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_INTERVAL_ITERATOR_H
34 #define LLVM_INTERVAL_ITERATOR_H
35 
36 #include "llvm/Analysis/IntervalPartition.h"
37 #include "llvm/Function.h"
38 #include "llvm/Support/CFG.h"
39 #include <algorithm>
40 #include <set>
41 #include <vector>
42 
43 namespace 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 //
49 inline BasicBlock *getNodeHeader(BasicBlock *BB) { return BB; }
50 inline 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 //
56 inline BasicBlock *getSourceGraphNode(Function *, BasicBlock *BB) {
57   return BB;
58 }
59 inline 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 //
68 inline 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 //
79 inline 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 
88 template<class NodeTy, class OrigContainer_t, class GT = GraphTraits<NodeTy*>,
89          class IGT = GraphTraits<Inverse<NodeTy*> > >
90 class 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
96 public:
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       assert(0 && "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       assert(0 && "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 
157 private:
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 invokation 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 
235 typedef IntervalIterator<BasicBlock, Function> function_interval_iterator;
236 typedef IntervalIterator<Interval, IntervalPartition>
237                                           interval_part_interval_iterator;
238 
239 
240 inline function_interval_iterator intervals_begin(Function *F,
241                                                   bool DeleteInts = true) {
242   return function_interval_iterator(F, DeleteInts);
243 }
244 inline function_interval_iterator intervals_end(Function *) {
245   return function_interval_iterator();
246 }
247 
248 inline interval_part_interval_iterator
249    intervals_begin(IntervalPartition &IP, bool DeleteIntervals = true) {
250   return interval_part_interval_iterator(IP, DeleteIntervals);
251 }
252 
253 inline interval_part_interval_iterator intervals_end(IntervalPartition &IP) {
254   return interval_part_interval_iterator();
255 }
256 
257 } // End llvm namespace
258 
259 #endif
260