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