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/SmallPtrSet.h" 37 #include "llvm/ADT/SmallVector.h" 38 #include "llvm/IR/CFG.h" 39 #include "llvm/IR/Instruction.h" 40 #include "llvm/Pass.h" 41 #include <algorithm> 42 43 namespace llvm { 44 45 template<typename T> 46 inline void RemoveFromVector(std::vector<T*> &V, T *N) { 47 typename std::vector<T*>::iterator I = std::find(V.begin(), V.end(), N); 48 assert(I != V.end() && "N is not in this list!"); 49 V.erase(I); 50 } 51 52 class DominatorTree; 53 class LoopInfo; 54 class Loop; 55 class MDNode; 56 class PHINode; 57 class raw_ostream; 58 template<class N> class DominatorTreeBase; 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 SmallPtrSet<const BlockT*, 8> DenseBlockSet; 76 77 LoopBase(const LoopBase<BlockT, LoopT> &) LLVM_DELETED_FUNCTION; 78 const LoopBase<BlockT, LoopT>& 79 operator=(const LoopBase<BlockT, LoopT> &) LLVM_DELETED_FUNCTION; 80 public: 81 /// Loop ctor - This creates an empty loop. 82 LoopBase() : ParentLoop(nullptr) {} 83 ~LoopBase() { 84 for (size_t i = 0, e = SubLoops.size(); i != e; ++i) 85 delete SubLoops[i]; 86 } 87 88 /// getLoopDepth - Return the nesting level of this loop. An outer-most 89 /// loop has depth 1, for consistency with loop depth values used for basic 90 /// blocks, where depth 0 is used for blocks not inside any loops. 91 unsigned getLoopDepth() const { 92 unsigned D = 1; 93 for (const LoopT *CurLoop = ParentLoop; CurLoop; 94 CurLoop = CurLoop->ParentLoop) 95 ++D; 96 return D; 97 } 98 BlockT *getHeader() const { return Blocks.front(); } 99 LoopT *getParentLoop() const { return ParentLoop; } 100 101 /// setParentLoop is a raw interface for bypassing addChildLoop. 102 void setParentLoop(LoopT *L) { ParentLoop = L; } 103 104 /// contains - Return true if the specified loop is contained within in 105 /// this loop. 106 /// 107 bool contains(const LoopT *L) const { 108 if (L == this) return true; 109 if (!L) return false; 110 return contains(L->getParentLoop()); 111 } 112 113 /// contains - Return true if the specified basic block is in this loop. 114 /// 115 bool contains(const BlockT *BB) const { 116 return DenseBlockSet.count(BB); 117 } 118 119 /// contains - Return true if the specified instruction is in this loop. 120 /// 121 template<class InstT> 122 bool contains(const InstT *Inst) const { 123 return contains(Inst->getParent()); 124 } 125 126 /// iterator/begin/end - Return the loops contained entirely within this loop. 127 /// 128 const std::vector<LoopT *> &getSubLoops() const { return SubLoops; } 129 std::vector<LoopT *> &getSubLoopsVector() { return SubLoops; } 130 typedef typename std::vector<LoopT *>::const_iterator iterator; 131 typedef typename std::vector<LoopT *>::const_reverse_iterator 132 reverse_iterator; 133 iterator begin() const { return SubLoops.begin(); } 134 iterator end() const { return SubLoops.end(); } 135 reverse_iterator rbegin() const { return SubLoops.rbegin(); } 136 reverse_iterator rend() const { return SubLoops.rend(); } 137 bool empty() const { return SubLoops.empty(); } 138 139 /// getBlocks - Get a list of the basic blocks which make up this loop. 140 /// 141 const std::vector<BlockT*> &getBlocks() const { 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<const BlockT*> BlockTraits; 156 for (typename BlockTraits::ChildIteratorType SI = 157 BlockTraits::child_begin(BB), 158 SE = BlockTraits::child_end(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(H), 174 E = InvBlockTraits::child_end(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 /// getLoopLatches - Return all loop latch blocks of this loop. A latch block 235 /// is a block that contains a branch back to the header. 236 void getLoopLatches(SmallVectorImpl<BlockT *> &LoopLatches) const { 237 BlockT *H = getHeader(); 238 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 239 for (typename InvBlockTraits::ChildIteratorType I = 240 InvBlockTraits::child_begin(H), 241 E = InvBlockTraits::child_end(H); I != E; ++I) 242 if (contains(*I)) 243 LoopLatches.push_back(*I); 244 } 245 246 //===--------------------------------------------------------------------===// 247 // APIs for updating loop information after changing the CFG 248 // 249 250 /// addBasicBlockToLoop - This method is used by other analyses to update loop 251 /// information. NewBB is set to be a new member of the current loop. 252 /// Because of this, it is added as a member of all parent loops, and is added 253 /// to the specified LoopInfo object as being in the current basic block. It 254 /// is not valid to replace the loop header with this method. 255 /// 256 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LI); 257 258 /// replaceChildLoopWith - This is used when splitting loops up. It replaces 259 /// the OldChild entry in our children list with NewChild, and updates the 260 /// parent pointer of OldChild to be null and the NewChild to be this loop. 261 /// This updates the loop depth of the new child. 262 void replaceChildLoopWith(LoopT *OldChild, LoopT *NewChild); 263 264 /// addChildLoop - Add the specified loop to be a child of this loop. This 265 /// updates the loop depth of the new child. 266 /// 267 void addChildLoop(LoopT *NewChild) { 268 assert(!NewChild->ParentLoop && "NewChild already has a parent!"); 269 NewChild->ParentLoop = static_cast<LoopT *>(this); 270 SubLoops.push_back(NewChild); 271 } 272 273 /// removeChildLoop - This removes the specified child from being a subloop of 274 /// this loop. The loop is not deleted, as it will presumably be inserted 275 /// into another loop. 276 LoopT *removeChildLoop(iterator I) { 277 assert(I != SubLoops.end() && "Cannot remove end iterator!"); 278 LoopT *Child = *I; 279 assert(Child->ParentLoop == this && "Child is not a child of this loop!"); 280 SubLoops.erase(SubLoops.begin()+(I-begin())); 281 Child->ParentLoop = nullptr; 282 return Child; 283 } 284 285 /// addBlockEntry - This adds a basic block directly to the basic block list. 286 /// This should only be used by transformations that create new loops. Other 287 /// transformations should use addBasicBlockToLoop. 288 void addBlockEntry(BlockT *BB) { 289 Blocks.push_back(BB); 290 DenseBlockSet.insert(BB); 291 } 292 293 /// reverseBlocks - interface to reverse Blocks[from, end of loop] in this loop 294 void reverseBlock(unsigned from) { 295 std::reverse(Blocks.begin() + from, Blocks.end()); 296 } 297 298 /// reserveBlocks- interface to do reserve() for Blocks 299 void reserveBlocks(unsigned size) { 300 Blocks.reserve(size); 301 } 302 303 /// moveToHeader - This method is used to move BB (which must be part of this 304 /// loop) to be the loop header of the loop (the block that dominates all 305 /// others). 306 void moveToHeader(BlockT *BB) { 307 if (Blocks[0] == BB) return; 308 for (unsigned i = 0; ; ++i) { 309 assert(i != Blocks.size() && "Loop does not contain BB!"); 310 if (Blocks[i] == BB) { 311 Blocks[i] = Blocks[0]; 312 Blocks[0] = BB; 313 return; 314 } 315 } 316 } 317 318 /// removeBlockFromLoop - This removes the specified basic block from the 319 /// current loop, updating the Blocks as appropriate. This does not update 320 /// the mapping in the LoopInfo class. 321 void removeBlockFromLoop(BlockT *BB) { 322 RemoveFromVector(Blocks, BB); 323 DenseBlockSet.erase(BB); 324 } 325 326 /// verifyLoop - Verify loop structure 327 void verifyLoop() const; 328 329 /// verifyLoop - Verify loop structure of this loop and all nested loops. 330 void verifyLoopNest(DenseSet<const LoopT*> *Loops) const; 331 332 void print(raw_ostream &OS, unsigned Depth = 0) const; 333 334 protected: 335 friend class LoopInfoBase<BlockT, LoopT>; 336 explicit LoopBase(BlockT *BB) : ParentLoop(nullptr) { 337 Blocks.push_back(BB); 338 DenseBlockSet.insert(BB); 339 } 340 }; 341 342 template<class BlockT, class LoopT> 343 raw_ostream& operator<<(raw_ostream &OS, const LoopBase<BlockT, LoopT> &Loop) { 344 Loop.print(OS); 345 return OS; 346 } 347 348 // Implementation in LoopInfoImpl.h 349 #ifdef __GNUC__ 350 __extension__ extern template class LoopBase<BasicBlock, Loop>; 351 #endif 352 353 class Loop : public LoopBase<BasicBlock, Loop> { 354 public: 355 Loop() {} 356 357 /// isLoopInvariant - Return true if the specified value is loop invariant 358 /// 359 bool isLoopInvariant(Value *V) const; 360 361 /// hasLoopInvariantOperands - Return true if all the operands of the 362 /// specified instruction are loop invariant. 363 bool hasLoopInvariantOperands(Instruction *I) const; 364 365 /// makeLoopInvariant - If the given value is an instruction inside of the 366 /// loop and it can be hoisted, do so to make it trivially loop-invariant. 367 /// Return true if the value after any hoisting is loop invariant. This 368 /// function can be used as a slightly more aggressive replacement for 369 /// isLoopInvariant. 370 /// 371 /// If InsertPt is specified, it is the point to hoist instructions to. 372 /// If null, the terminator of the loop preheader is used. 373 /// 374 bool makeLoopInvariant(Value *V, bool &Changed, 375 Instruction *InsertPt = nullptr) const; 376 377 /// makeLoopInvariant - If the given instruction is inside of the 378 /// loop and it can be hoisted, do so to make it trivially loop-invariant. 379 /// Return true if the instruction after any hoisting is loop invariant. This 380 /// function can be used as a slightly more aggressive replacement for 381 /// isLoopInvariant. 382 /// 383 /// If InsertPt is specified, it is the point to hoist instructions to. 384 /// If null, the terminator of the loop preheader is used. 385 /// 386 bool makeLoopInvariant(Instruction *I, bool &Changed, 387 Instruction *InsertPt = nullptr) const; 388 389 /// getCanonicalInductionVariable - Check to see if the loop has a canonical 390 /// induction variable: an integer recurrence that starts at 0 and increments 391 /// by one each time through the loop. If so, return the phi node that 392 /// corresponds to it. 393 /// 394 /// The IndVarSimplify pass transforms loops to have a canonical induction 395 /// variable. 396 /// 397 PHINode *getCanonicalInductionVariable() const; 398 399 /// isLCSSAForm - Return true if the Loop is in LCSSA form 400 bool isLCSSAForm(DominatorTree &DT) const; 401 402 /// isLoopSimplifyForm - Return true if the Loop is in the form that 403 /// the LoopSimplify form transforms loops to, which is sometimes called 404 /// normal form. 405 bool isLoopSimplifyForm() const; 406 407 /// isSafeToClone - Return true if the loop body is safe to clone in practice. 408 bool isSafeToClone() const; 409 410 /// Returns true if the loop is annotated parallel. 411 /// 412 /// A parallel loop can be assumed to not contain any dependencies between 413 /// iterations by the compiler. That is, any loop-carried dependency checking 414 /// can be skipped completely when parallelizing the loop on the target 415 /// machine. Thus, if the parallel loop information originates from the 416 /// programmer, e.g. via the OpenMP parallel for pragma, it is the 417 /// programmer's responsibility to ensure there are no loop-carried 418 /// dependencies. The final execution order of the instructions across 419 /// iterations is not guaranteed, thus, the end result might or might not 420 /// implement actual concurrent execution of instructions across multiple 421 /// iterations. 422 bool isAnnotatedParallel() const; 423 424 /// Return the llvm.loop loop id metadata node for this loop if it is present. 425 /// 426 /// If this loop contains the same llvm.loop metadata on each branch to the 427 /// header then the node is returned. If any latch instruction does not 428 /// contain llvm.loop or or if multiple latches contain different nodes then 429 /// 0 is returned. 430 MDNode *getLoopID() const; 431 /// Set the llvm.loop loop id metadata for this loop. 432 /// 433 /// The LoopID metadata node will be added to each terminator instruction in 434 /// the loop that branches to the loop header. 435 /// 436 /// The LoopID metadata node should have one or more operands and the first 437 /// operand should should be the node itself. 438 void setLoopID(MDNode *LoopID) const; 439 440 /// hasDedicatedExits - Return true if no exit block for the loop 441 /// has a predecessor that is outside the loop. 442 bool hasDedicatedExits() const; 443 444 /// getUniqueExitBlocks - Return all unique successor blocks of this loop. 445 /// These are the blocks _outside of the current loop_ which are branched to. 446 /// This assumes that loop exits are in canonical form. 447 /// 448 void getUniqueExitBlocks(SmallVectorImpl<BasicBlock *> &ExitBlocks) const; 449 450 /// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one 451 /// block, return that block. Otherwise return null. 452 BasicBlock *getUniqueExitBlock() const; 453 454 void dump() const; 455 456 /// \brief Return the debug location of the start of this loop. 457 /// This looks for a BB terminating instruction with a known debug 458 /// location by looking at the preheader and header blocks. If it 459 /// cannot find a terminating instruction with location information, 460 /// it returns an unknown location. 461 DebugLoc getStartLoc() const { 462 DebugLoc StartLoc; 463 BasicBlock *HeadBB; 464 465 // Try the pre-header first. 466 if ((HeadBB = getLoopPreheader()) != nullptr) { 467 StartLoc = HeadBB->getTerminator()->getDebugLoc(); 468 if (!StartLoc.isUnknown()) 469 return StartLoc; 470 } 471 472 // If we have no pre-header or there are no instructions with debug 473 // info in it, try the header. 474 HeadBB = getHeader(); 475 if (HeadBB) 476 StartLoc = HeadBB->getTerminator()->getDebugLoc(); 477 478 return StartLoc; 479 } 480 481 private: 482 friend class LoopInfoBase<BasicBlock, Loop>; 483 explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {} 484 }; 485 486 //===----------------------------------------------------------------------===// 487 /// LoopInfo - This class builds and contains all of the top level loop 488 /// structures in the specified function. 489 /// 490 491 template<class BlockT, class LoopT> 492 class LoopInfoBase { 493 // BBMap - Mapping of basic blocks to the inner most loop they occur in 494 DenseMap<BlockT *, LoopT *> BBMap; 495 std::vector<LoopT *> TopLevelLoops; 496 friend class LoopBase<BlockT, LoopT>; 497 friend class LoopInfo; 498 499 void operator=(const LoopInfoBase &) LLVM_DELETED_FUNCTION; 500 LoopInfoBase(const LoopInfo &) LLVM_DELETED_FUNCTION; 501 public: 502 LoopInfoBase() { } 503 ~LoopInfoBase() { releaseMemory(); } 504 505 void releaseMemory() { 506 for (typename std::vector<LoopT *>::iterator I = 507 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I) 508 delete *I; // Delete all of the loops... 509 510 BBMap.clear(); // Reset internal state of analysis 511 TopLevelLoops.clear(); 512 } 513 514 /// iterator/begin/end - The interface to the top-level loops in the current 515 /// function. 516 /// 517 typedef typename std::vector<LoopT *>::const_iterator iterator; 518 typedef typename std::vector<LoopT *>::const_reverse_iterator 519 reverse_iterator; 520 iterator begin() const { return TopLevelLoops.begin(); } 521 iterator end() const { return TopLevelLoops.end(); } 522 reverse_iterator rbegin() const { return TopLevelLoops.rbegin(); } 523 reverse_iterator rend() const { return TopLevelLoops.rend(); } 524 bool empty() const { return TopLevelLoops.empty(); } 525 526 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 527 /// block is in no loop (for example the entry node), null is returned. 528 /// 529 LoopT *getLoopFor(const BlockT *BB) const { 530 return BBMap.lookup(const_cast<BlockT*>(BB)); 531 } 532 533 /// operator[] - same as getLoopFor... 534 /// 535 const LoopT *operator[](const BlockT *BB) const { 536 return getLoopFor(BB); 537 } 538 539 /// getLoopDepth - Return the loop nesting level of the specified block. A 540 /// depth of 0 means the block is not inside any loop. 541 /// 542 unsigned getLoopDepth(const BlockT *BB) const { 543 const LoopT *L = getLoopFor(BB); 544 return L ? L->getLoopDepth() : 0; 545 } 546 547 // isLoopHeader - True if the block is a loop header node 548 bool isLoopHeader(BlockT *BB) const { 549 const LoopT *L = getLoopFor(BB); 550 return L && L->getHeader() == BB; 551 } 552 553 /// removeLoop - This removes the specified top-level loop from this loop info 554 /// object. The loop is not deleted, as it will presumably be inserted into 555 /// another loop. 556 LoopT *removeLoop(iterator I) { 557 assert(I != end() && "Cannot remove end iterator!"); 558 LoopT *L = *I; 559 assert(!L->getParentLoop() && "Not a top-level loop!"); 560 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin())); 561 return L; 562 } 563 564 /// changeLoopFor - Change the top-level loop that contains BB to the 565 /// specified loop. This should be used by transformations that restructure 566 /// the loop hierarchy tree. 567 void changeLoopFor(BlockT *BB, LoopT *L) { 568 if (!L) { 569 BBMap.erase(BB); 570 return; 571 } 572 BBMap[BB] = L; 573 } 574 575 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 576 /// list with the indicated loop. 577 void changeTopLevelLoop(LoopT *OldLoop, 578 LoopT *NewLoop) { 579 typename std::vector<LoopT *>::iterator I = 580 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop); 581 assert(I != TopLevelLoops.end() && "Old loop not at top level!"); 582 *I = NewLoop; 583 assert(!NewLoop->ParentLoop && !OldLoop->ParentLoop && 584 "Loops already embedded into a subloop!"); 585 } 586 587 /// addTopLevelLoop - This adds the specified loop to the collection of 588 /// top-level loops. 589 void addTopLevelLoop(LoopT *New) { 590 assert(!New->getParentLoop() && "Loop already in subloop!"); 591 TopLevelLoops.push_back(New); 592 } 593 594 /// removeBlock - This method completely removes BB from all data structures, 595 /// including all of the Loop objects it is nested in and our mapping from 596 /// BasicBlocks to loops. 597 void removeBlock(BlockT *BB) { 598 typename DenseMap<BlockT *, LoopT *>::iterator I = BBMap.find(BB); 599 if (I != BBMap.end()) { 600 for (LoopT *L = I->second; L; L = L->getParentLoop()) 601 L->removeBlockFromLoop(BB); 602 603 BBMap.erase(I); 604 } 605 } 606 607 // Internals 608 609 static bool isNotAlreadyContainedIn(const LoopT *SubLoop, 610 const LoopT *ParentLoop) { 611 if (!SubLoop) return true; 612 if (SubLoop == ParentLoop) return false; 613 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop); 614 } 615 616 /// Create the loop forest using a stable algorithm. 617 void Analyze(DominatorTreeBase<BlockT> &DomTree); 618 619 // Debugging 620 621 void print(raw_ostream &OS) const; 622 }; 623 624 // Implementation in LoopInfoImpl.h 625 #ifdef __GNUC__ 626 __extension__ extern template class LoopInfoBase<BasicBlock, Loop>; 627 #endif 628 629 class LoopInfo : public FunctionPass { 630 LoopInfoBase<BasicBlock, Loop> LI; 631 friend class LoopBase<BasicBlock, Loop>; 632 633 void operator=(const LoopInfo &) LLVM_DELETED_FUNCTION; 634 LoopInfo(const LoopInfo &) LLVM_DELETED_FUNCTION; 635 public: 636 static char ID; // Pass identification, replacement for typeid 637 638 LoopInfo() : FunctionPass(ID) { 639 initializeLoopInfoPass(*PassRegistry::getPassRegistry()); 640 } 641 642 LoopInfoBase<BasicBlock, Loop>& getBase() { return LI; } 643 644 /// iterator/begin/end - The interface to the top-level loops in the current 645 /// function. 646 /// 647 typedef LoopInfoBase<BasicBlock, Loop>::iterator iterator; 648 typedef LoopInfoBase<BasicBlock, Loop>::reverse_iterator reverse_iterator; 649 inline iterator begin() const { return LI.begin(); } 650 inline iterator end() const { return LI.end(); } 651 inline reverse_iterator rbegin() const { return LI.rbegin(); } 652 inline reverse_iterator rend() const { return LI.rend(); } 653 bool empty() const { return LI.empty(); } 654 655 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 656 /// block is in no loop (for example the entry node), null is returned. 657 /// 658 inline Loop *getLoopFor(const BasicBlock *BB) const { 659 return LI.getLoopFor(BB); 660 } 661 662 /// operator[] - same as getLoopFor... 663 /// 664 inline const Loop *operator[](const BasicBlock *BB) const { 665 return LI.getLoopFor(BB); 666 } 667 668 /// getLoopDepth - Return the loop nesting level of the specified block. A 669 /// depth of 0 means the block is not inside any loop. 670 /// 671 inline unsigned getLoopDepth(const BasicBlock *BB) const { 672 return LI.getLoopDepth(BB); 673 } 674 675 // isLoopHeader - True if the block is a loop header node 676 inline bool isLoopHeader(BasicBlock *BB) const { 677 return LI.isLoopHeader(BB); 678 } 679 680 /// runOnFunction - Calculate the natural loop information. 681 /// 682 bool runOnFunction(Function &F) override; 683 684 void verifyAnalysis() const override; 685 686 void releaseMemory() override { LI.releaseMemory(); } 687 688 void print(raw_ostream &O, const Module* M = nullptr) const override; 689 690 void getAnalysisUsage(AnalysisUsage &AU) const override; 691 692 /// removeLoop - This removes the specified top-level loop from this loop info 693 /// object. The loop is not deleted, as it will presumably be inserted into 694 /// another loop. 695 inline Loop *removeLoop(iterator I) { return LI.removeLoop(I); } 696 697 /// changeLoopFor - Change the top-level loop that contains BB to the 698 /// specified loop. This should be used by transformations that restructure 699 /// the loop hierarchy tree. 700 inline void changeLoopFor(BasicBlock *BB, Loop *L) { 701 LI.changeLoopFor(BB, L); 702 } 703 704 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 705 /// list with the indicated loop. 706 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) { 707 LI.changeTopLevelLoop(OldLoop, NewLoop); 708 } 709 710 /// addTopLevelLoop - This adds the specified loop to the collection of 711 /// top-level loops. 712 inline void addTopLevelLoop(Loop *New) { 713 LI.addTopLevelLoop(New); 714 } 715 716 /// removeBlock - This method completely removes BB from all data structures, 717 /// including all of the Loop objects it is nested in and our mapping from 718 /// BasicBlocks to loops. 719 void removeBlock(BasicBlock *BB) { 720 LI.removeBlock(BB); 721 } 722 723 /// updateUnloop - Update LoopInfo after removing the last backedge from a 724 /// loop--now the "unloop". This updates the loop forest and parent loops for 725 /// each block so that Unloop is no longer referenced, but the caller must 726 /// actually delete the Unloop object. 727 void updateUnloop(Loop *Unloop); 728 729 /// replacementPreservesLCSSAForm - Returns true if replacing From with To 730 /// everywhere is guaranteed to preserve LCSSA form. 731 bool replacementPreservesLCSSAForm(Instruction *From, Value *To) { 732 // Preserving LCSSA form is only problematic if the replacing value is an 733 // instruction. 734 Instruction *I = dyn_cast<Instruction>(To); 735 if (!I) return true; 736 // If both instructions are defined in the same basic block then replacement 737 // cannot break LCSSA form. 738 if (I->getParent() == From->getParent()) 739 return true; 740 // If the instruction is not defined in a loop then it can safely replace 741 // anything. 742 Loop *ToLoop = getLoopFor(I->getParent()); 743 if (!ToLoop) return true; 744 // If the replacing instruction is defined in the same loop as the original 745 // instruction, or in a loop that contains it as an inner loop, then using 746 // it as a replacement will not break LCSSA form. 747 return ToLoop->contains(getLoopFor(From->getParent())); 748 } 749 }; 750 751 752 // Allow clients to walk the list of nested loops... 753 template <> struct GraphTraits<const Loop*> { 754 typedef const Loop NodeType; 755 typedef LoopInfo::iterator ChildIteratorType; 756 757 static NodeType *getEntryNode(const Loop *L) { return L; } 758 static inline ChildIteratorType child_begin(NodeType *N) { 759 return N->begin(); 760 } 761 static inline ChildIteratorType child_end(NodeType *N) { 762 return N->end(); 763 } 764 }; 765 766 template <> struct GraphTraits<Loop*> { 767 typedef Loop NodeType; 768 typedef LoopInfo::iterator ChildIteratorType; 769 770 static NodeType *getEntryNode(Loop *L) { return L; } 771 static inline ChildIteratorType child_begin(NodeType *N) { 772 return N->begin(); 773 } 774 static inline ChildIteratorType child_end(NodeType *N) { 775 return N->end(); 776 } 777 }; 778 779 } // End llvm namespace 780 781 #endif 782