1//===- PostOrderCFGView.h - Post order view of CFG blocks -------*- 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 implements post order view of the blocks in a CFG.
10//
11//===----------------------------------------------------------------------===//
12
13#ifndef LLVM_CLANG_ANALYSIS_ANALYSES_POSTORDERCFGVIEW_H
14#define LLVM_CLANG_ANALYSIS_ANALYSES_POSTORDERCFGVIEW_H
15
16#include "clang/Analysis/AnalysisDeclContext.h"
17#include "clang/Analysis/CFG.h"
18#include "clang/Basic/LLVM.h"
19#include "llvm/ADT/BitVector.h"
20#include "llvm/ADT/DenseMap.h"
21#include "llvm/ADT/None.h"
22#include "llvm/ADT/PostOrderIterator.h"
23#include <utility>
24#include <vector>
25
26namespace clang {
27
28class PostOrderCFGView : public ManagedAnalysis {
29  virtual void anchor();
30
31public:
32  /// Implements a set of CFGBlocks using a BitVector.
33  ///
34  /// This class contains a minimal interface, primarily dictated by the SetType
35  /// template parameter of the llvm::po_iterator template, as used with
36  /// external storage. We also use this set to keep track of which CFGBlocks we
37  /// visit during the analysis.
38  class CFGBlockSet {
39    llvm::BitVector VisitedBlockIDs;
40
41  public:
42    // po_iterator requires this iterator, but the only interface needed is the
43    // value_type type.
44    struct iterator { using value_type = const CFGBlock *; };
45
46    CFGBlockSet() = default;
47    CFGBlockSet(const CFG *G) : VisitedBlockIDs(G->getNumBlockIDs(), false) {}
48
49    /// Set the bit associated with a particular CFGBlock.
50    /// This is the important method for the SetType template parameter.
51    std::pair<llvm::NoneType, bool> insert(const CFGBlock *Block) {
52      // Note that insert() is called by po_iterator, which doesn't check to
53      // make sure that Block is non-null.  Moreover, the CFGBlock iterator will
54      // occasionally hand out null pointers for pruned edges, so we catch those
55      // here.
56      if (!Block)
57        return std::make_pair(None, false); // if an edge is trivially false.
58      if (VisitedBlockIDs.test(Block->getBlockID()))
59        return std::make_pair(None, false);
60      VisitedBlockIDs.set(Block->getBlockID());
61      return std::make_pair(None, true);
62    }
63
64    /// Check if the bit for a CFGBlock has been already set.
65    /// This method is for tracking visited blocks in the main threadsafety
66    /// loop. Block must not be null.
67    bool alreadySet(const CFGBlock *Block) {
68      return VisitedBlockIDs.test(Block->getBlockID());
69    }
70  };
71
72private:
73  using po_iterator = llvm::po_iterator<const CFG *, CFGBlockSet, true>;
74  std::vector<const CFGBlock *> Blocks;
75
76  using BlockOrderTy = llvm::DenseMap<const CFGBlock *, unsigned>;
77  BlockOrderTy BlockOrder;
78
79public:
80  friend struct BlockOrderCompare;
81
82  using iterator = std::vector<const CFGBlock *>::reverse_iterator;
83  using const_iterator = std::vector<const CFGBlock *>::const_reverse_iterator;
84
85  PostOrderCFGView(const CFG *cfg);
86
87  iterator begin() { return Blocks.rbegin(); }
88  iterator end() { return Blocks.rend(); }
89
90  const_iterator begin() const { return Blocks.rbegin(); }
91  const_iterator end() const { return Blocks.rend(); }
92
93  bool empty() const { return begin() == end(); }
94
95  struct BlockOrderCompare {
96    const PostOrderCFGView &POV;
97
98  public:
99    BlockOrderCompare(const PostOrderCFGView &pov) : POV(pov) {}
100
101    bool operator()(const CFGBlock *b1, const CFGBlock *b2) const;
102  };
103
104  BlockOrderCompare getComparator() const {
105    return BlockOrderCompare(*this);
106  }
107
108  // Used by AnalyisContext to construct this object.
109  static const void *getTag();
110
111  static PostOrderCFGView *create(AnalysisDeclContext &analysisContext);
112};
113
114} // namespace clang
115
116#endif // LLVM_CLANG_ANALYSIS_ANALYSES_POSTORDERCFGVIEW_H
117