LoopInfo.h revision 21d6ff546d0c9cd1a631fe7940a3988a2472198c
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 const std::vector<Loop*> &getSubLoops() const { return SubLoops; } 78 typedef std::vector<Loop*>::const_iterator iterator; 79 iterator begin() const { return SubLoops.begin(); } 80 iterator end() const { return SubLoops.end(); } 81 82 /// getBlocks - Get a list of the basic blocks which make up this loop. 83 /// 84 const std::vector<BasicBlock*> &getBlocks() const { return Blocks; } 85 typedef std::vector<BasicBlock*>::const_iterator block_iterator; 86 block_iterator block_begin() const { return Blocks.begin(); } 87 block_iterator block_end() const { return Blocks.end(); } 88 89 /// isLoopExit - True if terminator in the block can branch to another block 90 /// that is outside of the current loop. 91 /// 92 bool isLoopExit(const BasicBlock *BB) const; 93 94 /// getNumBackEdges - Calculate the number of back edges to the loop header 95 /// 96 unsigned getNumBackEdges() const; 97 98 /// isLoopInvariant - Return true if the specified value is loop invariant 99 /// 100 bool isLoopInvariant(Value *V) const; 101 102 //===--------------------------------------------------------------------===// 103 // APIs for simple analysis of the loop. 104 // 105 // Note that all of these methods can fail on general loops (ie, there may not 106 // be a preheader, etc). For best success, the loop simplification and 107 // induction variable canonicalization pass should be used to normalize loops 108 // for easy analysis. These methods assume canonical loops. 109 110 /// getExitBlocks - Return all of the successor blocks of this loop. These 111 /// are the blocks _outside of the current loop_ which are branched to. 112 /// 113 void getExitBlocks(std::vector<BasicBlock*> &Blocks) const; 114 115 /// getLoopPreheader - If there is a preheader for this loop, return it. A 116 /// loop has a preheader if there is only one edge to the header of the loop 117 /// from outside of the loop. If this is the case, the block branching to the 118 /// header of the loop is the preheader node. 119 /// 120 /// This method returns null if there is no preheader for the loop. 121 /// 122 BasicBlock *getLoopPreheader() const; 123 124 /// getCanonicalInductionVariable - Check to see if the loop has a canonical 125 /// induction variable: an integer recurrence that starts at 0 and increments 126 /// by one each time through the loop. If so, return the phi node that 127 /// corresponds to it. 128 /// 129 PHINode *getCanonicalInductionVariable() const; 130 131 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds 132 /// the canonical induction variable value for the "next" iteration of the 133 /// loop. This always succeeds if getCanonicalInductionVariable succeeds. 134 /// 135 Instruction *getCanonicalInductionVariableIncrement() const; 136 137 /// getTripCount - Return a loop-invariant LLVM value indicating the number of 138 /// times the loop will be executed. Note that this means that the backedge 139 /// of the loop executes N-1 times. If the trip-count cannot be determined, 140 /// this returns null. 141 /// 142 Value *getTripCount() const; 143 144 //===--------------------------------------------------------------------===// 145 // APIs for updating loop information after changing the CFG 146 // 147 148 /// addBasicBlockToLoop - This method is used by other analyses to update loop 149 /// information. NewBB is set to be a new member of the current loop. 150 /// Because of this, it is added as a member of all parent loops, and is added 151 /// to the specified LoopInfo object as being in the current basic block. It 152 /// is not valid to replace the loop header with this method. 153 /// 154 void addBasicBlockToLoop(BasicBlock *NewBB, LoopInfo &LI); 155 156 /// replaceChildLoopWith - This is used when splitting loops up. It replaces 157 /// the OldChild entry in our children list with NewChild, and updates the 158 /// parent pointer of OldChild to be null and the NewChild to be this loop. 159 /// This updates the loop depth of the new child. 160 void replaceChildLoopWith(Loop *OldChild, Loop *NewChild); 161 162 /// addChildLoop - Add the specified loop to be a child of this loop. This 163 /// updates the loop depth of the new child. 164 /// 165 void addChildLoop(Loop *NewChild); 166 167 /// removeChildLoop - This removes the specified child from being a subloop of 168 /// this loop. The loop is not deleted, as it will presumably be inserted 169 /// into another loop. 170 Loop *removeChildLoop(iterator OldChild); 171 172 /// addBlockEntry - This adds a basic block directly to the basic block list. 173 /// This should only be used by transformations that create new loops. Other 174 /// transformations should use addBasicBlockToLoop. 175 void addBlockEntry(BasicBlock *BB) { 176 Blocks.push_back(BB); 177 } 178 179 /// moveToHeader - This method is used to move BB (which must be part of this 180 /// loop) to be the loop header of the loop (the block that dominates all 181 /// others). 182 void moveToHeader(BasicBlock *BB) { 183 if (Blocks[0] == BB) return; 184 for (unsigned i = 0; ; ++i) { 185 assert(i != Blocks.size() && "Loop does not contain BB!"); 186 if (Blocks[i] == BB) { 187 Blocks[i] = Blocks[0]; 188 Blocks[0] = BB; 189 return; 190 } 191 } 192 } 193 194 /// removeBlockFromLoop - This removes the specified basic block from the 195 /// current loop, updating the Blocks as appropriate. This does not update 196 /// the mapping in the LoopInfo class. 197 void removeBlockFromLoop(BasicBlock *BB); 198 199 void print(std::ostream &O, unsigned Depth = 0) const; 200 void dump() const; 201private: 202 friend class LoopInfo; 203 Loop(BasicBlock *BB) : ParentLoop(0) { 204 Blocks.push_back(BB); 205 } 206}; 207 208 209 210//===----------------------------------------------------------------------===// 211/// LoopInfo - This class builds and contains all of the top level loop 212/// structures in the specified function. 213/// 214class LoopInfo : public FunctionPass { 215 // BBMap - Mapping of basic blocks to the inner most loop they occur in 216 std::map<BasicBlock*, Loop*> BBMap; 217 std::vector<Loop*> TopLevelLoops; 218 friend class Loop; 219public: 220 ~LoopInfo() { releaseMemory(); } 221 222 /// iterator/begin/end - The interface to the top-level loops in the current 223 /// function. 224 /// 225 typedef std::vector<Loop*>::const_iterator iterator; 226 iterator begin() const { return TopLevelLoops.begin(); } 227 iterator end() const { return TopLevelLoops.end(); } 228 229 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 230 /// block is in no loop (for example the entry node), null is returned. 231 /// 232 Loop *getLoopFor(const BasicBlock *BB) const { 233 std::map<BasicBlock *, Loop*>::const_iterator I=BBMap.find((BasicBlock*)BB); 234 return I != BBMap.end() ? I->second : 0; 235 } 236 237 /// operator[] - same as getLoopFor... 238 /// 239 const Loop *operator[](const BasicBlock *BB) const { 240 return getLoopFor(BB); 241 } 242 243 /// getLoopDepth - Return the loop nesting level of the specified block... 244 /// 245 unsigned getLoopDepth(const BasicBlock *BB) const { 246 const Loop *L = getLoopFor(BB); 247 return L ? L->getLoopDepth() : 0; 248 } 249 250 // isLoopHeader - True if the block is a loop header node 251 bool isLoopHeader(BasicBlock *BB) const { 252 return getLoopFor(BB)->getHeader() == BB; 253 } 254 255 /// runOnFunction - Calculate the natural loop information. 256 /// 257 virtual bool runOnFunction(Function &F); 258 259 virtual void releaseMemory(); 260 void print(std::ostream &O, const Module* = 0) const; 261 262 /// getAnalysisUsage - Requires dominator sets 263 /// 264 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 265 266 /// removeLoop - This removes the specified top-level loop from this loop info 267 /// object. The loop is not deleted, as it will presumably be inserted into 268 /// another loop. 269 Loop *removeLoop(iterator I); 270 271 /// changeLoopFor - Change the top-level loop that contains BB to the 272 /// specified loop. This should be used by transformations that restructure 273 /// the loop hierarchy tree. 274 void changeLoopFor(BasicBlock *BB, Loop *L); 275 276 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 277 /// list with the indicated loop. 278 void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop); 279 280 /// addTopLevelLoop - This adds the specified loop to the collection of 281 /// top-level loops. 282 void addTopLevelLoop(Loop *New) { 283 assert(New->getParentLoop() == 0 && "Loop already in subloop!"); 284 TopLevelLoops.push_back(New); 285 } 286 287 /// removeBlock - This method completely removes BB from all data structures, 288 /// including all of the Loop objects it is nested in and our mapping from 289 /// BasicBlocks to loops. 290 void removeBlock(BasicBlock *BB); 291 292 static void stub(); // Noop 293private: 294 void Calculate(const DominatorSet &DS); 295 Loop *ConsiderForLoop(BasicBlock *BB, const DominatorSet &DS); 296 void MoveSiblingLoopInto(Loop *NewChild, Loop *NewParent); 297 void InsertLoopInto(Loop *L, Loop *Parent); 298}; 299 300 301// Make sure that any clients of this file link in LoopInfo.cpp 302static IncludeFile 303LOOP_INFO_INCLUDE_FILE((void*)&LoopInfo::stub); 304 305// Allow clients to walk the list of nested loops... 306template <> struct GraphTraits<const Loop*> { 307 typedef const Loop NodeType; 308 typedef std::vector<Loop*>::const_iterator ChildIteratorType; 309 310 static NodeType *getEntryNode(const Loop *L) { return L; } 311 static inline ChildIteratorType child_begin(NodeType *N) { 312 return N->begin(); 313 } 314 static inline ChildIteratorType child_end(NodeType *N) { 315 return N->end(); 316 } 317}; 318 319template <> struct GraphTraits<Loop*> { 320 typedef Loop NodeType; 321 typedef std::vector<Loop*>::const_iterator ChildIteratorType; 322 323 static NodeType *getEntryNode(Loop *L) { return L; } 324 static inline ChildIteratorType child_begin(NodeType *N) { 325 return N->begin(); 326 } 327 static inline ChildIteratorType child_end(NodeType *N) { 328 return N->end(); 329 } 330}; 331 332} // End llvm namespace 333 334#endif 335