[Frontend] Split off loadAccessNotesIfNeeded

This ought to be requestified, but for now let's split it into its
own function.

Author: hamishknight

include/swift/Frontend/Frontend.h

@@ -781,6 +781,11 @@ class CompilerInstance {
   /// Parses and type-checks all input files.
   void performSema();
 
+  /// Loads any access notes for the main module.
+  ///
+  /// FIXME: This should be requestified.
+  void loadAccessNotesIfNeeded();
+
   /// Parses and performs import resolution on all input files.
   ///
   /// This is similar to a parse-only invocation, but module imports will also

lib/Frontend/Frontend.cpp

@@ -1543,33 +1543,40 @@ void CompilerInstance::setMainModule(ModuleDecl *newMod) {
   Context->MainModule = newMod;
 }
 
+void CompilerInstance::loadAccessNotesIfNeeded() {
+  if (Invocation.getFrontendOptions().AccessNotesPath.empty())
+    return;
+
+  auto *mainModule = getMainModule();
+
+  auto accessNotesPath = Invocation.getFrontendOptions().AccessNotesPath;
+
+  auto bufferOrError =
+      swift::vfs::getFileOrSTDIN(getFileSystem(), accessNotesPath);
+  if (bufferOrError) {
+    int sourceID = SourceMgr.addNewSourceBuffer(std::move(bufferOrError.get()));
+    auto buffer = SourceMgr.getLLVMSourceMgr().getMemoryBuffer(sourceID);
+
+    if (auto accessNotesFile = AccessNotesFile::load(*Context, buffer))
+      mainModule->getAccessNotes() = *accessNotesFile;
+  } else {
+    Diagnostics.diagnose(SourceLoc(), diag::access_notes_file_io_error,
+                         accessNotesPath, bufferOrError.getError().message());
+  }
+}
+
 bool CompilerInstance::performParseAndResolveImportsOnly() {
   FrontendStatsTracer tracer(getStatsReporter(), "parse-and-resolve-imports");
 
-  auto *mainModule = getMainModule();
+  // NOTE: Do not add new logic to this function, use the request evaluator to
+  // lazily evaluate instead. Once the below computations are requestified we
+  // ought to be able to remove this function.
 
   // Load access notes.
-  if (!Invocation.getFrontendOptions().AccessNotesPath.empty()) {
-    auto accessNotesPath = Invocation.getFrontendOptions().AccessNotesPath;
-
-    auto bufferOrError =
-        swift::vfs::getFileOrSTDIN(getFileSystem(), accessNotesPath);
-    if (bufferOrError) {
-      int sourceID =
-          SourceMgr.addNewSourceBuffer(std::move(bufferOrError.get()));
-      auto buffer =
-          SourceMgr.getLLVMSourceMgr().getMemoryBuffer(sourceID);
-
-      if (auto accessNotesFile = AccessNotesFile::load(*Context, buffer))
-        mainModule->getAccessNotes() = *accessNotesFile;
-    }
-    else {
-      Diagnostics.diagnose(SourceLoc(), diag::access_notes_file_io_error,
-                           accessNotesPath, bufferOrError.getError().message());
-    }
-  }
+  loadAccessNotesIfNeeded();
 
   // Resolve imports for all the source files in the module.
+  auto *mainModule = getMainModule();
   performImportResolution(mainModule);
 
   bindExtensions(*mainModule);