CGCXXABI.h revision 0f30a12ce7b3d4d86c9ca9072f587da77c8eef34 
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/// 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
74public:
75
76  virtual ~CGCXXABI();
77
78  /// Gets the mangle context.
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
145protected:
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
153public:
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.
255CGCXXABI *CreateARMCXXABI(CodeGenModule &CGM);
256CGCXXABI *CreateItaniumCXXABI(CodeGenModule &CGM);
257CGCXXABI *CreateMicrosoftCXXABI(CodeGenModule &CGM);
258
259}
260}
261
262#endif
263