LoopInfo.h revision c8d76d5afb023a1c6b439941be3b62789fcc0ed3
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; 57class Loop; 58template<class N, class M> class LoopInfoBase; 59template<class N, class M> class LoopBase; 60 61//===----------------------------------------------------------------------===// 62/// LoopBase class - Instances of this class are used to represent loops that 63/// are detected in the flow graph 64/// 65template<class BlockT, class LoopT> 66class LoopBase { 67 LoopT *ParentLoop; 68 // SubLoops - Loops contained entirely within this one. 69 std::vector<LoopT *> SubLoops; 70 71 // Blocks - The list of blocks in this loop. First entry is the header node. 72 std::vector<BlockT*> Blocks; 73 74 // DO NOT IMPLEMENT 75 LoopBase(const LoopBase<BlockT, LoopT> &); 76 // DO NOT IMPLEMENT 77 const LoopBase<BlockT, LoopT>&operator=(const LoopBase<BlockT, LoopT> &); 78public: 79 /// Loop ctor - This creates an empty loop. 80 LoopBase() : ParentLoop(0) {} 81 ~LoopBase() { 82 for (size_t i = 0, e = SubLoops.size(); i != e; ++i) 83 delete SubLoops[i]; 84 } 85 86 /// getLoopDepth - Return the nesting level of this loop. An outer-most 87 /// loop has depth 1, for consistency with loop depth values used for basic 88 /// blocks, where depth 0 is used for blocks not inside any loops. 89 unsigned getLoopDepth() const { 90 unsigned D = 1; 91 for (const LoopT *CurLoop = ParentLoop; CurLoop; 92 CurLoop = CurLoop->ParentLoop) 93 ++D; 94 return D; 95 } 96 BlockT *getHeader() const { return Blocks.front(); } 97 LoopT *getParentLoop() const { return ParentLoop; } 98 99 /// contains - Return true if the specified basic block is in this loop 100 /// 101 bool contains(const BlockT *BB) const { 102 return std::find(block_begin(), block_end(), BB) != block_end(); 103 } 104 105 /// iterator/begin/end - Return the loops contained entirely within this loop. 106 /// 107 const std::vector<LoopT *> &getSubLoops() const { return SubLoops; } 108 typedef typename std::vector<LoopT *>::const_iterator iterator; 109 iterator begin() const { return SubLoops.begin(); } 110 iterator end() const { return SubLoops.end(); } 111 bool empty() const { return SubLoops.empty(); } 112 113 /// getBlocks - Get a list of the basic blocks which make up this loop. 114 /// 115 const std::vector<BlockT*> &getBlocks() const { return Blocks; } 116 typedef typename std::vector<BlockT*>::const_iterator block_iterator; 117 block_iterator block_begin() const { return Blocks.begin(); } 118 block_iterator block_end() const { return Blocks.end(); } 119 120 /// isLoopExit - True if terminator in the block can branch to another block 121 /// that is outside of the current loop. 122 /// 123 bool isLoopExit(const BlockT *BB) const { 124 typedef GraphTraits<BlockT*> BlockTraits; 125 for (typename BlockTraits::ChildIteratorType SI = 126 BlockTraits::child_begin(const_cast<BlockT*>(BB)), 127 SE = BlockTraits::child_end(const_cast<BlockT*>(BB)); SI != SE; ++SI) { 128 if (!contains(*SI)) 129 return true; 130 } 131 return false; 132 } 133 134 /// getNumBackEdges - Calculate the number of back edges to the loop header 135 /// 136 unsigned getNumBackEdges() const { 137 unsigned NumBackEdges = 0; 138 BlockT *H = getHeader(); 139 140 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 141 for (typename InvBlockTraits::ChildIteratorType I = 142 InvBlockTraits::child_begin(const_cast<BlockT*>(H)), 143 E = InvBlockTraits::child_end(const_cast<BlockT*>(H)); I != E; ++I) 144 if (contains(*I)) 145 ++NumBackEdges; 146 147 return NumBackEdges; 148 } 149 150 /// isLoopInvariant - Return true if the specified value is loop invariant 151 /// 152 inline bool isLoopInvariant(Value *V) const { 153 if (Instruction *I = dyn_cast<Instruction>(V)) 154 return !contains(I->getParent()); 155 return true; // All non-instructions are loop invariant 156 } 157 158 //===--------------------------------------------------------------------===// 159 // APIs for simple analysis of the loop. 160 // 161 // Note that all of these methods can fail on general loops (ie, there may not 162 // be a preheader, etc). For best success, the loop simplification and 163 // induction variable canonicalization pass should be used to normalize loops 164 // for easy analysis. These methods assume canonical loops. 165 166 /// getExitingBlocks - Return all blocks inside the loop that have successors 167 /// outside of the loop. These are the blocks _inside of the current loop_ 168 /// which branch out. The returned list is always unique. 169 /// 170 void getExitingBlocks(SmallVectorImpl<BlockT *> &ExitingBlocks) const { 171 // Sort the blocks vector so that we can use binary search to do quick 172 // lookups. 173 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 174 std::sort(LoopBBs.begin(), LoopBBs.end()); 175 176 typedef GraphTraits<BlockT*> BlockTraits; 177 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) 178 for (typename BlockTraits::ChildIteratorType I = 179 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 180 I != E; ++I) 181 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) { 182 // Not in current loop? It must be an exit block. 183 ExitingBlocks.push_back(*BI); 184 break; 185 } 186 } 187 188 /// getExitingBlock - If getExitingBlocks would return exactly one block, 189 /// return that block. Otherwise return null. 190 BlockT *getExitingBlock() const { 191 SmallVector<BlockT*, 8> ExitingBlocks; 192 getExitingBlocks(ExitingBlocks); 193 if (ExitingBlocks.size() == 1) 194 return ExitingBlocks[0]; 195 return 0; 196 } 197 198 /// getExitBlocks - Return all of the successor blocks of this loop. These 199 /// are the blocks _outside of the current loop_ which are branched to. 200 /// 201 void getExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const { 202 // Sort the blocks vector so that we can use binary search to do quick 203 // lookups. 204 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 205 std::sort(LoopBBs.begin(), LoopBBs.end()); 206 207 typedef GraphTraits<BlockT*> BlockTraits; 208 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) 209 for (typename BlockTraits::ChildIteratorType I = 210 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 211 I != E; ++I) 212 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) 213 // Not in current loop? It must be an exit block. 214 ExitBlocks.push_back(*I); 215 } 216 217 /// getExitBlock - If getExitBlocks would return exactly one block, 218 /// return that block. Otherwise return null. 219 BlockT *getExitBlock() const { 220 SmallVector<BlockT*, 8> ExitBlocks; 221 getExitBlocks(ExitBlocks); 222 if (ExitBlocks.size() == 1) 223 return ExitBlocks[0]; 224 return 0; 225 } 226 227 /// getUniqueExitBlocks - Return all unique successor blocks of this loop. 228 /// These are the blocks _outside of the current loop_ which are branched to. 229 /// This assumes that loop is in canonical form. 230 /// 231 void getUniqueExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const { 232 // Sort the blocks vector so that we can use binary search to do quick 233 // lookups. 234 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 235 std::sort(LoopBBs.begin(), LoopBBs.end()); 236 237 std::vector<BlockT*> switchExitBlocks; 238 239 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) { 240 241 BlockT *current = *BI; 242 switchExitBlocks.clear(); 243 244 typedef GraphTraits<BlockT*> BlockTraits; 245 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 246 for (typename BlockTraits::ChildIteratorType I = 247 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 248 I != E; ++I) { 249 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) 250 // If block is inside the loop then it is not a exit block. 251 continue; 252 253 typename InvBlockTraits::ChildIteratorType PI = 254 InvBlockTraits::child_begin(*I); 255 BlockT *firstPred = *PI; 256 257 // If current basic block is this exit block's first predecessor 258 // then only insert exit block in to the output ExitBlocks vector. 259 // This ensures that same exit block is not inserted twice into 260 // ExitBlocks vector. 261 if (current != firstPred) 262 continue; 263 264 // If a terminator has more then two successors, for example SwitchInst, 265 // then it is possible that there are multiple edges from current block 266 // to one exit block. 267 if (std::distance(BlockTraits::child_begin(current), 268 BlockTraits::child_end(current)) <= 2) { 269 ExitBlocks.push_back(*I); 270 continue; 271 } 272 273 // In case of multiple edges from current block to exit block, collect 274 // only one edge in ExitBlocks. Use switchExitBlocks to keep track of 275 // duplicate edges. 276 if (std::find(switchExitBlocks.begin(), switchExitBlocks.end(), *I) 277 == switchExitBlocks.end()) { 278 switchExitBlocks.push_back(*I); 279 ExitBlocks.push_back(*I); 280 } 281 } 282 } 283 } 284 285 /// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one 286 /// block, return that block. Otherwise return null. 287 BlockT *getUniqueExitBlock() const { 288 SmallVector<BlockT*, 8> UniqueExitBlocks; 289 getUniqueExitBlocks(UniqueExitBlocks); 290 if (UniqueExitBlocks.size() == 1) 291 return UniqueExitBlocks[0]; 292 return 0; 293 } 294 295 /// getLoopPreheader - If there is a preheader for this loop, return it. A 296 /// loop has a preheader if there is only one edge to the header of the loop 297 /// from outside of the loop. If this is the case, the block branching to the 298 /// header of the loop is the preheader node. 299 /// 300 /// This method returns null if there is no preheader for the loop. 301 /// 302 BlockT *getLoopPreheader() const { 303 // Keep track of nodes outside the loop branching to the header... 304 BlockT *Out = 0; 305 306 // Loop over the predecessors of the header node... 307 BlockT *Header = getHeader(); 308 typedef GraphTraits<BlockT*> BlockTraits; 309 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 310 for (typename InvBlockTraits::ChildIteratorType PI = 311 InvBlockTraits::child_begin(Header), 312 PE = InvBlockTraits::child_end(Header); PI != PE; ++PI) 313 if (!contains(*PI)) { // If the block is not in the loop... 314 if (Out && Out != *PI) 315 return 0; // Multiple predecessors outside the loop 316 Out = *PI; 317 } 318 319 // Make sure there is only one exit out of the preheader. 320 assert(Out && "Header of loop has no predecessors from outside loop?"); 321 typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out); 322 ++SI; 323 if (SI != BlockTraits::child_end(Out)) 324 return 0; // Multiple exits from the block, must not be a preheader. 325 326 // If there is exactly one preheader, return it. If there was zero, then 327 // Out is still null. 328 return Out; 329 } 330 331 /// getLoopLatch - If there is a single latch block for this loop, return it. 332 /// A latch block is a block that contains a branch back to the header. 333 /// A loop header in normal form has two edges into it: one from a preheader 334 /// and one from a latch block. 335 BlockT *getLoopLatch() const { 336 BlockT *Header = getHeader(); 337 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 338 typename InvBlockTraits::ChildIteratorType PI = 339 InvBlockTraits::child_begin(Header); 340 typename InvBlockTraits::ChildIteratorType PE = 341 InvBlockTraits::child_end(Header); 342 if (PI == PE) return 0; // no preds? 343 344 BlockT *Latch = 0; 345 if (contains(*PI)) 346 Latch = *PI; 347 ++PI; 348 if (PI == PE) return 0; // only one pred? 349 350 if (contains(*PI)) { 351 if (Latch) return 0; // multiple backedges 352 Latch = *PI; 353 } 354 ++PI; 355 if (PI != PE) return 0; // more than two preds 356 357 return Latch; 358 } 359 360 /// getCanonicalInductionVariable - Check to see if the loop has a canonical 361 /// induction variable: an integer recurrence that starts at 0 and increments 362 /// by one each time through the loop. If so, return the phi node that 363 /// corresponds to it. 364 /// 365 /// The IndVarSimplify pass transforms loops to have a canonical induction 366 /// variable. 367 /// 368 inline PHINode *getCanonicalInductionVariable() const { 369 BlockT *H = getHeader(); 370 371 BlockT *Incoming = 0, *Backedge = 0; 372 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 373 typename InvBlockTraits::ChildIteratorType PI = 374 InvBlockTraits::child_begin(H); 375 assert(PI != InvBlockTraits::child_end(H) && 376 "Loop must have at least one backedge!"); 377 Backedge = *PI++; 378 if (PI == InvBlockTraits::child_end(H)) return 0; // dead loop 379 Incoming = *PI++; 380 if (PI != InvBlockTraits::child_end(H)) return 0; // multiple backedges? 381 382 if (contains(Incoming)) { 383 if (contains(Backedge)) 384 return 0; 385 std::swap(Incoming, Backedge); 386 } else if (!contains(Backedge)) 387 return 0; 388 389 // Loop over all of the PHI nodes, looking for a canonical indvar. 390 for (typename BlockT::iterator I = H->begin(); isa<PHINode>(I); ++I) { 391 PHINode *PN = cast<PHINode>(I); 392 if (ConstantInt *CI = 393 dyn_cast<ConstantInt>(PN->getIncomingValueForBlock(Incoming))) 394 if (CI->isNullValue()) 395 if (Instruction *Inc = 396 dyn_cast<Instruction>(PN->getIncomingValueForBlock(Backedge))) 397 if (Inc->getOpcode() == Instruction::Add && 398 Inc->getOperand(0) == PN) 399 if (ConstantInt *CI = dyn_cast<ConstantInt>(Inc->getOperand(1))) 400 if (CI->equalsInt(1)) 401 return PN; 402 } 403 return 0; 404 } 405 406 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds 407 /// the canonical induction variable value for the "next" iteration of the 408 /// loop. This always succeeds if getCanonicalInductionVariable succeeds. 409 /// 410 inline Instruction *getCanonicalInductionVariableIncrement() const { 411 if (PHINode *PN = getCanonicalInductionVariable()) { 412 bool P1InLoop = contains(PN->getIncomingBlock(1)); 413 return cast<Instruction>(PN->getIncomingValue(P1InLoop)); 414 } 415 return 0; 416 } 417 418 /// getTripCount - Return a loop-invariant LLVM value indicating the number of 419 /// times the loop will be executed. Note that this means that the backedge 420 /// of the loop executes N-1 times. If the trip-count cannot be determined, 421 /// this returns null. 422 /// 423 /// The IndVarSimplify pass transforms loops to have a form that this 424 /// function easily understands. 425 /// 426 inline Value *getTripCount() const { 427 // Canonical loops will end with a 'cmp ne I, V', where I is the incremented 428 // canonical induction variable and V is the trip count of the loop. 429 Instruction *Inc = getCanonicalInductionVariableIncrement(); 430 if (Inc == 0) return 0; 431 PHINode *IV = cast<PHINode>(Inc->getOperand(0)); 432 433 BlockT *BackedgeBlock = 434 IV->getIncomingBlock(contains(IV->getIncomingBlock(1))); 435 436 if (BranchInst *BI = dyn_cast<BranchInst>(BackedgeBlock->getTerminator())) 437 if (BI->isConditional()) { 438 if (ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition())) { 439 if (ICI->getOperand(0) == Inc) { 440 if (BI->getSuccessor(0) == getHeader()) { 441 if (ICI->getPredicate() == ICmpInst::ICMP_NE) 442 return ICI->getOperand(1); 443 } else if (ICI->getPredicate() == ICmpInst::ICMP_EQ) { 444 return ICI->getOperand(1); 445 } 446 } 447 } 448 } 449 450 return 0; 451 } 452 453 /// getSmallConstantTripCount - Returns the trip count of this loop as a 454 /// normal unsigned value, if possible. Returns 0 if the trip count is unknown 455 /// of not constant. Will also return 0 if the trip count is very large 456 /// (>= 2^32) 457 inline unsigned getSmallConstantTripCount() const { 458 Value* TripCount = this->getTripCount(); 459 if (TripCount) { 460 if (ConstantInt *TripCountC = dyn_cast<ConstantInt>(TripCount)) { 461 // Guard against huge trip counts. 462 if (TripCountC->getValue().getActiveBits() <= 32) { 463 return (unsigned)TripCountC->getZExtValue(); 464 } 465 } 466 } 467 return 0; 468 } 469 470 /// getSmallConstantTripMultiple - Returns the largest constant divisor of the 471 /// trip count of this loop as a normal unsigned value, if possible. This 472 /// means that the actual trip count is always a multiple of the returned 473 /// value (don't forget the trip count could very well be zero as well!). 474 /// 475 /// Returns 1 if the trip count is unknown or not guaranteed to be the 476 /// multiple of a constant (which is also the case if the trip count is simply 477 /// constant, use getSmallConstantTripCount for that case), Will also return 1 478 /// if the trip count is very large (>= 2^32). 479 inline unsigned getSmallConstantTripMultiple() const { 480 Value* TripCount = this->getTripCount(); 481 // This will hold the ConstantInt result, if any 482 ConstantInt *Result = NULL; 483 if (TripCount) { 484 // See if the trip count is constant itself 485 Result = dyn_cast<ConstantInt>(TripCount); 486 // if not, see if it is a multiplication 487 if (!Result) 488 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TripCount)) { 489 switch (BO->getOpcode()) { 490 case BinaryOperator::Mul: 491 Result = dyn_cast<ConstantInt>(BO->getOperand(1)); 492 break; 493 default: 494 break; 495 } 496 } 497 } 498 // Guard against huge trip counts. 499 if (Result && Result->getValue().getActiveBits() <= 32) { 500 return (unsigned)Result->getZExtValue(); 501 } else { 502 return 1; 503 } 504 } 505 506 /// isLCSSAForm - Return true if the Loop is in LCSSA form 507 inline bool isLCSSAForm() const { 508 // Sort the blocks vector so that we can use binary search to do quick 509 // lookups. 510 SmallPtrSet<BlockT*, 16> LoopBBs(block_begin(), block_end()); 511 512 for (block_iterator BI = block_begin(), E = block_end(); BI != E; ++BI) { 513 BlockT *BB = *BI; 514 for (typename BlockT::iterator I = BB->begin(), E = BB->end(); I != E;++I) 515 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E; 516 ++UI) { 517 BlockT *UserBB = cast<Instruction>(*UI)->getParent(); 518 if (PHINode *P = dyn_cast<PHINode>(*UI)) { 519 UserBB = P->getIncomingBlock(UI); 520 } 521 522 // Check the current block, as a fast-path. Most values are used in 523 // the same block they are defined in. 524 if (UserBB != BB && !LoopBBs.count(UserBB)) 525 return false; 526 } 527 } 528 529 return true; 530 } 531 532 //===--------------------------------------------------------------------===// 533 // APIs for updating loop information after changing the CFG 534 // 535 536 /// addBasicBlockToLoop - This method is used by other analyses to update loop 537 /// information. NewBB is set to be a new member of the current loop. 538 /// Because of this, it is added as a member of all parent loops, and is added 539 /// to the specified LoopInfo object as being in the current basic block. It 540 /// is not valid to replace the loop header with this method. 541 /// 542 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LI); 543 544 /// replaceChildLoopWith - This is used when splitting loops up. It replaces 545 /// the OldChild entry in our children list with NewChild, and updates the 546 /// parent pointer of OldChild to be null and the NewChild to be this loop. 547 /// This updates the loop depth of the new child. 548 void replaceChildLoopWith(LoopT *OldChild, 549 LoopT *NewChild) { 550 assert(OldChild->ParentLoop == this && "This loop is already broken!"); 551 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 552 typename std::vector<LoopT *>::iterator I = 553 std::find(SubLoops.begin(), SubLoops.end(), OldChild); 554 assert(I != SubLoops.end() && "OldChild not in loop!"); 555 *I = NewChild; 556 OldChild->ParentLoop = 0; 557 NewChild->ParentLoop = static_cast<LoopT *>(this); 558 } 559 560 /// addChildLoop - Add the specified loop to be a child of this loop. This 561 /// updates the loop depth of the new child. 562 /// 563 void addChildLoop(LoopT *NewChild) { 564 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 565 NewChild->ParentLoop = static_cast<LoopT *>(this); 566 SubLoops.push_back(NewChild); 567 } 568 569 /// removeChildLoop - This removes the specified child from being a subloop of 570 /// this loop. The loop is not deleted, as it will presumably be inserted 571 /// into another loop. 572 LoopT *removeChildLoop(iterator I) { 573 assert(I != SubLoops.end() && "Cannot remove end iterator!"); 574 LoopT *Child = *I; 575 assert(Child->ParentLoop == this && "Child is not a child of this loop!"); 576 SubLoops.erase(SubLoops.begin()+(I-begin())); 577 Child->ParentLoop = 0; 578 return Child; 579 } 580 581 /// addBlockEntry - This adds a basic block directly to the basic block list. 582 /// This should only be used by transformations that create new loops. Other 583 /// transformations should use addBasicBlockToLoop. 584 void addBlockEntry(BlockT *BB) { 585 Blocks.push_back(BB); 586 } 587 588 /// moveToHeader - This method is used to move BB (which must be part of this 589 /// loop) to be the loop header of the loop (the block that dominates all 590 /// others). 591 void moveToHeader(BlockT *BB) { 592 if (Blocks[0] == BB) return; 593 for (unsigned i = 0; ; ++i) { 594 assert(i != Blocks.size() && "Loop does not contain BB!"); 595 if (Blocks[i] == BB) { 596 Blocks[i] = Blocks[0]; 597 Blocks[0] = BB; 598 return; 599 } 600 } 601 } 602 603 /// removeBlockFromLoop - This removes the specified basic block from the 604 /// current loop, updating the Blocks as appropriate. This does not update 605 /// the mapping in the LoopInfo class. 606 void removeBlockFromLoop(BlockT *BB) { 607 RemoveFromVector(Blocks, BB); 608 } 609 610 /// verifyLoop - Verify loop structure 611 void verifyLoop() const { 612#ifndef NDEBUG 613 assert (getHeader() && "Loop header is missing"); 614 assert (getLoopPreheader() && "Loop preheader is missing"); 615 assert (getLoopLatch() && "Loop latch is missing"); 616 for (iterator I = SubLoops.begin(), E = SubLoops.end(); I != E; ++I) 617 (*I)->verifyLoop(); 618#endif 619 } 620 621 void print(std::ostream &OS, unsigned Depth = 0) const { 622 OS << std::string(Depth*2, ' ') << "Loop at depth " << getLoopDepth() 623 << " containing: "; 624 625 for (unsigned i = 0; i < getBlocks().size(); ++i) { 626 if (i) OS << ","; 627 BlockT *BB = getBlocks()[i]; 628 WriteAsOperand(OS, BB, false); 629 if (BB == getHeader()) OS << "<header>"; 630 if (BB == getLoopLatch()) OS << "<latch>"; 631 if (isLoopExit(BB)) OS << "<exit>"; 632 } 633 OS << "\n"; 634 635 for (iterator I = begin(), E = end(); I != E; ++I) 636 (*I)->print(OS, Depth+2); 637 } 638 639 void print(std::ostream *O, unsigned Depth = 0) const { 640 if (O) print(*O, Depth); 641 } 642 643 void dump() const { 644 print(cerr); 645 } 646 647protected: 648 friend class LoopInfoBase<BlockT, LoopT>; 649 explicit LoopBase(BlockT *BB) : ParentLoop(0) { 650 Blocks.push_back(BB); 651 } 652}; 653 654class Loop : public LoopBase<BasicBlock, Loop> { 655public: 656 Loop() {} 657private: 658 friend class LoopInfoBase<BasicBlock, Loop>; 659 explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {} 660}; 661 662//===----------------------------------------------------------------------===// 663/// LoopInfo - This class builds and contains all of the top level loop 664/// structures in the specified function. 665/// 666 667template<class BlockT, class LoopT> 668class LoopInfoBase { 669 // BBMap - Mapping of basic blocks to the inner most loop they occur in 670 std::map<BlockT *, LoopT *> BBMap; 671 std::vector<LoopT *> TopLevelLoops; 672 friend class LoopBase<BlockT, LoopT>; 673 674 void operator=(const LoopInfoBase &); // do not implement 675 LoopInfoBase(const LoopInfo &); // do not implement 676public: 677 LoopInfoBase() { } 678 ~LoopInfoBase() { releaseMemory(); } 679 680 void releaseMemory() { 681 for (typename std::vector<LoopT *>::iterator I = 682 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I) 683 delete *I; // Delete all of the loops... 684 685 BBMap.clear(); // Reset internal state of analysis 686 TopLevelLoops.clear(); 687 } 688 689 /// iterator/begin/end - The interface to the top-level loops in the current 690 /// function. 691 /// 692 typedef typename std::vector<LoopT *>::const_iterator iterator; 693 iterator begin() const { return TopLevelLoops.begin(); } 694 iterator end() const { return TopLevelLoops.end(); } 695 bool empty() const { return TopLevelLoops.empty(); } 696 697 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 698 /// block is in no loop (for example the entry node), null is returned. 699 /// 700 LoopT *getLoopFor(const BlockT *BB) const { 701 typename std::map<BlockT *, LoopT *>::const_iterator I= 702 BBMap.find(const_cast<BlockT*>(BB)); 703 return I != BBMap.end() ? I->second : 0; 704 } 705 706 /// operator[] - same as getLoopFor... 707 /// 708 const LoopT *operator[](const BlockT *BB) const { 709 return getLoopFor(BB); 710 } 711 712 /// getLoopDepth - Return the loop nesting level of the specified block. A 713 /// depth of 0 means the block is not inside any loop. 714 /// 715 unsigned getLoopDepth(const BlockT *BB) const { 716 const LoopT *L = getLoopFor(BB); 717 return L ? L->getLoopDepth() : 0; 718 } 719 720 // isLoopHeader - True if the block is a loop header node 721 bool isLoopHeader(BlockT *BB) const { 722 const LoopT *L = getLoopFor(BB); 723 return L && L->getHeader() == BB; 724 } 725 726 /// removeLoop - This removes the specified top-level loop from this loop info 727 /// object. The loop is not deleted, as it will presumably be inserted into 728 /// another loop. 729 LoopT *removeLoop(iterator I) { 730 assert(I != end() && "Cannot remove end iterator!"); 731 LoopT *L = *I; 732 assert(L->getParentLoop() == 0 && "Not a top-level loop!"); 733 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin())); 734 return L; 735 } 736 737 /// changeLoopFor - Change the top-level loop that contains BB to the 738 /// specified loop. This should be used by transformations that restructure 739 /// the loop hierarchy tree. 740 void changeLoopFor(BlockT *BB, LoopT *L) { 741 LoopT *&OldLoop = BBMap[BB]; 742 assert(OldLoop && "Block not in a loop yet!"); 743 OldLoop = L; 744 } 745 746 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 747 /// list with the indicated loop. 748 void changeTopLevelLoop(LoopT *OldLoop, 749 LoopT *NewLoop) { 750 typename std::vector<LoopT *>::iterator I = 751 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop); 752 assert(I != TopLevelLoops.end() && "Old loop not at top level!"); 753 *I = NewLoop; 754 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 && 755 "Loops already embedded into a subloop!"); 756 } 757 758 /// addTopLevelLoop - This adds the specified loop to the collection of 759 /// top-level loops. 760 void addTopLevelLoop(LoopT *New) { 761 assert(New->getParentLoop() == 0 && "Loop already in subloop!"); 762 TopLevelLoops.push_back(New); 763 } 764 765 /// removeBlock - This method completely removes BB from all data structures, 766 /// including all of the Loop objects it is nested in and our mapping from 767 /// BasicBlocks to loops. 768 void removeBlock(BlockT *BB) { 769 typename std::map<BlockT *, LoopT *>::iterator I = BBMap.find(BB); 770 if (I != BBMap.end()) { 771 for (LoopT *L = I->second; L; L = L->getParentLoop()) 772 L->removeBlockFromLoop(BB); 773 774 BBMap.erase(I); 775 } 776 } 777 778 // Internals 779 780 static bool isNotAlreadyContainedIn(const LoopT *SubLoop, 781 const LoopT *ParentLoop) { 782 if (SubLoop == 0) return true; 783 if (SubLoop == ParentLoop) return false; 784 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop); 785 } 786 787 void Calculate(DominatorTreeBase<BlockT> &DT) { 788 BlockT *RootNode = DT.getRootNode()->getBlock(); 789 790 for (df_iterator<BlockT*> NI = df_begin(RootNode), 791 NE = df_end(RootNode); NI != NE; ++NI) 792 if (LoopT *L = ConsiderForLoop(*NI, DT)) 793 TopLevelLoops.push_back(L); 794 } 795 796 LoopT *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) { 797 if (BBMap.find(BB) != BBMap.end()) return 0;// Haven't processed this node? 798 799 std::vector<BlockT *> TodoStack; 800 801 // Scan the predecessors of BB, checking to see if BB dominates any of 802 // them. This identifies backedges which target this node... 803 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 804 for (typename InvBlockTraits::ChildIteratorType I = 805 InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB); 806 I != E; ++I) 807 if (DT.dominates(BB, *I)) // If BB dominates it's predecessor... 808 TodoStack.push_back(*I); 809 810 if (TodoStack.empty()) return 0; // No backedges to this block... 811 812 // Create a new loop to represent this basic block... 813 LoopT *L = new LoopT(BB); 814 BBMap[BB] = L; 815 816 BlockT *EntryBlock = BB->getParent()->begin(); 817 818 while (!TodoStack.empty()) { // Process all the nodes in the loop 819 BlockT *X = TodoStack.back(); 820 TodoStack.pop_back(); 821 822 if (!L->contains(X) && // As of yet unprocessed?? 823 DT.dominates(EntryBlock, X)) { // X is reachable from entry block? 824 // Check to see if this block already belongs to a loop. If this occurs 825 // then we have a case where a loop that is supposed to be a child of 826 // the current loop was processed before the current loop. When this 827 // occurs, this child loop gets added to a part of the current loop, 828 // making it a sibling to the current loop. We have to reparent this 829 // loop. 830 if (LoopT *SubLoop = 831 const_cast<LoopT *>(getLoopFor(X))) 832 if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){ 833 // Remove the subloop from it's current parent... 834 assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L); 835 LoopT *SLP = SubLoop->ParentLoop; // SubLoopParent 836 typename std::vector<LoopT *>::iterator I = 837 std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop); 838 assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?"); 839 SLP->SubLoops.erase(I); // Remove from parent... 840 841 // Add the subloop to THIS loop... 842 SubLoop->ParentLoop = L; 843 L->SubLoops.push_back(SubLoop); 844 } 845 846 // Normal case, add the block to our loop... 847 L->Blocks.push_back(X); 848 849 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 850 851 // Add all of the predecessors of X to the end of the work stack... 852 TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X), 853 InvBlockTraits::child_end(X)); 854 } 855 } 856 857 // If there are any loops nested within this loop, create them now! 858 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 859 E = L->Blocks.end(); I != E; ++I) 860 if (LoopT *NewLoop = ConsiderForLoop(*I, DT)) { 861 L->SubLoops.push_back(NewLoop); 862 NewLoop->ParentLoop = L; 863 } 864 865 // Add the basic blocks that comprise this loop to the BBMap so that this 866 // loop can be found for them. 867 // 868 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 869 E = L->Blocks.end(); I != E; ++I) { 870 typename std::map<BlockT*, LoopT *>::iterator BBMI = BBMap.find(*I); 871 if (BBMI == BBMap.end()) // Not in map yet... 872 BBMap.insert(BBMI, std::make_pair(*I, L)); // Must be at this level 873 } 874 875 // Now that we have a list of all of the child loops of this loop, check to 876 // see if any of them should actually be nested inside of each other. We 877 // can accidentally pull loops our of their parents, so we must make sure to 878 // organize the loop nests correctly now. 879 { 880 std::map<BlockT *, LoopT *> ContainingLoops; 881 for (unsigned i = 0; i != L->SubLoops.size(); ++i) { 882 LoopT *Child = L->SubLoops[i]; 883 assert(Child->getParentLoop() == L && "Not proper child loop?"); 884 885 if (LoopT *ContainingLoop = ContainingLoops[Child->getHeader()]) { 886 // If there is already a loop which contains this loop, move this loop 887 // into the containing loop. 888 MoveSiblingLoopInto(Child, ContainingLoop); 889 --i; // The loop got removed from the SubLoops list. 890 } else { 891 // This is currently considered to be a top-level loop. Check to see 892 // if any of the contained blocks are loop headers for subloops we 893 // have already processed. 894 for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) { 895 LoopT *&BlockLoop = ContainingLoops[Child->Blocks[b]]; 896 if (BlockLoop == 0) { // Child block not processed yet... 897 BlockLoop = Child; 898 } else if (BlockLoop != Child) { 899 LoopT *SubLoop = BlockLoop; 900 // Reparent all of the blocks which used to belong to BlockLoops 901 for (unsigned j = 0, e = SubLoop->Blocks.size(); j != e; ++j) 902 ContainingLoops[SubLoop->Blocks[j]] = Child; 903 904 // There is already a loop which contains this block, that means 905 // that we should reparent the loop which the block is currently 906 // considered to belong to to be a child of this loop. 907 MoveSiblingLoopInto(SubLoop, Child); 908 --i; // We just shrunk the SubLoops list. 909 } 910 } 911 } 912 } 913 } 914 915 return L; 916 } 917 918 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside 919 /// of the NewParent Loop, instead of being a sibling of it. 920 void MoveSiblingLoopInto(LoopT *NewChild, 921 LoopT *NewParent) { 922 LoopT *OldParent = NewChild->getParentLoop(); 923 assert(OldParent && OldParent == NewParent->getParentLoop() && 924 NewChild != NewParent && "Not sibling loops!"); 925 926 // Remove NewChild from being a child of OldParent 927 typename std::vector<LoopT *>::iterator I = 928 std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(), 929 NewChild); 930 assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??"); 931 OldParent->SubLoops.erase(I); // Remove from parent's subloops list 932 NewChild->ParentLoop = 0; 933 934 InsertLoopInto(NewChild, NewParent); 935 } 936 937 /// InsertLoopInto - This inserts loop L into the specified parent loop. If 938 /// the parent loop contains a loop which should contain L, the loop gets 939 /// inserted into L instead. 940 void InsertLoopInto(LoopT *L, LoopT *Parent) { 941 BlockT *LHeader = L->getHeader(); 942 assert(Parent->contains(LHeader) && 943 "This loop should not be inserted here!"); 944 945 // Check to see if it belongs in a child loop... 946 for (unsigned i = 0, e = static_cast<unsigned>(Parent->SubLoops.size()); 947 i != e; ++i) 948 if (Parent->SubLoops[i]->contains(LHeader)) { 949 InsertLoopInto(L, Parent->SubLoops[i]); 950 return; 951 } 952 953 // If not, insert it here! 954 Parent->SubLoops.push_back(L); 955 L->ParentLoop = Parent; 956 } 957 958 // Debugging 959 960 void print(std::ostream &OS, const Module* ) const { 961 for (unsigned i = 0; i < TopLevelLoops.size(); ++i) 962 TopLevelLoops[i]->print(OS); 963 #if 0 964 for (std::map<BasicBlock*, LoopT*>::const_iterator I = BBMap.begin(), 965 E = BBMap.end(); I != E; ++I) 966 OS << "BB '" << I->first->getName() << "' level = " 967 << I->second->getLoopDepth() << "\n"; 968 #endif 969 } 970}; 971 972class LoopInfo : public FunctionPass { 973 LoopInfoBase<BasicBlock, Loop> LI; 974 friend class LoopBase<BasicBlock, Loop>; 975 976 void operator=(const LoopInfo &); // do not implement 977 LoopInfo(const LoopInfo &); // do not implement 978public: 979 static char ID; // Pass identification, replacement for typeid 980 981 LoopInfo() : FunctionPass(&ID) {} 982 983 LoopInfoBase<BasicBlock, Loop>& getBase() { return LI; } 984 985 /// iterator/begin/end - The interface to the top-level loops in the current 986 /// function. 987 /// 988 typedef LoopInfoBase<BasicBlock, Loop>::iterator iterator; 989 inline iterator begin() const { return LI.begin(); } 990 inline iterator end() const { return LI.end(); } 991 bool empty() const { return LI.empty(); } 992 993 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 994 /// block is in no loop (for example the entry node), null is returned. 995 /// 996 inline Loop *getLoopFor(const BasicBlock *BB) const { 997 return LI.getLoopFor(BB); 998 } 999 1000 /// operator[] - same as getLoopFor... 1001 /// 1002 inline const Loop *operator[](const BasicBlock *BB) const { 1003 return LI.getLoopFor(BB); 1004 } 1005 1006 /// getLoopDepth - Return the loop nesting level of the specified block. A 1007 /// depth of 0 means the block is not inside any loop. 1008 /// 1009 inline unsigned getLoopDepth(const BasicBlock *BB) const { 1010 return LI.getLoopDepth(BB); 1011 } 1012 1013 // isLoopHeader - True if the block is a loop header node 1014 inline bool isLoopHeader(BasicBlock *BB) const { 1015 return LI.isLoopHeader(BB); 1016 } 1017 1018 /// runOnFunction - Calculate the natural loop information. 1019 /// 1020 virtual bool runOnFunction(Function &F); 1021 1022 virtual void releaseMemory() { LI.releaseMemory(); } 1023 1024 virtual void print(std::ostream &O, const Module* M = 0) const { 1025 LI.print(O, M); 1026 } 1027 1028 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 1029 1030 /// removeLoop - This removes the specified top-level loop from this loop info 1031 /// object. The loop is not deleted, as it will presumably be inserted into 1032 /// another loop. 1033 inline Loop *removeLoop(iterator I) { return LI.removeLoop(I); } 1034 1035 /// changeLoopFor - Change the top-level loop that contains BB to the 1036 /// specified loop. This should be used by transformations that restructure 1037 /// the loop hierarchy tree. 1038 inline void changeLoopFor(BasicBlock *BB, Loop *L) { 1039 LI.changeLoopFor(BB, L); 1040 } 1041 1042 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 1043 /// list with the indicated loop. 1044 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) { 1045 LI.changeTopLevelLoop(OldLoop, NewLoop); 1046 } 1047 1048 /// addTopLevelLoop - This adds the specified loop to the collection of 1049 /// top-level loops. 1050 inline void addTopLevelLoop(Loop *New) { 1051 LI.addTopLevelLoop(New); 1052 } 1053 1054 /// removeBlock - This method completely removes BB from all data structures, 1055 /// including all of the Loop objects it is nested in and our mapping from 1056 /// BasicBlocks to loops. 1057 void removeBlock(BasicBlock *BB) { 1058 LI.removeBlock(BB); 1059 } 1060 1061 static bool isNotAlreadyContainedIn(const Loop *SubLoop, 1062 const Loop *ParentLoop) { 1063 return 1064 LoopInfoBase<BasicBlock, Loop>::isNotAlreadyContainedIn(SubLoop, 1065 ParentLoop); 1066 } 1067}; 1068 1069 1070// Allow clients to walk the list of nested loops... 1071template <> struct GraphTraits<const Loop*> { 1072 typedef const Loop NodeType; 1073 typedef LoopInfo::iterator ChildIteratorType; 1074 1075 static NodeType *getEntryNode(const Loop *L) { return L; } 1076 static inline ChildIteratorType child_begin(NodeType *N) { 1077 return N->begin(); 1078 } 1079 static inline ChildIteratorType child_end(NodeType *N) { 1080 return N->end(); 1081 } 1082}; 1083 1084template <> struct GraphTraits<Loop*> { 1085 typedef Loop NodeType; 1086 typedef LoopInfo::iterator ChildIteratorType; 1087 1088 static NodeType *getEntryNode(Loop *L) { return L; } 1089 static inline ChildIteratorType child_begin(NodeType *N) { 1090 return N->begin(); 1091 } 1092 static inline ChildIteratorType child_end(NodeType *N) { 1093 return N->end(); 1094 } 1095}; 1096 1097template<class BlockT, class LoopT> 1098void 1099LoopBase<BlockT, LoopT>::addBasicBlockToLoop(BlockT *NewBB, 1100 LoopInfoBase<BlockT, LoopT> &LIB) { 1101 assert((Blocks.empty() || LIB[getHeader()] == this) && 1102 "Incorrect LI specified for this loop!"); 1103 assert(NewBB && "Cannot add a null basic block to the loop!"); 1104 assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!"); 1105 1106 LoopT *L = static_cast<LoopT *>(this); 1107 1108 // Add the loop mapping to the LoopInfo object... 1109 LIB.BBMap[NewBB] = L; 1110 1111 // Add the basic block to this loop and all parent loops... 1112 while (L) { 1113 L->Blocks.push_back(NewBB); 1114 L = L->getParentLoop(); 1115 } 1116} 1117 1118} // End llvm namespace 1119 1120#endif 1121