LoopInfo.h revision 88d3ef2c744db0289223a4477669f24d542e6d97
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; 37class 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 /// isLoopInvariant - Return true if the specified value is loop invariant 88 /// 89 bool isLoopInvariant(Value *V) const; 90 91 //===--------------------------------------------------------------------===// 92 // APIs for simple analysis of the loop. 93 // 94 // Note that all of these methods can fail on general loops (ie, there may not 95 // be a preheader, etc). For best success, the loop simplification and 96 // induction variable canonicalization pass should be used to normalize loops 97 // for easy analysis. These methods assume canonical loops. 98 99 /// getExitBlocks - Return all of the successor blocks of this loop. These 100 /// are the blocks _outside of the current loop_ which are branched to. 101 /// 102 void getExitBlocks(std::vector<BasicBlock*> &Blocks) const; 103 104 /// getLoopPreheader - If there is a preheader for this loop, return it. A 105 /// loop has a preheader if there is only one edge to the header of the loop 106 /// from outside of the loop. If this is the case, the block branching to the 107 /// header of the loop is the preheader node. 108 /// 109 /// This method returns null if there is no preheader for the loop. 110 /// 111 BasicBlock *getLoopPreheader() const; 112 113 /// getCanonicalInductionVariable - Check to see if the loop has a canonical 114 /// induction variable: an integer recurrence that starts at 0 and increments 115 /// by one each time through the loop. If so, return the phi node that 116 /// corresponds to it. 117 /// 118 PHINode *getCanonicalInductionVariable() const; 119 120 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds 121 /// the canonical induction variable value for the "next" iteration of the 122 /// loop. This always succeeds if getCanonicalInductionVariable succeeds. 123 /// 124 Instruction *getCanonicalInductionVariableIncrement() const; 125 126 /// getTripCount - Return a loop-invariant LLVM value indicating the number of 127 /// times the loop will be executed. Note that this means that the backedge 128 /// of the loop executes N-1 times. If the trip-count cannot be determined, 129 /// this returns null. 130 /// 131 Value *getTripCount() const; 132 133 //===--------------------------------------------------------------------===// 134 // APIs for updating loop information after changing the CFG 135 // 136 137 /// addBasicBlockToLoop - This method is used by other analyses to update loop 138 /// information. NewBB is set to be a new member of the current loop. 139 /// Because of this, it is added as a member of all parent loops, and is added 140 /// to the specified LoopInfo object as being in the current basic block. It 141 /// is not valid to replace the loop header with this method. 142 /// 143 void addBasicBlockToLoop(BasicBlock *NewBB, LoopInfo &LI); 144 145 /// replaceChildLoopWith - This is used when splitting loops up. It replaces 146 /// the OldChild entry in our children list with NewChild, and updates the 147 /// parent pointer of OldChild to be null and the NewChild to be this loop. 148 /// This updates the loop depth of the new child. 149 void replaceChildLoopWith(Loop *OldChild, Loop *NewChild); 150 151 /// addChildLoop - Add the specified loop to be a child of this loop. This 152 /// updates the loop depth of the new child. 153 /// 154 void addChildLoop(Loop *NewChild); 155 156 /// removeChildLoop - This removes the specified child from being a subloop of 157 /// this loop. The loop is not deleted, as it will presumably be inserted 158 /// into another loop. 159 Loop *removeChildLoop(iterator OldChild); 160 161 /// addBlockEntry - This adds a basic block directly to the basic block list. 162 /// This should only be used by transformations that create new loops. Other 163 /// transformations should use addBasicBlockToLoop. 164 void addBlockEntry(BasicBlock *BB) { 165 Blocks.push_back(BB); 166 } 167 168 /// removeBlockFromLoop - This removes the specified basic block from the 169 /// current loop, updating the Blocks as appropriate. This does not update 170 /// the mapping in the LoopInfo class. 171 void removeBlockFromLoop(BasicBlock *BB); 172 173 void print(std::ostream &O, unsigned Depth = 0) const; 174 void dump() const; 175private: 176 friend class LoopInfo; 177 Loop(BasicBlock *BB) : ParentLoop(0) { 178 Blocks.push_back(BB); LoopDepth = 0; 179 } 180 void setLoopDepth(unsigned Level) { 181 LoopDepth = Level; 182 for (unsigned i = 0, e = SubLoops.size(); i != e; ++i) 183 SubLoops[i]->setLoopDepth(Level+1); 184 } 185}; 186 187 188 189//===----------------------------------------------------------------------===// 190/// LoopInfo - This class builds and contains all of the top level loop 191/// structures in the specified function. 192/// 193class LoopInfo : public FunctionPass { 194 // BBMap - Mapping of basic blocks to the inner most loop they occur in 195 std::map<BasicBlock*, Loop*> BBMap; 196 std::vector<Loop*> TopLevelLoops; 197 friend class Loop; 198public: 199 ~LoopInfo() { releaseMemory(); } 200 201 /// iterator/begin/end - The interface to the top-level loops in the current 202 /// function. 203 /// 204 typedef std::vector<Loop*>::const_iterator iterator; 205 iterator begin() const { return TopLevelLoops.begin(); } 206 iterator end() const { return TopLevelLoops.end(); } 207 208 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 209 /// block is in no loop (for example the entry node), null is returned. 210 /// 211 const Loop *getLoopFor(const BasicBlock *BB) const { 212 std::map<BasicBlock *, Loop*>::const_iterator I=BBMap.find((BasicBlock*)BB); 213 return I != BBMap.end() ? I->second : 0; 214 } 215 216 /// operator[] - same as getLoopFor... 217 /// 218 inline const Loop *operator[](const BasicBlock *BB) const { 219 return getLoopFor(BB); 220 } 221 222 /// getLoopDepth - Return the loop nesting level of the specified block... 223 /// 224 unsigned getLoopDepth(const BasicBlock *BB) const { 225 const Loop *L = getLoopFor(BB); 226 return L ? L->getLoopDepth() : 0; 227 } 228 229 // isLoopHeader - True if the block is a loop header node 230 bool isLoopHeader(BasicBlock *BB) const { 231 return getLoopFor(BB)->getHeader() == BB; 232 } 233 234 /// runOnFunction - Calculate the natural loop information. 235 /// 236 virtual bool runOnFunction(Function &F); 237 238 virtual void releaseMemory(); 239 void print(std::ostream &O) const; 240 241 /// getAnalysisUsage - Requires dominator sets 242 /// 243 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 244 245 /// removeLoop - This removes the specified top-level loop from this loop info 246 /// object. The loop is not deleted, as it will presumably be inserted into 247 /// another loop. 248 Loop *removeLoop(iterator I); 249 250 /// changeLoopFor - Change the top-level loop that contains BB to the 251 /// specified loop. This should be used by transformations that restructure 252 /// the loop hierarchy tree. 253 void changeLoopFor(BasicBlock *BB, Loop *L); 254 255 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 256 /// list with the indicated loop. 257 void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop); 258 259 /// removeBlock - This method completely removes BB from all data structures, 260 /// including all of the Loop objects it is nested in and our mapping from 261 /// BasicBlocks to loops. 262 void removeBlock(BasicBlock *BB); 263 264 static void stub(); // Noop 265private: 266 void Calculate(const DominatorSet &DS); 267 Loop *ConsiderForLoop(BasicBlock *BB, const DominatorSet &DS); 268 void MoveSiblingLoopInto(Loop *NewChild, Loop *NewParent); 269 void InsertLoopInto(Loop *L, Loop *Parent); 270}; 271 272 273// Make sure that any clients of this file link in LoopInfo.cpp 274static IncludeFile 275LOOP_INFO_INCLUDE_FILE((void*)&LoopInfo::stub); 276 277// Allow clients to walk the list of nested loops... 278template <> struct GraphTraits<const Loop*> { 279 typedef const Loop NodeType; 280 typedef std::vector<Loop*>::const_iterator ChildIteratorType; 281 282 static NodeType *getEntryNode(const Loop *L) { return L; } 283 static inline ChildIteratorType child_begin(NodeType *N) { 284 return N->begin(); 285 } 286 static inline ChildIteratorType child_end(NodeType *N) { 287 return N->end(); 288 } 289}; 290 291template <> struct GraphTraits<Loop*> { 292 typedef Loop NodeType; 293 typedef std::vector<Loop*>::const_iterator ChildIteratorType; 294 295 static NodeType *getEntryNode(Loop *L) { return L; } 296 static inline ChildIteratorType child_begin(NodeType *N) { 297 return N->begin(); 298 } 299 static inline ChildIteratorType child_end(NodeType *N) { 300 return N->end(); 301 } 302}; 303 304} // End llvm namespace 305 306#endif 307