1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
| //===- llvm/ADT/BreadthFirstIterator.h - Breadth First iterator -*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file builds on the ADT/GraphTraits.h file to build a generic breadth
// first graph iterator. This file exposes the following functions/types:
//
// bf_begin/bf_end/bf_iterator
// * Normal breadth-first iteration - visit a graph level-by-level.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ADT_BREADTHFIRSTITERATOR_H
#define LLVM_ADT_BREADTHFIRSTITERATOR_H
#include "llvm/ADT/GraphTraits.h"
#include "llvm/ADT/None.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/iterator_range.h"
#include <iterator>
#include <queue>
#include <utility>
namespace llvm {
// bf_iterator_storage - A private class which is used to figure out where to
// store the visited set. We only provide a non-external variant for now.
template <class SetType> class bf_iterator_storage {
public:
SetType Visited;
};
// The visited state for the iteration is a simple set.
template <typename NodeRef, unsigned SmallSize = 8>
using bf_iterator_default_set = SmallPtrSet<NodeRef, SmallSize>;
// Generic Breadth first search iterator.
template <class GraphT,
class SetType =
bf_iterator_default_set<typename GraphTraits<GraphT>::NodeRef>,
class GT = GraphTraits<GraphT>>
class bf_iterator
: public std::iterator<std::forward_iterator_tag, typename GT::NodeRef>,
public bf_iterator_storage<SetType> {
using super = std::iterator<std::forward_iterator_tag, typename GT::NodeRef>;
using NodeRef = typename GT::NodeRef;
using ChildItTy = typename GT::ChildIteratorType;
// First element is the node reference, second is the next child to visit.
using QueueElement = std::pair<NodeRef, Optional<ChildItTy>>;
// Visit queue - used to maintain BFS ordering.
// Optional<> because we need markers for levels.
std::queue<Optional<QueueElement>> VisitQueue;
// Current level.
unsigned Level;
private:
inline bf_iterator(NodeRef Node) {
this->Visited.insert(Node);
Level = 0;
// Also, insert a dummy node as marker.
VisitQueue.push(QueueElement(Node, None));
VisitQueue.push(None);
}
inline bf_iterator() = default;
inline void toNext() {
Optional<QueueElement> Head = VisitQueue.front();
QueueElement H = Head.getValue();
NodeRef Node = H.first;
Optional<ChildItTy> &ChildIt = H.second;
if (!ChildIt)
ChildIt.emplace(GT::child_begin(Node));
while (*ChildIt != GT::child_end(Node)) {
NodeRef Next = *(*ChildIt)++;
// Already visited?
if (this->Visited.insert(Next).second)
VisitQueue.push(QueueElement(Next, None));
}
VisitQueue.pop();
// Go to the next element skipping markers if needed.
if (!VisitQueue.empty()) {
Head = VisitQueue.front();
if (Head != None)
return;
Level += 1;
VisitQueue.pop();
// Don't push another marker if this is the last
// element.
if (!VisitQueue.empty())
VisitQueue.push(None);
}
}
public:
using pointer = typename super::pointer;
// Provide static begin and end methods as our public "constructors"
static bf_iterator begin(const GraphT &G) {
return bf_iterator(GT::getEntryNode(G));
}
static bf_iterator end(const GraphT &G) { return bf_iterator(); }
bool operator==(const bf_iterator &RHS) const {
return VisitQueue == RHS.VisitQueue;
}
bool operator!=(const bf_iterator &RHS) const { return !(*this == RHS); }
const NodeRef &operator*() const { return VisitQueue.front()->first; }
// This is a nonstandard operator-> that dereferences the pointer an extra
// time so that you can actually call methods on the node, because the
// contained type is a pointer.
NodeRef operator->() const { return **this; }
bf_iterator &operator++() { // Pre-increment
toNext();
return *this;
}
bf_iterator operator++(int) { // Post-increment
bf_iterator ItCopy = *this;
++*this;
return ItCopy;
}
unsigned getLevel() const { return Level; }
};
// Provide global constructors that automatically figure out correct types.
template <class T> bf_iterator<T> bf_begin(const T &G) {
return bf_iterator<T>::begin(G);
}
template <class T> bf_iterator<T> bf_end(const T &G) {
return bf_iterator<T>::end(G);
}
// Provide an accessor method to use them in range-based patterns.
template <class T> iterator_range<bf_iterator<T>> breadth_first(const T &G) {
return make_range(bf_begin(G), bf_end(G));
}
} // end namespace llvm
#endif // LLVM_ADT_BREADTHFIRSTITERATOR_H
|