1 //===-- ODRHash.cpp - Hashing to diagnose ODR failures ----------*- 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 /// \file
11 /// This file implements the ODRHash class, which calculates a hash based
12 /// on AST nodes, which is stable across different runs.
13 ///
14 //===----------------------------------------------------------------------===//
15 
16 #include "clang/AST/ODRHash.h"
17 
18 #include "clang/AST/DeclVisitor.h"
19 #include "clang/AST/NestedNameSpecifier.h"
20 #include "clang/AST/StmtVisitor.h"
21 #include "clang/AST/TypeVisitor.h"
22 
23 using namespace clang;
24 
25 void ODRHash::AddStmt(const Stmt *S) {
26   assert(S && "Expecting non-null pointer.");
27   S->ProcessODRHash(ID, *this);
28 }
29 
30 void ODRHash::AddIdentifierInfo(const IdentifierInfo *II) {
31   assert(II && "Expecting non-null pointer.");
32   ID.AddString(II->getName());
33 }
34 
35 void ODRHash::AddDeclarationName(DeclarationName Name) {
36   AddBoolean(Name.isEmpty());
37   if (Name.isEmpty())
38     return;
39 
40   auto Kind = Name.getNameKind();
41   ID.AddInteger(Kind);
42   switch (Kind) {
43   case DeclarationName::Identifier:
44     AddIdentifierInfo(Name.getAsIdentifierInfo());
45     break;
46   case DeclarationName::ObjCZeroArgSelector:
47   case DeclarationName::ObjCOneArgSelector:
48   case DeclarationName::ObjCMultiArgSelector: {
49     Selector S = Name.getObjCSelector();
50     AddBoolean(S.isNull());
51     AddBoolean(S.isKeywordSelector());
52     AddBoolean(S.isUnarySelector());
53     unsigned NumArgs = S.getNumArgs();
54     for (unsigned i = 0; i < NumArgs; ++i) {
55       AddIdentifierInfo(S.getIdentifierInfoForSlot(i));
56     }
57     break;
58   }
59   case DeclarationName::CXXConstructorName:
60   case DeclarationName::CXXDestructorName:
61     AddQualType(Name.getCXXNameType());
62     break;
63   case DeclarationName::CXXOperatorName:
64     ID.AddInteger(Name.getCXXOverloadedOperator());
65     break;
66   case DeclarationName::CXXLiteralOperatorName:
67     AddIdentifierInfo(Name.getCXXLiteralIdentifier());
68     break;
69   case DeclarationName::CXXConversionFunctionName:
70     AddQualType(Name.getCXXNameType());
71     break;
72   case DeclarationName::CXXUsingDirective:
73     break;
74   case DeclarationName::CXXDeductionGuideName: {
75     auto *Template = Name.getCXXDeductionGuideTemplate();
76     AddBoolean(Template);
77     if (Template) {
78       AddDecl(Template);
79     }
80   }
81   }
82 }
83 
84 void ODRHash::AddNestedNameSpecifier(const NestedNameSpecifier *NNS) {}
85 void ODRHash::AddTemplateName(TemplateName Name) {}
86 void ODRHash::AddTemplateArgument(TemplateArgument TA) {}
87 void ODRHash::AddTemplateParameterList(const TemplateParameterList *TPL) {}
88 
89 void ODRHash::clear() {
90   DeclMap.clear();
91   TypeMap.clear();
92   Bools.clear();
93   ID.clear();
94 }
95 
96 unsigned ODRHash::CalculateHash() {
97   // Append the bools to the end of the data segment backwards.  This allows
98   // for the bools data to be compressed 32 times smaller compared to using
99   // ID.AddBoolean
100   const unsigned unsigned_bits = sizeof(unsigned) * CHAR_BIT;
101   const unsigned size = Bools.size();
102   const unsigned remainder = size % unsigned_bits;
103   const unsigned loops = size / unsigned_bits;
104   auto I = Bools.rbegin();
105   unsigned value = 0;
106   for (unsigned i = 0; i < remainder; ++i) {
107     value <<= 1;
108     value |= *I;
109     ++I;
110   }
111   ID.AddInteger(value);
112 
113   for (unsigned i = 0; i < loops; ++i) {
114     value = 0;
115     for (unsigned j = 0; j < unsigned_bits; ++j) {
116       value <<= 1;
117       value |= *I;
118       ++I;
119     }
120     ID.AddInteger(value);
121   }
122 
123   assert(I == Bools.rend());
124   Bools.clear();
125   return ID.ComputeHash();
126 }
127 
128 // Process a Decl pointer.  Add* methods call back into ODRHash while Visit*
129 // methods process the relevant parts of the Decl.
130 class ODRDeclVisitor : public ConstDeclVisitor<ODRDeclVisitor> {
131   typedef ConstDeclVisitor<ODRDeclVisitor> Inherited;
132   llvm::FoldingSetNodeID &ID;
133   ODRHash &Hash;
134 
135 public:
136   ODRDeclVisitor(llvm::FoldingSetNodeID &ID, ODRHash &Hash)
137       : ID(ID), Hash(Hash) {}
138 
139   void AddStmt(const Stmt *S) {
140     Hash.AddBoolean(S);
141     if (S) {
142       Hash.AddStmt(S);
143     }
144   }
145 
146   void AddIdentifierInfo(const IdentifierInfo *II) {
147     Hash.AddBoolean(II);
148     if (II) {
149       Hash.AddIdentifierInfo(II);
150     }
151   }
152 
153   void AddQualType(QualType T) {
154     Hash.AddQualType(T);
155   }
156 
157   void Visit(const Decl *D) {
158     ID.AddInteger(D->getKind());
159     Inherited::Visit(D);
160   }
161 
162   void VisitNamedDecl(const NamedDecl *D) {
163     AddIdentifierInfo(D->getIdentifier());
164     Inherited::VisitNamedDecl(D);
165   }
166 
167   void VisitValueDecl(const ValueDecl *D) {
168     AddQualType(D->getType());
169     Inherited::VisitValueDecl(D);
170   }
171 
172   void VisitAccessSpecDecl(const AccessSpecDecl *D) {
173     ID.AddInteger(D->getAccess());
174     Inherited::VisitAccessSpecDecl(D);
175   }
176 
177   void VisitStaticAssertDecl(const StaticAssertDecl *D) {
178     AddStmt(D->getAssertExpr());
179     AddStmt(D->getMessage());
180 
181     Inherited::VisitStaticAssertDecl(D);
182   }
183 
184   void VisitFieldDecl(const FieldDecl *D) {
185     const bool IsBitfield = D->isBitField();
186     Hash.AddBoolean(IsBitfield);
187 
188     if (IsBitfield) {
189       AddStmt(D->getBitWidth());
190     }
191 
192     Hash.AddBoolean(D->isMutable());
193     AddStmt(D->getInClassInitializer());
194 
195     Inherited::VisitFieldDecl(D);
196   }
197 
198   void VisitFunctionDecl(const FunctionDecl *D) {
199     Inherited::VisitFunctionDecl(D);
200   }
201 
202   void VisitCXXMethodDecl(const CXXMethodDecl *D) {
203     Inherited::VisitCXXMethodDecl(D);
204   }
205 };
206 
207 // Only allow a small portion of Decl's to be processed.  Remove this once
208 // all Decl's can be handled.
209 bool ODRHash::isWhitelistedDecl(const Decl *D, const CXXRecordDecl *Parent) {
210   if (D->isImplicit()) return false;
211   if (D->getDeclContext() != Parent) return false;
212 
213   switch (D->getKind()) {
214     default:
215       return false;
216     case Decl::AccessSpec:
217     case Decl::CXXMethod:
218     case Decl::Field:
219     case Decl::StaticAssert:
220       return true;
221   }
222 }
223 
224 void ODRHash::AddSubDecl(const Decl *D) {
225   assert(D && "Expecting non-null pointer.");
226   AddDecl(D);
227 
228   ODRDeclVisitor(ID, *this).Visit(D);
229 }
230 
231 void ODRHash::AddCXXRecordDecl(const CXXRecordDecl *Record) {
232   assert(Record && Record->hasDefinition() &&
233          "Expected non-null record to be a definition.");
234   AddDecl(Record);
235 
236   // Filter out sub-Decls which will not be processed in order to get an
237   // accurate count of Decl's.
238   llvm::SmallVector<const Decl *, 16> Decls;
239   for (const Decl *SubDecl : Record->decls()) {
240     if (isWhitelistedDecl(SubDecl, Record)) {
241       Decls.push_back(SubDecl);
242     }
243   }
244 
245   ID.AddInteger(Decls.size());
246   for (auto SubDecl : Decls) {
247     AddSubDecl(SubDecl);
248   }
249 }
250 
251 void ODRHash::AddDecl(const Decl *D) {
252   assert(D && "Expecting non-null pointer.");
253   auto Result = DeclMap.insert(std::make_pair(D, DeclMap.size()));
254   ID.AddInteger(Result.first->second);
255   // On first encounter of a Decl pointer, process it.  Every time afterwards,
256   // only the index value is needed.
257   if (!Result.second) {
258     return;
259   }
260 
261   ID.AddInteger(D->getKind());
262 
263   if (const NamedDecl *ND = dyn_cast<NamedDecl>(D)) {
264     AddDeclarationName(ND->getDeclName());
265   }
266 }
267 
268 // Process a Type pointer.  Add* methods call back into ODRHash while Visit*
269 // methods process the relevant parts of the Type.
270 class ODRTypeVisitor : public TypeVisitor<ODRTypeVisitor> {
271   typedef TypeVisitor<ODRTypeVisitor> Inherited;
272   llvm::FoldingSetNodeID &ID;
273   ODRHash &Hash;
274 
275 public:
276   ODRTypeVisitor(llvm::FoldingSetNodeID &ID, ODRHash &Hash)
277       : ID(ID), Hash(Hash) {}
278 
279   void AddStmt(Stmt *S) {
280     Hash.AddBoolean(S);
281     if (S) {
282       Hash.AddStmt(S);
283     }
284   }
285 
286   void AddDecl(Decl *D) {
287     Hash.AddBoolean(D);
288     if (D) {
289       Hash.AddDecl(D);
290     }
291   }
292 
293   void Visit(const Type *T) {
294     ID.AddInteger(T->getTypeClass());
295     Inherited::Visit(T);
296   }
297 
298   void VisitType(const Type *T) {}
299 
300   void VisitBuiltinType(const BuiltinType *T) {
301     ID.AddInteger(T->getKind());
302     VisitType(T);
303   }
304 
305   void VisitTypedefType(const TypedefType *T) {
306     AddDecl(T->getDecl());
307     VisitType(T);
308   }
309 };
310 
311 void ODRHash::AddType(const Type *T) {
312   assert(T && "Expecting non-null pointer.");
313   auto Result = TypeMap.insert(std::make_pair(T, TypeMap.size()));
314   ID.AddInteger(Result.first->second);
315   // On first encounter of a Type pointer, process it.  Every time afterwards,
316   // only the index value is needed.
317   if (!Result.second) {
318     return;
319   }
320 
321   ODRTypeVisitor(ID, *this).Visit(T);
322 }
323 
324 void ODRHash::AddQualType(QualType T) {
325   AddBoolean(T.isNull());
326   if (T.isNull())
327     return;
328   SplitQualType split = T.split();
329   ID.AddInteger(split.Quals.getAsOpaqueValue());
330   AddType(split.Ty);
331 }
332 
333 void ODRHash::AddBoolean(bool Value) {
334   Bools.push_back(Value);
335 }
336