[clangd] Remove accessors for top-level decls from preamble

Summary:
They cause lots of deserialization and are not actually used.
The ParsedAST accessor that previously returned those was renamed from
getTopLevelDecls to getLocalTopLevelDecls in order to avoid
confusion.

This change should considerably improve the speed of findDefinition
and other features that try to find AST nodes, corresponding to the
locations in the source code.

Reviewers: ioeric, sammccall

Reviewed By: sammccall

Subscribers: klimek, mehdi_amini, MaskRay, jkorous, cfe-commits

Differential Revision: https://reviews.llvm.org/D47331

1 files changed, 8 insertions, 58 deletions

diff --git a/clang-tools-extra/clangd/ClangdUnit.cpp b/clang-tools-extra/clangd/ClangdUnit.cpp
index 105bdb1fe8e..af6a52f5523 100644
--- a/clang-tools-extra/clangd/ClangdUnit.cpp
+++ b/clang-tools-extra/clangd/ClangdUnit.cpp
@@ -90,22 +90,8 @@ public:
   CppFilePreambleCallbacks(PathRef File, PreambleParsedCallback ParsedCallback)
       : File(File), ParsedCallback(ParsedCallback) {}
 
-  std::vector<serialization::DeclID> takeTopLevelDeclIDs() {
-    return std::move(TopLevelDeclIDs);
-  }
-
   std::vector<Inclusion> takeInclusions() { return std::move(Inclusions); }
 
-  void AfterPCHEmitted(ASTWriter &Writer) override {
-    TopLevelDeclIDs.reserve(TopLevelDecls.size());
-    for (Decl *D : TopLevelDecls) {
-      // Invalid top-level decls may not have been serialized.
-      if (D->isInvalidDecl())
-        continue;
-      TopLevelDeclIDs.push_back(Writer.getDeclID(D));
-    }
-  }
-
   void AfterExecute(CompilerInstance &CI) override {
     if (!ParsedCallback)
       return;
@@ -113,14 +99,6 @@ public:
     ParsedCallback(File, CI.getASTContext(), CI.getPreprocessorPtr());
   }
 
-  void HandleTopLevelDecl(DeclGroupRef DG) override {
-    for (Decl *D : DG) {
-      if (isa<ObjCMethodDecl>(D))
-        continue;
-      TopLevelDecls.push_back(D);
-    }
-  }
-
   void BeforeExecute(CompilerInstance &CI) override {
     SourceMgr = &CI.getSourceManager();
   }
@@ -135,8 +113,6 @@ public:
 private:
   PathRef File;
   PreambleParsedCallback ParsedCallback;
-  std::vector<Decl *> TopLevelDecls;
-  std::vector<serialization::DeclID> TopLevelDeclIDs;
   std::vector<Inclusion> Inclusions;
   SourceManager *SourceMgr = nullptr;
 };
@@ -204,28 +180,6 @@ ParsedAST::Build(std::unique_ptr<clang::CompilerInvocation> CI,
                    std::move(Inclusions));
 }
 
-void ParsedAST::ensurePreambleDeclsDeserialized() {
-  if (PreambleDeclsDeserialized || !Preamble)
-    return;
-
-  std::vector<const Decl *> Resolved;
-  Resolved.reserve(Preamble->TopLevelDeclIDs.size());
-
-  ExternalASTSource &Source = *getASTContext().getExternalSource();
-  for (serialization::DeclID TopLevelDecl : Preamble->TopLevelDeclIDs) {
-    // Resolve the declaration ID to an actual declaration, possibly
-    // deserializing the declaration in the process.
-    if (Decl *D = Source.GetExternalDecl(TopLevelDecl))
-      Resolved.push_back(D);
-  }
-
-  TopLevelDecls.reserve(TopLevelDecls.size() +
-                        Preamble->TopLevelDeclIDs.size());
-  TopLevelDecls.insert(TopLevelDecls.begin(), Resolved.begin(), Resolved.end());
-
-  PreambleDeclsDeserialized = true;
-}
-
 ParsedAST::ParsedAST(ParsedAST &&Other) = default;
 
 ParsedAST &ParsedAST::operator=(ParsedAST &&Other) = default;
@@ -252,9 +206,8 @@ const Preprocessor &ParsedAST::getPreprocessor() const {
   return Clang->getPreprocessor();
 }
 
-ArrayRef<const Decl *> ParsedAST::getTopLevelDecls() {
-  ensurePreambleDeclsDeserialized();
-  return TopLevelDecls;
+ArrayRef<const Decl *> ParsedAST::getLocalTopLevelDecls() {
+  return LocalTopLevelDecls;
 }
 
 const std::vector<Diag> &ParsedAST::getDiagnostics() const { return Diags; }
@@ -264,7 +217,7 @@ std::size_t ParsedAST::getUsedBytes() const {
   // FIXME(ibiryukov): we do not account for the dynamically allocated part of
   // Message and Fixes inside each diagnostic.
   return AST.getASTAllocatedMemory() + AST.getSideTableAllocatedMemory() +
-         ::getUsedBytes(TopLevelDecls) + ::getUsedBytes(Diags);
+         ::getUsedBytes(LocalTopLevelDecls) + ::getUsedBytes(Diags);
 }
 
 const std::vector<Inclusion> &ParsedAST::getInclusions() const {
@@ -272,21 +225,19 @@ const std::vector<Inclusion> &ParsedAST::getInclusions() const {
 }
 
 PreambleData::PreambleData(PrecompiledPreamble Preamble,
-                           std::vector<serialization::DeclID> TopLevelDeclIDs,
                            std::vector<Diag> Diags,
                            std::vector<Inclusion> Inclusions)
-    : Preamble(std::move(Preamble)),
-      TopLevelDeclIDs(std::move(TopLevelDeclIDs)), Diags(std::move(Diags)),
+    : Preamble(std::move(Preamble)), Diags(std::move(Diags)),
       Inclusions(std::move(Inclusions)) {}
 
 ParsedAST::ParsedAST(std::shared_ptr<const PreambleData> Preamble,
                      std::unique_ptr<CompilerInstance> Clang,
                      std::unique_ptr<FrontendAction> Action,
-                     std::vector<const Decl *> TopLevelDecls,
+                     std::vector<const Decl *> LocalTopLevelDecls,
                      std::vector<Diag> Diags, std::vector<Inclusion> Inclusions)
     : Preamble(std::move(Preamble)), Clang(std::move(Clang)),
       Action(std::move(Action)), Diags(std::move(Diags)),
-      TopLevelDecls(std::move(TopLevelDecls)), PreambleDeclsDeserialized(false),
+      LocalTopLevelDecls(std::move(LocalTopLevelDecls)),
       Inclusions(std::move(Inclusions)) {
   assert(this->Clang);
   assert(this->Action);
@@ -431,9 +382,8 @@ CppFile::rebuildPreamble(CompilerInvocation &CI,
         " for file " + Twine(FileName));
 
     return std::make_shared<PreambleData>(
-        std::move(*BuiltPreamble),
-        SerializedDeclsCollector.takeTopLevelDeclIDs(),
-        PreambleDiagnostics.take(), SerializedDeclsCollector.takeInclusions());
+        std::move(*BuiltPreamble), PreambleDiagnostics.take(),
+        SerializedDeclsCollector.takeInclusions());
   } else {
     log("Could not build a preamble for file " + Twine(FileName));
     return nullptr;