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