LoopInfo.h revision 60f422f894ae9aff2f508f34733be36f5a0ed20a
1//===- llvm/Analysis/LoopInfo.h - Natural Loop Calculator -------*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file defines the LoopInfo class that is used to identify natural loops 11// and determine the loop depth of various nodes of the CFG. A natural loop 12// has exactly one entry-point, which is called the header. Note that natural 13// loops may actually be several loops that share the same header node. 14// 15// This analysis calculates the nesting structure of loops in a function. For 16// each natural loop identified, this analysis identifies natural loops 17// contained entirely within the loop and the basic blocks the make up the loop. 18// 19// It can calculate on the fly various bits of information, for example: 20// 21// * whether there is a preheader for the loop 22// * the number of back edges to the header 23// * whether or not a particular block branches out of the loop 24// * the successor blocks of the loop 25// * the loop depth 26// * the trip count 27// * etc... 28// 29//===----------------------------------------------------------------------===// 30 31#ifndef LLVM_ANALYSIS_LOOP_INFO_H 32#define LLVM_ANALYSIS_LOOP_INFO_H 33 34#include "llvm/Pass.h" 35#include "llvm/ADT/DepthFirstIterator.h" 36#include "llvm/ADT/GraphTraits.h" 37#include "llvm/ADT/SmallVector.h" 38#include "llvm/Analysis/Dominators.h" 39#include "llvm/Support/CFG.h" 40#include "llvm/Support/raw_ostream.h" 41#include <algorithm> 42 43namespace llvm { 44 45template<typename T> 46static void RemoveFromVector(std::vector<T*> &V, T *N) { 47 typename std::vector<T*>::iterator I = std::find(V.begin(), V.end(), N); 48 assert(I != V.end() && "N is not in this list!"); 49 V.erase(I); 50} 51 52class DominatorTree; 53class LoopInfo; 54class Loop; 55template<class N, class M> class LoopInfoBase; 56template<class N, class M> class LoopBase; 57 58//===----------------------------------------------------------------------===// 59/// LoopBase class - Instances of this class are used to represent loops that 60/// are detected in the flow graph 61/// 62template<class BlockT, class LoopT> 63class LoopBase { 64 LoopT *ParentLoop; 65 // SubLoops - Loops contained entirely within this one. 66 std::vector<LoopT *> SubLoops; 67 68 // Blocks - The list of blocks in this loop. First entry is the header node. 69 std::vector<BlockT*> Blocks; 70 71 // DO NOT IMPLEMENT 72 LoopBase(const LoopBase<BlockT, LoopT> &); 73 // DO NOT IMPLEMENT 74 const LoopBase<BlockT, LoopT>&operator=(const LoopBase<BlockT, LoopT> &); 75public: 76 /// Loop ctor - This creates an empty loop. 77 LoopBase() : ParentLoop(0) {} 78 ~LoopBase() { 79 for (size_t i = 0, e = SubLoops.size(); i != e; ++i) 80 delete SubLoops[i]; 81 } 82 83 /// getLoopDepth - Return the nesting level of this loop. An outer-most 84 /// loop has depth 1, for consistency with loop depth values used for basic 85 /// blocks, where depth 0 is used for blocks not inside any loops. 86 unsigned getLoopDepth() const { 87 unsigned D = 1; 88 for (const LoopT *CurLoop = ParentLoop; CurLoop; 89 CurLoop = CurLoop->ParentLoop) 90 ++D; 91 return D; 92 } 93 BlockT *getHeader() const { return Blocks.front(); } 94 LoopT *getParentLoop() const { return ParentLoop; } 95 96 /// contains - Return true if the specified loop is contained within in 97 /// this loop. 98 /// 99 bool contains(const LoopT *L) const { 100 if (L == this) return true; 101 if (L == 0) return false; 102 return contains(L->getParentLoop()); 103 } 104 105 /// contains - Return true if the specified basic block is in this loop. 106 /// 107 bool contains(const BlockT *BB) const { 108 return std::find(block_begin(), block_end(), BB) != block_end(); 109 } 110 111 /// contains - Return true if the specified instruction is in this loop. 112 /// 113 template<class InstT> 114 bool contains(const InstT *Inst) const { 115 return contains(Inst->getParent()); 116 } 117 118 /// iterator/begin/end - Return the loops contained entirely within this loop. 119 /// 120 const std::vector<LoopT *> &getSubLoops() const { return SubLoops; } 121 typedef typename std::vector<LoopT *>::const_iterator iterator; 122 iterator begin() const { return SubLoops.begin(); } 123 iterator end() const { return SubLoops.end(); } 124 bool empty() const { return SubLoops.empty(); } 125 126 /// getBlocks - Get a list of the basic blocks which make up this loop. 127 /// 128 const std::vector<BlockT*> &getBlocks() const { return Blocks; } 129 typedef typename std::vector<BlockT*>::const_iterator block_iterator; 130 block_iterator block_begin() const { return Blocks.begin(); } 131 block_iterator block_end() const { return Blocks.end(); } 132 133 /// isLoopExiting - True if terminator in the block can branch to another 134 /// block that is outside of the current loop. 135 /// 136 bool isLoopExiting(const BlockT *BB) const { 137 typedef GraphTraits<BlockT*> BlockTraits; 138 for (typename BlockTraits::ChildIteratorType SI = 139 BlockTraits::child_begin(const_cast<BlockT*>(BB)), 140 SE = BlockTraits::child_end(const_cast<BlockT*>(BB)); SI != SE; ++SI) { 141 if (!contains(*SI)) 142 return true; 143 } 144 return false; 145 } 146 147 /// getNumBackEdges - Calculate the number of back edges to the loop header 148 /// 149 unsigned getNumBackEdges() const { 150 unsigned NumBackEdges = 0; 151 BlockT *H = getHeader(); 152 153 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 154 for (typename InvBlockTraits::ChildIteratorType I = 155 InvBlockTraits::child_begin(const_cast<BlockT*>(H)), 156 E = InvBlockTraits::child_end(const_cast<BlockT*>(H)); I != E; ++I) 157 if (contains(*I)) 158 ++NumBackEdges; 159 160 return NumBackEdges; 161 } 162 163 //===--------------------------------------------------------------------===// 164 // APIs for simple analysis of the loop. 165 // 166 // Note that all of these methods can fail on general loops (ie, there may not 167 // be a preheader, etc). For best success, the loop simplification and 168 // induction variable canonicalization pass should be used to normalize loops 169 // for easy analysis. These methods assume canonical loops. 170 171 /// getExitingBlocks - Return all blocks inside the loop that have successors 172 /// outside of the loop. These are the blocks _inside of the current loop_ 173 /// which branch out. The returned list is always unique. 174 /// 175 void getExitingBlocks(SmallVectorImpl<BlockT *> &ExitingBlocks) const { 176 // Sort the blocks vector so that we can use binary search to do quick 177 // lookups. 178 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 179 std::sort(LoopBBs.begin(), LoopBBs.end()); 180 181 typedef GraphTraits<BlockT*> BlockTraits; 182 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) 183 for (typename BlockTraits::ChildIteratorType I = 184 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 185 I != E; ++I) 186 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) { 187 // Not in current loop? It must be an exit block. 188 ExitingBlocks.push_back(*BI); 189 break; 190 } 191 } 192 193 /// getExitingBlock - If getExitingBlocks would return exactly one block, 194 /// return that block. Otherwise return null. 195 BlockT *getExitingBlock() const { 196 SmallVector<BlockT*, 8> ExitingBlocks; 197 getExitingBlocks(ExitingBlocks); 198 if (ExitingBlocks.size() == 1) 199 return ExitingBlocks[0]; 200 return 0; 201 } 202 203 /// getExitBlocks - Return all of the successor blocks of this loop. These 204 /// are the blocks _outside of the current loop_ which are branched to. 205 /// 206 void getExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const { 207 // Sort the blocks vector so that we can use binary search to do quick 208 // lookups. 209 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 210 std::sort(LoopBBs.begin(), LoopBBs.end()); 211 212 typedef GraphTraits<BlockT*> BlockTraits; 213 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) 214 for (typename BlockTraits::ChildIteratorType I = 215 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 216 I != E; ++I) 217 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) 218 // Not in current loop? It must be an exit block. 219 ExitBlocks.push_back(*I); 220 } 221 222 /// getExitBlock - If getExitBlocks would return exactly one block, 223 /// return that block. Otherwise return null. 224 BlockT *getExitBlock() const { 225 SmallVector<BlockT*, 8> ExitBlocks; 226 getExitBlocks(ExitBlocks); 227 if (ExitBlocks.size() == 1) 228 return ExitBlocks[0]; 229 return 0; 230 } 231 232 /// Edge type. 233 typedef std::pair<BlockT*, BlockT*> Edge; 234 235 /// getExitEdges - Return all pairs of (_inside_block_,_outside_block_). 236 template <typename EdgeT> 237 void getExitEdges(SmallVectorImpl<EdgeT> &ExitEdges) const { 238 // Sort the blocks vector so that we can use binary search to do quick 239 // lookups. 240 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 241 std::sort(LoopBBs.begin(), LoopBBs.end()); 242 243 typedef GraphTraits<BlockT*> BlockTraits; 244 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) 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 // Not in current loop? It must be an exit block. 250 ExitEdges.push_back(EdgeT(*BI, *I)); 251 } 252 253 /// getLoopPreheader - If there is a preheader for this loop, return it. A 254 /// loop has a preheader if there is only one edge to the header of the loop 255 /// from outside of the loop. If this is the case, the block branching to the 256 /// header of the loop is the preheader node. 257 /// 258 /// This method returns null if there is no preheader for the loop. 259 /// 260 BlockT *getLoopPreheader() const { 261 // Keep track of nodes outside the loop branching to the header... 262 BlockT *Out = getLoopPredecessor(); 263 if (!Out) return 0; 264 265 // Make sure there is only one exit out of the preheader. 266 typedef GraphTraits<BlockT*> BlockTraits; 267 typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out); 268 ++SI; 269 if (SI != BlockTraits::child_end(Out)) 270 return 0; // Multiple exits from the block, must not be a preheader. 271 272 // The predecessor has exactly one successor, so it is a preheader. 273 return Out; 274 } 275 276 /// getLoopPredecessor - If the given loop's header has exactly one unique 277 /// predecessor outside the loop, return it. Otherwise return null. 278 /// This is less strict that the loop "preheader" concept, which requires 279 /// the predecessor to have exactly one successor. 280 /// 281 BlockT *getLoopPredecessor() const { 282 // Keep track of nodes outside the loop branching to the header... 283 BlockT *Out = 0; 284 285 // Loop over the predecessors of the header node... 286 BlockT *Header = getHeader(); 287 typedef GraphTraits<BlockT*> BlockTraits; 288 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 289 for (typename InvBlockTraits::ChildIteratorType PI = 290 InvBlockTraits::child_begin(Header), 291 PE = InvBlockTraits::child_end(Header); PI != PE; ++PI) { 292 typename InvBlockTraits::NodeType *N = *PI; 293 if (!contains(N)) { // If the block is not in the loop... 294 if (Out && Out != N) 295 return 0; // Multiple predecessors outside the loop 296 Out = N; 297 } 298 } 299 300 // Make sure there is only one exit out of the preheader. 301 assert(Out && "Header of loop has no predecessors from outside loop?"); 302 return Out; 303 } 304 305 /// getLoopLatch - If there is a single latch block for this loop, return it. 306 /// A latch block is a block that contains a branch back to the header. 307 BlockT *getLoopLatch() const { 308 BlockT *Header = getHeader(); 309 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 310 typename InvBlockTraits::ChildIteratorType PI = 311 InvBlockTraits::child_begin(Header); 312 typename InvBlockTraits::ChildIteratorType PE = 313 InvBlockTraits::child_end(Header); 314 BlockT *Latch = 0; 315 for (; PI != PE; ++PI) { 316 typename InvBlockTraits::NodeType *N = *PI; 317 if (contains(N)) { 318 if (Latch) return 0; 319 Latch = N; 320 } 321 } 322 323 return Latch; 324 } 325 326 //===--------------------------------------------------------------------===// 327 // APIs for updating loop information after changing the CFG 328 // 329 330 /// addBasicBlockToLoop - This method is used by other analyses to update loop 331 /// information. NewBB is set to be a new member of the current loop. 332 /// Because of this, it is added as a member of all parent loops, and is added 333 /// to the specified LoopInfo object as being in the current basic block. It 334 /// is not valid to replace the loop header with this method. 335 /// 336 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LI); 337 338 /// replaceChildLoopWith - This is used when splitting loops up. It replaces 339 /// the OldChild entry in our children list with NewChild, and updates the 340 /// parent pointer of OldChild to be null and the NewChild to be this loop. 341 /// This updates the loop depth of the new child. 342 void replaceChildLoopWith(LoopT *OldChild, 343 LoopT *NewChild) { 344 assert(OldChild->ParentLoop == this && "This loop is already broken!"); 345 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 346 typename std::vector<LoopT *>::iterator I = 347 std::find(SubLoops.begin(), SubLoops.end(), OldChild); 348 assert(I != SubLoops.end() && "OldChild not in loop!"); 349 *I = NewChild; 350 OldChild->ParentLoop = 0; 351 NewChild->ParentLoop = static_cast<LoopT *>(this); 352 } 353 354 /// addChildLoop - Add the specified loop to be a child of this loop. This 355 /// updates the loop depth of the new child. 356 /// 357 void addChildLoop(LoopT *NewChild) { 358 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 359 NewChild->ParentLoop = static_cast<LoopT *>(this); 360 SubLoops.push_back(NewChild); 361 } 362 363 /// removeChildLoop - This removes the specified child from being a subloop of 364 /// this loop. The loop is not deleted, as it will presumably be inserted 365 /// into another loop. 366 LoopT *removeChildLoop(iterator I) { 367 assert(I != SubLoops.end() && "Cannot remove end iterator!"); 368 LoopT *Child = *I; 369 assert(Child->ParentLoop == this && "Child is not a child of this loop!"); 370 SubLoops.erase(SubLoops.begin()+(I-begin())); 371 Child->ParentLoop = 0; 372 return Child; 373 } 374 375 /// addBlockEntry - This adds a basic block directly to the basic block list. 376 /// This should only be used by transformations that create new loops. Other 377 /// transformations should use addBasicBlockToLoop. 378 void addBlockEntry(BlockT *BB) { 379 Blocks.push_back(BB); 380 } 381 382 /// moveToHeader - This method is used to move BB (which must be part of this 383 /// loop) to be the loop header of the loop (the block that dominates all 384 /// others). 385 void moveToHeader(BlockT *BB) { 386 if (Blocks[0] == BB) return; 387 for (unsigned i = 0; ; ++i) { 388 assert(i != Blocks.size() && "Loop does not contain BB!"); 389 if (Blocks[i] == BB) { 390 Blocks[i] = Blocks[0]; 391 Blocks[0] = BB; 392 return; 393 } 394 } 395 } 396 397 /// removeBlockFromLoop - This removes the specified basic block from the 398 /// current loop, updating the Blocks as appropriate. This does not update 399 /// the mapping in the LoopInfo class. 400 void removeBlockFromLoop(BlockT *BB) { 401 RemoveFromVector(Blocks, BB); 402 } 403 404 /// verifyLoop - Verify loop structure 405 void verifyLoop() const { 406#ifndef NDEBUG 407 assert(!Blocks.empty() && "Loop header is missing"); 408 409 // Sort the blocks vector so that we can use binary search to do quick 410 // lookups. 411 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 412 std::sort(LoopBBs.begin(), LoopBBs.end()); 413 414 // Check the individual blocks. 415 for (block_iterator I = block_begin(), E = block_end(); I != E; ++I) { 416 BlockT *BB = *I; 417 bool HasInsideLoopSuccs = false; 418 bool HasInsideLoopPreds = false; 419 SmallVector<BlockT *, 2> OutsideLoopPreds; 420 421 typedef GraphTraits<BlockT*> BlockTraits; 422 for (typename BlockTraits::ChildIteratorType SI = 423 BlockTraits::child_begin(BB), SE = BlockTraits::child_end(BB); 424 SI != SE; ++SI) 425 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *SI)) { 426 HasInsideLoopSuccs = true; 427 break; 428 } 429 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 430 for (typename InvBlockTraits::ChildIteratorType PI = 431 InvBlockTraits::child_begin(BB), PE = InvBlockTraits::child_end(BB); 432 PI != PE; ++PI) { 433 typename InvBlockTraits::NodeType *N = *PI; 434 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), N)) 435 HasInsideLoopPreds = true; 436 else 437 OutsideLoopPreds.push_back(N); 438 } 439 440 if (BB == getHeader()) { 441 assert(!OutsideLoopPreds.empty() && "Loop is unreachable!"); 442 } else if (!OutsideLoopPreds.empty()) { 443 // A non-header loop shouldn't be reachable from outside the loop, 444 // though it is permitted if the predecessor is not itself actually 445 // reachable. 446 BlockT *EntryBB = BB->getParent()->begin(); 447 for (df_iterator<BlockT *> NI = df_begin(EntryBB), 448 NE = df_end(EntryBB); NI != NE; ++NI) 449 for (unsigned i = 0, e = OutsideLoopPreds.size(); i != e; ++i) 450 assert(*NI != OutsideLoopPreds[i] && 451 "Loop has multiple entry points!"); 452 } 453 assert(HasInsideLoopPreds && "Loop block has no in-loop predecessors!"); 454 assert(HasInsideLoopSuccs && "Loop block has no in-loop successors!"); 455 assert(BB != getHeader()->getParent()->begin() && 456 "Loop contains function entry block!"); 457 } 458 459 // Check the subloops. 460 for (iterator I = begin(), E = end(); I != E; ++I) 461 // Each block in each subloop should be contained within this loop. 462 for (block_iterator BI = (*I)->block_begin(), BE = (*I)->block_end(); 463 BI != BE; ++BI) { 464 assert(std::binary_search(LoopBBs.begin(), LoopBBs.end(), *BI) && 465 "Loop does not contain all the blocks of a subloop!"); 466 } 467 468 // Check the parent loop pointer. 469 if (ParentLoop) { 470 assert(std::find(ParentLoop->begin(), ParentLoop->end(), this) != 471 ParentLoop->end() && 472 "Loop is not a subloop of its parent!"); 473 } 474#endif 475 } 476 477 /// verifyLoop - Verify loop structure of this loop and all nested loops. 478 void verifyLoopNest() const { 479 // Verify this loop. 480 verifyLoop(); 481 // Verify the subloops. 482 for (iterator I = begin(), E = end(); I != E; ++I) 483 (*I)->verifyLoopNest(); 484 } 485 486 void print(raw_ostream &OS, unsigned Depth = 0) const { 487 OS.indent(Depth*2) << "Loop at depth " << getLoopDepth() 488 << " containing: "; 489 490 for (unsigned i = 0; i < getBlocks().size(); ++i) { 491 if (i) OS << ","; 492 BlockT *BB = getBlocks()[i]; 493 WriteAsOperand(OS, BB, false); 494 if (BB == getHeader()) OS << "<header>"; 495 if (BB == getLoopLatch()) OS << "<latch>"; 496 if (isLoopExiting(BB)) OS << "<exiting>"; 497 } 498 OS << "\n"; 499 500 for (iterator I = begin(), E = end(); I != E; ++I) 501 (*I)->print(OS, Depth+2); 502 } 503 504protected: 505 friend class LoopInfoBase<BlockT, LoopT>; 506 explicit LoopBase(BlockT *BB) : ParentLoop(0) { 507 Blocks.push_back(BB); 508 } 509}; 510 511class Loop : public LoopBase<BasicBlock, Loop> { 512public: 513 Loop() {} 514 515 /// isLoopInvariant - Return true if the specified value is loop invariant 516 /// 517 bool isLoopInvariant(Value *V) const; 518 519 /// isLoopInvariant - Return true if the specified instruction is 520 /// loop-invariant. 521 /// 522 bool isLoopInvariant(Instruction *I) const; 523 524 /// makeLoopInvariant - If the given value is an instruction inside of the 525 /// loop and it can be hoisted, do so to make it trivially loop-invariant. 526 /// Return true if the value after any hoisting is loop invariant. This 527 /// function can be used as a slightly more aggressive replacement for 528 /// isLoopInvariant. 529 /// 530 /// If InsertPt is specified, it is the point to hoist instructions to. 531 /// If null, the terminator of the loop preheader is used. 532 /// 533 bool makeLoopInvariant(Value *V, bool &Changed, 534 Instruction *InsertPt = 0) const; 535 536 /// makeLoopInvariant - If the given instruction is inside of the 537 /// loop and it can be hoisted, do so to make it trivially loop-invariant. 538 /// Return true if the instruction after any hoisting is loop invariant. This 539 /// function can be used as a slightly more aggressive replacement for 540 /// isLoopInvariant. 541 /// 542 /// If InsertPt is specified, it is the point to hoist instructions to. 543 /// If null, the terminator of the loop preheader is used. 544 /// 545 bool makeLoopInvariant(Instruction *I, bool &Changed, 546 Instruction *InsertPt = 0) const; 547 548 /// getCanonicalInductionVariable - Check to see if the loop has a canonical 549 /// induction variable: an integer recurrence that starts at 0 and increments 550 /// by one each time through the loop. If so, return the phi node that 551 /// corresponds to it. 552 /// 553 /// The IndVarSimplify pass transforms loops to have a canonical induction 554 /// variable. 555 /// 556 PHINode *getCanonicalInductionVariable() const; 557 558 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds 559 /// the canonical induction variable value for the "next" iteration of the 560 /// loop. This always succeeds if getCanonicalInductionVariable succeeds. 561 /// 562 Instruction *getCanonicalInductionVariableIncrement() const; 563 564 /// getTripCount - Return a loop-invariant LLVM value indicating the number of 565 /// times the loop will be executed. Note that this means that the backedge 566 /// of the loop executes N-1 times. If the trip-count cannot be determined, 567 /// this returns null. 568 /// 569 /// The IndVarSimplify pass transforms loops to have a form that this 570 /// function easily understands. 571 /// 572 Value *getTripCount() const; 573 574 /// getSmallConstantTripCount - Returns the trip count of this loop as a 575 /// normal unsigned value, if possible. Returns 0 if the trip count is unknown 576 /// of not constant. Will also return 0 if the trip count is very large 577 /// (>= 2^32) 578 /// 579 /// The IndVarSimplify pass transforms loops to have a form that this 580 /// function easily understands. 581 /// 582 unsigned getSmallConstantTripCount() const; 583 584 /// getSmallConstantTripMultiple - Returns the largest constant divisor of the 585 /// trip count of this loop as a normal unsigned value, if possible. This 586 /// means that the actual trip count is always a multiple of the returned 587 /// value (don't forget the trip count could very well be zero as well!). 588 /// 589 /// Returns 1 if the trip count is unknown or not guaranteed to be the 590 /// multiple of a constant (which is also the case if the trip count is simply 591 /// constant, use getSmallConstantTripCount for that case), Will also return 1 592 /// if the trip count is very large (>= 2^32). 593 unsigned getSmallConstantTripMultiple() const; 594 595 /// isLCSSAForm - Return true if the Loop is in LCSSA form 596 bool isLCSSAForm(DominatorTree &DT) const; 597 598 /// isLoopSimplifyForm - Return true if the Loop is in the form that 599 /// the LoopSimplify form transforms loops to, which is sometimes called 600 /// normal form. 601 bool isLoopSimplifyForm() const; 602 603 /// hasDedicatedExits - Return true if no exit block for the loop 604 /// has a predecessor that is outside the loop. 605 bool hasDedicatedExits() const; 606 607 /// getUniqueExitBlocks - Return all unique successor blocks of this loop. 608 /// These are the blocks _outside of the current loop_ which are branched to. 609 /// This assumes that loop exits are in canonical form. 610 /// 611 void getUniqueExitBlocks(SmallVectorImpl<BasicBlock *> &ExitBlocks) const; 612 613 /// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one 614 /// block, return that block. Otherwise return null. 615 BasicBlock *getUniqueExitBlock() const; 616 617 void dump() const; 618 619private: 620 friend class LoopInfoBase<BasicBlock, Loop>; 621 explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {} 622}; 623 624//===----------------------------------------------------------------------===// 625/// LoopInfo - This class builds and contains all of the top level loop 626/// structures in the specified function. 627/// 628 629template<class BlockT, class LoopT> 630class LoopInfoBase { 631 // BBMap - Mapping of basic blocks to the inner most loop they occur in 632 std::map<BlockT *, LoopT *> BBMap; 633 std::vector<LoopT *> TopLevelLoops; 634 friend class LoopBase<BlockT, LoopT>; 635 636 void operator=(const LoopInfoBase &); // do not implement 637 LoopInfoBase(const LoopInfo &); // do not implement 638public: 639 LoopInfoBase() { } 640 ~LoopInfoBase() { releaseMemory(); } 641 642 void releaseMemory() { 643 for (typename std::vector<LoopT *>::iterator I = 644 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I) 645 delete *I; // Delete all of the loops... 646 647 BBMap.clear(); // Reset internal state of analysis 648 TopLevelLoops.clear(); 649 } 650 651 /// iterator/begin/end - The interface to the top-level loops in the current 652 /// function. 653 /// 654 typedef typename std::vector<LoopT *>::const_iterator iterator; 655 iterator begin() const { return TopLevelLoops.begin(); } 656 iterator end() const { return TopLevelLoops.end(); } 657 bool empty() const { return TopLevelLoops.empty(); } 658 659 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 660 /// block is in no loop (for example the entry node), null is returned. 661 /// 662 LoopT *getLoopFor(const BlockT *BB) const { 663 typename std::map<BlockT *, LoopT *>::const_iterator I= 664 BBMap.find(const_cast<BlockT*>(BB)); 665 return I != BBMap.end() ? I->second : 0; 666 } 667 668 /// operator[] - same as getLoopFor... 669 /// 670 const LoopT *operator[](const BlockT *BB) const { 671 return getLoopFor(BB); 672 } 673 674 /// getLoopDepth - Return the loop nesting level of the specified block. A 675 /// depth of 0 means the block is not inside any loop. 676 /// 677 unsigned getLoopDepth(const BlockT *BB) const { 678 const LoopT *L = getLoopFor(BB); 679 return L ? L->getLoopDepth() : 0; 680 } 681 682 // isLoopHeader - True if the block is a loop header node 683 bool isLoopHeader(BlockT *BB) const { 684 const LoopT *L = getLoopFor(BB); 685 return L && L->getHeader() == BB; 686 } 687 688 /// removeLoop - This removes the specified top-level loop from this loop info 689 /// object. The loop is not deleted, as it will presumably be inserted into 690 /// another loop. 691 LoopT *removeLoop(iterator I) { 692 assert(I != end() && "Cannot remove end iterator!"); 693 LoopT *L = *I; 694 assert(L->getParentLoop() == 0 && "Not a top-level loop!"); 695 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin())); 696 return L; 697 } 698 699 /// changeLoopFor - Change the top-level loop that contains BB to the 700 /// specified loop. This should be used by transformations that restructure 701 /// the loop hierarchy tree. 702 void changeLoopFor(BlockT *BB, LoopT *L) { 703 LoopT *&OldLoop = BBMap[BB]; 704 assert(OldLoop && "Block not in a loop yet!"); 705 OldLoop = L; 706 } 707 708 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 709 /// list with the indicated loop. 710 void changeTopLevelLoop(LoopT *OldLoop, 711 LoopT *NewLoop) { 712 typename std::vector<LoopT *>::iterator I = 713 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop); 714 assert(I != TopLevelLoops.end() && "Old loop not at top level!"); 715 *I = NewLoop; 716 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 && 717 "Loops already embedded into a subloop!"); 718 } 719 720 /// addTopLevelLoop - This adds the specified loop to the collection of 721 /// top-level loops. 722 void addTopLevelLoop(LoopT *New) { 723 assert(New->getParentLoop() == 0 && "Loop already in subloop!"); 724 TopLevelLoops.push_back(New); 725 } 726 727 /// removeBlock - This method completely removes BB from all data structures, 728 /// including all of the Loop objects it is nested in and our mapping from 729 /// BasicBlocks to loops. 730 void removeBlock(BlockT *BB) { 731 typename std::map<BlockT *, LoopT *>::iterator I = BBMap.find(BB); 732 if (I != BBMap.end()) { 733 for (LoopT *L = I->second; L; L = L->getParentLoop()) 734 L->removeBlockFromLoop(BB); 735 736 BBMap.erase(I); 737 } 738 } 739 740 // Internals 741 742 static bool isNotAlreadyContainedIn(const LoopT *SubLoop, 743 const LoopT *ParentLoop) { 744 if (SubLoop == 0) return true; 745 if (SubLoop == ParentLoop) return false; 746 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop); 747 } 748 749 void Calculate(DominatorTreeBase<BlockT> &DT) { 750 BlockT *RootNode = DT.getRootNode()->getBlock(); 751 752 for (df_iterator<BlockT*> NI = df_begin(RootNode), 753 NE = df_end(RootNode); NI != NE; ++NI) 754 if (LoopT *L = ConsiderForLoop(*NI, DT)) 755 TopLevelLoops.push_back(L); 756 } 757 758 LoopT *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) { 759 if (BBMap.find(BB) != BBMap.end()) return 0;// Haven't processed this node? 760 761 std::vector<BlockT *> TodoStack; 762 763 // Scan the predecessors of BB, checking to see if BB dominates any of 764 // them. This identifies backedges which target this node... 765 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 766 for (typename InvBlockTraits::ChildIteratorType I = 767 InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB); 768 I != E; ++I) { 769 typename InvBlockTraits::NodeType *N = *I; 770 if (DT.dominates(BB, N)) // If BB dominates its predecessor... 771 TodoStack.push_back(N); 772 } 773 774 if (TodoStack.empty()) return 0; // No backedges to this block... 775 776 // Create a new loop to represent this basic block... 777 LoopT *L = new LoopT(BB); 778 BBMap[BB] = L; 779 780 BlockT *EntryBlock = BB->getParent()->begin(); 781 782 while (!TodoStack.empty()) { // Process all the nodes in the loop 783 BlockT *X = TodoStack.back(); 784 TodoStack.pop_back(); 785 786 if (!L->contains(X) && // As of yet unprocessed?? 787 DT.dominates(EntryBlock, X)) { // X is reachable from entry block? 788 // Check to see if this block already belongs to a loop. If this occurs 789 // then we have a case where a loop that is supposed to be a child of 790 // the current loop was processed before the current loop. When this 791 // occurs, this child loop gets added to a part of the current loop, 792 // making it a sibling to the current loop. We have to reparent this 793 // loop. 794 if (LoopT *SubLoop = 795 const_cast<LoopT *>(getLoopFor(X))) 796 if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){ 797 // Remove the subloop from its current parent... 798 assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L); 799 LoopT *SLP = SubLoop->ParentLoop; // SubLoopParent 800 typename std::vector<LoopT *>::iterator I = 801 std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop); 802 assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?"); 803 SLP->SubLoops.erase(I); // Remove from parent... 804 805 // Add the subloop to THIS loop... 806 SubLoop->ParentLoop = L; 807 L->SubLoops.push_back(SubLoop); 808 } 809 810 // Normal case, add the block to our loop... 811 L->Blocks.push_back(X); 812 813 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 814 815 // Add all of the predecessors of X to the end of the work stack... 816 TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X), 817 InvBlockTraits::child_end(X)); 818 } 819 } 820 821 // If there are any loops nested within this loop, create them now! 822 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 823 E = L->Blocks.end(); I != E; ++I) 824 if (LoopT *NewLoop = ConsiderForLoop(*I, DT)) { 825 L->SubLoops.push_back(NewLoop); 826 NewLoop->ParentLoop = L; 827 } 828 829 // Add the basic blocks that comprise this loop to the BBMap so that this 830 // loop can be found for them. 831 // 832 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 833 E = L->Blocks.end(); I != E; ++I) 834 BBMap.insert(std::make_pair(*I, L)); 835 836 // Now that we have a list of all of the child loops of this loop, check to 837 // see if any of them should actually be nested inside of each other. We 838 // can accidentally pull loops our of their parents, so we must make sure to 839 // organize the loop nests correctly now. 840 { 841 std::map<BlockT *, LoopT *> ContainingLoops; 842 for (unsigned i = 0; i != L->SubLoops.size(); ++i) { 843 LoopT *Child = L->SubLoops[i]; 844 assert(Child->getParentLoop() == L && "Not proper child loop?"); 845 846 if (LoopT *ContainingLoop = ContainingLoops[Child->getHeader()]) { 847 // If there is already a loop which contains this loop, move this loop 848 // into the containing loop. 849 MoveSiblingLoopInto(Child, ContainingLoop); 850 --i; // The loop got removed from the SubLoops list. 851 } else { 852 // This is currently considered to be a top-level loop. Check to see 853 // if any of the contained blocks are loop headers for subloops we 854 // have already processed. 855 for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) { 856 LoopT *&BlockLoop = ContainingLoops[Child->Blocks[b]]; 857 if (BlockLoop == 0) { // Child block not processed yet... 858 BlockLoop = Child; 859 } else if (BlockLoop != Child) { 860 LoopT *SubLoop = BlockLoop; 861 // Reparent all of the blocks which used to belong to BlockLoops 862 for (unsigned j = 0, f = SubLoop->Blocks.size(); j != f; ++j) 863 ContainingLoops[SubLoop->Blocks[j]] = Child; 864 865 // There is already a loop which contains this block, that means 866 // that we should reparent the loop which the block is currently 867 // considered to belong to to be a child of this loop. 868 MoveSiblingLoopInto(SubLoop, Child); 869 --i; // We just shrunk the SubLoops list. 870 } 871 } 872 } 873 } 874 } 875 876 return L; 877 } 878 879 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside 880 /// of the NewParent Loop, instead of being a sibling of it. 881 void MoveSiblingLoopInto(LoopT *NewChild, 882 LoopT *NewParent) { 883 LoopT *OldParent = NewChild->getParentLoop(); 884 assert(OldParent && OldParent == NewParent->getParentLoop() && 885 NewChild != NewParent && "Not sibling loops!"); 886 887 // Remove NewChild from being a child of OldParent 888 typename std::vector<LoopT *>::iterator I = 889 std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(), 890 NewChild); 891 assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??"); 892 OldParent->SubLoops.erase(I); // Remove from parent's subloops list 893 NewChild->ParentLoop = 0; 894 895 InsertLoopInto(NewChild, NewParent); 896 } 897 898 /// InsertLoopInto - This inserts loop L into the specified parent loop. If 899 /// the parent loop contains a loop which should contain L, the loop gets 900 /// inserted into L instead. 901 void InsertLoopInto(LoopT *L, LoopT *Parent) { 902 BlockT *LHeader = L->getHeader(); 903 assert(Parent->contains(LHeader) && 904 "This loop should not be inserted here!"); 905 906 // Check to see if it belongs in a child loop... 907 for (unsigned i = 0, e = static_cast<unsigned>(Parent->SubLoops.size()); 908 i != e; ++i) 909 if (Parent->SubLoops[i]->contains(LHeader)) { 910 InsertLoopInto(L, Parent->SubLoops[i]); 911 return; 912 } 913 914 // If not, insert it here! 915 Parent->SubLoops.push_back(L); 916 L->ParentLoop = Parent; 917 } 918 919 // Debugging 920 921 void print(raw_ostream &OS) const { 922 for (unsigned i = 0; i < TopLevelLoops.size(); ++i) 923 TopLevelLoops[i]->print(OS); 924 #if 0 925 for (std::map<BasicBlock*, LoopT*>::const_iterator I = BBMap.begin(), 926 E = BBMap.end(); I != E; ++I) 927 OS << "BB '" << I->first->getName() << "' level = " 928 << I->second->getLoopDepth() << "\n"; 929 #endif 930 } 931}; 932 933class LoopInfo : public FunctionPass { 934 LoopInfoBase<BasicBlock, Loop> LI; 935 friend class LoopBase<BasicBlock, Loop>; 936 937 void operator=(const LoopInfo &); // do not implement 938 LoopInfo(const LoopInfo &); // do not implement 939public: 940 static char ID; // Pass identification, replacement for typeid 941 942 LoopInfo() : FunctionPass(&ID) {} 943 944 LoopInfoBase<BasicBlock, Loop>& getBase() { return LI; } 945 946 /// iterator/begin/end - The interface to the top-level loops in the current 947 /// function. 948 /// 949 typedef LoopInfoBase<BasicBlock, Loop>::iterator iterator; 950 inline iterator begin() const { return LI.begin(); } 951 inline iterator end() const { return LI.end(); } 952 bool empty() const { return LI.empty(); } 953 954 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 955 /// block is in no loop (for example the entry node), null is returned. 956 /// 957 inline Loop *getLoopFor(const BasicBlock *BB) const { 958 return LI.getLoopFor(BB); 959 } 960 961 /// operator[] - same as getLoopFor... 962 /// 963 inline const Loop *operator[](const BasicBlock *BB) const { 964 return LI.getLoopFor(BB); 965 } 966 967 /// getLoopDepth - Return the loop nesting level of the specified block. A 968 /// depth of 0 means the block is not inside any loop. 969 /// 970 inline unsigned getLoopDepth(const BasicBlock *BB) const { 971 return LI.getLoopDepth(BB); 972 } 973 974 // isLoopHeader - True if the block is a loop header node 975 inline bool isLoopHeader(BasicBlock *BB) const { 976 return LI.isLoopHeader(BB); 977 } 978 979 /// runOnFunction - Calculate the natural loop information. 980 /// 981 virtual bool runOnFunction(Function &F); 982 983 virtual void verifyAnalysis() const; 984 985 virtual void releaseMemory() { LI.releaseMemory(); } 986 987 virtual void print(raw_ostream &O, const Module* M = 0) const; 988 989 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 990 991 /// removeLoop - This removes the specified top-level loop from this loop info 992 /// object. The loop is not deleted, as it will presumably be inserted into 993 /// another loop. 994 inline Loop *removeLoop(iterator I) { return LI.removeLoop(I); } 995 996 /// changeLoopFor - Change the top-level loop that contains BB to the 997 /// specified loop. This should be used by transformations that restructure 998 /// the loop hierarchy tree. 999 inline void changeLoopFor(BasicBlock *BB, Loop *L) { 1000 LI.changeLoopFor(BB, L); 1001 } 1002 1003 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 1004 /// list with the indicated loop. 1005 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) { 1006 LI.changeTopLevelLoop(OldLoop, NewLoop); 1007 } 1008 1009 /// addTopLevelLoop - This adds the specified loop to the collection of 1010 /// top-level loops. 1011 inline void addTopLevelLoop(Loop *New) { 1012 LI.addTopLevelLoop(New); 1013 } 1014 1015 /// removeBlock - This method completely removes BB from all data structures, 1016 /// including all of the Loop objects it is nested in and our mapping from 1017 /// BasicBlocks to loops. 1018 void removeBlock(BasicBlock *BB) { 1019 LI.removeBlock(BB); 1020 } 1021}; 1022 1023 1024// Allow clients to walk the list of nested loops... 1025template <> struct GraphTraits<const Loop*> { 1026 typedef const Loop NodeType; 1027 typedef LoopInfo::iterator ChildIteratorType; 1028 1029 static NodeType *getEntryNode(const Loop *L) { return L; } 1030 static inline ChildIteratorType child_begin(NodeType *N) { 1031 return N->begin(); 1032 } 1033 static inline ChildIteratorType child_end(NodeType *N) { 1034 return N->end(); 1035 } 1036}; 1037 1038template <> struct GraphTraits<Loop*> { 1039 typedef Loop NodeType; 1040 typedef LoopInfo::iterator ChildIteratorType; 1041 1042 static NodeType *getEntryNode(Loop *L) { return L; } 1043 static inline ChildIteratorType child_begin(NodeType *N) { 1044 return N->begin(); 1045 } 1046 static inline ChildIteratorType child_end(NodeType *N) { 1047 return N->end(); 1048 } 1049}; 1050 1051template<class BlockT, class LoopT> 1052void 1053LoopBase<BlockT, LoopT>::addBasicBlockToLoop(BlockT *NewBB, 1054 LoopInfoBase<BlockT, LoopT> &LIB) { 1055 assert((Blocks.empty() || LIB[getHeader()] == this) && 1056 "Incorrect LI specified for this loop!"); 1057 assert(NewBB && "Cannot add a null basic block to the loop!"); 1058 assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!"); 1059 1060 LoopT *L = static_cast<LoopT *>(this); 1061 1062 // Add the loop mapping to the LoopInfo object... 1063 LIB.BBMap[NewBB] = L; 1064 1065 // Add the basic block to this loop and all parent loops... 1066 while (L) { 1067 L->Blocks.push_back(NewBB); 1068 L = L->getParentLoop(); 1069 } 1070} 1071 1072} // End llvm namespace 1073 1074#endif 1075