialization/ASTWriterStmt.cpp
@@ -213,6 +213,7 @@ void ASTStmtWriter::VisitLabelStmt(LabelStmt *S) {
   Writer.AddIdentifierRef(S->getID(), Record);
   Writer.AddStmt(S->getSubStmt());
   Writer.AddSourceLocation(S->getIdentLoc(), Record);
+  Record.push_back(S->isUsed());
   Record.push_back(Writer.GetLabelID(S));
   Code = serialization::STMT_LABEL;
 }