Allow dynamic_cast to void* even with -fno-rtti.

PR17346.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@191340 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaCast.cpp b/lib/Sema/SemaCast.cpp
index 46b5b45..ba00b71 100644
--- a/lib/Sema/SemaCast.cpp
+++ b/lib/Sema/SemaCast.cpp
@@ -669,8 +669,10 @@
   Self.MarkVTableUsed(OpRange.getBegin(), 
                       cast<CXXRecordDecl>(SrcRecord->getDecl()));
 
-  // dynamic_cast is not available with fno-rtti
-  if (!Self.getLangOpts().RTTI) {
+  // dynamic_cast is not available with -fno-rtti.
+  // As an exception, dynamic_cast to void* is available because it doesn't
+  // use RTTI.
+  if (!Self.getLangOpts().RTTI && !DestPointee->isVoidType()) {
     Self.Diag(OpRange.getBegin(), diag::err_no_dynamic_cast_with_fno_rtti);
     SrcExpr = ExprError();
     return;