LoopInfo.h revision 6c3534c5aa6b1d34b277dfaca3af86ac41e53f0e
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 /// The IndVarSimplify pass transforms loops to have a canonical induction 355 /// variable. 356 /// 357 inline PHINode *getCanonicalInductionVariable() const { 358 BlockT *H = getHeader(); 359 360 BlockT *Incoming = 0, *Backedge = 0; 361 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 362 typename InvBlockTraits::ChildIteratorType PI = 363 InvBlockTraits::child_begin(H); 364 assert(PI != InvBlockTraits::child_end(H) && 365 "Loop must have at least one backedge!"); 366 Backedge = *PI++; 367 if (PI == InvBlockTraits::child_end(H)) return 0; // dead loop 368 Incoming = *PI++; 369 if (PI != InvBlockTraits::child_end(H)) return 0; // multiple backedges? 370 371 if (contains(Incoming)) { 372 if (contains(Backedge)) 373 return 0; 374 std::swap(Incoming, Backedge); 375 } else if (!contains(Backedge)) 376 return 0; 377 378 // Loop over all of the PHI nodes, looking for a canonical indvar. 379 for (typename BlockT::iterator I = H->begin(); isa<PHINode>(I); ++I) { 380 PHINode *PN = cast<PHINode>(I); 381 if (ConstantInt *CI = 382 dyn_cast<ConstantInt>(PN->getIncomingValueForBlock(Incoming))) 383 if (CI->isNullValue()) 384 if (Instruction *Inc = 385 dyn_cast<Instruction>(PN->getIncomingValueForBlock(Backedge))) 386 if (Inc->getOpcode() == Instruction::Add && 387 Inc->getOperand(0) == PN) 388 if (ConstantInt *CI = dyn_cast<ConstantInt>(Inc->getOperand(1))) 389 if (CI->equalsInt(1)) 390 return PN; 391 } 392 return 0; 393 } 394 395 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds 396 /// the canonical induction variable value for the "next" iteration of the 397 /// loop. This always succeeds if getCanonicalInductionVariable succeeds. 398 /// 399 inline Instruction *getCanonicalInductionVariableIncrement() const { 400 if (PHINode *PN = getCanonicalInductionVariable()) { 401 bool P1InLoop = contains(PN->getIncomingBlock(1)); 402 return cast<Instruction>(PN->getIncomingValue(P1InLoop)); 403 } 404 return 0; 405 } 406 407 /// getTripCount - Return a loop-invariant LLVM value indicating the number of 408 /// times the loop will be executed. Note that this means that the backedge 409 /// of the loop executes N-1 times. If the trip-count cannot be determined, 410 /// this returns null. 411 /// 412 /// The IndVarSimplify pass transforms loops to have a form that this 413 /// function easily understands. 414 /// 415 inline Value *getTripCount() const { 416 // Canonical loops will end with a 'cmp ne I, V', where I is the incremented 417 // canonical induction variable and V is the trip count of the loop. 418 Instruction *Inc = getCanonicalInductionVariableIncrement(); 419 if (Inc == 0) return 0; 420 PHINode *IV = cast<PHINode>(Inc->getOperand(0)); 421 422 BlockT *BackedgeBlock = 423 IV->getIncomingBlock(contains(IV->getIncomingBlock(1))); 424 425 if (BranchInst *BI = dyn_cast<BranchInst>(BackedgeBlock->getTerminator())) 426 if (BI->isConditional()) { 427 if (ICmpInst *ICI = dyn_cast<ICmpInst>(BI->getCondition())) { 428 if (ICI->getOperand(0) == Inc) { 429 if (BI->getSuccessor(0) == getHeader()) { 430 if (ICI->getPredicate() == ICmpInst::ICMP_NE) 431 return ICI->getOperand(1); 432 } else if (ICI->getPredicate() == ICmpInst::ICMP_EQ) { 433 return ICI->getOperand(1); 434 } 435 } 436 } 437 } 438 439 return 0; 440 } 441 442 /// getSmallConstantTripCount - Returns the trip count of this loop as a 443 /// normal unsigned value, if possible. Returns 0 if the trip count is unknown 444 /// of not constant. Will also return 0 if the trip count is very large 445 /// (>= 2^32) 446 inline unsigned getSmallConstantTripCount() const { 447 Value* TripCount = this->getTripCount(); 448 if (TripCount) { 449 if (ConstantInt *TripCountC = dyn_cast<ConstantInt>(TripCount)) { 450 // Guard against huge trip counts. 451 if (TripCountC->getValue().getActiveBits() <= 32) { 452 return (unsigned)TripCountC->getZExtValue(); 453 } 454 } 455 } 456 return 0; 457 } 458 459 /// getSmallConstantTripMultiple - Returns the largest constant divisor of the 460 /// trip count of this loop as a normal unsigned value, if possible. This 461 /// means that the actual trip count is always a multiple of the returned 462 /// value (don't forget the trip count could very well be zero as well!). 463 /// 464 /// Returns 1 if the trip count is unknown or not guaranteed to be the 465 /// multiple of a constant (which is also the case if the trip count is simply 466 /// constant, use getSmallConstantTripCount for that case), Will also return 1 467 /// if the trip count is very large (>= 2^32). 468 inline unsigned getSmallConstantTripMultiple() const { 469 Value* TripCount = this->getTripCount(); 470 // This will hold the ConstantInt result, if any 471 ConstantInt *Result = NULL; 472 if (TripCount) { 473 // See if the trip count is constant itself 474 Result = dyn_cast<ConstantInt>(TripCount); 475 // if not, see if it is a multiplication 476 if (!Result) 477 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(TripCount)) { 478 switch (BO->getOpcode()) { 479 case BinaryOperator::Mul: 480 Result = dyn_cast<ConstantInt>(BO->getOperand(1)); 481 break; 482 default: 483 break; 484 } 485 } 486 } 487 // Guard against huge trip counts. 488 if (Result && Result->getValue().getActiveBits() <= 32) { 489 return (unsigned)Result->getZExtValue(); 490 } else { 491 return 1; 492 } 493 } 494 495 /// isLCSSAForm - Return true if the Loop is in LCSSA form 496 inline bool isLCSSAForm() const { 497 // Sort the blocks vector so that we can use binary search to do quick 498 // lookups. 499 SmallPtrSet<BlockT*, 16> LoopBBs(block_begin(), block_end()); 500 501 for (block_iterator BI = block_begin(), E = block_end(); BI != E; ++BI) { 502 BlockT *BB = *BI; 503 for (typename BlockT::iterator I = BB->begin(), E = BB->end(); I != E;++I) 504 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E; 505 ++UI) { 506 BlockT *UserBB = cast<Instruction>(*UI)->getParent(); 507 if (PHINode *P = dyn_cast<PHINode>(*UI)) { 508 UserBB = P->getIncomingBlock(UI); 509 } 510 511 // Check the current block, as a fast-path. Most values are used in 512 // the same block they are defined in. 513 if (UserBB != BB && !LoopBBs.count(UserBB)) 514 return false; 515 } 516 } 517 518 return true; 519 } 520 521 //===--------------------------------------------------------------------===// 522 // APIs for updating loop information after changing the CFG 523 // 524 525 /// addBasicBlockToLoop - This method is used by other analyses to update loop 526 /// information. NewBB is set to be a new member of the current loop. 527 /// Because of this, it is added as a member of all parent loops, and is added 528 /// to the specified LoopInfo object as being in the current basic block. It 529 /// is not valid to replace the loop header with this method. 530 /// 531 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT> &LI); 532 533 /// replaceChildLoopWith - This is used when splitting loops up. It replaces 534 /// the OldChild entry in our children list with NewChild, and updates the 535 /// parent pointer of OldChild to be null and the NewChild to be this loop. 536 /// This updates the loop depth of the new child. 537 void replaceChildLoopWith(LoopBase<BlockT> *OldChild, 538 LoopBase<BlockT> *NewChild) { 539 assert(OldChild->ParentLoop == this && "This loop is already broken!"); 540 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 541 typename std::vector<LoopBase<BlockT>*>::iterator I = 542 std::find(SubLoops.begin(), SubLoops.end(), OldChild); 543 assert(I != SubLoops.end() && "OldChild not in loop!"); 544 *I = NewChild; 545 OldChild->ParentLoop = 0; 546 NewChild->ParentLoop = this; 547 } 548 549 /// addChildLoop - Add the specified loop to be a child of this loop. This 550 /// updates the loop depth of the new child. 551 /// 552 void addChildLoop(LoopBase<BlockT> *NewChild) { 553 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 554 NewChild->ParentLoop = this; 555 SubLoops.push_back(NewChild); 556 } 557 558 /// removeChildLoop - This removes the specified child from being a subloop of 559 /// this loop. The loop is not deleted, as it will presumably be inserted 560 /// into another loop. 561 LoopBase<BlockT> *removeChildLoop(iterator I) { 562 assert(I != SubLoops.end() && "Cannot remove end iterator!"); 563 LoopBase<BlockT> *Child = *I; 564 assert(Child->ParentLoop == this && "Child is not a child of this loop!"); 565 SubLoops.erase(SubLoops.begin()+(I-begin())); 566 Child->ParentLoop = 0; 567 return Child; 568 } 569 570 /// addBlockEntry - This adds a basic block directly to the basic block list. 571 /// This should only be used by transformations that create new loops. Other 572 /// transformations should use addBasicBlockToLoop. 573 void addBlockEntry(BlockT *BB) { 574 Blocks.push_back(BB); 575 } 576 577 /// moveToHeader - This method is used to move BB (which must be part of this 578 /// loop) to be the loop header of the loop (the block that dominates all 579 /// others). 580 void moveToHeader(BlockT *BB) { 581 if (Blocks[0] == BB) return; 582 for (unsigned i = 0; ; ++i) { 583 assert(i != Blocks.size() && "Loop does not contain BB!"); 584 if (Blocks[i] == BB) { 585 Blocks[i] = Blocks[0]; 586 Blocks[0] = BB; 587 return; 588 } 589 } 590 } 591 592 /// removeBlockFromLoop - This removes the specified basic block from the 593 /// current loop, updating the Blocks as appropriate. This does not update 594 /// the mapping in the LoopInfo class. 595 void removeBlockFromLoop(BlockT *BB) { 596 RemoveFromVector(Blocks, BB); 597 } 598 599 /// verifyLoop - Verify loop structure 600 void verifyLoop() const { 601#ifndef NDEBUG 602 assert (getHeader() && "Loop header is missing"); 603 assert (getLoopPreheader() && "Loop preheader is missing"); 604 assert (getLoopLatch() && "Loop latch is missing"); 605 for (iterator I = SubLoops.begin(), E = SubLoops.end(); I != E; ++I) 606 (*I)->verifyLoop(); 607#endif 608 } 609 610 void print(std::ostream &OS, unsigned Depth = 0) const { 611 OS << std::string(Depth*2, ' ') << "Loop at depth " << getLoopDepth() 612 << " containing: "; 613 614 for (unsigned i = 0; i < getBlocks().size(); ++i) { 615 if (i) OS << ","; 616 BlockT *BB = getBlocks()[i]; 617 WriteAsOperand(OS, BB, false); 618 if (BB == getHeader()) OS << "<header>"; 619 if (BB == getLoopLatch()) OS << "<latch>"; 620 if (isLoopExit(BB)) OS << "<exit>"; 621 } 622 OS << "\n"; 623 624 for (iterator I = begin(), E = end(); I != E; ++I) 625 (*I)->print(OS, Depth+2); 626 } 627 628 void print(std::ostream *O, unsigned Depth = 0) const { 629 if (O) print(*O, Depth); 630 } 631 632 void dump() const { 633 print(cerr); 634 } 635 636private: 637 friend class LoopInfoBase<BlockT>; 638 explicit LoopBase(BlockT *BB) : ParentLoop(0) { 639 Blocks.push_back(BB); 640 } 641}; 642 643 644//===----------------------------------------------------------------------===// 645/// LoopInfo - This class builds and contains all of the top level loop 646/// structures in the specified function. 647/// 648 649template<class BlockT> 650class LoopInfoBase { 651 // BBMap - Mapping of basic blocks to the inner most loop they occur in 652 std::map<BlockT*, LoopBase<BlockT>*> BBMap; 653 std::vector<LoopBase<BlockT>*> TopLevelLoops; 654 friend class LoopBase<BlockT>; 655 656public: 657 LoopInfoBase() { } 658 ~LoopInfoBase() { releaseMemory(); } 659 660 void releaseMemory() { 661 for (typename std::vector<LoopBase<BlockT>* >::iterator I = 662 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I) 663 delete *I; // Delete all of the loops... 664 665 BBMap.clear(); // Reset internal state of analysis 666 TopLevelLoops.clear(); 667 } 668 669 /// iterator/begin/end - The interface to the top-level loops in the current 670 /// function. 671 /// 672 typedef typename std::vector<LoopBase<BlockT>*>::const_iterator iterator; 673 iterator begin() const { return TopLevelLoops.begin(); } 674 iterator end() const { return TopLevelLoops.end(); } 675 bool empty() const { return TopLevelLoops.empty(); } 676 677 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 678 /// block is in no loop (for example the entry node), null is returned. 679 /// 680 LoopBase<BlockT> *getLoopFor(const BlockT *BB) const { 681 typename std::map<BlockT *, LoopBase<BlockT>*>::const_iterator I= 682 BBMap.find(const_cast<BlockT*>(BB)); 683 return I != BBMap.end() ? I->second : 0; 684 } 685 686 /// operator[] - same as getLoopFor... 687 /// 688 const LoopBase<BlockT> *operator[](const BlockT *BB) const { 689 return getLoopFor(BB); 690 } 691 692 /// getLoopDepth - Return the loop nesting level of the specified block. A 693 /// depth of 0 means the block is not inside any loop. 694 /// 695 unsigned getLoopDepth(const BlockT *BB) const { 696 const LoopBase<BlockT> *L = getLoopFor(BB); 697 return L ? L->getLoopDepth() : 0; 698 } 699 700 // isLoopHeader - True if the block is a loop header node 701 bool isLoopHeader(BlockT *BB) const { 702 const LoopBase<BlockT> *L = getLoopFor(BB); 703 return L && L->getHeader() == BB; 704 } 705 706 /// removeLoop - This removes the specified top-level loop from this loop info 707 /// object. The loop is not deleted, as it will presumably be inserted into 708 /// another loop. 709 LoopBase<BlockT> *removeLoop(iterator I) { 710 assert(I != end() && "Cannot remove end iterator!"); 711 LoopBase<BlockT> *L = *I; 712 assert(L->getParentLoop() == 0 && "Not a top-level loop!"); 713 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin())); 714 return L; 715 } 716 717 /// changeLoopFor - Change the top-level loop that contains BB to the 718 /// specified loop. This should be used by transformations that restructure 719 /// the loop hierarchy tree. 720 void changeLoopFor(BlockT *BB, LoopBase<BlockT> *L) { 721 LoopBase<BlockT> *&OldLoop = BBMap[BB]; 722 assert(OldLoop && "Block not in a loop yet!"); 723 OldLoop = L; 724 } 725 726 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 727 /// list with the indicated loop. 728 void changeTopLevelLoop(LoopBase<BlockT> *OldLoop, 729 LoopBase<BlockT> *NewLoop) { 730 typename std::vector<LoopBase<BlockT>*>::iterator I = 731 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop); 732 assert(I != TopLevelLoops.end() && "Old loop not at top level!"); 733 *I = NewLoop; 734 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 && 735 "Loops already embedded into a subloop!"); 736 } 737 738 /// addTopLevelLoop - This adds the specified loop to the collection of 739 /// top-level loops. 740 void addTopLevelLoop(LoopBase<BlockT> *New) { 741 assert(New->getParentLoop() == 0 && "Loop already in subloop!"); 742 TopLevelLoops.push_back(New); 743 } 744 745 /// removeBlock - This method completely removes BB from all data structures, 746 /// including all of the Loop objects it is nested in and our mapping from 747 /// BasicBlocks to loops. 748 void removeBlock(BlockT *BB) { 749 typename std::map<BlockT *, LoopBase<BlockT>*>::iterator I = BBMap.find(BB); 750 if (I != BBMap.end()) { 751 for (LoopBase<BlockT> *L = I->second; L; L = L->getParentLoop()) 752 L->removeBlockFromLoop(BB); 753 754 BBMap.erase(I); 755 } 756 } 757 758 // Internals 759 760 static bool isNotAlreadyContainedIn(const LoopBase<BlockT> *SubLoop, 761 const LoopBase<BlockT> *ParentLoop) { 762 if (SubLoop == 0) return true; 763 if (SubLoop == ParentLoop) return false; 764 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop); 765 } 766 767 void Calculate(DominatorTreeBase<BlockT> &DT) { 768 BlockT *RootNode = DT.getRootNode()->getBlock(); 769 770 for (df_iterator<BlockT*> NI = df_begin(RootNode), 771 NE = df_end(RootNode); NI != NE; ++NI) 772 if (LoopBase<BlockT> *L = ConsiderForLoop(*NI, DT)) 773 TopLevelLoops.push_back(L); 774 } 775 776 LoopBase<BlockT> *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) { 777 if (BBMap.find(BB) != BBMap.end()) return 0;// Haven't processed this node? 778 779 std::vector<BlockT *> TodoStack; 780 781 // Scan the predecessors of BB, checking to see if BB dominates any of 782 // them. This identifies backedges which target this node... 783 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 784 for (typename InvBlockTraits::ChildIteratorType I = 785 InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB); 786 I != E; ++I) 787 if (DT.dominates(BB, *I)) // If BB dominates it's predecessor... 788 TodoStack.push_back(*I); 789 790 if (TodoStack.empty()) return 0; // No backedges to this block... 791 792 // Create a new loop to represent this basic block... 793 LoopBase<BlockT> *L = new LoopBase<BlockT>(BB); 794 BBMap[BB] = L; 795 796 BlockT *EntryBlock = BB->getParent()->begin(); 797 798 while (!TodoStack.empty()) { // Process all the nodes in the loop 799 BlockT *X = TodoStack.back(); 800 TodoStack.pop_back(); 801 802 if (!L->contains(X) && // As of yet unprocessed?? 803 DT.dominates(EntryBlock, X)) { // X is reachable from entry block? 804 // Check to see if this block already belongs to a loop. If this occurs 805 // then we have a case where a loop that is supposed to be a child of 806 // the current loop was processed before the current loop. When this 807 // occurs, this child loop gets added to a part of the current loop, 808 // making it a sibling to the current loop. We have to reparent this 809 // loop. 810 if (LoopBase<BlockT> *SubLoop = 811 const_cast<LoopBase<BlockT>*>(getLoopFor(X))) 812 if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){ 813 // Remove the subloop from it's current parent... 814 assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L); 815 LoopBase<BlockT> *SLP = SubLoop->ParentLoop; // SubLoopParent 816 typename std::vector<LoopBase<BlockT>*>::iterator I = 817 std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop); 818 assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?"); 819 SLP->SubLoops.erase(I); // Remove from parent... 820 821 // Add the subloop to THIS loop... 822 SubLoop->ParentLoop = L; 823 L->SubLoops.push_back(SubLoop); 824 } 825 826 // Normal case, add the block to our loop... 827 L->Blocks.push_back(X); 828 829 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 830 831 // Add all of the predecessors of X to the end of the work stack... 832 TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X), 833 InvBlockTraits::child_end(X)); 834 } 835 } 836 837 // If there are any loops nested within this loop, create them now! 838 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 839 E = L->Blocks.end(); I != E; ++I) 840 if (LoopBase<BlockT> *NewLoop = ConsiderForLoop(*I, DT)) { 841 L->SubLoops.push_back(NewLoop); 842 NewLoop->ParentLoop = L; 843 } 844 845 // Add the basic blocks that comprise this loop to the BBMap so that this 846 // loop can be found for them. 847 // 848 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 849 E = L->Blocks.end(); I != E; ++I) { 850 typename std::map<BlockT*, LoopBase<BlockT>*>::iterator BBMI = 851 BBMap.find(*I); 852 if (BBMI == BBMap.end()) // Not in map yet... 853 BBMap.insert(BBMI, std::make_pair(*I, L)); // Must be at this level 854 } 855 856 // Now that we have a list of all of the child loops of this loop, check to 857 // see if any of them should actually be nested inside of each other. We 858 // can accidentally pull loops our of their parents, so we must make sure to 859 // organize the loop nests correctly now. 860 { 861 std::map<BlockT*, LoopBase<BlockT>*> ContainingLoops; 862 for (unsigned i = 0; i != L->SubLoops.size(); ++i) { 863 LoopBase<BlockT> *Child = L->SubLoops[i]; 864 assert(Child->getParentLoop() == L && "Not proper child loop?"); 865 866 if (LoopBase<BlockT> *ContainingLoop = 867 ContainingLoops[Child->getHeader()]) { 868 // If there is already a loop which contains this loop, move this loop 869 // into the containing loop. 870 MoveSiblingLoopInto(Child, ContainingLoop); 871 --i; // The loop got removed from the SubLoops list. 872 } else { 873 // This is currently considered to be a top-level loop. Check to see 874 // if any of the contained blocks are loop headers for subloops we 875 // have already processed. 876 for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) { 877 LoopBase<BlockT> *&BlockLoop = ContainingLoops[Child->Blocks[b]]; 878 if (BlockLoop == 0) { // Child block not processed yet... 879 BlockLoop = Child; 880 } else if (BlockLoop != Child) { 881 LoopBase<BlockT> *SubLoop = BlockLoop; 882 // Reparent all of the blocks which used to belong to BlockLoops 883 for (unsigned j = 0, e = SubLoop->Blocks.size(); j != e; ++j) 884 ContainingLoops[SubLoop->Blocks[j]] = Child; 885 886 // There is already a loop which contains this block, that means 887 // that we should reparent the loop which the block is currently 888 // considered to belong to to be a child of this loop. 889 MoveSiblingLoopInto(SubLoop, Child); 890 --i; // We just shrunk the SubLoops list. 891 } 892 } 893 } 894 } 895 } 896 897 return L; 898 } 899 900 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside 901 /// of the NewParent Loop, instead of being a sibling of it. 902 void MoveSiblingLoopInto(LoopBase<BlockT> *NewChild, 903 LoopBase<BlockT> *NewParent) { 904 LoopBase<BlockT> *OldParent = NewChild->getParentLoop(); 905 assert(OldParent && OldParent == NewParent->getParentLoop() && 906 NewChild != NewParent && "Not sibling loops!"); 907 908 // Remove NewChild from being a child of OldParent 909 typename std::vector<LoopBase<BlockT>*>::iterator I = 910 std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(), 911 NewChild); 912 assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??"); 913 OldParent->SubLoops.erase(I); // Remove from parent's subloops list 914 NewChild->ParentLoop = 0; 915 916 InsertLoopInto(NewChild, NewParent); 917 } 918 919 /// InsertLoopInto - This inserts loop L into the specified parent loop. If 920 /// the parent loop contains a loop which should contain L, the loop gets 921 /// inserted into L instead. 922 void InsertLoopInto(LoopBase<BlockT> *L, LoopBase<BlockT> *Parent) { 923 BlockT *LHeader = L->getHeader(); 924 assert(Parent->contains(LHeader) && 925 "This loop should not be inserted here!"); 926 927 // Check to see if it belongs in a child loop... 928 for (unsigned i = 0, e = static_cast<unsigned>(Parent->SubLoops.size()); 929 i != e; ++i) 930 if (Parent->SubLoops[i]->contains(LHeader)) { 931 InsertLoopInto(L, Parent->SubLoops[i]); 932 return; 933 } 934 935 // If not, insert it here! 936 Parent->SubLoops.push_back(L); 937 L->ParentLoop = Parent; 938 } 939 940 // Debugging 941 942 void print(std::ostream &OS, const Module* ) const { 943 for (unsigned i = 0; i < TopLevelLoops.size(); ++i) 944 TopLevelLoops[i]->print(OS); 945 #if 0 946 for (std::map<BasicBlock*, Loop*>::const_iterator I = BBMap.begin(), 947 E = BBMap.end(); I != E; ++I) 948 OS << "BB '" << I->first->getName() << "' level = " 949 << I->second->getLoopDepth() << "\n"; 950 #endif 951 } 952}; 953 954class LoopInfo : public FunctionPass { 955 LoopInfoBase<BasicBlock>* LI; 956 friend class LoopBase<BasicBlock>; 957 958public: 959 static char ID; // Pass identification, replacement for typeid 960 961 LoopInfo() : FunctionPass(&ID) { 962 LI = new LoopInfoBase<BasicBlock>(); 963 } 964 965 ~LoopInfo() { delete LI; } 966 967 LoopInfoBase<BasicBlock>& getBase() { return *LI; } 968 969 /// iterator/begin/end - The interface to the top-level loops in the current 970 /// function. 971 /// 972 typedef std::vector<Loop*>::const_iterator iterator; 973 inline iterator begin() const { return LI->begin(); } 974 inline iterator end() const { return LI->end(); } 975 bool empty() const { return LI->empty(); } 976 977 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 978 /// block is in no loop (for example the entry node), null is returned. 979 /// 980 inline Loop *getLoopFor(const BasicBlock *BB) const { 981 return LI->getLoopFor(BB); 982 } 983 984 /// operator[] - same as getLoopFor... 985 /// 986 inline const Loop *operator[](const BasicBlock *BB) const { 987 return LI->getLoopFor(BB); 988 } 989 990 /// getLoopDepth - Return the loop nesting level of the specified block. A 991 /// depth of 0 means the block is not inside any loop. 992 /// 993 inline unsigned getLoopDepth(const BasicBlock *BB) const { 994 return LI->getLoopDepth(BB); 995 } 996 997 // isLoopHeader - True if the block is a loop header node 998 inline bool isLoopHeader(BasicBlock *BB) const { 999 return LI->isLoopHeader(BB); 1000 } 1001 1002 /// runOnFunction - Calculate the natural loop information. 1003 /// 1004 virtual bool runOnFunction(Function &F); 1005 1006 virtual void releaseMemory() { LI->releaseMemory(); } 1007 1008 virtual void print(std::ostream &O, const Module* M = 0) const { 1009 if (O) LI->print(O, M); 1010 } 1011 1012 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 1013 1014 /// removeLoop - This removes the specified top-level loop from this loop info 1015 /// object. The loop is not deleted, as it will presumably be inserted into 1016 /// another loop. 1017 inline Loop *removeLoop(iterator I) { return LI->removeLoop(I); } 1018 1019 /// changeLoopFor - Change the top-level loop that contains BB to the 1020 /// specified loop. This should be used by transformations that restructure 1021 /// the loop hierarchy tree. 1022 inline void changeLoopFor(BasicBlock *BB, Loop *L) { 1023 LI->changeLoopFor(BB, L); 1024 } 1025 1026 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 1027 /// list with the indicated loop. 1028 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) { 1029 LI->changeTopLevelLoop(OldLoop, NewLoop); 1030 } 1031 1032 /// addTopLevelLoop - This adds the specified loop to the collection of 1033 /// top-level loops. 1034 inline void addTopLevelLoop(Loop *New) { 1035 LI->addTopLevelLoop(New); 1036 } 1037 1038 /// removeBlock - This method completely removes BB from all data structures, 1039 /// including all of the Loop objects it is nested in and our mapping from 1040 /// BasicBlocks to loops. 1041 void removeBlock(BasicBlock *BB) { 1042 LI->removeBlock(BB); 1043 } 1044}; 1045 1046 1047// Allow clients to walk the list of nested loops... 1048template <> struct GraphTraits<const Loop*> { 1049 typedef const Loop NodeType; 1050 typedef std::vector<Loop*>::const_iterator ChildIteratorType; 1051 1052 static NodeType *getEntryNode(const Loop *L) { return L; } 1053 static inline ChildIteratorType child_begin(NodeType *N) { 1054 return N->begin(); 1055 } 1056 static inline ChildIteratorType child_end(NodeType *N) { 1057 return N->end(); 1058 } 1059}; 1060 1061template <> struct GraphTraits<Loop*> { 1062 typedef Loop NodeType; 1063 typedef std::vector<Loop*>::const_iterator ChildIteratorType; 1064 1065 static NodeType *getEntryNode(Loop *L) { return L; } 1066 static inline ChildIteratorType child_begin(NodeType *N) { 1067 return N->begin(); 1068 } 1069 static inline ChildIteratorType child_end(NodeType *N) { 1070 return N->end(); 1071 } 1072}; 1073 1074template<class BlockT> 1075void LoopBase<BlockT>::addBasicBlockToLoop(BlockT *NewBB, 1076 LoopInfoBase<BlockT> &LIB) { 1077 assert((Blocks.empty() || LIB[getHeader()] == this) && 1078 "Incorrect LI specified for this loop!"); 1079 assert(NewBB && "Cannot add a null basic block to the loop!"); 1080 assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!"); 1081 1082 // Add the loop mapping to the LoopInfo object... 1083 LIB.BBMap[NewBB] = this; 1084 1085 // Add the basic block to this loop and all parent loops... 1086 LoopBase<BlockT> *L = this; 1087 while (L) { 1088 L->Blocks.push_back(NewBB); 1089 L = L->getParentLoop(); 1090 } 1091} 1092 1093} // End llvm namespace 1094 1095#endif 1096