//===------- ItaniumCXXABI.cpp - Emit LLVM Code from ASTs for a Module ----===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This provides C++ code generation targeting the Itanium C++ ABI. The class // in this file generates structures that follow the Itanium C++ ABI, which is // documented at: // http://www.codesourcery.com/public/cxx-abi/abi.html // http://www.codesourcery.com/public/cxx-abi/abi-eh.html // // It also supports the closely-related ARM ABI, documented at: // http://infocenter.arm.com/help/topic/com.arm.doc.ihi0041c/IHI0041C_cppabi.pdf // //===----------------------------------------------------------------------===// #include "CGCXXABI.h" #include "CGRecordLayout.h" #include "CodeGenFunction.h" #include "CodeGenModule.h" #include #include #include #include #include using namespace clang; using namespace CodeGen; namespace { class ItaniumCXXABI : public CodeGen::CGCXXABI { private: llvm::IntegerType *PtrDiffTy; protected: bool IsARM; // It's a little silly for us to cache this. llvm::IntegerType *getPtrDiffTy() { if (!PtrDiffTy) { QualType T = getContext().getPointerDiffType(); llvm::Type *Ty = CGM.getTypes().ConvertType(T); PtrDiffTy = cast(Ty); } return PtrDiffTy; } bool NeedsArrayCookie(const CXXNewExpr *expr); bool NeedsArrayCookie(const CXXDeleteExpr *expr, QualType elementType); public: ItaniumCXXABI(CodeGen::CodeGenModule &CGM, bool IsARM = false) : CGCXXABI(CGM), PtrDiffTy(0), IsARM(IsARM) { } bool isZeroInitializable(const MemberPointerType *MPT); llvm::Type *ConvertMemberPointerType(const MemberPointerType *MPT); llvm::Value *EmitLoadOfMemberFunctionPointer(CodeGenFunction &CGF, llvm::Value *&This, llvm::Value *MemFnPtr, const MemberPointerType *MPT); llvm::Value *EmitMemberDataPointerAddress(CodeGenFunction &CGF, llvm::Value *Base, llvm::Value *MemPtr, const MemberPointerType *MPT); llvm::Value *EmitMemberPointerConversion(CodeGenFunction &CGF, const CastExpr *E, llvm::Value *Src); llvm::Constant *EmitMemberPointerConversion(const CastExpr *E, llvm::Constant *Src); llvm::Constant *EmitNullMemberPointer(const MemberPointerType *MPT); llvm::Constant *EmitMemberPointer(const CXXMethodDecl *MD); llvm::Constant *EmitMemberDataPointer(const MemberPointerType *MPT, CharUnits offset); llvm::Constant *EmitMemberPointer(const APValue &MP, QualType MPT); llvm::Constant *BuildMemberPointer(const CXXMethodDecl *MD, CharUnits ThisAdjustment); llvm::Value *EmitMemberPointerComparison(CodeGenFunction &CGF, llvm::Value *L, llvm::Value *R, const MemberPointerType *MPT, bool Inequality); llvm::Value *EmitMemberPointerIsNotNull(CodeGenFunction &CGF, llvm::Value *Addr, const MemberPointerType *MPT); void BuildConstructorSignature(const CXXConstructorDecl *Ctor, CXXCtorType T, CanQualType &ResTy, SmallVectorImpl &ArgTys); void BuildDestructorSignature(const CXXDestructorDecl *Dtor, CXXDtorType T, CanQualType &ResTy, SmallVectorImpl &ArgTys); void BuildInstanceFunctionParams(CodeGenFunction &CGF, QualType &ResTy, FunctionArgList &Params); void EmitInstanceFunctionProlog(CodeGenFunction &CGF); CharUnits GetArrayCookieSize(const CXXNewExpr *expr); llvm::Value *InitializeArrayCookie(CodeGenFunction &CGF, llvm::Value *NewPtr, llvm::Value *NumElements, const CXXNewExpr *expr, QualType ElementType); void ReadArrayCookie(CodeGenFunction &CGF, llvm::Value *Ptr, const CXXDeleteExpr *expr, QualType ElementType, llvm::Value *&NumElements, llvm::Value *&AllocPtr, CharUnits &CookieSize); void EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D, llvm::GlobalVariable *DeclPtr, bool PerformInit); }; class ARMCXXABI : public ItaniumCXXABI { public: ARMCXXABI(CodeGen::CodeGenModule &CGM) : ItaniumCXXABI(CGM, /*ARM*/ true) {} void BuildConstructorSignature(const CXXConstructorDecl *Ctor, CXXCtorType T, CanQualType &ResTy, SmallVectorImpl &ArgTys); void BuildDestructorSignature(const CXXDestructorDecl *Dtor, CXXDtorType T, CanQualType &ResTy, SmallVectorImpl &ArgTys); void BuildInstanceFunctionParams(CodeGenFunction &CGF, QualType &ResTy, FunctionArgList &Params); void EmitInstanceFunctionProlog(CodeGenFunction &CGF); void EmitReturnFromThunk(CodeGenFunction &CGF, RValue RV, QualType ResTy); CharUnits GetArrayCookieSize(const CXXNewExpr *expr); llvm::Value *InitializeArrayCookie(CodeGenFunction &CGF, llvm::Value *NewPtr, llvm::Value *NumElements, const CXXNewExpr *expr, QualType ElementType); void ReadArrayCookie(CodeGenFunction &CGF, llvm::Value *Ptr, const CXXDeleteExpr *expr, QualType ElementType, llvm::Value *&NumElements, llvm::Value *&AllocPtr, CharUnits &CookieSize); private: /// \brief Returns true if the given instance method is one of the /// kinds that the ARM ABI says returns 'this'. static bool HasThisReturn(GlobalDecl GD) { const CXXMethodDecl *MD = cast(GD.getDecl()); return ((isa(MD) && GD.getDtorType() != Dtor_Deleting) || (isa(MD))); } }; } CodeGen::CGCXXABI *CodeGen::CreateItaniumCXXABI(CodeGenModule &CGM) { return new ItaniumCXXABI(CGM); } CodeGen::CGCXXABI *CodeGen::CreateARMCXXABI(CodeGenModule &CGM) { return new ARMCXXABI(CGM); } llvm::Type * ItaniumCXXABI::ConvertMemberPointerType(const MemberPointerType *MPT) { if (MPT->isMemberDataPointer()) return getPtrDiffTy(); return llvm::StructType::get(getPtrDiffTy(), getPtrDiffTy(), NULL); } /// In the Itanium and ARM ABIs, method pointers have the form: /// struct { ptrdiff_t ptr; ptrdiff_t adj; } memptr; /// /// In the Itanium ABI: /// - method pointers are virtual if (memptr.ptr & 1) is nonzero /// - the this-adjustment is (memptr.adj) /// - the virtual offset is (memptr.ptr - 1) /// /// In the ARM ABI: /// - method pointers are virtual if (memptr.adj & 1) is nonzero /// - the this-adjustment is (memptr.adj >> 1) /// - the virtual offset is (memptr.ptr) /// ARM uses 'adj' for the virtual flag because Thumb functions /// may be only single-byte aligned. /// /// If the member is virtual, the adjusted 'this' pointer points /// to a vtable pointer from which the virtual offset is applied. /// /// If the member is non-virtual, memptr.ptr is the address of /// the function to call. llvm::Value * ItaniumCXXABI::EmitLoadOfMemberFunctionPointer(CodeGenFunction &CGF, llvm::Value *&This, llvm::Value *MemFnPtr, const MemberPointerType *MPT) { CGBuilderTy &Builder = CGF.Builder; const FunctionProtoType *FPT = MPT->getPointeeType()->getAs(); const CXXRecordDecl *RD = cast(MPT->getClass()->getAs()->getDecl()); llvm::FunctionType *FTy = CGM.getTypes().GetFunctionType( CGM.getTypes().arrangeCXXMethodType(RD, FPT)); llvm::IntegerType *ptrdiff = getPtrDiffTy(); llvm::Constant *ptrdiff_1 = llvm::ConstantInt::get(ptrdiff, 1); llvm::BasicBlock *FnVirtual = CGF.createBasicBlock("memptr.virtual"); llvm::BasicBlock *FnNonVirtual = CGF.createBasicBlock("memptr.nonvirtual"); llvm::BasicBlock *FnEnd = CGF.createBasicBlock("memptr.end"); // Extract memptr.adj, which is in the second field. llvm::Value *RawAdj = Builder.CreateExtractValue(MemFnPtr, 1, "memptr.adj"); // Compute the true adjustment. llvm::Value *Adj = RawAdj; if (IsARM) Adj = Builder.CreateAShr(Adj, ptrdiff_1, "memptr.adj.shifted"); // Apply the adjustment and cast back to the original struct type // for consistency. llvm::Value *Ptr = Builder.CreateBitCast(This, Builder.getInt8PtrTy()); Ptr = Builder.CreateInBoundsGEP(Ptr, Adj); This = Builder.CreateBitCast(Ptr, This->getType(), "this.adjusted"); // Load the function pointer. llvm::Value *FnAsInt = Builder.CreateExtractValue(MemFnPtr, 0, "memptr.ptr"); // If the LSB in the function pointer is 1, the function pointer points to // a virtual function. llvm::Value *IsVirtual; if (IsARM) IsVirtual = Builder.CreateAnd(RawAdj, ptrdiff_1); else IsVirtual = Builder.CreateAnd(FnAsInt, ptrdiff_1); IsVirtual = Builder.CreateIsNotNull(IsVirtual, "memptr.isvirtual"); Builder.CreateCondBr(IsVirtual, FnVirtual, FnNonVirtual); // In the virtual path, the adjustment left 'This' pointing to the // vtable of the correct base subobject. The "function pointer" is an // offset within the vtable (+1 for the virtual flag on non-ARM). CGF.EmitBlock(FnVirtual); // Cast the adjusted this to a pointer to vtable pointer and load. llvm::Type *VTableTy = Builder.getInt8PtrTy(); llvm::Value *VTable = Builder.CreateBitCast(This, VTableTy->getPointerTo()); VTable = Builder.CreateLoad(VTable, "memptr.vtable"); // Apply the offset. llvm::Value *VTableOffset = FnAsInt; if (!IsARM) VTableOffset = Builder.CreateSub(VTableOffset, ptrdiff_1); VTable = Builder.CreateGEP(VTable, VTableOffset); // Load the virtual function to call. VTable = Builder.CreateBitCast(VTable, FTy->getPointerTo()->getPointerTo()); llvm::Value *VirtualFn = Builder.CreateLoad(VTable, "memptr.virtualfn"); CGF.EmitBranch(FnEnd); // In the non-virtual path, the function pointer is actually a // function pointer. CGF.EmitBlock(FnNonVirtual); llvm::Value *NonVirtualFn = Builder.CreateIntToPtr(FnAsInt, FTy->getPointerTo(), "memptr.nonvirtualfn"); // We're done. CGF.EmitBlock(FnEnd); llvm::PHINode *Callee = Builder.CreatePHI(FTy->getPointerTo(), 2); Callee->addIncoming(VirtualFn, FnVirtual); Callee->addIncoming(NonVirtualFn, FnNonVirtual); return Callee; } /// Compute an l-value by applying the given pointer-to-member to a /// base object. llvm::Value *ItaniumCXXABI::EmitMemberDataPointerAddress(CodeGenFunction &CGF, llvm::Value *Base, llvm::Value *MemPtr, const MemberPointerType *MPT) { assert(MemPtr->getType() == getPtrDiffTy()); CGBuilderTy &Builder = CGF.Builder; unsigned AS = cast(Base->getType())->getAddressSpace(); // Cast to char*. Base = Builder.CreateBitCast(Base, Builder.getInt8Ty()->getPointerTo(AS)); // Apply the offset, which we assume is non-null. llvm::Value *Addr = Builder.CreateInBoundsGEP(Base, MemPtr, "memptr.offset"); // Cast the address to the appropriate pointer type, adopting the // address space of the base pointer. llvm::Type *PType = CGF.ConvertTypeForMem(MPT->getPointeeType())->getPointerTo(AS); return Builder.CreateBitCast(Addr, PType); } /// Perform a bitcast, derived-to-base, or base-to-derived member pointer /// conversion. /// /// Bitcast conversions are always a no-op under Itanium. /// /// Obligatory offset/adjustment diagram: /// <-- offset --> <-- adjustment --> /// |--------------------------|----------------------|--------------------| /// ^Derived address point ^Base address point ^Member address point /// /// So when converting a base member pointer to a derived member pointer, /// we add the offset to the adjustment because the address point has /// decreased; and conversely, when converting a derived MP to a base MP /// we subtract the offset from the adjustment because the address point /// has increased. /// /// The standard forbids (at compile time) conversion to and from /// virtual bases, which is why we don't have to consider them here. /// /// The standard forbids (at run time) casting a derived MP to a base /// MP when the derived MP does not point to a member of the base. /// This is why -1 is a reasonable choice for null data member /// pointers. llvm::Value * ItaniumCXXABI::EmitMemberPointerConversion(CodeGenFunction &CGF, const CastExpr *E, llvm::Value *src) { assert(E->getCastKind() == CK_DerivedToBaseMemberPointer || E->getCastKind() == CK_BaseToDerivedMemberPointer || E->getCastKind() == CK_ReinterpretMemberPointer); // Under Itanium, reinterprets don't require any additional processing. if (E->getCastKind() == CK_ReinterpretMemberPointer) return src; // Use constant emission if we can. if (isa(src)) return EmitMemberPointerConversion(E, cast(src)); llvm::Constant *adj = getMemberPointerAdjustment(E); if (!adj) return src; CGBuilderTy &Builder = CGF.Builder; bool isDerivedToBase = (E->getCastKind() == CK_DerivedToBaseMemberPointer); const MemberPointerType *destTy = E->getType()->castAs(); // For member data pointers, this is just a matter of adding the // offset if the source is non-null. if (destTy->isMemberDataPointer()) { llvm::Value *dst; if (isDerivedToBase) dst = Builder.CreateNSWSub(src, adj, "adj"); else dst = Builder.CreateNSWAdd(src, adj, "adj"); // Null check. llvm::Value *null = llvm::Constant::getAllOnesValue(src->getType()); llvm::Value *isNull = Builder.CreateICmpEQ(src, null, "memptr.isnull"); return Builder.CreateSelect(isNull, src, dst); } // The this-adjustment is left-shifted by 1 on ARM. if (IsARM) { uint64_t offset = cast(adj)->getZExtValue(); offset <<= 1; adj = llvm::ConstantInt::get(adj->getType(), offset); } llvm::Value *srcAdj = Builder.CreateExtractValue(src, 1, "src.adj"); llvm::Value *dstAdj; if (isDerivedToBase) dstAdj = Builder.CreateNSWSub(srcAdj, adj, "adj"); else dstAdj = Builder.CreateNSWAdd(srcAdj, adj, "adj"); return Builder.CreateInsertValue(src, dstAdj, 1); } llvm::Constant * ItaniumCXXABI::EmitMemberPointerConversion(const CastExpr *E, llvm::Constant *src) { assert(E->getCastKind() == CK_DerivedToBaseMemberPointer || E->getCastKind() == CK_BaseToDerivedMemberPointer || E->getCastKind() == CK_ReinterpretMemberPointer); // Under Itanium, reinterprets don't require any additional processing. if (E->getCastKind() == CK_ReinterpretMemberPointer) return src; // If the adjustment is trivial, we don't need to do anything. llvm::Constant *adj = getMemberPointerAdjustment(E); if (!adj) return src; bool isDerivedToBase = (E->getCastKind() == CK_DerivedToBaseMemberPointer); const MemberPointerType *destTy = E->getType()->castAs(); // For member data pointers, this is just a matter of adding the // offset if the source is non-null. if (destTy->isMemberDataPointer()) { // null maps to null. if (src->isAllOnesValue()) return src; if (isDerivedToBase) return llvm::ConstantExpr::getNSWSub(src, adj); else return llvm::ConstantExpr::getNSWAdd(src, adj); } // The this-adjustment is left-shifted by 1 on ARM. if (IsARM) { uint64_t offset = cast(adj)->getZExtValue(); offset <<= 1; adj = llvm::ConstantInt::get(adj->getType(), offset); } llvm::Constant *srcAdj = llvm::ConstantExpr::getExtractValue(src, 1); llvm::Constant *dstAdj; if (isDerivedToBase) dstAdj = llvm::ConstantExpr::getNSWSub(srcAdj, adj); else dstAdj = llvm::ConstantExpr::getNSWAdd(srcAdj, adj); return llvm::ConstantExpr::getInsertValue(src, dstAdj, 1); } llvm::Constant * ItaniumCXXABI::EmitNullMemberPointer(const MemberPointerType *MPT) { llvm::Type *ptrdiff_t = getPtrDiffTy(); // Itanium C++ ABI 2.3: // A NULL pointer is represented as -1. if (MPT->isMemberDataPointer()) return llvm::ConstantInt::get(ptrdiff_t, -1ULL, /*isSigned=*/true); llvm::Constant *Zero = llvm::ConstantInt::get(ptrdiff_t, 0); llvm::Constant *Values[2] = { Zero, Zero }; return llvm::ConstantStruct::getAnon(Values); } llvm::Constant * ItaniumCXXABI::EmitMemberDataPointer(const MemberPointerType *MPT, CharUnits offset) { // Itanium C++ ABI 2.3: // A pointer to data member is an offset from the base address of // the class object containing it, represented as a ptrdiff_t return llvm::ConstantInt::get(getPtrDiffTy(), offset.getQuantity()); } llvm::Constant *ItaniumCXXABI::EmitMemberPointer(const CXXMethodDecl *MD) { return BuildMemberPointer(MD, CharUnits::Zero()); } llvm::Constant *ItaniumCXXABI::BuildMemberPointer(const CXXMethodDecl *MD, CharUnits ThisAdjustment) { assert(MD->isInstance() && "Member function must not be static!"); MD = MD->getCanonicalDecl(); CodeGenTypes &Types = CGM.getTypes(); llvm::Type *ptrdiff_t = getPtrDiffTy(); // Get the function pointer (or index if this is a virtual function). llvm::Constant *MemPtr[2]; if (MD->isVirtual()) { uint64_t Index = CGM.getVTableContext().getMethodVTableIndex(MD); const ASTContext &Context = getContext(); CharUnits PointerWidth = Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(0)); uint64_t VTableOffset = (Index * PointerWidth.getQuantity()); if (IsARM) { // ARM C++ ABI 3.2.1: // This ABI specifies that adj contains twice the this // adjustment, plus 1 if the member function is virtual. The // least significant bit of adj then makes exactly the same // discrimination as the least significant bit of ptr does for // Itanium. MemPtr[0] = llvm::ConstantInt::get(ptrdiff_t, VTableOffset); MemPtr[1] = llvm::ConstantInt::get(ptrdiff_t, 2 * ThisAdjustment.getQuantity() + 1); } else { // Itanium C++ ABI 2.3: // For a virtual function, [the pointer field] is 1 plus the // virtual table offset (in bytes) of the function, // represented as a ptrdiff_t. MemPtr[0] = llvm::ConstantInt::get(ptrdiff_t, VTableOffset + 1); MemPtr[1] = llvm::ConstantInt::get(ptrdiff_t, ThisAdjustment.getQuantity()); } } else { const FunctionProtoType *FPT = MD->getType()->castAs(); llvm::Type *Ty; // Check whether the function has a computable LLVM signature. if (Types.isFuncTypeConvertible(FPT)) { // The function has a computable LLVM signature; use the correct type. Ty = Types.GetFunctionType(Types.arrangeCXXMethodDeclaration(MD)); } else { // Use an arbitrary non-function type to tell GetAddrOfFunction that the // function type is incomplete. Ty = ptrdiff_t; } llvm::Constant *addr = CGM.GetAddrOfFunction(MD, Ty); MemPtr[0] = llvm::ConstantExpr::getPtrToInt(addr, ptrdiff_t); MemPtr[1] = llvm::ConstantInt::get(ptrdiff_t, (IsARM ? 2 : 1) * ThisAdjustment.getQuantity()); } return llvm::ConstantStruct::getAnon(MemPtr); } llvm::Constant *ItaniumCXXABI::EmitMemberPointer(const APValue &MP, QualType MPType) { const MemberPointerType *MPT = MPType->castAs(); const ValueDecl *MPD = MP.getMemberPointerDecl(); if (!MPD) return EmitNullMemberPointer(MPT); // Compute the this-adjustment. CharUnits ThisAdjustment = CharUnits::Zero(); ArrayRef Path = MP.getMemberPointerPath(); bool DerivedMember = MP.isMemberPointerToDerivedMember(); const CXXRecordDecl *RD = cast(MPD->getDeclContext()); for (unsigned I = 0, N = Path.size(); I != N; ++I) { const CXXRecordDecl *Base = RD; const CXXRecordDecl *Derived = Path[I]; if (DerivedMember) std::swap(Base, Derived); ThisAdjustment += getContext().getASTRecordLayout(Derived).getBaseClassOffset(Base); RD = Path[I]; } if (DerivedMember) ThisAdjustment = -ThisAdjustment; if (const CXXMethodDecl *MD = dyn_cast(MPD)) return BuildMemberPointer(MD, ThisAdjustment); CharUnits FieldOffset = getContext().toCharUnitsFromBits(getContext().getFieldOffset(MPD)); return EmitMemberDataPointer(MPT, ThisAdjustment + FieldOffset); } /// The comparison algorithm is pretty easy: the member pointers are /// the same if they're either bitwise identical *or* both null. /// /// ARM is different here only because null-ness is more complicated. llvm::Value * ItaniumCXXABI::EmitMemberPointerComparison(CodeGenFunction &CGF, llvm::Value *L, llvm::Value *R, const MemberPointerType *MPT, bool Inequality) { CGBuilderTy &Builder = CGF.Builder; llvm::ICmpInst::Predicate Eq; llvm::Instruction::BinaryOps And, Or; if (Inequality) { Eq = llvm::ICmpInst::ICMP_NE; And = llvm::Instruction::Or; Or = llvm::Instruction::And; } else { Eq = llvm::ICmpInst::ICMP_EQ; And = llvm::Instruction::And; Or = llvm::Instruction::Or; } // Member data pointers are easy because there's a unique null // value, so it just comes down to bitwise equality. if (MPT->isMemberDataPointer()) return Builder.CreateICmp(Eq, L, R); // For member function pointers, the tautologies are more complex. // The Itanium tautology is: // (L == R) <==> (L.ptr == R.ptr && (L.ptr == 0 || L.adj == R.adj)) // The ARM tautology is: // (L == R) <==> (L.ptr == R.ptr && // (L.adj == R.adj || // (L.ptr == 0 && ((L.adj|R.adj) & 1) == 0))) // The inequality tautologies have exactly the same structure, except // applying De Morgan's laws. llvm::Value *LPtr = Builder.CreateExtractValue(L, 0, "lhs.memptr.ptr"); llvm::Value *RPtr = Builder.CreateExtractValue(R, 0, "rhs.memptr.ptr"); // This condition tests whether L.ptr == R.ptr. This must always be // true for equality to hold. llvm::Value *PtrEq = Builder.CreateICmp(Eq, LPtr, RPtr, "cmp.ptr"); // This condition, together with the assumption that L.ptr == R.ptr, // tests whether the pointers are both null. ARM imposes an extra // condition. llvm::Value *Zero = llvm::Constant::getNullValue(LPtr->getType()); llvm::Value *EqZero = Builder.CreateICmp(Eq, LPtr, Zero, "cmp.ptr.null"); // This condition tests whether L.adj == R.adj. If this isn't // true, the pointers are unequal unless they're both null. llvm::Value *LAdj = Builder.CreateExtractValue(L, 1, "lhs.memptr.adj"); llvm::Value *RAdj = Builder.CreateExtractValue(R, 1, "rhs.memptr.adj"); llvm::Value *AdjEq = Builder.CreateICmp(Eq, LAdj, RAdj, "cmp.adj"); // Null member function pointers on ARM clear the low bit of Adj, // so the zero condition has to check that neither low bit is set. if (IsARM) { llvm::Value *One = llvm::ConstantInt::get(LPtr->getType(), 1); // Compute (l.adj | r.adj) & 1 and test it against zero. llvm::Value *OrAdj = Builder.CreateOr(LAdj, RAdj, "or.adj"); llvm::Value *OrAdjAnd1 = Builder.CreateAnd(OrAdj, One); llvm::Value *OrAdjAnd1EqZero = Builder.CreateICmp(Eq, OrAdjAnd1, Zero, "cmp.or.adj"); EqZero = Builder.CreateBinOp(And, EqZero, OrAdjAnd1EqZero); } // Tie together all our conditions. llvm::Value *Result = Builder.CreateBinOp(Or, EqZero, AdjEq); Result = Builder.CreateBinOp(And, PtrEq, Result, Inequality ? "memptr.ne" : "memptr.eq"); return Result; } llvm::Value * ItaniumCXXABI::EmitMemberPointerIsNotNull(CodeGenFunction &CGF, llvm::Value *MemPtr, const MemberPointerType *MPT) { CGBuilderTy &Builder = CGF.Builder; /// For member data pointers, this is just a check against -1. if (MPT->isMemberDataPointer()) { assert(MemPtr->getType() == getPtrDiffTy()); llvm::Value *NegativeOne = llvm::Constant::getAllOnesValue(MemPtr->getType()); return Builder.CreateICmpNE(MemPtr, NegativeOne, "memptr.tobool"); } // In Itanium, a member function pointer is not null if 'ptr' is not null. llvm::Value *Ptr = Builder.CreateExtractValue(MemPtr, 0, "memptr.ptr"); llvm::Constant *Zero = llvm::ConstantInt::get(Ptr->getType(), 0); llvm::Value *Result = Builder.CreateICmpNE(Ptr, Zero, "memptr.tobool"); // On ARM, a member function pointer is also non-null if the low bit of 'adj' // (the virtual bit) is set. if (IsARM) { llvm::Constant *One = llvm::ConstantInt::get(Ptr->getType(), 1); llvm::Value *Adj = Builder.CreateExtractValue(MemPtr, 1, "memptr.adj"); llvm::Value *VirtualBit = Builder.CreateAnd(Adj, One, "memptr.virtualbit"); llvm::Value *IsVirtual = Builder.CreateICmpNE(VirtualBit, Zero, "memptr.isvirtual"); Result = Builder.CreateOr(Result, IsVirtual); } return Result; } /// The Itanium ABI requires non-zero initialization only for data /// member pointers, for which '0' is a valid offset. bool ItaniumCXXABI::isZeroInitializable(const MemberPointerType *MPT) { return MPT->getPointeeType()->isFunctionType(); } /// The generic ABI passes 'this', plus a VTT if it's initializing a /// base subobject. void ItaniumCXXABI::BuildConstructorSignature(const CXXConstructorDecl *Ctor, CXXCtorType Type, CanQualType &ResTy, SmallVectorImpl &ArgTys) { ASTContext &Context = getContext(); // 'this' is already there. // Check if we need to add a VTT parameter (which has type void **). if (Type == Ctor_Base && Ctor->getParent()->getNumVBases() != 0) ArgTys.push_back(Context.getPointerType(Context.VoidPtrTy)); } /// The ARM ABI does the same as the Itanium ABI, but returns 'this'. void ARMCXXABI::BuildConstructorSignature(const CXXConstructorDecl *Ctor, CXXCtorType Type, CanQualType &ResTy, SmallVectorImpl &ArgTys) { ItaniumCXXABI::BuildConstructorSignature(Ctor, Type, ResTy, ArgTys); ResTy = ArgTys[0]; } /// The generic ABI passes 'this', plus a VTT if it's destroying a /// base subobject. void ItaniumCXXABI::BuildDestructorSignature(const CXXDestructorDecl *Dtor, CXXDtorType Type, CanQualType &ResTy, SmallVectorImpl &ArgTys) { ASTContext &Context = getContext(); // 'this' is already there. // Check if we need to add a VTT parameter (which has type void **). if (Type == Dtor_Base && Dtor->getParent()->getNumVBases() != 0) ArgTys.push_back(Context.getPointerType(Context.VoidPtrTy)); } /// The ARM ABI does the same as the Itanium ABI, but returns 'this' /// for non-deleting destructors. void ARMCXXABI::BuildDestructorSignature(const CXXDestructorDecl *Dtor, CXXDtorType Type, CanQualType &ResTy, SmallVectorImpl &ArgTys) { ItaniumCXXABI::BuildDestructorSignature(Dtor, Type, ResTy, ArgTys); if (Type != Dtor_Deleting) ResTy = ArgTys[0]; } void ItaniumCXXABI::BuildInstanceFunctionParams(CodeGenFunction &CGF, QualType &ResTy, FunctionArgList &Params) { /// Create the 'this' variable. BuildThisParam(CGF, Params); const CXXMethodDecl *MD = cast(CGF.CurGD.getDecl()); assert(MD->isInstance()); // Check if we need a VTT parameter as well. if (CodeGenVTables::needsVTTParameter(CGF.CurGD)) { ASTContext &Context = getContext(); // FIXME: avoid the fake decl QualType T = Context.getPointerType(Context.VoidPtrTy); ImplicitParamDecl *VTTDecl = ImplicitParamDecl::Create(Context, 0, MD->getLocation(), &Context.Idents.get("vtt"), T); Params.push_back(VTTDecl); getVTTDecl(CGF) = VTTDecl; } } void ARMCXXABI::BuildInstanceFunctionParams(CodeGenFunction &CGF, QualType &ResTy, FunctionArgList &Params) { ItaniumCXXABI::BuildInstanceFunctionParams(CGF, ResTy, Params); // Return 'this' from certain constructors and destructors. if (HasThisReturn(CGF.CurGD)) ResTy = Params[0]->getType(); } void ItaniumCXXABI::EmitInstanceFunctionProlog(CodeGenFunction &CGF) { /// Initialize the 'this' slot. EmitThisParam(CGF); /// Initialize the 'vtt' slot if needed. if (getVTTDecl(CGF)) { getVTTValue(CGF) = CGF.Builder.CreateLoad(CGF.GetAddrOfLocalVar(getVTTDecl(CGF)), "vtt"); } } void ARMCXXABI::EmitInstanceFunctionProlog(CodeGenFunction &CGF) { ItaniumCXXABI::EmitInstanceFunctionProlog(CGF); /// Initialize the return slot to 'this' at the start of the /// function. if (HasThisReturn(CGF.CurGD)) CGF.Builder.CreateStore(getThisValue(CGF), CGF.ReturnValue); } void ARMCXXABI::EmitReturnFromThunk(CodeGenFunction &CGF, RValue RV, QualType ResultType) { if (!isa(CGF.CurGD.getDecl())) return ItaniumCXXABI::EmitReturnFromThunk(CGF, RV, ResultType); // Destructor thunks in the ARM ABI have indeterminate results. llvm::Type *T = cast(CGF.ReturnValue->getType())->getElementType(); RValue Undef = RValue::get(llvm::UndefValue::get(T)); return ItaniumCXXABI::EmitReturnFromThunk(CGF, Undef, ResultType); } /************************** Array allocation cookies **************************/ bool ItaniumCXXABI::NeedsArrayCookie(const CXXNewExpr *expr) { // If the class's usual deallocation function takes two arguments, // it needs a cookie. if (expr->doesUsualArrayDeleteWantSize()) return true; // Automatic Reference Counting: // We need an array cookie for pointers with strong or weak lifetime. QualType AllocatedType = expr->getAllocatedType(); if (getContext().getLangOpts().ObjCAutoRefCount && AllocatedType->isObjCLifetimeType()) { switch (AllocatedType.getObjCLifetime()) { case Qualifiers::OCL_None: case Qualifiers::OCL_ExplicitNone: case Qualifiers::OCL_Autoreleasing: return false; case Qualifiers::OCL_Strong: case Qualifiers::OCL_Weak: return true; } } // Otherwise, if the class has a non-trivial destructor, it always // needs a cookie. const CXXRecordDecl *record = AllocatedType->getBaseElementTypeUnsafe()->getAsCXXRecordDecl(); return (record && !record->hasTrivialDestructor()); } bool ItaniumCXXABI::NeedsArrayCookie(const CXXDeleteExpr *expr, QualType elementType) { // If the class's usual deallocation function takes two arguments, // it needs a cookie. if (expr->doesUsualArrayDeleteWantSize()) return true; return elementType.isDestructedType(); } CharUnits ItaniumCXXABI::GetArrayCookieSize(const CXXNewExpr *expr) { if (!NeedsArrayCookie(expr)) return CharUnits::Zero(); // Padding is the maximum of sizeof(size_t) and alignof(elementType) ASTContext &Ctx = getContext(); return std::max(Ctx.getTypeSizeInChars(Ctx.getSizeType()), Ctx.getTypeAlignInChars(expr->getAllocatedType())); } llvm::Value *ItaniumCXXABI::InitializeArrayCookie(CodeGenFunction &CGF, llvm::Value *NewPtr, llvm::Value *NumElements, const CXXNewExpr *expr, QualType ElementType) { assert(NeedsArrayCookie(expr)); unsigned AS = cast(NewPtr->getType())->getAddressSpace(); ASTContext &Ctx = getContext(); QualType SizeTy = Ctx.getSizeType(); CharUnits SizeSize = Ctx.getTypeSizeInChars(SizeTy); // The size of the cookie. CharUnits CookieSize = std::max(SizeSize, Ctx.getTypeAlignInChars(ElementType)); // Compute an offset to the cookie. llvm::Value *CookiePtr = NewPtr; CharUnits CookieOffset = CookieSize - SizeSize; if (!CookieOffset.isZero()) CookiePtr = CGF.Builder.CreateConstInBoundsGEP1_64(CookiePtr, CookieOffset.getQuantity()); // Write the number of elements into the appropriate slot. llvm::Value *NumElementsPtr = CGF.Builder.CreateBitCast(CookiePtr, CGF.ConvertType(SizeTy)->getPointerTo(AS)); CGF.Builder.CreateStore(NumElements, NumElementsPtr); // Finally, compute a pointer to the actual data buffer by skipping // over the cookie completely. return CGF.Builder.CreateConstInBoundsGEP1_64(NewPtr, CookieSize.getQuantity()); } void ItaniumCXXABI::ReadArrayCookie(CodeGenFunction &CGF, llvm::Value *Ptr, const CXXDeleteExpr *expr, QualType ElementType, llvm::Value *&NumElements, llvm::Value *&AllocPtr, CharUnits &CookieSize) { // Derive a char* in the same address space as the pointer. unsigned AS = cast(Ptr->getType())->getAddressSpace(); llvm::Type *CharPtrTy = CGF.Builder.getInt8Ty()->getPointerTo(AS); // If we don't need an array cookie, bail out early. if (!NeedsArrayCookie(expr, ElementType)) { AllocPtr = CGF.Builder.CreateBitCast(Ptr, CharPtrTy); NumElements = 0; CookieSize = CharUnits::Zero(); return; } QualType SizeTy = getContext().getSizeType(); CharUnits SizeSize = getContext().getTypeSizeInChars(SizeTy); llvm::Type *SizeLTy = CGF.ConvertType(SizeTy); CookieSize = std::max(SizeSize, getContext().getTypeAlignInChars(ElementType)); CharUnits NumElementsOffset = CookieSize - SizeSize; // Compute the allocated pointer. AllocPtr = CGF.Builder.CreateBitCast(Ptr, CharPtrTy); AllocPtr = CGF.Builder.CreateConstInBoundsGEP1_64(AllocPtr, -CookieSize.getQuantity()); llvm::Value *NumElementsPtr = AllocPtr; if (!NumElementsOffset.isZero()) NumElementsPtr = CGF.Builder.CreateConstInBoundsGEP1_64(NumElementsPtr, NumElementsOffset.getQuantity()); NumElementsPtr = CGF.Builder.CreateBitCast(NumElementsPtr, SizeLTy->getPointerTo(AS)); NumElements = CGF.Builder.CreateLoad(NumElementsPtr); } CharUnits ARMCXXABI::GetArrayCookieSize(const CXXNewExpr *expr) { if (!NeedsArrayCookie(expr)) return CharUnits::Zero(); // On ARM, the cookie is always: // struct array_cookie { // std::size_t element_size; // element_size != 0 // std::size_t element_count; // }; // TODO: what should we do if the allocated type actually wants // greater alignment? return getContext().getTypeSizeInChars(getContext().getSizeType()) * 2; } llvm::Value *ARMCXXABI::InitializeArrayCookie(CodeGenFunction &CGF, llvm::Value *NewPtr, llvm::Value *NumElements, const CXXNewExpr *expr, QualType ElementType) { assert(NeedsArrayCookie(expr)); // NewPtr is a char*. unsigned AS = cast(NewPtr->getType())->getAddressSpace(); ASTContext &Ctx = getContext(); CharUnits SizeSize = Ctx.getTypeSizeInChars(Ctx.getSizeType()); llvm::IntegerType *SizeTy = cast(CGF.ConvertType(Ctx.getSizeType())); // The cookie is always at the start of the buffer. llvm::Value *CookiePtr = NewPtr; // The first element is the element size. CookiePtr = CGF.Builder.CreateBitCast(CookiePtr, SizeTy->getPointerTo(AS)); llvm::Value *ElementSize = llvm::ConstantInt::get(SizeTy, Ctx.getTypeSizeInChars(ElementType).getQuantity()); CGF.Builder.CreateStore(ElementSize, CookiePtr); // The second element is the element count. CookiePtr = CGF.Builder.CreateConstInBoundsGEP1_32(CookiePtr, 1); CGF.Builder.CreateStore(NumElements, CookiePtr); // Finally, compute a pointer to the actual data buffer by skipping // over the cookie completely. CharUnits CookieSize = 2 * SizeSize; return CGF.Builder.CreateConstInBoundsGEP1_64(NewPtr, CookieSize.getQuantity()); } void ARMCXXABI::ReadArrayCookie(CodeGenFunction &CGF, llvm::Value *Ptr, const CXXDeleteExpr *expr, QualType ElementType, llvm::Value *&NumElements, llvm::Value *&AllocPtr, CharUnits &CookieSize) { // Derive a char* in the same address space as the pointer. unsigned AS = cast(Ptr->getType())->getAddressSpace(); llvm::Type *CharPtrTy = CGF.Builder.getInt8Ty()->getPointerTo(AS); // If we don't need an array cookie, bail out early. if (!NeedsArrayCookie(expr, ElementType)) { AllocPtr = CGF.Builder.CreateBitCast(Ptr, CharPtrTy); NumElements = 0; CookieSize = CharUnits::Zero(); return; } QualType SizeTy = getContext().getSizeType(); CharUnits SizeSize = getContext().getTypeSizeInChars(SizeTy); llvm::Type *SizeLTy = CGF.ConvertType(SizeTy); // The cookie size is always 2 * sizeof(size_t). CookieSize = 2 * SizeSize; // The allocated pointer is the input ptr, minus that amount. AllocPtr = CGF.Builder.CreateBitCast(Ptr, CharPtrTy); AllocPtr = CGF.Builder.CreateConstInBoundsGEP1_64(AllocPtr, -CookieSize.getQuantity()); // The number of elements is at offset sizeof(size_t) relative to that. llvm::Value *NumElementsPtr = CGF.Builder.CreateConstInBoundsGEP1_64(AllocPtr, SizeSize.getQuantity()); NumElementsPtr = CGF.Builder.CreateBitCast(NumElementsPtr, SizeLTy->getPointerTo(AS)); NumElements = CGF.Builder.CreateLoad(NumElementsPtr); } /*********************** Static local initialization **************************/ static llvm::Constant *getGuardAcquireFn(CodeGenModule &CGM, llvm::PointerType *GuardPtrTy) { // int __cxa_guard_acquire(__guard *guard_object); llvm::FunctionType *FTy = llvm::FunctionType::get(CGM.getTypes().ConvertType(CGM.getContext().IntTy), GuardPtrTy, /*isVarArg=*/false); return CGM.CreateRuntimeFunction(FTy, "__cxa_guard_acquire", llvm::Attribute::NoUnwind); } static llvm::Constant *getGuardReleaseFn(CodeGenModule &CGM, llvm::PointerType *GuardPtrTy) { // void __cxa_guard_release(__guard *guard_object); llvm::FunctionType *FTy = llvm::FunctionType::get(CGM.VoidTy, GuardPtrTy, /*isVarArg=*/false); return CGM.CreateRuntimeFunction(FTy, "__cxa_guard_release", llvm::Attribute::NoUnwind); } static llvm::Constant *getGuardAbortFn(CodeGenModule &CGM, llvm::PointerType *GuardPtrTy) { // void __cxa_guard_abort(__guard *guard_object); llvm::FunctionType *FTy = llvm::FunctionType::get(CGM.VoidTy, GuardPtrTy, /*isVarArg=*/false); return CGM.CreateRuntimeFunction(FTy, "__cxa_guard_abort", llvm::Attribute::NoUnwind); } namespace { struct CallGuardAbort : EHScopeStack::Cleanup { llvm::GlobalVariable *Guard; CallGuardAbort(llvm::GlobalVariable *Guard) : Guard(Guard) {} void Emit(CodeGenFunction &CGF, Flags flags) { CGF.Builder.CreateCall(getGuardAbortFn(CGF.CGM, Guard->getType()), Guard) ->setDoesNotThrow(); } }; } /// The ARM code here follows the Itanium code closely enough that we /// just special-case it at particular places. void ItaniumCXXABI::EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D, llvm::GlobalVariable *var, bool shouldPerformInit) { CGBuilderTy &Builder = CGF.Builder; // We only need to use thread-safe statics for local variables; // global initialization is always single-threaded. bool threadsafe = (getContext().getLangOpts().ThreadsafeStatics && D.isLocalVarDecl()); // If we have a global variable with internal linkage and thread-safe statics // are disabled, we can just let the guard variable be of type i8. bool useInt8GuardVariable = !threadsafe && var->hasInternalLinkage(); llvm::IntegerType *guardTy; if (useInt8GuardVariable) { guardTy = CGF.Int8Ty; } else { // Guard variables are 64 bits in the generic ABI and 32 bits on ARM. guardTy = (IsARM ? CGF.Int32Ty : CGF.Int64Ty); } llvm::PointerType *guardPtrTy = guardTy->getPointerTo(); // Create the guard variable if we don't already have it (as we // might if we're double-emitting this function body). llvm::GlobalVariable *guard = CGM.getStaticLocalDeclGuardAddress(&D); if (!guard) { // Mangle the name for the guard. SmallString<256> guardName; { llvm::raw_svector_ostream out(guardName); getMangleContext().mangleItaniumGuardVariable(&D, out); out.flush(); } // Create the guard variable with a zero-initializer. // Just absorb linkage and visibility from the guarded variable. guard = new llvm::GlobalVariable(CGM.getModule(), guardTy, false, var->getLinkage(), llvm::ConstantInt::get(guardTy, 0), guardName.str()); guard->setVisibility(var->getVisibility()); CGM.setStaticLocalDeclGuardAddress(&D, guard); } // Test whether the variable has completed initialization. llvm::Value *isInitialized; // ARM C++ ABI 3.2.3.1: // To support the potential use of initialization guard variables // as semaphores that are the target of ARM SWP and LDREX/STREX // synchronizing instructions we define a static initialization // guard variable to be a 4-byte aligned, 4- byte word with the // following inline access protocol. // #define INITIALIZED 1 // if ((obj_guard & INITIALIZED) != INITIALIZED) { // if (__cxa_guard_acquire(&obj_guard)) // ... // } if (IsARM && !useInt8GuardVariable) { llvm::Value *V = Builder.CreateLoad(guard); V = Builder.CreateAnd(V, Builder.getInt32(1)); isInitialized = Builder.CreateIsNull(V, "guard.uninitialized"); // Itanium C++ ABI 3.3.2: // The following is pseudo-code showing how these functions can be used: // if (obj_guard.first_byte == 0) { // if ( __cxa_guard_acquire (&obj_guard) ) { // try { // ... initialize the object ...; // } catch (...) { // __cxa_guard_abort (&obj_guard); // throw; // } // ... queue object destructor with __cxa_atexit() ...; // __cxa_guard_release (&obj_guard); // } // } } else { // Load the first byte of the guard variable. llvm::LoadInst *LI = Builder.CreateLoad(Builder.CreateBitCast(guard, CGM.Int8PtrTy)); LI->setAlignment(1); // Itanium ABI: // An implementation supporting thread-safety on multiprocessor // systems must also guarantee that references to the initialized // object do not occur before the load of the initialization flag. // // In LLVM, we do this by marking the load Acquire. if (threadsafe) LI->setAtomic(llvm::Acquire); isInitialized = Builder.CreateIsNull(LI, "guard.uninitialized"); } llvm::BasicBlock *InitCheckBlock = CGF.createBasicBlock("init.check"); llvm::BasicBlock *EndBlock = CGF.createBasicBlock("init.end"); // Check if the first byte of the guard variable is zero. Builder.CreateCondBr(isInitialized, InitCheckBlock, EndBlock); CGF.EmitBlock(InitCheckBlock); // Variables used when coping with thread-safe statics and exceptions. if (threadsafe) { // Call __cxa_guard_acquire. llvm::Value *V = Builder.CreateCall(getGuardAcquireFn(CGM, guardPtrTy), guard); llvm::BasicBlock *InitBlock = CGF.createBasicBlock("init"); Builder.CreateCondBr(Builder.CreateIsNotNull(V, "tobool"), InitBlock, EndBlock); // Call __cxa_guard_abort along the exceptional edge. CGF.EHStack.pushCleanup(EHCleanup, guard); CGF.EmitBlock(InitBlock); } // Emit the initializer and add a global destructor if appropriate. CGF.EmitCXXGlobalVarDeclInit(D, var, shouldPerformInit); if (threadsafe) { // Pop the guard-abort cleanup if we pushed one. CGF.PopCleanupBlock(); // Call __cxa_guard_release. This cannot throw. Builder.CreateCall(getGuardReleaseFn(CGM, guardPtrTy), guard); } else { Builder.CreateStore(llvm::ConstantInt::get(guardTy, 1), guard); } CGF.EmitBlock(EndBlock); }