//===----------------------------------------------------------------------===// // // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. // See https://llvm.org/LICENSE.txt for license information. // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception // //===----------------------------------------------------------------------===// // // This contains code dealing with C++ code generation of classes // //===----------------------------------------------------------------------===// #include "CIRGenCXXABI.h" #include "CIRGenFunction.h" #include "CIRGenValue.h" #include "clang/AST/ExprCXX.h" #include "clang/AST/RecordLayout.h" #include "clang/AST/Type.h" #include "clang/CIR/MissingFeatures.h" using namespace clang; using namespace clang::CIRGen; /// Checks whether the given constructor is a valid subject for the /// complete-to-base constructor delegation optimization, i.e. emitting the /// complete constructor as a simple call to the base constructor. bool CIRGenFunction::isConstructorDelegationValid( const CXXConstructorDecl *ctor) { // Currently we disable the optimization for classes with virtual bases // because (1) the address of parameter variables need to be consistent across // all initializers but (2) the delegate function call necessarily creates a // second copy of the parameter variable. // // The limiting example (purely theoretical AFAIK): // struct A { A(int &c) { c++; } }; // struct A : virtual A { // B(int count) : A(count) { printf("%d\n", count); } // }; // ...although even this example could in principle be emitted as a delegation // since the address of the parameter doesn't escape. if (ctor->getParent()->getNumVBases()) return false; // We also disable the optimization for variadic functions because it's // impossible to "re-pass" varargs. if (ctor->getType()->castAs()->isVariadic()) return false; // FIXME: Decide if we can do a delegation of a delegating constructor. if (ctor->isDelegatingConstructor()) return false; return true; } static void emitLValueForAnyFieldInitialization(CIRGenFunction &cgf, CXXCtorInitializer *memberInit, LValue &lhs) { FieldDecl *field = memberInit->getAnyMember(); if (memberInit->isIndirectMemberInitializer()) { // If we are initializing an anonymous union field, drill down to the field. IndirectFieldDecl *indirectField = memberInit->getIndirectMember(); for (const auto *nd : indirectField->chain()) { auto *fd = cast(nd); lhs = cgf.emitLValueForFieldInitialization(lhs, fd, fd->getName()); } } else { lhs = cgf.emitLValueForFieldInitialization(lhs, field, field->getName()); } } static void emitMemberInitializer(CIRGenFunction &cgf, const CXXRecordDecl *classDecl, CXXCtorInitializer *memberInit, const CXXConstructorDecl *constructor, FunctionArgList &args) { assert(memberInit->isAnyMemberInitializer() && "Must have member initializer!"); assert(memberInit->getInit() && "Must have initializer!"); assert(!cir::MissingFeatures::generateDebugInfo()); // non-static data member initializers FieldDecl *field = memberInit->getAnyMember(); QualType fieldType = field->getType(); mlir::Value thisPtr = cgf.loadCXXThis(); QualType recordTy = cgf.getContext().getTypeDeclType(classDecl); // If a base constructor is being emitted, create an LValue that has the // non-virtual alignment. LValue lhs = (cgf.curGD.getCtorType() == Ctor_Base) ? cgf.makeNaturalAlignPointeeAddrLValue(thisPtr, recordTy) : cgf.makeNaturalAlignAddrLValue(thisPtr, recordTy); emitLValueForAnyFieldInitialization(cgf, memberInit, lhs); // Special case: If we are in a copy or move constructor, and we are copying // an array off PODs or classes with trivial copy constructors, ignore the AST // and perform the copy we know is equivalent. // FIXME: This is hacky at best... if we had a bit more explicit information // in the AST, we could generalize it more easily. const ConstantArrayType *array = cgf.getContext().getAsConstantArrayType(fieldType); if (array && constructor->isDefaulted() && constructor->isCopyOrMoveConstructor()) { QualType baseElementTy = cgf.getContext().getBaseElementType(array); // NOTE(cir): CodeGen allows record types to be memcpy'd if applicable, // whereas ClangIR wants to represent all object construction explicitly. if (!baseElementTy->isRecordType()) { cgf.cgm.errorNYI(memberInit->getSourceRange(), "emitMemberInitializer: array of non-record type"); return; } } cgf.emitInitializerForField(field, lhs, memberInit->getInit()); } static bool isInitializerOfDynamicClass(const CXXCtorInitializer *baseInit) { const Type *baseType = baseInit->getBaseClass(); const auto *baseClassDecl = cast(baseType->castAs()->getDecl()); return baseClassDecl->isDynamicClass(); } /// Gets the address of a direct base class within a complete object. /// This should only be used for (1) non-virtual bases or (2) virtual bases /// when the type is known to be complete (e.g. in complete destructors). /// /// The object pointed to by 'thisAddr' is assumed to be non-null. Address CIRGenFunction::getAddressOfDirectBaseInCompleteClass( mlir::Location loc, Address thisAddr, const CXXRecordDecl *derived, const CXXRecordDecl *base, bool baseIsVirtual) { // 'thisAddr' must be a pointer (in some address space) to Derived. assert(thisAddr.getElementType() == convertType(derived)); // Compute the offset of the virtual base. CharUnits offset; const ASTRecordLayout &layout = getContext().getASTRecordLayout(derived); if (baseIsVirtual) offset = layout.getVBaseClassOffset(base); else offset = layout.getBaseClassOffset(base); return builder.createBaseClassAddr(loc, thisAddr, convertType(base), offset.getQuantity(), /*assumeNotNull=*/true); } void CIRGenFunction::emitBaseInitializer(mlir::Location loc, const CXXRecordDecl *classDecl, CXXCtorInitializer *baseInit) { assert(curFuncDecl && "loading 'this' without a func declaration?"); assert(isa(curFuncDecl)); assert(baseInit->isBaseInitializer() && "Must have base initializer!"); Address thisPtr = loadCXXThisAddress(); const Type *baseType = baseInit->getBaseClass(); const auto *baseClassDecl = cast(baseType->castAs()->getDecl()); bool isBaseVirtual = baseInit->isBaseVirtual(); // If the initializer for the base (other than the constructor // itself) accesses 'this' in any way, we need to initialize the // vtables. if (classDecl->isDynamicClass()) { cgm.errorNYI(loc, "emitBaseInitializer: dynamic class"); return; } // We can pretend to be a complete class because it only matters for // virtual bases, and we only do virtual bases for complete ctors. Address v = getAddressOfDirectBaseInCompleteClass( loc, thisPtr, classDecl, baseClassDecl, isBaseVirtual); assert(!cir::MissingFeatures::aggValueSlotGC()); AggValueSlot aggSlot = AggValueSlot::forAddr( v, Qualifiers(), AggValueSlot::IsDestructed, AggValueSlot::IsNotAliased, getOverlapForBaseInit(classDecl, baseClassDecl, isBaseVirtual)); emitAggExpr(baseInit->getInit(), aggSlot); assert(!cir::MissingFeatures::requiresCleanups()); } /// This routine generates necessary code to initialize base classes and /// non-static data members belonging to this constructor. void CIRGenFunction::emitCtorPrologue(const CXXConstructorDecl *cd, CXXCtorType ctorType, FunctionArgList &args) { if (cd->isDelegatingConstructor()) { emitDelegatingCXXConstructorCall(cd, args); return; } // If there are no member initializers, we can just return. if (cd->getNumCtorInitializers() == 0) return; const CXXRecordDecl *classDecl = cd->getParent(); // This code doesn't use range-based iteration because we may need to emit // code between the virtual base initializers and the non-virtual base or // between the non-virtual base initializers and the member initializers. CXXConstructorDecl::init_const_iterator b = cd->init_begin(), e = cd->init_end(); // Virtual base initializers first, if any. They aren't needed if: // - This is a base ctor variant // - There are no vbases // - The class is abstract, so a complete object of it cannot be constructed // // The check for an abstract class is necessary because sema may not have // marked virtual base destructors referenced. bool constructVBases = ctorType != Ctor_Base && classDecl->getNumVBases() != 0 && !classDecl->isAbstract(); if (constructVBases) { cgm.errorNYI(cd->getSourceRange(), "emitCtorPrologue: virtual base"); return; } const mlir::Value oldThisValue = cxxThisValue; if (!constructVBases && (*b)->isBaseInitializer() && (*b)->isBaseVirtual()) { cgm.errorNYI(cd->getSourceRange(), "emitCtorPrologue: virtual base initializer"); return; } // Handle non-virtual base initializers. for (; b != e && (*b)->isBaseInitializer(); b++) { assert(!(*b)->isBaseVirtual()); if (cgm.getCodeGenOpts().StrictVTablePointers && cgm.getCodeGenOpts().OptimizationLevel > 0 && isInitializerOfDynamicClass(*b)) { cgm.errorNYI(cd->getSourceRange(), "emitCtorPrologue: strict vtable pointers"); return; } emitBaseInitializer(getLoc(cd->getBeginLoc()), classDecl, *b); } cxxThisValue = oldThisValue; if (classDecl->isDynamicClass()) { cgm.errorNYI(cd->getSourceRange(), "emitCtorPrologue: initialize vtable pointers"); return; } // Finally, initialize class members. FieldConstructionScope fcs(*this, loadCXXThisAddress()); // Classic codegen uses a special class to attempt to replace member // initializers with memcpy. We could possibly defer that to the // lowering or optimization phases to keep the memory accesses more // explicit. For now, we don't insert memcpy at all. assert(!cir::MissingFeatures::ctorMemcpyizer()); for (; b != e; b++) { CXXCtorInitializer *member = (*b); assert(!member->isBaseInitializer()); assert(member->isAnyMemberInitializer() && "Delegating initializer on non-delegating constructor"); emitMemberInitializer(*this, cd->getParent(), member, cd, args); } } Address CIRGenFunction::loadCXXThisAddress() { assert(curFuncDecl && "loading 'this' without a func declaration?"); assert(isa(curFuncDecl)); // Lazily compute CXXThisAlignment. if (cxxThisAlignment.isZero()) { // Just use the best known alignment for the parent. // TODO: if we're currently emitting a complete-object ctor/dtor, we can // always use the complete-object alignment. auto rd = cast(curFuncDecl)->getParent(); cxxThisAlignment = cgm.getClassPointerAlignment(rd); } return Address(loadCXXThis(), cxxThisAlignment); } void CIRGenFunction::emitInitializerForField(FieldDecl *field, LValue lhs, Expr *init) { QualType fieldType = field->getType(); switch (getEvaluationKind(fieldType)) { case cir::TEK_Scalar: if (lhs.isSimple()) emitExprAsInit(init, field, lhs, false); else cgm.errorNYI(field->getSourceRange(), "emitInitializerForField: non-simple scalar"); break; case cir::TEK_Complex: cgm.errorNYI(field->getSourceRange(), "emitInitializerForField: complex"); break; case cir::TEK_Aggregate: { cgm.errorNYI(field->getSourceRange(), "emitInitializerForField: aggregate"); break; } } // Ensure that we destroy this object if an exception is thrown later in the // constructor. QualType::DestructionKind dtorKind = fieldType.isDestructedType(); (void)dtorKind; assert(!cir::MissingFeatures::requiresCleanups()); } /// Emit a loop to call a particular constructor for each of several members /// of an array. /// /// \param ctor the constructor to call for each element /// \param arrayType the type of the array to initialize /// \param arrayBegin an arrayType* /// \param zeroInitialize true if each element should be /// zero-initialized before it is constructed void CIRGenFunction::emitCXXAggrConstructorCall( const CXXConstructorDecl *ctor, const clang::ArrayType *arrayType, Address arrayBegin, const CXXConstructExpr *e, bool newPointerIsChecked, bool zeroInitialize) { QualType elementType; mlir::Value numElements = emitArrayLength(arrayType, elementType, arrayBegin); emitCXXAggrConstructorCall(ctor, numElements, arrayBegin, e, newPointerIsChecked, zeroInitialize); } /// Emit a loop to call a particular constructor for each of several members /// of an array. /// /// \param ctor the constructor to call for each element /// \param numElements the number of elements in the array; /// may be zero /// \param arrayBase a T*, where T is the type constructed by ctor /// \param zeroInitialize true if each element should be /// zero-initialized before it is constructed void CIRGenFunction::emitCXXAggrConstructorCall( const CXXConstructorDecl *ctor, mlir::Value numElements, Address arrayBase, const CXXConstructExpr *e, bool newPointerIsChecked, bool zeroInitialize) { // It's legal for numElements to be zero. This can happen both // dynamically, because x can be zero in 'new A[x]', and statically, // because of GCC extensions that permit zero-length arrays. There // are probably legitimate places where we could assume that this // doesn't happen, but it's not clear that it's worth it. // Optimize for a constant count. auto constantCount = dyn_cast(numElements.getDefiningOp()); if (constantCount) { auto constIntAttr = mlir::dyn_cast(constantCount.getValue()); // Just skip out if the constant count is zero. if (constIntAttr && constIntAttr.getUInt() == 0) return; } else { // Otherwise, emit the check. cgm.errorNYI(e->getSourceRange(), "dynamic-length array expression"); } auto arrayTy = mlir::cast(arrayBase.getElementType()); mlir::Type elementType = arrayTy.getElementType(); cir::PointerType ptrToElmType = builder.getPointerTo(elementType); // Tradional LLVM codegen emits a loop here. CIR lowers to a loop as part of // LoweringPrepare. // The alignment of the base, adjusted by the size of a single element, // provides a conservative estimate of the alignment of every element. // (This assumes we never start tracking offsetted alignments.) // // Note that these are complete objects and so we don't need to // use the non-virtual size or alignment. QualType type = getContext().getTypeDeclType(ctor->getParent()); CharUnits eltAlignment = arrayBase.getAlignment().alignmentOfArrayElement( getContext().getTypeSizeInChars(type)); // Zero initialize the storage, if requested. if (zeroInitialize) emitNullInitialization(*currSrcLoc, arrayBase, type); // C++ [class.temporary]p4: // There are two contexts in which temporaries are destroyed at a different // point than the end of the full-expression. The first context is when a // default constructor is called to initialize an element of an array. // If the constructor has one or more default arguments, the destruction of // every temporary created in a default argument expression is sequenced // before the construction of the next array element, if any. { assert(!cir::MissingFeatures::runCleanupsScope()); // Evaluate the constructor and its arguments in a regular // partial-destroy cleanup. if (getLangOpts().Exceptions && !ctor->getParent()->hasTrivialDestructor()) { cgm.errorNYI(e->getSourceRange(), "partial array cleanups"); } // Emit the constructor call that will execute for every array element. mlir::Value arrayOp = builder.createPtrBitcast(arrayBase.getPointer(), arrayTy); builder.create( *currSrcLoc, arrayOp, [&](mlir::OpBuilder &b, mlir::Location loc) { mlir::BlockArgument arg = b.getInsertionBlock()->addArgument(ptrToElmType, loc); Address curAddr = Address(arg, elementType, eltAlignment); assert(!cir::MissingFeatures::sanitizers()); auto currAVS = AggValueSlot::forAddr( curAddr, type.getQualifiers(), AggValueSlot::IsDestructed, AggValueSlot::IsNotAliased, AggValueSlot::DoesNotOverlap, AggValueSlot::IsNotZeroed); emitCXXConstructorCall(ctor, Ctor_Complete, /*ForVirtualBase=*/false, /*Delegating=*/false, currAVS, e); builder.create(loc); }); } if (constantCount.use_empty()) constantCount.erase(); } void CIRGenFunction::emitDelegateCXXConstructorCall( const CXXConstructorDecl *ctor, CXXCtorType ctorType, const FunctionArgList &args, SourceLocation loc) { CallArgList delegateArgs; FunctionArgList::const_iterator i = args.begin(), e = args.end(); assert(i != e && "no parameters to constructor"); // this Address thisAddr = loadCXXThisAddress(); delegateArgs.add(RValue::get(thisAddr.getPointer()), (*i)->getType()); ++i; // FIXME: The location of the VTT parameter in the parameter list is specific // to the Itanium ABI and shouldn't be hardcoded here. if (cgm.getCXXABI().needsVTTParameter(curGD)) { cgm.errorNYI(loc, "emitDelegateCXXConstructorCall: VTT parameter"); return; } // Explicit arguments. for (; i != e; ++i) { const VarDecl *param = *i; // FIXME: per-argument source location emitDelegateCallArg(delegateArgs, param, loc); } assert(!cir::MissingFeatures::sanitizers()); emitCXXConstructorCall(ctor, ctorType, /*ForVirtualBase=*/false, /*Delegating=*/true, thisAddr, delegateArgs, loc); } void CIRGenFunction::emitImplicitAssignmentOperatorBody(FunctionArgList &args) { const auto *assignOp = cast(curGD.getDecl()); assert(assignOp->isCopyAssignmentOperator() || assignOp->isMoveAssignmentOperator()); const Stmt *rootS = assignOp->getBody(); assert(isa(rootS) && "Body of an implicit assignment operator should be compound stmt."); const auto *rootCS = cast(rootS); assert(!cir::MissingFeatures::incrementProfileCounter()); assert(!cir::MissingFeatures::runCleanupsScope()); // Classic codegen uses a special class to attempt to replace member // initializers with memcpy. We could possibly defer that to the // lowering or optimization phases to keep the memory accesses more // explicit. For now, we don't insert memcpy at all, though in some // cases the AST contains a call to memcpy. assert(!cir::MissingFeatures::assignMemcpyizer()); for (Stmt *s : rootCS->body()) if (emitStmt(s, /*useCurrentScope=*/true).failed()) cgm.errorNYI(s->getSourceRange(), std::string("emitImplicitAssignmentOperatorBody: ") + s->getStmtClassName()); } void CIRGenFunction::destroyCXXObject(CIRGenFunction &cgf, Address addr, QualType type) { const RecordType *rtype = type->castAs(); const CXXRecordDecl *record = cast(rtype->getDecl()); const CXXDestructorDecl *dtor = record->getDestructor(); // TODO(cir): Unlike traditional codegen, CIRGen should actually emit trivial // dtors which shall be removed on later CIR passes. However, only remove this // assertion after we have a test case to exercise this path. assert(!dtor->isTrivial()); cgf.emitCXXDestructorCall(dtor, Dtor_Complete, /*forVirtualBase*/ false, /*delegating=*/false, addr, type); } void CIRGenFunction::emitDelegatingCXXConstructorCall( const CXXConstructorDecl *ctor, const FunctionArgList &args) { assert(ctor->isDelegatingConstructor()); Address thisPtr = loadCXXThisAddress(); assert(!cir::MissingFeatures::objCGC()); assert(!cir::MissingFeatures::sanitizers()); AggValueSlot aggSlot = AggValueSlot::forAddr( thisPtr, Qualifiers(), AggValueSlot::IsDestructed, AggValueSlot::IsNotAliased, AggValueSlot::MayOverlap, AggValueSlot::IsNotZeroed); emitAggExpr(ctor->init_begin()[0]->getInit(), aggSlot); const CXXRecordDecl *classDecl = ctor->getParent(); if (cgm.getLangOpts().Exceptions && !classDecl->hasTrivialDestructor()) { cgm.errorNYI(ctor->getSourceRange(), "emitDelegatingCXXConstructorCall: exception"); return; } } void CIRGenFunction::emitCXXDestructorCall(const CXXDestructorDecl *dd, CXXDtorType type, bool forVirtualBase, bool delegating, Address thisAddr, QualType thisTy) { cgm.getCXXABI().emitDestructorCall(*this, dd, type, forVirtualBase, delegating, thisAddr, thisTy); } Address CIRGenFunction::getAddressOfBaseClass( Address value, const CXXRecordDecl *derived, llvm::iterator_range path, bool nullCheckValue, SourceLocation loc) { assert(!path.empty() && "Base path should not be empty!"); if ((*path.begin())->isVirtual()) { // The implementation here is actually complete, but let's flag this // as an error until the rest of the virtual base class support is in place. cgm.errorNYI(loc, "getAddrOfBaseClass: virtual base"); return Address::invalid(); } // Compute the static offset of the ultimate destination within its // allocating subobject (the virtual base, if there is one, or else // the "complete" object that we see). CharUnits nonVirtualOffset = cgm.computeNonVirtualBaseClassOffset(derived, path); // Get the base pointer type. mlir::Type baseValueTy = convertType((path.end()[-1])->getType()); assert(!cir::MissingFeatures::addressSpace()); // The if statement here is redundant now, but it will be needed when we add // support for virtual base classes. // If there is no virtual base, use cir.base_class_addr. It takes care of // the adjustment and the null pointer check. if (nonVirtualOffset.isZero()) { assert(!cir::MissingFeatures::sanitizers()); return builder.createBaseClassAddr(getLoc(loc), value, baseValueTy, 0, /*assumeNotNull=*/true); } assert(!cir::MissingFeatures::sanitizers()); // Apply the offset value = builder.createBaseClassAddr(getLoc(loc), value, baseValueTy, nonVirtualOffset.getQuantity(), /*assumeNotNull=*/true); // Cast to the destination type. value = value.withElementType(builder, baseValueTy); return value; } void CIRGenFunction::emitCXXConstructorCall(const clang::CXXConstructorDecl *d, clang::CXXCtorType type, bool forVirtualBase, bool delegating, AggValueSlot thisAVS, const clang::CXXConstructExpr *e) { CallArgList args; Address thisAddr = thisAVS.getAddress(); QualType thisType = d->getThisType(); mlir::Value thisPtr = thisAddr.getPointer(); assert(!cir::MissingFeatures::addressSpace()); args.add(RValue::get(thisPtr), thisType); // In LLVM Codegen: If this is a trivial constructor, just emit what's needed. // If this is a union copy constructor, we must emit a memcpy, because the AST // does not model that copy. assert(!cir::MissingFeatures::isMemcpyEquivalentSpecialMember()); const FunctionProtoType *fpt = d->getType()->castAs(); assert(!cir::MissingFeatures::opCallArgEvaluationOrder()); emitCallArgs(args, fpt, e->arguments(), e->getConstructor(), /*ParamsToSkip=*/0); assert(!cir::MissingFeatures::sanitizers()); emitCXXConstructorCall(d, type, forVirtualBase, delegating, thisAddr, args, e->getExprLoc()); } void CIRGenFunction::emitCXXConstructorCall( const CXXConstructorDecl *d, CXXCtorType type, bool forVirtualBase, bool delegating, Address thisAddr, CallArgList &args, SourceLocation loc) { const CXXRecordDecl *crd = d->getParent(); // If this is a call to a trivial default constructor: // In LLVM: do nothing. // In CIR: emit as a regular call, other later passes should lower the // ctor call into trivial initialization. assert(!cir::MissingFeatures::isTrivialCtorOrDtor()); assert(!cir::MissingFeatures::isMemcpyEquivalentSpecialMember()); bool passPrototypeArgs = true; // Check whether we can actually emit the constructor before trying to do so. if (d->getInheritedConstructor()) { cgm.errorNYI(d->getSourceRange(), "emitCXXConstructorCall: inherited constructor"); return; } // Insert any ABI-specific implicit constructor arguments. assert(!cir::MissingFeatures::implicitConstructorArgs()); // Emit the call. auto calleePtr = cgm.getAddrOfCXXStructor(GlobalDecl(d, type)); const CIRGenFunctionInfo &info = cgm.getTypes().arrangeCXXConstructorCall( args, d, type, passPrototypeArgs); CIRGenCallee callee = CIRGenCallee::forDirect(calleePtr, GlobalDecl(d, type)); cir::CIRCallOpInterface c; emitCall(info, callee, ReturnValueSlot(), args, &c, getLoc(loc)); if (cgm.getCodeGenOpts().OptimizationLevel != 0 && !crd->isDynamicClass() && type != Ctor_Base && cgm.getCodeGenOpts().StrictVTablePointers) cgm.errorNYI(d->getSourceRange(), "vtable assumption loads"); }