LoopInfo.h revision 4fd6b397031d7b5baa01849c065ad7ef70882d83
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 /// getExitEdges - Return all pairs of (_inside_block_,_outside_block_). 233 typedef std::pair<const BlockT*,const BlockT*> Edge; 234 void getExitEdges(SmallVectorImpl<Edge> &ExitEdges) const { 235 // Sort the blocks vector so that we can use binary search to do quick 236 // lookups. 237 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 238 std::sort(LoopBBs.begin(), LoopBBs.end()); 239 240 typedef GraphTraits<BlockT*> BlockTraits; 241 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) 242 for (typename BlockTraits::ChildIteratorType I = 243 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 244 I != E; ++I) 245 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) 246 // Not in current loop? It must be an exit block. 247 ExitEdges.push_back(std::make_pair(*BI, *I)); 248 } 249 250 /// getLoopPreheader - If there is a preheader for this loop, return it. A 251 /// loop has a preheader if there is only one edge to the header of the loop 252 /// from outside of the loop. If this is the case, the block branching to the 253 /// header of the loop is the preheader node. 254 /// 255 /// This method returns null if there is no preheader for the loop. 256 /// 257 BlockT *getLoopPreheader() const { 258 // Keep track of nodes outside the loop branching to the header... 259 BlockT *Out = getLoopPredecessor(); 260 if (!Out) return 0; 261 262 // Make sure there is only one exit out of the preheader. 263 typedef GraphTraits<BlockT*> BlockTraits; 264 typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out); 265 ++SI; 266 if (SI != BlockTraits::child_end(Out)) 267 return 0; // Multiple exits from the block, must not be a preheader. 268 269 // The predecessor has exactly one successor, so it is a preheader. 270 return Out; 271 } 272 273 /// getLoopPredecessor - If the given loop's header has exactly one unique 274 /// predecessor outside the loop, return it. Otherwise return null. 275 /// This is less strict that the loop "preheader" concept, which requires 276 /// the predecessor to have exactly one successor. 277 /// 278 BlockT *getLoopPredecessor() const { 279 // Keep track of nodes outside the loop branching to the header... 280 BlockT *Out = 0; 281 282 // Loop over the predecessors of the header node... 283 BlockT *Header = getHeader(); 284 typedef GraphTraits<BlockT*> BlockTraits; 285 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 286 for (typename InvBlockTraits::ChildIteratorType PI = 287 InvBlockTraits::child_begin(Header), 288 PE = InvBlockTraits::child_end(Header); PI != PE; ++PI) { 289 typename InvBlockTraits::NodeType *N = *PI; 290 if (!contains(N)) { // If the block is not in the loop... 291 if (Out && Out != N) 292 return 0; // Multiple predecessors outside the loop 293 Out = N; 294 } 295 } 296 297 // Make sure there is only one exit out of the preheader. 298 assert(Out && "Header of loop has no predecessors from outside loop?"); 299 return Out; 300 } 301 302 /// getLoopLatch - If there is a single latch block for this loop, return it. 303 /// A latch block is a block that contains a branch back to the header. 304 BlockT *getLoopLatch() const { 305 BlockT *Header = getHeader(); 306 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 307 typename InvBlockTraits::ChildIteratorType PI = 308 InvBlockTraits::child_begin(Header); 309 typename InvBlockTraits::ChildIteratorType PE = 310 InvBlockTraits::child_end(Header); 311 BlockT *Latch = 0; 312 for (; PI != PE; ++PI) 313 if (contains(*PI)) { 314 if (Latch) return 0; 315 Latch = *PI; 316 } 317 318 return Latch; 319 } 320 321 //===--------------------------------------------------------------------===// 322 // APIs for updating loop information after changing the CFG 323 // 324 325 /// addBasicBlockToLoop - This method is used by other analyses to update loop 326 /// information. NewBB is set to be a new member of the current loop. 327 /// Because of this, it is added as a member of all parent loops, and is added 328 /// to the specified LoopInfo object as being in the current basic block. It 329 /// is not valid to replace the loop header with this method. 330 /// 331 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LI); 332 333 /// replaceChildLoopWith - This is used when splitting loops up. It replaces 334 /// the OldChild entry in our children list with NewChild, and updates the 335 /// parent pointer of OldChild to be null and the NewChild to be this loop. 336 /// This updates the loop depth of the new child. 337 void replaceChildLoopWith(LoopT *OldChild, 338 LoopT *NewChild) { 339 assert(OldChild->ParentLoop == this && "This loop is already broken!"); 340 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 341 typename std::vector<LoopT *>::iterator I = 342 std::find(SubLoops.begin(), SubLoops.end(), OldChild); 343 assert(I != SubLoops.end() && "OldChild not in loop!"); 344 *I = NewChild; 345 OldChild->ParentLoop = 0; 346 NewChild->ParentLoop = static_cast<LoopT *>(this); 347 } 348 349 /// addChildLoop - Add the specified loop to be a child of this loop. This 350 /// updates the loop depth of the new child. 351 /// 352 void addChildLoop(LoopT *NewChild) { 353 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 354 NewChild->ParentLoop = static_cast<LoopT *>(this); 355 SubLoops.push_back(NewChild); 356 } 357 358 /// removeChildLoop - This removes the specified child from being a subloop of 359 /// this loop. The loop is not deleted, as it will presumably be inserted 360 /// into another loop. 361 LoopT *removeChildLoop(iterator I) { 362 assert(I != SubLoops.end() && "Cannot remove end iterator!"); 363 LoopT *Child = *I; 364 assert(Child->ParentLoop == this && "Child is not a child of this loop!"); 365 SubLoops.erase(SubLoops.begin()+(I-begin())); 366 Child->ParentLoop = 0; 367 return Child; 368 } 369 370 /// addBlockEntry - This adds a basic block directly to the basic block list. 371 /// This should only be used by transformations that create new loops. Other 372 /// transformations should use addBasicBlockToLoop. 373 void addBlockEntry(BlockT *BB) { 374 Blocks.push_back(BB); 375 } 376 377 /// moveToHeader - This method is used to move BB (which must be part of this 378 /// loop) to be the loop header of the loop (the block that dominates all 379 /// others). 380 void moveToHeader(BlockT *BB) { 381 if (Blocks[0] == BB) return; 382 for (unsigned i = 0; ; ++i) { 383 assert(i != Blocks.size() && "Loop does not contain BB!"); 384 if (Blocks[i] == BB) { 385 Blocks[i] = Blocks[0]; 386 Blocks[0] = BB; 387 return; 388 } 389 } 390 } 391 392 /// removeBlockFromLoop - This removes the specified basic block from the 393 /// current loop, updating the Blocks as appropriate. This does not update 394 /// the mapping in the LoopInfo class. 395 void removeBlockFromLoop(BlockT *BB) { 396 RemoveFromVector(Blocks, BB); 397 } 398 399 /// verifyLoop - Verify loop structure 400 void verifyLoop() const { 401#ifndef NDEBUG 402 assert(!Blocks.empty() && "Loop header is missing"); 403 404 // Sort the blocks vector so that we can use binary search to do quick 405 // lookups. 406 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 407 std::sort(LoopBBs.begin(), LoopBBs.end()); 408 409 // Check the individual blocks. 410 for (block_iterator I = block_begin(), E = block_end(); I != E; ++I) { 411 BlockT *BB = *I; 412 bool HasInsideLoopSuccs = false; 413 bool HasInsideLoopPreds = false; 414 SmallVector<BlockT *, 2> OutsideLoopPreds; 415 416 typedef GraphTraits<BlockT*> BlockTraits; 417 for (typename BlockTraits::ChildIteratorType SI = 418 BlockTraits::child_begin(BB), SE = BlockTraits::child_end(BB); 419 SI != SE; ++SI) 420 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *SI)) { 421 HasInsideLoopSuccs = true; 422 break; 423 } 424 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 425 for (typename InvBlockTraits::ChildIteratorType PI = 426 InvBlockTraits::child_begin(BB), PE = InvBlockTraits::child_end(BB); 427 PI != PE; ++PI) { 428 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *PI)) 429 HasInsideLoopPreds = true; 430 else 431 OutsideLoopPreds.push_back(*PI); 432 } 433 434 if (BB == getHeader()) { 435 assert(!OutsideLoopPreds.empty() && "Loop is unreachable!"); 436 } else if (!OutsideLoopPreds.empty()) { 437 // A non-header loop shouldn't be reachable from outside the loop, 438 // though it is permitted if the predecessor is not itself actually 439 // reachable. 440 BlockT *EntryBB = BB->getParent()->begin(); 441 for (df_iterator<BlockT *> NI = df_begin(EntryBB), 442 NE = df_end(EntryBB); NI != NE; ++NI) 443 for (unsigned i = 0, e = OutsideLoopPreds.size(); i != e; ++i) 444 assert(*NI != OutsideLoopPreds[i] && 445 "Loop has multiple entry points!"); 446 } 447 assert(HasInsideLoopPreds && "Loop block has no in-loop predecessors!"); 448 assert(HasInsideLoopSuccs && "Loop block has no in-loop successors!"); 449 assert(BB != getHeader()->getParent()->begin() && 450 "Loop contains function entry block!"); 451 } 452 453 // Check the subloops. 454 for (iterator I = begin(), E = end(); I != E; ++I) 455 // Each block in each subloop should be contained within this loop. 456 for (block_iterator BI = (*I)->block_begin(), BE = (*I)->block_end(); 457 BI != BE; ++BI) { 458 assert(std::binary_search(LoopBBs.begin(), LoopBBs.end(), *BI) && 459 "Loop does not contain all the blocks of a subloop!"); 460 } 461 462 // Check the parent loop pointer. 463 if (ParentLoop) { 464 assert(std::find(ParentLoop->begin(), ParentLoop->end(), this) != 465 ParentLoop->end() && 466 "Loop is not a subloop of its parent!"); 467 } 468#endif 469 } 470 471 /// verifyLoop - Verify loop structure of this loop and all nested loops. 472 void verifyLoopNest() const { 473 // Verify this loop. 474 verifyLoop(); 475 // Verify the subloops. 476 for (iterator I = begin(), E = end(); I != E; ++I) 477 (*I)->verifyLoopNest(); 478 } 479 480 void print(raw_ostream &OS, unsigned Depth = 0) const { 481 OS.indent(Depth*2) << "Loop at depth " << getLoopDepth() 482 << " containing: "; 483 484 for (unsigned i = 0; i < getBlocks().size(); ++i) { 485 if (i) OS << ","; 486 BlockT *BB = getBlocks()[i]; 487 WriteAsOperand(OS, BB, false); 488 if (BB == getHeader()) OS << "<header>"; 489 if (BB == getLoopLatch()) OS << "<latch>"; 490 if (isLoopExiting(BB)) OS << "<exiting>"; 491 } 492 OS << "\n"; 493 494 for (iterator I = begin(), E = end(); I != E; ++I) 495 (*I)->print(OS, Depth+2); 496 } 497 498protected: 499 friend class LoopInfoBase<BlockT, LoopT>; 500 explicit LoopBase(BlockT *BB) : ParentLoop(0) { 501 Blocks.push_back(BB); 502 } 503}; 504 505class Loop : public LoopBase<BasicBlock, Loop> { 506public: 507 Loop() {} 508 509 /// isLoopInvariant - Return true if the specified value is loop invariant 510 /// 511 bool isLoopInvariant(Value *V) const; 512 513 /// isLoopInvariant - Return true if the specified instruction is 514 /// loop-invariant. 515 /// 516 bool isLoopInvariant(Instruction *I) const; 517 518 /// makeLoopInvariant - If the given value is an instruction inside of the 519 /// loop and it can be hoisted, do so to make it trivially loop-invariant. 520 /// Return true if the value after any hoisting is loop invariant. This 521 /// function can be used as a slightly more aggressive replacement for 522 /// isLoopInvariant. 523 /// 524 /// If InsertPt is specified, it is the point to hoist instructions to. 525 /// If null, the terminator of the loop preheader is used. 526 /// 527 bool makeLoopInvariant(Value *V, bool &Changed, 528 Instruction *InsertPt = 0) const; 529 530 /// makeLoopInvariant - If the given instruction is inside of the 531 /// loop and it can be hoisted, do so to make it trivially loop-invariant. 532 /// Return true if the instruction after any hoisting is loop invariant. This 533 /// function can be used as a slightly more aggressive replacement for 534 /// isLoopInvariant. 535 /// 536 /// If InsertPt is specified, it is the point to hoist instructions to. 537 /// If null, the terminator of the loop preheader is used. 538 /// 539 bool makeLoopInvariant(Instruction *I, bool &Changed, 540 Instruction *InsertPt = 0) const; 541 542 /// getCanonicalInductionVariable - Check to see if the loop has a canonical 543 /// induction variable: an integer recurrence that starts at 0 and increments 544 /// by one each time through the loop. If so, return the phi node that 545 /// corresponds to it. 546 /// 547 /// The IndVarSimplify pass transforms loops to have a canonical induction 548 /// variable. 549 /// 550 PHINode *getCanonicalInductionVariable() const; 551 552 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds 553 /// the canonical induction variable value for the "next" iteration of the 554 /// loop. This always succeeds if getCanonicalInductionVariable succeeds. 555 /// 556 Instruction *getCanonicalInductionVariableIncrement() const; 557 558 /// getTripCount - Return a loop-invariant LLVM value indicating the number of 559 /// times the loop will be executed. Note that this means that the backedge 560 /// of the loop executes N-1 times. If the trip-count cannot be determined, 561 /// this returns null. 562 /// 563 /// The IndVarSimplify pass transforms loops to have a form that this 564 /// function easily understands. 565 /// 566 Value *getTripCount() const; 567 568 /// getSmallConstantTripCount - Returns the trip count of this loop as a 569 /// normal unsigned value, if possible. Returns 0 if the trip count is unknown 570 /// of not constant. Will also return 0 if the trip count is very large 571 /// (>= 2^32) 572 /// 573 /// The IndVarSimplify pass transforms loops to have a form that this 574 /// function easily understands. 575 /// 576 unsigned getSmallConstantTripCount() const; 577 578 /// getSmallConstantTripMultiple - Returns the largest constant divisor of the 579 /// trip count of this loop as a normal unsigned value, if possible. This 580 /// means that the actual trip count is always a multiple of the returned 581 /// value (don't forget the trip count could very well be zero as well!). 582 /// 583 /// Returns 1 if the trip count is unknown or not guaranteed to be the 584 /// multiple of a constant (which is also the case if the trip count is simply 585 /// constant, use getSmallConstantTripCount for that case), Will also return 1 586 /// if the trip count is very large (>= 2^32). 587 unsigned getSmallConstantTripMultiple() const; 588 589 /// isLCSSAForm - Return true if the Loop is in LCSSA form 590 bool isLCSSAForm(DominatorTree &DT) const; 591 592 /// isLoopSimplifyForm - Return true if the Loop is in the form that 593 /// the LoopSimplify form transforms loops to, which is sometimes called 594 /// normal form. 595 bool isLoopSimplifyForm() const; 596 597 /// hasDedicatedExits - Return true if no exit block for the loop 598 /// has a predecessor that is outside the loop. 599 bool hasDedicatedExits() const; 600 601 /// getUniqueExitBlocks - Return all unique successor blocks of this loop. 602 /// These are the blocks _outside of the current loop_ which are branched to. 603 /// This assumes that loop exits are in canonical form. 604 /// 605 void getUniqueExitBlocks(SmallVectorImpl<BasicBlock *> &ExitBlocks) const; 606 607 /// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one 608 /// block, return that block. Otherwise return null. 609 BasicBlock *getUniqueExitBlock() const; 610 611 void dump() const; 612 613private: 614 friend class LoopInfoBase<BasicBlock, Loop>; 615 explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {} 616}; 617 618//===----------------------------------------------------------------------===// 619/// LoopInfo - This class builds and contains all of the top level loop 620/// structures in the specified function. 621/// 622 623template<class BlockT, class LoopT> 624class LoopInfoBase { 625 // BBMap - Mapping of basic blocks to the inner most loop they occur in 626 std::map<BlockT *, LoopT *> BBMap; 627 std::vector<LoopT *> TopLevelLoops; 628 friend class LoopBase<BlockT, LoopT>; 629 630 void operator=(const LoopInfoBase &); // do not implement 631 LoopInfoBase(const LoopInfo &); // do not implement 632public: 633 LoopInfoBase() { } 634 ~LoopInfoBase() { releaseMemory(); } 635 636 void releaseMemory() { 637 for (typename std::vector<LoopT *>::iterator I = 638 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I) 639 delete *I; // Delete all of the loops... 640 641 BBMap.clear(); // Reset internal state of analysis 642 TopLevelLoops.clear(); 643 } 644 645 /// iterator/begin/end - The interface to the top-level loops in the current 646 /// function. 647 /// 648 typedef typename std::vector<LoopT *>::const_iterator iterator; 649 iterator begin() const { return TopLevelLoops.begin(); } 650 iterator end() const { return TopLevelLoops.end(); } 651 bool empty() const { return TopLevelLoops.empty(); } 652 653 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 654 /// block is in no loop (for example the entry node), null is returned. 655 /// 656 LoopT *getLoopFor(const BlockT *BB) const { 657 typename std::map<BlockT *, LoopT *>::const_iterator I= 658 BBMap.find(const_cast<BlockT*>(BB)); 659 return I != BBMap.end() ? I->second : 0; 660 } 661 662 /// operator[] - same as getLoopFor... 663 /// 664 const LoopT *operator[](const BlockT *BB) const { 665 return getLoopFor(BB); 666 } 667 668 /// getLoopDepth - Return the loop nesting level of the specified block. A 669 /// depth of 0 means the block is not inside any loop. 670 /// 671 unsigned getLoopDepth(const BlockT *BB) const { 672 const LoopT *L = getLoopFor(BB); 673 return L ? L->getLoopDepth() : 0; 674 } 675 676 // isLoopHeader - True if the block is a loop header node 677 bool isLoopHeader(BlockT *BB) const { 678 const LoopT *L = getLoopFor(BB); 679 return L && L->getHeader() == BB; 680 } 681 682 /// removeLoop - This removes the specified top-level loop from this loop info 683 /// object. The loop is not deleted, as it will presumably be inserted into 684 /// another loop. 685 LoopT *removeLoop(iterator I) { 686 assert(I != end() && "Cannot remove end iterator!"); 687 LoopT *L = *I; 688 assert(L->getParentLoop() == 0 && "Not a top-level loop!"); 689 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin())); 690 return L; 691 } 692 693 /// changeLoopFor - Change the top-level loop that contains BB to the 694 /// specified loop. This should be used by transformations that restructure 695 /// the loop hierarchy tree. 696 void changeLoopFor(BlockT *BB, LoopT *L) { 697 LoopT *&OldLoop = BBMap[BB]; 698 assert(OldLoop && "Block not in a loop yet!"); 699 OldLoop = L; 700 } 701 702 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 703 /// list with the indicated loop. 704 void changeTopLevelLoop(LoopT *OldLoop, 705 LoopT *NewLoop) { 706 typename std::vector<LoopT *>::iterator I = 707 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop); 708 assert(I != TopLevelLoops.end() && "Old loop not at top level!"); 709 *I = NewLoop; 710 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 && 711 "Loops already embedded into a subloop!"); 712 } 713 714 /// addTopLevelLoop - This adds the specified loop to the collection of 715 /// top-level loops. 716 void addTopLevelLoop(LoopT *New) { 717 assert(New->getParentLoop() == 0 && "Loop already in subloop!"); 718 TopLevelLoops.push_back(New); 719 } 720 721 /// removeBlock - This method completely removes BB from all data structures, 722 /// including all of the Loop objects it is nested in and our mapping from 723 /// BasicBlocks to loops. 724 void removeBlock(BlockT *BB) { 725 typename std::map<BlockT *, LoopT *>::iterator I = BBMap.find(BB); 726 if (I != BBMap.end()) { 727 for (LoopT *L = I->second; L; L = L->getParentLoop()) 728 L->removeBlockFromLoop(BB); 729 730 BBMap.erase(I); 731 } 732 } 733 734 // Internals 735 736 static bool isNotAlreadyContainedIn(const LoopT *SubLoop, 737 const LoopT *ParentLoop) { 738 if (SubLoop == 0) return true; 739 if (SubLoop == ParentLoop) return false; 740 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop); 741 } 742 743 void Calculate(DominatorTreeBase<BlockT> &DT) { 744 BlockT *RootNode = DT.getRootNode()->getBlock(); 745 746 for (df_iterator<BlockT*> NI = df_begin(RootNode), 747 NE = df_end(RootNode); NI != NE; ++NI) 748 if (LoopT *L = ConsiderForLoop(*NI, DT)) 749 TopLevelLoops.push_back(L); 750 } 751 752 LoopT *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) { 753 if (BBMap.find(BB) != BBMap.end()) return 0;// Haven't processed this node? 754 755 std::vector<BlockT *> TodoStack; 756 757 // Scan the predecessors of BB, checking to see if BB dominates any of 758 // them. This identifies backedges which target this node... 759 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 760 for (typename InvBlockTraits::ChildIteratorType I = 761 InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB); 762 I != E; ++I) { 763 typename InvBlockTraits::NodeType *N = *I; 764 if (DT.dominates(BB, N)) // If BB dominates its predecessor... 765 TodoStack.push_back(N); 766 } 767 768 if (TodoStack.empty()) return 0; // No backedges to this block... 769 770 // Create a new loop to represent this basic block... 771 LoopT *L = new LoopT(BB); 772 BBMap[BB] = L; 773 774 BlockT *EntryBlock = BB->getParent()->begin(); 775 776 while (!TodoStack.empty()) { // Process all the nodes in the loop 777 BlockT *X = TodoStack.back(); 778 TodoStack.pop_back(); 779 780 if (!L->contains(X) && // As of yet unprocessed?? 781 DT.dominates(EntryBlock, X)) { // X is reachable from entry block? 782 // Check to see if this block already belongs to a loop. If this occurs 783 // then we have a case where a loop that is supposed to be a child of 784 // the current loop was processed before the current loop. When this 785 // occurs, this child loop gets added to a part of the current loop, 786 // making it a sibling to the current loop. We have to reparent this 787 // loop. 788 if (LoopT *SubLoop = 789 const_cast<LoopT *>(getLoopFor(X))) 790 if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){ 791 // Remove the subloop from its current parent... 792 assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L); 793 LoopT *SLP = SubLoop->ParentLoop; // SubLoopParent 794 typename std::vector<LoopT *>::iterator I = 795 std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop); 796 assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?"); 797 SLP->SubLoops.erase(I); // Remove from parent... 798 799 // Add the subloop to THIS loop... 800 SubLoop->ParentLoop = L; 801 L->SubLoops.push_back(SubLoop); 802 } 803 804 // Normal case, add the block to our loop... 805 L->Blocks.push_back(X); 806 807 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 808 809 // Add all of the predecessors of X to the end of the work stack... 810 TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X), 811 InvBlockTraits::child_end(X)); 812 } 813 } 814 815 // If there are any loops nested within this loop, create them now! 816 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 817 E = L->Blocks.end(); I != E; ++I) 818 if (LoopT *NewLoop = ConsiderForLoop(*I, DT)) { 819 L->SubLoops.push_back(NewLoop); 820 NewLoop->ParentLoop = L; 821 } 822 823 // Add the basic blocks that comprise this loop to the BBMap so that this 824 // loop can be found for them. 825 // 826 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 827 E = L->Blocks.end(); I != E; ++I) 828 BBMap.insert(std::make_pair(*I, L)); 829 830 // Now that we have a list of all of the child loops of this loop, check to 831 // see if any of them should actually be nested inside of each other. We 832 // can accidentally pull loops our of their parents, so we must make sure to 833 // organize the loop nests correctly now. 834 { 835 std::map<BlockT *, LoopT *> ContainingLoops; 836 for (unsigned i = 0; i != L->SubLoops.size(); ++i) { 837 LoopT *Child = L->SubLoops[i]; 838 assert(Child->getParentLoop() == L && "Not proper child loop?"); 839 840 if (LoopT *ContainingLoop = ContainingLoops[Child->getHeader()]) { 841 // If there is already a loop which contains this loop, move this loop 842 // into the containing loop. 843 MoveSiblingLoopInto(Child, ContainingLoop); 844 --i; // The loop got removed from the SubLoops list. 845 } else { 846 // This is currently considered to be a top-level loop. Check to see 847 // if any of the contained blocks are loop headers for subloops we 848 // have already processed. 849 for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) { 850 LoopT *&BlockLoop = ContainingLoops[Child->Blocks[b]]; 851 if (BlockLoop == 0) { // Child block not processed yet... 852 BlockLoop = Child; 853 } else if (BlockLoop != Child) { 854 LoopT *SubLoop = BlockLoop; 855 // Reparent all of the blocks which used to belong to BlockLoops 856 for (unsigned j = 0, f = SubLoop->Blocks.size(); j != f; ++j) 857 ContainingLoops[SubLoop->Blocks[j]] = Child; 858 859 // There is already a loop which contains this block, that means 860 // that we should reparent the loop which the block is currently 861 // considered to belong to to be a child of this loop. 862 MoveSiblingLoopInto(SubLoop, Child); 863 --i; // We just shrunk the SubLoops list. 864 } 865 } 866 } 867 } 868 } 869 870 return L; 871 } 872 873 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside 874 /// of the NewParent Loop, instead of being a sibling of it. 875 void MoveSiblingLoopInto(LoopT *NewChild, 876 LoopT *NewParent) { 877 LoopT *OldParent = NewChild->getParentLoop(); 878 assert(OldParent && OldParent == NewParent->getParentLoop() && 879 NewChild != NewParent && "Not sibling loops!"); 880 881 // Remove NewChild from being a child of OldParent 882 typename std::vector<LoopT *>::iterator I = 883 std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(), 884 NewChild); 885 assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??"); 886 OldParent->SubLoops.erase(I); // Remove from parent's subloops list 887 NewChild->ParentLoop = 0; 888 889 InsertLoopInto(NewChild, NewParent); 890 } 891 892 /// InsertLoopInto - This inserts loop L into the specified parent loop. If 893 /// the parent loop contains a loop which should contain L, the loop gets 894 /// inserted into L instead. 895 void InsertLoopInto(LoopT *L, LoopT *Parent) { 896 BlockT *LHeader = L->getHeader(); 897 assert(Parent->contains(LHeader) && 898 "This loop should not be inserted here!"); 899 900 // Check to see if it belongs in a child loop... 901 for (unsigned i = 0, e = static_cast<unsigned>(Parent->SubLoops.size()); 902 i != e; ++i) 903 if (Parent->SubLoops[i]->contains(LHeader)) { 904 InsertLoopInto(L, Parent->SubLoops[i]); 905 return; 906 } 907 908 // If not, insert it here! 909 Parent->SubLoops.push_back(L); 910 L->ParentLoop = Parent; 911 } 912 913 // Debugging 914 915 void print(raw_ostream &OS) const { 916 for (unsigned i = 0; i < TopLevelLoops.size(); ++i) 917 TopLevelLoops[i]->print(OS); 918 #if 0 919 for (std::map<BasicBlock*, LoopT*>::const_iterator I = BBMap.begin(), 920 E = BBMap.end(); I != E; ++I) 921 OS << "BB '" << I->first->getName() << "' level = " 922 << I->second->getLoopDepth() << "\n"; 923 #endif 924 } 925}; 926 927class LoopInfo : public FunctionPass { 928 LoopInfoBase<BasicBlock, Loop> LI; 929 friend class LoopBase<BasicBlock, Loop>; 930 931 void operator=(const LoopInfo &); // do not implement 932 LoopInfo(const LoopInfo &); // do not implement 933public: 934 static char ID; // Pass identification, replacement for typeid 935 936 LoopInfo() : FunctionPass(&ID) {} 937 938 LoopInfoBase<BasicBlock, Loop>& getBase() { return LI; } 939 940 /// iterator/begin/end - The interface to the top-level loops in the current 941 /// function. 942 /// 943 typedef LoopInfoBase<BasicBlock, Loop>::iterator iterator; 944 inline iterator begin() const { return LI.begin(); } 945 inline iterator end() const { return LI.end(); } 946 bool empty() const { return LI.empty(); } 947 948 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 949 /// block is in no loop (for example the entry node), null is returned. 950 /// 951 inline Loop *getLoopFor(const BasicBlock *BB) const { 952 return LI.getLoopFor(BB); 953 } 954 955 /// operator[] - same as getLoopFor... 956 /// 957 inline const Loop *operator[](const BasicBlock *BB) const { 958 return LI.getLoopFor(BB); 959 } 960 961 /// getLoopDepth - Return the loop nesting level of the specified block. A 962 /// depth of 0 means the block is not inside any loop. 963 /// 964 inline unsigned getLoopDepth(const BasicBlock *BB) const { 965 return LI.getLoopDepth(BB); 966 } 967 968 // isLoopHeader - True if the block is a loop header node 969 inline bool isLoopHeader(BasicBlock *BB) const { 970 return LI.isLoopHeader(BB); 971 } 972 973 /// runOnFunction - Calculate the natural loop information. 974 /// 975 virtual bool runOnFunction(Function &F); 976 977 virtual void verifyAnalysis() const; 978 979 virtual void releaseMemory() { LI.releaseMemory(); } 980 981 virtual void print(raw_ostream &O, const Module* M = 0) const; 982 983 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 984 985 /// removeLoop - This removes the specified top-level loop from this loop info 986 /// object. The loop is not deleted, as it will presumably be inserted into 987 /// another loop. 988 inline Loop *removeLoop(iterator I) { return LI.removeLoop(I); } 989 990 /// changeLoopFor - Change the top-level loop that contains BB to the 991 /// specified loop. This should be used by transformations that restructure 992 /// the loop hierarchy tree. 993 inline void changeLoopFor(BasicBlock *BB, Loop *L) { 994 LI.changeLoopFor(BB, L); 995 } 996 997 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 998 /// list with the indicated loop. 999 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) { 1000 LI.changeTopLevelLoop(OldLoop, NewLoop); 1001 } 1002 1003 /// addTopLevelLoop - This adds the specified loop to the collection of 1004 /// top-level loops. 1005 inline void addTopLevelLoop(Loop *New) { 1006 LI.addTopLevelLoop(New); 1007 } 1008 1009 /// removeBlock - This method completely removes BB from all data structures, 1010 /// including all of the Loop objects it is nested in and our mapping from 1011 /// BasicBlocks to loops. 1012 void removeBlock(BasicBlock *BB) { 1013 LI.removeBlock(BB); 1014 } 1015}; 1016 1017 1018// Allow clients to walk the list of nested loops... 1019template <> struct GraphTraits<const Loop*> { 1020 typedef const Loop NodeType; 1021 typedef LoopInfo::iterator ChildIteratorType; 1022 1023 static NodeType *getEntryNode(const Loop *L) { return L; } 1024 static inline ChildIteratorType child_begin(NodeType *N) { 1025 return N->begin(); 1026 } 1027 static inline ChildIteratorType child_end(NodeType *N) { 1028 return N->end(); 1029 } 1030}; 1031 1032template <> struct GraphTraits<Loop*> { 1033 typedef Loop NodeType; 1034 typedef LoopInfo::iterator ChildIteratorType; 1035 1036 static NodeType *getEntryNode(Loop *L) { return L; } 1037 static inline ChildIteratorType child_begin(NodeType *N) { 1038 return N->begin(); 1039 } 1040 static inline ChildIteratorType child_end(NodeType *N) { 1041 return N->end(); 1042 } 1043}; 1044 1045template<class BlockT, class LoopT> 1046void 1047LoopBase<BlockT, LoopT>::addBasicBlockToLoop(BlockT *NewBB, 1048 LoopInfoBase<BlockT, LoopT> &LIB) { 1049 assert((Blocks.empty() || LIB[getHeader()] == this) && 1050 "Incorrect LI specified for this loop!"); 1051 assert(NewBB && "Cannot add a null basic block to the loop!"); 1052 assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!"); 1053 1054 LoopT *L = static_cast<LoopT *>(this); 1055 1056 // Add the loop mapping to the LoopInfo object... 1057 LIB.BBMap[NewBB] = L; 1058 1059 // Add the basic block to this loop and all parent loops... 1060 while (L) { 1061 L->Blocks.push_back(NewBB); 1062 L = L->getParentLoop(); 1063 } 1064} 1065 1066} // End llvm namespace 1067 1068#endif 1069