Allow __attribute__((unused)) for fields and make it silence
-Wunused-private-field.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@158411 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaDeclCXX.cpp b/lib/Sema/SemaDeclCXX.cpp
index 4bd1c32..12a63b1 100644
--- a/lib/Sema/SemaDeclCXX.cpp
+++ b/lib/Sema/SemaDeclCXX.cpp
@@ -1646,6 +1646,7 @@
       // effects and are not part of a dependent type declaration.
       if (!FD->isImplicit() && FD->getDeclName() &&
           FD->getAccess() == AS_private &&
+          !FD->hasAttr<UnusedAttr>() &&
           !FD->getParent()->getTypeForDecl()->isDependentType() &&
           !InitializationHasSideEffects(*FD))
         UnusedPrivateFields.insert(FD);