P0840R2: support for [[no_unique_address]] attribute

Summary:
Add support for the C++2a [[no_unique_address]] attribute for targets using the Itanium C++ ABI.

This depends on D63371.

Reviewers: rjmccall, aaron.ballman

Subscribers: dschuff, aheejin, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D63451

llvm-svn: 363976
diff --git a/clang/lib/Parse/ParseDeclCXX.cpp b/clang/lib/Parse/ParseDeclCXX.cpp
index 6f44b84..81a56a0 100644
--- a/clang/lib/Parse/ParseDeclCXX.cpp
+++ b/clang/lib/Parse/ParseDeclCXX.cpp
@@ -3912,6 +3912,7 @@
   case ParsedAttr::AT_Deprecated:
   case ParsedAttr::AT_FallThrough:
   case ParsedAttr::AT_CXX11NoReturn:
+  case ParsedAttr::AT_NoUniqueAddress:
     return true;
   case ParsedAttr::AT_WarnUnusedResult:
     return !ScopeName && AttrName->getName().equals("nodiscard");