LoopInfo.h revision f1ab4b4eac5603d19c20f4a508f93a118a52bdd5
1//===- llvm/Analysis/LoopInfo.h - Natural Loop Calculator -------*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file was developed by the LLVM research group and is distributed under 6// the University of Illinois Open Source License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file defines the LoopInfo class that is used to identify natural loops 11// and determine the loop depth of various nodes of the CFG. Note that natural 12// loops may actually be several loops that share the same header node. 13// 14// This analysis calculates the nesting structure of loops in a function. For 15// each natural loop identified, this analysis identifies natural loops 16// contained entirely within the function, the basic blocks the make up the 17// loop, the nesting depth of the loop, and the successor blocks of the loop. 18// 19// It can calculate on the fly a variety of different bits of information, such 20// as whether there is a preheader for the loop, the number of back edges to the 21// header, and whether or not a particular block branches out of the loop. 22// 23//===----------------------------------------------------------------------===// 24 25#ifndef LLVM_ANALYSIS_LOOP_INFO_H 26#define LLVM_ANALYSIS_LOOP_INFO_H 27 28#include "llvm/Pass.h" 29#include "Support/GraphTraits.h" 30#include <set> 31 32namespace llvm { 33 34class DominatorSet; 35class LoopInfo; 36class PHINode; 37 class Instruction; 38 39//===----------------------------------------------------------------------===// 40/// Loop class - Instances of this class are used to represent loops that are 41/// detected in the flow graph 42/// 43class Loop { 44 Loop *ParentLoop; 45 std::vector<Loop*> SubLoops; // Loops contained entirely within this one 46 std::vector<BasicBlock*> Blocks; // First entry is the header node 47 unsigned LoopDepth; // Nesting depth of this loop 48 49 Loop(const Loop &); // DO NOT IMPLEMENT 50 const Loop &operator=(const Loop &); // DO NOT IMPLEMENT 51public: 52 /// Loop ctor - This creates an empty loop. 53 Loop() : ParentLoop(0), LoopDepth(0) { 54 } 55 ~Loop() { 56 for (unsigned i = 0, e = SubLoops.size(); i != e; ++i) 57 delete SubLoops[i]; 58 } 59 60 unsigned getLoopDepth() const { return LoopDepth; } 61 BasicBlock *getHeader() const { return Blocks.front(); } 62 Loop *getParentLoop() const { return ParentLoop; } 63 64 /// contains - Return true of the specified basic block is in this loop 65 /// 66 bool contains(const BasicBlock *BB) const; 67 68 /// iterator/begin/end - Return the loops contained entirely within this loop. 69 /// 70 typedef std::vector<Loop*>::const_iterator iterator; 71 iterator begin() const { return SubLoops.begin(); } 72 iterator end() const { return SubLoops.end(); } 73 74 /// getBlocks - Get a list of the basic blocks which make up this loop. 75 /// 76 const std::vector<BasicBlock*> &getBlocks() const { return Blocks; } 77 78 /// isLoopExit - True if terminator in the block can branch to another block 79 /// that is outside of the current loop. 80 /// 81 bool isLoopExit(const BasicBlock *BB) const; 82 83 /// getNumBackEdges - Calculate the number of back edges to the loop header 84 /// 85 unsigned getNumBackEdges() const; 86 87 //===--------------------------------------------------------------------===// 88 // APIs for simple analysis of the loop. 89 // 90 // Note that all of these methods can fail on general loops (ie, there may not 91 // be a preheader, etc). For best success, the loop simplification and 92 // induction variable canonicalization pass should be used to normalize loops 93 // for easy analysis. These methods assume canonical loops. 94 95 /// getExitBlocks - Return all of the successor blocks of this loop. These 96 /// are the blocks _outside of the current loop_ which are branched to. 97 /// 98 void getExitBlocks(std::vector<BasicBlock*> &Blocks) const; 99 100 /// getLoopPreheader - If there is a preheader for this loop, return it. A 101 /// loop has a preheader if there is only one edge to the header of the loop 102 /// from outside of the loop. If this is the case, the block branching to the 103 /// header of the loop is the preheader node. 104 /// 105 /// This method returns null if there is no preheader for the loop. 106 /// 107 BasicBlock *getLoopPreheader() const; 108 109 /// getCanonicalInductionVariable - Check to see if the loop has a canonical 110 /// induction variable: an integer recurrence that starts at 0 and increments 111 /// by one each time through the loop. If so, return the phi node that 112 /// corresponds to it. 113 /// 114 PHINode *getCanonicalInductionVariable() const; 115 116 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds 117 /// the canonical induction variable value for the "next" iteration of the 118 /// loop. This always succeeds if getCanonicalInductionVariable succeeds. 119 /// 120 Instruction *getCanonicalInductionVariableIncrement() const; 121 122 /// getTripCount - Return a loop-invariant LLVM value indicating the number of 123 /// times the loop will be executed. Note that this means that the backedge 124 /// of the loop executes N-1 times. If the trip-count cannot be determined, 125 /// this returns null. 126 /// 127 Value *getTripCount() const; 128 129 //===--------------------------------------------------------------------===// 130 // APIs for updating loop information after changing the CFG 131 // 132 133 /// addBasicBlockToLoop - This method is used by other analyses to update loop 134 /// information. NewBB is set to be a new member of the current loop. 135 /// Because of this, it is added as a member of all parent loops, and is added 136 /// to the specified LoopInfo object as being in the current basic block. It 137 /// is not valid to replace the loop header with this method. 138 /// 139 void addBasicBlockToLoop(BasicBlock *NewBB, LoopInfo &LI); 140 141 /// replaceChildLoopWith - This is used when splitting loops up. It replaces 142 /// the OldChild entry in our children list with NewChild, and updates the 143 /// parent pointer of OldChild to be null and the NewChild to be this loop. 144 /// This updates the loop depth of the new child. 145 void replaceChildLoopWith(Loop *OldChild, Loop *NewChild); 146 147 /// addChildLoop - Add the specified loop to be a child of this loop. This 148 /// updates the loop depth of the new child. 149 /// 150 void addChildLoop(Loop *NewChild); 151 152 /// removeChildLoop - This removes the specified child from being a subloop of 153 /// this loop. The loop is not deleted, as it will presumably be inserted 154 /// into another loop. 155 Loop *removeChildLoop(iterator OldChild); 156 157 /// addBlockEntry - This adds a basic block directly to the basic block list. 158 /// This should only be used by transformations that create new loops. Other 159 /// transformations should use addBasicBlockToLoop. 160 void addBlockEntry(BasicBlock *BB) { 161 Blocks.push_back(BB); 162 } 163 164 /// removeBlockFromLoop - This removes the specified basic block from the 165 /// current loop, updating the Blocks as appropriate. This does not update 166 /// the mapping in the LoopInfo class. 167 void removeBlockFromLoop(BasicBlock *BB); 168 169 void print(std::ostream &O, unsigned Depth = 0) const; 170 void dump() const; 171private: 172 friend class LoopInfo; 173 Loop(BasicBlock *BB) : ParentLoop(0) { 174 Blocks.push_back(BB); LoopDepth = 0; 175 } 176 void setLoopDepth(unsigned Level) { 177 LoopDepth = Level; 178 for (unsigned i = 0, e = SubLoops.size(); i != e; ++i) 179 SubLoops[i]->setLoopDepth(Level+1); 180 } 181}; 182 183 184 185//===----------------------------------------------------------------------===// 186/// LoopInfo - This class builds and contains all of the top level loop 187/// structures in the specified function. 188/// 189class LoopInfo : public FunctionPass { 190 // BBMap - Mapping of basic blocks to the inner most loop they occur in 191 std::map<BasicBlock*, Loop*> BBMap; 192 std::vector<Loop*> TopLevelLoops; 193 friend class Loop; 194public: 195 ~LoopInfo() { releaseMemory(); } 196 197 /// iterator/begin/end - The interface to the top-level loops in the current 198 /// function. 199 /// 200 typedef std::vector<Loop*>::const_iterator iterator; 201 iterator begin() const { return TopLevelLoops.begin(); } 202 iterator end() const { return TopLevelLoops.end(); } 203 204 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 205 /// block is in no loop (for example the entry node), null is returned. 206 /// 207 const Loop *getLoopFor(const BasicBlock *BB) const { 208 std::map<BasicBlock *, Loop*>::const_iterator I=BBMap.find((BasicBlock*)BB); 209 return I != BBMap.end() ? I->second : 0; 210 } 211 212 /// operator[] - same as getLoopFor... 213 /// 214 inline const Loop *operator[](const BasicBlock *BB) const { 215 return getLoopFor(BB); 216 } 217 218 /// getLoopDepth - Return the loop nesting level of the specified block... 219 /// 220 unsigned getLoopDepth(const BasicBlock *BB) const { 221 const Loop *L = getLoopFor(BB); 222 return L ? L->getLoopDepth() : 0; 223 } 224 225 // isLoopHeader - True if the block is a loop header node 226 bool isLoopHeader(BasicBlock *BB) const { 227 return getLoopFor(BB)->getHeader() == BB; 228 } 229 230 /// runOnFunction - Calculate the natural loop information. 231 /// 232 virtual bool runOnFunction(Function &F); 233 234 virtual void releaseMemory(); 235 void print(std::ostream &O) const; 236 237 /// getAnalysisUsage - Requires dominator sets 238 /// 239 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 240 241 /// removeLoop - This removes the specified top-level loop from this loop info 242 /// object. The loop is not deleted, as it will presumably be inserted into 243 /// another loop. 244 Loop *removeLoop(iterator I); 245 246 /// changeLoopFor - Change the top-level loop that contains BB to the 247 /// specified loop. This should be used by transformations that restructure 248 /// the loop hierarchy tree. 249 void changeLoopFor(BasicBlock *BB, Loop *L); 250 251 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 252 /// list with the indicated loop. 253 void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop); 254 255 /// removeBlock - This method completely removes BB from all data structures, 256 /// including all of the Loop objects it is nested in and our mapping from 257 /// BasicBlocks to loops. 258 void removeBlock(BasicBlock *BB); 259 260 static void stub(); // Noop 261private: 262 void Calculate(const DominatorSet &DS); 263 Loop *ConsiderForLoop(BasicBlock *BB, const DominatorSet &DS); 264 void MoveSiblingLoopInto(Loop *NewChild, Loop *NewParent); 265 void InsertLoopInto(Loop *L, Loop *Parent); 266}; 267 268 269// Make sure that any clients of this file link in LoopInfo.cpp 270static IncludeFile 271LOOP_INFO_INCLUDE_FILE((void*)&LoopInfo::stub); 272 273// Allow clients to walk the list of nested loops... 274template <> struct GraphTraits<const Loop*> { 275 typedef const Loop NodeType; 276 typedef std::vector<Loop*>::const_iterator ChildIteratorType; 277 278 static NodeType *getEntryNode(const Loop *L) { return L; } 279 static inline ChildIteratorType child_begin(NodeType *N) { 280 return N->begin(); 281 } 282 static inline ChildIteratorType child_end(NodeType *N) { 283 return N->end(); 284 } 285}; 286 287template <> struct GraphTraits<Loop*> { 288 typedef Loop NodeType; 289 typedef std::vector<Loop*>::const_iterator ChildIteratorType; 290 291 static NodeType *getEntryNode(Loop *L) { return L; } 292 static inline ChildIteratorType child_begin(NodeType *N) { 293 return N->begin(); 294 } 295 static inline ChildIteratorType child_end(NodeType *N) { 296 return N->end(); 297 } 298}; 299 300} // End llvm namespace 301 302#endif 303