Implement __attribute__((objc_direct)), __attribute__((objc_direct_members))
__attribute__((objc_direct)) is an attribute on methods declaration, and
__attribute__((objc_direct_members)) on implementation, categories or
extensions.
A `direct` property specifier is added (@property(direct) type name)
These attributes / specifiers cause the method to have no associated
Objective-C metadata (for the property or the method itself), and the
calling convention to be a direct C function call.
The symbol for the method has enforced hidden visibility and such direct
calls are hence unreachable cross image. An explicit C function must be
made if so desired to wrap them.
The implicit `self` and `_cmd` arguments are preserved, however to
maintain compatibility with the usual `objc_msgSend` semantics,
3 fundamental precautions are taken:
1) for instance methods, `self` is nil-checked. On arm64 backends this
typically adds a single instruction (cbz x0, <closest-ret>) to the
codegen, for the vast majority of the cases when the return type is a
scalar.
2) for class methods, because the class may not be realized/initialized
yet, a call to `[self self]` is emitted. When the proper deployment
target is used, this is optimized to `objc_opt_self(self)`.
However, long term we might want to emit something better that the
optimizer can reason about. When inlining kicks in, these calls
aren't optimized away as the optimizer has no idea that a single call
is really necessary.
3) the calling convention for the `_cmd` argument is changed: the caller
leaves the second argument to the call undefined, and the selector is
loaded inside the body when it's referenced only.
As far as error reporting goes, the compiler refuses:
- making any overloads direct,
- making an overload of a direct method,
- implementations marked as direct when the declaration in the
interface isn't (the other way around is allowed, as the direct
attribute is inherited from the declaration),
- marking methods required for protocol conformance as direct,
- messaging an unqualified `id` with a direct method,
- forming any @selector() expression with only direct selectors.
As warnings:
- any inconsistency of direct-related calling convention when
@selector() or messaging is used,
- forming any @selector() expression with a possibly direct selector.
Lastly an `objc_direct_members` attribute is added that can decorate
`@implementation` blocks and causes methods only declared there (and in
no `@interface`) to be automatically direct. When decorating an
`@interface` then all methods and properties declared in this block are
marked direct.
Radar-ID: rdar://problem/2684889
Differential Revision: https://reviews.llvm.org/D69991
Reviewed-By: John McCall
diff --git a/clang/lib/CodeGen/CGObjCMac.cpp b/clang/lib/CodeGen/CGObjCMac.cpp
index d08a26f..775e340 100644
--- a/clang/lib/CodeGen/CGObjCMac.cpp
+++ b/clang/lib/CodeGen/CGObjCMac.cpp
@@ -874,6 +874,10 @@
/// this translation unit.
llvm::DenseMap<const ObjCMethodDecl*, llvm::Function*> MethodDefinitions;
+ /// DirectMethodDefinitions - map of direct methods which have been defined in
+ /// this translation unit.
+ llvm::DenseMap<const ObjCMethodDecl*, llvm::Function*> DirectMethodDefinitions;
+
/// PropertyNames - uniqued method variable names.
llvm::DenseMap<IdentifierInfo*, llvm::GlobalVariable*> PropertyNames;
@@ -1065,7 +1069,7 @@
CodeGen::RValue EmitMessageSend(CodeGen::CodeGenFunction &CGF,
ReturnValueSlot Return,
QualType ResultType,
- llvm::Value *Sel,
+ Selector Sel,
llvm::Value *Arg0,
QualType Arg0Ty,
bool IsSuper,
@@ -1092,6 +1096,13 @@
llvm::Function *GenerateMethod(const ObjCMethodDecl *OMD,
const ObjCContainerDecl *CD=nullptr) override;
+ llvm::Function *GenerateDirectMethod(const ObjCMethodDecl *OMD,
+ const ObjCContainerDecl *CD);
+
+ void GenerateDirectMethodPrologue(CodeGenFunction &CGF, llvm::Function *Fn,
+ const ObjCMethodDecl *OMD,
+ const ObjCContainerDecl *CD) override;
+
void GenerateProtocol(const ObjCProtocolDecl *PD) override;
/// GetOrEmitProtocol - Get the protocol object for the given
@@ -1573,9 +1584,13 @@
// base of the ivar access is a parameter to an Objective C method.
// However, because the parameters are not available in the current
// interface, we cannot perform this check.
+ //
+ // Note that for direct methods, because objc_msgSend is skipped,
+ // and that the method may be inlined, this optimization actually
+ // can't be performed.
if (const ObjCMethodDecl *MD =
dyn_cast_or_null<ObjCMethodDecl>(CGF.CurFuncDecl))
- if (MD->isInstanceMethod())
+ if (MD->isInstanceMethod() && !MD->isDirectMethod())
if (const ObjCInterfaceDecl *ID = MD->getClassInterface())
return IV->getContainingInterface()->isSuperClassOf(ID);
return false;
@@ -2103,10 +2118,9 @@
CGM.getTypes().ConvertType(CGF.getContext().getObjCClassType());
Target = CGF.Builder.CreateBitCast(Target, ClassTy);
CGF.Builder.CreateStore(Target, CGF.Builder.CreateStructGEP(ObjCSuper, 1));
- return EmitMessageSend(CGF, Return, ResultType,
- EmitSelector(CGF, Sel),
- ObjCSuper.getPointer(), ObjCTypes.SuperPtrCTy,
- true, CallArgs, Method, Class, ObjCTypes);
+ return EmitMessageSend(CGF, Return, ResultType, Sel, ObjCSuper.getPointer(),
+ ObjCTypes.SuperPtrCTy, true, CallArgs, Method, Class,
+ ObjCTypes);
}
/// Generate code for a message send expression.
@@ -2118,10 +2132,9 @@
const CallArgList &CallArgs,
const ObjCInterfaceDecl *Class,
const ObjCMethodDecl *Method) {
- return EmitMessageSend(CGF, Return, ResultType,
- EmitSelector(CGF, Sel),
- Receiver, CGF.getContext().getObjCIdType(),
- false, CallArgs, Method, Class, ObjCTypes);
+ return EmitMessageSend(CGF, Return, ResultType, Sel, Receiver,
+ CGF.getContext().getObjCIdType(), false, CallArgs,
+ Method, Class, ObjCTypes);
}
static bool isWeakLinkedClass(const ObjCInterfaceDecl *ID) {
@@ -2137,7 +2150,7 @@
CGObjCCommonMac::EmitMessageSend(CodeGen::CodeGenFunction &CGF,
ReturnValueSlot Return,
QualType ResultType,
- llvm::Value *Sel,
+ Selector Sel,
llvm::Value *Arg0,
QualType Arg0Ty,
bool IsSuper,
@@ -2145,11 +2158,24 @@
const ObjCMethodDecl *Method,
const ObjCInterfaceDecl *ClassReceiver,
const ObjCCommonTypesHelper &ObjCTypes) {
+ CodeGenTypes &Types = CGM.getTypes();
+ auto selTy = CGF.getContext().getObjCSelType();
+ llvm::Value *SelValue;
+
+ if (Method && Method->isDirectMethod()) {
+ // Direct methods will synthesize the proper `_cmd` internally,
+ // so just don't bother with setting the `_cmd` argument.
+ assert(!IsSuper);
+ SelValue = llvm::UndefValue::get(Types.ConvertType(selTy));
+ } else {
+ SelValue = GetSelector(CGF, Sel);
+ }
+
CallArgList ActualArgs;
if (!IsSuper)
Arg0 = CGF.Builder.CreateBitCast(Arg0, ObjCTypes.ObjectPtrTy);
ActualArgs.add(RValue::get(Arg0), Arg0Ty);
- ActualArgs.add(RValue::get(Sel), CGF.getContext().getObjCSelType());
+ ActualArgs.add(RValue::get(SelValue), selTy);
ActualArgs.addFrom(CallArgs);
// If we're calling a method, use the formal signature.
@@ -2190,7 +2216,9 @@
bool RequiresNullCheck = false;
llvm::FunctionCallee Fn = nullptr;
- if (CGM.ReturnSlotInterferesWithArgs(MSI.CallInfo)) {
+ if (Method && Method->isDirectMethod()) {
+ Fn = GenerateDirectMethod(Method, Method->getClassInterface());
+ } else if (CGM.ReturnSlotInterferesWithArgs(MSI.CallInfo)) {
if (ReceiverCanBeNull) RequiresNullCheck = true;
Fn = (ObjCABI == 2) ? ObjCTypes.getSendStretFn2(IsSuper)
: ObjCTypes.getSendStretFn(IsSuper);
@@ -3297,6 +3325,8 @@
values.addInt(ObjCTypes.IntTy, Properties.size());
auto propertiesArray = values.beginArray(ObjCTypes.PropertyTy);
for (auto PD : Properties) {
+ if (PD->isDirectProperty())
+ continue;
auto property = propertiesArray.beginStruct(ObjCTypes.PropertyTy);
property.add(GetPropertyName(PD->getIdentifier()));
property.add(GetPropertyTypeString(PD, Container));
@@ -3372,7 +3402,8 @@
};
SmallVector<const ObjCMethodDecl *, 16> Methods[NumMethodLists];
for (const auto *MD : OCD->methods()) {
- Methods[unsigned(MD->isClassMethod())].push_back(MD);
+ if (!MD->isDirectMethod())
+ Methods[unsigned(MD->isClassMethod())].push_back(MD);
}
Values.add(GetClassName(OCD->getName()));
@@ -3554,11 +3585,14 @@
};
SmallVector<const ObjCMethodDecl *, 16> Methods[NumMethodLists];
for (const auto *MD : ID->methods()) {
- Methods[unsigned(MD->isClassMethod())].push_back(MD);
+ if (!MD->isDirectMethod())
+ Methods[unsigned(MD->isClassMethod())].push_back(MD);
}
for (const auto *PID : ID->property_impls()) {
if (PID->getPropertyImplementation() == ObjCPropertyImplDecl::Synthesize) {
+ if (PID->getPropertyDecl()->isDirectProperty())
+ continue;
if (ObjCMethodDecl *MD = PID->getGetterMethodDecl())
if (GetMethodDefinition(MD))
Methods[InstanceMethods].push_back(MD);
@@ -3957,7 +3991,8 @@
values.addInt(ObjCTypes.IntTy, methods.size());
auto methodArray = values.beginArray(ObjCTypes.MethodTy);
for (auto MD : methods) {
- emitMethodConstant(methodArray, MD);
+ if (!MD->isDirectMethod())
+ emitMethodConstant(methodArray, MD);
}
methodArray.finishAndAddTo(values);
@@ -3968,6 +4003,34 @@
llvm::Function *CGObjCCommonMac::GenerateMethod(const ObjCMethodDecl *OMD,
const ObjCContainerDecl *CD) {
+ llvm::Function *Method;
+
+ if (OMD->isDirectMethod()) {
+ Method = GenerateDirectMethod(OMD, CD);
+ } else {
+ SmallString<256> Name;
+ GetNameForMethod(OMD, CD, Name);
+
+ CodeGenTypes &Types = CGM.getTypes();
+ llvm::FunctionType *MethodTy =
+ Types.GetFunctionType(Types.arrangeObjCMethodDeclaration(OMD));
+ Method =
+ llvm::Function::Create(MethodTy, llvm::GlobalValue::InternalLinkage,
+ Name.str(), &CGM.getModule());
+ }
+
+ MethodDefinitions.insert(std::make_pair(OMD, Method));
+
+ return Method;
+}
+
+llvm::Function *
+CGObjCCommonMac::GenerateDirectMethod(const ObjCMethodDecl *OMD,
+ const ObjCContainerDecl *CD) {
+ auto I = DirectMethodDefinitions.find(OMD);
+ if (I != DirectMethodDefinitions.end())
+ return I->second;
+
SmallString<256> Name;
GetNameForMethod(OMD, CD, Name);
@@ -3975,15 +4038,98 @@
llvm::FunctionType *MethodTy =
Types.GetFunctionType(Types.arrangeObjCMethodDeclaration(OMD));
llvm::Function *Method =
- llvm::Function::Create(MethodTy,
- llvm::GlobalValue::InternalLinkage,
- Name.str(),
- &CGM.getModule());
- MethodDefinitions.insert(std::make_pair(OMD, Method));
+ llvm::Function::Create(MethodTy, llvm::GlobalValue::ExternalLinkage,
+ Name.str(), &CGM.getModule());
+ DirectMethodDefinitions.insert(std::make_pair(OMD, Method));
return Method;
}
+void CGObjCCommonMac::GenerateDirectMethodPrologue(
+ CodeGenFunction &CGF, llvm::Function *Fn, const ObjCMethodDecl *OMD,
+ const ObjCContainerDecl *CD) {
+ auto &Builder = CGF.Builder;
+ bool ReceiverCanBeNull = true;
+ auto selfAddr = CGF.GetAddrOfLocalVar(OMD->getSelfDecl());
+ auto selfValue = Builder.CreateLoad(selfAddr);
+
+ // Generate:
+ //
+ // /* for class methods only to force class lazy initialization */
+ // self = [self self];
+ //
+ // /* unless the receiver is never NULL */
+ // if (self == nil) {
+ // return (ReturnType){ };
+ // }
+ //
+ // _cmd = @selector(...)
+ // ...
+
+ if (OMD->isClassMethod()) {
+ const ObjCInterfaceDecl *OID = cast<ObjCInterfaceDecl>(CD);
+ assert(OID &&
+ "GenerateDirectMethod() should be called with the Class Interface");
+ Selector SelfSel = GetNullarySelector("self", CGM.getContext());
+ auto ResultType = CGF.getContext().getObjCIdType();
+ RValue result;
+ CallArgList Args;
+
+ // TODO: If this method is inlined, the caller might know that `self` is
+ // already initialized; for example, it might be an ordinary Objective-C
+ // method which always receives an initialized `self`, or it might have just
+ // forced initialization on its own.
+ //
+ // We should find a way to eliminate this unnecessary initialization in such
+ // cases in LLVM.
+ result = GeneratePossiblySpecializedMessageSend(
+ CGF, ReturnValueSlot(), ResultType, SelfSel, selfValue, Args, OID,
+ nullptr, true);
+ Builder.CreateStore(result.getScalarVal(), selfAddr);
+
+ // Nullable `Class` expressions cannot be messaged with a direct method
+ // so the only reason why the receive can be null would be because
+ // of weak linking.
+ ReceiverCanBeNull = isWeakLinkedClass(OID);
+ }
+
+ if (ReceiverCanBeNull) {
+ llvm::BasicBlock *SelfIsNilBlock =
+ CGF.createBasicBlock("objc_direct_method.self_is_nil");
+ llvm::BasicBlock *ContBlock =
+ CGF.createBasicBlock("objc_direct_method.cont");
+
+ // if (self == nil) {
+ auto selfTy = cast<llvm::PointerType>(selfValue->getType());
+ auto Zero = llvm::ConstantPointerNull::get(selfTy);
+
+ llvm::MDBuilder MDHelper(CGM.getLLVMContext());
+ Builder.CreateCondBr(Builder.CreateICmpEQ(selfValue, Zero), SelfIsNilBlock,
+ ContBlock, MDHelper.createBranchWeights(1, 1 << 20));
+
+ CGF.EmitBlock(SelfIsNilBlock);
+
+ // return (ReturnType){ };
+ auto retTy = OMD->getReturnType();
+ Builder.SetInsertPoint(SelfIsNilBlock);
+ if (!retTy->isVoidType()) {
+ CGF.EmitNullInitialization(CGF.ReturnValue, retTy);
+ }
+ CGF.EmitBranchThroughCleanup(CGF.ReturnBlock);
+ // }
+
+ // rest of the body
+ CGF.EmitBlock(ContBlock);
+ Builder.SetInsertPoint(ContBlock);
+ }
+
+ // only synthesize _cmd if it's referenced
+ if (OMD->getCmdDecl()->isUsed()) {
+ Builder.CreateStore(GetSelector(CGF, OMD),
+ CGF.GetAddrOfLocalVar(OMD->getCmdDecl()));
+ }
+}
+
llvm::GlobalVariable *CGObjCCommonMac::CreateMetadataVar(Twine Name,
ConstantStructBuilder &Init,
StringRef Section,
@@ -6226,10 +6372,12 @@
SmallVector<const ObjCMethodDecl*, 16> methods;
if (flags & NonFragileABI_Class_Meta) {
for (const auto *MD : ID->class_methods())
- methods.push_back(MD);
+ if (!MD->isDirectMethod())
+ methods.push_back(MD);
} else {
for (const auto *MD : ID->instance_methods())
- methods.push_back(MD);
+ if (!MD->isDirectMethod())
+ methods.push_back(MD);
}
values.add(emitMethodList(ID->getObjCRuntimeNameAsString(),
@@ -6550,6 +6698,8 @@
SmallVector<const ObjCMethodDecl *, 16> instanceMethods;
SmallVector<const ObjCMethodDecl *, 8> classMethods;
for (const auto *MD : OCD->methods()) {
+ if (MD->isDirectMethod())
+ continue;
if (MD->isInstanceMethod()) {
instanceMethods.push_back(MD);
} else {
@@ -7218,8 +7368,7 @@
? EmitVTableMessageSend(CGF, Return, ResultType, Sel,
Receiver, CGF.getContext().getObjCIdType(),
false, CallArgs, Method)
- : EmitMessageSend(CGF, Return, ResultType,
- EmitSelector(CGF, Sel),
+ : EmitMessageSend(CGF, Return, ResultType, Sel,
Receiver, CGF.getContext().getObjCIdType(),
false, CallArgs, Method, Class, ObjCTypes);
}
@@ -7450,8 +7599,7 @@
? EmitVTableMessageSend(CGF, Return, ResultType, Sel,
ObjCSuper.getPointer(), ObjCTypes.SuperPtrCTy,
true, CallArgs, Method)
- : EmitMessageSend(CGF, Return, ResultType,
- EmitSelector(CGF, Sel),
+ : EmitMessageSend(CGF, Return, ResultType, Sel,
ObjCSuper.getPointer(), ObjCTypes.SuperPtrCTy,
true, CallArgs, Method, Class, ObjCTypes);
}