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"
23#include "clang/AST/MangleNumberingContext.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#include <optional>
30
31using namespace clang;
32
33namespace {
34
35/// According to Itanium C++ ABI 5.1.2:
36/// the name of an anonymous union is considered to be
37/// the name of the first named data member found by a pre-order,
38/// depth-first, declaration-order walk of the data members of
39/// the anonymous union.
40/// If there is no such data member (i.e., if all of the data members
41/// in the union are unnamed), then there is no way for a program to
42/// refer to the anonymous union, and there is therefore no need to mangle its name.
43///
44/// Returns the name of anonymous union VarDecl or nullptr if it is not found.
45static const IdentifierInfo *findAnonymousUnionVarDeclName(const VarDecl& VD) {
46 const RecordType *RT = VD.getType()->getAs<RecordType>();
47 assert(RT && "type of VarDecl is expected to be RecordType.");
48 assert(RT->getDecl()->isUnion() && "RecordType is expected to be a union.");
49 if (const FieldDecl *FD = RT->getDecl()->findFirstNamedDataMember()) {
50 return FD->getIdentifier();
51 }
52
53 return nullptr;
54}
55
56/// The name of a decomposition declaration.
57struct DecompositionDeclName {
58 using BindingArray = ArrayRef<const BindingDecl*>;
59
60 /// Representative example of a set of bindings with these names.
61 BindingArray Bindings;
62
63 /// Iterators over the sequence of identifiers in the name.
64 struct Iterator
65 : llvm::iterator_adaptor_base<Iterator, BindingArray::const_iterator,
66 std::random_access_iterator_tag,
67 const IdentifierInfo *> {
68 Iterator(BindingArray::const_iterator It) : iterator_adaptor_base(It) {}
69 const IdentifierInfo *operator*() const {
70 return (*this->I)->getIdentifier();
71 }
72 };
73 Iterator begin() const { return Iterator(Bindings.begin()); }
74 Iterator end() const { return Iterator(Bindings.end()); }
75};
76}
77
78namespace llvm {
79template<typename T> bool isDenseMapKeyEmpty(T V) {
80 return llvm::DenseMapInfo<T>::isEqual(
81 V, llvm::DenseMapInfo<T>::getEmptyKey());
82}
83template<typename T> bool isDenseMapKeyTombstone(T V) {
84 return llvm::DenseMapInfo<T>::isEqual(
85 V, llvm::DenseMapInfo<T>::getTombstoneKey());
86}
87
88template <typename T>
89std::optional<bool> areDenseMapKeysEqualSpecialValues(T LHS, T RHS) {
90 bool LHSEmpty = isDenseMapKeyEmpty(LHS);
91 bool RHSEmpty = isDenseMapKeyEmpty(RHS);
92 if (LHSEmpty || RHSEmpty)
93 return LHSEmpty && RHSEmpty;
94
95 bool LHSTombstone = isDenseMapKeyTombstone(LHS);
96 bool RHSTombstone = isDenseMapKeyTombstone(RHS);
97 if (LHSTombstone || RHSTombstone)
98 return LHSTombstone && RHSTombstone;
99
100 return std::nullopt;
101}
102
103template<>
104struct DenseMapInfo<DecompositionDeclName> {
105 using ArrayInfo = llvm::DenseMapInfo<ArrayRef<const BindingDecl*>>;
106 static DecompositionDeclName getEmptyKey() {
107 return {.Bindings: ArrayInfo::getEmptyKey()};
108 }
109 static DecompositionDeclName getTombstoneKey() {
110 return {.Bindings: ArrayInfo::getTombstoneKey()};
111 }
112 static unsigned getHashValue(DecompositionDeclName Key) {
113 assert(!isEqual(Key, getEmptyKey()) && !isEqual(Key, getTombstoneKey()));
114 return llvm::hash_combine_range(first: Key.begin(), last: Key.end());
115 }
116 static bool isEqual(DecompositionDeclName LHS, DecompositionDeclName RHS) {
117 if (std::optional<bool> Result =
118 areDenseMapKeysEqualSpecialValues(LHS: LHS.Bindings, RHS: RHS.Bindings))
119 return *Result;
120
121 return LHS.Bindings.size() == RHS.Bindings.size() &&
122 std::equal(first1: LHS.begin(), last1: LHS.end(), first2: RHS.begin());
123 }
124};
125}
126
127namespace {
128
129/// Keeps track of the mangled names of lambda expressions and block
130/// literals within a particular context.
131class ItaniumNumberingContext : public MangleNumberingContext {
132 ItaniumMangleContext *Mangler;
133 llvm::StringMap<unsigned> LambdaManglingNumbers;
134 unsigned BlockManglingNumber = 0;
135 llvm::DenseMap<const IdentifierInfo *, unsigned> VarManglingNumbers;
136 llvm::DenseMap<const IdentifierInfo *, unsigned> TagManglingNumbers;
137 llvm::DenseMap<DecompositionDeclName, unsigned>
138 DecompsitionDeclManglingNumbers;
139
140public:
141 ItaniumNumberingContext(ItaniumMangleContext *Mangler) : Mangler(Mangler) {}
142
143 unsigned getManglingNumber(const CXXMethodDecl *CallOperator) override {
144 const CXXRecordDecl *Lambda = CallOperator->getParent();
145 assert(Lambda->isLambda());
146
147 // Computation of the <lambda-sig> is non-trivial and subtle. Rather than
148 // duplicating it here, just mangle the <lambda-sig> directly.
149 llvm::SmallString<128> LambdaSig;
150 llvm::raw_svector_ostream Out(LambdaSig);
151 Mangler->mangleLambdaSig(Lambda, Out);
152
153 return ++LambdaManglingNumbers[LambdaSig];
154 }
155
156 unsigned getManglingNumber(const BlockDecl *BD) override {
157 return ++BlockManglingNumber;
158 }
159
160 unsigned getStaticLocalNumber(const VarDecl *VD) override {
161 return 0;
162 }
163
164 /// Variable decls are numbered by identifier.
165 unsigned getManglingNumber(const VarDecl *VD, unsigned) override {
166 if (auto *DD = dyn_cast<DecompositionDecl>(Val: VD)) {
167 DecompositionDeclName Name{.Bindings: DD->bindings()};
168 return ++DecompsitionDeclManglingNumbers[Name];
169 }
170
171 const IdentifierInfo *Identifier = VD->getIdentifier();
172 if (!Identifier) {
173 // VarDecl without an identifier represents an anonymous union
174 // declaration.
175 Identifier = findAnonymousUnionVarDeclName(VD: *VD);
176 }
177 return ++VarManglingNumbers[Identifier];
178 }
179
180 unsigned getManglingNumber(const TagDecl *TD, unsigned) override {
181 return ++TagManglingNumbers[TD->getIdentifier()];
182 }
183};
184
185// A version of this for SYCL that makes sure that 'device' mangling context
186// matches the lambda mangling number, so that __builtin_sycl_unique_stable_name
187// can be consistently generated between a MS and Itanium host by just referring
188// to the device mangling number.
189class ItaniumSYCLNumberingContext : public ItaniumNumberingContext {
190 llvm::DenseMap<const CXXMethodDecl *, unsigned> ManglingNumbers;
191 using ManglingItr = decltype(ManglingNumbers)::iterator;
192
193public:
194 ItaniumSYCLNumberingContext(ItaniumMangleContext *Mangler)
195 : ItaniumNumberingContext(Mangler) {}
196
197 unsigned getManglingNumber(const CXXMethodDecl *CallOperator) override {
198 unsigned Number = ItaniumNumberingContext::getManglingNumber(CallOperator);
199 std::pair<ManglingItr, bool> emplace_result =
200 ManglingNumbers.try_emplace(Key: CallOperator, Args&: Number);
201 (void)emplace_result;
202 assert(emplace_result.second && "Lambda number set multiple times?");
203 return Number;
204 }
205
206 using ItaniumNumberingContext::getManglingNumber;
207
208 unsigned getDeviceManglingNumber(const CXXMethodDecl *CallOperator) override {
209 ManglingItr Itr = ManglingNumbers.find(Val: CallOperator);
210 assert(Itr != ManglingNumbers.end() && "Lambda not yet mangled?");
211
212 return Itr->second;
213 }
214};
215
216class ItaniumCXXABI : public CXXABI {
217private:
218 std::unique_ptr<MangleContext> Mangler;
219protected:
220 ASTContext &Context;
221public:
222 ItaniumCXXABI(ASTContext &Ctx)
223 : Mangler(Ctx.createMangleContext()), Context(Ctx) {}
224
225 MemberPointerInfo
226 getMemberPointerInfo(const MemberPointerType *MPT) const override {
227 const TargetInfo &Target = Context.getTargetInfo();
228 TargetInfo::IntType PtrDiff = Target.getPtrDiffType(AddrSpace: LangAS::Default);
229 MemberPointerInfo MPI;
230 MPI.Width = Target.getTypeWidth(T: PtrDiff);
231 MPI.Align = Target.getTypeAlign(T: PtrDiff);
232 MPI.HasPadding = false;
233 if (MPT->isMemberFunctionPointer())
234 MPI.Width *= 2;
235 return MPI;
236 }
237
238 CallingConv getDefaultMethodCallConv(bool isVariadic) const override {
239 const llvm::Triple &T = Context.getTargetInfo().getTriple();
240 if (!isVariadic && T.isWindowsGNUEnvironment() &&
241 T.getArch() == llvm::Triple::x86)
242 return CC_X86ThisCall;
243 return Context.getTargetInfo().getDefaultCallingConv();
244 }
245
246 // We cheat and just check that the class has a vtable pointer, and that it's
247 // only big enough to have a vtable pointer and nothing more (or less).
248 bool isNearlyEmpty(const CXXRecordDecl *RD) const override {
249
250 // Check that the class has a vtable pointer.
251 if (!RD->isDynamicClass())
252 return false;
253
254 const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
255 CharUnits PointerSize = Context.toCharUnitsFromBits(
256 BitSize: Context.getTargetInfo().getPointerWidth(AddrSpace: LangAS::Default));
257 return Layout.getNonVirtualSize() == PointerSize;
258 }
259
260 const CXXConstructorDecl *
261 getCopyConstructorForExceptionObject(CXXRecordDecl *RD) override {
262 return nullptr;
263 }
264
265 void addCopyConstructorForExceptionObject(CXXRecordDecl *RD,
266 CXXConstructorDecl *CD) override {}
267
268 void addTypedefNameForUnnamedTagDecl(TagDecl *TD,
269 TypedefNameDecl *DD) override {}
270
271 TypedefNameDecl *getTypedefNameForUnnamedTagDecl(const TagDecl *TD) override {
272 return nullptr;
273 }
274
275 void addDeclaratorForUnnamedTagDecl(TagDecl *TD,
276 DeclaratorDecl *DD) override {}
277
278 DeclaratorDecl *getDeclaratorForUnnamedTagDecl(const TagDecl *TD) override {
279 return nullptr;
280 }
281
282 std::unique_ptr<MangleNumberingContext>
283 createMangleNumberingContext() const override {
284 if (Context.getLangOpts().isSYCL())
285 return std::make_unique<ItaniumSYCLNumberingContext>(
286 args: cast<ItaniumMangleContext>(Val: Mangler.get()));
287 return std::make_unique<ItaniumNumberingContext>(
288 args: cast<ItaniumMangleContext>(Val: Mangler.get()));
289 }
290};
291}
292
293CXXABI *clang::CreateItaniumCXXABI(ASTContext &Ctx) {
294 return new ItaniumCXXABI(Ctx);
295}
296
297std::unique_ptr<MangleNumberingContext>
298clang::createItaniumNumberingContext(MangleContext *Mangler) {
299 return std::make_unique<ItaniumNumberingContext>(
300 args: cast<ItaniumMangleContext>(Val: Mangler));
301}
302

source code of clang/lib/AST/ItaniumCXXABI.cpp