Frontend: Don't record request references in WMO builds

Part of <rdar://problem/72906325>.

Author: slavapestov

include/swift/AST/DependencyCollector.h

@@ -27,7 +27,7 @@ class NominalTypeDecl;
 
 namespace evaluator {
 
-struct DependencyRecorder;
+class DependencyRecorder;
 
 /// A \c DependencyCollector defines an abstract write-only buffer of
 /// \c Reference objects. References are added to a collector during the write

include/swift/AST/EvaluatorDependencies.h

@@ -47,10 +47,13 @@ using DependencySource = swift::NullablePtr<SourceFile>;
 
 /// A \c DependencyRecorder is an aggregator of named references discovered in a
 /// particular \c DependencyScope during the course of request evaluation.
-struct DependencyRecorder {
+class DependencyRecorder {
   friend DependencyCollector;
 
-private:
+  /// Whether we are performing an incremental build and should therefore
+  /// record request references.
+  bool shouldRecord;
+
   /// References recorded while evaluating a dependency source request for each
   /// source file. This map is updated upon completion of a dependency source
   /// request, and includes all references from each downstream request as well.
@@ -82,6 +85,8 @@ struct DependencyRecorder {
 #endif
 
 public:
+  DependencyRecorder(bool shouldRecord) : shouldRecord(shouldRecord) {}
+
   /// Push a new empty set onto the activeRequestReferences stack.
   template<typename Request>
   void beginRequest();
@@ -131,6 +136,9 @@ struct DependencyRecorder {
 
 template<typename Request>
 void evaluator::DependencyRecorder::beginRequest() {
+  if (!shouldRecord)
+    return;
+
   if (!Request::isEverCached && !Request::isDependencySource)
     return;
 
@@ -139,6 +147,9 @@ void evaluator::DependencyRecorder::beginRequest() {
 
 template<typename Request>
 void evaluator::DependencyRecorder::endRequest(const Request &req) {
+  if (!shouldRecord)
+    return;
+
   if (!Request::isEverCached && !Request::isDependencySource)
     return;
 
@@ -170,6 +181,9 @@ template<typename Request>
 void evaluator::DependencyRecorder::replayCachedRequest(const Request &req) {
   assert(req.isCached());
 
+  if (!shouldRecord)
+    return;
+
   if (activeRequestReferences.empty())
     return;
 

include/swift/Basic/LangOptions.h

@@ -218,6 +218,9 @@ namespace swift {
     /// Enable named lazy member loading.
     bool NamedLazyMemberLoading = true;
 
+    /// Whether to record request references for incremental builds.
+    bool RecordRequestReferences = true;
+
     /// The path to which we should emit GraphViz output for the complete
     /// request-evaluator graph.
     std::string RequestEvaluatorGraphVizPath;

lib/AST/Evaluator.cpp

@@ -67,7 +67,7 @@ Evaluator::Evaluator(DiagnosticEngine &diags, const LangOptions &opts)
     : diags(diags),
       debugDumpCycles(opts.DebugDumpCycles),
       buildDependencyGraph(opts.BuildRequestDependencyGraph),
-      recorder{} {}
+      recorder(opts.RecordRequestReferences) {}
 
 void Evaluator::emitRequestEvaluatorGraphViz(llvm::StringRef graphVizPath) {
   std::error_code error;

lib/Frontend/Frontend.cpp

@@ -205,6 +205,11 @@ bool CompilerInstance::setUpASTContextIfNeeded() {
     return false;
   }
 
+  // For the time being, we only need to record dependencies in batch mode
+  // and single file builds.
+  Invocation.getLangOptions().RecordRequestReferences
+    = !isWholeModuleCompilation();
+
   Context.reset(ASTContext::get(
       Invocation.getLangOptions(), Invocation.getTypeCheckerOptions(),
       Invocation.getSearchPathOptions(),