LoopInfo.h revision cbf24b4e58c2f621f480883c5bb1f2f2b2b8d497
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> 49static 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 // DO NOT IMPLEMENT 76 LoopBase(const LoopBase<BlockT, LoopT> &); 77 // DO NOT IMPLEMENT 78 const LoopBase<BlockT, LoopT>&operator=(const LoopBase<BlockT, LoopT> &); 79public: 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 /// contains - Return true if the specified loop is contained within in 101 /// this loop. 102 /// 103 bool contains(const LoopT *L) const { 104 if (L == this) return true; 105 if (L == 0) return false; 106 return contains(L->getParentLoop()); 107 } 108 109 /// contains - Return true if the specified basic block is in this loop. 110 /// 111 bool contains(const BlockT *BB) const { 112 return std::find(block_begin(), block_end(), BB) != block_end(); 113 } 114 115 /// contains - Return true if the specified instruction is in this loop. 116 /// 117 template<class InstT> 118 bool contains(const InstT *Inst) const { 119 return contains(Inst->getParent()); 120 } 121 122 /// iterator/begin/end - Return the loops contained entirely within this loop. 123 /// 124 const std::vector<LoopT *> &getSubLoops() const { return SubLoops; } 125 typedef typename std::vector<LoopT *>::const_iterator iterator; 126 iterator begin() const { return SubLoops.begin(); } 127 iterator end() const { return SubLoops.end(); } 128 bool empty() const { return SubLoops.empty(); } 129 130 /// getBlocks - Get a list of the basic blocks which make up this loop. 131 /// 132 const std::vector<BlockT*> &getBlocks() const { return Blocks; } 133 typedef typename std::vector<BlockT*>::const_iterator block_iterator; 134 block_iterator block_begin() const { return Blocks.begin(); } 135 block_iterator block_end() const { return Blocks.end(); } 136 137 /// getNumBlocks - Get the number of blocks in this loop in constant time. 138 unsigned getNumBlocks() const { 139 return Blocks.size(); 140 } 141 142 /// isLoopExiting - True if terminator in the block can branch to another 143 /// block that is outside of the current loop. 144 /// 145 bool isLoopExiting(const BlockT *BB) const { 146 typedef GraphTraits<BlockT*> BlockTraits; 147 for (typename BlockTraits::ChildIteratorType SI = 148 BlockTraits::child_begin(const_cast<BlockT*>(BB)), 149 SE = BlockTraits::child_end(const_cast<BlockT*>(BB)); SI != SE; ++SI) { 150 if (!contains(*SI)) 151 return true; 152 } 153 return false; 154 } 155 156 /// getNumBackEdges - Calculate the number of back edges to the loop header 157 /// 158 unsigned getNumBackEdges() const { 159 unsigned NumBackEdges = 0; 160 BlockT *H = getHeader(); 161 162 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 163 for (typename InvBlockTraits::ChildIteratorType I = 164 InvBlockTraits::child_begin(const_cast<BlockT*>(H)), 165 E = InvBlockTraits::child_end(const_cast<BlockT*>(H)); I != E; ++I) 166 if (contains(*I)) 167 ++NumBackEdges; 168 169 return NumBackEdges; 170 } 171 172 //===--------------------------------------------------------------------===// 173 // APIs for simple analysis of the loop. 174 // 175 // Note that all of these methods can fail on general loops (ie, there may not 176 // be a preheader, etc). For best success, the loop simplification and 177 // induction variable canonicalization pass should be used to normalize loops 178 // for easy analysis. These methods assume canonical loops. 179 180 /// getExitingBlocks - Return all blocks inside the loop that have successors 181 /// outside of the loop. These are the blocks _inside of the current loop_ 182 /// which branch out. The returned list is always unique. 183 /// 184 void getExitingBlocks(SmallVectorImpl<BlockT *> &ExitingBlocks) const; 185 186 /// getExitingBlock - If getExitingBlocks would return exactly one block, 187 /// return that block. Otherwise return null. 188 BlockT *getExitingBlock() const; 189 190 /// getExitBlocks - Return all of the successor blocks of this loop. These 191 /// are the blocks _outside of the current loop_ which are branched to. 192 /// 193 void getExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const; 194 195 /// getExitBlock - If getExitBlocks would return exactly one block, 196 /// return that block. Otherwise return null. 197 BlockT *getExitBlock() const; 198 199 /// Edge type. 200 typedef std::pair<const BlockT*, const BlockT*> Edge; 201 202 /// getExitEdges - Return all pairs of (_inside_block_,_outside_block_). 203 void getExitEdges(SmallVectorImpl<Edge> &ExitEdges) const; 204 205 /// getLoopPreheader - If there is a preheader for this loop, return it. A 206 /// loop has a preheader if there is only one edge to the header of the loop 207 /// from outside of the loop. If this is the case, the block branching to the 208 /// header of the loop is the preheader node. 209 /// 210 /// This method returns null if there is no preheader for the loop. 211 /// 212 BlockT *getLoopPreheader() const; 213 214 /// getLoopPredecessor - If the given loop's header has exactly one unique 215 /// predecessor outside the loop, return it. Otherwise return null. 216 /// This is less strict that the loop "preheader" concept, which requires 217 /// the predecessor to have exactly one successor. 218 /// 219 BlockT *getLoopPredecessor() const; 220 221 /// getLoopLatch - If there is a single latch block for this loop, return it. 222 /// A latch block is a block that contains a branch back to the header. 223 BlockT *getLoopLatch() const; 224 225 //===--------------------------------------------------------------------===// 226 // APIs for updating loop information after changing the CFG 227 // 228 229 /// addBasicBlockToLoop - This method is used by other analyses to update loop 230 /// information. NewBB is set to be a new member of the current loop. 231 /// Because of this, it is added as a member of all parent loops, and is added 232 /// to the specified LoopInfo object as being in the current basic block. It 233 /// is not valid to replace the loop header with this method. 234 /// 235 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LI); 236 237 /// replaceChildLoopWith - This is used when splitting loops up. It replaces 238 /// the OldChild entry in our children list with NewChild, and updates the 239 /// parent pointer of OldChild to be null and the NewChild to be this loop. 240 /// This updates the loop depth of the new child. 241 void replaceChildLoopWith(LoopT *OldChild, LoopT *NewChild); 242 243 /// addChildLoop - Add the specified loop to be a child of this loop. This 244 /// updates the loop depth of the new child. 245 /// 246 void addChildLoop(LoopT *NewChild) { 247 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 248 NewChild->ParentLoop = static_cast<LoopT *>(this); 249 SubLoops.push_back(NewChild); 250 } 251 252 /// removeChildLoop - This removes the specified child from being a subloop of 253 /// this loop. The loop is not deleted, as it will presumably be inserted 254 /// into another loop. 255 LoopT *removeChildLoop(iterator I) { 256 assert(I != SubLoops.end() && "Cannot remove end iterator!"); 257 LoopT *Child = *I; 258 assert(Child->ParentLoop == this && "Child is not a child of this loop!"); 259 SubLoops.erase(SubLoops.begin()+(I-begin())); 260 Child->ParentLoop = 0; 261 return Child; 262 } 263 264 /// addBlockEntry - This adds a basic block directly to the basic block list. 265 /// This should only be used by transformations that create new loops. Other 266 /// transformations should use addBasicBlockToLoop. 267 void addBlockEntry(BlockT *BB) { 268 Blocks.push_back(BB); 269 } 270 271 /// moveToHeader - This method is used to move BB (which must be part of this 272 /// loop) to be the loop header of the loop (the block that dominates all 273 /// others). 274 void moveToHeader(BlockT *BB) { 275 if (Blocks[0] == BB) return; 276 for (unsigned i = 0; ; ++i) { 277 assert(i != Blocks.size() && "Loop does not contain BB!"); 278 if (Blocks[i] == BB) { 279 Blocks[i] = Blocks[0]; 280 Blocks[0] = BB; 281 return; 282 } 283 } 284 } 285 286 /// removeBlockFromLoop - This removes the specified basic block from the 287 /// current loop, updating the Blocks as appropriate. This does not update 288 /// the mapping in the LoopInfo class. 289 void removeBlockFromLoop(BlockT *BB) { 290 RemoveFromVector(Blocks, BB); 291 } 292 293 /// verifyLoop - Verify loop structure 294 void verifyLoop() const; 295 296 /// verifyLoop - Verify loop structure of this loop and all nested loops. 297 void verifyLoopNest(DenseSet<const LoopT*> *Loops) const; 298 299 void print(raw_ostream &OS, unsigned Depth = 0) const; 300 301protected: 302 friend class LoopInfoBase<BlockT, LoopT>; 303 explicit LoopBase(BlockT *BB) : ParentLoop(0) { 304 Blocks.push_back(BB); 305 } 306}; 307 308template<class BlockT, class LoopT> 309raw_ostream& operator<<(raw_ostream &OS, const LoopBase<BlockT, LoopT> &Loop) { 310 Loop.print(OS); 311 return OS; 312} 313 314class Loop : public LoopBase<BasicBlock, Loop> { 315public: 316 Loop() {} 317 318 /// isLoopInvariant - Return true if the specified value is loop invariant 319 /// 320 bool isLoopInvariant(Value *V) const; 321 322 /// hasLoopInvariantOperands - Return true if all the operands of the 323 /// specified instruction are loop invariant. 324 bool hasLoopInvariantOperands(Instruction *I) const; 325 326 /// makeLoopInvariant - If the given value is an instruction inside of the 327 /// loop and it can be hoisted, do so to make it trivially loop-invariant. 328 /// Return true if the value after any hoisting is loop invariant. This 329 /// function can be used as a slightly more aggressive replacement for 330 /// isLoopInvariant. 331 /// 332 /// If InsertPt is specified, it is the point to hoist instructions to. 333 /// If null, the terminator of the loop preheader is used. 334 /// 335 bool makeLoopInvariant(Value *V, bool &Changed, 336 Instruction *InsertPt = 0) const; 337 338 /// makeLoopInvariant - If the given instruction is inside of the 339 /// loop and it can be hoisted, do so to make it trivially loop-invariant. 340 /// Return true if the instruction after any hoisting is loop invariant. This 341 /// function can be used as a slightly more aggressive replacement for 342 /// isLoopInvariant. 343 /// 344 /// If InsertPt is specified, it is the point to hoist instructions to. 345 /// If null, the terminator of the loop preheader is used. 346 /// 347 bool makeLoopInvariant(Instruction *I, bool &Changed, 348 Instruction *InsertPt = 0) const; 349 350 /// getCanonicalInductionVariable - Check to see if the loop has a canonical 351 /// induction variable: an integer recurrence that starts at 0 and increments 352 /// by one each time through the loop. If so, return the phi node that 353 /// corresponds to it. 354 /// 355 /// The IndVarSimplify pass transforms loops to have a canonical induction 356 /// variable. 357 /// 358 PHINode *getCanonicalInductionVariable() const; 359 360 /// isLCSSAForm - Return true if the Loop is in LCSSA form 361 bool isLCSSAForm(DominatorTree &DT) const; 362 363 /// isLoopSimplifyForm - Return true if the Loop is in the form that 364 /// the LoopSimplify form transforms loops to, which is sometimes called 365 /// normal form. 366 bool isLoopSimplifyForm() const; 367 368 /// isSafeToClone - Return true if the loop body is safe to clone in practice. 369 bool isSafeToClone() const; 370 371 /// hasDedicatedExits - Return true if no exit block for the loop 372 /// has a predecessor that is outside the loop. 373 bool hasDedicatedExits() const; 374 375 /// getUniqueExitBlocks - Return all unique successor blocks of this loop. 376 /// These are the blocks _outside of the current loop_ which are branched to. 377 /// This assumes that loop exits are in canonical form. 378 /// 379 void getUniqueExitBlocks(SmallVectorImpl<BasicBlock *> &ExitBlocks) const; 380 381 /// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one 382 /// block, return that block. Otherwise return null. 383 BasicBlock *getUniqueExitBlock() const; 384 385 void dump() const; 386 387private: 388 friend class LoopInfoBase<BasicBlock, Loop>; 389 explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {} 390}; 391 392//===----------------------------------------------------------------------===// 393/// LoopInfo - This class builds and contains all of the top level loop 394/// structures in the specified function. 395/// 396 397template<class BlockT, class LoopT> 398class LoopInfoBase { 399 // BBMap - Mapping of basic blocks to the inner most loop they occur in 400 DenseMap<BlockT *, LoopT *> BBMap; 401 std::vector<LoopT *> TopLevelLoops; 402 friend class LoopBase<BlockT, LoopT>; 403 friend class LoopInfo; 404 405 void operator=(const LoopInfoBase &); // do not implement 406 LoopInfoBase(const LoopInfo &); // do not implement 407public: 408 LoopInfoBase() { } 409 ~LoopInfoBase() { releaseMemory(); } 410 411 void releaseMemory() { 412 for (typename std::vector<LoopT *>::iterator I = 413 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I) 414 delete *I; // Delete all of the loops... 415 416 BBMap.clear(); // Reset internal state of analysis 417 TopLevelLoops.clear(); 418 } 419 420 /// iterator/begin/end - The interface to the top-level loops in the current 421 /// function. 422 /// 423 typedef typename std::vector<LoopT *>::const_iterator iterator; 424 iterator begin() const { return TopLevelLoops.begin(); } 425 iterator end() const { return TopLevelLoops.end(); } 426 bool empty() const { return TopLevelLoops.empty(); } 427 428 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 429 /// block is in no loop (for example the entry node), null is returned. 430 /// 431 LoopT *getLoopFor(const BlockT *BB) const { 432 return BBMap.lookup(const_cast<BlockT*>(BB)); 433 } 434 435 /// operator[] - same as getLoopFor... 436 /// 437 const LoopT *operator[](const BlockT *BB) const { 438 return getLoopFor(BB); 439 } 440 441 /// getLoopDepth - Return the loop nesting level of the specified block. A 442 /// depth of 0 means the block is not inside any loop. 443 /// 444 unsigned getLoopDepth(const BlockT *BB) const { 445 const LoopT *L = getLoopFor(BB); 446 return L ? L->getLoopDepth() : 0; 447 } 448 449 // isLoopHeader - True if the block is a loop header node 450 bool isLoopHeader(BlockT *BB) const { 451 const LoopT *L = getLoopFor(BB); 452 return L && L->getHeader() == BB; 453 } 454 455 /// removeLoop - This removes the specified top-level loop from this loop info 456 /// object. The loop is not deleted, as it will presumably be inserted into 457 /// another loop. 458 LoopT *removeLoop(iterator I) { 459 assert(I != end() && "Cannot remove end iterator!"); 460 LoopT *L = *I; 461 assert(L->getParentLoop() == 0 && "Not a top-level loop!"); 462 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin())); 463 return L; 464 } 465 466 /// changeLoopFor - Change the top-level loop that contains BB to the 467 /// specified loop. This should be used by transformations that restructure 468 /// the loop hierarchy tree. 469 void changeLoopFor(BlockT *BB, LoopT *L) { 470 if (!L) { 471 BBMap.erase(BB); 472 return; 473 } 474 BBMap[BB] = L; 475 } 476 477 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 478 /// list with the indicated loop. 479 void changeTopLevelLoop(LoopT *OldLoop, 480 LoopT *NewLoop) { 481 typename std::vector<LoopT *>::iterator I = 482 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop); 483 assert(I != TopLevelLoops.end() && "Old loop not at top level!"); 484 *I = NewLoop; 485 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 && 486 "Loops already embedded into a subloop!"); 487 } 488 489 /// addTopLevelLoop - This adds the specified loop to the collection of 490 /// top-level loops. 491 void addTopLevelLoop(LoopT *New) { 492 assert(New->getParentLoop() == 0 && "Loop already in subloop!"); 493 TopLevelLoops.push_back(New); 494 } 495 496 /// removeBlock - This method completely removes BB from all data structures, 497 /// including all of the Loop objects it is nested in and our mapping from 498 /// BasicBlocks to loops. 499 void removeBlock(BlockT *BB) { 500 typename DenseMap<BlockT *, LoopT *>::iterator I = BBMap.find(BB); 501 if (I != BBMap.end()) { 502 for (LoopT *L = I->second; L; L = L->getParentLoop()) 503 L->removeBlockFromLoop(BB); 504 505 BBMap.erase(I); 506 } 507 } 508 509 // Internals 510 511 static bool isNotAlreadyContainedIn(const LoopT *SubLoop, 512 const LoopT *ParentLoop) { 513 if (SubLoop == 0) return true; 514 if (SubLoop == ParentLoop) return false; 515 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop); 516 } 517 518 void Calculate(DominatorTreeBase<BlockT> &DT); 519 520 LoopT *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT); 521 522 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside 523 /// of the NewParent Loop, instead of being a sibling of it. 524 void MoveSiblingLoopInto(LoopT *NewChild, LoopT *NewParent); 525 526 /// InsertLoopInto - This inserts loop L into the specified parent loop. If 527 /// the parent loop contains a loop which should contain L, the loop gets 528 /// inserted into L instead. 529 void InsertLoopInto(LoopT *L, LoopT *Parent); 530 531 // Debugging 532 533 void print(raw_ostream &OS) const; 534}; 535 536class LoopInfo : public FunctionPass { 537 LoopInfoBase<BasicBlock, Loop> LI; 538 friend class LoopBase<BasicBlock, Loop>; 539 540 void operator=(const LoopInfo &); // do not implement 541 LoopInfo(const LoopInfo &); // do not implement 542public: 543 static char ID; // Pass identification, replacement for typeid 544 545 LoopInfo() : FunctionPass(ID) { 546 initializeLoopInfoPass(*PassRegistry::getPassRegistry()); 547 } 548 549 LoopInfoBase<BasicBlock, Loop>& getBase() { return LI; } 550 551 /// iterator/begin/end - The interface to the top-level loops in the current 552 /// function. 553 /// 554 typedef LoopInfoBase<BasicBlock, Loop>::iterator iterator; 555 inline iterator begin() const { return LI.begin(); } 556 inline iterator end() const { return LI.end(); } 557 bool empty() const { return LI.empty(); } 558 559 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 560 /// block is in no loop (for example the entry node), null is returned. 561 /// 562 inline Loop *getLoopFor(const BasicBlock *BB) const { 563 return LI.getLoopFor(BB); 564 } 565 566 /// operator[] - same as getLoopFor... 567 /// 568 inline const Loop *operator[](const BasicBlock *BB) const { 569 return LI.getLoopFor(BB); 570 } 571 572 /// getLoopDepth - Return the loop nesting level of the specified block. A 573 /// depth of 0 means the block is not inside any loop. 574 /// 575 inline unsigned getLoopDepth(const BasicBlock *BB) const { 576 return LI.getLoopDepth(BB); 577 } 578 579 // isLoopHeader - True if the block is a loop header node 580 inline bool isLoopHeader(BasicBlock *BB) const { 581 return LI.isLoopHeader(BB); 582 } 583 584 /// runOnFunction - Calculate the natural loop information. 585 /// 586 virtual bool runOnFunction(Function &F); 587 588 virtual void verifyAnalysis() const; 589 590 virtual void releaseMemory() { LI.releaseMemory(); } 591 592 virtual void print(raw_ostream &O, const Module* M = 0) const; 593 594 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 595 596 /// removeLoop - This removes the specified top-level loop from this loop info 597 /// object. The loop is not deleted, as it will presumably be inserted into 598 /// another loop. 599 inline Loop *removeLoop(iterator I) { return LI.removeLoop(I); } 600 601 /// changeLoopFor - Change the top-level loop that contains BB to the 602 /// specified loop. This should be used by transformations that restructure 603 /// the loop hierarchy tree. 604 inline void changeLoopFor(BasicBlock *BB, Loop *L) { 605 LI.changeLoopFor(BB, L); 606 } 607 608 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 609 /// list with the indicated loop. 610 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) { 611 LI.changeTopLevelLoop(OldLoop, NewLoop); 612 } 613 614 /// addTopLevelLoop - This adds the specified loop to the collection of 615 /// top-level loops. 616 inline void addTopLevelLoop(Loop *New) { 617 LI.addTopLevelLoop(New); 618 } 619 620 /// removeBlock - This method completely removes BB from all data structures, 621 /// including all of the Loop objects it is nested in and our mapping from 622 /// BasicBlocks to loops. 623 void removeBlock(BasicBlock *BB) { 624 LI.removeBlock(BB); 625 } 626 627 /// updateUnloop - Update LoopInfo after removing the last backedge from a 628 /// loop--now the "unloop". This updates the loop forest and parent loops for 629 /// each block so that Unloop is no longer referenced, but the caller must 630 /// actually delete the Unloop object. 631 void updateUnloop(Loop *Unloop); 632 633 /// replacementPreservesLCSSAForm - Returns true if replacing From with To 634 /// everywhere is guaranteed to preserve LCSSA form. 635 bool replacementPreservesLCSSAForm(Instruction *From, Value *To) { 636 // Preserving LCSSA form is only problematic if the replacing value is an 637 // instruction. 638 Instruction *I = dyn_cast<Instruction>(To); 639 if (!I) return true; 640 // If both instructions are defined in the same basic block then replacement 641 // cannot break LCSSA form. 642 if (I->getParent() == From->getParent()) 643 return true; 644 // If the instruction is not defined in a loop then it can safely replace 645 // anything. 646 Loop *ToLoop = getLoopFor(I->getParent()); 647 if (!ToLoop) return true; 648 // If the replacing instruction is defined in the same loop as the original 649 // instruction, or in a loop that contains it as an inner loop, then using 650 // it as a replacement will not break LCSSA form. 651 return ToLoop->contains(getLoopFor(From->getParent())); 652 } 653}; 654 655 656// Allow clients to walk the list of nested loops... 657template <> struct GraphTraits<const Loop*> { 658 typedef const Loop NodeType; 659 typedef LoopInfo::iterator ChildIteratorType; 660 661 static NodeType *getEntryNode(const Loop *L) { return L; } 662 static inline ChildIteratorType child_begin(NodeType *N) { 663 return N->begin(); 664 } 665 static inline ChildIteratorType child_end(NodeType *N) { 666 return N->end(); 667 } 668}; 669 670template <> struct GraphTraits<Loop*> { 671 typedef Loop NodeType; 672 typedef LoopInfo::iterator ChildIteratorType; 673 674 static NodeType *getEntryNode(Loop *L) { return L; } 675 static inline ChildIteratorType child_begin(NodeType *N) { 676 return N->begin(); 677 } 678 static inline ChildIteratorType child_end(NodeType *N) { 679 return N->end(); 680 } 681}; 682 683} // End llvm namespace 684 685#endif 686