LoopInfo.h revision 6bec5bb344fc0374431aed1cb63418de607a1aec
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 118 /// block 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 BlockT *getLoopLatch() const { 273 BlockT *Header = getHeader(); 274 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 275 typename InvBlockTraits::ChildIteratorType PI = 276 InvBlockTraits::child_begin(Header); 277 typename InvBlockTraits::ChildIteratorType PE = 278 InvBlockTraits::child_end(Header); 279 BlockT *Latch = 0; 280 for (; PI != PE; ++PI) 281 if (contains(*PI)) { 282 if (Latch) return 0; 283 Latch = *PI; 284 } 285 286 return Latch; 287 } 288 289 //===--------------------------------------------------------------------===// 290 // APIs for updating loop information after changing the CFG 291 // 292 293 /// addBasicBlockToLoop - This method is used by other analyses to update loop 294 /// information. NewBB is set to be a new member of the current loop. 295 /// Because of this, it is added as a member of all parent loops, and is added 296 /// to the specified LoopInfo object as being in the current basic block. It 297 /// is not valid to replace the loop header with this method. 298 /// 299 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LI); 300 301 /// replaceChildLoopWith - This is used when splitting loops up. It replaces 302 /// the OldChild entry in our children list with NewChild, and updates the 303 /// parent pointer of OldChild to be null and the NewChild to be this loop. 304 /// This updates the loop depth of the new child. 305 void replaceChildLoopWith(LoopT *OldChild, 306 LoopT *NewChild) { 307 assert(OldChild->ParentLoop == this && "This loop is already broken!"); 308 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 309 typename std::vector<LoopT *>::iterator I = 310 std::find(SubLoops.begin(), SubLoops.end(), OldChild); 311 assert(I != SubLoops.end() && "OldChild not in loop!"); 312 *I = NewChild; 313 OldChild->ParentLoop = 0; 314 NewChild->ParentLoop = static_cast<LoopT *>(this); 315 } 316 317 /// addChildLoop - Add the specified loop to be a child of this loop. This 318 /// updates the loop depth of the new child. 319 /// 320 void addChildLoop(LoopT *NewChild) { 321 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 322 NewChild->ParentLoop = static_cast<LoopT *>(this); 323 SubLoops.push_back(NewChild); 324 } 325 326 /// removeChildLoop - This removes the specified child from being a subloop of 327 /// this loop. The loop is not deleted, as it will presumably be inserted 328 /// into another loop. 329 LoopT *removeChildLoop(iterator I) { 330 assert(I != SubLoops.end() && "Cannot remove end iterator!"); 331 LoopT *Child = *I; 332 assert(Child->ParentLoop == this && "Child is not a child of this loop!"); 333 SubLoops.erase(SubLoops.begin()+(I-begin())); 334 Child->ParentLoop = 0; 335 return Child; 336 } 337 338 /// addBlockEntry - This adds a basic block directly to the basic block list. 339 /// This should only be used by transformations that create new loops. Other 340 /// transformations should use addBasicBlockToLoop. 341 void addBlockEntry(BlockT *BB) { 342 Blocks.push_back(BB); 343 } 344 345 /// moveToHeader - This method is used to move BB (which must be part of this 346 /// loop) to be the loop header of the loop (the block that dominates all 347 /// others). 348 void moveToHeader(BlockT *BB) { 349 if (Blocks[0] == BB) return; 350 for (unsigned i = 0; ; ++i) { 351 assert(i != Blocks.size() && "Loop does not contain BB!"); 352 if (Blocks[i] == BB) { 353 Blocks[i] = Blocks[0]; 354 Blocks[0] = BB; 355 return; 356 } 357 } 358 } 359 360 /// removeBlockFromLoop - This removes the specified basic block from the 361 /// current loop, updating the Blocks as appropriate. This does not update 362 /// the mapping in the LoopInfo class. 363 void removeBlockFromLoop(BlockT *BB) { 364 RemoveFromVector(Blocks, BB); 365 } 366 367 /// verifyLoop - Verify loop structure 368 void verifyLoop() const { 369#ifndef NDEBUG 370 assert(!Blocks.empty() && "Loop header is missing"); 371 372 // Sort the blocks vector so that we can use binary search to do quick 373 // lookups. 374 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 375 std::sort(LoopBBs.begin(), LoopBBs.end()); 376 377 // Check the individual blocks. 378 for (block_iterator I = block_begin(), E = block_end(); I != E; ++I) { 379 BlockT *BB = *I; 380 bool HasInsideLoopSuccs = false; 381 bool HasInsideLoopPreds = false; 382 SmallVector<BlockT *, 2> OutsideLoopPreds; 383 384 typedef GraphTraits<BlockT*> BlockTraits; 385 for (typename BlockTraits::ChildIteratorType SI = 386 BlockTraits::child_begin(BB), SE = BlockTraits::child_end(BB); 387 SI != SE; ++SI) 388 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *SI)) { 389 HasInsideLoopSuccs = true; 390 break; 391 } 392 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 393 for (typename InvBlockTraits::ChildIteratorType PI = 394 InvBlockTraits::child_begin(BB), PE = InvBlockTraits::child_end(BB); 395 PI != PE; ++PI) { 396 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *PI)) 397 HasInsideLoopPreds = true; 398 else 399 OutsideLoopPreds.push_back(*PI); 400 } 401 402 if (BB == getHeader()) { 403 assert(!OutsideLoopPreds.empty() && "Loop is unreachable!"); 404 } else if (!OutsideLoopPreds.empty()) { 405 // A non-header loop shouldn't be reachable from outside the loop, 406 // though it is permitted if the predecessor is not itself actually 407 // reachable. 408 BlockT *EntryBB = BB->getParent()->begin(); 409 for (df_iterator<BlockT *> NI = df_begin(EntryBB), 410 NE = df_end(EntryBB); NI != NE; ++NI) 411 for (unsigned i = 0, e = OutsideLoopPreds.size(); i != e; ++i) 412 assert(*NI != OutsideLoopPreds[i] && 413 "Loop has multiple entry points!"); 414 } 415 assert(HasInsideLoopPreds && "Loop block has no in-loop predecessors!"); 416 assert(HasInsideLoopSuccs && "Loop block has no in-loop successors!"); 417 assert(BB != getHeader()->getParent()->begin() && 418 "Loop contains function entry block!"); 419 } 420 421 // Check the subloops. 422 for (iterator I = begin(), E = end(); I != E; ++I) 423 // Each block in each subloop should be contained within this loop. 424 for (block_iterator BI = (*I)->block_begin(), BE = (*I)->block_end(); 425 BI != BE; ++BI) { 426 assert(std::binary_search(LoopBBs.begin(), LoopBBs.end(), *BI) && 427 "Loop does not contain all the blocks of a subloop!"); 428 } 429 430 // Check the parent loop pointer. 431 if (ParentLoop) { 432 assert(std::find(ParentLoop->begin(), ParentLoop->end(), this) != 433 ParentLoop->end() && 434 "Loop is not a subloop of its parent!"); 435 } 436#endif 437 } 438 439 /// verifyLoop - Verify loop structure of this loop and all nested loops. 440 void verifyLoopNest() const { 441 // Verify this loop. 442 verifyLoop(); 443 // Verify the subloops. 444 for (iterator I = begin(), E = end(); I != E; ++I) 445 (*I)->verifyLoopNest(); 446 } 447 448 void print(raw_ostream &OS, unsigned Depth = 0) const { 449 OS.indent(Depth*2) << "Loop at depth " << getLoopDepth() 450 << " containing: "; 451 452 for (unsigned i = 0; i < getBlocks().size(); ++i) { 453 if (i) OS << ","; 454 BlockT *BB = getBlocks()[i]; 455 WriteAsOperand(OS, BB, false); 456 if (BB == getHeader()) OS << "<header>"; 457 if (BB == getLoopLatch()) OS << "<latch>"; 458 if (isLoopExiting(BB)) OS << "<exiting>"; 459 } 460 OS << "\n"; 461 462 for (iterator I = begin(), E = end(); I != E; ++I) 463 (*I)->print(OS, Depth+2); 464 } 465 466 void dump() const { 467 print(errs()); 468 } 469 470protected: 471 friend class LoopInfoBase<BlockT, LoopT>; 472 explicit LoopBase(BlockT *BB) : ParentLoop(0) { 473 Blocks.push_back(BB); 474 } 475}; 476 477class Loop : public LoopBase<BasicBlock, Loop> { 478public: 479 Loop() {} 480 481 /// isLoopInvariant - Return true if the specified value is loop invariant 482 /// 483 bool isLoopInvariant(Value *V) const; 484 485 /// isLoopInvariant - Return true if the specified instruction is 486 /// loop-invariant. 487 /// 488 bool isLoopInvariant(Instruction *I) const; 489 490 /// makeLoopInvariant - If the given value is an instruction inside of the 491 /// loop and it can be hoisted, do so to make it trivially loop-invariant. 492 /// Return true if the value after any hoisting is loop invariant. This 493 /// function can be used as a slightly more aggressive replacement for 494 /// isLoopInvariant. 495 /// 496 /// If InsertPt is specified, it is the point to hoist instructions to. 497 /// If null, the terminator of the loop preheader is used. 498 /// 499 bool makeLoopInvariant(Value *V, bool &Changed, 500 Instruction *InsertPt = 0) const; 501 502 /// makeLoopInvariant - If the given instruction is inside of the 503 /// loop and it can be hoisted, do so to make it trivially loop-invariant. 504 /// Return true if the instruction 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(Instruction *I, bool &Changed, 512 Instruction *InsertPt = 0) const; 513 514 /// getCanonicalInductionVariable - Check to see if the loop has a canonical 515 /// induction variable: an integer recurrence that starts at 0 and increments 516 /// by one each time through the loop. If so, return the phi node that 517 /// corresponds to it. 518 /// 519 /// The IndVarSimplify pass transforms loops to have a canonical induction 520 /// variable. 521 /// 522 PHINode *getCanonicalInductionVariable() const; 523 524 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds 525 /// the canonical induction variable value for the "next" iteration of the 526 /// loop. This always succeeds if getCanonicalInductionVariable succeeds. 527 /// 528 Instruction *getCanonicalInductionVariableIncrement() const; 529 530 /// getTripCount - Return a loop-invariant LLVM value indicating the number of 531 /// times the loop will be executed. Note that this means that the backedge 532 /// of the loop executes N-1 times. If the trip-count cannot be determined, 533 /// this returns null. 534 /// 535 /// The IndVarSimplify pass transforms loops to have a form that this 536 /// function easily understands. 537 /// 538 Value *getTripCount() const; 539 540 /// getSmallConstantTripCount - Returns the trip count of this loop as a 541 /// normal unsigned value, if possible. Returns 0 if the trip count is unknown 542 /// of not constant. Will also return 0 if the trip count is very large 543 /// (>= 2^32) 544 unsigned getSmallConstantTripCount() const; 545 546 /// getSmallConstantTripMultiple - Returns the largest constant divisor of the 547 /// trip count of this loop as a normal unsigned value, if possible. This 548 /// means that the actual trip count is always a multiple of the returned 549 /// value (don't forget the trip count could very well be zero as well!). 550 /// 551 /// Returns 1 if the trip count is unknown or not guaranteed to be the 552 /// multiple of a constant (which is also the case if the trip count is simply 553 /// constant, use getSmallConstantTripCount for that case), Will also return 1 554 /// if the trip count is very large (>= 2^32). 555 unsigned getSmallConstantTripMultiple() const; 556 557 /// isLCSSAForm - Return true if the Loop is in LCSSA form 558 bool isLCSSAForm() const; 559 560 /// isLoopSimplifyForm - Return true if the Loop is in the form that 561 /// the LoopSimplify form transforms loops to, which is sometimes called 562 /// normal form. 563 bool isLoopSimplifyForm() const; 564 565 /// hasDedicatedExits - Return true if no exit block for the loop 566 /// has a predecessor that is outside the loop. 567 bool hasDedicatedExits() const; 568 569 /// getUniqueExitBlocks - Return all unique successor blocks of this loop. 570 /// These are the blocks _outside of the current loop_ which are branched to. 571 /// This assumes that loop exits are in canonical form. 572 /// 573 void getUniqueExitBlocks(SmallVectorImpl<BasicBlock *> &ExitBlocks) const; 574 575 /// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one 576 /// block, return that block. Otherwise return null. 577 BasicBlock *getUniqueExitBlock() const; 578 579private: 580 friend class LoopInfoBase<BasicBlock, Loop>; 581 explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {} 582}; 583 584//===----------------------------------------------------------------------===// 585/// LoopInfo - This class builds and contains all of the top level loop 586/// structures in the specified function. 587/// 588 589template<class BlockT, class LoopT> 590class LoopInfoBase { 591 // BBMap - Mapping of basic blocks to the inner most loop they occur in 592 std::map<BlockT *, LoopT *> BBMap; 593 std::vector<LoopT *> TopLevelLoops; 594 friend class LoopBase<BlockT, LoopT>; 595 596 void operator=(const LoopInfoBase &); // do not implement 597 LoopInfoBase(const LoopInfo &); // do not implement 598public: 599 LoopInfoBase() { } 600 ~LoopInfoBase() { releaseMemory(); } 601 602 void releaseMemory() { 603 for (typename std::vector<LoopT *>::iterator I = 604 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I) 605 delete *I; // Delete all of the loops... 606 607 BBMap.clear(); // Reset internal state of analysis 608 TopLevelLoops.clear(); 609 } 610 611 /// iterator/begin/end - The interface to the top-level loops in the current 612 /// function. 613 /// 614 typedef typename std::vector<LoopT *>::const_iterator iterator; 615 iterator begin() const { return TopLevelLoops.begin(); } 616 iterator end() const { return TopLevelLoops.end(); } 617 bool empty() const { return TopLevelLoops.empty(); } 618 619 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 620 /// block is in no loop (for example the entry node), null is returned. 621 /// 622 LoopT *getLoopFor(const BlockT *BB) const { 623 typename std::map<BlockT *, LoopT *>::const_iterator I= 624 BBMap.find(const_cast<BlockT*>(BB)); 625 return I != BBMap.end() ? I->second : 0; 626 } 627 628 /// operator[] - same as getLoopFor... 629 /// 630 const LoopT *operator[](const BlockT *BB) const { 631 return getLoopFor(BB); 632 } 633 634 /// getLoopDepth - Return the loop nesting level of the specified block. A 635 /// depth of 0 means the block is not inside any loop. 636 /// 637 unsigned getLoopDepth(const BlockT *BB) const { 638 const LoopT *L = getLoopFor(BB); 639 return L ? L->getLoopDepth() : 0; 640 } 641 642 // isLoopHeader - True if the block is a loop header node 643 bool isLoopHeader(BlockT *BB) const { 644 const LoopT *L = getLoopFor(BB); 645 return L && L->getHeader() == BB; 646 } 647 648 /// removeLoop - This removes the specified top-level loop from this loop info 649 /// object. The loop is not deleted, as it will presumably be inserted into 650 /// another loop. 651 LoopT *removeLoop(iterator I) { 652 assert(I != end() && "Cannot remove end iterator!"); 653 LoopT *L = *I; 654 assert(L->getParentLoop() == 0 && "Not a top-level loop!"); 655 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin())); 656 return L; 657 } 658 659 /// changeLoopFor - Change the top-level loop that contains BB to the 660 /// specified loop. This should be used by transformations that restructure 661 /// the loop hierarchy tree. 662 void changeLoopFor(BlockT *BB, LoopT *L) { 663 LoopT *&OldLoop = BBMap[BB]; 664 assert(OldLoop && "Block not in a loop yet!"); 665 OldLoop = L; 666 } 667 668 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 669 /// list with the indicated loop. 670 void changeTopLevelLoop(LoopT *OldLoop, 671 LoopT *NewLoop) { 672 typename std::vector<LoopT *>::iterator I = 673 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop); 674 assert(I != TopLevelLoops.end() && "Old loop not at top level!"); 675 *I = NewLoop; 676 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 && 677 "Loops already embedded into a subloop!"); 678 } 679 680 /// addTopLevelLoop - This adds the specified loop to the collection of 681 /// top-level loops. 682 void addTopLevelLoop(LoopT *New) { 683 assert(New->getParentLoop() == 0 && "Loop already in subloop!"); 684 TopLevelLoops.push_back(New); 685 } 686 687 /// removeBlock - This method completely removes BB from all data structures, 688 /// including all of the Loop objects it is nested in and our mapping from 689 /// BasicBlocks to loops. 690 void removeBlock(BlockT *BB) { 691 typename std::map<BlockT *, LoopT *>::iterator I = BBMap.find(BB); 692 if (I != BBMap.end()) { 693 for (LoopT *L = I->second; L; L = L->getParentLoop()) 694 L->removeBlockFromLoop(BB); 695 696 BBMap.erase(I); 697 } 698 } 699 700 // Internals 701 702 static bool isNotAlreadyContainedIn(const LoopT *SubLoop, 703 const LoopT *ParentLoop) { 704 if (SubLoop == 0) return true; 705 if (SubLoop == ParentLoop) return false; 706 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop); 707 } 708 709 void Calculate(DominatorTreeBase<BlockT> &DT) { 710 BlockT *RootNode = DT.getRootNode()->getBlock(); 711 712 for (df_iterator<BlockT*> NI = df_begin(RootNode), 713 NE = df_end(RootNode); NI != NE; ++NI) 714 if (LoopT *L = ConsiderForLoop(*NI, DT)) 715 TopLevelLoops.push_back(L); 716 } 717 718 LoopT *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) { 719 if (BBMap.find(BB) != BBMap.end()) return 0;// Haven't processed this node? 720 721 std::vector<BlockT *> TodoStack; 722 723 // Scan the predecessors of BB, checking to see if BB dominates any of 724 // them. This identifies backedges which target this node... 725 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 726 for (typename InvBlockTraits::ChildIteratorType I = 727 InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB); 728 I != E; ++I) 729 if (DT.dominates(BB, *I)) // If BB dominates its predecessor... 730 TodoStack.push_back(*I); 731 732 if (TodoStack.empty()) return 0; // No backedges to this block... 733 734 // Create a new loop to represent this basic block... 735 LoopT *L = new LoopT(BB); 736 BBMap[BB] = L; 737 738 BlockT *EntryBlock = BB->getParent()->begin(); 739 740 while (!TodoStack.empty()) { // Process all the nodes in the loop 741 BlockT *X = TodoStack.back(); 742 TodoStack.pop_back(); 743 744 if (!L->contains(X) && // As of yet unprocessed?? 745 DT.dominates(EntryBlock, X)) { // X is reachable from entry block? 746 // Check to see if this block already belongs to a loop. If this occurs 747 // then we have a case where a loop that is supposed to be a child of 748 // the current loop was processed before the current loop. When this 749 // occurs, this child loop gets added to a part of the current loop, 750 // making it a sibling to the current loop. We have to reparent this 751 // loop. 752 if (LoopT *SubLoop = 753 const_cast<LoopT *>(getLoopFor(X))) 754 if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){ 755 // Remove the subloop from its current parent... 756 assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L); 757 LoopT *SLP = SubLoop->ParentLoop; // SubLoopParent 758 typename std::vector<LoopT *>::iterator I = 759 std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop); 760 assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?"); 761 SLP->SubLoops.erase(I); // Remove from parent... 762 763 // Add the subloop to THIS loop... 764 SubLoop->ParentLoop = L; 765 L->SubLoops.push_back(SubLoop); 766 } 767 768 // Normal case, add the block to our loop... 769 L->Blocks.push_back(X); 770 771 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 772 773 // Add all of the predecessors of X to the end of the work stack... 774 TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X), 775 InvBlockTraits::child_end(X)); 776 } 777 } 778 779 // If there are any loops nested within this loop, create them now! 780 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 781 E = L->Blocks.end(); I != E; ++I) 782 if (LoopT *NewLoop = ConsiderForLoop(*I, DT)) { 783 L->SubLoops.push_back(NewLoop); 784 NewLoop->ParentLoop = L; 785 } 786 787 // Add the basic blocks that comprise this loop to the BBMap so that this 788 // loop can be found for them. 789 // 790 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 791 E = L->Blocks.end(); I != E; ++I) 792 BBMap.insert(std::make_pair(*I, L)); 793 794 // Now that we have a list of all of the child loops of this loop, check to 795 // see if any of them should actually be nested inside of each other. We 796 // can accidentally pull loops our of their parents, so we must make sure to 797 // organize the loop nests correctly now. 798 { 799 std::map<BlockT *, LoopT *> ContainingLoops; 800 for (unsigned i = 0; i != L->SubLoops.size(); ++i) { 801 LoopT *Child = L->SubLoops[i]; 802 assert(Child->getParentLoop() == L && "Not proper child loop?"); 803 804 if (LoopT *ContainingLoop = ContainingLoops[Child->getHeader()]) { 805 // If there is already a loop which contains this loop, move this loop 806 // into the containing loop. 807 MoveSiblingLoopInto(Child, ContainingLoop); 808 --i; // The loop got removed from the SubLoops list. 809 } else { 810 // This is currently considered to be a top-level loop. Check to see 811 // if any of the contained blocks are loop headers for subloops we 812 // have already processed. 813 for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) { 814 LoopT *&BlockLoop = ContainingLoops[Child->Blocks[b]]; 815 if (BlockLoop == 0) { // Child block not processed yet... 816 BlockLoop = Child; 817 } else if (BlockLoop != Child) { 818 LoopT *SubLoop = BlockLoop; 819 // Reparent all of the blocks which used to belong to BlockLoops 820 for (unsigned j = 0, e = SubLoop->Blocks.size(); j != e; ++j) 821 ContainingLoops[SubLoop->Blocks[j]] = Child; 822 823 // There is already a loop which contains this block, that means 824 // that we should reparent the loop which the block is currently 825 // considered to belong to to be a child of this loop. 826 MoveSiblingLoopInto(SubLoop, Child); 827 --i; // We just shrunk the SubLoops list. 828 } 829 } 830 } 831 } 832 } 833 834 return L; 835 } 836 837 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside 838 /// of the NewParent Loop, instead of being a sibling of it. 839 void MoveSiblingLoopInto(LoopT *NewChild, 840 LoopT *NewParent) { 841 LoopT *OldParent = NewChild->getParentLoop(); 842 assert(OldParent && OldParent == NewParent->getParentLoop() && 843 NewChild != NewParent && "Not sibling loops!"); 844 845 // Remove NewChild from being a child of OldParent 846 typename std::vector<LoopT *>::iterator I = 847 std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(), 848 NewChild); 849 assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??"); 850 OldParent->SubLoops.erase(I); // Remove from parent's subloops list 851 NewChild->ParentLoop = 0; 852 853 InsertLoopInto(NewChild, NewParent); 854 } 855 856 /// InsertLoopInto - This inserts loop L into the specified parent loop. If 857 /// the parent loop contains a loop which should contain L, the loop gets 858 /// inserted into L instead. 859 void InsertLoopInto(LoopT *L, LoopT *Parent) { 860 BlockT *LHeader = L->getHeader(); 861 assert(Parent->contains(LHeader) && 862 "This loop should not be inserted here!"); 863 864 // Check to see if it belongs in a child loop... 865 for (unsigned i = 0, e = static_cast<unsigned>(Parent->SubLoops.size()); 866 i != e; ++i) 867 if (Parent->SubLoops[i]->contains(LHeader)) { 868 InsertLoopInto(L, Parent->SubLoops[i]); 869 return; 870 } 871 872 // If not, insert it here! 873 Parent->SubLoops.push_back(L); 874 L->ParentLoop = Parent; 875 } 876 877 // Debugging 878 879 void print(raw_ostream &OS) const { 880 for (unsigned i = 0; i < TopLevelLoops.size(); ++i) 881 TopLevelLoops[i]->print(OS); 882 #if 0 883 for (std::map<BasicBlock*, LoopT*>::const_iterator I = BBMap.begin(), 884 E = BBMap.end(); I != E; ++I) 885 OS << "BB '" << I->first->getName() << "' level = " 886 << I->second->getLoopDepth() << "\n"; 887 #endif 888 } 889}; 890 891class LoopInfo : public FunctionPass { 892 LoopInfoBase<BasicBlock, Loop> LI; 893 friend class LoopBase<BasicBlock, Loop>; 894 895 void operator=(const LoopInfo &); // do not implement 896 LoopInfo(const LoopInfo &); // do not implement 897public: 898 static char ID; // Pass identification, replacement for typeid 899 900 LoopInfo() : FunctionPass(&ID) {} 901 902 LoopInfoBase<BasicBlock, Loop>& getBase() { return LI; } 903 904 /// iterator/begin/end - The interface to the top-level loops in the current 905 /// function. 906 /// 907 typedef LoopInfoBase<BasicBlock, Loop>::iterator iterator; 908 inline iterator begin() const { return LI.begin(); } 909 inline iterator end() const { return LI.end(); } 910 bool empty() const { return LI.empty(); } 911 912 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 913 /// block is in no loop (for example the entry node), null is returned. 914 /// 915 inline Loop *getLoopFor(const BasicBlock *BB) const { 916 return LI.getLoopFor(BB); 917 } 918 919 /// operator[] - same as getLoopFor... 920 /// 921 inline const Loop *operator[](const BasicBlock *BB) const { 922 return LI.getLoopFor(BB); 923 } 924 925 /// getLoopDepth - Return the loop nesting level of the specified block. A 926 /// depth of 0 means the block is not inside any loop. 927 /// 928 inline unsigned getLoopDepth(const BasicBlock *BB) const { 929 return LI.getLoopDepth(BB); 930 } 931 932 // isLoopHeader - True if the block is a loop header node 933 inline bool isLoopHeader(BasicBlock *BB) const { 934 return LI.isLoopHeader(BB); 935 } 936 937 /// runOnFunction - Calculate the natural loop information. 938 /// 939 virtual bool runOnFunction(Function &F); 940 941 virtual void verifyAnalysis() const; 942 943 virtual void releaseMemory() { LI.releaseMemory(); } 944 945 virtual void print(raw_ostream &O, const Module* M = 0) const; 946 947 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 948 949 /// removeLoop - This removes the specified top-level loop from this loop info 950 /// object. The loop is not deleted, as it will presumably be inserted into 951 /// another loop. 952 inline Loop *removeLoop(iterator I) { return LI.removeLoop(I); } 953 954 /// changeLoopFor - Change the top-level loop that contains BB to the 955 /// specified loop. This should be used by transformations that restructure 956 /// the loop hierarchy tree. 957 inline void changeLoopFor(BasicBlock *BB, Loop *L) { 958 LI.changeLoopFor(BB, L); 959 } 960 961 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 962 /// list with the indicated loop. 963 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) { 964 LI.changeTopLevelLoop(OldLoop, NewLoop); 965 } 966 967 /// addTopLevelLoop - This adds the specified loop to the collection of 968 /// top-level loops. 969 inline void addTopLevelLoop(Loop *New) { 970 LI.addTopLevelLoop(New); 971 } 972 973 /// removeBlock - This method completely removes BB from all data structures, 974 /// including all of the Loop objects it is nested in and our mapping from 975 /// BasicBlocks to loops. 976 void removeBlock(BasicBlock *BB) { 977 LI.removeBlock(BB); 978 } 979}; 980 981 982// Allow clients to walk the list of nested loops... 983template <> struct GraphTraits<const Loop*> { 984 typedef const Loop NodeType; 985 typedef LoopInfo::iterator ChildIteratorType; 986 987 static NodeType *getEntryNode(const Loop *L) { return L; } 988 static inline ChildIteratorType child_begin(NodeType *N) { 989 return N->begin(); 990 } 991 static inline ChildIteratorType child_end(NodeType *N) { 992 return N->end(); 993 } 994}; 995 996template <> struct GraphTraits<Loop*> { 997 typedef Loop NodeType; 998 typedef LoopInfo::iterator ChildIteratorType; 999 1000 static NodeType *getEntryNode(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<class BlockT, class LoopT> 1010void 1011LoopBase<BlockT, LoopT>::addBasicBlockToLoop(BlockT *NewBB, 1012 LoopInfoBase<BlockT, LoopT> &LIB) { 1013 assert((Blocks.empty() || LIB[getHeader()] == this) && 1014 "Incorrect LI specified for this loop!"); 1015 assert(NewBB && "Cannot add a null basic block to the loop!"); 1016 assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!"); 1017 1018 LoopT *L = static_cast<LoopT *>(this); 1019 1020 // Add the loop mapping to the LoopInfo object... 1021 LIB.BBMap[NewBB] = L; 1022 1023 // Add the basic block to this loop and all parent loops... 1024 while (L) { 1025 L->Blocks.push_back(NewBB); 1026 L = L->getParentLoop(); 1027 } 1028} 1029 1030} // End llvm namespace 1031 1032#endif 1033