LoopInfo.h revision 9769ab22265b313171d201b5928688524a01bd87
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 loop and the basic blocks the make up the loop. 17// 18// It can calculate on the fly various bits of information, for example: 19// 20// * whether there is a preheader for the loop 21// * the number of back edges to the header 22// * whether or not a particular block branches out of the loop 23// * the successor blocks of the loop 24// * the loop depth 25// * the trip count 26// * etc... 27// 28//===----------------------------------------------------------------------===// 29 30#ifndef LLVM_ANALYSIS_LOOP_INFO_H 31#define LLVM_ANALYSIS_LOOP_INFO_H 32 33#include "llvm/Pass.h" 34#include "llvm/ADT/GraphTraits.h" 35 36namespace llvm { 37 38struct DominatorSet; 39class LoopInfo; 40class PHINode; 41class Instruction; 42 43//===----------------------------------------------------------------------===// 44/// Loop class - Instances of this class are used to represent loops that are 45/// detected in the flow graph 46/// 47class Loop { 48 Loop *ParentLoop; 49 std::vector<Loop*> SubLoops; // Loops contained entirely within this one 50 std::vector<BasicBlock*> Blocks; // First entry is the header node 51 52 Loop(const Loop &); // DO NOT IMPLEMENT 53 const Loop &operator=(const Loop &); // DO NOT IMPLEMENT 54public: 55 /// Loop ctor - This creates an empty loop. 56 Loop() : ParentLoop(0) {} 57 ~Loop() { 58 for (unsigned i = 0, e = SubLoops.size(); i != e; ++i) 59 delete SubLoops[i]; 60 } 61 62 unsigned getLoopDepth() const { 63 unsigned D = 0; 64 for (const Loop *CurLoop = this; CurLoop; CurLoop = CurLoop->ParentLoop) 65 ++D; 66 return D; 67 } 68 BasicBlock *getHeader() const { return Blocks.front(); } 69 Loop *getParentLoop() const { return ParentLoop; } 70 71 /// contains - Return true of the specified basic block is in this loop 72 /// 73 bool contains(const BasicBlock *BB) const; 74 75 /// iterator/begin/end - Return the loops contained entirely within this loop. 76 /// 77 typedef std::vector<Loop*>::const_iterator iterator; 78 iterator begin() const { return SubLoops.begin(); } 79 iterator end() const { return SubLoops.end(); } 80 81 /// getBlocks - Get a list of the basic blocks which make up this loop. 82 /// 83 const std::vector<BasicBlock*> &getBlocks() const { return Blocks; } 84 typedef std::vector<BasicBlock*>::const_iterator block_iterator; 85 block_iterator block_begin() const { return Blocks.begin(); } 86 block_iterator block_end() const { return Blocks.end(); } 87 88 /// isLoopExit - True if terminator in the block can branch to another block 89 /// that is outside of the current loop. 90 /// 91 bool isLoopExit(const BasicBlock *BB) const; 92 93 /// getNumBackEdges - Calculate the number of back edges to the loop header 94 /// 95 unsigned getNumBackEdges() const; 96 97 /// isLoopInvariant - Return true if the specified value is loop invariant 98 /// 99 bool isLoopInvariant(Value *V) const; 100 101 //===--------------------------------------------------------------------===// 102 // APIs for simple analysis of the loop. 103 // 104 // Note that all of these methods can fail on general loops (ie, there may not 105 // be a preheader, etc). For best success, the loop simplification and 106 // induction variable canonicalization pass should be used to normalize loops 107 // for easy analysis. These methods assume canonical loops. 108 109 /// getExitBlocks - Return all of the successor blocks of this loop. These 110 /// are the blocks _outside of the current loop_ which are branched to. 111 /// 112 void getExitBlocks(std::vector<BasicBlock*> &Blocks) const; 113 114 /// getLoopPreheader - If there is a preheader for this loop, return it. A 115 /// loop has a preheader if there is only one edge to the header of the loop 116 /// from outside of the loop. If this is the case, the block branching to the 117 /// header of the loop is the preheader node. 118 /// 119 /// This method returns null if there is no preheader for the loop. 120 /// 121 BasicBlock *getLoopPreheader() const; 122 123 /// getCanonicalInductionVariable - Check to see if the loop has a canonical 124 /// induction variable: an integer recurrence that starts at 0 and increments 125 /// by one each time through the loop. If so, return the phi node that 126 /// corresponds to it. 127 /// 128 PHINode *getCanonicalInductionVariable() const; 129 130 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds 131 /// the canonical induction variable value for the "next" iteration of the 132 /// loop. This always succeeds if getCanonicalInductionVariable succeeds. 133 /// 134 Instruction *getCanonicalInductionVariableIncrement() const; 135 136 /// getTripCount - Return a loop-invariant LLVM value indicating the number of 137 /// times the loop will be executed. Note that this means that the backedge 138 /// of the loop executes N-1 times. If the trip-count cannot be determined, 139 /// this returns null. 140 /// 141 Value *getTripCount() const; 142 143 //===--------------------------------------------------------------------===// 144 // APIs for updating loop information after changing the CFG 145 // 146 147 /// addBasicBlockToLoop - This method is used by other analyses to update loop 148 /// information. NewBB is set to be a new member of the current loop. 149 /// Because of this, it is added as a member of all parent loops, and is added 150 /// to the specified LoopInfo object as being in the current basic block. It 151 /// is not valid to replace the loop header with this method. 152 /// 153 void addBasicBlockToLoop(BasicBlock *NewBB, LoopInfo &LI); 154 155 /// replaceChildLoopWith - This is used when splitting loops up. It replaces 156 /// the OldChild entry in our children list with NewChild, and updates the 157 /// parent pointer of OldChild to be null and the NewChild to be this loop. 158 /// This updates the loop depth of the new child. 159 void replaceChildLoopWith(Loop *OldChild, Loop *NewChild); 160 161 /// addChildLoop - Add the specified loop to be a child of this loop. This 162 /// updates the loop depth of the new child. 163 /// 164 void addChildLoop(Loop *NewChild); 165 166 /// removeChildLoop - This removes the specified child from being a subloop of 167 /// this loop. The loop is not deleted, as it will presumably be inserted 168 /// into another loop. 169 Loop *removeChildLoop(iterator OldChild); 170 171 /// addBlockEntry - This adds a basic block directly to the basic block list. 172 /// This should only be used by transformations that create new loops. Other 173 /// transformations should use addBasicBlockToLoop. 174 void addBlockEntry(BasicBlock *BB) { 175 Blocks.push_back(BB); 176 } 177 178 /// moveToHeader - This method is used to move BB (which must be part of this 179 /// loop) to be the loop header of the loop (the block that dominates all 180 /// others). 181 void moveToHeader(BasicBlock *BB) { 182 if (Blocks[0] == BB) return; 183 for (unsigned i = 0; ; ++i) { 184 assert(i != Blocks.size() && "Loop does not contain BB!"); 185 if (Blocks[i] == BB) { 186 Blocks[i] = Blocks[0]; 187 Blocks[0] = BB; 188 return; 189 } 190 } 191 } 192 193 /// removeBlockFromLoop - This removes the specified basic block from the 194 /// current loop, updating the Blocks as appropriate. This does not update 195 /// the mapping in the LoopInfo class. 196 void removeBlockFromLoop(BasicBlock *BB); 197 198 void print(std::ostream &O, unsigned Depth = 0) const; 199 void dump() const; 200private: 201 friend class LoopInfo; 202 Loop(BasicBlock *BB) : ParentLoop(0) { 203 Blocks.push_back(BB); 204 } 205}; 206 207 208 209//===----------------------------------------------------------------------===// 210/// LoopInfo - This class builds and contains all of the top level loop 211/// structures in the specified function. 212/// 213class LoopInfo : public FunctionPass { 214 // BBMap - Mapping of basic blocks to the inner most loop they occur in 215 std::map<BasicBlock*, Loop*> BBMap; 216 std::vector<Loop*> TopLevelLoops; 217 friend class Loop; 218public: 219 ~LoopInfo() { releaseMemory(); } 220 221 /// iterator/begin/end - The interface to the top-level loops in the current 222 /// function. 223 /// 224 typedef std::vector<Loop*>::const_iterator iterator; 225 iterator begin() const { return TopLevelLoops.begin(); } 226 iterator end() const { return TopLevelLoops.end(); } 227 228 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 229 /// block is in no loop (for example the entry node), null is returned. 230 /// 231 Loop *getLoopFor(const BasicBlock *BB) const { 232 std::map<BasicBlock *, Loop*>::const_iterator I=BBMap.find((BasicBlock*)BB); 233 return I != BBMap.end() ? I->second : 0; 234 } 235 236 /// operator[] - same as getLoopFor... 237 /// 238 const Loop *operator[](const BasicBlock *BB) const { 239 return getLoopFor(BB); 240 } 241 242 /// getLoopDepth - Return the loop nesting level of the specified block... 243 /// 244 unsigned getLoopDepth(const BasicBlock *BB) const { 245 const Loop *L = getLoopFor(BB); 246 return L ? L->getLoopDepth() : 0; 247 } 248 249 // isLoopHeader - True if the block is a loop header node 250 bool isLoopHeader(BasicBlock *BB) const { 251 return getLoopFor(BB)->getHeader() == BB; 252 } 253 254 /// runOnFunction - Calculate the natural loop information. 255 /// 256 virtual bool runOnFunction(Function &F); 257 258 virtual void releaseMemory(); 259 void print(std::ostream &O, const Module* = 0) const; 260 261 /// getAnalysisUsage - Requires dominator sets 262 /// 263 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 264 265 /// removeLoop - This removes the specified top-level loop from this loop info 266 /// object. The loop is not deleted, as it will presumably be inserted into 267 /// another loop. 268 Loop *removeLoop(iterator I); 269 270 /// changeLoopFor - Change the top-level loop that contains BB to the 271 /// specified loop. This should be used by transformations that restructure 272 /// the loop hierarchy tree. 273 void changeLoopFor(BasicBlock *BB, Loop *L); 274 275 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 276 /// list with the indicated loop. 277 void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop); 278 279 /// addTopLevelLoop - This adds the specified loop to the collection of 280 /// top-level loops. 281 void addTopLevelLoop(Loop *New) { 282 assert(New->getParentLoop() == 0 && "Loop already in subloop!"); 283 TopLevelLoops.push_back(New); 284 } 285 286 /// removeBlock - This method completely removes BB from all data structures, 287 /// including all of the Loop objects it is nested in and our mapping from 288 /// BasicBlocks to loops. 289 void removeBlock(BasicBlock *BB); 290 291 static void stub(); // Noop 292private: 293 void Calculate(const DominatorSet &DS); 294 Loop *ConsiderForLoop(BasicBlock *BB, const DominatorSet &DS); 295 void MoveSiblingLoopInto(Loop *NewChild, Loop *NewParent); 296 void InsertLoopInto(Loop *L, Loop *Parent); 297}; 298 299 300// Make sure that any clients of this file link in LoopInfo.cpp 301static IncludeFile 302LOOP_INFO_INCLUDE_FILE((void*)&LoopInfo::stub); 303 304// Allow clients to walk the list of nested loops... 305template <> struct GraphTraits<const Loop*> { 306 typedef const Loop NodeType; 307 typedef std::vector<Loop*>::const_iterator ChildIteratorType; 308 309 static NodeType *getEntryNode(const Loop *L) { return L; } 310 static inline ChildIteratorType child_begin(NodeType *N) { 311 return N->begin(); 312 } 313 static inline ChildIteratorType child_end(NodeType *N) { 314 return N->end(); 315 } 316}; 317 318template <> struct GraphTraits<Loop*> { 319 typedef Loop NodeType; 320 typedef std::vector<Loop*>::const_iterator ChildIteratorType; 321 322 static NodeType *getEntryNode(Loop *L) { return L; } 323 static inline ChildIteratorType child_begin(NodeType *N) { 324 return N->begin(); 325 } 326 static inline ChildIteratorType child_end(NodeType *N) { 327 return N->end(); 328 } 329}; 330 331} // End llvm namespace 332 333#endif 334