Modular Codegen: Add/use a bit in serialized function definitions to track whether they are the subject of modular codegen

Some decls are created not where they are written, but in other module
files/users (implicit special members and function template implicit
specializations). To correctly identify them, use a bit next to the definition
to track the modular codegen property.

Discussed whether the module file bit could be omitted in favor of
reconstituting from the modular codegen decls list - best guess today is that
the efficiency improvement of not having to deserialize the whole list whenever
any function is queried by a module user is worth it for the small size
increase of this redundant (list + bit-on-def) representation.

Reviewers: rsmith

Differential Revision: https://reviews.llvm.org/D29901

llvm-svn: 299982

1 files changed, 8 insertions, 6 deletions

diff --git a/clang/lib/Serialization/ASTWriterDecl.cpp b/clang/lib/Serialization/ASTWriterDecl.cpp
index 41b9a97c78f..8196c8d02cd 100644
--- a/clang/lib/Serialization/ASTWriterDecl.cpp
+++ b/clang/lib/Serialization/ASTWriterDecl.cpp
@@ -2159,7 +2159,7 @@ void ASTWriter::WriteDeclAbbrevs() {
 /// relatively painless since they would presumably only do it for top-level
 /// decls.
 static bool isRequiredDecl(const Decl *D, ASTContext &Context,
-                           bool WritingModule, bool ModularCode) {
+                           bool WritingModule) {
   // An ObjCMethodDecl is never considered as "required" because its
   // implementation container always is.
 
@@ -2175,7 +2175,7 @@ static bool isRequiredDecl(const Decl *D, ASTContext &Context,
     return false;
   }
 
-  return Context.DeclMustBeEmitted(D, ModularCode);
+  return Context.DeclMustBeEmitted(D);
 }
 
 void ASTWriter::WriteDecl(ASTContext &Context, Decl *D) {
@@ -2219,11 +2219,8 @@ void ASTWriter::WriteDecl(ASTContext &Context, Decl *D) {
 
   // Note declarations that should be deserialized eagerly so that we can add
   // them to a record in the AST file later.
-  if (isRequiredDecl(D, Context, WritingModule, false))
+  if (isRequiredDecl(D, Context, WritingModule))
     EagerlyDeserializedDecls.push_back(ID);
-  else if (Context.getLangOpts().ModularCodegen && WritingModule &&
-           isRequiredDecl(D, Context, true, true))
-    ModularCodegenDecls.push_back(ID);
 }
 
 void ASTRecordWriter::AddFunctionDefinition(const FunctionDecl *FD) {
@@ -2231,6 +2228,11 @@ void ASTRecordWriter::AddFunctionDefinition(const FunctionDecl *FD) {
   Writer->ClearSwitchCaseIDs();
 
   assert(FD->doesThisDeclarationHaveABody());
+  bool ModularCodegen = Writer->Context->getLangOpts().ModularCodegen &&
+                        Writer->WritingModule && !FD->isDependentContext();
+  Record->push_back(ModularCodegen);
+  if (ModularCodegen)
+    Writer->ModularCodegenDecls.push_back(Writer->GetDeclRef(FD));
   if (auto *CD = dyn_cast<CXXConstructorDecl>(FD)) {
     Record->push_back(CD->getNumCtorInitializers());
     if (CD->getNumCtorInitializers())