1//===- IntervalIterator.h - Interval Iterator Declaration -------*- 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// This file defines an iterator that enumerates the intervals in a control flow
11// graph of some sort.  This iterator is parametric, allowing iterator over the
12// following types of graphs:
13//
14//  1. A Function* object, composed of BasicBlock nodes.
15//  2. An IntervalPartition& object, composed of Interval nodes.
16//
17// This iterator is defined to walk the control flow graph, returning intervals
18// in depth first order.  These intervals are completely filled in except for
19// the predecessor fields (the successor information is filled in however).
20//
21// By default, the intervals created by this iterator are deleted after they
22// are no longer any use to the iterator.  This behavior can be changed by
23// passing a false value into the intervals_begin() function. This causes the
24// IOwnMem member to be set, and the intervals to not be deleted.
25//
26// It is only safe to use this if all of the intervals are deleted by the caller
27// and all of the intervals are processed.  However, the user of the iterator is
28// not allowed to modify or delete the intervals until after the iterator has
29// been used completely.  The IntervalPartition class uses this functionality.
30//
31//===----------------------------------------------------------------------===//
32
33#ifndef LLVM_ANALYSIS_INTERVALITERATOR_H
34#define LLVM_ANALYSIS_INTERVALITERATOR_H
35
36#include "llvm/Analysis/IntervalPartition.h"
37#include "llvm/IR/CFG.h"
38#include "llvm/IR/Function.h"
39#include <algorithm>
40#include <set>
41#include <vector>
42
43namespace llvm {
44
45// getNodeHeader - Given a source graph node and the source graph, return the
46// BasicBlock that is the header node.  This is the opposite of
47// getSourceGraphNode.
48//
49inline BasicBlock *getNodeHeader(BasicBlock *BB) { return BB; }
50inline BasicBlock *getNodeHeader(Interval *I) { return I->getHeaderNode(); }
51
52// getSourceGraphNode - Given a BasicBlock and the source graph, return the
53// source graph node that corresponds to the BasicBlock.  This is the opposite
54// of getNodeHeader.
55//
56inline BasicBlock *getSourceGraphNode(Function *, BasicBlock *BB) {
57  return BB;
58}
59inline Interval *getSourceGraphNode(IntervalPartition *IP, BasicBlock *BB) {
60  return IP->getBlockInterval(BB);
61}
62
63// addNodeToInterval - This method exists to assist the generic ProcessNode
64// with the task of adding a node to the new interval, depending on the
65// type of the source node.  In the case of a CFG source graph (BasicBlock
66// case), the BasicBlock itself is added to the interval.
67//
68inline void addNodeToInterval(Interval *Int, BasicBlock *BB) {
69  Int->Nodes.push_back(BB);
70}
71
72// addNodeToInterval - This method exists to assist the generic ProcessNode
73// with the task of adding a node to the new interval, depending on the
74// type of the source node.  In the case of a CFG source graph (BasicBlock
75// case), the BasicBlock itself is added to the interval.  In the case of
76// an IntervalPartition source graph (Interval case), all of the member
77// BasicBlocks are added to the interval.
78//
79inline void addNodeToInterval(Interval *Int, Interval *I) {
80  // Add all of the nodes in I as new nodes in Int.
81  copy(I->Nodes.begin(), I->Nodes.end(), back_inserter(Int->Nodes));
82}
83
84
85
86
87
88template<class NodeTy, class OrigContainer_t, class GT = GraphTraits<NodeTy*>,
89         class IGT = GraphTraits<Inverse<NodeTy*> > >
90class IntervalIterator {
91  std::vector<std::pair<Interval*, typename Interval::succ_iterator> > IntStack;
92  std::set<BasicBlock*> Visited;
93  OrigContainer_t *OrigContainer;
94  bool IOwnMem;     // If True, delete intervals when done with them
95                    // See file header for conditions of use
96public:
97  typedef IntervalIterator<NodeTy, OrigContainer_t> _Self;
98  typedef std::forward_iterator_tag iterator_category;
99
100  IntervalIterator() {} // End iterator, empty stack
101  IntervalIterator(Function *M, bool OwnMemory) : IOwnMem(OwnMemory) {
102    OrigContainer = M;
103    if (!ProcessInterval(&M->front())) {
104      llvm_unreachable("ProcessInterval should never fail for first interval!");
105    }
106  }
107
108  IntervalIterator(IntervalPartition &IP, bool OwnMemory) : IOwnMem(OwnMemory) {
109    OrigContainer = &IP;
110    if (!ProcessInterval(IP.getRootInterval())) {
111      llvm_unreachable("ProcessInterval should never fail for first interval!");
112    }
113  }
114
115  inline ~IntervalIterator() {
116    if (IOwnMem)
117      while (!IntStack.empty()) {
118        delete operator*();
119        IntStack.pop_back();
120      }
121  }
122
123  inline bool operator==(const _Self& x) const { return IntStack == x.IntStack;}
124  inline bool operator!=(const _Self& x) const { return !operator==(x); }
125
126  inline const Interval *operator*() const { return IntStack.back().first; }
127  inline       Interval *operator*()       { return IntStack.back().first; }
128  inline const Interval *operator->() const { return operator*(); }
129  inline       Interval *operator->()       { return operator*(); }
130
131  _Self& operator++() {  // Preincrement
132    assert(!IntStack.empty() && "Attempting to use interval iterator at end!");
133    do {
134      // All of the intervals on the stack have been visited.  Try visiting
135      // their successors now.
136      Interval::succ_iterator &SuccIt = IntStack.back().second,
137                                EndIt = succ_end(IntStack.back().first);
138      while (SuccIt != EndIt) {                 // Loop over all interval succs
139        bool Done = ProcessInterval(getSourceGraphNode(OrigContainer, *SuccIt));
140        ++SuccIt;                               // Increment iterator
141        if (Done) return *this;                 // Found a new interval! Use it!
142      }
143
144      // Free interval memory... if necessary
145      if (IOwnMem) delete IntStack.back().first;
146
147      // We ran out of successors for this interval... pop off the stack
148      IntStack.pop_back();
149    } while (!IntStack.empty());
150
151    return *this;
152  }
153  inline _Self operator++(int) { // Postincrement
154    _Self tmp = *this; ++*this; return tmp;
155  }
156
157private:
158  // ProcessInterval - This method is used during the construction of the
159  // interval graph.  It walks through the source graph, recursively creating
160  // an interval per invocation until the entire graph is covered.  This uses
161  // the ProcessNode method to add all of the nodes to the interval.
162  //
163  // This method is templated because it may operate on two different source
164  // graphs: a basic block graph, or a preexisting interval graph.
165  //
166  bool ProcessInterval(NodeTy *Node) {
167    BasicBlock *Header = getNodeHeader(Node);
168    if (Visited.count(Header)) return false;
169
170    Interval *Int = new Interval(Header);
171    Visited.insert(Header);   // The header has now been visited!
172
173    // Check all of our successors to see if they are in the interval...
174    for (typename GT::ChildIteratorType I = GT::child_begin(Node),
175           E = GT::child_end(Node); I != E; ++I)
176      ProcessNode(Int, getSourceGraphNode(OrigContainer, *I));
177
178    IntStack.push_back(std::make_pair(Int, succ_begin(Int)));
179    return true;
180  }
181
182  // ProcessNode - This method is called by ProcessInterval to add nodes to the
183  // interval being constructed, and it is also called recursively as it walks
184  // the source graph.  A node is added to the current interval only if all of
185  // its predecessors are already in the graph.  This also takes care of keeping
186  // the successor set of an interval up to date.
187  //
188  // This method is templated because it may operate on two different source
189  // graphs: a basic block graph, or a preexisting interval graph.
190  //
191  void ProcessNode(Interval *Int, NodeTy *Node) {
192    assert(Int && "Null interval == bad!");
193    assert(Node && "Null Node == bad!");
194
195    BasicBlock *NodeHeader = getNodeHeader(Node);
196
197    if (Visited.count(NodeHeader)) {     // Node already been visited?
198      if (Int->contains(NodeHeader)) {   // Already in this interval...
199        return;
200      } else {                           // In other interval, add as successor
201        if (!Int->isSuccessor(NodeHeader)) // Add only if not already in set
202          Int->Successors.push_back(NodeHeader);
203      }
204    } else {                             // Otherwise, not in interval yet
205      for (typename IGT::ChildIteratorType I = IGT::child_begin(Node),
206             E = IGT::child_end(Node); I != E; ++I) {
207        if (!Int->contains(*I)) {        // If pred not in interval, we can't be
208          if (!Int->isSuccessor(NodeHeader)) // Add only if not already in set
209            Int->Successors.push_back(NodeHeader);
210          return;                        // See you later
211        }
212      }
213
214      // If we get here, then all of the predecessors of BB are in the interval
215      // already.  In this case, we must add BB to the interval!
216      addNodeToInterval(Int, Node);
217      Visited.insert(NodeHeader);     // The node has now been visited!
218
219      if (Int->isSuccessor(NodeHeader)) {
220        // If we were in the successor list from before... remove from succ list
221        Int->Successors.erase(std::remove(Int->Successors.begin(),
222                                          Int->Successors.end(), NodeHeader),
223                              Int->Successors.end());
224      }
225
226      // Now that we have discovered that Node is in the interval, perhaps some
227      // of its successors are as well?
228      for (typename GT::ChildIteratorType It = GT::child_begin(Node),
229             End = GT::child_end(Node); It != End; ++It)
230        ProcessNode(Int, getSourceGraphNode(OrigContainer, *It));
231    }
232  }
233};
234
235typedef IntervalIterator<BasicBlock, Function> function_interval_iterator;
236typedef IntervalIterator<Interval, IntervalPartition>
237                                          interval_part_interval_iterator;
238
239
240inline function_interval_iterator intervals_begin(Function *F,
241                                                  bool DeleteInts = true) {
242  return function_interval_iterator(F, DeleteInts);
243}
244inline function_interval_iterator intervals_end(Function *) {
245  return function_interval_iterator();
246}
247
248inline interval_part_interval_iterator
249   intervals_begin(IntervalPartition &IP, bool DeleteIntervals = true) {
250  return interval_part_interval_iterator(IP, DeleteIntervals);
251}
252
253inline interval_part_interval_iterator intervals_end(IntervalPartition &IP) {
254  return interval_part_interval_iterator();
255}
256
257} // End llvm namespace
258
259#endif
260