clang  10.0.0svn
ItaniumCXXABI.cpp
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1 //===------- ItaniumCXXABI.cpp - AST support for the Itanium C++ ABI ------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This provides C++ AST support targeting the Itanium C++ ABI, which is
10 // documented at:
11 // http://www.codesourcery.com/public/cxx-abi/abi.html
12 // http://www.codesourcery.com/public/cxx-abi/abi-eh.html
13 //
14 // It also supports the closely-related ARM C++ ABI, documented at:
15 // http://infocenter.arm.com/help/topic/com.arm.doc.ihi0041c/IHI0041C_cppabi.pdf
16 //
17 //===----------------------------------------------------------------------===//
18 
19 #include "CXXABI.h"
20 #include "clang/AST/ASTContext.h"
21 #include "clang/AST/DeclCXX.h"
22 #include "clang/AST/Mangle.h"
24 #include "clang/AST/RecordLayout.h"
25 #include "clang/AST/Type.h"
26 #include "clang/Basic/TargetInfo.h"
27 #include "llvm/ADT/FoldingSet.h"
28 #include "llvm/ADT/iterator.h"
29 
30 using namespace clang;
31 
32 namespace {
33 
34 /// According to Itanium C++ ABI 5.1.2:
35 /// the name of an anonymous union is considered to be
36 /// the name of the first named data member found by a pre-order,
37 /// depth-first, declaration-order walk of the data members of
38 /// the anonymous union.
39 /// If there is no such data member (i.e., if all of the data members
40 /// in the union are unnamed), then there is no way for a program to
41 /// refer to the anonymous union, and there is therefore no need to mangle its name.
42 ///
43 /// Returns the name of anonymous union VarDecl or nullptr if it is not found.
44 static const IdentifierInfo *findAnonymousUnionVarDeclName(const VarDecl& VD) {
45  const RecordType *RT = VD.getType()->getAs<RecordType>();
46  assert(RT && "type of VarDecl is expected to be RecordType.");
47  assert(RT->getDecl()->isUnion() && "RecordType is expected to be a union.");
48  if (const FieldDecl *FD = RT->getDecl()->findFirstNamedDataMember()) {
49  return FD->getIdentifier();
50  }
51 
52  return nullptr;
53 }
54 
55 /// The name of a decomposition declaration.
56 struct DecompositionDeclName {
57  using BindingArray = ArrayRef<const BindingDecl*>;
58 
59  /// Representative example of a set of bindings with these names.
60  BindingArray Bindings;
61 
62  /// Iterators over the sequence of identifiers in the name.
63  struct Iterator
64  : llvm::iterator_adaptor_base<Iterator, BindingArray::const_iterator,
65  std::random_access_iterator_tag,
66  const IdentifierInfo *> {
67  Iterator(BindingArray::const_iterator It) : iterator_adaptor_base(It) {}
68  const IdentifierInfo *operator*() const {
69  return (*this->I)->getIdentifier();
70  }
71  };
72  Iterator begin() const { return Iterator(Bindings.begin()); }
73  Iterator end() const { return Iterator(Bindings.end()); }
74 };
75 }
76 
77 namespace llvm {
78 template<typename T> bool isDenseMapKeyEmpty(T V) {
81 }
82 template<typename T> bool isDenseMapKeyTombstone(T V) {
85 }
86 
87 template<typename T>
89  bool LHSEmpty = isDenseMapKeyEmpty(LHS);
90  bool RHSEmpty = isDenseMapKeyEmpty(RHS);
91  if (LHSEmpty || RHSEmpty)
92  return LHSEmpty && RHSEmpty;
93 
94  bool LHSTombstone = isDenseMapKeyTombstone(LHS);
95  bool RHSTombstone = isDenseMapKeyTombstone(RHS);
96  if (LHSTombstone || RHSTombstone)
97  return LHSTombstone && RHSTombstone;
98 
99  return None;
100 }
101 
102 template<>
103 struct DenseMapInfo<DecompositionDeclName> {
105  static DecompositionDeclName getEmptyKey() {
106  return {ArrayInfo::getEmptyKey()};
107  }
108  static DecompositionDeclName getTombstoneKey() {
109  return {ArrayInfo::getTombstoneKey()};
110  }
111  static unsigned getHashValue(DecompositionDeclName Key) {
112  assert(!isEqual(Key, getEmptyKey()) && !isEqual(Key, getTombstoneKey()));
113  return llvm::hash_combine_range(Key.begin(), Key.end());
114  }
115  static bool isEqual(DecompositionDeclName LHS, DecompositionDeclName RHS) {
117  LHS.Bindings, RHS.Bindings))
118  return *Result;
119 
120  return LHS.Bindings.size() == RHS.Bindings.size() &&
121  std::equal(LHS.begin(), LHS.end(), RHS.begin());
122  }
123 };
124 }
125 
126 namespace {
127 
128 /// Keeps track of the mangled names of lambda expressions and block
129 /// literals within a particular context.
130 class ItaniumNumberingContext : public MangleNumberingContext {
131  ItaniumMangleContext *Mangler;
132  llvm::StringMap<unsigned> LambdaManglingNumbers;
133  unsigned BlockManglingNumber = 0;
134  llvm::DenseMap<const IdentifierInfo *, unsigned> VarManglingNumbers;
135  llvm::DenseMap<const IdentifierInfo *, unsigned> TagManglingNumbers;
136  llvm::DenseMap<DecompositionDeclName, unsigned>
137  DecompsitionDeclManglingNumbers;
138 
139 public:
140  ItaniumNumberingContext(ItaniumMangleContext *Mangler) : Mangler(Mangler) {}
141 
142  unsigned getManglingNumber(const CXXMethodDecl *CallOperator) override {
143  const CXXRecordDecl *Lambda = CallOperator->getParent();
144  assert(Lambda->isLambda());
145 
146  // Computation of the <lambda-sig> is non-trivial and subtle. Rather than
147  // duplicating it here, just mangle the <lambda-sig> directly.
148  llvm::SmallString<128> LambdaSig;
149  llvm::raw_svector_ostream Out(LambdaSig);
150  Mangler->mangleLambdaSig(Lambda, Out);
151 
152  return ++LambdaManglingNumbers[LambdaSig];
153  }
154 
155  unsigned getManglingNumber(const BlockDecl *BD) override {
156  return ++BlockManglingNumber;
157  }
158 
159  unsigned getStaticLocalNumber(const VarDecl *VD) override {
160  return 0;
161  }
162 
163  /// Variable decls are numbered by identifier.
164  unsigned getManglingNumber(const VarDecl *VD, unsigned) override {
165  if (auto *DD = dyn_cast<DecompositionDecl>(VD)) {
166  DecompositionDeclName Name{DD->bindings()};
167  return ++DecompsitionDeclManglingNumbers[Name];
168  }
169 
170  const IdentifierInfo *Identifier = VD->getIdentifier();
171  if (!Identifier) {
172  // VarDecl without an identifier represents an anonymous union
173  // declaration.
174  Identifier = findAnonymousUnionVarDeclName(*VD);
175  }
176  return ++VarManglingNumbers[Identifier];
177  }
178 
179  unsigned getManglingNumber(const TagDecl *TD, unsigned) override {
180  return ++TagManglingNumbers[TD->getIdentifier()];
181  }
182 };
183 
184 class ItaniumCXXABI : public CXXABI {
185 private:
186  std::unique_ptr<MangleContext> Mangler;
187 protected:
188  ASTContext &Context;
189 public:
190  ItaniumCXXABI(ASTContext &Ctx)
191  : Mangler(Ctx.createMangleContext()), Context(Ctx) {}
192 
193  MemberPointerInfo
194  getMemberPointerInfo(const MemberPointerType *MPT) const override {
195  const TargetInfo &Target = Context.getTargetInfo();
196  TargetInfo::IntType PtrDiff = Target.getPtrDiffType(0);
197  MemberPointerInfo MPI;
198  MPI.Width = Target.getTypeWidth(PtrDiff);
199  MPI.Align = Target.getTypeAlign(PtrDiff);
200  MPI.HasPadding = false;
201  if (MPT->isMemberFunctionPointer())
202  MPI.Width *= 2;
203  return MPI;
204  }
205 
206  CallingConv getDefaultMethodCallConv(bool isVariadic) const override {
207  const llvm::Triple &T = Context.getTargetInfo().getTriple();
208  if (!isVariadic && T.isWindowsGNUEnvironment() &&
209  T.getArch() == llvm::Triple::x86)
210  return CC_X86ThisCall;
211  return Context.getTargetInfo().getDefaultCallingConv();
212  }
213 
214  // We cheat and just check that the class has a vtable pointer, and that it's
215  // only big enough to have a vtable pointer and nothing more (or less).
216  bool isNearlyEmpty(const CXXRecordDecl *RD) const override {
217 
218  // Check that the class has a vtable pointer.
219  if (!RD->isDynamicClass())
220  return false;
221 
222  const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
223  CharUnits PointerSize =
224  Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(0));
225  return Layout.getNonVirtualSize() == PointerSize;
226  }
227 
228  const CXXConstructorDecl *
229  getCopyConstructorForExceptionObject(CXXRecordDecl *RD) override {
230  return nullptr;
231  }
232 
233  void addCopyConstructorForExceptionObject(CXXRecordDecl *RD,
234  CXXConstructorDecl *CD) override {}
235 
236  void addTypedefNameForUnnamedTagDecl(TagDecl *TD,
237  TypedefNameDecl *DD) override {}
238 
239  TypedefNameDecl *getTypedefNameForUnnamedTagDecl(const TagDecl *TD) override {
240  return nullptr;
241  }
242 
243  void addDeclaratorForUnnamedTagDecl(TagDecl *TD,
244  DeclaratorDecl *DD) override {}
245 
246  DeclaratorDecl *getDeclaratorForUnnamedTagDecl(const TagDecl *TD) override {
247  return nullptr;
248  }
249 
250  std::unique_ptr<MangleNumberingContext>
251  createMangleNumberingContext() const override {
252  return std::make_unique<ItaniumNumberingContext>(
253  cast<ItaniumMangleContext>(Mangler.get()));
254  }
255 };
256 }
257 
259  return new ItaniumCXXABI(Ctx);
260 }
Defines the clang::ASTContext interface.
unsigned getTypeWidth(IntType T) const
Return the width (in bits) of the specified integer type enum.
Definition: TargetInfo.cpp:219
StringRef Identifier
Definition: Format.cpp:1815
MangleContext * createMangleContext(const TargetInfo *T=nullptr)
If T is null pointer, assume the target in ASTContext.
Specialize PointerLikeTypeTraits to allow LazyGenerationalUpdatePtr to be placed into a PointerUnion...
Definition: Dominators.h:30
const ASTRecordLayout & getASTRecordLayout(const RecordDecl *D) const
Get or compute information about the layout of the specified record (struct/union/class) D...
const llvm::Triple & getTriple() const
Returns the target triple of the primary target.
Definition: TargetInfo.h:991
C Language Family Type Representation.
Optional< bool > areDenseMapKeysEqualSpecialValues(T LHS, T RHS)
const TargetInfo & getTargetInfo() const
Definition: ASTContext.h:706
Represents a C++ constructor within a class.
Definition: DeclCXX.h:2365
Represents a variable declaration or definition.
Definition: Decl.h:827
const T * getAs() const
Member-template getAs<specific type>&#39;.
Definition: Type.h:6858
IdentifierInfo * getIdentifier() const
Get the identifier that names this declaration, if there is one.
Definition: Decl.h:269
virtual void mangleLambdaSig(const CXXRecordDecl *Lambda, raw_ostream &)=0
uint64_t getPointerWidth(unsigned AddrSpace) const
Return the width of pointers on this target, for the specified address space.
Definition: TargetInfo.h:360
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:160
Represents a member of a struct/union/class.
Definition: Decl.h:2643
static DecompositionDeclName getTombstoneKey()
clang::CharUnits operator*(clang::CharUnits::QuantityType Scale, const clang::CharUnits &CU)
Definition: CharUnits.h:212
static bool isEqual(DecompositionDeclName LHS, DecompositionDeclName RHS)
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...
bool isLambda() const
Determine whether this class describes a lambda function object.
Definition: DeclCXX.h:962
bool isDenseMapKeyTombstone(T V)
CXXABI * CreateItaniumCXXABI(ASTContext &Ctx)
Creates an instance of a C++ ABI class.
static unsigned getHashValue(DecompositionDeclName Key)
bool isDynamicClass() const
Definition: DeclCXX.h:555
Represents a ValueDecl that came out of a declarator.
Definition: Decl.h:696
ASTRecordLayout - This class contains layout information for one RecordDecl, which is a struct/union/...
Definition: RecordLayout.h:38
Exposes information about the current target.
Definition: TargetInfo.h:163
Represents a block literal declaration, which is like an unnamed FunctionDecl.
Definition: Decl.h:3951
const FieldDecl * findFirstNamedDataMember() const
Finds the first data member which has a name.
Definition: Decl.cpp:4435
virtual CallingConv getDefaultCallingConv() const
Gets the default calling convention for the given target and declaration context. ...
Definition: TargetInfo.h:1260
#define V(N, I)
Definition: ASTContext.h:2921
static DecompositionDeclName getEmptyKey()
Implements C++ ABI-specific semantic analysis functions.
Definition: CXXABI.h:29
The result type of a method or function.
CallingConv
CallingConv - Specifies the calling convention that a function uses.
Definition: Specifiers.h:265
unsigned getTypeAlign(IntType T) const
Return the alignment (in bits) of the specified integer type enum.
Definition: TargetInfo.cpp:290
RecordDecl * getDecl() const
Definition: Type.h:4454
IntType getPtrDiffType(unsigned AddrSpace) const
Definition: TargetInfo.h:289
Represents the declaration of a struct/union/class/enum.
Definition: Decl.h:3133
Represents a static or instance method of a struct/union/class.
Definition: DeclCXX.h:1905
IntType
===-— Target Data Type Query Methods ----------------------------—===//
Definition: TargetInfo.h:106
Base class for declarations which introduce a typedef-name.
Definition: Decl.h:2985
Dataflow Directional Tag Classes.
const CXXRecordDecl * getParent() const
Return the parent of this method declaration, which is the class in which this method is defined...
Definition: DeclCXX.h:2028
A pointer to member type per C++ 8.3.3 - Pointers to members.
Definition: Type.h:2804
A helper class that allows the use of isa/cast/dyncast to detect TagType objects of structs/unions/cl...
Definition: Type.h:4444
CharUnits toCharUnitsFromBits(int64_t BitSize) const
Convert a size in bits to a size in characters.
Defines the C++ Decl subclasses, other than those for templates (found in DeclTemplate.h) and friends (in DeclFriend.h).
Represents a C++ struct/union/class.
Definition: DeclCXX.h:255
bool isMemberFunctionPointer() const
Returns true if the member type (i.e.
Definition: Type.h:2828
CharUnits getNonVirtualSize() const
getNonVirtualSize - Get the non-virtual size (in chars) of an object, which is the size of the object...
Definition: RecordLayout.h:202
Defines the clang::TargetInfo interface.
bool isDenseMapKeyEmpty(T V)
bool isUnion() const
Definition: Decl.h:3321
QualType getType() const
Definition: Decl.h:655