[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, 122 insertions, 55 deletions

diff --git a/clang/lib/CodeGen/CGBlocks.cpp b/clang/lib/CodeGen/CGBlocks.cpp
index bbef9292d2c..7bd61768758 100644
--- a/clang/lib/CodeGen/CGBlocks.cpp
+++ b/clang/lib/CodeGen/CGBlocks.cpp
@@ -477,6 +477,14 @@ static void computeBlockInfo(CodeGenModule &CGM, CodeGenFunction *CGF,
       info.NeedsCopyDispose = true;
       info.HasCXXObject = true;
 
+    // So do C structs that require non-trivial copy construction or
+    // destruction.
+    } else if (variable->getType().isNonTrivialToPrimitiveCopy() ==
+                   QualType::PCK_Struct ||
+               variable->getType().isDestructedType() ==
+                   QualType::DK_nontrivial_c_struct) {
+      info.NeedsCopyDispose = true;
+
     // And so do types with destructors.
     } else if (CGM.getLangOpts().CPlusPlus) {
       if (const CXXRecordDecl *record =
@@ -1511,6 +1519,7 @@ enum class BlockCaptureEntityKind {
   CXXRecord, // Copy or destroy
   ARCWeak,
   ARCStrong,
+  NonTrivialCStruct,
   BlockObject, // Assign or release
   None
 };
@@ -1546,39 +1555,46 @@ computeCopyInfoForBlockCapture(const BlockDecl::Capture &CI, QualType T,
       Flags |= BLOCK_FIELD_IS_WEAK;
     return std::make_pair(BlockCaptureEntityKind::BlockObject, Flags);
   }
-  if (!T->isObjCRetainableType())
-    // For all other types, the memcpy is fine.
-    return std::make_pair(BlockCaptureEntityKind::None, Flags);
 
   Flags = BLOCK_FIELD_IS_OBJECT;
   bool isBlockPointer = T->isBlockPointerType();
   if (isBlockPointer)
     Flags = BLOCK_FIELD_IS_BLOCK;
 
-  // Special rules for ARC captures:
-  Qualifiers QS = T.getQualifiers();
-
-  // We need to register __weak direct captures with the runtime.
-  if (QS.getObjCLifetime() == Qualifiers::OCL_Weak)
-    return std::make_pair(BlockCaptureEntityKind::ARCWeak, Flags);
-
-  // We need to retain the copied value for __strong direct captures.
-  if (QS.getObjCLifetime() == Qualifiers::OCL_Strong) {
-    // If it's a block pointer, we have to copy the block and
-    // assign that to the destination pointer, so we might as
-    // well use _Block_object_assign.  Otherwise we can avoid that.
+  switch (T.isNonTrivialToPrimitiveCopy()) {
+  case QualType::PCK_Struct:
+    return std::make_pair(BlockCaptureEntityKind::NonTrivialCStruct,
+                          BlockFieldFlags());
+  case QualType::PCK_ARCStrong:
+    // We need to retain the copied value for __strong direct captures.
+    // If it's a block pointer, we have to copy the block and assign that to
+    // the destination pointer, so we might as well use _Block_object_assign.
+    // Otherwise we can avoid that.
     return std::make_pair(!isBlockPointer ? BlockCaptureEntityKind::ARCStrong
                                           : BlockCaptureEntityKind::BlockObject,
                           Flags);
-  }
+  case QualType::PCK_Trivial:
+  case QualType::PCK_VolatileTrivial: {
+    if (!T->isObjCRetainableType())
+      // For all other types, the memcpy is fine.
+      return std::make_pair(BlockCaptureEntityKind::None, BlockFieldFlags());
 
-  // Non-ARC captures of retainable pointers are strong and
-  // therefore require a call to _Block_object_assign.
-  if (!QS.getObjCLifetime() && !LangOpts.ObjCAutoRefCount)
-    return std::make_pair(BlockCaptureEntityKind::BlockObject, Flags);
+    // Special rules for ARC captures:
+    Qualifiers QS = T.getQualifiers();
 
-  // Otherwise the memcpy is fine.
-  return std::make_pair(BlockCaptureEntityKind::None, Flags);
+    // We need to register __weak direct captures with the runtime.
+    if (QS.getObjCLifetime() == Qualifiers::OCL_Weak)
+      return std::make_pair(BlockCaptureEntityKind::ARCWeak, Flags);
+
+    // Non-ARC captures of retainable pointers are strong and
+    // therefore require a call to _Block_object_assign.
+    if (!QS.getObjCLifetime() && !LangOpts.ObjCAutoRefCount)
+      return std::make_pair(BlockCaptureEntityKind::BlockObject, Flags);
+
+    // Otherwise the memcpy is fine.
+    return std::make_pair(BlockCaptureEntityKind::None, BlockFieldFlags());
+  }
+  }
 }
 
 /// Find the set of block captures that need to be explicitly copied or destroy.
@@ -1675,6 +1691,13 @@ CodeGenFunction::GenerateCopyHelperFunction(const CGBlockInfo &blockInfo) {
       EmitSynthesizedCXXCopyCtor(dstField, srcField, CI.getCopyExpr());
     } else if (CopiedCapture.Kind == BlockCaptureEntityKind::ARCWeak) {
       EmitARCCopyWeak(dstField, srcField);
+    // If this is a C struct that requires non-trivial copy construction, emit a
+    // call to its copy constructor.
+    } else if (CopiedCapture.Kind ==
+               BlockCaptureEntityKind::NonTrivialCStruct) {
+      QualType varType = CI.getVariable()->getType();
+      callCStructCopyConstructor(MakeAddrLValue(dstField, varType),
+                                 MakeAddrLValue(srcField, varType));
     } else {
       llvm::Value *srcValue = Builder.CreateLoad(srcField, "blockcopy.src");
       if (CopiedCapture.Kind == BlockCaptureEntityKind::ARCStrong) {
@@ -1730,50 +1753,50 @@ CodeGenFunction::GenerateCopyHelperFunction(const CGBlockInfo &blockInfo) {
   return llvm::ConstantExpr::getBitCast(Fn, VoidPtrTy);
 }
 
+static BlockFieldFlags
+getBlockFieldFlagsForObjCObjectPointer(const BlockDecl::Capture &CI,
+                                       QualType T) {
+  BlockFieldFlags Flags = BLOCK_FIELD_IS_OBJECT;
+  if (T->isBlockPointerType())
+    Flags = BLOCK_FIELD_IS_BLOCK;
+  return Flags;
+}
+
 static std::pair<BlockCaptureEntityKind, BlockFieldFlags>
 computeDestroyInfoForBlockCapture(const BlockDecl::Capture &CI, QualType T,
                                   const LangOptions &LangOpts) {
-  BlockFieldFlags Flags;
   if (CI.isByRef()) {
-    Flags = BLOCK_FIELD_IS_BYREF;
+    BlockFieldFlags Flags = BLOCK_FIELD_IS_BYREF;
     if (T.isObjCGCWeak())
       Flags |= BLOCK_FIELD_IS_WEAK;
     return std::make_pair(BlockCaptureEntityKind::BlockObject, Flags);
   }
 
-  if (const CXXRecordDecl *Record = T->getAsCXXRecordDecl()) {
-    if (Record->hasTrivialDestructor())
-      return std::make_pair(BlockCaptureEntityKind::None, BlockFieldFlags());
+  switch (T.isDestructedType()) {
+  case QualType::DK_cxx_destructor:
     return std::make_pair(BlockCaptureEntityKind::CXXRecord, BlockFieldFlags());
+  case QualType::DK_objc_strong_lifetime:
+    // Use objc_storeStrong for __strong direct captures; the
+    // dynamic tools really like it when we do this.
+    return std::make_pair(BlockCaptureEntityKind::ARCStrong,
+                          getBlockFieldFlagsForObjCObjectPointer(CI, T));
+  case QualType::DK_objc_weak_lifetime:
+    // Support __weak direct captures.
+    return std::make_pair(BlockCaptureEntityKind::ARCWeak,
+                          getBlockFieldFlagsForObjCObjectPointer(CI, T));
+  case QualType::DK_nontrivial_c_struct:
+    return std::make_pair(BlockCaptureEntityKind::NonTrivialCStruct,
+                          BlockFieldFlags());
+  case QualType::DK_none: {
+    // Non-ARC captures are strong, and we need to use _Block_object_dispose.
+    if (T->isObjCRetainableType() && !T.getQualifiers().hasObjCLifetime() &&
+        !LangOpts.ObjCAutoRefCount)
+      return std::make_pair(BlockCaptureEntityKind::BlockObject,
+                            getBlockFieldFlagsForObjCObjectPointer(CI, T));
+    // Otherwise, we have nothing to do.
+    return std::make_pair(BlockCaptureEntityKind::None, BlockFieldFlags());
+  }
   }
-
-  // Other types don't need to be destroy explicitly.
-  if (!T->isObjCRetainableType())
-    return std::make_pair(BlockCaptureEntityKind::None, Flags);
-
-  Flags = BLOCK_FIELD_IS_OBJECT;
-  if (T->isBlockPointerType())
-    Flags = BLOCK_FIELD_IS_BLOCK;
-
-  // Special rules for ARC captures.
-  Qualifiers QS = T.getQualifiers();
-
-  // Use objc_storeStrong for __strong direct captures; the
-  // dynamic tools really like it when we do this.
-  if (QS.getObjCLifetime() == Qualifiers::OCL_Strong)
-    return std::make_pair(BlockCaptureEntityKind::ARCStrong, Flags);
-
-  // Support __weak direct captures.
-  if (QS.getObjCLifetime() == Qualifiers::OCL_Weak)
-    return std::make_pair(BlockCaptureEntityKind::ARCWeak, Flags);
-
-  // Non-ARC captures are strong, and we need to use
-  // _Block_object_dispose.
-  if (!QS.hasObjCLifetime() && !LangOpts.ObjCAutoRefCount)
-    return std::make_pair(BlockCaptureEntityKind::BlockObject, Flags);
-
-  // Otherwise, we have nothing to do.
-  return std::make_pair(BlockCaptureEntityKind::None, Flags);
 }
 
 /// Generate the destroy-helper function for a block closure object:
@@ -1851,6 +1874,13 @@ CodeGenFunction::GenerateDestroyHelperFunction(const CGBlockInfo &blockInfo) {
     } else if (DestroyedCapture.Kind == BlockCaptureEntityKind::ARCStrong) {
       EmitARCDestroyStrong(srcField, ARCImpreciseLifetime);
 
+    // If this is a C struct that requires non-trivial destruction, emit a call
+    // to its destructor.
+    } else if (DestroyedCapture.Kind ==
+               BlockCaptureEntityKind::NonTrivialCStruct) {
+      QualType varType = CI.getVariable()->getType();
+      pushDestroy(varType.isDestructedType(), srcField, varType);
+
     // Otherwise we call _Block_object_dispose.  It wouldn't be too
     // hard to just emit this as a cleanup if we wanted to make sure
     // that things were done in reverse.
@@ -2018,6 +2048,36 @@ public:
     id.AddPointer(VarType.getCanonicalType().getAsOpaquePtr());
   }
 };
+
+/// Emits the copy/dispose helpers for a __block variable that is a non-trivial
+/// C struct.
+class NonTrivialCStructByrefHelpers final : public BlockByrefHelpers {
+  QualType VarType;
+
+public:
+  NonTrivialCStructByrefHelpers(CharUnits alignment, QualType type)
+    : BlockByrefHelpers(alignment), VarType(type) {}
+
+  void emitCopy(CodeGenFunction &CGF, Address destField,
+                Address srcField) override {
+    CGF.callCStructMoveConstructor(CGF.MakeAddrLValue(destField, VarType),
+                                   CGF.MakeAddrLValue(srcField, VarType));
+  }
+
+  bool needsDispose() const override {
+    return VarType.isDestructedType();
+  }
+
+  void emitDispose(CodeGenFunction &CGF, Address field) override {
+    EHScopeStack::stable_iterator cleanupDepth = CGF.EHStack.stable_begin();
+    CGF.pushDestroy(VarType.isDestructedType(), field, VarType);
+    CGF.PopCleanupBlocks(cleanupDepth);
+  }
+
+  void profileImpl(llvm::FoldingSetNodeID &id) const override {
+    id.AddPointer(VarType.getCanonicalType().getAsOpaquePtr());
+  }
+};
 } // end anonymous namespace
 
 static llvm::Constant *
@@ -2203,6 +2263,13 @@ CodeGenFunction::buildByrefHelpers(llvm::StructType &byrefType,
         CGM, byrefInfo, CXXByrefHelpers(valueAlignment, type, copyExpr));
   }
 
+  // If type is a non-trivial C struct type that is non-trivial to
+  // destructly move or destroy, build the copy and dispose helpers.
+  if (type.isNonTrivialToPrimitiveDestructiveMove() == QualType::PCK_Struct ||
+      type.isDestructedType() == QualType::DK_nontrivial_c_struct)
+    return ::buildByrefHelpers(
+        CGM, byrefInfo, NonTrivialCStructByrefHelpers(valueAlignment, type));
+
   // Otherwise, if we don't have a retainable type, there's nothing to do.
   // that the runtime does extra copies.
   if (!type->isObjCRetainableType()) return nullptr;