LoopInfo.h revision 263508
1//===- llvm/Analysis/LoopInfo.h - Natural Loop Calculator -------*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// 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. A natural loop 12// has exactly one entry-point, which is called the header. Note that natural 13// loops may actually be several loops that share the same header node. 14// 15// This analysis calculates the nesting structure of loops in a function. For 16// each natural loop identified, this analysis identifies natural loops 17// contained entirely within the loop and the basic blocks the make up the loop. 18// 19// It can calculate on the fly various bits of information, for example: 20// 21// * whether there is a preheader for the loop 22// * the number of back edges to the header 23// * whether or not a particular block branches out of the loop 24// * the successor blocks of the loop 25// * the loop depth 26// * etc... 27// 28//===----------------------------------------------------------------------===// 29 30#ifndef LLVM_ANALYSIS_LOOPINFO_H 31#define LLVM_ANALYSIS_LOOPINFO_H 32 33#include "llvm/ADT/DenseMap.h" 34#include "llvm/ADT/DenseSet.h" 35#include "llvm/ADT/GraphTraits.h" 36#include "llvm/ADT/SmallVector.h" 37#include "llvm/Analysis/Dominators.h" 38#include "llvm/Pass.h" 39#include <algorithm> 40 41namespace llvm { 42 43template<typename T> 44inline void RemoveFromVector(std::vector<T*> &V, T *N) { 45 typename std::vector<T*>::iterator I = std::find(V.begin(), V.end(), N); 46 assert(I != V.end() && "N is not in this list!"); 47 V.erase(I); 48} 49 50class DominatorTree; 51class LoopInfo; 52class Loop; 53class MDNode; 54class PHINode; 55class raw_ostream; 56template<class N, class M> class LoopInfoBase; 57template<class N, class M> class LoopBase; 58 59//===----------------------------------------------------------------------===// 60/// LoopBase class - Instances of this class are used to represent loops that 61/// are detected in the flow graph 62/// 63template<class BlockT, class LoopT> 64class LoopBase { 65 LoopT *ParentLoop; 66 // SubLoops - Loops contained entirely within this one. 67 std::vector<LoopT *> SubLoops; 68 69 // Blocks - The list of blocks in this loop. First entry is the header node. 70 std::vector<BlockT*> Blocks; 71 72 SmallPtrSet<const BlockT*, 8> DenseBlockSet; 73 74 LoopBase(const LoopBase<BlockT, LoopT> &) LLVM_DELETED_FUNCTION; 75 const LoopBase<BlockT, LoopT>& 76 operator=(const LoopBase<BlockT, LoopT> &) LLVM_DELETED_FUNCTION; 77public: 78 /// Loop ctor - This creates an empty loop. 79 LoopBase() : ParentLoop(0) {} 80 ~LoopBase() { 81 for (size_t i = 0, e = SubLoops.size(); i != e; ++i) 82 delete SubLoops[i]; 83 } 84 85 /// getLoopDepth - Return the nesting level of this loop. An outer-most 86 /// loop has depth 1, for consistency with loop depth values used for basic 87 /// blocks, where depth 0 is used for blocks not inside any loops. 88 unsigned getLoopDepth() const { 89 unsigned D = 1; 90 for (const LoopT *CurLoop = ParentLoop; CurLoop; 91 CurLoop = CurLoop->ParentLoop) 92 ++D; 93 return D; 94 } 95 BlockT *getHeader() const { return Blocks.front(); } 96 LoopT *getParentLoop() const { return ParentLoop; } 97 98 /// setParentLoop is a raw interface for bypassing addChildLoop. 99 void setParentLoop(LoopT *L) { ParentLoop = L; } 100 101 /// contains - Return true if the specified loop is contained within in 102 /// this loop. 103 /// 104 bool contains(const LoopT *L) const { 105 if (L == this) return true; 106 if (L == 0) return false; 107 return contains(L->getParentLoop()); 108 } 109 110 /// contains - Return true if the specified basic block is in this loop. 111 /// 112 bool contains(const BlockT *BB) const { 113 return DenseBlockSet.count(BB); 114 } 115 116 /// contains - Return true if the specified instruction is in this loop. 117 /// 118 template<class InstT> 119 bool contains(const InstT *Inst) const { 120 return contains(Inst->getParent()); 121 } 122 123 /// iterator/begin/end - Return the loops contained entirely within this loop. 124 /// 125 const std::vector<LoopT *> &getSubLoops() const { return SubLoops; } 126 std::vector<LoopT *> &getSubLoopsVector() { return SubLoops; } 127 typedef typename std::vector<LoopT *>::const_iterator iterator; 128 typedef typename std::vector<LoopT *>::const_reverse_iterator 129 reverse_iterator; 130 iterator begin() const { return SubLoops.begin(); } 131 iterator end() const { return SubLoops.end(); } 132 reverse_iterator rbegin() const { return SubLoops.rbegin(); } 133 reverse_iterator rend() const { return SubLoops.rend(); } 134 bool empty() const { return SubLoops.empty(); } 135 136 /// getBlocks - Get a list of the basic blocks which make up this loop. 137 /// 138 const std::vector<BlockT*> &getBlocks() const { return Blocks; } 139 typedef typename std::vector<BlockT*>::const_iterator block_iterator; 140 block_iterator block_begin() const { return Blocks.begin(); } 141 block_iterator block_end() const { return Blocks.end(); } 142 143 /// getNumBlocks - Get the number of blocks in this loop in constant time. 144 unsigned getNumBlocks() const { 145 return Blocks.size(); 146 } 147 148 /// isLoopExiting - True if terminator in the block can branch to another 149 /// block that is outside of the current loop. 150 /// 151 bool isLoopExiting(const BlockT *BB) const { 152 typedef GraphTraits<const BlockT*> BlockTraits; 153 for (typename BlockTraits::ChildIteratorType SI = 154 BlockTraits::child_begin(BB), 155 SE = BlockTraits::child_end(BB); SI != SE; ++SI) { 156 if (!contains(*SI)) 157 return true; 158 } 159 return false; 160 } 161 162 /// getNumBackEdges - Calculate the number of back edges to the loop header 163 /// 164 unsigned getNumBackEdges() const { 165 unsigned NumBackEdges = 0; 166 BlockT *H = getHeader(); 167 168 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 169 for (typename InvBlockTraits::ChildIteratorType I = 170 InvBlockTraits::child_begin(H), 171 E = InvBlockTraits::child_end(H); I != E; ++I) 172 if (contains(*I)) 173 ++NumBackEdges; 174 175 return NumBackEdges; 176 } 177 178 //===--------------------------------------------------------------------===// 179 // APIs for simple analysis of the loop. 180 // 181 // Note that all of these methods can fail on general loops (ie, there may not 182 // be a preheader, etc). For best success, the loop simplification and 183 // induction variable canonicalization pass should be used to normalize loops 184 // for easy analysis. These methods assume canonical loops. 185 186 /// getExitingBlocks - Return all blocks inside the loop that have successors 187 /// outside of the loop. These are the blocks _inside of the current loop_ 188 /// which branch out. The returned list is always unique. 189 /// 190 void getExitingBlocks(SmallVectorImpl<BlockT *> &ExitingBlocks) const; 191 192 /// getExitingBlock - If getExitingBlocks would return exactly one block, 193 /// return that block. Otherwise return null. 194 BlockT *getExitingBlock() const; 195 196 /// getExitBlocks - Return all of the successor blocks of this loop. These 197 /// are the blocks _outside of the current loop_ which are branched to. 198 /// 199 void getExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const; 200 201 /// getExitBlock - If getExitBlocks would return exactly one block, 202 /// return that block. Otherwise return null. 203 BlockT *getExitBlock() const; 204 205 /// Edge type. 206 typedef std::pair<const BlockT*, const BlockT*> Edge; 207 208 /// getExitEdges - Return all pairs of (_inside_block_,_outside_block_). 209 void getExitEdges(SmallVectorImpl<Edge> &ExitEdges) const; 210 211 /// getLoopPreheader - If there is a preheader for this loop, return it. A 212 /// loop has a preheader if there is only one edge to the header of the loop 213 /// from outside of the loop. If this is the case, the block branching to the 214 /// header of the loop is the preheader node. 215 /// 216 /// This method returns null if there is no preheader for the loop. 217 /// 218 BlockT *getLoopPreheader() const; 219 220 /// getLoopPredecessor - If the given loop's header has exactly one unique 221 /// predecessor outside the loop, return it. Otherwise return null. 222 /// This is less strict that the loop "preheader" concept, which requires 223 /// the predecessor to have exactly one successor. 224 /// 225 BlockT *getLoopPredecessor() const; 226 227 /// getLoopLatch - If there is a single latch block for this loop, return it. 228 /// A latch block is a block that contains a branch back to the header. 229 BlockT *getLoopLatch() const; 230 231 //===--------------------------------------------------------------------===// 232 // APIs for updating loop information after changing the CFG 233 // 234 235 /// addBasicBlockToLoop - This method is used by other analyses to update loop 236 /// information. NewBB is set to be a new member of the current loop. 237 /// Because of this, it is added as a member of all parent loops, and is added 238 /// to the specified LoopInfo object as being in the current basic block. It 239 /// is not valid to replace the loop header with this method. 240 /// 241 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LI); 242 243 /// replaceChildLoopWith - This is used when splitting loops up. It replaces 244 /// the OldChild entry in our children list with NewChild, and updates the 245 /// parent pointer of OldChild to be null and the NewChild to be this loop. 246 /// This updates the loop depth of the new child. 247 void replaceChildLoopWith(LoopT *OldChild, LoopT *NewChild); 248 249 /// addChildLoop - Add the specified loop to be a child of this loop. This 250 /// updates the loop depth of the new child. 251 /// 252 void addChildLoop(LoopT *NewChild) { 253 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 254 NewChild->ParentLoop = static_cast<LoopT *>(this); 255 SubLoops.push_back(NewChild); 256 } 257 258 /// removeChildLoop - This removes the specified child from being a subloop of 259 /// this loop. The loop is not deleted, as it will presumably be inserted 260 /// into another loop. 261 LoopT *removeChildLoop(iterator I) { 262 assert(I != SubLoops.end() && "Cannot remove end iterator!"); 263 LoopT *Child = *I; 264 assert(Child->ParentLoop == this && "Child is not a child of this loop!"); 265 SubLoops.erase(SubLoops.begin()+(I-begin())); 266 Child->ParentLoop = 0; 267 return Child; 268 } 269 270 /// addBlockEntry - This adds a basic block directly to the basic block list. 271 /// This should only be used by transformations that create new loops. Other 272 /// transformations should use addBasicBlockToLoop. 273 void addBlockEntry(BlockT *BB) { 274 Blocks.push_back(BB); 275 DenseBlockSet.insert(BB); 276 } 277 278 /// reverseBlocks - interface to reverse Blocks[from, end of loop] in this loop 279 void reverseBlock(unsigned from) { 280 std::reverse(Blocks.begin() + from, Blocks.end()); 281 } 282 283 /// reserveBlocks- interface to do reserve() for Blocks 284 void reserveBlocks(unsigned size) { 285 Blocks.reserve(size); 286 } 287 288 /// moveToHeader - This method is used to move BB (which must be part of this 289 /// loop) to be the loop header of the loop (the block that dominates all 290 /// others). 291 void moveToHeader(BlockT *BB) { 292 if (Blocks[0] == BB) return; 293 for (unsigned i = 0; ; ++i) { 294 assert(i != Blocks.size() && "Loop does not contain BB!"); 295 if (Blocks[i] == BB) { 296 Blocks[i] = Blocks[0]; 297 Blocks[0] = BB; 298 return; 299 } 300 } 301 } 302 303 /// removeBlockFromLoop - This removes the specified basic block from the 304 /// current loop, updating the Blocks as appropriate. This does not update 305 /// the mapping in the LoopInfo class. 306 void removeBlockFromLoop(BlockT *BB) { 307 RemoveFromVector(Blocks, BB); 308 DenseBlockSet.erase(BB); 309 } 310 311 /// verifyLoop - Verify loop structure 312 void verifyLoop() const; 313 314 /// verifyLoop - Verify loop structure of this loop and all nested loops. 315 void verifyLoopNest(DenseSet<const LoopT*> *Loops) const; 316 317 void print(raw_ostream &OS, unsigned Depth = 0) const; 318 319protected: 320 friend class LoopInfoBase<BlockT, LoopT>; 321 explicit LoopBase(BlockT *BB) : ParentLoop(0) { 322 Blocks.push_back(BB); 323 DenseBlockSet.insert(BB); 324 } 325}; 326 327template<class BlockT, class LoopT> 328raw_ostream& operator<<(raw_ostream &OS, const LoopBase<BlockT, LoopT> &Loop) { 329 Loop.print(OS); 330 return OS; 331} 332 333// Implementation in LoopInfoImpl.h 334#ifdef __GNUC__ 335__extension__ extern template class LoopBase<BasicBlock, Loop>; 336#endif 337 338class Loop : public LoopBase<BasicBlock, Loop> { 339public: 340 Loop() {} 341 342 /// isLoopInvariant - Return true if the specified value is loop invariant 343 /// 344 bool isLoopInvariant(Value *V) const; 345 346 /// hasLoopInvariantOperands - Return true if all the operands of the 347 /// specified instruction are loop invariant. 348 bool hasLoopInvariantOperands(Instruction *I) const; 349 350 /// makeLoopInvariant - If the given value is an instruction inside of the 351 /// loop and it can be hoisted, do so to make it trivially loop-invariant. 352 /// Return true if the value after any hoisting is loop invariant. This 353 /// function can be used as a slightly more aggressive replacement for 354 /// isLoopInvariant. 355 /// 356 /// If InsertPt is specified, it is the point to hoist instructions to. 357 /// If null, the terminator of the loop preheader is used. 358 /// 359 bool makeLoopInvariant(Value *V, bool &Changed, 360 Instruction *InsertPt = 0) const; 361 362 /// makeLoopInvariant - If the given instruction is inside of the 363 /// loop and it can be hoisted, do so to make it trivially loop-invariant. 364 /// Return true if the instruction after any hoisting is loop invariant. This 365 /// function can be used as a slightly more aggressive replacement for 366 /// isLoopInvariant. 367 /// 368 /// If InsertPt is specified, it is the point to hoist instructions to. 369 /// If null, the terminator of the loop preheader is used. 370 /// 371 bool makeLoopInvariant(Instruction *I, bool &Changed, 372 Instruction *InsertPt = 0) const; 373 374 /// getCanonicalInductionVariable - Check to see if the loop has a canonical 375 /// induction variable: an integer recurrence that starts at 0 and increments 376 /// by one each time through the loop. If so, return the phi node that 377 /// corresponds to it. 378 /// 379 /// The IndVarSimplify pass transforms loops to have a canonical induction 380 /// variable. 381 /// 382 PHINode *getCanonicalInductionVariable() const; 383 384 /// isLCSSAForm - Return true if the Loop is in LCSSA form 385 bool isLCSSAForm(DominatorTree &DT) const; 386 387 /// isLoopSimplifyForm - Return true if the Loop is in the form that 388 /// the LoopSimplify form transforms loops to, which is sometimes called 389 /// normal form. 390 bool isLoopSimplifyForm() const; 391 392 /// isSafeToClone - Return true if the loop body is safe to clone in practice. 393 bool isSafeToClone() const; 394 395 /// Returns true if the loop is annotated parallel. 396 /// 397 /// A parallel loop can be assumed to not contain any dependencies between 398 /// iterations by the compiler. That is, any loop-carried dependency checking 399 /// can be skipped completely when parallelizing the loop on the target 400 /// machine. Thus, if the parallel loop information originates from the 401 /// programmer, e.g. via the OpenMP parallel for pragma, it is the 402 /// programmer's responsibility to ensure there are no loop-carried 403 /// dependencies. The final execution order of the instructions across 404 /// iterations is not guaranteed, thus, the end result might or might not 405 /// implement actual concurrent execution of instructions across multiple 406 /// iterations. 407 bool isAnnotatedParallel() const; 408 409 /// Return the llvm.loop loop id metadata node for this loop if it is present. 410 /// 411 /// If this loop contains the same llvm.loop metadata on each branch to the 412 /// header then the node is returned. If any latch instruction does not 413 /// contain llvm.loop or or if multiple latches contain different nodes then 414 /// 0 is returned. 415 MDNode *getLoopID() const; 416 /// Set the llvm.loop loop id metadata for this loop. 417 /// 418 /// The LoopID metadata node will be added to each terminator instruction in 419 /// the loop that branches to the loop header. 420 /// 421 /// The LoopID metadata node should have one or more operands and the first 422 /// operand should should be the node itself. 423 void setLoopID(MDNode *LoopID) const; 424 425 /// hasDedicatedExits - Return true if no exit block for the loop 426 /// has a predecessor that is outside the loop. 427 bool hasDedicatedExits() const; 428 429 /// getUniqueExitBlocks - Return all unique successor blocks of this loop. 430 /// These are the blocks _outside of the current loop_ which are branched to. 431 /// This assumes that loop exits are in canonical form. 432 /// 433 void getUniqueExitBlocks(SmallVectorImpl<BasicBlock *> &ExitBlocks) const; 434 435 /// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one 436 /// block, return that block. Otherwise return null. 437 BasicBlock *getUniqueExitBlock() const; 438 439 void dump() const; 440 441private: 442 friend class LoopInfoBase<BasicBlock, Loop>; 443 explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {} 444}; 445 446//===----------------------------------------------------------------------===// 447/// LoopInfo - This class builds and contains all of the top level loop 448/// structures in the specified function. 449/// 450 451template<class BlockT, class LoopT> 452class LoopInfoBase { 453 // BBMap - Mapping of basic blocks to the inner most loop they occur in 454 DenseMap<BlockT *, LoopT *> BBMap; 455 std::vector<LoopT *> TopLevelLoops; 456 friend class LoopBase<BlockT, LoopT>; 457 friend class LoopInfo; 458 459 void operator=(const LoopInfoBase &) LLVM_DELETED_FUNCTION; 460 LoopInfoBase(const LoopInfo &) LLVM_DELETED_FUNCTION; 461public: 462 LoopInfoBase() { } 463 ~LoopInfoBase() { releaseMemory(); } 464 465 void releaseMemory() { 466 for (typename std::vector<LoopT *>::iterator I = 467 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I) 468 delete *I; // Delete all of the loops... 469 470 BBMap.clear(); // Reset internal state of analysis 471 TopLevelLoops.clear(); 472 } 473 474 /// iterator/begin/end - The interface to the top-level loops in the current 475 /// function. 476 /// 477 typedef typename std::vector<LoopT *>::const_iterator iterator; 478 typedef typename std::vector<LoopT *>::const_reverse_iterator 479 reverse_iterator; 480 iterator begin() const { return TopLevelLoops.begin(); } 481 iterator end() const { return TopLevelLoops.end(); } 482 reverse_iterator rbegin() const { return TopLevelLoops.rbegin(); } 483 reverse_iterator rend() const { return TopLevelLoops.rend(); } 484 bool empty() const { return TopLevelLoops.empty(); } 485 486 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 487 /// block is in no loop (for example the entry node), null is returned. 488 /// 489 LoopT *getLoopFor(const BlockT *BB) const { 490 return BBMap.lookup(const_cast<BlockT*>(BB)); 491 } 492 493 /// operator[] - same as getLoopFor... 494 /// 495 const LoopT *operator[](const BlockT *BB) const { 496 return getLoopFor(BB); 497 } 498 499 /// getLoopDepth - Return the loop nesting level of the specified block. A 500 /// depth of 0 means the block is not inside any loop. 501 /// 502 unsigned getLoopDepth(const BlockT *BB) const { 503 const LoopT *L = getLoopFor(BB); 504 return L ? L->getLoopDepth() : 0; 505 } 506 507 // isLoopHeader - True if the block is a loop header node 508 bool isLoopHeader(BlockT *BB) const { 509 const LoopT *L = getLoopFor(BB); 510 return L && L->getHeader() == BB; 511 } 512 513 /// removeLoop - This removes the specified top-level loop from this loop info 514 /// object. The loop is not deleted, as it will presumably be inserted into 515 /// another loop. 516 LoopT *removeLoop(iterator I) { 517 assert(I != end() && "Cannot remove end iterator!"); 518 LoopT *L = *I; 519 assert(L->getParentLoop() == 0 && "Not a top-level loop!"); 520 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin())); 521 return L; 522 } 523 524 /// changeLoopFor - Change the top-level loop that contains BB to the 525 /// specified loop. This should be used by transformations that restructure 526 /// the loop hierarchy tree. 527 void changeLoopFor(BlockT *BB, LoopT *L) { 528 if (!L) { 529 BBMap.erase(BB); 530 return; 531 } 532 BBMap[BB] = L; 533 } 534 535 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 536 /// list with the indicated loop. 537 void changeTopLevelLoop(LoopT *OldLoop, 538 LoopT *NewLoop) { 539 typename std::vector<LoopT *>::iterator I = 540 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop); 541 assert(I != TopLevelLoops.end() && "Old loop not at top level!"); 542 *I = NewLoop; 543 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 && 544 "Loops already embedded into a subloop!"); 545 } 546 547 /// addTopLevelLoop - This adds the specified loop to the collection of 548 /// top-level loops. 549 void addTopLevelLoop(LoopT *New) { 550 assert(New->getParentLoop() == 0 && "Loop already in subloop!"); 551 TopLevelLoops.push_back(New); 552 } 553 554 /// removeBlock - This method completely removes BB from all data structures, 555 /// including all of the Loop objects it is nested in and our mapping from 556 /// BasicBlocks to loops. 557 void removeBlock(BlockT *BB) { 558 typename DenseMap<BlockT *, LoopT *>::iterator I = BBMap.find(BB); 559 if (I != BBMap.end()) { 560 for (LoopT *L = I->second; L; L = L->getParentLoop()) 561 L->removeBlockFromLoop(BB); 562 563 BBMap.erase(I); 564 } 565 } 566 567 // Internals 568 569 static bool isNotAlreadyContainedIn(const LoopT *SubLoop, 570 const LoopT *ParentLoop) { 571 if (SubLoop == 0) return true; 572 if (SubLoop == ParentLoop) return false; 573 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop); 574 } 575 576 /// Create the loop forest using a stable algorithm. 577 void Analyze(DominatorTreeBase<BlockT> &DomTree); 578 579 // Debugging 580 581 void print(raw_ostream &OS) const; 582}; 583 584// Implementation in LoopInfoImpl.h 585#ifdef __GNUC__ 586__extension__ extern template class LoopInfoBase<BasicBlock, Loop>; 587#endif 588 589class LoopInfo : public FunctionPass { 590 LoopInfoBase<BasicBlock, Loop> LI; 591 friend class LoopBase<BasicBlock, Loop>; 592 593 void operator=(const LoopInfo &) LLVM_DELETED_FUNCTION; 594 LoopInfo(const LoopInfo &) LLVM_DELETED_FUNCTION; 595public: 596 static char ID; // Pass identification, replacement for typeid 597 598 LoopInfo() : FunctionPass(ID) { 599 initializeLoopInfoPass(*PassRegistry::getPassRegistry()); 600 } 601 602 LoopInfoBase<BasicBlock, Loop>& getBase() { return LI; } 603 604 /// iterator/begin/end - The interface to the top-level loops in the current 605 /// function. 606 /// 607 typedef LoopInfoBase<BasicBlock, Loop>::iterator iterator; 608 typedef LoopInfoBase<BasicBlock, Loop>::reverse_iterator reverse_iterator; 609 inline iterator begin() const { return LI.begin(); } 610 inline iterator end() const { return LI.end(); } 611 inline reverse_iterator rbegin() const { return LI.rbegin(); } 612 inline reverse_iterator rend() const { return LI.rend(); } 613 bool empty() const { return LI.empty(); } 614 615 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 616 /// block is in no loop (for example the entry node), null is returned. 617 /// 618 inline Loop *getLoopFor(const BasicBlock *BB) const { 619 return LI.getLoopFor(BB); 620 } 621 622 /// operator[] - same as getLoopFor... 623 /// 624 inline const Loop *operator[](const BasicBlock *BB) const { 625 return LI.getLoopFor(BB); 626 } 627 628 /// getLoopDepth - Return the loop nesting level of the specified block. A 629 /// depth of 0 means the block is not inside any loop. 630 /// 631 inline unsigned getLoopDepth(const BasicBlock *BB) const { 632 return LI.getLoopDepth(BB); 633 } 634 635 // isLoopHeader - True if the block is a loop header node 636 inline bool isLoopHeader(BasicBlock *BB) const { 637 return LI.isLoopHeader(BB); 638 } 639 640 /// runOnFunction - Calculate the natural loop information. 641 /// 642 virtual bool runOnFunction(Function &F); 643 644 virtual void verifyAnalysis() const; 645 646 virtual void releaseMemory() { LI.releaseMemory(); } 647 648 virtual void print(raw_ostream &O, const Module* M = 0) const; 649 650 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 651 652 /// removeLoop - This removes the specified top-level loop from this loop info 653 /// object. The loop is not deleted, as it will presumably be inserted into 654 /// another loop. 655 inline Loop *removeLoop(iterator I) { return LI.removeLoop(I); } 656 657 /// changeLoopFor - Change the top-level loop that contains BB to the 658 /// specified loop. This should be used by transformations that restructure 659 /// the loop hierarchy tree. 660 inline void changeLoopFor(BasicBlock *BB, Loop *L) { 661 LI.changeLoopFor(BB, L); 662 } 663 664 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 665 /// list with the indicated loop. 666 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) { 667 LI.changeTopLevelLoop(OldLoop, NewLoop); 668 } 669 670 /// addTopLevelLoop - This adds the specified loop to the collection of 671 /// top-level loops. 672 inline void addTopLevelLoop(Loop *New) { 673 LI.addTopLevelLoop(New); 674 } 675 676 /// removeBlock - This method completely removes BB from all data structures, 677 /// including all of the Loop objects it is nested in and our mapping from 678 /// BasicBlocks to loops. 679 void removeBlock(BasicBlock *BB) { 680 LI.removeBlock(BB); 681 } 682 683 /// updateUnloop - Update LoopInfo after removing the last backedge from a 684 /// loop--now the "unloop". This updates the loop forest and parent loops for 685 /// each block so that Unloop is no longer referenced, but the caller must 686 /// actually delete the Unloop object. 687 void updateUnloop(Loop *Unloop); 688 689 /// replacementPreservesLCSSAForm - Returns true if replacing From with To 690 /// everywhere is guaranteed to preserve LCSSA form. 691 bool replacementPreservesLCSSAForm(Instruction *From, Value *To) { 692 // Preserving LCSSA form is only problematic if the replacing value is an 693 // instruction. 694 Instruction *I = dyn_cast<Instruction>(To); 695 if (!I) return true; 696 // If both instructions are defined in the same basic block then replacement 697 // cannot break LCSSA form. 698 if (I->getParent() == From->getParent()) 699 return true; 700 // If the instruction is not defined in a loop then it can safely replace 701 // anything. 702 Loop *ToLoop = getLoopFor(I->getParent()); 703 if (!ToLoop) return true; 704 // If the replacing instruction is defined in the same loop as the original 705 // instruction, or in a loop that contains it as an inner loop, then using 706 // it as a replacement will not break LCSSA form. 707 return ToLoop->contains(getLoopFor(From->getParent())); 708 } 709}; 710 711 712// Allow clients to walk the list of nested loops... 713template <> struct GraphTraits<const Loop*> { 714 typedef const Loop NodeType; 715 typedef LoopInfo::iterator ChildIteratorType; 716 717 static NodeType *getEntryNode(const Loop *L) { return L; } 718 static inline ChildIteratorType child_begin(NodeType *N) { 719 return N->begin(); 720 } 721 static inline ChildIteratorType child_end(NodeType *N) { 722 return N->end(); 723 } 724}; 725 726template <> struct GraphTraits<Loop*> { 727 typedef Loop NodeType; 728 typedef LoopInfo::iterator ChildIteratorType; 729 730 static NodeType *getEntryNode(Loop *L) { return L; } 731 static inline ChildIteratorType child_begin(NodeType *N) { 732 return N->begin(); 733 } 734 static inline ChildIteratorType child_end(NodeType *N) { 735 return N->end(); 736 } 737}; 738 739} // End llvm namespace 740 741#endif 742