address review comments

Author: hnrklssn

clang/include/clang/AST/ExternalASTSource.h

@@ -434,6 +434,17 @@ struct LazyOffsetPtr {
     return GetPtr();
   }
 
+  /// Retrieve the pointer to the AST node that this lazy pointer points to,
+  /// if it can be done without triggering deserialization.
+  ///
+  /// \returns a pointer to the AST node, or null if not yet deserialized.
+  T *getWithoutDeserializing() const {
+    if (isOffset()) {
+      return nullptr;
+    }
+    return GetPtr();
+  }
+
   /// Retrieve the address of the AST node pointer. Deserializes the pointee if
   /// necessary.
   T **getAddressOfPointer(ExternalASTSource *Source) const {

clang/include/clang/Sema/MultiplexExternalSemaSource.h

@@ -94,6 +94,8 @@ class MultiplexExternalSemaSource : public ExternalSemaSource {
 
   bool wasThisDeclarationADefinition(const FunctionDecl *FD) override;
 
+  bool hasInitializerWithSideEffects(const VarDecl *VD) const override;
+
   /// Find all declarations with the given name in the
   /// given context.
   bool FindExternalVisibleDeclsByName(const DeclContext *DC,

clang/include/clang/Serialization/ASTReader.h

@@ -1444,6 +1444,8 @@ class ASTReader
 
   /// VarDecls with initializers containing side effects must be emitted,
   /// but DeclMustBeEmitted is not allowed to deserialize the intializer.
+  /// FIXME: Lower memory usage by removing VarDecls once the initializer
+  /// is deserialized.
   llvm::SmallPtrSet<Decl *, 16> InitSideEffectVars;
 
 public:

clang/lib/AST/Decl.cpp

@@ -2443,9 +2443,7 @@ bool VarDecl::hasInitWithSideEffects() const {
   if (auto *S = dyn_cast<Stmt *>(Init)) {
     E = cast<Expr>(S);
   } else {
-    auto *Eval = getEvaluatedStmt();
-    if (!Eval->Value.isOffset())
-      E = cast<Expr>(Eval->Value.get(nullptr));
+    E = cast_or_null<Expr>(getEvaluatedStmt()->Value.getWithoutDeserializing());
   }
 
   if (E)
@@ -2455,8 +2453,9 @@ bool VarDecl::hasInitWithSideEffects() const {
 
   assert(getEvaluatedStmt()->Value.isOffset());
   // ASTReader tracks this without having to deserialize the initializer
-  return getASTContext().getExternalSource()->hasInitializerWithSideEffects(
-      this);
+  if (auto Source = getASTContext().getExternalSource())
+    return Source->hasInitializerWithSideEffects(this);
+  return false;
 }
 
 bool VarDecl::isOutOfLine() const {

clang/lib/Sema/MultiplexExternalSemaSource.cpp

@@ -115,6 +115,14 @@ bool MultiplexExternalSemaSource::wasThisDeclarationADefinition(
   return false;
 }
 
+bool MultiplexExternalSemaSource::hasInitializerWithSideEffects(
+    const VarDecl *VD) const {
+  for (const auto &S : Sources)
+    if (S->hasInitializerWithSideEffects(VD))
+      return true;
+  return false;
+}
+
 bool MultiplexExternalSemaSource::FindExternalVisibleDeclsByName(
     const DeclContext *DC, DeclarationName Name,
     const DeclContext *OriginalDC) {

clang/lib/Serialization/ASTReaderDecl.cpp

@@ -1632,8 +1632,7 @@ RedeclarableResult ASTDeclReader::VisitVarDeclImpl(VarDecl *VD) {
     VD->NonParmVarDeclBits.PreviousDeclInSameBlockScope =
         VarDeclBits.getNextBit();
 
-    bool HasInitWithSideEffect = VarDeclBits.getNextBit();
-    if (HasInitWithSideEffect)
+    if (VarDeclBits.getNextBit())
       Reader.InitSideEffectVars.insert(VD);
 
     VD->NonParmVarDeclBits.EscapingByref = VarDeclBits.getNextBit();