Introduce command line option -error-on-deserialized-decl that is accompanied by a name
and emits an error if a declaration with this name is deserialized from PCH.

This is for testing, to make sure that we don't deserialize stuff needlessly.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@116505 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index 8f0cb08..3a928a5 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -1409,7 +1409,13 @@
   Opts.UsePredefines = !Args.hasArg(OPT_undef);
   Opts.DetailedRecord = Args.hasArg(OPT_detailed_preprocessing_record);
   Opts.DisablePCHValidation = Args.hasArg(OPT_fno_validate_pch);
+
   Opts.DumpDeserializedPCHDecls = Args.hasArg(OPT_dump_deserialized_pch_decls);
+  for (arg_iterator it = Args.filtered_begin(OPT_error_on_deserialized_pch_decl),
+         ie = Args.filtered_end(); it != ie; ++it) {
+    const Arg *A = *it;
+    Opts.DeserializedPCHDeclsToErrorOn.insert(A->getValue(Args));
+  }
 
   if (const Arg *A = Args.getLastArg(OPT_preamble_bytes_EQ)) {
     llvm::StringRef Value(A->getValue(Args));