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 // FIXME: Replace this brittle forward declaration with the include of the new 46 // PassManager.h when doing so doesn't break the PassManagerBuilder. 47 template <typename IRUnitT> class AnalysisManager; 48 class PreservedAnalyses; 49 50 template<typename T> 51 inline void RemoveFromVector(std::vector<T*> &V, T *N) { 52 typename std::vector<T*>::iterator I = std::find(V.begin(), V.end(), N); 53 assert(I != V.end() && "N is not in this list!"); 54 V.erase(I); 55 } 56 57 class DominatorTree; 58 class LoopInfo; 59 class Loop; 60 class MDNode; 61 class PHINode; 62 class raw_ostream; 63 template<class N> class DominatorTreeBase; 64 template<class N, class M> class LoopInfoBase; 65 template<class N, class M> class LoopBase; 66 67 //===----------------------------------------------------------------------===// 68 /// LoopBase class - Instances of this class are used to represent loops that 69 /// are detected in the flow graph 70 /// 71 template<class BlockT, class LoopT> 72 class LoopBase { 73 LoopT *ParentLoop; 74 // SubLoops - Loops contained entirely within this one. 75 std::vector<LoopT *> SubLoops; 76 77 // Blocks - The list of blocks in this loop. First entry is the header node. 78 std::vector<BlockT*> Blocks; 79 80 SmallPtrSet<const BlockT*, 8> DenseBlockSet; 81 82 LoopBase(const LoopBase<BlockT, LoopT> &) = delete; 83 const LoopBase<BlockT, LoopT>& 84 operator=(const LoopBase<BlockT, LoopT> &) = delete; 85 public: 86 /// Loop ctor - This creates an empty loop. 87 LoopBase() : ParentLoop(nullptr) {} 88 ~LoopBase() { 89 for (size_t i = 0, e = SubLoops.size(); i != e; ++i) 90 delete SubLoops[i]; 91 } 92 93 /// getLoopDepth - Return the nesting level of this loop. An outer-most 94 /// loop has depth 1, for consistency with loop depth values used for basic 95 /// blocks, where depth 0 is used for blocks not inside any loops. 96 unsigned getLoopDepth() const { 97 unsigned D = 1; 98 for (const LoopT *CurLoop = ParentLoop; CurLoop; 99 CurLoop = CurLoop->ParentLoop) 100 ++D; 101 return D; 102 } 103 BlockT *getHeader() const { return Blocks.front(); } 104 LoopT *getParentLoop() const { return ParentLoop; } 105 106 /// setParentLoop is a raw interface for bypassing addChildLoop. 107 void setParentLoop(LoopT *L) { ParentLoop = L; } 108 109 /// contains - Return true if the specified loop is contained within in 110 /// this loop. 111 /// 112 bool contains(const LoopT *L) const { 113 if (L == this) return true; 114 if (!L) return false; 115 return contains(L->getParentLoop()); 116 } 117 118 /// contains - Return true if the specified basic block is in this loop. 119 /// 120 bool contains(const BlockT *BB) const { 121 return DenseBlockSet.count(BB); 122 } 123 124 /// contains - Return true if the specified instruction is in this loop. 125 /// 126 template<class InstT> 127 bool contains(const InstT *Inst) const { 128 return contains(Inst->getParent()); 129 } 130 131 /// iterator/begin/end - Return the loops contained entirely within this loop. 132 /// 133 const std::vector<LoopT *> &getSubLoops() const { return SubLoops; } 134 std::vector<LoopT *> &getSubLoopsVector() { return SubLoops; } 135 typedef typename std::vector<LoopT *>::const_iterator iterator; 136 typedef typename std::vector<LoopT *>::const_reverse_iterator 137 reverse_iterator; 138 iterator begin() const { return SubLoops.begin(); } 139 iterator end() const { return SubLoops.end(); } 140 reverse_iterator rbegin() const { return SubLoops.rbegin(); } 141 reverse_iterator rend() const { return SubLoops.rend(); } 142 bool empty() const { return SubLoops.empty(); } 143 144 /// getBlocks - Get a list of the basic blocks which make up this loop. 145 /// 146 const std::vector<BlockT*> &getBlocks() const { return Blocks; } 147 typedef typename std::vector<BlockT*>::const_iterator block_iterator; 148 block_iterator block_begin() const { return Blocks.begin(); } 149 block_iterator block_end() const { return Blocks.end(); } 150 151 /// getNumBlocks - Get the number of blocks in this loop in constant time. 152 unsigned getNumBlocks() const { 153 return Blocks.size(); 154 } 155 156 /// isLoopExiting - True if terminator in the block can branch to another 157 /// block that is outside of the current loop. 158 /// 159 bool isLoopExiting(const BlockT *BB) const { 160 typedef GraphTraits<const BlockT*> BlockTraits; 161 for (typename BlockTraits::ChildIteratorType SI = 162 BlockTraits::child_begin(BB), 163 SE = BlockTraits::child_end(BB); SI != SE; ++SI) { 164 if (!contains(*SI)) 165 return true; 166 } 167 return false; 168 } 169 170 /// getNumBackEdges - Calculate the number of back edges to the loop header 171 /// 172 unsigned getNumBackEdges() const { 173 unsigned NumBackEdges = 0; 174 BlockT *H = getHeader(); 175 176 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 177 for (typename InvBlockTraits::ChildIteratorType I = 178 InvBlockTraits::child_begin(H), 179 E = InvBlockTraits::child_end(H); I != E; ++I) 180 if (contains(*I)) 181 ++NumBackEdges; 182 183 return NumBackEdges; 184 } 185 186 //===--------------------------------------------------------------------===// 187 // APIs for simple analysis of the loop. 188 // 189 // Note that all of these methods can fail on general loops (ie, there may not 190 // be a preheader, etc). For best success, the loop simplification and 191 // induction variable canonicalization pass should be used to normalize loops 192 // for easy analysis. These methods assume canonical loops. 193 194 /// getExitingBlocks - Return all blocks inside the loop that have successors 195 /// outside of the loop. These are the blocks _inside of the current loop_ 196 /// which branch out. The returned list is always unique. 197 /// 198 void getExitingBlocks(SmallVectorImpl<BlockT *> &ExitingBlocks) const; 199 200 /// getExitingBlock - If getExitingBlocks would return exactly one block, 201 /// return that block. Otherwise return null. 202 BlockT *getExitingBlock() const; 203 204 /// getExitBlocks - Return all of the successor blocks of this loop. These 205 /// are the blocks _outside of the current loop_ which are branched to. 206 /// 207 void getExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const; 208 209 /// getExitBlock - If getExitBlocks would return exactly one block, 210 /// return that block. Otherwise return null. 211 BlockT *getExitBlock() const; 212 213 /// Edge type. 214 typedef std::pair<const BlockT*, const BlockT*> Edge; 215 216 /// getExitEdges - Return all pairs of (_inside_block_,_outside_block_). 217 void getExitEdges(SmallVectorImpl<Edge> &ExitEdges) const; 218 219 /// getLoopPreheader - If there is a preheader for this loop, return it. A 220 /// loop has a preheader if there is only one edge to the header of the loop 221 /// from outside of the loop. If this is the case, the block branching to the 222 /// header of the loop is the preheader node. 223 /// 224 /// This method returns null if there is no preheader for the loop. 225 /// 226 BlockT *getLoopPreheader() const; 227 228 /// getLoopPredecessor - If the given loop's header has exactly one unique 229 /// predecessor outside the loop, return it. Otherwise return null. 230 /// This is less strict that the loop "preheader" concept, which requires 231 /// the predecessor to have exactly one successor. 232 /// 233 BlockT *getLoopPredecessor() const; 234 235 /// getLoopLatch - If there is a single latch block for this loop, return it. 236 /// A latch block is a block that contains a branch back to the header. 237 BlockT *getLoopLatch() const; 238 239 /// getLoopLatches - Return all loop latch blocks of this loop. A latch block 240 /// is a block that contains a branch back to the header. 241 void getLoopLatches(SmallVectorImpl<BlockT *> &LoopLatches) const { 242 BlockT *H = getHeader(); 243 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 244 for (typename InvBlockTraits::ChildIteratorType I = 245 InvBlockTraits::child_begin(H), 246 E = InvBlockTraits::child_end(H); I != E; ++I) 247 if (contains(*I)) 248 LoopLatches.push_back(*I); 249 } 250 251 //===--------------------------------------------------------------------===// 252 // APIs for updating loop information after changing the CFG 253 // 254 255 /// addBasicBlockToLoop - This method is used by other analyses to update loop 256 /// information. NewBB is set to be a new member of the current loop. 257 /// Because of this, it is added as a member of all parent loops, and is added 258 /// to the specified LoopInfo object as being in the current basic block. It 259 /// is not valid to replace the loop header with this method. 260 /// 261 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LI); 262 263 /// replaceChildLoopWith - This is used when splitting loops up. It replaces 264 /// the OldChild entry in our children list with NewChild, and updates the 265 /// parent pointer of OldChild to be null and the NewChild to be this loop. 266 /// This updates the loop depth of the new child. 267 void replaceChildLoopWith(LoopT *OldChild, LoopT *NewChild); 268 269 /// addChildLoop - Add the specified loop to be a child of this loop. This 270 /// updates the loop depth of the new child. 271 /// 272 void addChildLoop(LoopT *NewChild) { 273 assert(!NewChild->ParentLoop && "NewChild already has a parent!"); 274 NewChild->ParentLoop = static_cast<LoopT *>(this); 275 SubLoops.push_back(NewChild); 276 } 277 278 /// removeChildLoop - This removes the specified child from being a subloop of 279 /// this loop. The loop is not deleted, as it will presumably be inserted 280 /// into another loop. 281 LoopT *removeChildLoop(iterator I) { 282 assert(I != SubLoops.end() && "Cannot remove end iterator!"); 283 LoopT *Child = *I; 284 assert(Child->ParentLoop == this && "Child is not a child of this loop!"); 285 SubLoops.erase(SubLoops.begin()+(I-begin())); 286 Child->ParentLoop = nullptr; 287 return Child; 288 } 289 290 /// addBlockEntry - This adds a basic block directly to the basic block list. 291 /// This should only be used by transformations that create new loops. Other 292 /// transformations should use addBasicBlockToLoop. 293 void addBlockEntry(BlockT *BB) { 294 Blocks.push_back(BB); 295 DenseBlockSet.insert(BB); 296 } 297 298 /// reverseBlocks - interface to reverse Blocks[from, end of loop] in this loop 299 void reverseBlock(unsigned from) { 300 std::reverse(Blocks.begin() + from, Blocks.end()); 301 } 302 303 /// reserveBlocks- interface to do reserve() for Blocks 304 void reserveBlocks(unsigned size) { 305 Blocks.reserve(size); 306 } 307 308 /// moveToHeader - This method is used to move BB (which must be part of this 309 /// loop) to be the loop header of the loop (the block that dominates all 310 /// others). 311 void moveToHeader(BlockT *BB) { 312 if (Blocks[0] == BB) return; 313 for (unsigned i = 0; ; ++i) { 314 assert(i != Blocks.size() && "Loop does not contain BB!"); 315 if (Blocks[i] == BB) { 316 Blocks[i] = Blocks[0]; 317 Blocks[0] = BB; 318 return; 319 } 320 } 321 } 322 323 /// removeBlockFromLoop - This removes the specified basic block from the 324 /// current loop, updating the Blocks as appropriate. This does not update 325 /// the mapping in the LoopInfo class. 326 void removeBlockFromLoop(BlockT *BB) { 327 RemoveFromVector(Blocks, BB); 328 DenseBlockSet.erase(BB); 329 } 330 331 /// verifyLoop - Verify loop structure 332 void verifyLoop() const; 333 334 /// verifyLoop - Verify loop structure of this loop and all nested loops. 335 void verifyLoopNest(DenseSet<const LoopT*> *Loops) const; 336 337 void print(raw_ostream &OS, unsigned Depth = 0) const; 338 339 protected: 340 friend class LoopInfoBase<BlockT, LoopT>; 341 explicit LoopBase(BlockT *BB) : ParentLoop(nullptr) { 342 Blocks.push_back(BB); 343 DenseBlockSet.insert(BB); 344 } 345 }; 346 347 template<class BlockT, class LoopT> 348 raw_ostream& operator<<(raw_ostream &OS, const LoopBase<BlockT, LoopT> &Loop) { 349 Loop.print(OS); 350 return OS; 351 } 352 353 // Implementation in LoopInfoImpl.h 354 #ifdef __GNUC__ 355 __extension__ extern template class LoopBase<BasicBlock, Loop>; 356 #endif 357 358 class Loop : public LoopBase<BasicBlock, Loop> { 359 public: 360 Loop() {} 361 362 /// isLoopInvariant - Return true if the specified value is loop invariant 363 /// 364 bool isLoopInvariant(Value *V) const; 365 366 /// hasLoopInvariantOperands - Return true if all the operands of the 367 /// specified instruction are loop invariant. 368 bool hasLoopInvariantOperands(Instruction *I) const; 369 370 /// makeLoopInvariant - If the given value is an instruction inside of the 371 /// loop and it can be hoisted, do so to make it trivially loop-invariant. 372 /// Return true if the value after any hoisting is loop invariant. This 373 /// function can be used as a slightly more aggressive replacement for 374 /// isLoopInvariant. 375 /// 376 /// If InsertPt is specified, it is the point to hoist instructions to. 377 /// If null, the terminator of the loop preheader is used. 378 /// 379 bool makeLoopInvariant(Value *V, bool &Changed, 380 Instruction *InsertPt = nullptr) const; 381 382 /// makeLoopInvariant - If the given instruction is inside of the 383 /// loop and it can be hoisted, do so to make it trivially loop-invariant. 384 /// Return true if the instruction after any hoisting is loop invariant. This 385 /// function can be used as a slightly more aggressive replacement for 386 /// isLoopInvariant. 387 /// 388 /// If InsertPt is specified, it is the point to hoist instructions to. 389 /// If null, the terminator of the loop preheader is used. 390 /// 391 bool makeLoopInvariant(Instruction *I, bool &Changed, 392 Instruction *InsertPt = nullptr) const; 393 394 /// getCanonicalInductionVariable - Check to see if the loop has a canonical 395 /// induction variable: an integer recurrence that starts at 0 and increments 396 /// by one each time through the loop. If so, return the phi node that 397 /// corresponds to it. 398 /// 399 /// The IndVarSimplify pass transforms loops to have a canonical induction 400 /// variable. 401 /// 402 PHINode *getCanonicalInductionVariable() const; 403 404 /// isLCSSAForm - Return true if the Loop is in LCSSA form 405 bool isLCSSAForm(DominatorTree &DT) const; 406 407 /// isLoopSimplifyForm - Return true if the Loop is in the form that 408 /// the LoopSimplify form transforms loops to, which is sometimes called 409 /// normal form. 410 bool isLoopSimplifyForm() const; 411 412 /// isSafeToClone - Return true if the loop body is safe to clone in practice. 413 bool isSafeToClone() const; 414 415 /// Returns true if the loop is annotated parallel. 416 /// 417 /// A parallel loop can be assumed to not contain any dependencies between 418 /// iterations by the compiler. That is, any loop-carried dependency checking 419 /// can be skipped completely when parallelizing the loop on the target 420 /// machine. Thus, if the parallel loop information originates from the 421 /// programmer, e.g. via the OpenMP parallel for pragma, it is the 422 /// programmer's responsibility to ensure there are no loop-carried 423 /// dependencies. The final execution order of the instructions across 424 /// iterations is not guaranteed, thus, the end result might or might not 425 /// implement actual concurrent execution of instructions across multiple 426 /// iterations. 427 bool isAnnotatedParallel() const; 428 429 /// Return the llvm.loop loop id metadata node for this loop if it is present. 430 /// 431 /// If this loop contains the same llvm.loop metadata on each branch to the 432 /// header then the node is returned. If any latch instruction does not 433 /// contain llvm.loop or or if multiple latches contain different nodes then 434 /// 0 is returned. 435 MDNode *getLoopID() const; 436 /// Set the llvm.loop loop id metadata for this loop. 437 /// 438 /// The LoopID metadata node will be added to each terminator instruction in 439 /// the loop that branches to the loop header. 440 /// 441 /// The LoopID metadata node should have one or more operands and the first 442 /// operand should should be the node itself. 443 void setLoopID(MDNode *LoopID) const; 444 445 /// hasDedicatedExits - Return true if no exit block for the loop 446 /// has a predecessor that is outside the loop. 447 bool hasDedicatedExits() const; 448 449 /// getUniqueExitBlocks - Return all unique successor blocks of this loop. 450 /// These are the blocks _outside of the current loop_ which are branched to. 451 /// This assumes that loop exits are in canonical form. 452 /// 453 void getUniqueExitBlocks(SmallVectorImpl<BasicBlock *> &ExitBlocks) const; 454 455 /// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one 456 /// block, return that block. Otherwise return null. 457 BasicBlock *getUniqueExitBlock() const; 458 459 void dump() const; 460 461 /// \brief Return the debug location of the start of this loop. 462 /// This looks for a BB terminating instruction with a known debug 463 /// location by looking at the preheader and header blocks. If it 464 /// cannot find a terminating instruction with location information, 465 /// it returns an unknown location. 466 DebugLoc getStartLoc() const { 467 BasicBlock *HeadBB; 468 469 // Try the pre-header first. 470 if ((HeadBB = getLoopPreheader()) != nullptr) 471 if (DebugLoc DL = HeadBB->getTerminator()->getDebugLoc()) 472 return DL; 473 474 // If we have no pre-header or there are no instructions with debug 475 // info in it, try the header. 476 HeadBB = getHeader(); 477 if (HeadBB) 478 return HeadBB->getTerminator()->getDebugLoc(); 479 480 return DebugLoc(); 481 } 482 483 private: 484 friend class LoopInfoBase<BasicBlock, Loop>; 485 explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {} 486 }; 487 488 //===----------------------------------------------------------------------===// 489 /// LoopInfo - This class builds and contains all of the top level loop 490 /// structures in the specified function. 491 /// 492 493 template<class BlockT, class LoopT> 494 class LoopInfoBase { 495 // BBMap - Mapping of basic blocks to the inner most loop they occur in 496 DenseMap<BlockT *, LoopT *> BBMap; 497 std::vector<LoopT *> TopLevelLoops; 498 friend class LoopBase<BlockT, LoopT>; 499 friend class LoopInfo; 500 501 void operator=(const LoopInfoBase &) = delete; 502 LoopInfoBase(const LoopInfoBase &) = delete; 503 public: 504 LoopInfoBase() { } 505 ~LoopInfoBase() { releaseMemory(); } 506 507 LoopInfoBase(LoopInfoBase &&Arg) 508 : BBMap(std::move(Arg.BBMap)), 509 TopLevelLoops(std::move(Arg.TopLevelLoops)) { 510 // We have to clear the arguments top level loops as we've taken ownership. 511 Arg.TopLevelLoops.clear(); 512 } 513 LoopInfoBase &operator=(LoopInfoBase &&RHS) { 514 BBMap = std::move(RHS.BBMap); 515 516 for (auto *L : TopLevelLoops) 517 delete L; 518 TopLevelLoops = std::move(RHS.TopLevelLoops); 519 RHS.TopLevelLoops.clear(); 520 return *this; 521 } 522 523 void releaseMemory() { 524 BBMap.clear(); 525 526 for (auto *L : TopLevelLoops) 527 delete L; 528 TopLevelLoops.clear(); 529 } 530 531 /// iterator/begin/end - The interface to the top-level loops in the current 532 /// function. 533 /// 534 typedef typename std::vector<LoopT *>::const_iterator iterator; 535 typedef typename std::vector<LoopT *>::const_reverse_iterator 536 reverse_iterator; 537 iterator begin() const { return TopLevelLoops.begin(); } 538 iterator end() const { return TopLevelLoops.end(); } 539 reverse_iterator rbegin() const { return TopLevelLoops.rbegin(); } 540 reverse_iterator rend() const { return TopLevelLoops.rend(); } 541 bool empty() const { return TopLevelLoops.empty(); } 542 543 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 544 /// block is in no loop (for example the entry node), null is returned. 545 /// 546 LoopT *getLoopFor(const BlockT *BB) const { 547 return BBMap.lookup(const_cast<BlockT*>(BB)); 548 } 549 550 /// operator[] - same as getLoopFor... 551 /// 552 const LoopT *operator[](const BlockT *BB) const { 553 return getLoopFor(BB); 554 } 555 556 /// getLoopDepth - Return the loop nesting level of the specified block. A 557 /// depth of 0 means the block is not inside any loop. 558 /// 559 unsigned getLoopDepth(const BlockT *BB) const { 560 const LoopT *L = getLoopFor(BB); 561 return L ? L->getLoopDepth() : 0; 562 } 563 564 // isLoopHeader - True if the block is a loop header node 565 bool isLoopHeader(BlockT *BB) const { 566 const LoopT *L = getLoopFor(BB); 567 return L && L->getHeader() == BB; 568 } 569 570 /// removeLoop - This removes the specified top-level loop from this loop info 571 /// object. The loop is not deleted, as it will presumably be inserted into 572 /// another loop. 573 LoopT *removeLoop(iterator I) { 574 assert(I != end() && "Cannot remove end iterator!"); 575 LoopT *L = *I; 576 assert(!L->getParentLoop() && "Not a top-level loop!"); 577 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin())); 578 return L; 579 } 580 581 /// changeLoopFor - Change the top-level loop that contains BB to the 582 /// specified loop. This should be used by transformations that restructure 583 /// the loop hierarchy tree. 584 void changeLoopFor(BlockT *BB, LoopT *L) { 585 if (!L) { 586 BBMap.erase(BB); 587 return; 588 } 589 BBMap[BB] = L; 590 } 591 592 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 593 /// list with the indicated loop. 594 void changeTopLevelLoop(LoopT *OldLoop, 595 LoopT *NewLoop) { 596 auto I = std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop); 597 assert(I != TopLevelLoops.end() && "Old loop not at top level!"); 598 *I = NewLoop; 599 assert(!NewLoop->ParentLoop && !OldLoop->ParentLoop && 600 "Loops already embedded into a subloop!"); 601 } 602 603 /// addTopLevelLoop - This adds the specified loop to the collection of 604 /// top-level loops. 605 void addTopLevelLoop(LoopT *New) { 606 assert(!New->getParentLoop() && "Loop already in subloop!"); 607 TopLevelLoops.push_back(New); 608 } 609 610 /// removeBlock - This method completely removes BB from all data structures, 611 /// including all of the Loop objects it is nested in and our mapping from 612 /// BasicBlocks to loops. 613 void removeBlock(BlockT *BB) { 614 auto I = BBMap.find(BB); 615 if (I != BBMap.end()) { 616 for (LoopT *L = I->second; L; L = L->getParentLoop()) 617 L->removeBlockFromLoop(BB); 618 619 BBMap.erase(I); 620 } 621 } 622 623 // Internals 624 625 static bool isNotAlreadyContainedIn(const LoopT *SubLoop, 626 const LoopT *ParentLoop) { 627 if (!SubLoop) return true; 628 if (SubLoop == ParentLoop) return false; 629 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop); 630 } 631 632 /// Create the loop forest using a stable algorithm. 633 void Analyze(DominatorTreeBase<BlockT> &DomTree); 634 635 // Debugging 636 void print(raw_ostream &OS) const; 637 638 void verify() const; 639 }; 640 641 // Implementation in LoopInfoImpl.h 642 #ifdef __GNUC__ 643 __extension__ extern template class LoopInfoBase<BasicBlock, Loop>; 644 #endif 645 646 class LoopInfo : public LoopInfoBase<BasicBlock, Loop> { 647 typedef LoopInfoBase<BasicBlock, Loop> BaseT; 648 649 friend class LoopBase<BasicBlock, Loop>; 650 651 void operator=(const LoopInfo &) = delete; 652 LoopInfo(const LoopInfo &) = delete; 653 public: 654 LoopInfo() {} 655 656 LoopInfo(LoopInfo &&Arg) : BaseT(std::move(static_cast<BaseT &>(Arg))) {} 657 LoopInfo &operator=(LoopInfo &&RHS) { 658 BaseT::operator=(std::move(static_cast<BaseT &>(RHS))); 659 return *this; 660 } 661 662 // Most of the public interface is provided via LoopInfoBase. 663 664 /// updateUnloop - Update LoopInfo after removing the last backedge from a 665 /// loop--now the "unloop". This updates the loop forest and parent loops for 666 /// each block so that Unloop is no longer referenced, but the caller must 667 /// actually delete the Unloop object. 668 void updateUnloop(Loop *Unloop); 669 670 /// replacementPreservesLCSSAForm - Returns true if replacing From with To 671 /// everywhere is guaranteed to preserve LCSSA form. 672 bool replacementPreservesLCSSAForm(Instruction *From, Value *To) { 673 // Preserving LCSSA form is only problematic if the replacing value is an 674 // instruction. 675 Instruction *I = dyn_cast<Instruction>(To); 676 if (!I) return true; 677 // If both instructions are defined in the same basic block then replacement 678 // cannot break LCSSA form. 679 if (I->getParent() == From->getParent()) 680 return true; 681 // If the instruction is not defined in a loop then it can safely replace 682 // anything. 683 Loop *ToLoop = getLoopFor(I->getParent()); 684 if (!ToLoop) return true; 685 // If the replacing instruction is defined in the same loop as the original 686 // instruction, or in a loop that contains it as an inner loop, then using 687 // it as a replacement will not break LCSSA form. 688 return ToLoop->contains(getLoopFor(From->getParent())); 689 } 690 }; 691 692 // Allow clients to walk the list of nested loops... 693 template <> struct GraphTraits<const Loop*> { 694 typedef const Loop NodeType; 695 typedef LoopInfo::iterator ChildIteratorType; 696 697 static NodeType *getEntryNode(const Loop *L) { return L; } 698 static inline ChildIteratorType child_begin(NodeType *N) { 699 return N->begin(); 700 } 701 static inline ChildIteratorType child_end(NodeType *N) { 702 return N->end(); 703 } 704 }; 705 706 template <> struct GraphTraits<Loop*> { 707 typedef Loop NodeType; 708 typedef LoopInfo::iterator ChildIteratorType; 709 710 static NodeType *getEntryNode(Loop *L) { return L; } 711 static inline ChildIteratorType child_begin(NodeType *N) { 712 return N->begin(); 713 } 714 static inline ChildIteratorType child_end(NodeType *N) { 715 return N->end(); 716 } 717 }; 718 719 /// \brief Analysis pass that exposes the \c LoopInfo for a function. 720 class LoopAnalysis { 721 static char PassID; 722 723 public: 724 typedef LoopInfo Result; 725 726 /// \brief Opaque, unique identifier for this analysis pass. 727 static void *ID() { return (void *)&PassID; } 728 729 /// \brief Provide a name for the analysis for debugging and logging. 730 static StringRef name() { return "LoopAnalysis"; } 731 732 LoopAnalysis() {} 733 LoopAnalysis(const LoopAnalysis &Arg) {} 734 LoopAnalysis(LoopAnalysis &&Arg) {} 735 LoopAnalysis &operator=(const LoopAnalysis &RHS) { return *this; } 736 LoopAnalysis &operator=(LoopAnalysis &&RHS) { return *this; } 737 738 LoopInfo run(Function &F, AnalysisManager<Function> *AM); 739 }; 740 741 /// \brief Printer pass for the \c LoopAnalysis results. 742 class LoopPrinterPass { 743 raw_ostream &OS; 744 745 public: 746 explicit LoopPrinterPass(raw_ostream &OS) : OS(OS) {} 747 PreservedAnalyses run(Function &F, AnalysisManager<Function> *AM); 748 749 static StringRef name() { return "LoopPrinterPass"; } 750 }; 751 752 /// \brief The legacy pass manager's analysis pass to compute loop information. 753 class LoopInfoWrapperPass : public FunctionPass { 754 LoopInfo LI; 755 756 public: 757 static char ID; // Pass identification, replacement for typeid 758 759 LoopInfoWrapperPass() : FunctionPass(ID) { 760 initializeLoopInfoWrapperPassPass(*PassRegistry::getPassRegistry()); 761 } 762 763 LoopInfo &getLoopInfo() { return LI; } 764 const LoopInfo &getLoopInfo() const { return LI; } 765 766 /// \brief Calculate the natural loop information for a given function. 767 bool runOnFunction(Function &F) override; 768 769 void verifyAnalysis() const override; 770 771 void releaseMemory() override { LI.releaseMemory(); } 772 773 void print(raw_ostream &O, const Module *M = nullptr) const override; 774 775 void getAnalysisUsage(AnalysisUsage &AU) const override; 776 }; 777 778 } // End llvm namespace 779 780 #endif 781