[clang][Interp] Handle __datasizeof.

Author: tbaederr

clang/lib/AST/Interp/ByteCodeExprGen.cpp

@@ -1096,9 +1096,9 @@ template <class Emitter>
 bool ByteCodeExprGen<Emitter>::VisitUnaryExprOrTypeTraitExpr(
     const UnaryExprOrTypeTraitExpr *E) {
   UnaryExprOrTypeTrait Kind = E->getKind();
-  ASTContext &ASTCtx = Ctx.getASTContext();
+  const ASTContext &ASTCtx = Ctx.getASTContext();
 
-  if (Kind == UETT_SizeOf) {
+  if (Kind == UETT_SizeOf || Kind == UETT_DataSizeOf) {
     QualType ArgType = E->getTypeOfArgument();
 
     // C++ [expr.sizeof]p2: "When applied to a reference or a reference type,
@@ -1113,7 +1113,10 @@ bool ByteCodeExprGen<Emitter>::VisitUnaryExprOrTypeTraitExpr(
       if (ArgType->isDependentType() || !ArgType->isConstantSizeType())
         return false;
 
-      Size = ASTCtx.getTypeSizeInChars(ArgType);
+      if (Kind == UETT_SizeOf)
+        Size = ASTCtx.getTypeSizeInChars(ArgType);
+      else
+        Size = ASTCtx.getTypeInfoDataSizeInChars(ArgType).Width;
     }
 
     if (DiscardResult)

clang/test/SemaCXX/datasizeof.cpp

@@ -1,4 +1,5 @@
 // RUN: %clang_cc1 -fsyntax-only -triple x86_64-linux-gnu -verify %s
+// RUN: %clang_cc1 -fsyntax-only -triple x86_64-linux-gnu -verify %s -fexperimental-new-constant-interpreter
 
 #if !__has_extension(datasizeof)
 #  error "Expected datasizeof extension"