1 //===----- CGCXXABI.h - Interface to C++ ABIs -------------------*- C++ -*-===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This provides an abstract class for C++ code generation. Concrete subclasses 11 // of this implement code generation for specific C++ ABIs. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #ifndef CLANG_CODEGEN_CXXABI_H 16 #define CLANG_CODEGEN_CXXABI_H 17 18 #include "clang/Basic/LLVM.h" 19 20 #include "CodeGenFunction.h" 21 22 namespace llvm { 23 class Constant; 24 class Type; 25 class Value; 26 } 27 28 namespace clang { 29 class CastExpr; 30 class CXXConstructorDecl; 31 class CXXDestructorDecl; 32 class CXXMethodDecl; 33 class CXXRecordDecl; 34 class FieldDecl; 35 class MangleContext; 36 37 namespace CodeGen { 38 class CodeGenFunction; 39 class CodeGenModule; 40 41 /// Implements C++ ABI-specific code generation functions. 42 class CGCXXABI { 43 protected: 44 CodeGenModule &CGM; 45 OwningPtr<MangleContext> MangleCtx; 46 CGCXXABI(CodeGenModule & CGM)47 CGCXXABI(CodeGenModule &CGM) 48 : CGM(CGM), MangleCtx(CGM.getContext().createMangleContext()) {} 49 50 protected: getThisDecl(CodeGenFunction & CGF)51 ImplicitParamDecl *&getThisDecl(CodeGenFunction &CGF) { 52 return CGF.CXXABIThisDecl; 53 } getThisValue(CodeGenFunction & CGF)54 llvm::Value *&getThisValue(CodeGenFunction &CGF) { 55 return CGF.CXXABIThisValue; 56 } 57 getVTTDecl(CodeGenFunction & CGF)58 ImplicitParamDecl *&getVTTDecl(CodeGenFunction &CGF) { 59 return CGF.CXXVTTDecl; 60 } getVTTValue(CodeGenFunction & CGF)61 llvm::Value *&getVTTValue(CodeGenFunction &CGF) { 62 return CGF.CXXVTTValue; 63 } 64 65 /// Build a parameter variable suitable for 'this'. 66 void BuildThisParam(CodeGenFunction &CGF, FunctionArgList &Params); 67 68 /// Perform prolog initialization of the parameter variable suitable 69 /// for 'this' emitted by BuildThisParam. 70 void EmitThisParam(CodeGenFunction &CGF); 71 getContext()72 ASTContext &getContext() const { return CGM.getContext(); } 73 74 public: 75 76 virtual ~CGCXXABI(); 77 78 /// Gets the mangle context. getMangleContext()79 MangleContext &getMangleContext() { 80 return *MangleCtx; 81 } 82 83 /// Find the LLVM type used to represent the given member pointer 84 /// type. 85 virtual llvm::Type * 86 ConvertMemberPointerType(const MemberPointerType *MPT); 87 88 /// Load a member function from an object and a member function 89 /// pointer. Apply the this-adjustment and set 'This' to the 90 /// adjusted value. 91 virtual llvm::Value * 92 EmitLoadOfMemberFunctionPointer(CodeGenFunction &CGF, 93 llvm::Value *&This, 94 llvm::Value *MemPtr, 95 const MemberPointerType *MPT); 96 97 /// Calculate an l-value from an object and a data member pointer. 98 virtual llvm::Value *EmitMemberDataPointerAddress(CodeGenFunction &CGF, 99 llvm::Value *Base, 100 llvm::Value *MemPtr, 101 const MemberPointerType *MPT); 102 103 /// Perform a derived-to-base, base-to-derived, or bitcast member 104 /// pointer conversion. 105 virtual llvm::Value *EmitMemberPointerConversion(CodeGenFunction &CGF, 106 const CastExpr *E, 107 llvm::Value *Src); 108 109 /// Perform a derived-to-base, base-to-derived, or bitcast member 110 /// pointer conversion on a constant value. 111 virtual llvm::Constant *EmitMemberPointerConversion(const CastExpr *E, 112 llvm::Constant *Src); 113 114 /// Return true if the given member pointer can be zero-initialized 115 /// (in the C++ sense) with an LLVM zeroinitializer. 116 virtual bool isZeroInitializable(const MemberPointerType *MPT); 117 118 /// Create a null member pointer of the given type. 119 virtual llvm::Constant *EmitNullMemberPointer(const MemberPointerType *MPT); 120 121 /// Create a member pointer for the given method. 122 virtual llvm::Constant *EmitMemberPointer(const CXXMethodDecl *MD); 123 124 /// Create a member pointer for the given field. 125 virtual llvm::Constant *EmitMemberDataPointer(const MemberPointerType *MPT, 126 CharUnits offset); 127 128 /// Create a member pointer for the given member pointer constant. 129 virtual llvm::Constant *EmitMemberPointer(const APValue &MP, QualType MPT); 130 131 /// Emit a comparison between two member pointers. Returns an i1. 132 virtual llvm::Value * 133 EmitMemberPointerComparison(CodeGenFunction &CGF, 134 llvm::Value *L, 135 llvm::Value *R, 136 const MemberPointerType *MPT, 137 bool Inequality); 138 139 /// Determine if a member pointer is non-null. Returns an i1. 140 virtual llvm::Value * 141 EmitMemberPointerIsNotNull(CodeGenFunction &CGF, 142 llvm::Value *MemPtr, 143 const MemberPointerType *MPT); 144 145 protected: 146 /// A utility method for computing the offset required for the given 147 /// base-to-derived or derived-to-base member-pointer conversion. 148 /// Does not handle virtual conversions (in case we ever fully 149 /// support an ABI that allows this). Returns null if no adjustment 150 /// is required. 151 llvm::Constant *getMemberPointerAdjustment(const CastExpr *E); 152 153 public: 154 /// Build the signature of the given constructor variant by adding 155 /// any required parameters. For convenience, ResTy has been 156 /// initialized to 'void', and ArgTys has been initialized with the 157 /// type of 'this' (although this may be changed by the ABI) and 158 /// will have the formal parameters added to it afterwards. 159 /// 160 /// If there are ever any ABIs where the implicit parameters are 161 /// intermixed with the formal parameters, we can address those 162 /// then. 163 virtual void BuildConstructorSignature(const CXXConstructorDecl *Ctor, 164 CXXCtorType T, 165 CanQualType &ResTy, 166 SmallVectorImpl<CanQualType> &ArgTys) = 0; 167 168 /// Build the signature of the given destructor variant by adding 169 /// any required parameters. For convenience, ResTy has been 170 /// initialized to 'void' and ArgTys has been initialized with the 171 /// type of 'this' (although this may be changed by the ABI). 172 virtual void BuildDestructorSignature(const CXXDestructorDecl *Dtor, 173 CXXDtorType T, 174 CanQualType &ResTy, 175 SmallVectorImpl<CanQualType> &ArgTys) = 0; 176 177 /// Build the ABI-specific portion of the parameter list for a 178 /// function. This generally involves a 'this' parameter and 179 /// possibly some extra data for constructors and destructors. 180 /// 181 /// ABIs may also choose to override the return type, which has been 182 /// initialized with the formal return type of the function. 183 virtual void BuildInstanceFunctionParams(CodeGenFunction &CGF, 184 QualType &ResTy, 185 FunctionArgList &Params) = 0; 186 187 /// Emit the ABI-specific prolog for the function. 188 virtual void EmitInstanceFunctionProlog(CodeGenFunction &CGF) = 0; 189 190 virtual void EmitReturnFromThunk(CodeGenFunction &CGF, 191 RValue RV, QualType ResultType); 192 193 /**************************** Array cookies ******************************/ 194 195 /// Returns the extra size required in order to store the array 196 /// cookie for the given type. May return 0 to indicate that no 197 /// array cookie is required. 198 /// 199 /// Several cases are filtered out before this method is called: 200 /// - non-array allocations never need a cookie 201 /// - calls to ::operator new(size_t, void*) never need a cookie 202 /// 203 /// \param ElementType - the allocated type of the expression, 204 /// i.e. the pointee type of the expression result type 205 virtual CharUnits GetArrayCookieSize(const CXXNewExpr *expr); 206 207 /// Initialize the array cookie for the given allocation. 208 /// 209 /// \param NewPtr - a char* which is the presumed-non-null 210 /// return value of the allocation function 211 /// \param NumElements - the computed number of elements, 212 /// potentially collapsed from the multidimensional array case 213 /// \param ElementType - the base element allocated type, 214 /// i.e. the allocated type after stripping all array types 215 virtual llvm::Value *InitializeArrayCookie(CodeGenFunction &CGF, 216 llvm::Value *NewPtr, 217 llvm::Value *NumElements, 218 const CXXNewExpr *expr, 219 QualType ElementType); 220 221 /// Reads the array cookie associated with the given pointer, 222 /// if it has one. 223 /// 224 /// \param Ptr - a pointer to the first element in the array 225 /// \param ElementType - the base element type of elements of the array 226 /// \param NumElements - an out parameter which will be initialized 227 /// with the number of elements allocated, or zero if there is no 228 /// cookie 229 /// \param AllocPtr - an out parameter which will be initialized 230 /// with a char* pointing to the address returned by the allocation 231 /// function 232 /// \param CookieSize - an out parameter which will be initialized 233 /// with the size of the cookie, or zero if there is no cookie 234 virtual void ReadArrayCookie(CodeGenFunction &CGF, llvm::Value *Ptr, 235 const CXXDeleteExpr *expr, 236 QualType ElementType, llvm::Value *&NumElements, 237 llvm::Value *&AllocPtr, CharUnits &CookieSize); 238 239 /*************************** Static local guards ****************************/ 240 241 /// Emits the guarded initializer and destructor setup for the given 242 /// variable, given that it couldn't be emitted as a constant. 243 /// If \p PerformInit is false, the initialization has been folded to a 244 /// constant and should not be performed. 245 /// 246 /// The variable may be: 247 /// - a static local variable 248 /// - a static data member of a class template instantiation 249 virtual void EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D, 250 llvm::GlobalVariable *DeclPtr, bool PerformInit); 251 252 }; 253 254 /// Creates an instance of a C++ ABI class. 255 CGCXXABI *CreateARMCXXABI(CodeGenModule &CGM); 256 CGCXXABI *CreateItaniumCXXABI(CodeGenModule &CGM); 257 CGCXXABI *CreateMicrosoftCXXABI(CodeGenModule &CGM); 258 259 } 260 } 261 262 #endif 263