LoopInfo.h revision b14bc1f6f82c7f650226f39ed0256d8189eb2a1b
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 = 0; 260 261 // Loop over the predecessors of the header node... 262 BlockT *Header = getHeader(); 263 typedef GraphTraits<BlockT*> BlockTraits; 264 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 265 for (typename InvBlockTraits::ChildIteratorType PI = 266 InvBlockTraits::child_begin(Header), 267 PE = InvBlockTraits::child_end(Header); PI != PE; ++PI) 268 if (!contains(*PI)) { // If the block is not in the loop... 269 if (Out && Out != *PI) 270 return 0; // Multiple predecessors outside the loop 271 Out = *PI; 272 } 273 274 // Make sure there is only one exit out of the preheader. 275 assert(Out && "Header of loop has no predecessors from outside loop?"); 276 typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out); 277 ++SI; 278 if (SI != BlockTraits::child_end(Out)) 279 return 0; // Multiple exits from the block, must not be a preheader. 280 281 // If there is exactly one preheader, return it. If there was zero, then 282 // Out is still null. 283 return Out; 284 } 285 286 /// getLoopLatch - If there is a single latch block for this loop, return it. 287 /// A latch block is a block that contains a branch back to the header. 288 BlockT *getLoopLatch() const { 289 BlockT *Header = getHeader(); 290 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 291 typename InvBlockTraits::ChildIteratorType PI = 292 InvBlockTraits::child_begin(Header); 293 typename InvBlockTraits::ChildIteratorType PE = 294 InvBlockTraits::child_end(Header); 295 BlockT *Latch = 0; 296 for (; PI != PE; ++PI) 297 if (contains(*PI)) { 298 if (Latch) return 0; 299 Latch = *PI; 300 } 301 302 return Latch; 303 } 304 305 //===--------------------------------------------------------------------===// 306 // APIs for updating loop information after changing the CFG 307 // 308 309 /// addBasicBlockToLoop - This method is used by other analyses to update loop 310 /// information. NewBB is set to be a new member of the current loop. 311 /// Because of this, it is added as a member of all parent loops, and is added 312 /// to the specified LoopInfo object as being in the current basic block. It 313 /// is not valid to replace the loop header with this method. 314 /// 315 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LI); 316 317 /// replaceChildLoopWith - This is used when splitting loops up. It replaces 318 /// the OldChild entry in our children list with NewChild, and updates the 319 /// parent pointer of OldChild to be null and the NewChild to be this loop. 320 /// This updates the loop depth of the new child. 321 void replaceChildLoopWith(LoopT *OldChild, 322 LoopT *NewChild) { 323 assert(OldChild->ParentLoop == this && "This loop is already broken!"); 324 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 325 typename std::vector<LoopT *>::iterator I = 326 std::find(SubLoops.begin(), SubLoops.end(), OldChild); 327 assert(I != SubLoops.end() && "OldChild not in loop!"); 328 *I = NewChild; 329 OldChild->ParentLoop = 0; 330 NewChild->ParentLoop = static_cast<LoopT *>(this); 331 } 332 333 /// addChildLoop - Add the specified loop to be a child of this loop. This 334 /// updates the loop depth of the new child. 335 /// 336 void addChildLoop(LoopT *NewChild) { 337 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 338 NewChild->ParentLoop = static_cast<LoopT *>(this); 339 SubLoops.push_back(NewChild); 340 } 341 342 /// removeChildLoop - This removes the specified child from being a subloop of 343 /// this loop. The loop is not deleted, as it will presumably be inserted 344 /// into another loop. 345 LoopT *removeChildLoop(iterator I) { 346 assert(I != SubLoops.end() && "Cannot remove end iterator!"); 347 LoopT *Child = *I; 348 assert(Child->ParentLoop == this && "Child is not a child of this loop!"); 349 SubLoops.erase(SubLoops.begin()+(I-begin())); 350 Child->ParentLoop = 0; 351 return Child; 352 } 353 354 /// addBlockEntry - This adds a basic block directly to the basic block list. 355 /// This should only be used by transformations that create new loops. Other 356 /// transformations should use addBasicBlockToLoop. 357 void addBlockEntry(BlockT *BB) { 358 Blocks.push_back(BB); 359 } 360 361 /// moveToHeader - This method is used to move BB (which must be part of this 362 /// loop) to be the loop header of the loop (the block that dominates all 363 /// others). 364 void moveToHeader(BlockT *BB) { 365 if (Blocks[0] == BB) return; 366 for (unsigned i = 0; ; ++i) { 367 assert(i != Blocks.size() && "Loop does not contain BB!"); 368 if (Blocks[i] == BB) { 369 Blocks[i] = Blocks[0]; 370 Blocks[0] = BB; 371 return; 372 } 373 } 374 } 375 376 /// removeBlockFromLoop - This removes the specified basic block from the 377 /// current loop, updating the Blocks as appropriate. This does not update 378 /// the mapping in the LoopInfo class. 379 void removeBlockFromLoop(BlockT *BB) { 380 RemoveFromVector(Blocks, BB); 381 } 382 383 /// verifyLoop - Verify loop structure 384 void verifyLoop() const { 385#ifndef NDEBUG 386 assert(!Blocks.empty() && "Loop header is missing"); 387 388 // Sort the blocks vector so that we can use binary search to do quick 389 // lookups. 390 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 391 std::sort(LoopBBs.begin(), LoopBBs.end()); 392 393 // Check the individual blocks. 394 for (block_iterator I = block_begin(), E = block_end(); I != E; ++I) { 395 BlockT *BB = *I; 396 bool HasInsideLoopSuccs = false; 397 bool HasInsideLoopPreds = false; 398 SmallVector<BlockT *, 2> OutsideLoopPreds; 399 400 typedef GraphTraits<BlockT*> BlockTraits; 401 for (typename BlockTraits::ChildIteratorType SI = 402 BlockTraits::child_begin(BB), SE = BlockTraits::child_end(BB); 403 SI != SE; ++SI) 404 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *SI)) { 405 HasInsideLoopSuccs = true; 406 break; 407 } 408 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 409 for (typename InvBlockTraits::ChildIteratorType PI = 410 InvBlockTraits::child_begin(BB), PE = InvBlockTraits::child_end(BB); 411 PI != PE; ++PI) { 412 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *PI)) 413 HasInsideLoopPreds = true; 414 else 415 OutsideLoopPreds.push_back(*PI); 416 } 417 418 if (BB == getHeader()) { 419 assert(!OutsideLoopPreds.empty() && "Loop is unreachable!"); 420 } else if (!OutsideLoopPreds.empty()) { 421 // A non-header loop shouldn't be reachable from outside the loop, 422 // though it is permitted if the predecessor is not itself actually 423 // reachable. 424 BlockT *EntryBB = BB->getParent()->begin(); 425 for (df_iterator<BlockT *> NI = df_begin(EntryBB), 426 NE = df_end(EntryBB); NI != NE; ++NI) 427 for (unsigned i = 0, e = OutsideLoopPreds.size(); i != e; ++i) 428 assert(*NI != OutsideLoopPreds[i] && 429 "Loop has multiple entry points!"); 430 } 431 assert(HasInsideLoopPreds && "Loop block has no in-loop predecessors!"); 432 assert(HasInsideLoopSuccs && "Loop block has no in-loop successors!"); 433 assert(BB != getHeader()->getParent()->begin() && 434 "Loop contains function entry block!"); 435 } 436 437 // Check the subloops. 438 for (iterator I = begin(), E = end(); I != E; ++I) 439 // Each block in each subloop should be contained within this loop. 440 for (block_iterator BI = (*I)->block_begin(), BE = (*I)->block_end(); 441 BI != BE; ++BI) { 442 assert(std::binary_search(LoopBBs.begin(), LoopBBs.end(), *BI) && 443 "Loop does not contain all the blocks of a subloop!"); 444 } 445 446 // Check the parent loop pointer. 447 if (ParentLoop) { 448 assert(std::find(ParentLoop->begin(), ParentLoop->end(), this) != 449 ParentLoop->end() && 450 "Loop is not a subloop of its parent!"); 451 } 452#endif 453 } 454 455 /// verifyLoop - Verify loop structure of this loop and all nested loops. 456 void verifyLoopNest() const { 457 // Verify this loop. 458 verifyLoop(); 459 // Verify the subloops. 460 for (iterator I = begin(), E = end(); I != E; ++I) 461 (*I)->verifyLoopNest(); 462 } 463 464 void print(raw_ostream &OS, unsigned Depth = 0) const { 465 OS.indent(Depth*2) << "Loop at depth " << getLoopDepth() 466 << " containing: "; 467 468 for (unsigned i = 0; i < getBlocks().size(); ++i) { 469 if (i) OS << ","; 470 BlockT *BB = getBlocks()[i]; 471 WriteAsOperand(OS, BB, false); 472 if (BB == getHeader()) OS << "<header>"; 473 if (BB == getLoopLatch()) OS << "<latch>"; 474 if (isLoopExiting(BB)) OS << "<exiting>"; 475 } 476 OS << "\n"; 477 478 for (iterator I = begin(), E = end(); I != E; ++I) 479 (*I)->print(OS, Depth+2); 480 } 481 482protected: 483 friend class LoopInfoBase<BlockT, LoopT>; 484 explicit LoopBase(BlockT *BB) : ParentLoop(0) { 485 Blocks.push_back(BB); 486 } 487}; 488 489class Loop : public LoopBase<BasicBlock, Loop> { 490public: 491 Loop() {} 492 493 /// isLoopInvariant - Return true if the specified value is loop invariant 494 /// 495 bool isLoopInvariant(Value *V) const; 496 497 /// isLoopInvariant - Return true if the specified instruction is 498 /// loop-invariant. 499 /// 500 bool isLoopInvariant(Instruction *I) const; 501 502 /// makeLoopInvariant - If the given value is an instruction inside of the 503 /// loop and it can be hoisted, do so to make it trivially loop-invariant. 504 /// Return true if the value after any hoisting is loop invariant. This 505 /// function can be used as a slightly more aggressive replacement for 506 /// isLoopInvariant. 507 /// 508 /// If InsertPt is specified, it is the point to hoist instructions to. 509 /// If null, the terminator of the loop preheader is used. 510 /// 511 bool makeLoopInvariant(Value *V, bool &Changed, 512 Instruction *InsertPt = 0) const; 513 514 /// makeLoopInvariant - If the given instruction is inside of the 515 /// loop and it can be hoisted, do so to make it trivially loop-invariant. 516 /// Return true if the instruction after any hoisting is loop invariant. This 517 /// function can be used as a slightly more aggressive replacement for 518 /// isLoopInvariant. 519 /// 520 /// If InsertPt is specified, it is the point to hoist instructions to. 521 /// If null, the terminator of the loop preheader is used. 522 /// 523 bool makeLoopInvariant(Instruction *I, bool &Changed, 524 Instruction *InsertPt = 0) const; 525 526 /// getCanonicalInductionVariable - Check to see if the loop has a canonical 527 /// induction variable: an integer recurrence that starts at 0 and increments 528 /// by one each time through the loop. If so, return the phi node that 529 /// corresponds to it. 530 /// 531 /// The IndVarSimplify pass transforms loops to have a canonical induction 532 /// variable. 533 /// 534 PHINode *getCanonicalInductionVariable() const; 535 536 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds 537 /// the canonical induction variable value for the "next" iteration of the 538 /// loop. This always succeeds if getCanonicalInductionVariable succeeds. 539 /// 540 Instruction *getCanonicalInductionVariableIncrement() const; 541 542 /// getTripCount - Return a loop-invariant LLVM value indicating the number of 543 /// times the loop will be executed. Note that this means that the backedge 544 /// of the loop executes N-1 times. If the trip-count cannot be determined, 545 /// this returns null. 546 /// 547 /// The IndVarSimplify pass transforms loops to have a form that this 548 /// function easily understands. 549 /// 550 Value *getTripCount() const; 551 552 /// getSmallConstantTripCount - Returns the trip count of this loop as a 553 /// normal unsigned value, if possible. Returns 0 if the trip count is unknown 554 /// of not constant. Will also return 0 if the trip count is very large 555 /// (>= 2^32) 556 /// 557 /// The IndVarSimplify pass transforms loops to have a form that this 558 /// function easily understands. 559 /// 560 unsigned getSmallConstantTripCount() const; 561 562 /// getSmallConstantTripMultiple - Returns the largest constant divisor of the 563 /// trip count of this loop as a normal unsigned value, if possible. This 564 /// means that the actual trip count is always a multiple of the returned 565 /// value (don't forget the trip count could very well be zero as well!). 566 /// 567 /// Returns 1 if the trip count is unknown or not guaranteed to be the 568 /// multiple of a constant (which is also the case if the trip count is simply 569 /// constant, use getSmallConstantTripCount for that case), Will also return 1 570 /// if the trip count is very large (>= 2^32). 571 unsigned getSmallConstantTripMultiple() const; 572 573 /// isLCSSAForm - Return true if the Loop is in LCSSA form 574 bool isLCSSAForm() const; 575 576 /// isLoopSimplifyForm - Return true if the Loop is in the form that 577 /// the LoopSimplify form transforms loops to, which is sometimes called 578 /// normal form. 579 bool isLoopSimplifyForm() const; 580 581 /// hasDedicatedExits - Return true if no exit block for the loop 582 /// has a predecessor that is outside the loop. 583 bool hasDedicatedExits() const; 584 585 /// getUniqueExitBlocks - Return all unique successor blocks of this loop. 586 /// These are the blocks _outside of the current loop_ which are branched to. 587 /// This assumes that loop exits are in canonical form. 588 /// 589 void getUniqueExitBlocks(SmallVectorImpl<BasicBlock *> &ExitBlocks) const; 590 591 /// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one 592 /// block, return that block. Otherwise return null. 593 BasicBlock *getUniqueExitBlock() const; 594 595 void dump() const; 596 597private: 598 friend class LoopInfoBase<BasicBlock, Loop>; 599 explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {} 600}; 601 602//===----------------------------------------------------------------------===// 603/// LoopInfo - This class builds and contains all of the top level loop 604/// structures in the specified function. 605/// 606 607template<class BlockT, class LoopT> 608class LoopInfoBase { 609 // BBMap - Mapping of basic blocks to the inner most loop they occur in 610 std::map<BlockT *, LoopT *> BBMap; 611 std::vector<LoopT *> TopLevelLoops; 612 friend class LoopBase<BlockT, LoopT>; 613 614 void operator=(const LoopInfoBase &); // do not implement 615 LoopInfoBase(const LoopInfo &); // do not implement 616public: 617 LoopInfoBase() { } 618 ~LoopInfoBase() { releaseMemory(); } 619 620 void releaseMemory() { 621 for (typename std::vector<LoopT *>::iterator I = 622 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I) 623 delete *I; // Delete all of the loops... 624 625 BBMap.clear(); // Reset internal state of analysis 626 TopLevelLoops.clear(); 627 } 628 629 /// iterator/begin/end - The interface to the top-level loops in the current 630 /// function. 631 /// 632 typedef typename std::vector<LoopT *>::const_iterator iterator; 633 iterator begin() const { return TopLevelLoops.begin(); } 634 iterator end() const { return TopLevelLoops.end(); } 635 bool empty() const { return TopLevelLoops.empty(); } 636 637 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 638 /// block is in no loop (for example the entry node), null is returned. 639 /// 640 LoopT *getLoopFor(const BlockT *BB) const { 641 typename std::map<BlockT *, LoopT *>::const_iterator I= 642 BBMap.find(const_cast<BlockT*>(BB)); 643 return I != BBMap.end() ? I->second : 0; 644 } 645 646 /// operator[] - same as getLoopFor... 647 /// 648 const LoopT *operator[](const BlockT *BB) const { 649 return getLoopFor(BB); 650 } 651 652 /// getLoopDepth - Return the loop nesting level of the specified block. A 653 /// depth of 0 means the block is not inside any loop. 654 /// 655 unsigned getLoopDepth(const BlockT *BB) const { 656 const LoopT *L = getLoopFor(BB); 657 return L ? L->getLoopDepth() : 0; 658 } 659 660 // isLoopHeader - True if the block is a loop header node 661 bool isLoopHeader(BlockT *BB) const { 662 const LoopT *L = getLoopFor(BB); 663 return L && L->getHeader() == BB; 664 } 665 666 /// removeLoop - This removes the specified top-level loop from this loop info 667 /// object. The loop is not deleted, as it will presumably be inserted into 668 /// another loop. 669 LoopT *removeLoop(iterator I) { 670 assert(I != end() && "Cannot remove end iterator!"); 671 LoopT *L = *I; 672 assert(L->getParentLoop() == 0 && "Not a top-level loop!"); 673 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin())); 674 return L; 675 } 676 677 /// changeLoopFor - Change the top-level loop that contains BB to the 678 /// specified loop. This should be used by transformations that restructure 679 /// the loop hierarchy tree. 680 void changeLoopFor(BlockT *BB, LoopT *L) { 681 LoopT *&OldLoop = BBMap[BB]; 682 assert(OldLoop && "Block not in a loop yet!"); 683 OldLoop = L; 684 } 685 686 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 687 /// list with the indicated loop. 688 void changeTopLevelLoop(LoopT *OldLoop, 689 LoopT *NewLoop) { 690 typename std::vector<LoopT *>::iterator I = 691 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop); 692 assert(I != TopLevelLoops.end() && "Old loop not at top level!"); 693 *I = NewLoop; 694 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 && 695 "Loops already embedded into a subloop!"); 696 } 697 698 /// addTopLevelLoop - This adds the specified loop to the collection of 699 /// top-level loops. 700 void addTopLevelLoop(LoopT *New) { 701 assert(New->getParentLoop() == 0 && "Loop already in subloop!"); 702 TopLevelLoops.push_back(New); 703 } 704 705 /// removeBlock - This method completely removes BB from all data structures, 706 /// including all of the Loop objects it is nested in and our mapping from 707 /// BasicBlocks to loops. 708 void removeBlock(BlockT *BB) { 709 typename std::map<BlockT *, LoopT *>::iterator I = BBMap.find(BB); 710 if (I != BBMap.end()) { 711 for (LoopT *L = I->second; L; L = L->getParentLoop()) 712 L->removeBlockFromLoop(BB); 713 714 BBMap.erase(I); 715 } 716 } 717 718 // Internals 719 720 static bool isNotAlreadyContainedIn(const LoopT *SubLoop, 721 const LoopT *ParentLoop) { 722 if (SubLoop == 0) return true; 723 if (SubLoop == ParentLoop) return false; 724 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop); 725 } 726 727 void Calculate(DominatorTreeBase<BlockT> &DT) { 728 BlockT *RootNode = DT.getRootNode()->getBlock(); 729 730 for (df_iterator<BlockT*> NI = df_begin(RootNode), 731 NE = df_end(RootNode); NI != NE; ++NI) 732 if (LoopT *L = ConsiderForLoop(*NI, DT)) 733 TopLevelLoops.push_back(L); 734 } 735 736 LoopT *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) { 737 if (BBMap.find(BB) != BBMap.end()) return 0;// Haven't processed this node? 738 739 std::vector<BlockT *> TodoStack; 740 741 // Scan the predecessors of BB, checking to see if BB dominates any of 742 // them. This identifies backedges which target this node... 743 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 744 for (typename InvBlockTraits::ChildIteratorType I = 745 InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB); 746 I != E; ++I) 747 if (DT.dominates(BB, *I)) // If BB dominates its predecessor... 748 TodoStack.push_back(*I); 749 750 if (TodoStack.empty()) return 0; // No backedges to this block... 751 752 // Create a new loop to represent this basic block... 753 LoopT *L = new LoopT(BB); 754 BBMap[BB] = L; 755 756 BlockT *EntryBlock = BB->getParent()->begin(); 757 758 while (!TodoStack.empty()) { // Process all the nodes in the loop 759 BlockT *X = TodoStack.back(); 760 TodoStack.pop_back(); 761 762 if (!L->contains(X) && // As of yet unprocessed?? 763 DT.dominates(EntryBlock, X)) { // X is reachable from entry block? 764 // Check to see if this block already belongs to a loop. If this occurs 765 // then we have a case where a loop that is supposed to be a child of 766 // the current loop was processed before the current loop. When this 767 // occurs, this child loop gets added to a part of the current loop, 768 // making it a sibling to the current loop. We have to reparent this 769 // loop. 770 if (LoopT *SubLoop = 771 const_cast<LoopT *>(getLoopFor(X))) 772 if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){ 773 // Remove the subloop from its current parent... 774 assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L); 775 LoopT *SLP = SubLoop->ParentLoop; // SubLoopParent 776 typename std::vector<LoopT *>::iterator I = 777 std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop); 778 assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?"); 779 SLP->SubLoops.erase(I); // Remove from parent... 780 781 // Add the subloop to THIS loop... 782 SubLoop->ParentLoop = L; 783 L->SubLoops.push_back(SubLoop); 784 } 785 786 // Normal case, add the block to our loop... 787 L->Blocks.push_back(X); 788 789 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 790 791 // Add all of the predecessors of X to the end of the work stack... 792 TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X), 793 InvBlockTraits::child_end(X)); 794 } 795 } 796 797 // If there are any loops nested within this loop, create them now! 798 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 799 E = L->Blocks.end(); I != E; ++I) 800 if (LoopT *NewLoop = ConsiderForLoop(*I, DT)) { 801 L->SubLoops.push_back(NewLoop); 802 NewLoop->ParentLoop = L; 803 } 804 805 // Add the basic blocks that comprise this loop to the BBMap so that this 806 // loop can be found for them. 807 // 808 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 809 E = L->Blocks.end(); I != E; ++I) 810 BBMap.insert(std::make_pair(*I, L)); 811 812 // Now that we have a list of all of the child loops of this loop, check to 813 // see if any of them should actually be nested inside of each other. We 814 // can accidentally pull loops our of their parents, so we must make sure to 815 // organize the loop nests correctly now. 816 { 817 std::map<BlockT *, LoopT *> ContainingLoops; 818 for (unsigned i = 0; i != L->SubLoops.size(); ++i) { 819 LoopT *Child = L->SubLoops[i]; 820 assert(Child->getParentLoop() == L && "Not proper child loop?"); 821 822 if (LoopT *ContainingLoop = ContainingLoops[Child->getHeader()]) { 823 // If there is already a loop which contains this loop, move this loop 824 // into the containing loop. 825 MoveSiblingLoopInto(Child, ContainingLoop); 826 --i; // The loop got removed from the SubLoops list. 827 } else { 828 // This is currently considered to be a top-level loop. Check to see 829 // if any of the contained blocks are loop headers for subloops we 830 // have already processed. 831 for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) { 832 LoopT *&BlockLoop = ContainingLoops[Child->Blocks[b]]; 833 if (BlockLoop == 0) { // Child block not processed yet... 834 BlockLoop = Child; 835 } else if (BlockLoop != Child) { 836 LoopT *SubLoop = BlockLoop; 837 // Reparent all of the blocks which used to belong to BlockLoops 838 for (unsigned j = 0, e = SubLoop->Blocks.size(); j != e; ++j) 839 ContainingLoops[SubLoop->Blocks[j]] = Child; 840 841 // There is already a loop which contains this block, that means 842 // that we should reparent the loop which the block is currently 843 // considered to belong to to be a child of this loop. 844 MoveSiblingLoopInto(SubLoop, Child); 845 --i; // We just shrunk the SubLoops list. 846 } 847 } 848 } 849 } 850 } 851 852 return L; 853 } 854 855 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside 856 /// of the NewParent Loop, instead of being a sibling of it. 857 void MoveSiblingLoopInto(LoopT *NewChild, 858 LoopT *NewParent) { 859 LoopT *OldParent = NewChild->getParentLoop(); 860 assert(OldParent && OldParent == NewParent->getParentLoop() && 861 NewChild != NewParent && "Not sibling loops!"); 862 863 // Remove NewChild from being a child of OldParent 864 typename std::vector<LoopT *>::iterator I = 865 std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(), 866 NewChild); 867 assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??"); 868 OldParent->SubLoops.erase(I); // Remove from parent's subloops list 869 NewChild->ParentLoop = 0; 870 871 InsertLoopInto(NewChild, NewParent); 872 } 873 874 /// InsertLoopInto - This inserts loop L into the specified parent loop. If 875 /// the parent loop contains a loop which should contain L, the loop gets 876 /// inserted into L instead. 877 void InsertLoopInto(LoopT *L, LoopT *Parent) { 878 BlockT *LHeader = L->getHeader(); 879 assert(Parent->contains(LHeader) && 880 "This loop should not be inserted here!"); 881 882 // Check to see if it belongs in a child loop... 883 for (unsigned i = 0, e = static_cast<unsigned>(Parent->SubLoops.size()); 884 i != e; ++i) 885 if (Parent->SubLoops[i]->contains(LHeader)) { 886 InsertLoopInto(L, Parent->SubLoops[i]); 887 return; 888 } 889 890 // If not, insert it here! 891 Parent->SubLoops.push_back(L); 892 L->ParentLoop = Parent; 893 } 894 895 // Debugging 896 897 void print(raw_ostream &OS) const { 898 for (unsigned i = 0; i < TopLevelLoops.size(); ++i) 899 TopLevelLoops[i]->print(OS); 900 #if 0 901 for (std::map<BasicBlock*, LoopT*>::const_iterator I = BBMap.begin(), 902 E = BBMap.end(); I != E; ++I) 903 OS << "BB '" << I->first->getName() << "' level = " 904 << I->second->getLoopDepth() << "\n"; 905 #endif 906 } 907}; 908 909class LoopInfo : public FunctionPass { 910 LoopInfoBase<BasicBlock, Loop> LI; 911 friend class LoopBase<BasicBlock, Loop>; 912 913 void operator=(const LoopInfo &); // do not implement 914 LoopInfo(const LoopInfo &); // do not implement 915public: 916 static char ID; // Pass identification, replacement for typeid 917 918 LoopInfo() : FunctionPass(&ID) {} 919 920 LoopInfoBase<BasicBlock, Loop>& getBase() { return LI; } 921 922 /// iterator/begin/end - The interface to the top-level loops in the current 923 /// function. 924 /// 925 typedef LoopInfoBase<BasicBlock, Loop>::iterator iterator; 926 inline iterator begin() const { return LI.begin(); } 927 inline iterator end() const { return LI.end(); } 928 bool empty() const { return LI.empty(); } 929 930 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 931 /// block is in no loop (for example the entry node), null is returned. 932 /// 933 inline Loop *getLoopFor(const BasicBlock *BB) const { 934 return LI.getLoopFor(BB); 935 } 936 937 /// operator[] - same as getLoopFor... 938 /// 939 inline const Loop *operator[](const BasicBlock *BB) const { 940 return LI.getLoopFor(BB); 941 } 942 943 /// getLoopDepth - Return the loop nesting level of the specified block. A 944 /// depth of 0 means the block is not inside any loop. 945 /// 946 inline unsigned getLoopDepth(const BasicBlock *BB) const { 947 return LI.getLoopDepth(BB); 948 } 949 950 // isLoopHeader - True if the block is a loop header node 951 inline bool isLoopHeader(BasicBlock *BB) const { 952 return LI.isLoopHeader(BB); 953 } 954 955 /// runOnFunction - Calculate the natural loop information. 956 /// 957 virtual bool runOnFunction(Function &F); 958 959 virtual void verifyAnalysis() const; 960 961 virtual void releaseMemory() { LI.releaseMemory(); } 962 963 virtual void print(raw_ostream &O, const Module* M = 0) const; 964 965 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 966 967 /// removeLoop - This removes the specified top-level loop from this loop info 968 /// object. The loop is not deleted, as it will presumably be inserted into 969 /// another loop. 970 inline Loop *removeLoop(iterator I) { return LI.removeLoop(I); } 971 972 /// changeLoopFor - Change the top-level loop that contains BB to the 973 /// specified loop. This should be used by transformations that restructure 974 /// the loop hierarchy tree. 975 inline void changeLoopFor(BasicBlock *BB, Loop *L) { 976 LI.changeLoopFor(BB, L); 977 } 978 979 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 980 /// list with the indicated loop. 981 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) { 982 LI.changeTopLevelLoop(OldLoop, NewLoop); 983 } 984 985 /// addTopLevelLoop - This adds the specified loop to the collection of 986 /// top-level loops. 987 inline void addTopLevelLoop(Loop *New) { 988 LI.addTopLevelLoop(New); 989 } 990 991 /// removeBlock - This method completely removes BB from all data structures, 992 /// including all of the Loop objects it is nested in and our mapping from 993 /// BasicBlocks to loops. 994 void removeBlock(BasicBlock *BB) { 995 LI.removeBlock(BB); 996 } 997}; 998 999 1000// Allow clients to walk the list of nested loops... 1001template <> struct GraphTraits<const Loop*> { 1002 typedef const Loop NodeType; 1003 typedef LoopInfo::iterator ChildIteratorType; 1004 1005 static NodeType *getEntryNode(const Loop *L) { return L; } 1006 static inline ChildIteratorType child_begin(NodeType *N) { 1007 return N->begin(); 1008 } 1009 static inline ChildIteratorType child_end(NodeType *N) { 1010 return N->end(); 1011 } 1012}; 1013 1014template <> struct GraphTraits<Loop*> { 1015 typedef Loop NodeType; 1016 typedef LoopInfo::iterator ChildIteratorType; 1017 1018 static NodeType *getEntryNode(Loop *L) { return L; } 1019 static inline ChildIteratorType child_begin(NodeType *N) { 1020 return N->begin(); 1021 } 1022 static inline ChildIteratorType child_end(NodeType *N) { 1023 return N->end(); 1024 } 1025}; 1026 1027template<class BlockT, class LoopT> 1028void 1029LoopBase<BlockT, LoopT>::addBasicBlockToLoop(BlockT *NewBB, 1030 LoopInfoBase<BlockT, LoopT> &LIB) { 1031 assert((Blocks.empty() || LIB[getHeader()] == this) && 1032 "Incorrect LI specified for this loop!"); 1033 assert(NewBB && "Cannot add a null basic block to the loop!"); 1034 assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!"); 1035 1036 LoopT *L = static_cast<LoopT *>(this); 1037 1038 // Add the loop mapping to the LoopInfo object... 1039 LIB.BBMap[NewBB] = L; 1040 1041 // Add the basic block to this loop and all parent loops... 1042 while (L) { 1043 L->Blocks.push_back(NewBB); 1044 L = L->getParentLoop(); 1045 } 1046} 1047 1048} // End llvm namespace 1049 1050#endif 1051