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 "CodeGenFunction.h"
19#include "clang/Basic/LLVM.h"
20
21namespace llvm {
22  class Constant;
23  class Type;
24  class Value;
25}
26
27namespace clang {
28  class CastExpr;
29  class CXXConstructorDecl;
30  class CXXDestructorDecl;
31  class CXXMethodDecl;
32  class CXXRecordDecl;
33  class FieldDecl;
34  class MangleContext;
35
36namespace CodeGen {
37  class CodeGenFunction;
38  class CodeGenModule;
39
40/// \brief Implements C++ ABI-specific code generation functions.
41class CGCXXABI {
42protected:
43  CodeGenModule &CGM;
44  OwningPtr<MangleContext> MangleCtx;
45
46  CGCXXABI(CodeGenModule &CGM)
47    : CGM(CGM), MangleCtx(CGM.getContext().createMangleContext()) {}
48
49protected:
50  ImplicitParamDecl *&getThisDecl(CodeGenFunction &CGF) {
51    return CGF.CXXABIThisDecl;
52  }
53  llvm::Value *&getThisValue(CodeGenFunction &CGF) {
54    return CGF.CXXABIThisValue;
55  }
56
57  /// Issue a diagnostic about unsupported features in the ABI.
58  void ErrorUnsupportedABI(CodeGenFunction &CGF, StringRef S);
59
60  /// Get a null value for unsupported member pointers.
61  llvm::Constant *GetBogusMemberPointer(QualType T);
62
63  // FIXME: Every place that calls getVTT{Decl,Value} is something
64  // that needs to be abstracted properly.
65  ImplicitParamDecl *&getVTTDecl(CodeGenFunction &CGF) {
66    return CGF.CXXStructorImplicitParamDecl;
67  }
68  llvm::Value *&getVTTValue(CodeGenFunction &CGF) {
69    return CGF.CXXStructorImplicitParamValue;
70  }
71
72  ImplicitParamDecl *&getStructorImplicitParamDecl(CodeGenFunction &CGF) {
73    return CGF.CXXStructorImplicitParamDecl;
74  }
75  llvm::Value *&getStructorImplicitParamValue(CodeGenFunction &CGF) {
76    return CGF.CXXStructorImplicitParamValue;
77  }
78
79  /// Build a parameter variable suitable for 'this'.
80  void BuildThisParam(CodeGenFunction &CGF, FunctionArgList &Params);
81
82  /// Perform prolog initialization of the parameter variable suitable
83  /// for 'this' emitted by BuildThisParam.
84  void EmitThisParam(CodeGenFunction &CGF);
85
86  ASTContext &getContext() const { return CGM.getContext(); }
87
88  virtual bool requiresArrayCookie(const CXXDeleteExpr *E, QualType eltType);
89  virtual bool requiresArrayCookie(const CXXNewExpr *E);
90
91public:
92
93  virtual ~CGCXXABI();
94
95  /// Gets the mangle context.
96  MangleContext &getMangleContext() {
97    return *MangleCtx;
98  }
99
100  /// Returns true if the given constructor or destructor is one of the
101  /// kinds that the ABI says returns 'this' (only applies when called
102  /// non-virtually for destructors).
103  ///
104  /// There currently is no way to indicate if a destructor returns 'this'
105  /// when called virtually, and code generation does not support the case.
106  virtual bool HasThisReturn(GlobalDecl GD) const { return false; }
107
108  /// Returns true if the given record type should be returned indirectly.
109  virtual bool isReturnTypeIndirect(const CXXRecordDecl *RD) const = 0;
110
111  /// Specify how one should pass an argument of a record type.
112  enum RecordArgABI {
113    /// Pass it using the normal C aggregate rules for the ABI, potentially
114    /// introducing extra copies and passing some or all of it in registers.
115    RAA_Default = 0,
116
117    /// Pass it on the stack using its defined layout.  The argument must be
118    /// evaluated directly into the correct stack position in the arguments area,
119    /// and the call machinery must not move it or introduce extra copies.
120    RAA_DirectInMemory,
121
122    /// Pass it as a pointer to temporary memory.
123    RAA_Indirect
124  };
125
126  /// Returns how an argument of the given record type should be passed.
127  virtual RecordArgABI getRecordArgABI(const CXXRecordDecl *RD) const = 0;
128
129  /// Find the LLVM type used to represent the given member pointer
130  /// type.
131  virtual llvm::Type *
132  ConvertMemberPointerType(const MemberPointerType *MPT);
133
134  /// Load a member function from an object and a member function
135  /// pointer.  Apply the this-adjustment and set 'This' to the
136  /// adjusted value.
137  virtual llvm::Value *
138  EmitLoadOfMemberFunctionPointer(CodeGenFunction &CGF,
139                                  llvm::Value *&This,
140                                  llvm::Value *MemPtr,
141                                  const MemberPointerType *MPT);
142
143  /// Calculate an l-value from an object and a data member pointer.
144  virtual llvm::Value *EmitMemberDataPointerAddress(CodeGenFunction &CGF,
145                                                    llvm::Value *Base,
146                                                    llvm::Value *MemPtr,
147                                            const MemberPointerType *MPT);
148
149  /// Perform a derived-to-base, base-to-derived, or bitcast member
150  /// pointer conversion.
151  virtual llvm::Value *EmitMemberPointerConversion(CodeGenFunction &CGF,
152                                                   const CastExpr *E,
153                                                   llvm::Value *Src);
154
155  /// Perform a derived-to-base, base-to-derived, or bitcast member
156  /// pointer conversion on a constant value.
157  virtual llvm::Constant *EmitMemberPointerConversion(const CastExpr *E,
158                                                      llvm::Constant *Src);
159
160  /// Return true if the given member pointer can be zero-initialized
161  /// (in the C++ sense) with an LLVM zeroinitializer.
162  virtual bool isZeroInitializable(const MemberPointerType *MPT);
163
164  /// Create a null member pointer of the given type.
165  virtual llvm::Constant *EmitNullMemberPointer(const MemberPointerType *MPT);
166
167  /// Create a member pointer for the given method.
168  virtual llvm::Constant *EmitMemberPointer(const CXXMethodDecl *MD);
169
170  /// Create a member pointer for the given field.
171  virtual llvm::Constant *EmitMemberDataPointer(const MemberPointerType *MPT,
172                                                CharUnits offset);
173
174  /// Create a member pointer for the given member pointer constant.
175  virtual llvm::Constant *EmitMemberPointer(const APValue &MP, QualType MPT);
176
177  /// Emit a comparison between two member pointers.  Returns an i1.
178  virtual llvm::Value *
179  EmitMemberPointerComparison(CodeGenFunction &CGF,
180                              llvm::Value *L,
181                              llvm::Value *R,
182                              const MemberPointerType *MPT,
183                              bool Inequality);
184
185  /// Determine if a member pointer is non-null.  Returns an i1.
186  virtual llvm::Value *
187  EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
188                             llvm::Value *MemPtr,
189                             const MemberPointerType *MPT);
190
191protected:
192  /// A utility method for computing the offset required for the given
193  /// base-to-derived or derived-to-base member-pointer conversion.
194  /// Does not handle virtual conversions (in case we ever fully
195  /// support an ABI that allows this).  Returns null if no adjustment
196  /// is required.
197  llvm::Constant *getMemberPointerAdjustment(const CastExpr *E);
198
199  /// \brief Computes the non-virtual adjustment needed for a member pointer
200  /// conversion along an inheritance path stored in an APValue.  Unlike
201  /// getMemberPointerAdjustment(), the adjustment can be negative if the path
202  /// is from a derived type to a base type.
203  CharUnits getMemberPointerPathAdjustment(const APValue &MP);
204
205public:
206  /// Adjust the given non-null pointer to an object of polymorphic
207  /// type to point to the complete object.
208  ///
209  /// The IR type of the result should be a pointer but is otherwise
210  /// irrelevant.
211  virtual llvm::Value *adjustToCompleteObject(CodeGenFunction &CGF,
212                                              llvm::Value *ptr,
213                                              QualType type) = 0;
214
215  virtual llvm::Value *GetVirtualBaseClassOffset(CodeGenFunction &CGF,
216                                                 llvm::Value *This,
217                                                 const CXXRecordDecl *ClassDecl,
218                                        const CXXRecordDecl *BaseClassDecl) = 0;
219
220  /// Build the signature of the given constructor variant by adding
221  /// any required parameters.  For convenience, ArgTys has been initialized
222  /// with the type of 'this' and ResTy has been initialized with the type of
223  /// 'this' if HasThisReturn(GlobalDecl(Ctor, T)) is true or 'void' otherwise
224  /// (although both may be changed by the ABI).
225  ///
226  /// If there are ever any ABIs where the implicit parameters are
227  /// intermixed with the formal parameters, we can address those
228  /// then.
229  virtual void BuildConstructorSignature(const CXXConstructorDecl *Ctor,
230                                         CXXCtorType T,
231                                         CanQualType &ResTy,
232                               SmallVectorImpl<CanQualType> &ArgTys) = 0;
233
234  virtual llvm::BasicBlock *EmitCtorCompleteObjectHandler(CodeGenFunction &CGF,
235                                                          const CXXRecordDecl *RD);
236
237  /// Emit constructor variants required by this ABI.
238  virtual void EmitCXXConstructors(const CXXConstructorDecl *D) = 0;
239
240  /// Build the signature of the given destructor variant by adding
241  /// any required parameters.  For convenience, ArgTys has been initialized
242  /// with the type of 'this' and ResTy has been initialized with the type of
243  /// 'this' if HasThisReturn(GlobalDecl(Dtor, T)) is true or 'void' otherwise
244  /// (although both may be changed by the ABI).
245  virtual void BuildDestructorSignature(const CXXDestructorDecl *Dtor,
246                                        CXXDtorType T,
247                                        CanQualType &ResTy,
248                               SmallVectorImpl<CanQualType> &ArgTys) = 0;
249
250  /// Returns true if the given destructor type should be emitted as a linkonce
251  /// delegating thunk, regardless of whether the dtor is defined in this TU or
252  /// not.
253  virtual bool useThunkForDtorVariant(const CXXDestructorDecl *Dtor,
254                                      CXXDtorType DT) const = 0;
255
256  /// Emit destructor variants required by this ABI.
257  virtual void EmitCXXDestructors(const CXXDestructorDecl *D) = 0;
258
259  /// Build the ABI-specific portion of the parameter list for a
260  /// function.  This generally involves a 'this' parameter and
261  /// possibly some extra data for constructors and destructors.
262  ///
263  /// ABIs may also choose to override the return type, which has been
264  /// initialized with the type of 'this' if HasThisReturn(CGF.CurGD) is true or
265  /// the formal return type of the function otherwise.
266  virtual void BuildInstanceFunctionParams(CodeGenFunction &CGF,
267                                           QualType &ResTy,
268                                           FunctionArgList &Params) = 0;
269
270  /// Emit the ABI-specific prolog for the function.
271  virtual void EmitInstanceFunctionProlog(CodeGenFunction &CGF) = 0;
272
273  /// Emit the constructor call. Return the function that is called.
274  virtual void EmitConstructorCall(CodeGenFunction &CGF,
275                                   const CXXConstructorDecl *D,
276                                   CXXCtorType Type,
277                                   bool ForVirtualBase, bool Delegating,
278                                   llvm::Value *This,
279                                   CallExpr::const_arg_iterator ArgBeg,
280                                   CallExpr::const_arg_iterator ArgEnd) = 0;
281
282  /// Emit the ABI-specific virtual destructor call.
283  virtual void EmitVirtualDestructorCall(CodeGenFunction &CGF,
284                                         const CXXDestructorDecl *Dtor,
285                                         CXXDtorType DtorType,
286                                         SourceLocation CallLoc,
287                                         llvm::Value *This) = 0;
288
289  /// Emit any tables needed to implement virtual inheritance.  For Itanium,
290  /// this emits virtual table tables.  For the MSVC++ ABI, this emits virtual
291  /// base tables.
292  virtual void
293      EmitVirtualInheritanceTables(llvm::GlobalVariable::LinkageTypes Linkage,
294                                   const CXXRecordDecl *RD) = 0;
295
296  virtual void EmitReturnFromThunk(CodeGenFunction &CGF,
297                                   RValue RV, QualType ResultType);
298
299  /// Gets the pure virtual member call function.
300  virtual StringRef GetPureVirtualCallName() = 0;
301
302  /// Gets the deleted virtual member call name.
303  virtual StringRef GetDeletedVirtualCallName() = 0;
304
305  /**************************** Array cookies ******************************/
306
307  /// Returns the extra size required in order to store the array
308  /// cookie for the given new-expression.  May return 0 to indicate that no
309  /// array cookie is required.
310  ///
311  /// Several cases are filtered out before this method is called:
312  ///   - non-array allocations never need a cookie
313  ///   - calls to \::operator new(size_t, void*) never need a cookie
314  ///
315  /// \param expr - the new-expression being allocated.
316  virtual CharUnits GetArrayCookieSize(const CXXNewExpr *expr);
317
318  /// Initialize the array cookie for the given allocation.
319  ///
320  /// \param NewPtr - a char* which is the presumed-non-null
321  ///   return value of the allocation function
322  /// \param NumElements - the computed number of elements,
323  ///   potentially collapsed from the multidimensional array case;
324  ///   always a size_t
325  /// \param ElementType - the base element allocated type,
326  ///   i.e. the allocated type after stripping all array types
327  virtual llvm::Value *InitializeArrayCookie(CodeGenFunction &CGF,
328                                             llvm::Value *NewPtr,
329                                             llvm::Value *NumElements,
330                                             const CXXNewExpr *expr,
331                                             QualType ElementType);
332
333  /// Reads the array cookie associated with the given pointer,
334  /// if it has one.
335  ///
336  /// \param Ptr - a pointer to the first element in the array
337  /// \param ElementType - the base element type of elements of the array
338  /// \param NumElements - an out parameter which will be initialized
339  ///   with the number of elements allocated, or zero if there is no
340  ///   cookie
341  /// \param AllocPtr - an out parameter which will be initialized
342  ///   with a char* pointing to the address returned by the allocation
343  ///   function
344  /// \param CookieSize - an out parameter which will be initialized
345  ///   with the size of the cookie, or zero if there is no cookie
346  virtual void ReadArrayCookie(CodeGenFunction &CGF, llvm::Value *Ptr,
347                               const CXXDeleteExpr *expr,
348                               QualType ElementType, llvm::Value *&NumElements,
349                               llvm::Value *&AllocPtr, CharUnits &CookieSize);
350
351  /// Return whether the given global decl needs a VTT parameter.
352  virtual bool NeedsVTTParameter(GlobalDecl GD);
353
354protected:
355  /// Returns the extra size required in order to store the array
356  /// cookie for the given type.  Assumes that an array cookie is
357  /// required.
358  virtual CharUnits getArrayCookieSizeImpl(QualType elementType);
359
360  /// Reads the array cookie for an allocation which is known to have one.
361  /// This is called by the standard implementation of ReadArrayCookie.
362  ///
363  /// \param ptr - a pointer to the allocation made for an array, as a char*
364  /// \param cookieSize - the computed cookie size of an array
365  ///
366  /// Other parameters are as above.
367  ///
368  /// \return a size_t
369  virtual llvm::Value *readArrayCookieImpl(CodeGenFunction &IGF,
370                                           llvm::Value *ptr,
371                                           CharUnits cookieSize);
372
373public:
374
375  /*************************** Static local guards ****************************/
376
377  /// Emits the guarded initializer and destructor setup for the given
378  /// variable, given that it couldn't be emitted as a constant.
379  /// If \p PerformInit is false, the initialization has been folded to a
380  /// constant and should not be performed.
381  ///
382  /// The variable may be:
383  ///   - a static local variable
384  ///   - a static data member of a class template instantiation
385  virtual void EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D,
386                               llvm::GlobalVariable *DeclPtr, bool PerformInit);
387
388  /// Emit code to force the execution of a destructor during global
389  /// teardown.  The default implementation of this uses atexit.
390  ///
391  /// \param dtor - a function taking a single pointer argument
392  /// \param addr - a pointer to pass to the destructor function.
393  virtual void registerGlobalDtor(CodeGenFunction &CGF, const VarDecl &D,
394                                  llvm::Constant *dtor, llvm::Constant *addr);
395
396  /*************************** thread_local initialization ********************/
397
398  /// Emits ABI-required functions necessary to initialize thread_local
399  /// variables in this translation unit.
400  ///
401  /// \param Decls The thread_local declarations in this translation unit.
402  /// \param InitFunc If this translation unit contains any non-constant
403  ///        initialization or non-trivial destruction for thread_local
404  ///        variables, a function to perform the initialization. Otherwise, 0.
405  virtual void EmitThreadLocalInitFuncs(
406      llvm::ArrayRef<std::pair<const VarDecl *, llvm::GlobalVariable *> > Decls,
407      llvm::Function *InitFunc);
408
409  /// Emit a reference to a non-local thread_local variable (including
410  /// triggering the initialization of all thread_local variables in its
411  /// translation unit).
412  virtual LValue EmitThreadLocalDeclRefExpr(CodeGenFunction &CGF,
413                                            const DeclRefExpr *DRE);
414};
415
416// Create an instance of a C++ ABI class:
417
418/// Creates an Itanium-family ABI.
419CGCXXABI *CreateItaniumCXXABI(CodeGenModule &CGM);
420
421/// Creates a Microsoft-family ABI.
422CGCXXABI *CreateMicrosoftCXXABI(CodeGenModule &CGM);
423
424}
425}
426
427#endif
428