[ObjC] Allow declaring __strong pointer fields in structs in Objective-C

ARC mode.

Declaring __strong pointer fields in structs was not allowed in
Objective-C ARC until now because that would make the struct non-trivial
to default-initialize, copy/move, and destroy, which is not something C
was designed to do. This patch lifts that restriction.

Special functions for non-trivial C structs are synthesized that are
needed to default-initialize, copy/move, and destroy the structs and
manage the ownership of the objects the __strong pointer fields point
to. Non-trivial structs passed to functions are destructed in the callee
function.

rdar://problem/33599681

Differential Revision: https://reviews.llvm.org/D41228

llvm-svn: 326307

1 files changed, 20 insertions, 10 deletions

diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index 959df69f22e..1d346935de1 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -3432,10 +3432,15 @@ struct DestroyUnpassedArg final : EHScopeStack::Cleanup {
   QualType Ty;
 
   void Emit(CodeGenFunction &CGF, Flags flags) override {
-    const CXXDestructorDecl *Dtor = Ty->getAsCXXRecordDecl()->getDestructor();
-    assert(!Dtor->isTrivial());
-    CGF.EmitCXXDestructorCall(Dtor, Dtor_Complete, /*for vbase*/ false,
-                              /*Delegating=*/false, Addr);
+    QualType::DestructionKind DtorKind = Ty.isDestructedType();
+    if (DtorKind == QualType::DK_cxx_destructor) {
+      const CXXDestructorDecl *Dtor = Ty->getAsCXXRecordDecl()->getDestructor();
+      assert(!Dtor->isTrivial());
+      CGF.EmitCXXDestructorCall(Dtor, Dtor_Complete, /*for vbase*/ false,
+                                /*Delegating=*/false, Addr);
+    } else {
+      CGF.callCStructDestructor(CGF.MakeAddrLValue(Addr, Ty));
+    }
   }
 };
 
@@ -3485,11 +3490,16 @@ void CodeGenFunction::EmitCallArg(CallArgList &args, const Expr *E,
     else
       Slot = CreateAggTemp(type, "agg.tmp");
 
-    const CXXRecordDecl *RD = type->getAsCXXRecordDecl();
-    bool DestroyedInCallee =
-        RD && RD->hasNonTrivialDestructor() &&
-        (CGM.getCXXABI().getRecordArgABI(RD) != CGCXXABI::RAA_Default ||
-         RD->hasTrivialABIOverride());
+    bool DestroyedInCallee = true, NeedsEHCleanup = true;
+    if (const auto *RD = type->getAsCXXRecordDecl()) {
+      DestroyedInCallee =
+          RD && RD->hasNonTrivialDestructor() &&
+          (CGM.getCXXABI().getRecordArgABI(RD) != CGCXXABI::RAA_Default ||
+           RD->hasTrivialABIOverride());
+    } else {
+      NeedsEHCleanup = needsEHCleanup(type.isDestructedType());
+    }
+
     if (DestroyedInCallee)
       Slot.setExternallyDestructed();
 
@@ -3497,7 +3507,7 @@ void CodeGenFunction::EmitCallArg(CallArgList &args, const Expr *E,
     RValue RV = Slot.asRValue();
     args.add(RV, type);
 
-    if (DestroyedInCallee) {
+    if (DestroyedInCallee && NeedsEHCleanup) {
       // Create a no-op GEP between the placeholder and the cleanup so we can
       // RAUW it successfully.  It also serves as a marker of the first
       // instruction where the cleanup is active.