LoopInfo.h revision 45cfe545ec8177262dabc70580ce05feaa1c3880
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/Streams.h" 40#include <algorithm> 41#include <ostream> 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 /// isLoopExit - True if terminator in the block can branch to another block 118 /// that is outside of the current loop. 119 /// 120 bool isLoopExit(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 /// (Modelled after getExitingBlocks().) 218 typedef std::pair<const BlockT*,const BlockT*> Edge; 219 void getExitEdges(SmallVectorImpl<Edge> &ExitEdges) const { 220 // Sort the blocks vector so that we can use binary search to do quick 221 // lookups. 222 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 223 std::sort(LoopBBs.begin(), LoopBBs.end()); 224 225 typedef GraphTraits<BlockT*> BlockTraits; 226 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) 227 for (typename BlockTraits::ChildIteratorType I = 228 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 229 I != E; ++I) 230 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) 231 // Not in current loop? It must be an exit block. 232 ExitEdges.push_back(std::make_pair(*BI, *I)); 233 } 234 235 /// getUniqueExitBlocks - Return all unique successor blocks of this loop. 236 /// These are the blocks _outside of the current loop_ which are branched to. 237 /// This assumes that loop is in canonical form. 238 /// 239 void getUniqueExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const { 240 // Sort the blocks vector so that we can use binary search to do quick 241 // lookups. 242 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 243 std::sort(LoopBBs.begin(), LoopBBs.end()); 244 245 std::vector<BlockT*> switchExitBlocks; 246 247 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) { 248 249 BlockT *current = *BI; 250 switchExitBlocks.clear(); 251 252 typedef GraphTraits<BlockT*> BlockTraits; 253 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 254 for (typename BlockTraits::ChildIteratorType I = 255 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 256 I != E; ++I) { 257 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) 258 // If block is inside the loop then it is not a exit block. 259 continue; 260 261 typename InvBlockTraits::ChildIteratorType PI = 262 InvBlockTraits::child_begin(*I); 263 BlockT *firstPred = *PI; 264 265 // If current basic block is this exit block's first predecessor 266 // then only insert exit block in to the output ExitBlocks vector. 267 // This ensures that same exit block is not inserted twice into 268 // ExitBlocks vector. 269 if (current != firstPred) 270 continue; 271 272 // If a terminator has more then two successors, for example SwitchInst, 273 // then it is possible that there are multiple edges from current block 274 // to one exit block. 275 if (std::distance(BlockTraits::child_begin(current), 276 BlockTraits::child_end(current)) <= 2) { 277 ExitBlocks.push_back(*I); 278 continue; 279 } 280 281 // In case of multiple edges from current block to exit block, collect 282 // only one edge in ExitBlocks. Use switchExitBlocks to keep track of 283 // duplicate edges. 284 if (std::find(switchExitBlocks.begin(), switchExitBlocks.end(), *I) 285 == switchExitBlocks.end()) { 286 switchExitBlocks.push_back(*I); 287 ExitBlocks.push_back(*I); 288 } 289 } 290 } 291 } 292 293 /// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one 294 /// block, return that block. Otherwise return null. 295 BlockT *getUniqueExitBlock() const { 296 SmallVector<BlockT*, 8> UniqueExitBlocks; 297 getUniqueExitBlocks(UniqueExitBlocks); 298 if (UniqueExitBlocks.size() == 1) 299 return UniqueExitBlocks[0]; 300 return 0; 301 } 302 303 /// getLoopPreheader - If there is a preheader for this loop, return it. A 304 /// loop has a preheader if there is only one edge to the header of the loop 305 /// from outside of the loop. If this is the case, the block branching to the 306 /// header of the loop is the preheader node. 307 /// 308 /// This method returns null if there is no preheader for the loop. 309 /// 310 BlockT *getLoopPreheader() const { 311 // Keep track of nodes outside the loop branching to the header... 312 BlockT *Out = 0; 313 314 // Loop over the predecessors of the header node... 315 BlockT *Header = getHeader(); 316 typedef GraphTraits<BlockT*> BlockTraits; 317 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 318 for (typename InvBlockTraits::ChildIteratorType PI = 319 InvBlockTraits::child_begin(Header), 320 PE = InvBlockTraits::child_end(Header); PI != PE; ++PI) 321 if (!contains(*PI)) { // If the block is not in the loop... 322 if (Out && Out != *PI) 323 return 0; // Multiple predecessors outside the loop 324 Out = *PI; 325 } 326 327 // Make sure there is only one exit out of the preheader. 328 assert(Out && "Header of loop has no predecessors from outside loop?"); 329 typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out); 330 ++SI; 331 if (SI != BlockTraits::child_end(Out)) 332 return 0; // Multiple exits from the block, must not be a preheader. 333 334 // If there is exactly one preheader, return it. If there was zero, then 335 // Out is still null. 336 return Out; 337 } 338 339 /// getLoopLatch - If there is a single latch block for this loop, return it. 340 /// A latch block is a block that contains a branch back to the header. 341 /// A loop header in normal form has two edges into it: one from a preheader 342 /// and one from a latch block. 343 BlockT *getLoopLatch() const { 344 BlockT *Header = getHeader(); 345 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 346 typename InvBlockTraits::ChildIteratorType PI = 347 InvBlockTraits::child_begin(Header); 348 typename InvBlockTraits::ChildIteratorType PE = 349 InvBlockTraits::child_end(Header); 350 if (PI == PE) return 0; // no preds? 351 352 BlockT *Latch = 0; 353 if (contains(*PI)) 354 Latch = *PI; 355 ++PI; 356 if (PI == PE) return 0; // only one pred? 357 358 if (contains(*PI)) { 359 if (Latch) return 0; // multiple backedges 360 Latch = *PI; 361 } 362 ++PI; 363 if (PI != PE) return 0; // more than two preds 364 365 return Latch; 366 } 367 368 //===--------------------------------------------------------------------===// 369 // APIs for updating loop information after changing the CFG 370 // 371 372 /// addBasicBlockToLoop - This method is used by other analyses to update loop 373 /// information. NewBB is set to be a new member of the current loop. 374 /// Because of this, it is added as a member of all parent loops, and is added 375 /// to the specified LoopInfo object as being in the current basic block. It 376 /// is not valid to replace the loop header with this method. 377 /// 378 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LI); 379 380 /// replaceChildLoopWith - This is used when splitting loops up. It replaces 381 /// the OldChild entry in our children list with NewChild, and updates the 382 /// parent pointer of OldChild to be null and the NewChild to be this loop. 383 /// This updates the loop depth of the new child. 384 void replaceChildLoopWith(LoopT *OldChild, 385 LoopT *NewChild) { 386 assert(OldChild->ParentLoop == this && "This loop is already broken!"); 387 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 388 typename std::vector<LoopT *>::iterator I = 389 std::find(SubLoops.begin(), SubLoops.end(), OldChild); 390 assert(I != SubLoops.end() && "OldChild not in loop!"); 391 *I = NewChild; 392 OldChild->ParentLoop = 0; 393 NewChild->ParentLoop = static_cast<LoopT *>(this); 394 } 395 396 /// addChildLoop - Add the specified loop to be a child of this loop. This 397 /// updates the loop depth of the new child. 398 /// 399 void addChildLoop(LoopT *NewChild) { 400 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 401 NewChild->ParentLoop = static_cast<LoopT *>(this); 402 SubLoops.push_back(NewChild); 403 } 404 405 /// removeChildLoop - This removes the specified child from being a subloop of 406 /// this loop. The loop is not deleted, as it will presumably be inserted 407 /// into another loop. 408 LoopT *removeChildLoop(iterator I) { 409 assert(I != SubLoops.end() && "Cannot remove end iterator!"); 410 LoopT *Child = *I; 411 assert(Child->ParentLoop == this && "Child is not a child of this loop!"); 412 SubLoops.erase(SubLoops.begin()+(I-begin())); 413 Child->ParentLoop = 0; 414 return Child; 415 } 416 417 /// addBlockEntry - This adds a basic block directly to the basic block list. 418 /// This should only be used by transformations that create new loops. Other 419 /// transformations should use addBasicBlockToLoop. 420 void addBlockEntry(BlockT *BB) { 421 Blocks.push_back(BB); 422 } 423 424 /// moveToHeader - This method is used to move BB (which must be part of this 425 /// loop) to be the loop header of the loop (the block that dominates all 426 /// others). 427 void moveToHeader(BlockT *BB) { 428 if (Blocks[0] == BB) return; 429 for (unsigned i = 0; ; ++i) { 430 assert(i != Blocks.size() && "Loop does not contain BB!"); 431 if (Blocks[i] == BB) { 432 Blocks[i] = Blocks[0]; 433 Blocks[0] = BB; 434 return; 435 } 436 } 437 } 438 439 /// removeBlockFromLoop - This removes the specified basic block from the 440 /// current loop, updating the Blocks as appropriate. This does not update 441 /// the mapping in the LoopInfo class. 442 void removeBlockFromLoop(BlockT *BB) { 443 RemoveFromVector(Blocks, BB); 444 } 445 446 /// verifyLoop - Verify loop structure 447 void verifyLoop() const { 448#ifndef NDEBUG 449 assert (getHeader() && "Loop header is missing"); 450 assert (getLoopPreheader() && "Loop preheader is missing"); 451 assert (getLoopLatch() && "Loop latch is missing"); 452 for (iterator I = SubLoops.begin(), E = SubLoops.end(); I != E; ++I) 453 (*I)->verifyLoop(); 454#endif 455 } 456 457 void print(raw_ostream &OS, unsigned Depth = 0) const { 458 OS.indent(Depth*2) << "Loop at depth " << getLoopDepth() 459 << " containing: "; 460 461 for (unsigned i = 0; i < getBlocks().size(); ++i) { 462 if (i) OS << ","; 463 BlockT *BB = getBlocks()[i]; 464 WriteAsOperand(OS, BB, false); 465 if (BB == getHeader()) OS << "<header>"; 466 if (BB == getLoopLatch()) OS << "<latch>"; 467 if (isLoopExit(BB)) OS << "<exit>"; 468 } 469 OS << "\n"; 470 471 for (iterator I = begin(), E = end(); I != E; ++I) 472 (*I)->print(OS, Depth+2); 473 } 474 475 void dump() const { 476 print(errs()); 477 } 478 479protected: 480 friend class LoopInfoBase<BlockT, LoopT>; 481 explicit LoopBase(BlockT *BB) : ParentLoop(0) { 482 Blocks.push_back(BB); 483 } 484}; 485 486class Loop : public LoopBase<BasicBlock, Loop> { 487public: 488 Loop() {} 489 490 /// isLoopInvariant - Return true if the specified value is loop invariant 491 /// 492 bool isLoopInvariant(Value *V) const; 493 494 /// isLoopInvariant - Return true if the specified instruction is 495 /// loop-invariant. 496 /// 497 bool isLoopInvariant(Instruction *I) const; 498 499 /// makeLoopInvariant - If the given value is an instruction inside of the 500 /// loop and it can be hoisted, do so to make it trivially loop-invariant. 501 /// Return true if the value after any hoisting is loop invariant. This 502 /// function can be used as a slightly more aggressive replacement for 503 /// isLoopInvariant. 504 /// 505 /// If InsertPt is specified, it is the point to hoist instructions to. 506 /// If null, the terminator of the loop preheader is used. 507 /// 508 bool makeLoopInvariant(Value *V, bool &Changed, 509 Instruction *InsertPt = 0) const; 510 511 /// makeLoopInvariant - If the given instruction is inside of the 512 /// loop and it can be hoisted, do so to make it trivially loop-invariant. 513 /// Return true if the instruction after any hoisting is loop invariant. This 514 /// function can be used as a slightly more aggressive replacement for 515 /// isLoopInvariant. 516 /// 517 /// If InsertPt is specified, it is the point to hoist instructions to. 518 /// If null, the terminator of the loop preheader is used. 519 /// 520 bool makeLoopInvariant(Instruction *I, bool &Changed, 521 Instruction *InsertPt = 0) const; 522 523 /// getCanonicalInductionVariable - Check to see if the loop has a canonical 524 /// induction variable: an integer recurrence that starts at 0 and increments 525 /// by one each time through the loop. If so, return the phi node that 526 /// corresponds to it. 527 /// 528 /// The IndVarSimplify pass transforms loops to have a canonical induction 529 /// variable. 530 /// 531 PHINode *getCanonicalInductionVariable() const; 532 533 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds 534 /// the canonical induction variable value for the "next" iteration of the 535 /// loop. This always succeeds if getCanonicalInductionVariable succeeds. 536 /// 537 Instruction *getCanonicalInductionVariableIncrement() const; 538 539 /// getTripCount - Return a loop-invariant LLVM value indicating the number of 540 /// times the loop will be executed. Note that this means that the backedge 541 /// of the loop executes N-1 times. If the trip-count cannot be determined, 542 /// this returns null. 543 /// 544 /// The IndVarSimplify pass transforms loops to have a form that this 545 /// function easily understands. 546 /// 547 Value *getTripCount() const; 548 549 /// getSmallConstantTripCount - Returns the trip count of this loop as a 550 /// normal unsigned value, if possible. Returns 0 if the trip count is unknown 551 /// of not constant. Will also return 0 if the trip count is very large 552 /// (>= 2^32) 553 unsigned getSmallConstantTripCount() const; 554 555 /// getSmallConstantTripMultiple - Returns the largest constant divisor of the 556 /// trip count of this loop as a normal unsigned value, if possible. This 557 /// means that the actual trip count is always a multiple of the returned 558 /// value (don't forget the trip count could very well be zero as well!). 559 /// 560 /// Returns 1 if the trip count is unknown or not guaranteed to be the 561 /// multiple of a constant (which is also the case if the trip count is simply 562 /// constant, use getSmallConstantTripCount for that case), Will also return 1 563 /// if the trip count is very large (>= 2^32). 564 unsigned getSmallConstantTripMultiple() const; 565 566 /// isLCSSAForm - Return true if the Loop is in LCSSA form 567 bool isLCSSAForm() const; 568 569 /// isLoopSimplifyForm - Return true if the Loop is in the form that 570 /// the LoopSimplify form transforms loops to, which is sometimes called 571 /// normal form. 572 bool isLoopSimplifyForm() const; 573 574private: 575 friend class LoopInfoBase<BasicBlock, Loop>; 576 explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {} 577}; 578 579//===----------------------------------------------------------------------===// 580/// LoopInfo - This class builds and contains all of the top level loop 581/// structures in the specified function. 582/// 583 584template<class BlockT, class LoopT> 585class LoopInfoBase { 586 // BBMap - Mapping of basic blocks to the inner most loop they occur in 587 std::map<BlockT *, LoopT *> BBMap; 588 std::vector<LoopT *> TopLevelLoops; 589 friend class LoopBase<BlockT, LoopT>; 590 591 void operator=(const LoopInfoBase &); // do not implement 592 LoopInfoBase(const LoopInfo &); // do not implement 593public: 594 LoopInfoBase() { } 595 ~LoopInfoBase() { releaseMemory(); } 596 597 void releaseMemory() { 598 for (typename std::vector<LoopT *>::iterator I = 599 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I) 600 delete *I; // Delete all of the loops... 601 602 BBMap.clear(); // Reset internal state of analysis 603 TopLevelLoops.clear(); 604 } 605 606 /// iterator/begin/end - The interface to the top-level loops in the current 607 /// function. 608 /// 609 typedef typename std::vector<LoopT *>::const_iterator iterator; 610 iterator begin() const { return TopLevelLoops.begin(); } 611 iterator end() const { return TopLevelLoops.end(); } 612 bool empty() const { return TopLevelLoops.empty(); } 613 614 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 615 /// block is in no loop (for example the entry node), null is returned. 616 /// 617 LoopT *getLoopFor(const BlockT *BB) const { 618 typename std::map<BlockT *, LoopT *>::const_iterator I= 619 BBMap.find(const_cast<BlockT*>(BB)); 620 return I != BBMap.end() ? I->second : 0; 621 } 622 623 /// operator[] - same as getLoopFor... 624 /// 625 const LoopT *operator[](const BlockT *BB) const { 626 return getLoopFor(BB); 627 } 628 629 /// getLoopDepth - Return the loop nesting level of the specified block. A 630 /// depth of 0 means the block is not inside any loop. 631 /// 632 unsigned getLoopDepth(const BlockT *BB) const { 633 const LoopT *L = getLoopFor(BB); 634 return L ? L->getLoopDepth() : 0; 635 } 636 637 // isLoopHeader - True if the block is a loop header node 638 bool isLoopHeader(BlockT *BB) const { 639 const LoopT *L = getLoopFor(BB); 640 return L && L->getHeader() == BB; 641 } 642 643 /// removeLoop - This removes the specified top-level loop from this loop info 644 /// object. The loop is not deleted, as it will presumably be inserted into 645 /// another loop. 646 LoopT *removeLoop(iterator I) { 647 assert(I != end() && "Cannot remove end iterator!"); 648 LoopT *L = *I; 649 assert(L->getParentLoop() == 0 && "Not a top-level loop!"); 650 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin())); 651 return L; 652 } 653 654 /// changeLoopFor - Change the top-level loop that contains BB to the 655 /// specified loop. This should be used by transformations that restructure 656 /// the loop hierarchy tree. 657 void changeLoopFor(BlockT *BB, LoopT *L) { 658 LoopT *&OldLoop = BBMap[BB]; 659 assert(OldLoop && "Block not in a loop yet!"); 660 OldLoop = L; 661 } 662 663 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 664 /// list with the indicated loop. 665 void changeTopLevelLoop(LoopT *OldLoop, 666 LoopT *NewLoop) { 667 typename std::vector<LoopT *>::iterator I = 668 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop); 669 assert(I != TopLevelLoops.end() && "Old loop not at top level!"); 670 *I = NewLoop; 671 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 && 672 "Loops already embedded into a subloop!"); 673 } 674 675 /// addTopLevelLoop - This adds the specified loop to the collection of 676 /// top-level loops. 677 void addTopLevelLoop(LoopT *New) { 678 assert(New->getParentLoop() == 0 && "Loop already in subloop!"); 679 TopLevelLoops.push_back(New); 680 } 681 682 /// removeBlock - This method completely removes BB from all data structures, 683 /// including all of the Loop objects it is nested in and our mapping from 684 /// BasicBlocks to loops. 685 void removeBlock(BlockT *BB) { 686 typename std::map<BlockT *, LoopT *>::iterator I = BBMap.find(BB); 687 if (I != BBMap.end()) { 688 for (LoopT *L = I->second; L; L = L->getParentLoop()) 689 L->removeBlockFromLoop(BB); 690 691 BBMap.erase(I); 692 } 693 } 694 695 // Internals 696 697 static bool isNotAlreadyContainedIn(const LoopT *SubLoop, 698 const LoopT *ParentLoop) { 699 if (SubLoop == 0) return true; 700 if (SubLoop == ParentLoop) return false; 701 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop); 702 } 703 704 void Calculate(DominatorTreeBase<BlockT> &DT) { 705 BlockT *RootNode = DT.getRootNode()->getBlock(); 706 707 for (df_iterator<BlockT*> NI = df_begin(RootNode), 708 NE = df_end(RootNode); NI != NE; ++NI) 709 if (LoopT *L = ConsiderForLoop(*NI, DT)) 710 TopLevelLoops.push_back(L); 711 } 712 713 LoopT *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) { 714 if (BBMap.find(BB) != BBMap.end()) return 0;// Haven't processed this node? 715 716 std::vector<BlockT *> TodoStack; 717 718 // Scan the predecessors of BB, checking to see if BB dominates any of 719 // them. This identifies backedges which target this node... 720 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 721 for (typename InvBlockTraits::ChildIteratorType I = 722 InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB); 723 I != E; ++I) 724 if (DT.dominates(BB, *I)) // If BB dominates it's predecessor... 725 TodoStack.push_back(*I); 726 727 if (TodoStack.empty()) return 0; // No backedges to this block... 728 729 // Create a new loop to represent this basic block... 730 LoopT *L = new LoopT(BB); 731 BBMap[BB] = L; 732 733 BlockT *EntryBlock = BB->getParent()->begin(); 734 735 while (!TodoStack.empty()) { // Process all the nodes in the loop 736 BlockT *X = TodoStack.back(); 737 TodoStack.pop_back(); 738 739 if (!L->contains(X) && // As of yet unprocessed?? 740 DT.dominates(EntryBlock, X)) { // X is reachable from entry block? 741 // Check to see if this block already belongs to a loop. If this occurs 742 // then we have a case where a loop that is supposed to be a child of 743 // the current loop was processed before the current loop. When this 744 // occurs, this child loop gets added to a part of the current loop, 745 // making it a sibling to the current loop. We have to reparent this 746 // loop. 747 if (LoopT *SubLoop = 748 const_cast<LoopT *>(getLoopFor(X))) 749 if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){ 750 // Remove the subloop from it's current parent... 751 assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L); 752 LoopT *SLP = SubLoop->ParentLoop; // SubLoopParent 753 typename std::vector<LoopT *>::iterator I = 754 std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop); 755 assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?"); 756 SLP->SubLoops.erase(I); // Remove from parent... 757 758 // Add the subloop to THIS loop... 759 SubLoop->ParentLoop = L; 760 L->SubLoops.push_back(SubLoop); 761 } 762 763 // Normal case, add the block to our loop... 764 L->Blocks.push_back(X); 765 766 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 767 768 // Add all of the predecessors of X to the end of the work stack... 769 TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X), 770 InvBlockTraits::child_end(X)); 771 } 772 } 773 774 // If there are any loops nested within this loop, create them now! 775 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 776 E = L->Blocks.end(); I != E; ++I) 777 if (LoopT *NewLoop = ConsiderForLoop(*I, DT)) { 778 L->SubLoops.push_back(NewLoop); 779 NewLoop->ParentLoop = L; 780 } 781 782 // Add the basic blocks that comprise this loop to the BBMap so that this 783 // loop can be found for them. 784 // 785 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 786 E = L->Blocks.end(); I != E; ++I) { 787 typename std::map<BlockT*, LoopT *>::iterator BBMI = BBMap.find(*I); 788 if (BBMI == BBMap.end()) // Not in map yet... 789 BBMap.insert(BBMI, std::make_pair(*I, L)); // Must be at this level 790 } 791 792 // Now that we have a list of all of the child loops of this loop, check to 793 // see if any of them should actually be nested inside of each other. We 794 // can accidentally pull loops our of their parents, so we must make sure to 795 // organize the loop nests correctly now. 796 { 797 std::map<BlockT *, LoopT *> ContainingLoops; 798 for (unsigned i = 0; i != L->SubLoops.size(); ++i) { 799 LoopT *Child = L->SubLoops[i]; 800 assert(Child->getParentLoop() == L && "Not proper child loop?"); 801 802 if (LoopT *ContainingLoop = ContainingLoops[Child->getHeader()]) { 803 // If there is already a loop which contains this loop, move this loop 804 // into the containing loop. 805 MoveSiblingLoopInto(Child, ContainingLoop); 806 --i; // The loop got removed from the SubLoops list. 807 } else { 808 // This is currently considered to be a top-level loop. Check to see 809 // if any of the contained blocks are loop headers for subloops we 810 // have already processed. 811 for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) { 812 LoopT *&BlockLoop = ContainingLoops[Child->Blocks[b]]; 813 if (BlockLoop == 0) { // Child block not processed yet... 814 BlockLoop = Child; 815 } else if (BlockLoop != Child) { 816 LoopT *SubLoop = BlockLoop; 817 // Reparent all of the blocks which used to belong to BlockLoops 818 for (unsigned j = 0, e = SubLoop->Blocks.size(); j != e; ++j) 819 ContainingLoops[SubLoop->Blocks[j]] = Child; 820 821 // There is already a loop which contains this block, that means 822 // that we should reparent the loop which the block is currently 823 // considered to belong to to be a child of this loop. 824 MoveSiblingLoopInto(SubLoop, Child); 825 --i; // We just shrunk the SubLoops list. 826 } 827 } 828 } 829 } 830 } 831 832 return L; 833 } 834 835 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside 836 /// of the NewParent Loop, instead of being a sibling of it. 837 void MoveSiblingLoopInto(LoopT *NewChild, 838 LoopT *NewParent) { 839 LoopT *OldParent = NewChild->getParentLoop(); 840 assert(OldParent && OldParent == NewParent->getParentLoop() && 841 NewChild != NewParent && "Not sibling loops!"); 842 843 // Remove NewChild from being a child of OldParent 844 typename std::vector<LoopT *>::iterator I = 845 std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(), 846 NewChild); 847 assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??"); 848 OldParent->SubLoops.erase(I); // Remove from parent's subloops list 849 NewChild->ParentLoop = 0; 850 851 InsertLoopInto(NewChild, NewParent); 852 } 853 854 /// InsertLoopInto - This inserts loop L into the specified parent loop. If 855 /// the parent loop contains a loop which should contain L, the loop gets 856 /// inserted into L instead. 857 void InsertLoopInto(LoopT *L, LoopT *Parent) { 858 BlockT *LHeader = L->getHeader(); 859 assert(Parent->contains(LHeader) && 860 "This loop should not be inserted here!"); 861 862 // Check to see if it belongs in a child loop... 863 for (unsigned i = 0, e = static_cast<unsigned>(Parent->SubLoops.size()); 864 i != e; ++i) 865 if (Parent->SubLoops[i]->contains(LHeader)) { 866 InsertLoopInto(L, Parent->SubLoops[i]); 867 return; 868 } 869 870 // If not, insert it here! 871 Parent->SubLoops.push_back(L); 872 L->ParentLoop = Parent; 873 } 874 875 // Debugging 876 877 void print(raw_ostream &OS) const { 878 for (unsigned i = 0; i < TopLevelLoops.size(); ++i) 879 TopLevelLoops[i]->print(OS); 880 #if 0 881 for (std::map<BasicBlock*, LoopT*>::const_iterator I = BBMap.begin(), 882 E = BBMap.end(); I != E; ++I) 883 OS << "BB '" << I->first->getName() << "' level = " 884 << I->second->getLoopDepth() << "\n"; 885 #endif 886 } 887}; 888 889class LoopInfo : public FunctionPass { 890 LoopInfoBase<BasicBlock, Loop> LI; 891 friend class LoopBase<BasicBlock, Loop>; 892 893 void operator=(const LoopInfo &); // do not implement 894 LoopInfo(const LoopInfo &); // do not implement 895public: 896 static char ID; // Pass identification, replacement for typeid 897 898 LoopInfo() : FunctionPass(&ID) {} 899 900 LoopInfoBase<BasicBlock, Loop>& getBase() { return LI; } 901 902 /// iterator/begin/end - The interface to the top-level loops in the current 903 /// function. 904 /// 905 typedef LoopInfoBase<BasicBlock, Loop>::iterator iterator; 906 inline iterator begin() const { return LI.begin(); } 907 inline iterator end() const { return LI.end(); } 908 bool empty() const { return LI.empty(); } 909 910 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 911 /// block is in no loop (for example the entry node), null is returned. 912 /// 913 inline Loop *getLoopFor(const BasicBlock *BB) const { 914 return LI.getLoopFor(BB); 915 } 916 917 /// operator[] - same as getLoopFor... 918 /// 919 inline const Loop *operator[](const BasicBlock *BB) const { 920 return LI.getLoopFor(BB); 921 } 922 923 /// getLoopDepth - Return the loop nesting level of the specified block. A 924 /// depth of 0 means the block is not inside any loop. 925 /// 926 inline unsigned getLoopDepth(const BasicBlock *BB) const { 927 return LI.getLoopDepth(BB); 928 } 929 930 // isLoopHeader - True if the block is a loop header node 931 inline bool isLoopHeader(BasicBlock *BB) const { 932 return LI.isLoopHeader(BB); 933 } 934 935 /// runOnFunction - Calculate the natural loop information. 936 /// 937 virtual bool runOnFunction(Function &F); 938 939 virtual void releaseMemory() { LI.releaseMemory(); } 940 941 virtual void print(raw_ostream &O, const Module* M = 0) const; 942 943 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 944 945 /// removeLoop - This removes the specified top-level loop from this loop info 946 /// object. The loop is not deleted, as it will presumably be inserted into 947 /// another loop. 948 inline Loop *removeLoop(iterator I) { return LI.removeLoop(I); } 949 950 /// changeLoopFor - Change the top-level loop that contains BB to the 951 /// specified loop. This should be used by transformations that restructure 952 /// the loop hierarchy tree. 953 inline void changeLoopFor(BasicBlock *BB, Loop *L) { 954 LI.changeLoopFor(BB, L); 955 } 956 957 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 958 /// list with the indicated loop. 959 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) { 960 LI.changeTopLevelLoop(OldLoop, NewLoop); 961 } 962 963 /// addTopLevelLoop - This adds the specified loop to the collection of 964 /// top-level loops. 965 inline void addTopLevelLoop(Loop *New) { 966 LI.addTopLevelLoop(New); 967 } 968 969 /// removeBlock - This method completely removes BB from all data structures, 970 /// including all of the Loop objects it is nested in and our mapping from 971 /// BasicBlocks to loops. 972 void removeBlock(BasicBlock *BB) { 973 LI.removeBlock(BB); 974 } 975 976 static bool isNotAlreadyContainedIn(const Loop *SubLoop, 977 const Loop *ParentLoop) { 978 return 979 LoopInfoBase<BasicBlock, Loop>::isNotAlreadyContainedIn(SubLoop, 980 ParentLoop); 981 } 982}; 983 984 985// Allow clients to walk the list of nested loops... 986template <> struct GraphTraits<const Loop*> { 987 typedef const Loop NodeType; 988 typedef LoopInfo::iterator ChildIteratorType; 989 990 static NodeType *getEntryNode(const Loop *L) { return L; } 991 static inline ChildIteratorType child_begin(NodeType *N) { 992 return N->begin(); 993 } 994 static inline ChildIteratorType child_end(NodeType *N) { 995 return N->end(); 996 } 997}; 998 999template <> struct GraphTraits<Loop*> { 1000 typedef Loop NodeType; 1001 typedef LoopInfo::iterator ChildIteratorType; 1002 1003 static NodeType *getEntryNode(Loop *L) { return L; } 1004 static inline ChildIteratorType child_begin(NodeType *N) { 1005 return N->begin(); 1006 } 1007 static inline ChildIteratorType child_end(NodeType *N) { 1008 return N->end(); 1009 } 1010}; 1011 1012template<class BlockT, class LoopT> 1013void 1014LoopBase<BlockT, LoopT>::addBasicBlockToLoop(BlockT *NewBB, 1015 LoopInfoBase<BlockT, LoopT> &LIB) { 1016 assert((Blocks.empty() || LIB[getHeader()] == this) && 1017 "Incorrect LI specified for this loop!"); 1018 assert(NewBB && "Cannot add a null basic block to the loop!"); 1019 assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!"); 1020 1021 LoopT *L = static_cast<LoopT *>(this); 1022 1023 // Add the loop mapping to the LoopInfo object... 1024 LIB.BBMap[NewBB] = L; 1025 1026 // Add the basic block to this loop and all parent loops... 1027 while (L) { 1028 L->Blocks.push_back(NewBB); 1029 L = L->getParentLoop(); 1030 } 1031} 1032 1033} // End llvm namespace 1034 1035#endif 1036