Back off the WholeModule change to CompilerInstance::createSILModule()

(May be needed in this form for sil-opt.)

Author: David Ungar

lib/Frontend/Frontend.cpp

@@ -55,8 +55,10 @@ std::string CompilerInvocation::getPCHHash() const {
 
 void CompilerInstance::createSILModule() {
   assert(MainModule && "main module not created yet");
+  // Assume WMO if a -primary-file option was not provided.
+  bool WholeModule = !Invocation.getFrontendOptions().PrimaryInput.hasValue();
   TheSILModule = SILModule::createEmptyModule(
-    getMainModule(), Invocation.getSILOptions(), isWholeModuleCompilation());
+    getMainModule(), Invocation.getSILOptions(), WholeModule);
 }
 
 void CompilerInstance::setPrimarySourceFile(SourceFile *SF) {