[libSyntax] Don't create dedicated deferred nodes in SyntaxTreeCreator

include/swift/Parse/SyntaxParseActions.h

@@ -82,8 +82,6 @@ struct DeferredNodeInfo {
 // MARK: - SyntaxParseActions
 
 class SyntaxParseActions {
-  llvm::BumpPtrAllocator DeferredNodeAllocator;
-
   virtual void _anchor();
 
 public:
@@ -111,24 +109,24 @@ class SyntaxParseActions {
                                              StringRef leadingTrivia,
                                              StringRef trailingTrivia,
                                              CharSourceRange range,
-                                             bool isMissing);
+                                             bool isMissing) = 0;
 
   /// Create a deferred layout node that may or may not be recorded later using
   /// \c recordDeferredLayout. The \c SyntaxParseAction is responsible for
   /// keeping the deferred token alive until it is destructed.
   virtual OpaqueSyntaxNode
   makeDeferredLayout(syntax::SyntaxKind k, bool isMissing,
-                     const ArrayRef<RecordedOrDeferredNode> &children);
+                     const ArrayRef<RecordedOrDeferredNode> &children) = 0;
 
   /// Record a deferred token node that was previously created using \c
   /// makeDeferredToken. The deferred data will never be used again, so it can
   /// be destroyed by this method. Note that not all deferred nodes will be
   /// recorded and that pending deferred nodes need to be freed when the \c
   /// SyntaxParseActions is destructed.
-  virtual OpaqueSyntaxNode recordDeferredToken(OpaqueSyntaxNode deferred);
+  virtual OpaqueSyntaxNode recordDeferredToken(OpaqueSyntaxNode deferred) = 0;
 
   /// Record a deferred layout node. See recordDeferredToken.
-  virtual OpaqueSyntaxNode recordDeferredLayout(OpaqueSyntaxNode deferred);
+  virtual OpaqueSyntaxNode recordDeferredLayout(OpaqueSyntaxNode deferred) = 0;
 
   /// Since most data of \c ParsedRawSyntax is described as opaque data, the
   /// \c ParsedRawSyntax node needs to reach out to the \c SyntaxParseAction,
@@ -140,11 +138,11 @@ class SyntaxParseActions {
   /// node starts at \p StartLoc.
   virtual DeferredNodeInfo getDeferredChild(OpaqueSyntaxNode node,
                                             size_t childIndex,
-                                            SourceLoc startLoc);
+                                            SourceLoc startLoc) = 0;
 
   /// Return the number of children, \p node has. These can be retrieved using
   /// \c getDeferredChild.
-  virtual size_t getDeferredNumChildren(OpaqueSyntaxNode node);
+  virtual size_t getDeferredNumChildren(OpaqueSyntaxNode node) = 0;
 
   /// Attempt to realize an opaque raw syntax node for a source file into a
   /// SourceFileSyntax node. This will return \c None if the parsing action

include/swift/SyntaxParse/SyntaxTreeCreator.h

@@ -33,7 +33,7 @@ class SourceFileSyntax;
 ///
 /// It also handles caching re-usable RawSyntax objects and skipping parsed
 /// nodes via consulting a \c SyntaxParsingCache.
-class SyntaxTreeCreator: public SyntaxParseActions {
+class SyntaxTreeCreator final : public SyntaxParseActions {
   SourceManager &SM;
   unsigned BufferID;
   RC<syntax::SyntaxArena> Arena;
@@ -48,6 +48,8 @@ class SyntaxTreeCreator: public SyntaxParseActions {
   /// tree.
   SyntaxParsingCache *SyntaxCache;
 
+  llvm::BumpPtrAllocator ScratchAlloc;
+
 public:
   SyntaxTreeCreator(SourceManager &SM, unsigned bufferID,
                     SyntaxParsingCache *syntaxCache,
@@ -70,6 +72,23 @@ class SyntaxTreeCreator: public SyntaxParseActions {
 
   std::pair<size_t, OpaqueSyntaxNode>
   lookupNode(size_t lexerOffset, syntax::SyntaxKind kind) override;
+
+  OpaqueSyntaxNode makeDeferredToken(tok tokenKind, StringRef leadingTrivia,
+                                     StringRef trailingTrivia,
+                                     CharSourceRange range,
+                                     bool isMissing) override;
+
+  OpaqueSyntaxNode
+  makeDeferredLayout(syntax::SyntaxKind k, bool IsMissing,
+                     const ArrayRef<RecordedOrDeferredNode> &children) override;
+
+  OpaqueSyntaxNode recordDeferredToken(OpaqueSyntaxNode deferred) override;
+  OpaqueSyntaxNode recordDeferredLayout(OpaqueSyntaxNode deferred) override;
+
+  DeferredNodeInfo getDeferredChild(OpaqueSyntaxNode node, size_t ChildIndex,
+                                    SourceLoc StartLoc) override;
+
+  size_t getDeferredNumChildren(OpaqueSyntaxNode node) override;
 };
 
 } // end namespace swift

lib/Parse/CMakeLists.txt

@@ -22,7 +22,6 @@ add_swift_host_library(swiftParse STATIC
   ParseStmt.cpp
   ParseType.cpp
   PersistentParserState.cpp
-  SyntaxParseActions.cpp
   SyntaxParsingCache.cpp
   SyntaxParsingContext.cpp)
 _swift_gyb_target_sources(swiftParse PRIVATE

lib/SyntaxParse/SyntaxTreeCreator.cpp

@@ -164,3 +164,92 @@ SyntaxTreeCreator::lookupNode(size_t lexerOffset, syntax::SyntaxKind kind) {
   size_t length = raw->getTextLength();
   return {length, static_cast<OpaqueSyntaxNode>(raw)};
 }
+
+OpaqueSyntaxNode SyntaxTreeCreator::makeDeferredToken(tok tokenKind,
+                                                      StringRef leadingTrivia,
+                                                      StringRef trailingTrivia,
+                                                      CharSourceRange range,
+                                                      bool isMissing) {
+  // Instead of creating dedicated deferred nodes that will be recorded only if
+  // needed, the SyntaxTreeCreator always records all nodes and forms RawSyntax
+  // nodes for them. This eliminates a bunch of copies that would otherwise
+  // be required to record the deferred nodes.
+  // Should a deferred node not be recorded, its data stays alive in the
+  // SyntaxArena. This causes a small memory leak but since most nodes are
+  // being recorded, it is acceptable.
+  if (isMissing) {
+    auto Node = recordMissingToken(tokenKind, range.getStart());
+    return Node;
+  } else {
+    auto Node = recordToken(tokenKind, leadingTrivia, trailingTrivia, range);
+    return Node;
+  }
+}
+
+OpaqueSyntaxNode SyntaxTreeCreator::makeDeferredLayout(
+    syntax::SyntaxKind k, bool IsMissing,
+    const ArrayRef<RecordedOrDeferredNode> &children) {
+  SmallVector<OpaqueSyntaxNode, 16> opaqueChildren;
+  opaqueChildren.reserve(children.size());
+
+  for (size_t i = 0; i < children.size(); ++i) {
+    opaqueChildren.push_back(children[i].getOpaque());
+  }
+
+  // Also see comment in makeDeferredToken
+  return recordRawSyntax(k, opaqueChildren);
+}
+
+OpaqueSyntaxNode
+SyntaxTreeCreator::recordDeferredToken(OpaqueSyntaxNode deferred) {
+  // We don't diffirentiate between deferred and recorded nodes. See comment in
+  // makeDeferredToken.
+  return deferred;
+}
+
+OpaqueSyntaxNode
+SyntaxTreeCreator::recordDeferredLayout(OpaqueSyntaxNode deferred) {
+  // We don't diffirentiate between deferred and recorded nodes. See comment in
+  // makeDeferredToken.
+  return deferred;
+}
+
+DeferredNodeInfo SyntaxTreeCreator::getDeferredChild(OpaqueSyntaxNode node,
+                                                     size_t ChildIndex,
+                                                     SourceLoc StartLoc) {
+  const RawSyntax *raw = static_cast<const RawSyntax *>(node);
+
+  // Compute the start offset of the child node by advancing StartLoc by the
+  // length of all previous child nodes.
+  for (unsigned i = 0; i < ChildIndex; ++i) {
+    const RawSyntax *child = raw->getChild(i);
+    if (child) {
+      StartLoc = StartLoc.getAdvancedLoc(child->getTextLength());
+    }
+  }
+
+  const RawSyntax *Child = raw->getChild(ChildIndex);
+  if (Child == nullptr) {
+    return DeferredNodeInfo(
+        RecordedOrDeferredNode(nullptr, RecordedOrDeferredNode::Kind::Null),
+        syntax::SyntaxKind::Unknown, tok::NUM_TOKENS, /*IsMissing=*/false,
+        CharSourceRange(StartLoc, /*Length=*/0));
+  } else if (Child->isToken()) {
+    return DeferredNodeInfo(
+        RecordedOrDeferredNode(Child,
+                               RecordedOrDeferredNode::Kind::DeferredToken),
+        syntax::SyntaxKind::Token, Child->getTokenKind(), Child->isMissing(),
+        CharSourceRange(StartLoc, Child->getTextLength()));
+  } else {
+    return DeferredNodeInfo(
+        RecordedOrDeferredNode(Child,
+                               RecordedOrDeferredNode::Kind::DeferredLayout),
+        Child->getKind(), tok::NUM_TOKENS,
+        /*IsMissing=*/false, CharSourceRange(StartLoc, Child->getTextLength()));
+  }
+}
+
+size_t SyntaxTreeCreator::getDeferredNumChildren(OpaqueSyntaxNode node) {
+  const syntax::RawSyntax *raw = static_cast<const syntax::RawSyntax *>(node);
+  return raw->getNumChildren();
+}