LoopInfo.h revision 7ed47a13356daed2a34cd2209a31f92552e3bdd8
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. Note that natural 12// loops may actually be several loops that share the same header node. 13// 14// This analysis calculates the nesting structure of loops in a function. For 15// each natural loop identified, this analysis identifies natural loops 16// contained entirely within the loop and the basic blocks the make up the loop. 17// 18// It can calculate on the fly various bits of information, for example: 19// 20// * whether there is a preheader for the loop 21// * the number of back edges to the header 22// * whether or not a particular block branches out of the loop 23// * the successor blocks of the loop 24// * the loop depth 25// * the trip count 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/Constants.h" 35#include "llvm/Instructions.h" 36#include "llvm/ADT/DepthFirstIterator.h" 37#include "llvm/ADT/GraphTraits.h" 38#include "llvm/ADT/SmallPtrSet.h" 39#include "llvm/ADT/SmallVector.h" 40#include "llvm/Analysis/Dominators.h" 41#include "llvm/Support/CFG.h" 42#include "llvm/Support/Streams.h" 43#include <algorithm> 44#include <ostream> 45 46template<typename T> 47static void RemoveFromVector(std::vector<T*> &V, T *N) { 48 typename std::vector<T*>::iterator I = std::find(V.begin(), V.end(), N); 49 assert(I != V.end() && "N is not in this list!"); 50 V.erase(I); 51} 52 53namespace llvm { 54 55class DominatorTree; 56class LoopInfo; 57class PHINode; 58class Instruction; 59template<class N> class LoopInfoBase; 60 61//===----------------------------------------------------------------------===// 62/// LoopBase class - Instances of this class are used to represent loops that are 63/// detected in the flow graph 64/// 65template<class BlockT> 66class LoopBase { 67 LoopBase<BlockT> *ParentLoop; 68 std::vector<LoopBase<BlockT>*> SubLoops; // Loops contained entirely within this one 69 std::vector<BlockT*> Blocks; // First entry is the header node 70 71 LoopBase(const LoopBase<BlockT> &); // DO NOT IMPLEMENT 72 const LoopBase<BlockT> &operator=(const LoopBase<BlockT> &); // DO NOT IMPLEMENT 73public: 74 /// Loop ctor - This creates an empty loop. 75 LoopBase() : ParentLoop(0) {} 76 ~LoopBase() { 77 for (unsigned i = 0, e = SubLoops.size(); i != e; ++i) 78 delete SubLoops[i]; 79 } 80 81 unsigned getLoopDepth() const { 82 unsigned D = 0; 83 for (const LoopBase<BlockT> *CurLoop = this; CurLoop; 84 CurLoop = CurLoop->ParentLoop) 85 ++D; 86 return D; 87 } 88 BlockT *getHeader() const { return Blocks.front(); } 89 LoopBase<BlockT> *getParentLoop() const { return ParentLoop; } 90 91 /// contains - Return true of the specified basic block is in this loop 92 /// 93 bool contains(const BlockT *BB) const { 94 return std::find(Blocks.begin(), Blocks.end(), BB) != Blocks.end(); 95 } 96 97 /// iterator/begin/end - Return the loops contained entirely within this loop. 98 /// 99 const std::vector<LoopBase<BlockT>*> &getSubLoops() const { return SubLoops; } 100 typedef typename std::vector<LoopBase<BlockT>*>::const_iterator iterator; 101 iterator begin() const { return SubLoops.begin(); } 102 iterator end() const { return SubLoops.end(); } 103 bool empty() const { return SubLoops.empty(); } 104 105 /// getBlocks - Get a list of the basic blocks which make up this loop. 106 /// 107 const std::vector<BlockT*> &getBlocks() const { return Blocks; } 108 typedef typename std::vector<BlockT*>::const_iterator block_iterator; 109 block_iterator block_begin() const { return Blocks.begin(); } 110 block_iterator block_end() const { return Blocks.end(); } 111 112 /// isLoopExit - True if terminator in the block can branch to another block 113 /// that is outside of the current loop. 114 /// 115 bool isLoopExit(const BlockT *BB) const { 116 typedef GraphTraits<BlockT*> BlockTraits; 117 for (typename BlockTraits::ChildIteratorType SI = 118 BlockTraits::child_begin(const_cast<BlockT*>(BB)), 119 SE = BlockTraits::child_end(const_cast<BlockT*>(BB)); SI != SE; ++SI) { 120 if (!contains(*SI)) 121 return true; 122 } 123 return false; 124 } 125 126 /// getNumBackEdges - Calculate the number of back edges to the loop header 127 /// 128 unsigned getNumBackEdges() const { 129 unsigned NumBackEdges = 0; 130 BlockT *H = getHeader(); 131 132 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 133 for (typename InvBlockTraits::ChildIteratorType I = 134 InvBlockTraits::child_begin(const_cast<BlockT*>(H)), 135 E = InvBlockTraits::child_end(const_cast<BlockT*>(H)); I != E; ++I) 136 if (contains(*I)) 137 ++NumBackEdges; 138 139 return NumBackEdges; 140 } 141 142 /// isLoopInvariant - Return true if the specified value is loop invariant 143 /// 144 inline bool isLoopInvariant(Value *V) const { 145 if (Instruction *I = dyn_cast<Instruction>(V)) 146 return !contains(I->getParent()); 147 return true; // All non-instructions are loop invariant 148 } 149 150 //===--------------------------------------------------------------------===// 151 // APIs for simple analysis of the loop. 152 // 153 // Note that all of these methods can fail on general loops (ie, there may not 154 // be a preheader, etc). For best success, the loop simplification and 155 // induction variable canonicalization pass should be used to normalize loops 156 // for easy analysis. These methods assume canonical loops. 157 158 /// getExitingBlocks - Return all blocks inside the loop that have successors 159 /// outside of the loop. These are the blocks _inside of the current loop_ 160 /// which branch out. The returned list is always unique. 161 /// 162 void getExitingBlocks(SmallVectorImpl<BlockT *> &ExitingBlocks) const { 163 // Sort the blocks vector so that we can use binary search to do quick 164 // lookups. 165 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 166 std::sort(LoopBBs.begin(), LoopBBs.end()); 167 168 typedef GraphTraits<BlockT*> BlockTraits; 169 for (typename std::vector<BlockT*>::const_iterator BI = Blocks.begin(), 170 BE = Blocks.end(); BI != BE; ++BI) 171 for (typename BlockTraits::ChildIteratorType I = 172 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 173 I != E; ++I) 174 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) { 175 // Not in current loop? It must be an exit block. 176 ExitingBlocks.push_back(*BI); 177 break; 178 } 179 } 180 181 /// getExitBlocks - Return all of the successor blocks of this loop. These 182 /// are the blocks _outside of the current loop_ which are branched to. 183 /// 184 void getExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const { 185 // Sort the blocks vector so that we can use binary search to do quick 186 // lookups. 187 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 188 std::sort(LoopBBs.begin(), LoopBBs.end()); 189 190 typedef GraphTraits<BlockT*> BlockTraits; 191 for (typename std::vector<BlockT*>::const_iterator BI = Blocks.begin(), 192 BE = Blocks.end(); BI != BE; ++BI) 193 for (typename BlockTraits::ChildIteratorType I = 194 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 195 I != E; ++I) 196 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) 197 // Not in current loop? It must be an exit block. 198 ExitBlocks.push_back(*I); 199 } 200 201 /// getUniqueExitBlocks - Return all unique successor blocks of this loop. 202 /// These are the blocks _outside of the current loop_ which are branched to. 203 /// This assumes that loop is in canonical form. 204 /// 205 void getUniqueExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const { 206 // Sort the blocks vector so that we can use binary search to do quick 207 // lookups. 208 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 209 std::sort(LoopBBs.begin(), LoopBBs.end()); 210 211 std::vector<BlockT*> switchExitBlocks; 212 213 for (typename std::vector<BlockT*>::const_iterator BI = Blocks.begin(), 214 BE = Blocks.end(); BI != BE; ++BI) { 215 216 BlockT *current = *BI; 217 switchExitBlocks.clear(); 218 219 typedef GraphTraits<BlockT*> BlockTraits; 220 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 221 for (typename BlockTraits::ChildIteratorType I = 222 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 223 I != E; ++I) { 224 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) 225 // If block is inside the loop then it is not a exit block. 226 continue; 227 228 typename InvBlockTraits::ChildIteratorType PI = 229 InvBlockTraits::child_begin(*I); 230 BlockT *firstPred = *PI; 231 232 // If current basic block is this exit block's first predecessor 233 // then only insert exit block in to the output ExitBlocks vector. 234 // This ensures that same exit block is not inserted twice into 235 // ExitBlocks vector. 236 if (current != firstPred) 237 continue; 238 239 // If a terminator has more then two successors, for example SwitchInst, 240 // then it is possible that there are multiple edges from current block 241 // to one exit block. 242 if (std::distance(BlockTraits::child_begin(current), 243 BlockTraits::child_end(current)) <= 2) { 244 ExitBlocks.push_back(*I); 245 continue; 246 } 247 248 // In case of multiple edges from current block to exit block, collect 249 // only one edge in ExitBlocks. Use switchExitBlocks to keep track of 250 // duplicate edges. 251 if (std::find(switchExitBlocks.begin(), switchExitBlocks.end(), *I) 252 == switchExitBlocks.end()) { 253 switchExitBlocks.push_back(*I); 254 ExitBlocks.push_back(*I); 255 } 256 } 257 } 258 } 259 260 /// getLoopPreheader - If there is a preheader for this loop, return it. A 261 /// loop has a preheader if there is only one edge to the header of the loop 262 /// from outside of the loop. If this is the case, the block branching to the 263 /// header of the loop is the preheader node. 264 /// 265 /// This method returns null if there is no preheader for the loop. 266 /// 267 BlockT *getLoopPreheader() const { 268 // Keep track of nodes outside the loop branching to the header... 269 BlockT *Out = 0; 270 271 // Loop over the predecessors of the header node... 272 BlockT *Header = getHeader(); 273 typedef GraphTraits<BlockT*> BlockTraits; 274 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 275 for (typename InvBlockTraits::ChildIteratorType PI = 276 InvBlockTraits::child_begin(Header), 277 PE = InvBlockTraits::child_end(Header); PI != PE; ++PI) 278 if (!contains(*PI)) { // If the block is not in the loop... 279 if (Out && Out != *PI) 280 return 0; // Multiple predecessors outside the loop 281 Out = *PI; 282 } 283 284 // Make sure there is only one exit out of the preheader. 285 assert(Out && "Header of loop has no predecessors from outside loop?"); 286 typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out); 287 ++SI; 288 if (SI != BlockTraits::child_end(Out)) 289 return 0; // Multiple exits from the block, must not be a preheader. 290 291 // If there is exactly one preheader, return it. If there was zero, then Out 292 // is still null. 293 return Out; 294 } 295 296 /// getLoopLatch - If there is a latch block for this loop, return it. A 297 /// latch block is the canonical backedge for a loop. A loop header in normal 298 /// form has two edges into it: one from a preheader and one from a latch 299 /// block. 300 BlockT *getLoopLatch() const { 301 BlockT *Header = getHeader(); 302 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 303 typename InvBlockTraits::ChildIteratorType PI = 304 InvBlockTraits::child_begin(Header); 305 typename InvBlockTraits::ChildIteratorType PE = 306 InvBlockTraits::child_end(Header); 307 if (PI == PE) return 0; // no preds? 308 309 BlockT *Latch = 0; 310 if (contains(*PI)) 311 Latch = *PI; 312 ++PI; 313 if (PI == PE) return 0; // only one pred? 314 315 if (contains(*PI)) { 316 if (Latch) return 0; // multiple backedges 317 Latch = *PI; 318 } 319 ++PI; 320 if (PI != PE) return 0; // more than two preds 321 322 return Latch; 323 } 324 325 /// getCanonicalInductionVariable - Check to see if the loop has a canonical 326 /// induction variable: an integer recurrence that starts at 0 and increments 327 /// by one each time through the loop. If so, return the phi node that 328 /// corresponds to it. 329 /// 330 inline PHINode *getCanonicalInductionVariable() const { 331 BlockT *H = getHeader(); 332 333 BlockT *Incoming = 0, *Backedge = 0; 334 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 335 typename InvBlockTraits::ChildIteratorType PI = 336 InvBlockTraits::child_begin(H); 337 assert(PI != InvBlockTraits::child_end(H) && 338 "Loop must have at least one backedge!"); 339 Backedge = *PI++; 340 if (PI == InvBlockTraits::child_end(H)) return 0; // dead loop 341 Incoming = *PI++; 342 if (PI != InvBlockTraits::child_end(H)) return 0; // multiple backedges? 343 344 if (contains(Incoming)) { 345 if (contains(Backedge)) 346 return 0; 347 std::swap(Incoming, Backedge); 348 } else if (!contains(Backedge)) 349 return 0; 350 351 // Loop over all of the PHI nodes, looking for a canonical indvar. 352 for (typename BlockT::iterator I = H->begin(); isa<PHINode>(I); ++I) { 353 PHINode *PN = cast<PHINode>(I); 354 if (Instruction *Inc = 355 dyn_cast<Instruction>(PN->getIncomingValueForBlock(Backedge))) 356 if (Inc->getOpcode() == Instruction::Add && Inc->getOperand(0) == PN) 357 if (ConstantInt *CI = dyn_cast<ConstantInt>(Inc->getOperand(1))) 358 if (CI->equalsInt(1)) 359 return PN; 360 } 361 return 0; 362 } 363 364 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds 365 /// the canonical induction variable value for the "next" iteration of the 366 /// loop. This always succeeds if getCanonicalInductionVariable succeeds. 367 /// 368 inline Instruction *getCanonicalInductionVariableIncrement() const { 369 if (PHINode *PN = getCanonicalInductionVariable()) { 370 bool P1InLoop = contains(PN->getIncomingBlock(1)); 371 return cast<Instruction>(PN->getIncomingValue(P1InLoop)); 372 } 373 return 0; 374 } 375 376 /// getTripCount - Return a loop-invariant LLVM value indicating the number of 377 /// times the loop will be executed. Note that this means that the backedge 378 /// of the loop executes N-1 times. If the trip-count cannot be determined, 379 /// this returns null. 380 /// 381 inline Value *getTripCount() const { 382 // Canonical loops will end with a 'cmp ne I, V', where I is the incremented 383 // canonical induction variable and V is the trip count of the loop. 384 Instruction *Inc = getCanonicalInductionVariableIncrement(); 385 if (Inc == 0) return 0; 386 PHINode *IV = cast<PHINode>(Inc->getOperand(0)); 387 388 BlockT *BackedgeBlock = 389 IV->getIncomingBlock(contains(IV->getIncomingBlock(1))); 390 391 if (BranchInst *BI = dyn_cast<BranchInst>(BackedgeBlock->getTerminator())) 392 if (BI->isConditional()) { 393 if (ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition())) { 394 if (ICI->getOperand(0) == Inc) 395 if (BI->getSuccessor(0) == getHeader()) { 396 if (ICI->getPredicate() == ICmpInst::ICMP_NE) 397 return ICI->getOperand(1); 398 } else if (ICI->getPredicate() == ICmpInst::ICMP_EQ) { 399 return ICI->getOperand(1); 400 } 401 } 402 } 403 404 return 0; 405 } 406 407 /// isLCSSAForm - Return true if the Loop is in LCSSA form 408 inline bool isLCSSAForm() const { 409 // Sort the blocks vector so that we can use binary search to do quick 410 // lookups. 411 SmallPtrSet<BlockT*, 16> LoopBBs(block_begin(), block_end()); 412 413 for (block_iterator BI = block_begin(), E = block_end(); BI != E; ++BI) { 414 BlockT *BB = *BI; 415 for (typename BlockT::iterator I = BB->begin(), E = BB->end(); I != E; ++I) 416 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E; 417 ++UI) { 418 BlockT *UserBB = cast<Instruction>(*UI)->getParent(); 419 if (PHINode *P = dyn_cast<PHINode>(*UI)) { 420 unsigned OperandNo = UI.getOperandNo(); 421 UserBB = P->getIncomingBlock(OperandNo/2); 422 } 423 424 // Check the current block, as a fast-path. Most values are used in the 425 // same block they are defined in. 426 if (UserBB != BB && !LoopBBs.count(UserBB)) 427 return false; 428 } 429 } 430 431 return true; 432 } 433 434 //===--------------------------------------------------------------------===// 435 // APIs for updating loop information after changing the CFG 436 // 437 438 /// addBasicBlockToLoop - This method is used by other analyses to update loop 439 /// information. NewBB is set to be a new member of the current loop. 440 /// Because of this, it is added as a member of all parent loops, and is added 441 /// to the specified LoopInfo object as being in the current basic block. It 442 /// is not valid to replace the loop header with this method. 443 /// 444 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT> &LI); 445 446 /// replaceChildLoopWith - This is used when splitting loops up. It replaces 447 /// the OldChild entry in our children list with NewChild, and updates the 448 /// parent pointer of OldChild to be null and the NewChild to be this loop. 449 /// This updates the loop depth of the new child. 450 void replaceChildLoopWith(LoopBase<BlockT> *OldChild, 451 LoopBase<BlockT> *NewChild) { 452 assert(OldChild->ParentLoop == this && "This loop is already broken!"); 453 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 454 typename std::vector<LoopBase<BlockT>*>::iterator I = 455 std::find(SubLoops.begin(), SubLoops.end(), OldChild); 456 assert(I != SubLoops.end() && "OldChild not in loop!"); 457 *I = NewChild; 458 OldChild->ParentLoop = 0; 459 NewChild->ParentLoop = this; 460 } 461 462 /// addChildLoop - Add the specified loop to be a child of this loop. This 463 /// updates the loop depth of the new child. 464 /// 465 void addChildLoop(LoopBase<BlockT> *NewChild) { 466 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 467 NewChild->ParentLoop = this; 468 SubLoops.push_back(NewChild); 469 } 470 471 /// removeChildLoop - This removes the specified child from being a subloop of 472 /// this loop. The loop is not deleted, as it will presumably be inserted 473 /// into another loop. 474 LoopBase<BlockT> *removeChildLoop(iterator I) { 475 assert(I != SubLoops.end() && "Cannot remove end iterator!"); 476 LoopBase<BlockT> *Child = *I; 477 assert(Child->ParentLoop == this && "Child is not a child of this loop!"); 478 SubLoops.erase(SubLoops.begin()+(I-begin())); 479 Child->ParentLoop = 0; 480 return Child; 481 } 482 483 /// addBlockEntry - This adds a basic block directly to the basic block list. 484 /// This should only be used by transformations that create new loops. Other 485 /// transformations should use addBasicBlockToLoop. 486 void addBlockEntry(BlockT *BB) { 487 Blocks.push_back(BB); 488 } 489 490 /// moveToHeader - This method is used to move BB (which must be part of this 491 /// loop) to be the loop header of the loop (the block that dominates all 492 /// others). 493 void moveToHeader(BlockT *BB) { 494 if (Blocks[0] == BB) return; 495 for (unsigned i = 0; ; ++i) { 496 assert(i != Blocks.size() && "Loop does not contain BB!"); 497 if (Blocks[i] == BB) { 498 Blocks[i] = Blocks[0]; 499 Blocks[0] = BB; 500 return; 501 } 502 } 503 } 504 505 /// removeBlockFromLoop - This removes the specified basic block from the 506 /// current loop, updating the Blocks as appropriate. This does not update 507 /// the mapping in the LoopInfo class. 508 void removeBlockFromLoop(BlockT *BB) { 509 RemoveFromVector(Blocks, BB); 510 } 511 512 /// verifyLoop - Verify loop structure 513 void verifyLoop() const { 514#ifndef NDEBUG 515 assert (getHeader() && "Loop header is missing"); 516 assert (getLoopPreheader() && "Loop preheader is missing"); 517 assert (getLoopLatch() && "Loop latch is missing"); 518 for (typename std::vector<LoopBase<BlockT>*>::const_iterator I = 519 SubLoops.begin(), E = SubLoops.end(); I != E; ++I) 520 (*I)->verifyLoop(); 521#endif 522 } 523 524 void print(std::ostream &OS, unsigned Depth = 0) const { 525 OS << std::string(Depth*2, ' ') << "Loop Containing: "; 526 527 for (unsigned i = 0; i < getBlocks().size(); ++i) { 528 if (i) OS << ","; 529 WriteAsOperand(OS, getBlocks()[i], false); 530 } 531 OS << "\n"; 532 533 for (iterator I = begin(), E = end(); I != E; ++I) 534 (*I)->print(OS, Depth+2); 535 } 536 537 void print(std::ostream *O, unsigned Depth = 0) const { 538 if (O) print(*O, Depth); 539 } 540 541 void dump() const { 542 print(cerr); 543 } 544 545private: 546 friend class LoopInfoBase<BlockT>; 547 LoopBase(BlockT *BB) : ParentLoop(0) { 548 Blocks.push_back(BB); 549 } 550}; 551 552typedef LoopBase<BasicBlock> Loop; 553 554 555//===----------------------------------------------------------------------===// 556/// LoopInfo - This class builds and contains all of the top level loop 557/// structures in the specified function. 558/// 559 560template<class BlockT> 561class LoopInfoBase { 562 // BBMap - Mapping of basic blocks to the inner most loop they occur in 563 std::map<BlockT*, LoopBase<BlockT>*> BBMap; 564 std::vector<LoopBase<BlockT>*> TopLevelLoops; 565 friend class LoopBase<BlockT>; 566 567public: 568 LoopInfoBase() { } 569 ~LoopInfoBase() { releaseMemory(); } 570 571 void releaseMemory() { 572 for (typename std::vector<LoopBase<BlockT>* >::iterator I = 573 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I) 574 delete *I; // Delete all of the loops... 575 576 BBMap.clear(); // Reset internal state of analysis 577 TopLevelLoops.clear(); 578 } 579 580 /// iterator/begin/end - The interface to the top-level loops in the current 581 /// function. 582 /// 583 typedef typename std::vector<LoopBase<BlockT>*>::const_iterator iterator; 584 iterator begin() const { return TopLevelLoops.begin(); } 585 iterator end() const { return TopLevelLoops.end(); } 586 587 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 588 /// block is in no loop (for example the entry node), null is returned. 589 /// 590 LoopBase<BlockT> *getLoopFor(const BlockT *BB) const { 591 typename std::map<BlockT *, LoopBase<BlockT>*>::const_iterator I= 592 BBMap.find(const_cast<BlockT*>(BB)); 593 return I != BBMap.end() ? I->second : 0; 594 } 595 596 /// operator[] - same as getLoopFor... 597 /// 598 const LoopBase<BlockT> *operator[](const BlockT *BB) const { 599 return getLoopFor(BB); 600 } 601 602 /// getLoopDepth - Return the loop nesting level of the specified block... 603 /// 604 unsigned getLoopDepth(const BlockT *BB) const { 605 const LoopBase<BlockT> *L = getLoopFor(BB); 606 return L ? L->getLoopDepth() : 0; 607 } 608 609 // isLoopHeader - True if the block is a loop header node 610 bool isLoopHeader(BlockT *BB) const { 611 const LoopBase<BlockT> *L = getLoopFor(BB); 612 return L && L->getHeader() == BB; 613 } 614 615 /// removeLoop - This removes the specified top-level loop from this loop info 616 /// object. The loop is not deleted, as it will presumably be inserted into 617 /// another loop. 618 LoopBase<BlockT> *removeLoop(iterator I) { 619 assert(I != end() && "Cannot remove end iterator!"); 620 LoopBase<BlockT> *L = *I; 621 assert(L->getParentLoop() == 0 && "Not a top-level loop!"); 622 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin())); 623 return L; 624 } 625 626 /// changeLoopFor - Change the top-level loop that contains BB to the 627 /// specified loop. This should be used by transformations that restructure 628 /// the loop hierarchy tree. 629 void changeLoopFor(BlockT *BB, LoopBase<BlockT> *L) { 630 LoopBase<BlockT> *&OldLoop = BBMap[BB]; 631 assert(OldLoop && "Block not in a loop yet!"); 632 OldLoop = L; 633 } 634 635 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 636 /// list with the indicated loop. 637 void changeTopLevelLoop(LoopBase<BlockT> *OldLoop, 638 LoopBase<BlockT> *NewLoop) { 639 typename std::vector<LoopBase<BlockT>*>::iterator I = 640 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop); 641 assert(I != TopLevelLoops.end() && "Old loop not at top level!"); 642 *I = NewLoop; 643 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 && 644 "Loops already embedded into a subloop!"); 645 } 646 647 /// addTopLevelLoop - This adds the specified loop to the collection of 648 /// top-level loops. 649 void addTopLevelLoop(LoopBase<BlockT> *New) { 650 assert(New->getParentLoop() == 0 && "Loop already in subloop!"); 651 TopLevelLoops.push_back(New); 652 } 653 654 /// removeBlock - This method completely removes BB from all data structures, 655 /// including all of the Loop objects it is nested in and our mapping from 656 /// BasicBlocks to loops. 657 void removeBlock(BlockT *BB) { 658 typename std::map<BlockT *, LoopBase<BlockT>*>::iterator I = BBMap.find(BB); 659 if (I != BBMap.end()) { 660 for (LoopBase<BlockT> *L = I->second; L; L = L->getParentLoop()) 661 L->removeBlockFromLoop(BB); 662 663 BBMap.erase(I); 664 } 665 } 666 667 // Internals 668 669 static bool isNotAlreadyContainedIn(LoopBase<BlockT> *SubLoop, 670 LoopBase<BlockT> *ParentLoop) { 671 if (SubLoop == 0) return true; 672 if (SubLoop == ParentLoop) return false; 673 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop); 674 } 675 676 void Calculate(DominatorTreeBase<BlockT> &DT) { 677 BlockT *RootNode = DT.getRootNode()->getBlock(); 678 679 for (df_iterator<BlockT*> NI = df_begin(RootNode), 680 NE = df_end(RootNode); NI != NE; ++NI) 681 if (LoopBase<BlockT> *L = ConsiderForLoop(*NI, DT)) 682 TopLevelLoops.push_back(L); 683 } 684 685 LoopBase<BlockT> *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) { 686 if (BBMap.find(BB) != BBMap.end()) return 0;// Haven't processed this node? 687 688 std::vector<BlockT *> TodoStack; 689 690 // Scan the predecessors of BB, checking to see if BB dominates any of 691 // them. This identifies backedges which target this node... 692 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 693 for (typename InvBlockTraits::ChildIteratorType I = 694 InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB); 695 I != E; ++I) 696 if (DT.dominates(BB, *I)) // If BB dominates it's predecessor... 697 TodoStack.push_back(*I); 698 699 if (TodoStack.empty()) return 0; // No backedges to this block... 700 701 // Create a new loop to represent this basic block... 702 LoopBase<BlockT> *L = new LoopBase<BlockT>(BB); 703 BBMap[BB] = L; 704 705 BlockT *EntryBlock = BB->getParent()->begin(); 706 707 while (!TodoStack.empty()) { // Process all the nodes in the loop 708 BlockT *X = TodoStack.back(); 709 TodoStack.pop_back(); 710 711 if (!L->contains(X) && // As of yet unprocessed?? 712 DT.dominates(EntryBlock, X)) { // X is reachable from entry block? 713 // Check to see if this block already belongs to a loop. If this occurs 714 // then we have a case where a loop that is supposed to be a child of the 715 // current loop was processed before the current loop. When this occurs, 716 // this child loop gets added to a part of the current loop, making it a 717 // sibling to the current loop. We have to reparent this loop. 718 if (LoopBase<BlockT> *SubLoop = 719 const_cast<LoopBase<BlockT>*>(getLoopFor(X))) 720 if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)) { 721 // Remove the subloop from it's current parent... 722 assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L); 723 LoopBase<BlockT> *SLP = SubLoop->ParentLoop; // SubLoopParent 724 typename std::vector<LoopBase<BlockT>*>::iterator I = 725 std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop); 726 assert(I != SLP->SubLoops.end() && "SubLoop not a child of parent?"); 727 SLP->SubLoops.erase(I); // Remove from parent... 728 729 // Add the subloop to THIS loop... 730 SubLoop->ParentLoop = L; 731 L->SubLoops.push_back(SubLoop); 732 } 733 734 // Normal case, add the block to our loop... 735 L->Blocks.push_back(X); 736 737 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 738 739 // Add all of the predecessors of X to the end of the work stack... 740 TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X), 741 InvBlockTraits::child_end(X)); 742 } 743 } 744 745 // If there are any loops nested within this loop, create them now! 746 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 747 E = L->Blocks.end(); I != E; ++I) 748 if (LoopBase<BlockT> *NewLoop = ConsiderForLoop(*I, DT)) { 749 L->SubLoops.push_back(NewLoop); 750 NewLoop->ParentLoop = L; 751 } 752 753 // Add the basic blocks that comprise this loop to the BBMap so that this 754 // loop can be found for them. 755 // 756 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 757 E = L->Blocks.end(); I != E; ++I) { 758 typename std::map<BlockT*, LoopBase<BlockT>*>::iterator BBMI = 759 BBMap.lower_bound(*I); 760 if (BBMI == BBMap.end() || BBMI->first != *I) // Not in map yet... 761 BBMap.insert(BBMI, std::make_pair(*I, L)); // Must be at this level 762 } 763 764 // Now that we have a list of all of the child loops of this loop, check to 765 // see if any of them should actually be nested inside of each other. We can 766 // accidentally pull loops our of their parents, so we must make sure to 767 // organize the loop nests correctly now. 768 { 769 std::map<BlockT*, LoopBase<BlockT>*> ContainingLoops; 770 for (unsigned i = 0; i != L->SubLoops.size(); ++i) { 771 LoopBase<BlockT> *Child = L->SubLoops[i]; 772 assert(Child->getParentLoop() == L && "Not proper child loop?"); 773 774 if (LoopBase<BlockT> *ContainingLoop = 775 ContainingLoops[Child->getHeader()]) { 776 // If there is already a loop which contains this loop, move this loop 777 // into the containing loop. 778 MoveSiblingLoopInto(Child, ContainingLoop); 779 --i; // The loop got removed from the SubLoops list. 780 } else { 781 // This is currently considered to be a top-level loop. Check to see if 782 // any of the contained blocks are loop headers for subloops we have 783 // already processed. 784 for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) { 785 LoopBase<BlockT> *&BlockLoop = ContainingLoops[Child->Blocks[b]]; 786 if (BlockLoop == 0) { // Child block not processed yet... 787 BlockLoop = Child; 788 } else if (BlockLoop != Child) { 789 LoopBase<BlockT> *SubLoop = BlockLoop; 790 // Reparent all of the blocks which used to belong to BlockLoops 791 for (unsigned j = 0, e = SubLoop->Blocks.size(); j != e; ++j) 792 ContainingLoops[SubLoop->Blocks[j]] = Child; 793 794 // There is already a loop which contains this block, that means 795 // that we should reparent the loop which the block is currently 796 // considered to belong to to be a child of this loop. 797 MoveSiblingLoopInto(SubLoop, Child); 798 --i; // We just shrunk the SubLoops list. 799 } 800 } 801 } 802 } 803 } 804 805 return L; 806 } 807 808 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside of 809 /// the NewParent Loop, instead of being a sibling of it. 810 void MoveSiblingLoopInto(LoopBase<BlockT> *NewChild, 811 LoopBase<BlockT> *NewParent) { 812 LoopBase<BlockT> *OldParent = NewChild->getParentLoop(); 813 assert(OldParent && OldParent == NewParent->getParentLoop() && 814 NewChild != NewParent && "Not sibling loops!"); 815 816 // Remove NewChild from being a child of OldParent 817 typename std::vector<LoopBase<BlockT>*>::iterator I = 818 std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(), NewChild); 819 assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??"); 820 OldParent->SubLoops.erase(I); // Remove from parent's subloops list 821 NewChild->ParentLoop = 0; 822 823 InsertLoopInto(NewChild, NewParent); 824 } 825 826 /// InsertLoopInto - This inserts loop L into the specified parent loop. If the 827 /// parent loop contains a loop which should contain L, the loop gets inserted 828 /// into L instead. 829 void InsertLoopInto(LoopBase<BlockT> *L, LoopBase<BlockT> *Parent) { 830 BlockT *LHeader = L->getHeader(); 831 assert(Parent->contains(LHeader) && "This loop should not be inserted here!"); 832 833 // Check to see if it belongs in a child loop... 834 for (unsigned i = 0, e = Parent->SubLoops.size(); i != e; ++i) 835 if (Parent->SubLoops[i]->contains(LHeader)) { 836 InsertLoopInto(L, Parent->SubLoops[i]); 837 return; 838 } 839 840 // If not, insert it here! 841 Parent->SubLoops.push_back(L); 842 L->ParentLoop = Parent; 843 } 844 845 // Debugging 846 847 void print(std::ostream &OS, const Module* ) const { 848 for (unsigned i = 0; i < TopLevelLoops.size(); ++i) 849 TopLevelLoops[i]->print(OS); 850 #if 0 851 for (std::map<BasicBlock*, Loop*>::const_iterator I = BBMap.begin(), 852 E = BBMap.end(); I != E; ++I) 853 OS << "BB '" << I->first->getName() << "' level = " 854 << I->second->getLoopDepth() << "\n"; 855 #endif 856 } 857}; 858 859class LoopInfo : public FunctionPass { 860 LoopInfoBase<BasicBlock>* LI; 861 friend class LoopBase<BasicBlock>; 862 863public: 864 static char ID; // Pass identification, replacement for typeid 865 866 LoopInfo() : FunctionPass(intptr_t(&ID)) { 867 LI = new LoopInfoBase<BasicBlock>(); 868 } 869 870 ~LoopInfo() { delete LI; } 871 872 LoopInfoBase<BasicBlock>& getBase() { return *LI; } 873 874 /// iterator/begin/end - The interface to the top-level loops in the current 875 /// function. 876 /// 877 typedef std::vector<Loop*>::const_iterator iterator; 878 inline iterator begin() const { return LI->begin(); } 879 inline iterator end() const { return LI->end(); } 880 881 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 882 /// block is in no loop (for example the entry node), null is returned. 883 /// 884 inline Loop *getLoopFor(const BasicBlock *BB) const { 885 return LI->getLoopFor(BB); 886 } 887 888 /// operator[] - same as getLoopFor... 889 /// 890 inline const Loop *operator[](const BasicBlock *BB) const { 891 return LI->getLoopFor(BB); 892 } 893 894 /// getLoopDepth - Return the loop nesting level of the specified block... 895 /// 896 inline unsigned getLoopDepth(const BasicBlock *BB) const { 897 return LI->getLoopDepth(BB); 898 } 899 900 // isLoopHeader - True if the block is a loop header node 901 inline bool isLoopHeader(BasicBlock *BB) const { 902 return LI->isLoopHeader(BB); 903 } 904 905 /// runOnFunction - Calculate the natural loop information. 906 /// 907 virtual bool runOnFunction(Function &F); 908 909 virtual void releaseMemory() { LI->releaseMemory(); } 910 911 virtual void print(std::ostream &O, const Module* M = 0) const { 912 if (O) LI->print(O, M); 913 } 914 915 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 916 917 /// removeLoop - This removes the specified top-level loop from this loop info 918 /// object. The loop is not deleted, as it will presumably be inserted into 919 /// another loop. 920 inline Loop *removeLoop(iterator I) { return LI->removeLoop(I); } 921 922 /// changeLoopFor - Change the top-level loop that contains BB to the 923 /// specified loop. This should be used by transformations that restructure 924 /// the loop hierarchy tree. 925 inline void changeLoopFor(BasicBlock *BB, Loop *L) { 926 LI->changeLoopFor(BB, L); 927 } 928 929 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 930 /// list with the indicated loop. 931 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) { 932 LI->changeTopLevelLoop(OldLoop, NewLoop); 933 } 934 935 /// addTopLevelLoop - This adds the specified loop to the collection of 936 /// top-level loops. 937 inline void addTopLevelLoop(Loop *New) { 938 LI->addTopLevelLoop(New); 939 } 940 941 /// removeBlock - This method completely removes BB from all data structures, 942 /// including all of the Loop objects it is nested in and our mapping from 943 /// BasicBlocks to loops. 944 void removeBlock(BasicBlock *BB) { 945 LI->removeBlock(BB); 946 } 947}; 948 949 950// Allow clients to walk the list of nested loops... 951template <> struct GraphTraits<const Loop*> { 952 typedef const Loop NodeType; 953 typedef std::vector<Loop*>::const_iterator ChildIteratorType; 954 955 static NodeType *getEntryNode(const Loop *L) { return L; } 956 static inline ChildIteratorType child_begin(NodeType *N) { 957 return N->begin(); 958 } 959 static inline ChildIteratorType child_end(NodeType *N) { 960 return N->end(); 961 } 962}; 963 964template <> struct GraphTraits<Loop*> { 965 typedef Loop NodeType; 966 typedef std::vector<Loop*>::const_iterator ChildIteratorType; 967 968 static NodeType *getEntryNode(Loop *L) { return L; } 969 static inline ChildIteratorType child_begin(NodeType *N) { 970 return N->begin(); 971 } 972 static inline ChildIteratorType child_end(NodeType *N) { 973 return N->end(); 974 } 975}; 976 977template<class BlockT> 978void LoopBase<BlockT>::addBasicBlockToLoop(BlockT *NewBB, 979 LoopInfoBase<BlockT> &LIB) { 980 assert((Blocks.empty() || LIB[getHeader()] == this) && 981 "Incorrect LI specified for this loop!"); 982 assert(NewBB && "Cannot add a null basic block to the loop!"); 983 assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!"); 984 985 // Add the loop mapping to the LoopInfo object... 986 LIB.BBMap[NewBB] = this; 987 988 // Add the basic block to this loop and all parent loops... 989 LoopBase<BlockT> *L = this; 990 while (L) { 991 L->Blocks.push_back(NewBB); 992 L = L->getParentLoop(); 993 } 994} 995 996} // End llvm namespace 997 998// Make sure that any clients of this file link in LoopInfo.cpp 999FORCE_DEFINING_FILE_TO_BE_LINKED(LoopInfo) 1000 1001#endif 1002