1 //===- ParentMapContext.h - Map of parents using DynTypedNode -------*- 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 // Similar to ParentMap.h, but generalizes to non-Stmt nodes, which can have
10 // multiple parents.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_CLANG_AST_PARENTMAPCONTEXT_H
15 #define LLVM_CLANG_AST_PARENTMAPCONTEXT_H
16 
17 #include "clang/AST/ASTContext.h"
18 #include "clang/AST/ASTTypeTraits.h"
19 
20 namespace clang {
21 class DynTypedNodeList;
22 
23 class ParentMapContext {
24 public:
25   ParentMapContext(ASTContext &Ctx);
26 
27   ~ParentMapContext();
28 
29   /// Returns the parents of the given node (within the traversal scope).
30   ///
31   /// Note that this will lazily compute the parents of all nodes
32   /// and store them for later retrieval. Thus, the first call is O(n)
33   /// in the number of AST nodes.
34   ///
35   /// Caveats and FIXMEs:
36   /// Calculating the parent map over all AST nodes will need to load the
37   /// full AST. This can be undesirable in the case where the full AST is
38   /// expensive to create (for example, when using precompiled header
39   /// preambles). Thus, there are good opportunities for optimization here.
40   /// One idea is to walk the given node downwards, looking for references
41   /// to declaration contexts - once a declaration context is found, compute
42   /// the parent map for the declaration context; if that can satisfy the
43   /// request, loading the whole AST can be avoided. Note that this is made
44   /// more complex by statements in templates having multiple parents - those
45   /// problems can be solved by building closure over the templated parts of
46   /// the AST, which also avoids touching large parts of the AST.
47   /// Additionally, we will want to add an interface to already give a hint
48   /// where to search for the parents, for example when looking at a statement
49   /// inside a certain function.
50   ///
51   /// 'NodeT' can be one of Decl, Stmt, Type, TypeLoc,
52   /// NestedNameSpecifier or NestedNameSpecifierLoc.
53   template <typename NodeT> DynTypedNodeList getParents(const NodeT &Node);
54 
55   DynTypedNodeList getParents(const DynTypedNode &Node);
56 
57   /// Clear parent maps.
58   void clear();
59 
getTraversalKind()60   TraversalKind getTraversalKind() const { return Traversal; }
setTraversalKind(TraversalKind TK)61   void setTraversalKind(TraversalKind TK) { Traversal = TK; }
62 
63   const Expr *traverseIgnored(const Expr *E) const;
64   Expr *traverseIgnored(Expr *E) const;
65   DynTypedNode traverseIgnored(const DynTypedNode &N) const;
66 
67   class ParentMap;
68 
69 private:
70   ASTContext &ASTCtx;
71   TraversalKind Traversal = TK_AsIs;
72   std::unique_ptr<ParentMap> Parents;
73 };
74 
75 class TraversalKindScope {
76   ParentMapContext &Ctx;
77   TraversalKind TK = TK_AsIs;
78 
79 public:
TraversalKindScope(ASTContext & ASTCtx,std::optional<TraversalKind> ScopeTK)80   TraversalKindScope(ASTContext &ASTCtx, std::optional<TraversalKind> ScopeTK)
81       : Ctx(ASTCtx.getParentMapContext()) {
82     TK = Ctx.getTraversalKind();
83     if (ScopeTK)
84       Ctx.setTraversalKind(*ScopeTK);
85   }
86 
~TraversalKindScope()87   ~TraversalKindScope() { Ctx.setTraversalKind(TK); }
88 };
89 
90 /// Container for either a single DynTypedNode or for an ArrayRef to
91 /// DynTypedNode. For use with ParentMap.
92 class DynTypedNodeList {
93   union {
94     DynTypedNode SingleNode;
95     ArrayRef<DynTypedNode> Nodes;
96   };
97   bool IsSingleNode;
98 
99 public:
DynTypedNodeList(const DynTypedNode & N)100   DynTypedNodeList(const DynTypedNode &N) : IsSingleNode(true) {
101     new (&SingleNode) DynTypedNode(N);
102   }
103 
DynTypedNodeList(ArrayRef<DynTypedNode> A)104   DynTypedNodeList(ArrayRef<DynTypedNode> A) : IsSingleNode(false) {
105     new (&Nodes) ArrayRef<DynTypedNode>(A);
106   }
107 
begin()108   const DynTypedNode *begin() const {
109     return !IsSingleNode ? Nodes.begin() : &SingleNode;
110   }
111 
end()112   const DynTypedNode *end() const {
113     return !IsSingleNode ? Nodes.end() : &SingleNode + 1;
114   }
115 
size()116   size_t size() const { return end() - begin(); }
empty()117   bool empty() const { return begin() == end(); }
118 
119   const DynTypedNode &operator[](size_t N) const {
120     assert(N < size() && "Out of bounds!");
121     return *(begin() + N);
122   }
123 };
124 
125 template <typename NodeT>
getParents(const NodeT & Node)126 inline DynTypedNodeList ParentMapContext::getParents(const NodeT &Node) {
127   return getParents(DynTypedNode::create(Node));
128 }
129 
130 template <typename NodeT>
getParents(const NodeT & Node)131 inline DynTypedNodeList ASTContext::getParents(const NodeT &Node) {
132   return getParentMapContext().getParents(Node);
133 }
134 
135 template <>
getParents(const DynTypedNode & Node)136 inline DynTypedNodeList ASTContext::getParents(const DynTypedNode &Node) {
137   return getParentMapContext().getParents(Node);
138 }
139 
140 } // namespace clang
141 
142 #endif
143