feat(classes): destroy stack objects at scope exit

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 77 insertions, 0 deletions

diff --git a/lib/CodeGen/ConstructorGen.cc b/lib/CodeGen/ConstructorGen.cc
index 9e6b0b3..c0e50ac 100644
--- a/lib/CodeGen/ConstructorGen.cc
+++ b/lib/CodeGen/ConstructorGen.cc
@@ -107,3 +107,80 @@ bool CodeGen::emitDestroy(const std::string &TypeName, Value *Addr, int Line) {
     }
     return true;
 }
+
+size_t CodeGen::registerStackObject(Value *Addr, const std::string &TypeName, int Line,
+                                     bool IsArray, bool IsCopy) {
+    if (!typeNeedsDestruction(TypeName)) return size_t(-1);
+    auto *F = Builder->GetInsertBlock()->getParent();
+    IRBuilder<> Entry(&F->getEntryBlock(), F->getEntryBlock().begin());
+    auto *Alive = Entry.CreateAlloca(Entry.getInt1Ty(), nullptr, "object_alive");
+    Entry.CreateStore(Entry.getFalse(), Alive);
+    AllocaInst *Count = nullptr;
+    if (IsArray) {
+        Count = Entry.CreateAlloca(Entry.getInt64Ty(), nullptr, "object_count");
+        Entry.CreateStore(Entry.getInt64(0), Count);
+    }
+    StackObjects.push_back({Addr, TypeName, Alive, Count, Line, IsCopy});
+    // This DECLARE can execute repeatedly, including after a backward loop edge.
+    emitStackObjectCleanup(StackObjects.back());
+    return StackObjects.size() - 1;
+}
+
+void CodeGen::activateStackObject(size_t Index, Value *Count) {
+    if (Index == size_t(-1)) return;
+    const auto &Object = StackObjects[Index];
+    if (Object.Count) Builder->CreateStore(Count, Object.Count);
+    Builder->CreateStore(Builder->getTrue(), Object.Alive);
+}
+
+void CodeGen::emitStackObjectCleanup(const StackObject &Object) {
+    auto *F = Builder->GetInsertBlock()->getParent();
+    auto *Destroy = BasicBlock::Create(*TheContext, "destroy_object", F);
+    auto *Done = BasicBlock::Create(*TheContext, "destroyed_object", F);
+    Builder->CreateCondBr(Builder->CreateLoad(Builder->getInt1Ty(), Object.Alive), Destroy, Done);
+    Builder->SetInsertPoint(Destroy);
+    // Clear before the user method: a throwing destructor must never run twice.
+    Builder->CreateStore(Builder->getFalse(), Object.Alive);
+    if (!Object.Count) {
+        emitDestroy(Object.TypeName, Object.Addr, Object.Line);
+    } else {
+        Value *Base = Builder->CreateLoad(PointerType::getUnqual(*TheContext), Object.Addr);
+        Value *Count = Builder->CreateLoad(Builder->getInt64Ty(), Object.Count);
+        auto *Preheader = Builder->GetInsertBlock();
+        auto *Loop = BasicBlock::Create(*TheContext, "destroy_elements", F);
+        auto *Body = BasicBlock::Create(*TheContext, "destroy_element", F);
+        Builder->CreateBr(Loop);
+        Builder->SetInsertPoint(Loop);
+        auto *Index = Builder->CreatePHI(Builder->getInt64Ty(), 2);
+        Index->addIncoming(Count, Preheader);
+        Builder->CreateCondBr(Builder->CreateICmpNE(Index, Builder->getInt64(0)), Body, Done);
+        Builder->SetInsertPoint(Body);
+        Value *Previous = Builder->CreateSub(Index, Builder->getInt64(1));
+        Value *Element = Builder->CreateGEP(resolveType(Object.TypeName)->LLVMType, Base, Previous);
+        emitDestroy(Object.TypeName, Element, Object.Line);
+        Index->addIncoming(Previous, Builder->GetInsertBlock());
+        Builder->CreateBr(Loop);
+        Builder->SetInsertPoint(Done);
+        return;
+    }
+    Builder->CreateBr(Done);
+    Builder->SetInsertPoint(Done);
+}
+
+void CodeGen::finishStackObjects(Function *F) {
+    IRBuilderBase::InsertPointGuard Guard(*Builder);
+    std::vector<Instruction *> Exits;
+    for (auto &BB : *F)
+        if (BB.hasTerminator() && isa<ReturnInst>(BB.getTerminator()))
+            Exits.push_back(BB.getTerminator());
+    for (auto *Exit : Exits) {
+        // Keep the original terminator in a continuation while cleanup builds branches.
+        auto *BB = Exit->getParent();
+        auto *Continuation = BB->splitBasicBlock(Exit->getIterator(), "after_destruction");
+        BB->getTerminator()->eraseFromParent();
+        Builder->SetInsertPoint(BB);
+        for (auto It = StackObjects.rbegin(); It != StackObjects.rend(); ++It)
+            emitStackObjectCleanup(*It);
+        Builder->CreateBr(Continuation);
+    }
+}