clang  3.9.0
AST/ItaniumCXXABI.cpp
Go to the documentation of this file.
1 //===------- ItaniumCXXABI.cpp - AST support for the Itanium C++ ABI ------===//
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 C++ AST support targeting the Itanium C++ ABI, which is
11 // documented at:
12 // http://www.codesourcery.com/public/cxx-abi/abi.html
13 // http://www.codesourcery.com/public/cxx-abi/abi-eh.html
14 //
15 // It also supports the closely-related ARM C++ ABI, documented at:
16 // http://infocenter.arm.com/help/topic/com.arm.doc.ihi0041c/IHI0041C_cppabi.pdf
17 //
18 //===----------------------------------------------------------------------===//
19 
20 #include "CXXABI.h"
21 #include "clang/AST/ASTContext.h"
22 #include "clang/AST/DeclCXX.h"
24 #include "clang/AST/RecordLayout.h"
25 #include "clang/AST/Type.h"
26 #include "clang/Basic/TargetInfo.h"
27 
28 using namespace clang;
29 
30 namespace {
31 
32 /// According to Itanium C++ ABI 5.1.2:
33 /// the name of an anonymous union is considered to be
34 /// the name of the first named data member found by a pre-order,
35 /// depth-first, declaration-order walk of the data members of
36 /// the anonymous union.
37 /// If there is no such data member (i.e., if all of the data members
38 /// in the union are unnamed), then there is no way for a program to
39 /// refer to the anonymous union, and there is therefore no need to mangle its name.
40 ///
41 /// Returns the name of anonymous union VarDecl or nullptr if it is not found.
42 static const IdentifierInfo *findAnonymousUnionVarDeclName(const VarDecl& VD) {
43  const RecordType *RT = VD.getType()->getAs<RecordType>();
44  assert(RT && "type of VarDecl is expected to be RecordType.");
45  assert(RT->getDecl()->isUnion() && "RecordType is expected to be a union.");
46  if (const FieldDecl *FD = RT->getDecl()->findFirstNamedDataMember()) {
47  return FD->getIdentifier();
48  }
49 
50  return nullptr;
51 }
52 
53 /// \brief Keeps track of the mangled names of lambda expressions and block
54 /// literals within a particular context.
55 class ItaniumNumberingContext : public MangleNumberingContext {
56  llvm::DenseMap<const Type *, unsigned> ManglingNumbers;
57  llvm::DenseMap<const IdentifierInfo *, unsigned> VarManglingNumbers;
58  llvm::DenseMap<const IdentifierInfo *, unsigned> TagManglingNumbers;
59 
60 public:
61  unsigned getManglingNumber(const CXXMethodDecl *CallOperator) override {
62  const FunctionProtoType *Proto =
63  CallOperator->getType()->getAs<FunctionProtoType>();
64  ASTContext &Context = CallOperator->getASTContext();
65 
66  QualType Key =
67  Context.getFunctionType(Context.VoidTy, Proto->getParamTypes(),
69  Key = Context.getCanonicalType(Key);
70  return ++ManglingNumbers[Key->castAs<FunctionProtoType>()];
71  }
72 
73  unsigned getManglingNumber(const BlockDecl *BD) override {
74  const Type *Ty = nullptr;
75  return ++ManglingNumbers[Ty];
76  }
77 
78  unsigned getStaticLocalNumber(const VarDecl *VD) override {
79  return 0;
80  }
81 
82  /// Variable decls are numbered by identifier.
83  unsigned getManglingNumber(const VarDecl *VD, unsigned) override {
84  const IdentifierInfo *Identifier = VD->getIdentifier();
85  if (!Identifier) {
86  // VarDecl without an identifier represents an anonymous union declaration.
87  Identifier = findAnonymousUnionVarDeclName(*VD);
88  }
89  return ++VarManglingNumbers[Identifier];
90  }
91 
92  unsigned getManglingNumber(const TagDecl *TD, unsigned) override {
93  return ++TagManglingNumbers[TD->getIdentifier()];
94  }
95 };
96 
97 class ItaniumCXXABI : public CXXABI {
98 protected:
100 public:
101  ItaniumCXXABI(ASTContext &Ctx) : Context(Ctx) { }
102 
103  std::pair<uint64_t, unsigned>
104  getMemberPointerWidthAndAlign(const MemberPointerType *MPT) const override {
105  const TargetInfo &Target = Context.getTargetInfo();
106  TargetInfo::IntType PtrDiff = Target.getPtrDiffType(0);
107  uint64_t Width = Target.getTypeWidth(PtrDiff);
108  unsigned Align = Target.getTypeAlign(PtrDiff);
109  if (MPT->isMemberFunctionPointer())
110  Width = 2 * Width;
111  return std::make_pair(Width, Align);
112  }
113 
114  CallingConv getDefaultMethodCallConv(bool isVariadic) const override {
115  const llvm::Triple &T = Context.getTargetInfo().getTriple();
116  if (!isVariadic && T.isWindowsGNUEnvironment() &&
117  T.getArch() == llvm::Triple::x86)
118  return CC_X86ThisCall;
119  return CC_C;
120  }
121 
122  // We cheat and just check that the class has a vtable pointer, and that it's
123  // only big enough to have a vtable pointer and nothing more (or less).
124  bool isNearlyEmpty(const CXXRecordDecl *RD) const override {
125 
126  // Check that the class has a vtable pointer.
127  if (!RD->isDynamicClass())
128  return false;
129 
130  const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
131  CharUnits PointerSize =
132  Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(0));
133  return Layout.getNonVirtualSize() == PointerSize;
134  }
135 
136  const CXXConstructorDecl *
137  getCopyConstructorForExceptionObject(CXXRecordDecl *RD) override {
138  return nullptr;
139  }
140 
141  void addCopyConstructorForExceptionObject(CXXRecordDecl *RD,
142  CXXConstructorDecl *CD) override {}
143 
144  void addDefaultArgExprForConstructor(const CXXConstructorDecl *CD,
145  unsigned ParmIdx, Expr *DAE) override {}
146 
147  Expr *getDefaultArgExprForConstructor(const CXXConstructorDecl *CD,
148  unsigned ParmIdx) override {
149  return nullptr;
150  }
151 
152  void addTypedefNameForUnnamedTagDecl(TagDecl *TD,
153  TypedefNameDecl *DD) override {}
154 
155  TypedefNameDecl *getTypedefNameForUnnamedTagDecl(const TagDecl *TD) override {
156  return nullptr;
157  }
158 
159  void addDeclaratorForUnnamedTagDecl(TagDecl *TD,
160  DeclaratorDecl *DD) override {}
161 
162  DeclaratorDecl *getDeclaratorForUnnamedTagDecl(const TagDecl *TD) override {
163  return nullptr;
164  }
165 
166  MangleNumberingContext *createMangleNumberingContext() const override {
167  return new ItaniumNumberingContext();
168  }
169 };
170 }
171 
173  return new ItaniumCXXABI(Ctx);
174 }
Defines the clang::ASTContext interface.
A (possibly-)qualified type.
Definition: Type.h:598
IdentifierInfo * getIdentifier() const
getIdentifier - Get the identifier that names this declaration, if there is one.
Definition: Decl.h:232
C Language Family Type Representation.
The base class of the type hierarchy.
Definition: Type.h:1281
Represents a C++ constructor within a class.
Definition: DeclCXX.h:2187
VarDecl - An instance of this class is created to represent a variable declaration or definition...
Definition: Decl.h:768
Extra information about a function prototype.
Definition: Type.h:3167
One of these records is kept for each identifier that is lexed.
Holds long-lived AST nodes (such as types and decls) that can be referred to throughout the semantic ...
Definition: ASTContext.h:92
ArrayRef< QualType > getParamTypes() const
Definition: Type.h:3276
FieldDecl - An instance of this class is created by Sema::ActOnField to represent a member of a struc...
Definition: Decl.h:2293
CharUnits - This is an opaque type for sizes expressed in character units.
Definition: CharUnits.h:38
Keeps track of the mangled names of lambda expressions and block literals within a particular context...
RecordDecl * getDecl() const
Definition: Type.h:3716
CXXABI * CreateItaniumCXXABI(ASTContext &Ctx)
Creates an instance of a C++ ABI class.
QualType getType() const
Definition: Decl.h:599
bool isMemberFunctionPointer() const
Returns true if the member type (i.e.
Definition: Type.h:2424
bool isUnion() const
Definition: Decl.h:2939
Represents a prototype with parameter type info, e.g.
Definition: Type.h:3073
Represents a ValueDecl that came out of a declarator.
Definition: Decl.h:646
ASTContext * Context
unsigned getTypeWidth(IntType T) const
Return the width (in bits) of the specified integer type enum.
ASTRecordLayout - This class contains layout information for one RecordDecl, which is a struct/union/...
Definition: RecordLayout.h:34
Exposes information about the current target.
BlockDecl - This represents a block literal declaration, which is like an unnamed FunctionDecl...
Definition: Decl.h:3456
Expr - This represents one expression.
Definition: Expr.h:105
Implements C++ ABI-specific semantic analysis functions.
Definition: CXXABI.h:30
CallingConv
CallingConv - Specifies the calling convention that a function uses.
Definition: Specifiers.h:231
unsigned getTypeAlign(IntType T) const
Return the alignment (in bits) of the specified integer type enum.
TagDecl - Represents the declaration of a struct/union/class/enum.
Definition: Decl.h:2727
Represents a static or instance method of a struct/union/class.
Definition: DeclCXX.h:1736
const T * castAs() const
Member-template castAs<specific type>.
Definition: Type.h:5849
bool isDynamicClass() const
Definition: DeclCXX.h:698
Base class for declarations which introduce a typedef-name.
Definition: Decl.h:2609
IntType
===-— Target Data Type Query Methods ----------------------------—===//
A pointer to member type per C++ 8.3.3 - Pointers to members.
Definition: Type.h:2401
A helper class that allows the use of isa/cast/dyncast to detect TagType objects of structs/unions/cl...
Definition: Type.h:3707
const T * getAs() const
Member-template getAs<specific type>'.
Definition: Type.h:5818
QualType getCanonicalType() const
Definition: Type.h:5298
CharUnits getNonVirtualSize() const
getNonVirtualSize - Get the non-virtual size (in chars) of an object, which is the size of the object...
Definition: RecordLayout.h:189
Defines the C++ Decl subclasses, other than those for templates (found in DeclTemplate.h) and friends (in DeclFriend.h).
const FieldDecl * findFirstNamedDataMember() const
Finds the first data member which has a name.
Definition: Decl.cpp:3857
Represents a C++ struct/union/class.
Definition: DeclCXX.h:263
Defines the clang::TargetInfo interface.
IntType getPtrDiffType(unsigned AddrSpace) const