LoopInfo.h revision 06ac2bef15f8a41f2e3439899b5aa1d95f4bd1f5
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 "Support/GraphTraits.h" 35 36namespace llvm { 37 38class 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 /// removeBlockFromLoop - This removes the specified basic block from the 179 /// current loop, updating the Blocks as appropriate. This does not update 180 /// the mapping in the LoopInfo class. 181 void removeBlockFromLoop(BasicBlock *BB); 182 183 void print(std::ostream &O, unsigned Depth = 0) const; 184 void dump() const; 185private: 186 friend class LoopInfo; 187 Loop(BasicBlock *BB) : ParentLoop(0) { 188 Blocks.push_back(BB); 189 } 190}; 191 192 193 194//===----------------------------------------------------------------------===// 195/// LoopInfo - This class builds and contains all of the top level loop 196/// structures in the specified function. 197/// 198class LoopInfo : public FunctionPass { 199 // BBMap - Mapping of basic blocks to the inner most loop they occur in 200 std::map<BasicBlock*, Loop*> BBMap; 201 std::vector<Loop*> TopLevelLoops; 202 friend class Loop; 203public: 204 ~LoopInfo() { releaseMemory(); } 205 206 /// iterator/begin/end - The interface to the top-level loops in the current 207 /// function. 208 /// 209 typedef std::vector<Loop*>::const_iterator iterator; 210 iterator begin() const { return TopLevelLoops.begin(); } 211 iterator end() const { return TopLevelLoops.end(); } 212 213 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 214 /// block is in no loop (for example the entry node), null is returned. 215 /// 216 Loop *getLoopFor(const BasicBlock *BB) const { 217 std::map<BasicBlock *, Loop*>::const_iterator I=BBMap.find((BasicBlock*)BB); 218 return I != BBMap.end() ? I->second : 0; 219 } 220 221 /// operator[] - same as getLoopFor... 222 /// 223 const Loop *operator[](const BasicBlock *BB) const { 224 return getLoopFor(BB); 225 } 226 227 /// getLoopDepth - Return the loop nesting level of the specified block... 228 /// 229 unsigned getLoopDepth(const BasicBlock *BB) const { 230 const Loop *L = getLoopFor(BB); 231 return L ? L->getLoopDepth() : 0; 232 } 233 234 // isLoopHeader - True if the block is a loop header node 235 bool isLoopHeader(BasicBlock *BB) const { 236 return getLoopFor(BB)->getHeader() == BB; 237 } 238 239 /// runOnFunction - Calculate the natural loop information. 240 /// 241 virtual bool runOnFunction(Function &F); 242 243 virtual void releaseMemory(); 244 void print(std::ostream &O) const; 245 246 /// getAnalysisUsage - Requires dominator sets 247 /// 248 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 249 250 /// removeLoop - This removes the specified top-level loop from this loop info 251 /// object. The loop is not deleted, as it will presumably be inserted into 252 /// another loop. 253 Loop *removeLoop(iterator I); 254 255 /// changeLoopFor - Change the top-level loop that contains BB to the 256 /// specified loop. This should be used by transformations that restructure 257 /// the loop hierarchy tree. 258 void changeLoopFor(BasicBlock *BB, Loop *L); 259 260 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 261 /// list with the indicated loop. 262 void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop); 263 264 /// addTopLevelLoop - This adds the specified loop to the collection of 265 /// top-level loops. 266 void addTopLevelLoop(Loop *New) { 267 assert(New->getParentLoop() == 0 && "Loop already in subloop!"); 268 TopLevelLoops.push_back(New); 269 } 270 271 /// removeBlock - This method completely removes BB from all data structures, 272 /// including all of the Loop objects it is nested in and our mapping from 273 /// BasicBlocks to loops. 274 void removeBlock(BasicBlock *BB); 275 276 static void stub(); // Noop 277private: 278 void Calculate(const DominatorSet &DS); 279 Loop *ConsiderForLoop(BasicBlock *BB, const DominatorSet &DS); 280 void MoveSiblingLoopInto(Loop *NewChild, Loop *NewParent); 281 void InsertLoopInto(Loop *L, Loop *Parent); 282}; 283 284 285// Make sure that any clients of this file link in LoopInfo.cpp 286static IncludeFile 287LOOP_INFO_INCLUDE_FILE((void*)&LoopInfo::stub); 288 289// Allow clients to walk the list of nested loops... 290template <> struct GraphTraits<const Loop*> { 291 typedef const Loop NodeType; 292 typedef std::vector<Loop*>::const_iterator ChildIteratorType; 293 294 static NodeType *getEntryNode(const Loop *L) { return L; } 295 static inline ChildIteratorType child_begin(NodeType *N) { 296 return N->begin(); 297 } 298 static inline ChildIteratorType child_end(NodeType *N) { 299 return N->end(); 300 } 301}; 302 303template <> struct GraphTraits<Loop*> { 304 typedef Loop NodeType; 305 typedef std::vector<Loop*>::const_iterator ChildIteratorType; 306 307 static NodeType *getEntryNode(Loop *L) { return L; } 308 static inline ChildIteratorType child_begin(NodeType *N) { 309 return N->begin(); 310 } 311 static inline ChildIteratorType child_end(NodeType *N) { 312 return N->end(); 313 } 314}; 315 316} // End llvm namespace 317 318#endif 319