LoopInfo.h revision 1827e8263c9cb5dc29eea4999d8729f7376af4e1
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 46namespace llvm { 47 48template<typename T> 49static void RemoveFromVector(std::vector<T*> &V, T *N) { 50 typename std::vector<T*>::iterator I = std::find(V.begin(), V.end(), N); 51 assert(I != V.end() && "N is not in this list!"); 52 V.erase(I); 53} 54 55class DominatorTree; 56class LoopInfo; 57template<class N> class LoopInfoBase; 58template<class N> class LoopBase; 59 60typedef LoopBase<BasicBlock> Loop; 61 62//===----------------------------------------------------------------------===// 63/// LoopBase class - Instances of this class are used to represent loops that 64/// are detected in the flow graph 65/// 66template<class BlockT> 67class LoopBase { 68 LoopBase<BlockT> *ParentLoop; 69 // SubLoops - Loops contained entirely within this one. 70 std::vector<LoopBase<BlockT>*> SubLoops; 71 72 // Blocks - The list of blocks in this loop. First entry is the header node. 73 std::vector<BlockT*> Blocks; 74 75 LoopBase(const LoopBase<BlockT> &); // DO NOT IMPLEMENT 76 const LoopBase<BlockT>&operator=(const LoopBase<BlockT> &);// DO NOT IMPLEMENT 77public: 78 /// Loop ctor - This creates an empty loop. 79 LoopBase() : ParentLoop(0) {} 80 ~LoopBase() { 81 for (size_t i = 0, e = SubLoops.size(); i != e; ++i) 82 delete SubLoops[i]; 83 } 84 85 /// getLoopDepth - Return the nesting level of this loop. An outer-most 86 /// loop has depth 1, for consistency with loop depth values used for basic 87 /// blocks, where depth 0 is used for blocks not inside any loops. 88 unsigned getLoopDepth() const { 89 unsigned D = 1; 90 for (const LoopBase<BlockT> *CurLoop = ParentLoop; CurLoop; 91 CurLoop = CurLoop->ParentLoop) 92 ++D; 93 return D; 94 } 95 BlockT *getHeader() const { return Blocks.front(); } 96 LoopBase<BlockT> *getParentLoop() const { return ParentLoop; } 97 98 /// contains - Return true if the specified basic block is in this loop 99 /// 100 bool contains(const BlockT *BB) const { 101 return std::find(block_begin(), block_end(), BB) != block_end(); 102 } 103 104 /// iterator/begin/end - Return the loops contained entirely within this loop. 105 /// 106 const std::vector<LoopBase<BlockT>*> &getSubLoops() const { return SubLoops; } 107 typedef typename std::vector<LoopBase<BlockT>*>::const_iterator iterator; 108 iterator begin() const { return SubLoops.begin(); } 109 iterator end() const { return SubLoops.end(); } 110 bool empty() const { return SubLoops.empty(); } 111 112 /// getBlocks - Get a list of the basic blocks which make up this loop. 113 /// 114 const std::vector<BlockT*> &getBlocks() const { return Blocks; } 115 typedef typename std::vector<BlockT*>::const_iterator block_iterator; 116 block_iterator block_begin() const { return Blocks.begin(); } 117 block_iterator block_end() const { return Blocks.end(); } 118 119 /// isLoopExit - True if terminator in the block can branch to another block 120 /// that is outside of the current loop. 121 /// 122 bool isLoopExit(const BlockT *BB) const { 123 typedef GraphTraits<BlockT*> BlockTraits; 124 for (typename BlockTraits::ChildIteratorType SI = 125 BlockTraits::child_begin(const_cast<BlockT*>(BB)), 126 SE = BlockTraits::child_end(const_cast<BlockT*>(BB)); SI != SE; ++SI) { 127 if (!contains(*SI)) 128 return true; 129 } 130 return false; 131 } 132 133 /// getNumBackEdges - Calculate the number of back edges to the loop header 134 /// 135 unsigned getNumBackEdges() const { 136 unsigned NumBackEdges = 0; 137 BlockT *H = getHeader(); 138 139 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 140 for (typename InvBlockTraits::ChildIteratorType I = 141 InvBlockTraits::child_begin(const_cast<BlockT*>(H)), 142 E = InvBlockTraits::child_end(const_cast<BlockT*>(H)); I != E; ++I) 143 if (contains(*I)) 144 ++NumBackEdges; 145 146 return NumBackEdges; 147 } 148 149 /// isLoopInvariant - Return true if the specified value is loop invariant 150 /// 151 inline bool isLoopInvariant(Value *V) const { 152 if (Instruction *I = dyn_cast<Instruction>(V)) 153 return !contains(I->getParent()); 154 return true; // All non-instructions are loop invariant 155 } 156 157 //===--------------------------------------------------------------------===// 158 // APIs for simple analysis of the loop. 159 // 160 // Note that all of these methods can fail on general loops (ie, there may not 161 // be a preheader, etc). For best success, the loop simplification and 162 // induction variable canonicalization pass should be used to normalize loops 163 // for easy analysis. These methods assume canonical loops. 164 165 /// getExitingBlocks - Return all blocks inside the loop that have successors 166 /// outside of the loop. These are the blocks _inside of the current loop_ 167 /// which branch out. The returned list is always unique. 168 /// 169 void getExitingBlocks(SmallVectorImpl<BlockT *> &ExitingBlocks) const { 170 // Sort the blocks vector so that we can use binary search to do quick 171 // lookups. 172 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 173 std::sort(LoopBBs.begin(), LoopBBs.end()); 174 175 typedef GraphTraits<BlockT*> BlockTraits; 176 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) 177 for (typename BlockTraits::ChildIteratorType I = 178 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 179 I != E; ++I) 180 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) { 181 // Not in current loop? It must be an exit block. 182 ExitingBlocks.push_back(*BI); 183 break; 184 } 185 } 186 187 /// getExitingBlock - If getExitingBlocks would return exactly one block, 188 /// return that block. Otherwise return null. 189 BlockT *getExitingBlock() const { 190 SmallVector<BlockT*, 8> ExitingBlocks; 191 getExitingBlocks(ExitingBlocks); 192 if (ExitingBlocks.size() == 1) 193 return ExitingBlocks[0]; 194 return 0; 195 } 196 197 /// getExitBlocks - Return all of the successor blocks of this loop. These 198 /// are the blocks _outside of the current loop_ which are branched to. 199 /// 200 void getExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const { 201 // Sort the blocks vector so that we can use binary search to do quick 202 // lookups. 203 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 204 std::sort(LoopBBs.begin(), LoopBBs.end()); 205 206 typedef GraphTraits<BlockT*> BlockTraits; 207 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) 208 for (typename BlockTraits::ChildIteratorType I = 209 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 210 I != E; ++I) 211 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) 212 // Not in current loop? It must be an exit block. 213 ExitBlocks.push_back(*I); 214 } 215 216 /// getExitBlock - If getExitBlocks would return exactly one block, 217 /// return that block. Otherwise return null. 218 BlockT *getExitBlock() const { 219 SmallVector<BlockT*, 8> ExitBlocks; 220 getExitBlocks(ExitBlocks); 221 if (ExitBlocks.size() == 1) 222 return ExitBlocks[0]; 223 return 0; 224 } 225 226 /// getUniqueExitBlocks - Return all unique successor blocks of this loop. 227 /// These are the blocks _outside of the current loop_ which are branched to. 228 /// This assumes that loop is in canonical form. 229 /// 230 void getUniqueExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const { 231 // Sort the blocks vector so that we can use binary search to do quick 232 // lookups. 233 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 234 std::sort(LoopBBs.begin(), LoopBBs.end()); 235 236 std::vector<BlockT*> switchExitBlocks; 237 238 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) { 239 240 BlockT *current = *BI; 241 switchExitBlocks.clear(); 242 243 typedef GraphTraits<BlockT*> BlockTraits; 244 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 245 for (typename BlockTraits::ChildIteratorType I = 246 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 247 I != E; ++I) { 248 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) 249 // If block is inside the loop then it is not a exit block. 250 continue; 251 252 typename InvBlockTraits::ChildIteratorType PI = 253 InvBlockTraits::child_begin(*I); 254 BlockT *firstPred = *PI; 255 256 // If current basic block is this exit block's first predecessor 257 // then only insert exit block in to the output ExitBlocks vector. 258 // This ensures that same exit block is not inserted twice into 259 // ExitBlocks vector. 260 if (current != firstPred) 261 continue; 262 263 // If a terminator has more then two successors, for example SwitchInst, 264 // then it is possible that there are multiple edges from current block 265 // to one exit block. 266 if (std::distance(BlockTraits::child_begin(current), 267 BlockTraits::child_end(current)) <= 2) { 268 ExitBlocks.push_back(*I); 269 continue; 270 } 271 272 // In case of multiple edges from current block to exit block, collect 273 // only one edge in ExitBlocks. Use switchExitBlocks to keep track of 274 // duplicate edges. 275 if (std::find(switchExitBlocks.begin(), switchExitBlocks.end(), *I) 276 == switchExitBlocks.end()) { 277 switchExitBlocks.push_back(*I); 278 ExitBlocks.push_back(*I); 279 } 280 } 281 } 282 } 283 284 /// getLoopPreheader - If there is a preheader for this loop, return it. A 285 /// loop has a preheader if there is only one edge to the header of the loop 286 /// from outside of the loop. If this is the case, the block branching to the 287 /// header of the loop is the preheader node. 288 /// 289 /// This method returns null if there is no preheader for the loop. 290 /// 291 BlockT *getLoopPreheader() const { 292 // Keep track of nodes outside the loop branching to the header... 293 BlockT *Out = 0; 294 295 // Loop over the predecessors of the header node... 296 BlockT *Header = getHeader(); 297 typedef GraphTraits<BlockT*> BlockTraits; 298 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 299 for (typename InvBlockTraits::ChildIteratorType PI = 300 InvBlockTraits::child_begin(Header), 301 PE = InvBlockTraits::child_end(Header); PI != PE; ++PI) 302 if (!contains(*PI)) { // If the block is not in the loop... 303 if (Out && Out != *PI) 304 return 0; // Multiple predecessors outside the loop 305 Out = *PI; 306 } 307 308 // Make sure there is only one exit out of the preheader. 309 assert(Out && "Header of loop has no predecessors from outside loop?"); 310 typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out); 311 ++SI; 312 if (SI != BlockTraits::child_end(Out)) 313 return 0; // Multiple exits from the block, must not be a preheader. 314 315 // If there is exactly one preheader, return it. If there was zero, then 316 // Out is still null. 317 return Out; 318 } 319 320 /// getLoopLatch - If there is a single latch block for this loop, return it. 321 /// A latch block is a block that contains a branch back to the header. 322 /// A loop header in normal form has two edges into it: one from a preheader 323 /// and one from a latch block. 324 BlockT *getLoopLatch() const { 325 BlockT *Header = getHeader(); 326 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 327 typename InvBlockTraits::ChildIteratorType PI = 328 InvBlockTraits::child_begin(Header); 329 typename InvBlockTraits::ChildIteratorType PE = 330 InvBlockTraits::child_end(Header); 331 if (PI == PE) return 0; // no preds? 332 333 BlockT *Latch = 0; 334 if (contains(*PI)) 335 Latch = *PI; 336 ++PI; 337 if (PI == PE) return 0; // only one pred? 338 339 if (contains(*PI)) { 340 if (Latch) return 0; // multiple backedges 341 Latch = *PI; 342 } 343 ++PI; 344 if (PI != PE) return 0; // more than two preds 345 346 return Latch; 347 } 348 349 /// getCanonicalInductionVariable - Check to see if the loop has a canonical 350 /// induction variable: an integer recurrence that starts at 0 and increments 351 /// by one each time through the loop. If so, return the phi node that 352 /// corresponds to it. 353 /// 354 inline PHINode *getCanonicalInductionVariable() const { 355 BlockT *H = getHeader(); 356 357 BlockT *Incoming = 0, *Backedge = 0; 358 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 359 typename InvBlockTraits::ChildIteratorType PI = 360 InvBlockTraits::child_begin(H); 361 assert(PI != InvBlockTraits::child_end(H) && 362 "Loop must have at least one backedge!"); 363 Backedge = *PI++; 364 if (PI == InvBlockTraits::child_end(H)) return 0; // dead loop 365 Incoming = *PI++; 366 if (PI != InvBlockTraits::child_end(H)) return 0; // multiple backedges? 367 368 if (contains(Incoming)) { 369 if (contains(Backedge)) 370 return 0; 371 std::swap(Incoming, Backedge); 372 } else if (!contains(Backedge)) 373 return 0; 374 375 // Loop over all of the PHI nodes, looking for a canonical indvar. 376 for (typename BlockT::iterator I = H->begin(); isa<PHINode>(I); ++I) { 377 PHINode *PN = cast<PHINode>(I); 378 if (ConstantInt *CI = 379 dyn_cast<ConstantInt>(PN->getIncomingValueForBlock(Incoming))) 380 if (CI->isNullValue()) 381 if (Instruction *Inc = 382 dyn_cast<Instruction>(PN->getIncomingValueForBlock(Backedge))) 383 if (Inc->getOpcode() == Instruction::Add && 384 Inc->getOperand(0) == PN) 385 if (ConstantInt *CI = dyn_cast<ConstantInt>(Inc->getOperand(1))) 386 if (CI->equalsInt(1)) 387 return PN; 388 } 389 return 0; 390 } 391 392 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds 393 /// the canonical induction variable value for the "next" iteration of the 394 /// loop. This always succeeds if getCanonicalInductionVariable succeeds. 395 /// 396 inline Instruction *getCanonicalInductionVariableIncrement() const { 397 if (PHINode *PN = getCanonicalInductionVariable()) { 398 bool P1InLoop = contains(PN->getIncomingBlock(1)); 399 return cast<Instruction>(PN->getIncomingValue(P1InLoop)); 400 } 401 return 0; 402 } 403 404 /// getTripCount - Return a loop-invariant LLVM value indicating the number of 405 /// times the loop will be executed. Note that this means that the backedge 406 /// of the loop executes N-1 times. If the trip-count cannot be determined, 407 /// this returns null. 408 /// 409 inline Value *getTripCount() const { 410 // Canonical loops will end with a 'cmp ne I, V', where I is the incremented 411 // canonical induction variable and V is the trip count of the loop. 412 Instruction *Inc = getCanonicalInductionVariableIncrement(); 413 if (Inc == 0) return 0; 414 PHINode *IV = cast<PHINode>(Inc->getOperand(0)); 415 416 BlockT *BackedgeBlock = 417 IV->getIncomingBlock(contains(IV->getIncomingBlock(1))); 418 419 if (BranchInst *BI = dyn_cast<BranchInst>(BackedgeBlock->getTerminator())) 420 if (BI->isConditional()) { 421 if (ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition())) { 422 if (ICI->getOperand(0) == Inc) { 423 if (BI->getSuccessor(0) == getHeader()) { 424 if (ICI->getPredicate() == ICmpInst::ICMP_NE) 425 return ICI->getOperand(1); 426 } else if (ICI->getPredicate() == ICmpInst::ICMP_EQ) { 427 return ICI->getOperand(1); 428 } 429 } 430 } 431 } 432 433 return 0; 434 } 435 436 /// getSmallConstantTripCount - Returns the trip count of this loop as a 437 /// normal unsigned value, if possible. Returns 0 if the trip count is unknown 438 /// of not constant. Will also return 0 if the trip count is very large 439 /// (>= 2^32) 440 inline unsigned getSmallConstantTripCount() const { 441 Value* TripCount = this->getTripCount(); 442 if (TripCount) { 443 if (ConstantInt *TripCountC = dyn_cast<ConstantInt>(TripCount)) { 444 // Guard against huge trip counts. 445 if (TripCountC->getValue().getActiveBits() <= 32) { 446 return (unsigned)TripCountC->getZExtValue(); 447 } 448 } 449 } 450 return 0; 451 } 452 453 /// getSmallConstantTripMultiple - Returns the largest constant divisor of the 454 /// trip count of this loop as a normal unsigned value, if possible. This 455 /// means that the actual trip count is always a multiple of the returned 456 /// value (don't forget the trip count could very well be zero as well!). 457 /// 458 /// Returns 1 if the trip count is unknown or not guaranteed to be the 459 /// multiple of a constant (which is also the case if the trip count is simply 460 /// constant, use getSmallConstantTripCount for that case), Will also return 1 461 /// if the trip count is very large (>= 2^32). 462 inline unsigned getSmallConstantTripMultiple() const { 463 Value* TripCount = this->getTripCount(); 464 // This will hold the ConstantInt result, if any 465 ConstantInt *Result = NULL; 466 if (TripCount) { 467 // See if the trip count is constant itself 468 Result = dyn_cast<ConstantInt>(TripCount); 469 // if not, see if it is a multiplication 470 if (!Result) 471 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TripCount)) { 472 switch (BO->getOpcode()) { 473 case BinaryOperator::Mul: 474 Result = dyn_cast<ConstantInt>(BO->getOperand(1)); 475 break; 476 default: 477 break; 478 } 479 } 480 } 481 // Guard against huge trip counts. 482 if (Result && Result->getValue().getActiveBits() <= 32) { 483 return (unsigned)Result->getZExtValue(); 484 } else { 485 return 1; 486 } 487 } 488 489 /// isLCSSAForm - Return true if the Loop is in LCSSA form 490 inline bool isLCSSAForm() const { 491 // Sort the blocks vector so that we can use binary search to do quick 492 // lookups. 493 SmallPtrSet<BlockT*, 16> LoopBBs(block_begin(), block_end()); 494 495 for (block_iterator BI = block_begin(), E = block_end(); BI != E; ++BI) { 496 BlockT *BB = *BI; 497 for (typename BlockT::iterator I = BB->begin(), E = BB->end(); I != E;++I) 498 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E; 499 ++UI) { 500 BlockT *UserBB = cast<Instruction>(*UI)->getParent(); 501 if (PHINode *P = dyn_cast<PHINode>(*UI)) { 502 UserBB = P->getIncomingBlock(UI); 503 } 504 505 // Check the current block, as a fast-path. Most values are used in 506 // the same block they are defined in. 507 if (UserBB != BB && !LoopBBs.count(UserBB)) 508 return false; 509 } 510 } 511 512 return true; 513 } 514 515 //===--------------------------------------------------------------------===// 516 // APIs for updating loop information after changing the CFG 517 // 518 519 /// addBasicBlockToLoop - This method is used by other analyses to update loop 520 /// information. NewBB is set to be a new member of the current loop. 521 /// Because of this, it is added as a member of all parent loops, and is added 522 /// to the specified LoopInfo object as being in the current basic block. It 523 /// is not valid to replace the loop header with this method. 524 /// 525 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT> &LI); 526 527 /// replaceChildLoopWith - This is used when splitting loops up. It replaces 528 /// the OldChild entry in our children list with NewChild, and updates the 529 /// parent pointer of OldChild to be null and the NewChild to be this loop. 530 /// This updates the loop depth of the new child. 531 void replaceChildLoopWith(LoopBase<BlockT> *OldChild, 532 LoopBase<BlockT> *NewChild) { 533 assert(OldChild->ParentLoop == this && "This loop is already broken!"); 534 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 535 typename std::vector<LoopBase<BlockT>*>::iterator I = 536 std::find(SubLoops.begin(), SubLoops.end(), OldChild); 537 assert(I != SubLoops.end() && "OldChild not in loop!"); 538 *I = NewChild; 539 OldChild->ParentLoop = 0; 540 NewChild->ParentLoop = this; 541 } 542 543 /// addChildLoop - Add the specified loop to be a child of this loop. This 544 /// updates the loop depth of the new child. 545 /// 546 void addChildLoop(LoopBase<BlockT> *NewChild) { 547 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 548 NewChild->ParentLoop = this; 549 SubLoops.push_back(NewChild); 550 } 551 552 /// removeChildLoop - This removes the specified child from being a subloop of 553 /// this loop. The loop is not deleted, as it will presumably be inserted 554 /// into another loop. 555 LoopBase<BlockT> *removeChildLoop(iterator I) { 556 assert(I != SubLoops.end() && "Cannot remove end iterator!"); 557 LoopBase<BlockT> *Child = *I; 558 assert(Child->ParentLoop == this && "Child is not a child of this loop!"); 559 SubLoops.erase(SubLoops.begin()+(I-begin())); 560 Child->ParentLoop = 0; 561 return Child; 562 } 563 564 /// addBlockEntry - This adds a basic block directly to the basic block list. 565 /// This should only be used by transformations that create new loops. Other 566 /// transformations should use addBasicBlockToLoop. 567 void addBlockEntry(BlockT *BB) { 568 Blocks.push_back(BB); 569 } 570 571 /// moveToHeader - This method is used to move BB (which must be part of this 572 /// loop) to be the loop header of the loop (the block that dominates all 573 /// others). 574 void moveToHeader(BlockT *BB) { 575 if (Blocks[0] == BB) return; 576 for (unsigned i = 0; ; ++i) { 577 assert(i != Blocks.size() && "Loop does not contain BB!"); 578 if (Blocks[i] == BB) { 579 Blocks[i] = Blocks[0]; 580 Blocks[0] = BB; 581 return; 582 } 583 } 584 } 585 586 /// removeBlockFromLoop - This removes the specified basic block from the 587 /// current loop, updating the Blocks as appropriate. This does not update 588 /// the mapping in the LoopInfo class. 589 void removeBlockFromLoop(BlockT *BB) { 590 RemoveFromVector(Blocks, BB); 591 } 592 593 /// verifyLoop - Verify loop structure 594 void verifyLoop() const { 595#ifndef NDEBUG 596 assert (getHeader() && "Loop header is missing"); 597 assert (getLoopPreheader() && "Loop preheader is missing"); 598 assert (getLoopLatch() && "Loop latch is missing"); 599 for (iterator I = SubLoops.begin(), E = SubLoops.end(); I != E; ++I) 600 (*I)->verifyLoop(); 601#endif 602 } 603 604 void print(std::ostream &OS, unsigned Depth = 0) const { 605 OS << std::string(Depth*2, ' ') << "Loop at depth " << getLoopDepth() 606 << " containing: "; 607 608 for (unsigned i = 0; i < getBlocks().size(); ++i) { 609 if (i) OS << ","; 610 BlockT *BB = getBlocks()[i]; 611 WriteAsOperand(OS, BB, false); 612 if (BB == getHeader()) OS << "<header>"; 613 if (BB == getLoopLatch()) OS << "<latch>"; 614 if (isLoopExit(BB)) OS << "<exit>"; 615 } 616 OS << "\n"; 617 618 for (iterator I = begin(), E = end(); I != E; ++I) 619 (*I)->print(OS, Depth+2); 620 } 621 622 void print(std::ostream *O, unsigned Depth = 0) const { 623 if (O) print(*O, Depth); 624 } 625 626 void dump() const { 627 print(cerr); 628 } 629 630private: 631 friend class LoopInfoBase<BlockT>; 632 explicit LoopBase(BlockT *BB) : ParentLoop(0) { 633 Blocks.push_back(BB); 634 } 635}; 636 637 638//===----------------------------------------------------------------------===// 639/// LoopInfo - This class builds and contains all of the top level loop 640/// structures in the specified function. 641/// 642 643template<class BlockT> 644class LoopInfoBase { 645 // BBMap - Mapping of basic blocks to the inner most loop they occur in 646 std::map<BlockT*, LoopBase<BlockT>*> BBMap; 647 std::vector<LoopBase<BlockT>*> TopLevelLoops; 648 friend class LoopBase<BlockT>; 649 650public: 651 LoopInfoBase() { } 652 ~LoopInfoBase() { releaseMemory(); } 653 654 void releaseMemory() { 655 for (typename std::vector<LoopBase<BlockT>* >::iterator I = 656 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I) 657 delete *I; // Delete all of the loops... 658 659 BBMap.clear(); // Reset internal state of analysis 660 TopLevelLoops.clear(); 661 } 662 663 /// iterator/begin/end - The interface to the top-level loops in the current 664 /// function. 665 /// 666 typedef typename std::vector<LoopBase<BlockT>*>::const_iterator iterator; 667 iterator begin() const { return TopLevelLoops.begin(); } 668 iterator end() const { return TopLevelLoops.end(); } 669 bool empty() const { return TopLevelLoops.empty(); } 670 671 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 672 /// block is in no loop (for example the entry node), null is returned. 673 /// 674 LoopBase<BlockT> *getLoopFor(const BlockT *BB) const { 675 typename std::map<BlockT *, LoopBase<BlockT>*>::const_iterator I= 676 BBMap.find(const_cast<BlockT*>(BB)); 677 return I != BBMap.end() ? I->second : 0; 678 } 679 680 /// operator[] - same as getLoopFor... 681 /// 682 const LoopBase<BlockT> *operator[](const BlockT *BB) const { 683 return getLoopFor(BB); 684 } 685 686 /// getLoopDepth - Return the loop nesting level of the specified block. A 687 /// depth of 0 means the block is not inside any loop. 688 /// 689 unsigned getLoopDepth(const BlockT *BB) const { 690 const LoopBase<BlockT> *L = getLoopFor(BB); 691 return L ? L->getLoopDepth() : 0; 692 } 693 694 // isLoopHeader - True if the block is a loop header node 695 bool isLoopHeader(BlockT *BB) const { 696 const LoopBase<BlockT> *L = getLoopFor(BB); 697 return L && L->getHeader() == BB; 698 } 699 700 /// removeLoop - This removes the specified top-level loop from this loop info 701 /// object. The loop is not deleted, as it will presumably be inserted into 702 /// another loop. 703 LoopBase<BlockT> *removeLoop(iterator I) { 704 assert(I != end() && "Cannot remove end iterator!"); 705 LoopBase<BlockT> *L = *I; 706 assert(L->getParentLoop() == 0 && "Not a top-level loop!"); 707 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin())); 708 return L; 709 } 710 711 /// changeLoopFor - Change the top-level loop that contains BB to the 712 /// specified loop. This should be used by transformations that restructure 713 /// the loop hierarchy tree. 714 void changeLoopFor(BlockT *BB, LoopBase<BlockT> *L) { 715 LoopBase<BlockT> *&OldLoop = BBMap[BB]; 716 assert(OldLoop && "Block not in a loop yet!"); 717 OldLoop = L; 718 } 719 720 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 721 /// list with the indicated loop. 722 void changeTopLevelLoop(LoopBase<BlockT> *OldLoop, 723 LoopBase<BlockT> *NewLoop) { 724 typename std::vector<LoopBase<BlockT>*>::iterator I = 725 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop); 726 assert(I != TopLevelLoops.end() && "Old loop not at top level!"); 727 *I = NewLoop; 728 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 && 729 "Loops already embedded into a subloop!"); 730 } 731 732 /// addTopLevelLoop - This adds the specified loop to the collection of 733 /// top-level loops. 734 void addTopLevelLoop(LoopBase<BlockT> *New) { 735 assert(New->getParentLoop() == 0 && "Loop already in subloop!"); 736 TopLevelLoops.push_back(New); 737 } 738 739 /// removeBlock - This method completely removes BB from all data structures, 740 /// including all of the Loop objects it is nested in and our mapping from 741 /// BasicBlocks to loops. 742 void removeBlock(BlockT *BB) { 743 typename std::map<BlockT *, LoopBase<BlockT>*>::iterator I = BBMap.find(BB); 744 if (I != BBMap.end()) { 745 for (LoopBase<BlockT> *L = I->second; L; L = L->getParentLoop()) 746 L->removeBlockFromLoop(BB); 747 748 BBMap.erase(I); 749 } 750 } 751 752 // Internals 753 754 static bool isNotAlreadyContainedIn(const LoopBase<BlockT> *SubLoop, 755 const LoopBase<BlockT> *ParentLoop) { 756 if (SubLoop == 0) return true; 757 if (SubLoop == ParentLoop) return false; 758 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop); 759 } 760 761 void Calculate(DominatorTreeBase<BlockT> &DT) { 762 BlockT *RootNode = DT.getRootNode()->getBlock(); 763 764 for (df_iterator<BlockT*> NI = df_begin(RootNode), 765 NE = df_end(RootNode); NI != NE; ++NI) 766 if (LoopBase<BlockT> *L = ConsiderForLoop(*NI, DT)) 767 TopLevelLoops.push_back(L); 768 } 769 770 LoopBase<BlockT> *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) { 771 if (BBMap.find(BB) != BBMap.end()) return 0;// Haven't processed this node? 772 773 std::vector<BlockT *> TodoStack; 774 775 // Scan the predecessors of BB, checking to see if BB dominates any of 776 // them. This identifies backedges which target this node... 777 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 778 for (typename InvBlockTraits::ChildIteratorType I = 779 InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB); 780 I != E; ++I) 781 if (DT.dominates(BB, *I)) // If BB dominates it's predecessor... 782 TodoStack.push_back(*I); 783 784 if (TodoStack.empty()) return 0; // No backedges to this block... 785 786 // Create a new loop to represent this basic block... 787 LoopBase<BlockT> *L = new LoopBase<BlockT>(BB); 788 BBMap[BB] = L; 789 790 BlockT *EntryBlock = BB->getParent()->begin(); 791 792 while (!TodoStack.empty()) { // Process all the nodes in the loop 793 BlockT *X = TodoStack.back(); 794 TodoStack.pop_back(); 795 796 if (!L->contains(X) && // As of yet unprocessed?? 797 DT.dominates(EntryBlock, X)) { // X is reachable from entry block? 798 // Check to see if this block already belongs to a loop. If this occurs 799 // then we have a case where a loop that is supposed to be a child of 800 // the current loop was processed before the current loop. When this 801 // occurs, this child loop gets added to a part of the current loop, 802 // making it a sibling to the current loop. We have to reparent this 803 // loop. 804 if (LoopBase<BlockT> *SubLoop = 805 const_cast<LoopBase<BlockT>*>(getLoopFor(X))) 806 if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){ 807 // Remove the subloop from it's current parent... 808 assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L); 809 LoopBase<BlockT> *SLP = SubLoop->ParentLoop; // SubLoopParent 810 typename std::vector<LoopBase<BlockT>*>::iterator I = 811 std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop); 812 assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?"); 813 SLP->SubLoops.erase(I); // Remove from parent... 814 815 // Add the subloop to THIS loop... 816 SubLoop->ParentLoop = L; 817 L->SubLoops.push_back(SubLoop); 818 } 819 820 // Normal case, add the block to our loop... 821 L->Blocks.push_back(X); 822 823 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 824 825 // Add all of the predecessors of X to the end of the work stack... 826 TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X), 827 InvBlockTraits::child_end(X)); 828 } 829 } 830 831 // If there are any loops nested within this loop, create them now! 832 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 833 E = L->Blocks.end(); I != E; ++I) 834 if (LoopBase<BlockT> *NewLoop = ConsiderForLoop(*I, DT)) { 835 L->SubLoops.push_back(NewLoop); 836 NewLoop->ParentLoop = L; 837 } 838 839 // Add the basic blocks that comprise this loop to the BBMap so that this 840 // loop can be found for them. 841 // 842 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 843 E = L->Blocks.end(); I != E; ++I) { 844 typename std::map<BlockT*, LoopBase<BlockT>*>::iterator BBMI = 845 BBMap.find(*I); 846 if (BBMI == BBMap.end()) // Not in map yet... 847 BBMap.insert(BBMI, std::make_pair(*I, L)); // Must be at this level 848 } 849 850 // Now that we have a list of all of the child loops of this loop, check to 851 // see if any of them should actually be nested inside of each other. We 852 // can accidentally pull loops our of their parents, so we must make sure to 853 // organize the loop nests correctly now. 854 { 855 std::map<BlockT*, LoopBase<BlockT>*> ContainingLoops; 856 for (unsigned i = 0; i != L->SubLoops.size(); ++i) { 857 LoopBase<BlockT> *Child = L->SubLoops[i]; 858 assert(Child->getParentLoop() == L && "Not proper child loop?"); 859 860 if (LoopBase<BlockT> *ContainingLoop = 861 ContainingLoops[Child->getHeader()]) { 862 // If there is already a loop which contains this loop, move this loop 863 // into the containing loop. 864 MoveSiblingLoopInto(Child, ContainingLoop); 865 --i; // The loop got removed from the SubLoops list. 866 } else { 867 // This is currently considered to be a top-level loop. Check to see 868 // if any of the contained blocks are loop headers for subloops we 869 // have already processed. 870 for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) { 871 LoopBase<BlockT> *&BlockLoop = ContainingLoops[Child->Blocks[b]]; 872 if (BlockLoop == 0) { // Child block not processed yet... 873 BlockLoop = Child; 874 } else if (BlockLoop != Child) { 875 LoopBase<BlockT> *SubLoop = BlockLoop; 876 // Reparent all of the blocks which used to belong to BlockLoops 877 for (unsigned j = 0, e = SubLoop->Blocks.size(); j != e; ++j) 878 ContainingLoops[SubLoop->Blocks[j]] = Child; 879 880 // There is already a loop which contains this block, that means 881 // that we should reparent the loop which the block is currently 882 // considered to belong to to be a child of this loop. 883 MoveSiblingLoopInto(SubLoop, Child); 884 --i; // We just shrunk the SubLoops list. 885 } 886 } 887 } 888 } 889 } 890 891 return L; 892 } 893 894 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside 895 /// of the NewParent Loop, instead of being a sibling of it. 896 void MoveSiblingLoopInto(LoopBase<BlockT> *NewChild, 897 LoopBase<BlockT> *NewParent) { 898 LoopBase<BlockT> *OldParent = NewChild->getParentLoop(); 899 assert(OldParent && OldParent == NewParent->getParentLoop() && 900 NewChild != NewParent && "Not sibling loops!"); 901 902 // Remove NewChild from being a child of OldParent 903 typename std::vector<LoopBase<BlockT>*>::iterator I = 904 std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(), 905 NewChild); 906 assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??"); 907 OldParent->SubLoops.erase(I); // Remove from parent's subloops list 908 NewChild->ParentLoop = 0; 909 910 InsertLoopInto(NewChild, NewParent); 911 } 912 913 /// InsertLoopInto - This inserts loop L into the specified parent loop. If 914 /// the parent loop contains a loop which should contain L, the loop gets 915 /// inserted into L instead. 916 void InsertLoopInto(LoopBase<BlockT> *L, LoopBase<BlockT> *Parent) { 917 BlockT *LHeader = L->getHeader(); 918 assert(Parent->contains(LHeader) && 919 "This loop should not be inserted here!"); 920 921 // Check to see if it belongs in a child loop... 922 for (unsigned i = 0, e = static_cast<unsigned>(Parent->SubLoops.size()); 923 i != e; ++i) 924 if (Parent->SubLoops[i]->contains(LHeader)) { 925 InsertLoopInto(L, Parent->SubLoops[i]); 926 return; 927 } 928 929 // If not, insert it here! 930 Parent->SubLoops.push_back(L); 931 L->ParentLoop = Parent; 932 } 933 934 // Debugging 935 936 void print(std::ostream &OS, const Module* ) const { 937 for (unsigned i = 0; i < TopLevelLoops.size(); ++i) 938 TopLevelLoops[i]->print(OS); 939 #if 0 940 for (std::map<BasicBlock*, Loop*>::const_iterator I = BBMap.begin(), 941 E = BBMap.end(); I != E; ++I) 942 OS << "BB '" << I->first->getName() << "' level = " 943 << I->second->getLoopDepth() << "\n"; 944 #endif 945 } 946}; 947 948class LoopInfo : public FunctionPass { 949 LoopInfoBase<BasicBlock>* LI; 950 friend class LoopBase<BasicBlock>; 951 952public: 953 static char ID; // Pass identification, replacement for typeid 954 955 LoopInfo() : FunctionPass(&ID) { 956 LI = new LoopInfoBase<BasicBlock>(); 957 } 958 959 ~LoopInfo() { delete LI; } 960 961 LoopInfoBase<BasicBlock>& getBase() { return *LI; } 962 963 /// iterator/begin/end - The interface to the top-level loops in the current 964 /// function. 965 /// 966 typedef std::vector<Loop*>::const_iterator iterator; 967 inline iterator begin() const { return LI->begin(); } 968 inline iterator end() const { return LI->end(); } 969 bool empty() const { return LI->empty(); } 970 971 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 972 /// block is in no loop (for example the entry node), null is returned. 973 /// 974 inline Loop *getLoopFor(const BasicBlock *BB) const { 975 return LI->getLoopFor(BB); 976 } 977 978 /// operator[] - same as getLoopFor... 979 /// 980 inline const Loop *operator[](const BasicBlock *BB) const { 981 return LI->getLoopFor(BB); 982 } 983 984 /// getLoopDepth - Return the loop nesting level of the specified block. A 985 /// depth of 0 means the block is not inside any loop. 986 /// 987 inline unsigned getLoopDepth(const BasicBlock *BB) const { 988 return LI->getLoopDepth(BB); 989 } 990 991 // isLoopHeader - True if the block is a loop header node 992 inline bool isLoopHeader(BasicBlock *BB) const { 993 return LI->isLoopHeader(BB); 994 } 995 996 /// runOnFunction - Calculate the natural loop information. 997 /// 998 virtual bool runOnFunction(Function &F); 999 1000 virtual void releaseMemory() { LI->releaseMemory(); } 1001 1002 virtual void print(std::ostream &O, const Module* M = 0) const { 1003 if (O) LI->print(O, M); 1004 } 1005 1006 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 1007 1008 /// removeLoop - This removes the specified top-level loop from this loop info 1009 /// object. The loop is not deleted, as it will presumably be inserted into 1010 /// another loop. 1011 inline Loop *removeLoop(iterator I) { return LI->removeLoop(I); } 1012 1013 /// changeLoopFor - Change the top-level loop that contains BB to the 1014 /// specified loop. This should be used by transformations that restructure 1015 /// the loop hierarchy tree. 1016 inline void changeLoopFor(BasicBlock *BB, Loop *L) { 1017 LI->changeLoopFor(BB, L); 1018 } 1019 1020 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 1021 /// list with the indicated loop. 1022 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) { 1023 LI->changeTopLevelLoop(OldLoop, NewLoop); 1024 } 1025 1026 /// addTopLevelLoop - This adds the specified loop to the collection of 1027 /// top-level loops. 1028 inline void addTopLevelLoop(Loop *New) { 1029 LI->addTopLevelLoop(New); 1030 } 1031 1032 /// removeBlock - This method completely removes BB from all data structures, 1033 /// including all of the Loop objects it is nested in and our mapping from 1034 /// BasicBlocks to loops. 1035 void removeBlock(BasicBlock *BB) { 1036 LI->removeBlock(BB); 1037 } 1038}; 1039 1040 1041// Allow clients to walk the list of nested loops... 1042template <> struct GraphTraits<const Loop*> { 1043 typedef const Loop NodeType; 1044 typedef std::vector<Loop*>::const_iterator ChildIteratorType; 1045 1046 static NodeType *getEntryNode(const Loop *L) { return L; } 1047 static inline ChildIteratorType child_begin(NodeType *N) { 1048 return N->begin(); 1049 } 1050 static inline ChildIteratorType child_end(NodeType *N) { 1051 return N->end(); 1052 } 1053}; 1054 1055template <> struct GraphTraits<Loop*> { 1056 typedef Loop NodeType; 1057 typedef std::vector<Loop*>::const_iterator ChildIteratorType; 1058 1059 static NodeType *getEntryNode(Loop *L) { return L; } 1060 static inline ChildIteratorType child_begin(NodeType *N) { 1061 return N->begin(); 1062 } 1063 static inline ChildIteratorType child_end(NodeType *N) { 1064 return N->end(); 1065 } 1066}; 1067 1068template<class BlockT> 1069void LoopBase<BlockT>::addBasicBlockToLoop(BlockT *NewBB, 1070 LoopInfoBase<BlockT> &LIB) { 1071 assert((Blocks.empty() || LIB[getHeader()] == this) && 1072 "Incorrect LI specified for this loop!"); 1073 assert(NewBB && "Cannot add a null basic block to the loop!"); 1074 assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!"); 1075 1076 // Add the loop mapping to the LoopInfo object... 1077 LIB.BBMap[NewBB] = this; 1078 1079 // Add the basic block to this loop and all parent loops... 1080 LoopBase<BlockT> *L = this; 1081 while (L) { 1082 L->Blocks.push_back(NewBB); 1083 L = L->getParentLoop(); 1084 } 1085} 1086 1087} // End llvm namespace 1088 1089#endif 1090