ASTImporterLookupTable.h revision 1.1.1.1 
1//===- ASTImporterLookupTable.h - ASTImporter specific lookup--*- C++ -*---===//
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 file defines the ASTImporterLookupTable class which implements a
10//  lookup procedure for the import mechanism.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_CLANG_AST_ASTIMPORTERLOOKUPTABLE_H
15#define LLVM_CLANG_AST_ASTIMPORTERLOOKUPTABLE_H
16
17#include "clang/AST/DeclBase.h" // lookup_result
18#include "clang/AST/DeclarationName.h"
19#include "llvm/ADT/DenseMap.h"
20#include "llvm/ADT/SetVector.h"
21
22namespace clang {
23
24class ASTContext;
25class NamedDecl;
26class DeclContext;
27
28// There are certain cases when normal C/C++ lookup (localUncachedLookup)
29// does not find AST nodes. E.g.:
30// Example 1:
31//   template <class T>
32//   struct X {
33//     friend void foo(); // this is never found in the DC of the TU.
34//   };
35// Example 2:
36//   // The fwd decl to Foo is not found in the lookupPtr of the DC of the
37//   // translation unit decl.
38//   // Here we could find the node by doing a traverse throught the list of
39//   // the Decls in the DC, but that would not scale.
40//   struct A { struct Foo *p; };
41// This is a severe problem because the importer decides if it has to create a
42// new Decl or not based on the lookup results.
43// To overcome these cases we need an importer specific lookup table which
44// holds every node and we are not interested in any C/C++ specific visibility
45// considerations. Simply, we must know if there is an existing Decl in a
46// given DC. Once we found it then we can handle any visibility related tasks.
47class ASTImporterLookupTable {
48
49  // We store a list of declarations for each name.
50  // And we collect these lists for each DeclContext.
51  // We could have a flat map with (DeclContext, Name) tuple as key, but a two
52  // level map seems easier to handle.
53  using DeclList = llvm::SmallSetVector<NamedDecl *, 2>;
54  using NameMap = llvm::SmallDenseMap<DeclarationName, DeclList, 4>;
55  using DCMap = llvm::DenseMap<DeclContext *, NameMap>;
56
57  void add(DeclContext *DC, NamedDecl *ND);
58  void remove(DeclContext *DC, NamedDecl *ND);
59
60  DCMap LookupTable;
61
62public:
63  ASTImporterLookupTable(TranslationUnitDecl &TU);
64  void add(NamedDecl *ND);
65  void remove(NamedDecl *ND);
66  using LookupResult = DeclList;
67  LookupResult lookup(DeclContext *DC, DeclarationName Name) const;
68  void dump(DeclContext *DC) const;
69  void dump() const;
70};
71
72} // namespace clang
73
74#endif // LLVM_CLANG_AST_ASTIMPORTERLOOKUPTABLE_H
75