CGCXXABI.h revision 239462 
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
22namespace llvm {
23  class Constant;
24  class Type;
25  class Value;
26}
27
28namespace clang {
29  class CastExpr;
30  class CXXConstructorDecl;
31  class CXXDestructorDecl;
32  class CXXMethodDecl;
33  class CXXRecordDecl;
34  class FieldDecl;
35  class MangleContext;
36
37namespace CodeGen {
38  class CodeGenFunction;
39  class CodeGenModule;
40
41/// \brief Implements C++ ABI-specific code generation functions.
42class CGCXXABI {
43protected:
44  CodeGenModule &CGM;
45  OwningPtr<MangleContext> MangleCtx;
46
47  CGCXXABI(CodeGenModule &CGM)
48    : CGM(CGM), MangleCtx(CGM.getContext().createMangleContext()) {}
49
50protected:
51  ImplicitParamDecl *&getThisDecl(CodeGenFunction &CGF) {
52    return CGF.CXXABIThisDecl;
53  }
54  llvm::Value *&getThisValue(CodeGenFunction &CGF) {
55    return CGF.CXXABIThisValue;
56  }
57
58  ImplicitParamDecl *&getVTTDecl(CodeGenFunction &CGF) {
59    return CGF.CXXVTTDecl;
60  }
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
72  ASTContext &getContext() const { return CGM.getContext(); }
73
74  virtual bool requiresArrayCookie(const CXXDeleteExpr *E, QualType eltType);
75  virtual bool requiresArrayCookie(const CXXNewExpr *E);
76
77public:
78
79  virtual ~CGCXXABI();
80
81  /// Gets the mangle context.
82  MangleContext &getMangleContext() {
83    return *MangleCtx;
84  }
85
86  /// Find the LLVM type used to represent the given member pointer
87  /// type.
88  virtual llvm::Type *
89  ConvertMemberPointerType(const MemberPointerType *MPT);
90
91  /// Load a member function from an object and a member function
92  /// pointer.  Apply the this-adjustment and set 'This' to the
93  /// adjusted value.
94  virtual llvm::Value *
95  EmitLoadOfMemberFunctionPointer(CodeGenFunction &CGF,
96                                  llvm::Value *&This,
97                                  llvm::Value *MemPtr,
98                                  const MemberPointerType *MPT);
99
100  /// Calculate an l-value from an object and a data member pointer.
101  virtual llvm::Value *EmitMemberDataPointerAddress(CodeGenFunction &CGF,
102                                                    llvm::Value *Base,
103                                                    llvm::Value *MemPtr,
104                                            const MemberPointerType *MPT);
105
106  /// Perform a derived-to-base, base-to-derived, or bitcast member
107  /// pointer conversion.
108  virtual llvm::Value *EmitMemberPointerConversion(CodeGenFunction &CGF,
109                                                   const CastExpr *E,
110                                                   llvm::Value *Src);
111
112  /// Perform a derived-to-base, base-to-derived, or bitcast member
113  /// pointer conversion on a constant value.
114  virtual llvm::Constant *EmitMemberPointerConversion(const CastExpr *E,
115                                                      llvm::Constant *Src);
116
117  /// Return true if the given member pointer can be zero-initialized
118  /// (in the C++ sense) with an LLVM zeroinitializer.
119  virtual bool isZeroInitializable(const MemberPointerType *MPT);
120
121  /// Create a null member pointer of the given type.
122  virtual llvm::Constant *EmitNullMemberPointer(const MemberPointerType *MPT);
123
124  /// Create a member pointer for the given method.
125  virtual llvm::Constant *EmitMemberPointer(const CXXMethodDecl *MD);
126
127  /// Create a member pointer for the given field.
128  virtual llvm::Constant *EmitMemberDataPointer(const MemberPointerType *MPT,
129                                                CharUnits offset);
130
131  /// Create a member pointer for the given member pointer constant.
132  virtual llvm::Constant *EmitMemberPointer(const APValue &MP, QualType MPT);
133
134  /// Emit a comparison between two member pointers.  Returns an i1.
135  virtual llvm::Value *
136  EmitMemberPointerComparison(CodeGenFunction &CGF,
137                              llvm::Value *L,
138                              llvm::Value *R,
139                              const MemberPointerType *MPT,
140                              bool Inequality);
141
142  /// Determine if a member pointer is non-null.  Returns an i1.
143  virtual llvm::Value *
144  EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
145                             llvm::Value *MemPtr,
146                             const MemberPointerType *MPT);
147
148protected:
149  /// A utility method for computing the offset required for the given
150  /// base-to-derived or derived-to-base member-pointer conversion.
151  /// Does not handle virtual conversions (in case we ever fully
152  /// support an ABI that allows this).  Returns null if no adjustment
153  /// is required.
154  llvm::Constant *getMemberPointerAdjustment(const CastExpr *E);
155
156public:
157  /// Build the signature of the given constructor variant by adding
158  /// any required parameters.  For convenience, ResTy has been
159  /// initialized to 'void', and ArgTys has been initialized with the
160  /// type of 'this' (although this may be changed by the ABI) and
161  /// will have the formal parameters added to it afterwards.
162  ///
163  /// If there are ever any ABIs where the implicit parameters are
164  /// intermixed with the formal parameters, we can address those
165  /// then.
166  virtual void BuildConstructorSignature(const CXXConstructorDecl *Ctor,
167                                         CXXCtorType T,
168                                         CanQualType &ResTy,
169                               SmallVectorImpl<CanQualType> &ArgTys) = 0;
170
171  /// Build the signature of the given destructor variant by adding
172  /// any required parameters.  For convenience, ResTy has been
173  /// initialized to 'void' and ArgTys has been initialized with the
174  /// type of 'this' (although this may be changed by the ABI).
175  virtual void BuildDestructorSignature(const CXXDestructorDecl *Dtor,
176                                        CXXDtorType T,
177                                        CanQualType &ResTy,
178                               SmallVectorImpl<CanQualType> &ArgTys) = 0;
179
180  /// Build the ABI-specific portion of the parameter list for a
181  /// function.  This generally involves a 'this' parameter and
182  /// possibly some extra data for constructors and destructors.
183  ///
184  /// ABIs may also choose to override the return type, which has been
185  /// initialized with the formal return type of the function.
186  virtual void BuildInstanceFunctionParams(CodeGenFunction &CGF,
187                                           QualType &ResTy,
188                                           FunctionArgList &Params) = 0;
189
190  /// Emit the ABI-specific prolog for the function.
191  virtual void EmitInstanceFunctionProlog(CodeGenFunction &CGF) = 0;
192
193  virtual void EmitReturnFromThunk(CodeGenFunction &CGF,
194                                   RValue RV, QualType ResultType);
195
196  /// Gets the pure virtual member call function.
197  virtual StringRef GetPureVirtualCallName() = 0;
198
199  /**************************** Array cookies ******************************/
200
201  /// Returns the extra size required in order to store the array
202  /// cookie for the given new-expression.  May return 0 to indicate that no
203  /// array cookie is required.
204  ///
205  /// Several cases are filtered out before this method is called:
206  ///   - non-array allocations never need a cookie
207  ///   - calls to \::operator new(size_t, void*) never need a cookie
208  ///
209  /// \param expr - the new-expression being allocated.
210  virtual CharUnits GetArrayCookieSize(const CXXNewExpr *expr);
211
212  /// Initialize the array cookie for the given allocation.
213  ///
214  /// \param NewPtr - a char* which is the presumed-non-null
215  ///   return value of the allocation function
216  /// \param NumElements - the computed number of elements,
217  ///   potentially collapsed from the multidimensional array case;
218  ///   always a size_t
219  /// \param ElementType - the base element allocated type,
220  ///   i.e. the allocated type after stripping all array types
221  virtual llvm::Value *InitializeArrayCookie(CodeGenFunction &CGF,
222                                             llvm::Value *NewPtr,
223                                             llvm::Value *NumElements,
224                                             const CXXNewExpr *expr,
225                                             QualType ElementType);
226
227  /// Reads the array cookie associated with the given pointer,
228  /// if it has one.
229  ///
230  /// \param Ptr - a pointer to the first element in the array
231  /// \param ElementType - the base element type of elements of the array
232  /// \param NumElements - an out parameter which will be initialized
233  ///   with the number of elements allocated, or zero if there is no
234  ///   cookie
235  /// \param AllocPtr - an out parameter which will be initialized
236  ///   with a char* pointing to the address returned by the allocation
237  ///   function
238  /// \param CookieSize - an out parameter which will be initialized
239  ///   with the size of the cookie, or zero if there is no cookie
240  virtual void ReadArrayCookie(CodeGenFunction &CGF, llvm::Value *Ptr,
241                               const CXXDeleteExpr *expr,
242                               QualType ElementType, llvm::Value *&NumElements,
243                               llvm::Value *&AllocPtr, CharUnits &CookieSize);
244
245protected:
246  /// Returns the extra size required in order to store the array
247  /// cookie for the given type.  Assumes that an array cookie is
248  /// required.
249  virtual CharUnits getArrayCookieSizeImpl(QualType elementType);
250
251  /// Reads the array cookie for an allocation which is known to have one.
252  /// This is called by the standard implementation of ReadArrayCookie.
253  ///
254  /// \param ptr - a pointer to the allocation made for an array, as a char*
255  /// \param cookieSize - the computed cookie size of an array
256  ///
257  /// Other parameters are as above.
258  ///
259  /// \return a size_t
260  virtual llvm::Value *readArrayCookieImpl(CodeGenFunction &IGF,
261                                           llvm::Value *ptr,
262                                           CharUnits cookieSize);
263
264public:
265
266  /*************************** Static local guards ****************************/
267
268  /// Emits the guarded initializer and destructor setup for the given
269  /// variable, given that it couldn't be emitted as a constant.
270  /// If \p PerformInit is false, the initialization has been folded to a
271  /// constant and should not be performed.
272  ///
273  /// The variable may be:
274  ///   - a static local variable
275  ///   - a static data member of a class template instantiation
276  virtual void EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D,
277                               llvm::GlobalVariable *DeclPtr, bool PerformInit);
278
279  /// Emit code to force the execution of a destructor during global
280  /// teardown.  The default implementation of this uses atexit.
281  ///
282  /// \param dtor - a function taking a single pointer argument
283  /// \param addr - a pointer to pass to the destructor function.
284  virtual void registerGlobalDtor(CodeGenFunction &CGF, llvm::Constant *dtor,
285                                  llvm::Constant *addr);
286
287  /***************************** Virtual Tables *******************************/
288
289  /// Generates and emits the virtual tables for a class.
290  virtual void EmitVTables(const CXXRecordDecl *Class) = 0;
291};
292
293/// Creates an instance of a C++ ABI class.
294CGCXXABI *CreateARMCXXABI(CodeGenModule &CGM);
295CGCXXABI *CreateItaniumCXXABI(CodeGenModule &CGM);
296CGCXXABI *CreateMicrosoftCXXABI(CodeGenModule &CGM);
297
298}
299}
300
301#endif
302