[Frontend] Always allow loading the adjacent module for the stdlib

Author: xymus

lib/Frontend/ModuleInterfaceLoader.cpp

@@ -675,7 +675,8 @@ class ModuleInterfaceLoaderImpl {
   std::pair<std::string, std::string> getCompiledModuleCandidates() {
     std::pair<std::string, std::string> result;
     // Should we attempt to load a swiftmodule adjacent to the swiftinterface?
-    bool shouldLoadAdjacentModule = !ctx.IgnoreAdjacentModules;
+    bool shouldLoadAdjacentModule = !ctx.IgnoreAdjacentModules ||
+      moduleName == STDLIB_NAME;
 
     // Don't use the adjacent swiftmodule for frameworks from the public
     // Frameworks folder of the SDK.

lib/Serialization/SerializedModuleLoader.cpp

@@ -23,6 +23,7 @@
 #include "swift/Basic/SourceManager.h"
 #include "swift/Basic/Version.h"
 #include "swift/Option/Options.h"
+#include "swift/Strings.h"
 
 #include "llvm/Option/OptTable.h"
 #include "llvm/Option/ArgList.h"
@@ -445,7 +446,7 @@ std::error_code ImplicitSerializedModuleLoader::findModuleFilesInDirectory(
          "Module and Module Doc buffer must both be initialized or NULL");
 
   if (LoadMode == ModuleLoadingMode::OnlyInterface ||
-      Ctx.IgnoreAdjacentModules)
+      (Ctx.IgnoreAdjacentModules && ModuleID.Item.str() != STDLIB_NAME))
     return std::make_error_code(std::errc::not_supported);
 
   auto ModuleErr = openModuleFile(ModuleID, BaseName, ModuleBuffer);