LoopInfo.h revision 5c89b5240c90eb8171f999e5f06f815502d0321c
1//===- llvm/Analysis/LoopInfo.h - Natural Loop Calculator -------*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file defines the LoopInfo class that is used to identify natural loops 11// and determine the loop depth of various nodes of the CFG. Note that natural 12// loops may actually be several loops that share the same header node. 13// 14// This analysis calculates the nesting structure of loops in a function. For 15// each natural loop identified, this analysis identifies natural loops 16// contained entirely within the loop and the basic blocks the make up the loop. 17// 18// It can calculate on the fly various bits of information, for example: 19// 20// * whether there is a preheader for the loop 21// * the number of back edges to the header 22// * whether or not a particular block branches out of the loop 23// * the successor blocks of the loop 24// * the loop depth 25// * the trip count 26// * etc... 27// 28//===----------------------------------------------------------------------===// 29 30#ifndef LLVM_ANALYSIS_LOOP_INFO_H 31#define LLVM_ANALYSIS_LOOP_INFO_H 32 33#include "llvm/Pass.h" 34#include "llvm/ADT/DepthFirstIterator.h" 35#include "llvm/ADT/GraphTraits.h" 36#include "llvm/ADT/SmallVector.h" 37#include "llvm/Analysis/Dominators.h" 38#include "llvm/Support/CFG.h" 39#include "llvm/Support/raw_ostream.h" 40#include <algorithm> 41 42namespace llvm { 43 44template<typename T> 45static void RemoveFromVector(std::vector<T*> &V, T *N) { 46 typename std::vector<T*>::iterator I = std::find(V.begin(), V.end(), N); 47 assert(I != V.end() && "N is not in this list!"); 48 V.erase(I); 49} 50 51class DominatorTree; 52class LoopInfo; 53class Loop; 54template<class N, class M> class LoopInfoBase; 55template<class N, class M> class LoopBase; 56 57//===----------------------------------------------------------------------===// 58/// LoopBase class - Instances of this class are used to represent loops that 59/// are detected in the flow graph 60/// 61template<class BlockT, class LoopT> 62class LoopBase { 63 LoopT *ParentLoop; 64 // SubLoops - Loops contained entirely within this one. 65 std::vector<LoopT *> SubLoops; 66 67 // Blocks - The list of blocks in this loop. First entry is the header node. 68 std::vector<BlockT*> Blocks; 69 70 // DO NOT IMPLEMENT 71 LoopBase(const LoopBase<BlockT, LoopT> &); 72 // DO NOT IMPLEMENT 73 const LoopBase<BlockT, LoopT>&operator=(const LoopBase<BlockT, LoopT> &); 74public: 75 /// Loop ctor - This creates an empty loop. 76 LoopBase() : ParentLoop(0) {} 77 ~LoopBase() { 78 for (size_t i = 0, e = SubLoops.size(); i != e; ++i) 79 delete SubLoops[i]; 80 } 81 82 /// getLoopDepth - Return the nesting level of this loop. An outer-most 83 /// loop has depth 1, for consistency with loop depth values used for basic 84 /// blocks, where depth 0 is used for blocks not inside any loops. 85 unsigned getLoopDepth() const { 86 unsigned D = 1; 87 for (const LoopT *CurLoop = ParentLoop; CurLoop; 88 CurLoop = CurLoop->ParentLoop) 89 ++D; 90 return D; 91 } 92 BlockT *getHeader() const { return Blocks.front(); } 93 LoopT *getParentLoop() const { return ParentLoop; } 94 95 /// contains - Return true if the specified basic block is in this loop 96 /// 97 bool contains(const BlockT *BB) const { 98 return std::find(block_begin(), block_end(), BB) != block_end(); 99 } 100 101 /// iterator/begin/end - Return the loops contained entirely within this loop. 102 /// 103 const std::vector<LoopT *> &getSubLoops() const { return SubLoops; } 104 typedef typename std::vector<LoopT *>::const_iterator iterator; 105 iterator begin() const { return SubLoops.begin(); } 106 iterator end() const { return SubLoops.end(); } 107 bool empty() const { return SubLoops.empty(); } 108 109 /// getBlocks - Get a list of the basic blocks which make up this loop. 110 /// 111 const std::vector<BlockT*> &getBlocks() const { return Blocks; } 112 typedef typename std::vector<BlockT*>::const_iterator block_iterator; 113 block_iterator block_begin() const { return Blocks.begin(); } 114 block_iterator block_end() const { return Blocks.end(); } 115 116 /// isLoopExit - True if terminator in the block can branch to another block 117 /// that is outside of the current loop. 118 /// 119 bool isLoopExit(const BlockT *BB) const { 120 typedef GraphTraits<BlockT*> BlockTraits; 121 for (typename BlockTraits::ChildIteratorType SI = 122 BlockTraits::child_begin(const_cast<BlockT*>(BB)), 123 SE = BlockTraits::child_end(const_cast<BlockT*>(BB)); SI != SE; ++SI) { 124 if (!contains(*SI)) 125 return true; 126 } 127 return false; 128 } 129 130 /// getNumBackEdges - Calculate the number of back edges to the loop header 131 /// 132 unsigned getNumBackEdges() const { 133 unsigned NumBackEdges = 0; 134 BlockT *H = getHeader(); 135 136 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 137 for (typename InvBlockTraits::ChildIteratorType I = 138 InvBlockTraits::child_begin(const_cast<BlockT*>(H)), 139 E = InvBlockTraits::child_end(const_cast<BlockT*>(H)); I != E; ++I) 140 if (contains(*I)) 141 ++NumBackEdges; 142 143 return NumBackEdges; 144 } 145 146 //===--------------------------------------------------------------------===// 147 // APIs for simple analysis of the loop. 148 // 149 // Note that all of these methods can fail on general loops (ie, there may not 150 // be a preheader, etc). For best success, the loop simplification and 151 // induction variable canonicalization pass should be used to normalize loops 152 // for easy analysis. These methods assume canonical loops. 153 154 /// getExitingBlocks - Return all blocks inside the loop that have successors 155 /// outside of the loop. These are the blocks _inside of the current loop_ 156 /// which branch out. The returned list is always unique. 157 /// 158 void getExitingBlocks(SmallVectorImpl<BlockT *> &ExitingBlocks) const { 159 // Sort the blocks vector so that we can use binary search to do quick 160 // lookups. 161 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 162 std::sort(LoopBBs.begin(), LoopBBs.end()); 163 164 typedef GraphTraits<BlockT*> BlockTraits; 165 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) 166 for (typename BlockTraits::ChildIteratorType I = 167 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 168 I != E; ++I) 169 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) { 170 // Not in current loop? It must be an exit block. 171 ExitingBlocks.push_back(*BI); 172 break; 173 } 174 } 175 176 /// getExitingBlock - If getExitingBlocks would return exactly one block, 177 /// return that block. Otherwise return null. 178 BlockT *getExitingBlock() const { 179 SmallVector<BlockT*, 8> ExitingBlocks; 180 getExitingBlocks(ExitingBlocks); 181 if (ExitingBlocks.size() == 1) 182 return ExitingBlocks[0]; 183 return 0; 184 } 185 186 /// getExitBlocks - Return all of the successor blocks of this loop. These 187 /// are the blocks _outside of the current loop_ which are branched to. 188 /// 189 void getExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const { 190 // Sort the blocks vector so that we can use binary search to do quick 191 // lookups. 192 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 193 std::sort(LoopBBs.begin(), LoopBBs.end()); 194 195 typedef GraphTraits<BlockT*> BlockTraits; 196 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) 197 for (typename BlockTraits::ChildIteratorType I = 198 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 199 I != E; ++I) 200 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) 201 // Not in current loop? It must be an exit block. 202 ExitBlocks.push_back(*I); 203 } 204 205 /// getExitBlock - If getExitBlocks would return exactly one block, 206 /// return that block. Otherwise return null. 207 BlockT *getExitBlock() const { 208 SmallVector<BlockT*, 8> ExitBlocks; 209 getExitBlocks(ExitBlocks); 210 if (ExitBlocks.size() == 1) 211 return ExitBlocks[0]; 212 return 0; 213 } 214 215 /// getExitEdges - Return all pairs of (_inside_block_,_outside_block_). 216 typedef std::pair<const BlockT*,const BlockT*> Edge; 217 void getExitEdges(SmallVectorImpl<Edge> &ExitEdges) const { 218 // Sort the blocks vector so that we can use binary search to do quick 219 // lookups. 220 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 221 std::sort(LoopBBs.begin(), LoopBBs.end()); 222 223 typedef GraphTraits<BlockT*> BlockTraits; 224 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) 225 for (typename BlockTraits::ChildIteratorType I = 226 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 227 I != E; ++I) 228 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) 229 // Not in current loop? It must be an exit block. 230 ExitEdges.push_back(std::make_pair(*BI, *I)); 231 } 232 233 /// getLoopPreheader - If there is a preheader for this loop, return it. A 234 /// loop has a preheader if there is only one edge to the header of the loop 235 /// from outside of the loop. If this is the case, the block branching to the 236 /// header of the loop is the preheader node. 237 /// 238 /// This method returns null if there is no preheader for the loop. 239 /// 240 BlockT *getLoopPreheader() const { 241 // Keep track of nodes outside the loop branching to the header... 242 BlockT *Out = 0; 243 244 // Loop over the predecessors of the header node... 245 BlockT *Header = getHeader(); 246 typedef GraphTraits<BlockT*> BlockTraits; 247 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 248 for (typename InvBlockTraits::ChildIteratorType PI = 249 InvBlockTraits::child_begin(Header), 250 PE = InvBlockTraits::child_end(Header); PI != PE; ++PI) 251 if (!contains(*PI)) { // If the block is not in the loop... 252 if (Out && Out != *PI) 253 return 0; // Multiple predecessors outside the loop 254 Out = *PI; 255 } 256 257 // Make sure there is only one exit out of the preheader. 258 assert(Out && "Header of loop has no predecessors from outside loop?"); 259 typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out); 260 ++SI; 261 if (SI != BlockTraits::child_end(Out)) 262 return 0; // Multiple exits from the block, must not be a preheader. 263 264 // If there is exactly one preheader, return it. If there was zero, then 265 // Out is still null. 266 return Out; 267 } 268 269 /// getLoopLatch - If there is a single latch block for this loop, return it. 270 /// A latch block is a block that contains a branch back to the header. 271 /// A loop header in normal form has two edges into it: one from a preheader 272 /// and one from a latch block. 273 BlockT *getLoopLatch() const { 274 BlockT *Header = getHeader(); 275 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 276 typename InvBlockTraits::ChildIteratorType PI = 277 InvBlockTraits::child_begin(Header); 278 typename InvBlockTraits::ChildIteratorType PE = 279 InvBlockTraits::child_end(Header); 280 if (PI == PE) return 0; // no preds? 281 282 BlockT *Latch = 0; 283 if (contains(*PI)) 284 Latch = *PI; 285 ++PI; 286 if (PI == PE) return 0; // only one pred? 287 288 if (contains(*PI)) { 289 if (Latch) return 0; // multiple backedges 290 Latch = *PI; 291 } 292 ++PI; 293 if (PI != PE) return 0; // more than two preds 294 295 return Latch; 296 } 297 298 //===--------------------------------------------------------------------===// 299 // APIs for updating loop information after changing the CFG 300 // 301 302 /// addBasicBlockToLoop - This method is used by other analyses to update loop 303 /// information. NewBB is set to be a new member of the current loop. 304 /// Because of this, it is added as a member of all parent loops, and is added 305 /// to the specified LoopInfo object as being in the current basic block. It 306 /// is not valid to replace the loop header with this method. 307 /// 308 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LI); 309 310 /// replaceChildLoopWith - This is used when splitting loops up. It replaces 311 /// the OldChild entry in our children list with NewChild, and updates the 312 /// parent pointer of OldChild to be null and the NewChild to be this loop. 313 /// This updates the loop depth of the new child. 314 void replaceChildLoopWith(LoopT *OldChild, 315 LoopT *NewChild) { 316 assert(OldChild->ParentLoop == this && "This loop is already broken!"); 317 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 318 typename std::vector<LoopT *>::iterator I = 319 std::find(SubLoops.begin(), SubLoops.end(), OldChild); 320 assert(I != SubLoops.end() && "OldChild not in loop!"); 321 *I = NewChild; 322 OldChild->ParentLoop = 0; 323 NewChild->ParentLoop = static_cast<LoopT *>(this); 324 } 325 326 /// addChildLoop - Add the specified loop to be a child of this loop. This 327 /// updates the loop depth of the new child. 328 /// 329 void addChildLoop(LoopT *NewChild) { 330 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 331 NewChild->ParentLoop = static_cast<LoopT *>(this); 332 SubLoops.push_back(NewChild); 333 } 334 335 /// removeChildLoop - This removes the specified child from being a subloop of 336 /// this loop. The loop is not deleted, as it will presumably be inserted 337 /// into another loop. 338 LoopT *removeChildLoop(iterator I) { 339 assert(I != SubLoops.end() && "Cannot remove end iterator!"); 340 LoopT *Child = *I; 341 assert(Child->ParentLoop == this && "Child is not a child of this loop!"); 342 SubLoops.erase(SubLoops.begin()+(I-begin())); 343 Child->ParentLoop = 0; 344 return Child; 345 } 346 347 /// addBlockEntry - This adds a basic block directly to the basic block list. 348 /// This should only be used by transformations that create new loops. Other 349 /// transformations should use addBasicBlockToLoop. 350 void addBlockEntry(BlockT *BB) { 351 Blocks.push_back(BB); 352 } 353 354 /// moveToHeader - This method is used to move BB (which must be part of this 355 /// loop) to be the loop header of the loop (the block that dominates all 356 /// others). 357 void moveToHeader(BlockT *BB) { 358 if (Blocks[0] == BB) return; 359 for (unsigned i = 0; ; ++i) { 360 assert(i != Blocks.size() && "Loop does not contain BB!"); 361 if (Blocks[i] == BB) { 362 Blocks[i] = Blocks[0]; 363 Blocks[0] = BB; 364 return; 365 } 366 } 367 } 368 369 /// removeBlockFromLoop - This removes the specified basic block from the 370 /// current loop, updating the Blocks as appropriate. This does not update 371 /// the mapping in the LoopInfo class. 372 void removeBlockFromLoop(BlockT *BB) { 373 RemoveFromVector(Blocks, BB); 374 } 375 376 /// verifyLoop - Verify loop structure 377 void verifyLoop() const { 378#ifndef NDEBUG 379 assert(!Blocks.empty() && "Loop header is missing"); 380 assert(getHeader() && "Loop header is missing"); 381 382 // Sort the blocks vector so that we can use binary search to do quick 383 // lookups. 384 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 385 std::sort(LoopBBs.begin(), LoopBBs.end()); 386 387 // Check the individual blocks. 388 for (block_iterator I = block_begin(), E = block_end(); I != E; ++I) { 389 BlockT *BB = *I; 390 bool HasInsideLoopSuccs = false; 391 bool HasInsideLoopPreds = false; 392 SmallVector<BlockT *, 2> OutsideLoopPreds; 393 394 typedef GraphTraits<BlockT*> BlockTraits; 395 for (typename BlockTraits::ChildIteratorType SI = 396 BlockTraits::child_begin(BB), SE = BlockTraits::child_end(BB); 397 SI != SE; ++SI) 398 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *SI)) { 399 HasInsideLoopSuccs = true; 400 break; 401 } 402 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 403 for (typename InvBlockTraits::ChildIteratorType PI = 404 InvBlockTraits::child_begin(BB), PE = InvBlockTraits::child_end(BB); 405 PI != PE; ++PI) { 406 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *PI)) 407 HasInsideLoopPreds = true; 408 else 409 OutsideLoopPreds.push_back(*PI); 410 } 411 412 if (BB == getHeader()) { 413 assert(!OutsideLoopPreds.empty() && "Loop is unreachable!"); 414 } else if (!OutsideLoopPreds.empty()) { 415 // A non-header loop shouldn't be reachable from outside the loop, 416 // though it is permitted if the predecessor is not itself actually 417 // reachable. 418 BlockT *EntryBB = BB->getParent()->begin(); 419 for (df_iterator<BlockT *> NI = df_begin(EntryBB), 420 NE = df_end(EntryBB); NI != NE; ++NI) 421 for (unsigned i = 0, e = OutsideLoopPreds.size(); i != e; ++i) 422 assert(*NI != OutsideLoopPreds[i] && 423 "Loop has multiple entry points!"); 424 } 425 assert(HasInsideLoopPreds && "Loop block has no in-loop predecessors!"); 426 assert(HasInsideLoopSuccs && "Loop block has no in-loop successors!"); 427 assert(BB != getHeader()->getParent()->begin() && 428 "Loop contains function entry block!"); 429 } 430 431 // Check the subloops. 432 for (iterator I = begin(), E = end(); I != E; ++I) 433 // Each block in each subloop should be contained within this loop. 434 for (block_iterator BI = (*I)->block_begin(), BE = (*I)->block_end(); 435 BI != BE; ++BI) { 436 assert(std::binary_search(LoopBBs.begin(), LoopBBs.end(), *BI) && 437 "Loop does not contain all the blocks of a subloop!"); 438 } 439 440 // Check the parent loop pointer. 441 if (ParentLoop) { 442 assert(std::find(ParentLoop->begin(), ParentLoop->end(), this) != 443 ParentLoop->end() && 444 "Loop is not a subloop of its parent!"); 445 } 446#endif 447 } 448 449 /// verifyLoop - Verify loop structure of this loop and all nested loops. 450 void verifyLoopNest() const { 451 // Verify this loop. 452 verifyLoop(); 453 // Verify the subloops. 454 for (iterator I = begin(), E = end(); I != E; ++I) 455 (*I)->verifyLoopNest(); 456 } 457 458 void print(raw_ostream &OS, unsigned Depth = 0) const { 459 OS.indent(Depth*2) << "Loop at depth " << getLoopDepth() 460 << " containing: "; 461 462 for (unsigned i = 0; i < getBlocks().size(); ++i) { 463 if (i) OS << ","; 464 BlockT *BB = getBlocks()[i]; 465 WriteAsOperand(OS, BB, false); 466 if (BB == getHeader()) OS << "<header>"; 467 if (BB == getLoopLatch()) OS << "<latch>"; 468 if (isLoopExit(BB)) OS << "<exit>"; 469 } 470 OS << "\n"; 471 472 for (iterator I = begin(), E = end(); I != E; ++I) 473 (*I)->print(OS, Depth+2); 474 } 475 476 void dump() const { 477 print(errs()); 478 } 479 480protected: 481 friend class LoopInfoBase<BlockT, LoopT>; 482 explicit LoopBase(BlockT *BB) : ParentLoop(0) { 483 Blocks.push_back(BB); 484 } 485}; 486 487class Loop : public LoopBase<BasicBlock, Loop> { 488public: 489 Loop() {} 490 491 /// isLoopInvariant - Return true if the specified value is loop invariant 492 /// 493 bool isLoopInvariant(Value *V) const; 494 495 /// isLoopInvariant - Return true if the specified instruction is 496 /// loop-invariant. 497 /// 498 bool isLoopInvariant(Instruction *I) const; 499 500 /// makeLoopInvariant - If the given value is an instruction inside of the 501 /// loop and it can be hoisted, do so to make it trivially loop-invariant. 502 /// Return true if the value after any hoisting is loop invariant. This 503 /// function can be used as a slightly more aggressive replacement for 504 /// isLoopInvariant. 505 /// 506 /// If InsertPt is specified, it is the point to hoist instructions to. 507 /// If null, the terminator of the loop preheader is used. 508 /// 509 bool makeLoopInvariant(Value *V, bool &Changed, 510 Instruction *InsertPt = 0) const; 511 512 /// makeLoopInvariant - If the given instruction is inside of the 513 /// loop and it can be hoisted, do so to make it trivially loop-invariant. 514 /// Return true if the instruction after any hoisting is loop invariant. This 515 /// function can be used as a slightly more aggressive replacement for 516 /// isLoopInvariant. 517 /// 518 /// If InsertPt is specified, it is the point to hoist instructions to. 519 /// If null, the terminator of the loop preheader is used. 520 /// 521 bool makeLoopInvariant(Instruction *I, bool &Changed, 522 Instruction *InsertPt = 0) const; 523 524 /// getCanonicalInductionVariable - Check to see if the loop has a canonical 525 /// induction variable: an integer recurrence that starts at 0 and increments 526 /// by one each time through the loop. If so, return the phi node that 527 /// corresponds to it. 528 /// 529 /// The IndVarSimplify pass transforms loops to have a canonical induction 530 /// variable. 531 /// 532 PHINode *getCanonicalInductionVariable() const; 533 534 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds 535 /// the canonical induction variable value for the "next" iteration of the 536 /// loop. This always succeeds if getCanonicalInductionVariable succeeds. 537 /// 538 Instruction *getCanonicalInductionVariableIncrement() const; 539 540 /// getTripCount - Return a loop-invariant LLVM value indicating the number of 541 /// times the loop will be executed. Note that this means that the backedge 542 /// of the loop executes N-1 times. If the trip-count cannot be determined, 543 /// this returns null. 544 /// 545 /// The IndVarSimplify pass transforms loops to have a form that this 546 /// function easily understands. 547 /// 548 Value *getTripCount() const; 549 550 /// getSmallConstantTripCount - Returns the trip count of this loop as a 551 /// normal unsigned value, if possible. Returns 0 if the trip count is unknown 552 /// of not constant. Will also return 0 if the trip count is very large 553 /// (>= 2^32) 554 unsigned getSmallConstantTripCount() const; 555 556 /// getSmallConstantTripMultiple - Returns the largest constant divisor of the 557 /// trip count of this loop as a normal unsigned value, if possible. This 558 /// means that the actual trip count is always a multiple of the returned 559 /// value (don't forget the trip count could very well be zero as well!). 560 /// 561 /// Returns 1 if the trip count is unknown or not guaranteed to be the 562 /// multiple of a constant (which is also the case if the trip count is simply 563 /// constant, use getSmallConstantTripCount for that case), Will also return 1 564 /// if the trip count is very large (>= 2^32). 565 unsigned getSmallConstantTripMultiple() const; 566 567 /// isLCSSAForm - Return true if the Loop is in LCSSA form 568 bool isLCSSAForm() const; 569 570 /// isLoopSimplifyForm - Return true if the Loop is in the form that 571 /// the LoopSimplify form transforms loops to, which is sometimes called 572 /// normal form. 573 bool isLoopSimplifyForm() const; 574 575 /// getUniqueExitBlocks - Return all unique successor blocks of this loop. 576 /// These are the blocks _outside of the current loop_ which are branched to. 577 /// This assumes that loop is in canonical form. 578 /// 579 void getUniqueExitBlocks(SmallVectorImpl<BasicBlock *> &ExitBlocks) const; 580 581 /// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one 582 /// block, return that block. Otherwise return null. 583 BasicBlock *getUniqueExitBlock() const; 584 585private: 586 friend class LoopInfoBase<BasicBlock, Loop>; 587 explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {} 588}; 589 590//===----------------------------------------------------------------------===// 591/// LoopInfo - This class builds and contains all of the top level loop 592/// structures in the specified function. 593/// 594 595template<class BlockT, class LoopT> 596class LoopInfoBase { 597 // BBMap - Mapping of basic blocks to the inner most loop they occur in 598 std::map<BlockT *, LoopT *> BBMap; 599 std::vector<LoopT *> TopLevelLoops; 600 friend class LoopBase<BlockT, LoopT>; 601 602 void operator=(const LoopInfoBase &); // do not implement 603 LoopInfoBase(const LoopInfo &); // do not implement 604public: 605 LoopInfoBase() { } 606 ~LoopInfoBase() { releaseMemory(); } 607 608 void releaseMemory() { 609 for (typename std::vector<LoopT *>::iterator I = 610 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I) 611 delete *I; // Delete all of the loops... 612 613 BBMap.clear(); // Reset internal state of analysis 614 TopLevelLoops.clear(); 615 } 616 617 /// iterator/begin/end - The interface to the top-level loops in the current 618 /// function. 619 /// 620 typedef typename std::vector<LoopT *>::const_iterator iterator; 621 iterator begin() const { return TopLevelLoops.begin(); } 622 iterator end() const { return TopLevelLoops.end(); } 623 bool empty() const { return TopLevelLoops.empty(); } 624 625 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 626 /// block is in no loop (for example the entry node), null is returned. 627 /// 628 LoopT *getLoopFor(const BlockT *BB) const { 629 typename std::map<BlockT *, LoopT *>::const_iterator I= 630 BBMap.find(const_cast<BlockT*>(BB)); 631 return I != BBMap.end() ? I->second : 0; 632 } 633 634 /// operator[] - same as getLoopFor... 635 /// 636 const LoopT *operator[](const BlockT *BB) const { 637 return getLoopFor(BB); 638 } 639 640 /// getLoopDepth - Return the loop nesting level of the specified block. A 641 /// depth of 0 means the block is not inside any loop. 642 /// 643 unsigned getLoopDepth(const BlockT *BB) const { 644 const LoopT *L = getLoopFor(BB); 645 return L ? L->getLoopDepth() : 0; 646 } 647 648 // isLoopHeader - True if the block is a loop header node 649 bool isLoopHeader(BlockT *BB) const { 650 const LoopT *L = getLoopFor(BB); 651 return L && L->getHeader() == BB; 652 } 653 654 /// removeLoop - This removes the specified top-level loop from this loop info 655 /// object. The loop is not deleted, as it will presumably be inserted into 656 /// another loop. 657 LoopT *removeLoop(iterator I) { 658 assert(I != end() && "Cannot remove end iterator!"); 659 LoopT *L = *I; 660 assert(L->getParentLoop() == 0 && "Not a top-level loop!"); 661 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin())); 662 return L; 663 } 664 665 /// changeLoopFor - Change the top-level loop that contains BB to the 666 /// specified loop. This should be used by transformations that restructure 667 /// the loop hierarchy tree. 668 void changeLoopFor(BlockT *BB, LoopT *L) { 669 LoopT *&OldLoop = BBMap[BB]; 670 assert(OldLoop && "Block not in a loop yet!"); 671 OldLoop = L; 672 } 673 674 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 675 /// list with the indicated loop. 676 void changeTopLevelLoop(LoopT *OldLoop, 677 LoopT *NewLoop) { 678 typename std::vector<LoopT *>::iterator I = 679 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop); 680 assert(I != TopLevelLoops.end() && "Old loop not at top level!"); 681 *I = NewLoop; 682 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 && 683 "Loops already embedded into a subloop!"); 684 } 685 686 /// addTopLevelLoop - This adds the specified loop to the collection of 687 /// top-level loops. 688 void addTopLevelLoop(LoopT *New) { 689 assert(New->getParentLoop() == 0 && "Loop already in subloop!"); 690 TopLevelLoops.push_back(New); 691 } 692 693 /// removeBlock - This method completely removes BB from all data structures, 694 /// including all of the Loop objects it is nested in and our mapping from 695 /// BasicBlocks to loops. 696 void removeBlock(BlockT *BB) { 697 typename std::map<BlockT *, LoopT *>::iterator I = BBMap.find(BB); 698 if (I != BBMap.end()) { 699 for (LoopT *L = I->second; L; L = L->getParentLoop()) 700 L->removeBlockFromLoop(BB); 701 702 BBMap.erase(I); 703 } 704 } 705 706 // Internals 707 708 static bool isNotAlreadyContainedIn(const LoopT *SubLoop, 709 const LoopT *ParentLoop) { 710 if (SubLoop == 0) return true; 711 if (SubLoop == ParentLoop) return false; 712 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop); 713 } 714 715 void Calculate(DominatorTreeBase<BlockT> &DT) { 716 BlockT *RootNode = DT.getRootNode()->getBlock(); 717 718 for (df_iterator<BlockT*> NI = df_begin(RootNode), 719 NE = df_end(RootNode); NI != NE; ++NI) 720 if (LoopT *L = ConsiderForLoop(*NI, DT)) 721 TopLevelLoops.push_back(L); 722 } 723 724 LoopT *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) { 725 if (BBMap.find(BB) != BBMap.end()) return 0;// Haven't processed this node? 726 727 std::vector<BlockT *> TodoStack; 728 729 // Scan the predecessors of BB, checking to see if BB dominates any of 730 // them. This identifies backedges which target this node... 731 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 732 for (typename InvBlockTraits::ChildIteratorType I = 733 InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB); 734 I != E; ++I) 735 if (DT.dominates(BB, *I)) // If BB dominates it's predecessor... 736 TodoStack.push_back(*I); 737 738 if (TodoStack.empty()) return 0; // No backedges to this block... 739 740 // Create a new loop to represent this basic block... 741 LoopT *L = new LoopT(BB); 742 BBMap[BB] = L; 743 744 BlockT *EntryBlock = BB->getParent()->begin(); 745 746 while (!TodoStack.empty()) { // Process all the nodes in the loop 747 BlockT *X = TodoStack.back(); 748 TodoStack.pop_back(); 749 750 if (!L->contains(X) && // As of yet unprocessed?? 751 DT.dominates(EntryBlock, X)) { // X is reachable from entry block? 752 // Check to see if this block already belongs to a loop. If this occurs 753 // then we have a case where a loop that is supposed to be a child of 754 // the current loop was processed before the current loop. When this 755 // occurs, this child loop gets added to a part of the current loop, 756 // making it a sibling to the current loop. We have to reparent this 757 // loop. 758 if (LoopT *SubLoop = 759 const_cast<LoopT *>(getLoopFor(X))) 760 if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){ 761 // Remove the subloop from it's current parent... 762 assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L); 763 LoopT *SLP = SubLoop->ParentLoop; // SubLoopParent 764 typename std::vector<LoopT *>::iterator I = 765 std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop); 766 assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?"); 767 SLP->SubLoops.erase(I); // Remove from parent... 768 769 // Add the subloop to THIS loop... 770 SubLoop->ParentLoop = L; 771 L->SubLoops.push_back(SubLoop); 772 } 773 774 // Normal case, add the block to our loop... 775 L->Blocks.push_back(X); 776 777 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 778 779 // Add all of the predecessors of X to the end of the work stack... 780 TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X), 781 InvBlockTraits::child_end(X)); 782 } 783 } 784 785 // If there are any loops nested within this loop, create them now! 786 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 787 E = L->Blocks.end(); I != E; ++I) 788 if (LoopT *NewLoop = ConsiderForLoop(*I, DT)) { 789 L->SubLoops.push_back(NewLoop); 790 NewLoop->ParentLoop = L; 791 } 792 793 // Add the basic blocks that comprise this loop to the BBMap so that this 794 // loop can be found for them. 795 // 796 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 797 E = L->Blocks.end(); I != E; ++I) 798 BBMap.insert(std::make_pair(*I, L)); 799 800 // Now that we have a list of all of the child loops of this loop, check to 801 // see if any of them should actually be nested inside of each other. We 802 // can accidentally pull loops our of their parents, so we must make sure to 803 // organize the loop nests correctly now. 804 { 805 std::map<BlockT *, LoopT *> ContainingLoops; 806 for (unsigned i = 0; i != L->SubLoops.size(); ++i) { 807 LoopT *Child = L->SubLoops[i]; 808 assert(Child->getParentLoop() == L && "Not proper child loop?"); 809 810 if (LoopT *ContainingLoop = ContainingLoops[Child->getHeader()]) { 811 // If there is already a loop which contains this loop, move this loop 812 // into the containing loop. 813 MoveSiblingLoopInto(Child, ContainingLoop); 814 --i; // The loop got removed from the SubLoops list. 815 } else { 816 // This is currently considered to be a top-level loop. Check to see 817 // if any of the contained blocks are loop headers for subloops we 818 // have already processed. 819 for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) { 820 LoopT *&BlockLoop = ContainingLoops[Child->Blocks[b]]; 821 if (BlockLoop == 0) { // Child block not processed yet... 822 BlockLoop = Child; 823 } else if (BlockLoop != Child) { 824 LoopT *SubLoop = BlockLoop; 825 // Reparent all of the blocks which used to belong to BlockLoops 826 for (unsigned j = 0, e = SubLoop->Blocks.size(); j != e; ++j) 827 ContainingLoops[SubLoop->Blocks[j]] = Child; 828 829 // There is already a loop which contains this block, that means 830 // that we should reparent the loop which the block is currently 831 // considered to belong to to be a child of this loop. 832 MoveSiblingLoopInto(SubLoop, Child); 833 --i; // We just shrunk the SubLoops list. 834 } 835 } 836 } 837 } 838 } 839 840 return L; 841 } 842 843 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside 844 /// of the NewParent Loop, instead of being a sibling of it. 845 void MoveSiblingLoopInto(LoopT *NewChild, 846 LoopT *NewParent) { 847 LoopT *OldParent = NewChild->getParentLoop(); 848 assert(OldParent && OldParent == NewParent->getParentLoop() && 849 NewChild != NewParent && "Not sibling loops!"); 850 851 // Remove NewChild from being a child of OldParent 852 typename std::vector<LoopT *>::iterator I = 853 std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(), 854 NewChild); 855 assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??"); 856 OldParent->SubLoops.erase(I); // Remove from parent's subloops list 857 NewChild->ParentLoop = 0; 858 859 InsertLoopInto(NewChild, NewParent); 860 } 861 862 /// InsertLoopInto - This inserts loop L into the specified parent loop. If 863 /// the parent loop contains a loop which should contain L, the loop gets 864 /// inserted into L instead. 865 void InsertLoopInto(LoopT *L, LoopT *Parent) { 866 BlockT *LHeader = L->getHeader(); 867 assert(Parent->contains(LHeader) && 868 "This loop should not be inserted here!"); 869 870 // Check to see if it belongs in a child loop... 871 for (unsigned i = 0, e = static_cast<unsigned>(Parent->SubLoops.size()); 872 i != e; ++i) 873 if (Parent->SubLoops[i]->contains(LHeader)) { 874 InsertLoopInto(L, Parent->SubLoops[i]); 875 return; 876 } 877 878 // If not, insert it here! 879 Parent->SubLoops.push_back(L); 880 L->ParentLoop = Parent; 881 } 882 883 // Debugging 884 885 void print(raw_ostream &OS) const { 886 for (unsigned i = 0; i < TopLevelLoops.size(); ++i) 887 TopLevelLoops[i]->print(OS); 888 #if 0 889 for (std::map<BasicBlock*, LoopT*>::const_iterator I = BBMap.begin(), 890 E = BBMap.end(); I != E; ++I) 891 OS << "BB '" << I->first->getName() << "' level = " 892 << I->second->getLoopDepth() << "\n"; 893 #endif 894 } 895}; 896 897class LoopInfo : public FunctionPass { 898 LoopInfoBase<BasicBlock, Loop> LI; 899 friend class LoopBase<BasicBlock, Loop>; 900 901 void operator=(const LoopInfo &); // do not implement 902 LoopInfo(const LoopInfo &); // do not implement 903public: 904 static char ID; // Pass identification, replacement for typeid 905 906 LoopInfo() : FunctionPass(&ID) {} 907 908 LoopInfoBase<BasicBlock, Loop>& getBase() { return LI; } 909 910 /// iterator/begin/end - The interface to the top-level loops in the current 911 /// function. 912 /// 913 typedef LoopInfoBase<BasicBlock, Loop>::iterator iterator; 914 inline iterator begin() const { return LI.begin(); } 915 inline iterator end() const { return LI.end(); } 916 bool empty() const { return LI.empty(); } 917 918 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 919 /// block is in no loop (for example the entry node), null is returned. 920 /// 921 inline Loop *getLoopFor(const BasicBlock *BB) const { 922 return LI.getLoopFor(BB); 923 } 924 925 /// operator[] - same as getLoopFor... 926 /// 927 inline const Loop *operator[](const BasicBlock *BB) const { 928 return LI.getLoopFor(BB); 929 } 930 931 /// getLoopDepth - Return the loop nesting level of the specified block. A 932 /// depth of 0 means the block is not inside any loop. 933 /// 934 inline unsigned getLoopDepth(const BasicBlock *BB) const { 935 return LI.getLoopDepth(BB); 936 } 937 938 // isLoopHeader - True if the block is a loop header node 939 inline bool isLoopHeader(BasicBlock *BB) const { 940 return LI.isLoopHeader(BB); 941 } 942 943 /// runOnFunction - Calculate the natural loop information. 944 /// 945 virtual bool runOnFunction(Function &F); 946 947 virtual void verifyAnalysis() const; 948 949 virtual void releaseMemory() { LI.releaseMemory(); } 950 951 virtual void print(raw_ostream &O, const Module* M = 0) const; 952 953 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 954 955 /// removeLoop - This removes the specified top-level loop from this loop info 956 /// object. The loop is not deleted, as it will presumably be inserted into 957 /// another loop. 958 inline Loop *removeLoop(iterator I) { return LI.removeLoop(I); } 959 960 /// changeLoopFor - Change the top-level loop that contains BB to the 961 /// specified loop. This should be used by transformations that restructure 962 /// the loop hierarchy tree. 963 inline void changeLoopFor(BasicBlock *BB, Loop *L) { 964 LI.changeLoopFor(BB, L); 965 } 966 967 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 968 /// list with the indicated loop. 969 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) { 970 LI.changeTopLevelLoop(OldLoop, NewLoop); 971 } 972 973 /// addTopLevelLoop - This adds the specified loop to the collection of 974 /// top-level loops. 975 inline void addTopLevelLoop(Loop *New) { 976 LI.addTopLevelLoop(New); 977 } 978 979 /// removeBlock - This method completely removes BB from all data structures, 980 /// including all of the Loop objects it is nested in and our mapping from 981 /// BasicBlocks to loops. 982 void removeBlock(BasicBlock *BB) { 983 LI.removeBlock(BB); 984 } 985 986 static bool isNotAlreadyContainedIn(const Loop *SubLoop, 987 const Loop *ParentLoop) { 988 return 989 LoopInfoBase<BasicBlock, Loop>::isNotAlreadyContainedIn(SubLoop, 990 ParentLoop); 991 } 992}; 993 994 995// Allow clients to walk the list of nested loops... 996template <> struct GraphTraits<const Loop*> { 997 typedef const Loop NodeType; 998 typedef LoopInfo::iterator ChildIteratorType; 999 1000 static NodeType *getEntryNode(const Loop *L) { return L; } 1001 static inline ChildIteratorType child_begin(NodeType *N) { 1002 return N->begin(); 1003 } 1004 static inline ChildIteratorType child_end(NodeType *N) { 1005 return N->end(); 1006 } 1007}; 1008 1009template <> struct GraphTraits<Loop*> { 1010 typedef Loop NodeType; 1011 typedef LoopInfo::iterator ChildIteratorType; 1012 1013 static NodeType *getEntryNode(Loop *L) { return L; } 1014 static inline ChildIteratorType child_begin(NodeType *N) { 1015 return N->begin(); 1016 } 1017 static inline ChildIteratorType child_end(NodeType *N) { 1018 return N->end(); 1019 } 1020}; 1021 1022template<class BlockT, class LoopT> 1023void 1024LoopBase<BlockT, LoopT>::addBasicBlockToLoop(BlockT *NewBB, 1025 LoopInfoBase<BlockT, LoopT> &LIB) { 1026 assert((Blocks.empty() || LIB[getHeader()] == this) && 1027 "Incorrect LI specified for this loop!"); 1028 assert(NewBB && "Cannot add a null basic block to the loop!"); 1029 assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!"); 1030 1031 LoopT *L = static_cast<LoopT *>(this); 1032 1033 // Add the loop mapping to the LoopInfo object... 1034 LIB.BBMap[NewBB] = L; 1035 1036 // Add the basic block to this loop and all parent loops... 1037 while (L) { 1038 L->Blocks.push_back(NewBB); 1039 L = L->getParentLoop(); 1040 } 1041} 1042 1043} // End llvm namespace 1044 1045#endif 1046