LoopInfo.h revision f17e9511f15a0e007ff47d0789d1a52502e8c1fb
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 basic block is in this loop 97 /// 98 bool contains(const BlockT *BB) const { 99 return std::find(block_begin(), block_end(), BB) != block_end(); 100 } 101 102 /// iterator/begin/end - Return the loops contained entirely within this loop. 103 /// 104 const std::vector<LoopT *> &getSubLoops() const { return SubLoops; } 105 typedef typename std::vector<LoopT *>::const_iterator iterator; 106 iterator begin() const { return SubLoops.begin(); } 107 iterator end() const { return SubLoops.end(); } 108 bool empty() const { return SubLoops.empty(); } 109 110 /// getBlocks - Get a list of the basic blocks which make up this loop. 111 /// 112 const std::vector<BlockT*> &getBlocks() const { return Blocks; } 113 typedef typename std::vector<BlockT*>::const_iterator block_iterator; 114 block_iterator block_begin() const { return Blocks.begin(); } 115 block_iterator block_end() const { return Blocks.end(); } 116 117 /// isLoopExiting - True if terminator in the block can branch to another block 118 /// that is outside of the current loop. 119 /// 120 bool isLoopExiting(const BlockT *BB) const { 121 typedef GraphTraits<BlockT*> BlockTraits; 122 for (typename BlockTraits::ChildIteratorType SI = 123 BlockTraits::child_begin(const_cast<BlockT*>(BB)), 124 SE = BlockTraits::child_end(const_cast<BlockT*>(BB)); SI != SE; ++SI) { 125 if (!contains(*SI)) 126 return true; 127 } 128 return false; 129 } 130 131 /// getNumBackEdges - Calculate the number of back edges to the loop header 132 /// 133 unsigned getNumBackEdges() const { 134 unsigned NumBackEdges = 0; 135 BlockT *H = getHeader(); 136 137 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 138 for (typename InvBlockTraits::ChildIteratorType I = 139 InvBlockTraits::child_begin(const_cast<BlockT*>(H)), 140 E = InvBlockTraits::child_end(const_cast<BlockT*>(H)); I != E; ++I) 141 if (contains(*I)) 142 ++NumBackEdges; 143 144 return NumBackEdges; 145 } 146 147 //===--------------------------------------------------------------------===// 148 // APIs for simple analysis of the loop. 149 // 150 // Note that all of these methods can fail on general loops (ie, there may not 151 // be a preheader, etc). For best success, the loop simplification and 152 // induction variable canonicalization pass should be used to normalize loops 153 // for easy analysis. These methods assume canonical loops. 154 155 /// getExitingBlocks - Return all blocks inside the loop that have successors 156 /// outside of the loop. These are the blocks _inside of the current loop_ 157 /// which branch out. The returned list is always unique. 158 /// 159 void getExitingBlocks(SmallVectorImpl<BlockT *> &ExitingBlocks) const { 160 // Sort the blocks vector so that we can use binary search to do quick 161 // lookups. 162 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 163 std::sort(LoopBBs.begin(), LoopBBs.end()); 164 165 typedef GraphTraits<BlockT*> BlockTraits; 166 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) 167 for (typename BlockTraits::ChildIteratorType I = 168 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 169 I != E; ++I) 170 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) { 171 // Not in current loop? It must be an exit block. 172 ExitingBlocks.push_back(*BI); 173 break; 174 } 175 } 176 177 /// getExitingBlock - If getExitingBlocks would return exactly one block, 178 /// return that block. Otherwise return null. 179 BlockT *getExitingBlock() const { 180 SmallVector<BlockT*, 8> ExitingBlocks; 181 getExitingBlocks(ExitingBlocks); 182 if (ExitingBlocks.size() == 1) 183 return ExitingBlocks[0]; 184 return 0; 185 } 186 187 /// getExitBlocks - Return all of the successor blocks of this loop. These 188 /// are the blocks _outside of the current loop_ which are branched to. 189 /// 190 void getExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const { 191 // Sort the blocks vector so that we can use binary search to do quick 192 // lookups. 193 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 194 std::sort(LoopBBs.begin(), LoopBBs.end()); 195 196 typedef GraphTraits<BlockT*> BlockTraits; 197 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) 198 for (typename BlockTraits::ChildIteratorType I = 199 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 200 I != E; ++I) 201 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) 202 // Not in current loop? It must be an exit block. 203 ExitBlocks.push_back(*I); 204 } 205 206 /// getExitBlock - If getExitBlocks would return exactly one block, 207 /// return that block. Otherwise return null. 208 BlockT *getExitBlock() const { 209 SmallVector<BlockT*, 8> ExitBlocks; 210 getExitBlocks(ExitBlocks); 211 if (ExitBlocks.size() == 1) 212 return ExitBlocks[0]; 213 return 0; 214 } 215 216 /// getExitEdges - Return all pairs of (_inside_block_,_outside_block_). 217 typedef std::pair<const BlockT*,const BlockT*> Edge; 218 void getExitEdges(SmallVectorImpl<Edge> &ExitEdges) const { 219 // Sort the blocks vector so that we can use binary search to do quick 220 // lookups. 221 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 222 std::sort(LoopBBs.begin(), LoopBBs.end()); 223 224 typedef GraphTraits<BlockT*> BlockTraits; 225 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) 226 for (typename BlockTraits::ChildIteratorType I = 227 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 228 I != E; ++I) 229 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) 230 // Not in current loop? It must be an exit block. 231 ExitEdges.push_back(std::make_pair(*BI, *I)); 232 } 233 234 /// getLoopPreheader - If there is a preheader for this loop, return it. A 235 /// loop has a preheader if there is only one edge to the header of the loop 236 /// from outside of the loop. If this is the case, the block branching to the 237 /// header of the loop is the preheader node. 238 /// 239 /// This method returns null if there is no preheader for the loop. 240 /// 241 BlockT *getLoopPreheader() const { 242 // Keep track of nodes outside the loop branching to the header... 243 BlockT *Out = 0; 244 245 // Loop over the predecessors of the header node... 246 BlockT *Header = getHeader(); 247 typedef GraphTraits<BlockT*> BlockTraits; 248 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 249 for (typename InvBlockTraits::ChildIteratorType PI = 250 InvBlockTraits::child_begin(Header), 251 PE = InvBlockTraits::child_end(Header); PI != PE; ++PI) 252 if (!contains(*PI)) { // If the block is not in the loop... 253 if (Out && Out != *PI) 254 return 0; // Multiple predecessors outside the loop 255 Out = *PI; 256 } 257 258 // Make sure there is only one exit out of the preheader. 259 assert(Out && "Header of loop has no predecessors from outside loop?"); 260 typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out); 261 ++SI; 262 if (SI != BlockTraits::child_end(Out)) 263 return 0; // Multiple exits from the block, must not be a preheader. 264 265 // If there is exactly one preheader, return it. If there was zero, then 266 // Out is still null. 267 return Out; 268 } 269 270 /// getLoopLatch - If there is a single latch block for this loop, return it. 271 /// A latch block is a block that contains a branch back to the header. 272 /// A loop header in normal form has two edges into it: one from a preheader 273 /// and one from a latch block. 274 BlockT *getLoopLatch() const { 275 BlockT *Header = getHeader(); 276 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 277 typename InvBlockTraits::ChildIteratorType PI = 278 InvBlockTraits::child_begin(Header); 279 typename InvBlockTraits::ChildIteratorType PE = 280 InvBlockTraits::child_end(Header); 281 if (PI == PE) return 0; // no preds? 282 283 BlockT *Latch = 0; 284 if (contains(*PI)) 285 Latch = *PI; 286 ++PI; 287 if (PI == PE) return 0; // only one pred? 288 289 if (contains(*PI)) { 290 if (Latch) return 0; // multiple backedges 291 Latch = *PI; 292 } 293 ++PI; 294 if (PI != PE) return 0; // more than two preds 295 296 return Latch; 297 } 298 299 //===--------------------------------------------------------------------===// 300 // APIs for updating loop information after changing the CFG 301 // 302 303 /// addBasicBlockToLoop - This method is used by other analyses to update loop 304 /// information. NewBB is set to be a new member of the current loop. 305 /// Because of this, it is added as a member of all parent loops, and is added 306 /// to the specified LoopInfo object as being in the current basic block. It 307 /// is not valid to replace the loop header with this method. 308 /// 309 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LI); 310 311 /// replaceChildLoopWith - This is used when splitting loops up. It replaces 312 /// the OldChild entry in our children list with NewChild, and updates the 313 /// parent pointer of OldChild to be null and the NewChild to be this loop. 314 /// This updates the loop depth of the new child. 315 void replaceChildLoopWith(LoopT *OldChild, 316 LoopT *NewChild) { 317 assert(OldChild->ParentLoop == this && "This loop is already broken!"); 318 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 319 typename std::vector<LoopT *>::iterator I = 320 std::find(SubLoops.begin(), SubLoops.end(), OldChild); 321 assert(I != SubLoops.end() && "OldChild not in loop!"); 322 *I = NewChild; 323 OldChild->ParentLoop = 0; 324 NewChild->ParentLoop = static_cast<LoopT *>(this); 325 } 326 327 /// addChildLoop - Add the specified loop to be a child of this loop. This 328 /// updates the loop depth of the new child. 329 /// 330 void addChildLoop(LoopT *NewChild) { 331 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 332 NewChild->ParentLoop = static_cast<LoopT *>(this); 333 SubLoops.push_back(NewChild); 334 } 335 336 /// removeChildLoop - This removes the specified child from being a subloop of 337 /// this loop. The loop is not deleted, as it will presumably be inserted 338 /// into another loop. 339 LoopT *removeChildLoop(iterator I) { 340 assert(I != SubLoops.end() && "Cannot remove end iterator!"); 341 LoopT *Child = *I; 342 assert(Child->ParentLoop == this && "Child is not a child of this loop!"); 343 SubLoops.erase(SubLoops.begin()+(I-begin())); 344 Child->ParentLoop = 0; 345 return Child; 346 } 347 348 /// addBlockEntry - This adds a basic block directly to the basic block list. 349 /// This should only be used by transformations that create new loops. Other 350 /// transformations should use addBasicBlockToLoop. 351 void addBlockEntry(BlockT *BB) { 352 Blocks.push_back(BB); 353 } 354 355 /// moveToHeader - This method is used to move BB (which must be part of this 356 /// loop) to be the loop header of the loop (the block that dominates all 357 /// others). 358 void moveToHeader(BlockT *BB) { 359 if (Blocks[0] == BB) return; 360 for (unsigned i = 0; ; ++i) { 361 assert(i != Blocks.size() && "Loop does not contain BB!"); 362 if (Blocks[i] == BB) { 363 Blocks[i] = Blocks[0]; 364 Blocks[0] = BB; 365 return; 366 } 367 } 368 } 369 370 /// removeBlockFromLoop - This removes the specified basic block from the 371 /// current loop, updating the Blocks as appropriate. This does not update 372 /// the mapping in the LoopInfo class. 373 void removeBlockFromLoop(BlockT *BB) { 374 RemoveFromVector(Blocks, BB); 375 } 376 377 /// verifyLoop - Verify loop structure 378 void verifyLoop() const { 379#ifndef NDEBUG 380 assert(!Blocks.empty() && "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 (isLoopExiting(BB)) OS << "<exiting>"; 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 /// hasDedicatedExits - Return true if no exit block for the loop 576 /// has a predecessor that is outside the loop. 577 bool hasDedicatedExits() const; 578 579 /// getUniqueExitBlocks - Return all unique successor blocks of this loop. 580 /// These are the blocks _outside of the current loop_ which are branched to. 581 /// This assumes that loop is in canonical form. 582 /// 583 void getUniqueExitBlocks(SmallVectorImpl<BasicBlock *> &ExitBlocks) const; 584 585 /// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one 586 /// block, return that block. Otherwise return null. 587 BasicBlock *getUniqueExitBlock() const; 588 589private: 590 friend class LoopInfoBase<BasicBlock, Loop>; 591 explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {} 592}; 593 594//===----------------------------------------------------------------------===// 595/// LoopInfo - This class builds and contains all of the top level loop 596/// structures in the specified function. 597/// 598 599template<class BlockT, class LoopT> 600class LoopInfoBase { 601 // BBMap - Mapping of basic blocks to the inner most loop they occur in 602 std::map<BlockT *, LoopT *> BBMap; 603 std::vector<LoopT *> TopLevelLoops; 604 friend class LoopBase<BlockT, LoopT>; 605 606 void operator=(const LoopInfoBase &); // do not implement 607 LoopInfoBase(const LoopInfo &); // do not implement 608public: 609 LoopInfoBase() { } 610 ~LoopInfoBase() { releaseMemory(); } 611 612 void releaseMemory() { 613 for (typename std::vector<LoopT *>::iterator I = 614 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I) 615 delete *I; // Delete all of the loops... 616 617 BBMap.clear(); // Reset internal state of analysis 618 TopLevelLoops.clear(); 619 } 620 621 /// iterator/begin/end - The interface to the top-level loops in the current 622 /// function. 623 /// 624 typedef typename std::vector<LoopT *>::const_iterator iterator; 625 iterator begin() const { return TopLevelLoops.begin(); } 626 iterator end() const { return TopLevelLoops.end(); } 627 bool empty() const { return TopLevelLoops.empty(); } 628 629 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 630 /// block is in no loop (for example the entry node), null is returned. 631 /// 632 LoopT *getLoopFor(const BlockT *BB) const { 633 typename std::map<BlockT *, LoopT *>::const_iterator I= 634 BBMap.find(const_cast<BlockT*>(BB)); 635 return I != BBMap.end() ? I->second : 0; 636 } 637 638 /// operator[] - same as getLoopFor... 639 /// 640 const LoopT *operator[](const BlockT *BB) const { 641 return getLoopFor(BB); 642 } 643 644 /// getLoopDepth - Return the loop nesting level of the specified block. A 645 /// depth of 0 means the block is not inside any loop. 646 /// 647 unsigned getLoopDepth(const BlockT *BB) const { 648 const LoopT *L = getLoopFor(BB); 649 return L ? L->getLoopDepth() : 0; 650 } 651 652 // isLoopHeader - True if the block is a loop header node 653 bool isLoopHeader(BlockT *BB) const { 654 const LoopT *L = getLoopFor(BB); 655 return L && L->getHeader() == BB; 656 } 657 658 /// removeLoop - This removes the specified top-level loop from this loop info 659 /// object. The loop is not deleted, as it will presumably be inserted into 660 /// another loop. 661 LoopT *removeLoop(iterator I) { 662 assert(I != end() && "Cannot remove end iterator!"); 663 LoopT *L = *I; 664 assert(L->getParentLoop() == 0 && "Not a top-level loop!"); 665 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin())); 666 return L; 667 } 668 669 /// changeLoopFor - Change the top-level loop that contains BB to the 670 /// specified loop. This should be used by transformations that restructure 671 /// the loop hierarchy tree. 672 void changeLoopFor(BlockT *BB, LoopT *L) { 673 LoopT *&OldLoop = BBMap[BB]; 674 assert(OldLoop && "Block not in a loop yet!"); 675 OldLoop = L; 676 } 677 678 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 679 /// list with the indicated loop. 680 void changeTopLevelLoop(LoopT *OldLoop, 681 LoopT *NewLoop) { 682 typename std::vector<LoopT *>::iterator I = 683 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop); 684 assert(I != TopLevelLoops.end() && "Old loop not at top level!"); 685 *I = NewLoop; 686 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 && 687 "Loops already embedded into a subloop!"); 688 } 689 690 /// addTopLevelLoop - This adds the specified loop to the collection of 691 /// top-level loops. 692 void addTopLevelLoop(LoopT *New) { 693 assert(New->getParentLoop() == 0 && "Loop already in subloop!"); 694 TopLevelLoops.push_back(New); 695 } 696 697 /// removeBlock - This method completely removes BB from all data structures, 698 /// including all of the Loop objects it is nested in and our mapping from 699 /// BasicBlocks to loops. 700 void removeBlock(BlockT *BB) { 701 typename std::map<BlockT *, LoopT *>::iterator I = BBMap.find(BB); 702 if (I != BBMap.end()) { 703 for (LoopT *L = I->second; L; L = L->getParentLoop()) 704 L->removeBlockFromLoop(BB); 705 706 BBMap.erase(I); 707 } 708 } 709 710 // Internals 711 712 static bool isNotAlreadyContainedIn(const LoopT *SubLoop, 713 const LoopT *ParentLoop) { 714 if (SubLoop == 0) return true; 715 if (SubLoop == ParentLoop) return false; 716 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop); 717 } 718 719 void Calculate(DominatorTreeBase<BlockT> &DT) { 720 BlockT *RootNode = DT.getRootNode()->getBlock(); 721 722 for (df_iterator<BlockT*> NI = df_begin(RootNode), 723 NE = df_end(RootNode); NI != NE; ++NI) 724 if (LoopT *L = ConsiderForLoop(*NI, DT)) 725 TopLevelLoops.push_back(L); 726 } 727 728 LoopT *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) { 729 if (BBMap.find(BB) != BBMap.end()) return 0;// Haven't processed this node? 730 731 std::vector<BlockT *> TodoStack; 732 733 // Scan the predecessors of BB, checking to see if BB dominates any of 734 // them. This identifies backedges which target this node... 735 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 736 for (typename InvBlockTraits::ChildIteratorType I = 737 InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB); 738 I != E; ++I) 739 if (DT.dominates(BB, *I)) // If BB dominates its predecessor... 740 TodoStack.push_back(*I); 741 742 if (TodoStack.empty()) return 0; // No backedges to this block... 743 744 // Create a new loop to represent this basic block... 745 LoopT *L = new LoopT(BB); 746 BBMap[BB] = L; 747 748 BlockT *EntryBlock = BB->getParent()->begin(); 749 750 while (!TodoStack.empty()) { // Process all the nodes in the loop 751 BlockT *X = TodoStack.back(); 752 TodoStack.pop_back(); 753 754 if (!L->contains(X) && // As of yet unprocessed?? 755 DT.dominates(EntryBlock, X)) { // X is reachable from entry block? 756 // Check to see if this block already belongs to a loop. If this occurs 757 // then we have a case where a loop that is supposed to be a child of 758 // the current loop was processed before the current loop. When this 759 // occurs, this child loop gets added to a part of the current loop, 760 // making it a sibling to the current loop. We have to reparent this 761 // loop. 762 if (LoopT *SubLoop = 763 const_cast<LoopT *>(getLoopFor(X))) 764 if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){ 765 // Remove the subloop from its current parent... 766 assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L); 767 LoopT *SLP = SubLoop->ParentLoop; // SubLoopParent 768 typename std::vector<LoopT *>::iterator I = 769 std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop); 770 assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?"); 771 SLP->SubLoops.erase(I); // Remove from parent... 772 773 // Add the subloop to THIS loop... 774 SubLoop->ParentLoop = L; 775 L->SubLoops.push_back(SubLoop); 776 } 777 778 // Normal case, add the block to our loop... 779 L->Blocks.push_back(X); 780 781 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 782 783 // Add all of the predecessors of X to the end of the work stack... 784 TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X), 785 InvBlockTraits::child_end(X)); 786 } 787 } 788 789 // If there are any loops nested within this loop, create them now! 790 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 791 E = L->Blocks.end(); I != E; ++I) 792 if (LoopT *NewLoop = ConsiderForLoop(*I, DT)) { 793 L->SubLoops.push_back(NewLoop); 794 NewLoop->ParentLoop = L; 795 } 796 797 // Add the basic blocks that comprise this loop to the BBMap so that this 798 // loop can be found for them. 799 // 800 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 801 E = L->Blocks.end(); I != E; ++I) 802 BBMap.insert(std::make_pair(*I, L)); 803 804 // Now that we have a list of all of the child loops of this loop, check to 805 // see if any of them should actually be nested inside of each other. We 806 // can accidentally pull loops our of their parents, so we must make sure to 807 // organize the loop nests correctly now. 808 { 809 std::map<BlockT *, LoopT *> ContainingLoops; 810 for (unsigned i = 0; i != L->SubLoops.size(); ++i) { 811 LoopT *Child = L->SubLoops[i]; 812 assert(Child->getParentLoop() == L && "Not proper child loop?"); 813 814 if (LoopT *ContainingLoop = ContainingLoops[Child->getHeader()]) { 815 // If there is already a loop which contains this loop, move this loop 816 // into the containing loop. 817 MoveSiblingLoopInto(Child, ContainingLoop); 818 --i; // The loop got removed from the SubLoops list. 819 } else { 820 // This is currently considered to be a top-level loop. Check to see 821 // if any of the contained blocks are loop headers for subloops we 822 // have already processed. 823 for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) { 824 LoopT *&BlockLoop = ContainingLoops[Child->Blocks[b]]; 825 if (BlockLoop == 0) { // Child block not processed yet... 826 BlockLoop = Child; 827 } else if (BlockLoop != Child) { 828 LoopT *SubLoop = BlockLoop; 829 // Reparent all of the blocks which used to belong to BlockLoops 830 for (unsigned j = 0, e = SubLoop->Blocks.size(); j != e; ++j) 831 ContainingLoops[SubLoop->Blocks[j]] = Child; 832 833 // There is already a loop which contains this block, that means 834 // that we should reparent the loop which the block is currently 835 // considered to belong to to be a child of this loop. 836 MoveSiblingLoopInto(SubLoop, Child); 837 --i; // We just shrunk the SubLoops list. 838 } 839 } 840 } 841 } 842 } 843 844 return L; 845 } 846 847 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside 848 /// of the NewParent Loop, instead of being a sibling of it. 849 void MoveSiblingLoopInto(LoopT *NewChild, 850 LoopT *NewParent) { 851 LoopT *OldParent = NewChild->getParentLoop(); 852 assert(OldParent && OldParent == NewParent->getParentLoop() && 853 NewChild != NewParent && "Not sibling loops!"); 854 855 // Remove NewChild from being a child of OldParent 856 typename std::vector<LoopT *>::iterator I = 857 std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(), 858 NewChild); 859 assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??"); 860 OldParent->SubLoops.erase(I); // Remove from parent's subloops list 861 NewChild->ParentLoop = 0; 862 863 InsertLoopInto(NewChild, NewParent); 864 } 865 866 /// InsertLoopInto - This inserts loop L into the specified parent loop. If 867 /// the parent loop contains a loop which should contain L, the loop gets 868 /// inserted into L instead. 869 void InsertLoopInto(LoopT *L, LoopT *Parent) { 870 BlockT *LHeader = L->getHeader(); 871 assert(Parent->contains(LHeader) && 872 "This loop should not be inserted here!"); 873 874 // Check to see if it belongs in a child loop... 875 for (unsigned i = 0, e = static_cast<unsigned>(Parent->SubLoops.size()); 876 i != e; ++i) 877 if (Parent->SubLoops[i]->contains(LHeader)) { 878 InsertLoopInto(L, Parent->SubLoops[i]); 879 return; 880 } 881 882 // If not, insert it here! 883 Parent->SubLoops.push_back(L); 884 L->ParentLoop = Parent; 885 } 886 887 // Debugging 888 889 void print(raw_ostream &OS) const { 890 for (unsigned i = 0; i < TopLevelLoops.size(); ++i) 891 TopLevelLoops[i]->print(OS); 892 #if 0 893 for (std::map<BasicBlock*, LoopT*>::const_iterator I = BBMap.begin(), 894 E = BBMap.end(); I != E; ++I) 895 OS << "BB '" << I->first->getName() << "' level = " 896 << I->second->getLoopDepth() << "\n"; 897 #endif 898 } 899}; 900 901class LoopInfo : public FunctionPass { 902 LoopInfoBase<BasicBlock, Loop> LI; 903 friend class LoopBase<BasicBlock, Loop>; 904 905 void operator=(const LoopInfo &); // do not implement 906 LoopInfo(const LoopInfo &); // do not implement 907public: 908 static char ID; // Pass identification, replacement for typeid 909 910 LoopInfo() : FunctionPass(&ID) {} 911 912 LoopInfoBase<BasicBlock, Loop>& getBase() { return LI; } 913 914 /// iterator/begin/end - The interface to the top-level loops in the current 915 /// function. 916 /// 917 typedef LoopInfoBase<BasicBlock, Loop>::iterator iterator; 918 inline iterator begin() const { return LI.begin(); } 919 inline iterator end() const { return LI.end(); } 920 bool empty() const { return LI.empty(); } 921 922 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 923 /// block is in no loop (for example the entry node), null is returned. 924 /// 925 inline Loop *getLoopFor(const BasicBlock *BB) const { 926 return LI.getLoopFor(BB); 927 } 928 929 /// operator[] - same as getLoopFor... 930 /// 931 inline const Loop *operator[](const BasicBlock *BB) const { 932 return LI.getLoopFor(BB); 933 } 934 935 /// getLoopDepth - Return the loop nesting level of the specified block. A 936 /// depth of 0 means the block is not inside any loop. 937 /// 938 inline unsigned getLoopDepth(const BasicBlock *BB) const { 939 return LI.getLoopDepth(BB); 940 } 941 942 // isLoopHeader - True if the block is a loop header node 943 inline bool isLoopHeader(BasicBlock *BB) const { 944 return LI.isLoopHeader(BB); 945 } 946 947 /// runOnFunction - Calculate the natural loop information. 948 /// 949 virtual bool runOnFunction(Function &F); 950 951 virtual void verifyAnalysis() const; 952 953 virtual void releaseMemory() { LI.releaseMemory(); } 954 955 virtual void print(raw_ostream &O, const Module* M = 0) const; 956 957 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 958 959 /// removeLoop - This removes the specified top-level loop from this loop info 960 /// object. The loop is not deleted, as it will presumably be inserted into 961 /// another loop. 962 inline Loop *removeLoop(iterator I) { return LI.removeLoop(I); } 963 964 /// changeLoopFor - Change the top-level loop that contains BB to the 965 /// specified loop. This should be used by transformations that restructure 966 /// the loop hierarchy tree. 967 inline void changeLoopFor(BasicBlock *BB, Loop *L) { 968 LI.changeLoopFor(BB, L); 969 } 970 971 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 972 /// list with the indicated loop. 973 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) { 974 LI.changeTopLevelLoop(OldLoop, NewLoop); 975 } 976 977 /// addTopLevelLoop - This adds the specified loop to the collection of 978 /// top-level loops. 979 inline void addTopLevelLoop(Loop *New) { 980 LI.addTopLevelLoop(New); 981 } 982 983 /// removeBlock - This method completely removes BB from all data structures, 984 /// including all of the Loop objects it is nested in and our mapping from 985 /// BasicBlocks to loops. 986 void removeBlock(BasicBlock *BB) { 987 LI.removeBlock(BB); 988 } 989 990 static bool isNotAlreadyContainedIn(const Loop *SubLoop, 991 const Loop *ParentLoop) { 992 return 993 LoopInfoBase<BasicBlock, Loop>::isNotAlreadyContainedIn(SubLoop, 994 ParentLoop); 995 } 996}; 997 998 999// Allow clients to walk the list of nested loops... 1000template <> struct GraphTraits<const Loop*> { 1001 typedef const Loop NodeType; 1002 typedef LoopInfo::iterator ChildIteratorType; 1003 1004 static NodeType *getEntryNode(const Loop *L) { return L; } 1005 static inline ChildIteratorType child_begin(NodeType *N) { 1006 return N->begin(); 1007 } 1008 static inline ChildIteratorType child_end(NodeType *N) { 1009 return N->end(); 1010 } 1011}; 1012 1013template <> struct GraphTraits<Loop*> { 1014 typedef Loop NodeType; 1015 typedef LoopInfo::iterator ChildIteratorType; 1016 1017 static NodeType *getEntryNode(Loop *L) { return L; } 1018 static inline ChildIteratorType child_begin(NodeType *N) { 1019 return N->begin(); 1020 } 1021 static inline ChildIteratorType child_end(NodeType *N) { 1022 return N->end(); 1023 } 1024}; 1025 1026template<class BlockT, class LoopT> 1027void 1028LoopBase<BlockT, LoopT>::addBasicBlockToLoop(BlockT *NewBB, 1029 LoopInfoBase<BlockT, LoopT> &LIB) { 1030 assert((Blocks.empty() || LIB[getHeader()] == this) && 1031 "Incorrect LI specified for this loop!"); 1032 assert(NewBB && "Cannot add a null basic block to the loop!"); 1033 assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!"); 1034 1035 LoopT *L = static_cast<LoopT *>(this); 1036 1037 // Add the loop mapping to the LoopInfo object... 1038 LIB.BBMap[NewBB] = L; 1039 1040 // Add the basic block to this loop and all parent loops... 1041 while (L) { 1042 L->Blocks.push_back(NewBB); 1043 L = L->getParentLoop(); 1044 } 1045} 1046 1047} // End llvm namespace 1048 1049#endif 1050