LoopInfo.h revision ff271e13539a43e804cab4457821a46a8bddc2ec
1//===- llvm/Analysis/LoopInfo.h - Natural Loop Calculator -------*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file defines the LoopInfo class that is used to identify natural loops 11// and determine the loop depth of various nodes of the CFG. Note that natural 12// loops may actually be several loops that share the same header node. 13// 14// This analysis calculates the nesting structure of loops in a function. For 15// each natural loop identified, this analysis identifies natural loops 16// contained entirely within the loop and the basic blocks the make up the loop. 17// 18// It can calculate on the fly various bits of information, for example: 19// 20// * whether there is a preheader for the loop 21// * the number of back edges to the header 22// * whether or not a particular block branches out of the loop 23// * the successor blocks of the loop 24// * the loop depth 25// * the trip count 26// * etc... 27// 28//===----------------------------------------------------------------------===// 29 30#ifndef LLVM_ANALYSIS_LOOP_INFO_H 31#define LLVM_ANALYSIS_LOOP_INFO_H 32 33#include "llvm/Pass.h" 34#include "llvm/ADT/DepthFirstIterator.h" 35#include "llvm/ADT/GraphTraits.h" 36#include "llvm/ADT/SmallVector.h" 37#include "llvm/Analysis/Dominators.h" 38#include "llvm/Support/CFG.h" 39#include "llvm/Support/raw_ostream.h" 40#include <algorithm> 41 42namespace llvm { 43 44template<typename T> 45static void RemoveFromVector(std::vector<T*> &V, T *N) { 46 typename std::vector<T*>::iterator I = std::find(V.begin(), V.end(), N); 47 assert(I != V.end() && "N is not in this list!"); 48 V.erase(I); 49} 50 51class DominatorTree; 52class LoopInfo; 53class Loop; 54template<class N, class M> class LoopInfoBase; 55template<class N, class M> class LoopBase; 56 57//===----------------------------------------------------------------------===// 58/// LoopBase class - Instances of this class are used to represent loops that 59/// are detected in the flow graph 60/// 61template<class BlockT, class LoopT> 62class LoopBase { 63 LoopT *ParentLoop; 64 // SubLoops - Loops contained entirely within this one. 65 std::vector<LoopT *> SubLoops; 66 67 // Blocks - The list of blocks in this loop. First entry is the header node. 68 std::vector<BlockT*> Blocks; 69 70 // DO NOT IMPLEMENT 71 LoopBase(const LoopBase<BlockT, LoopT> &); 72 // DO NOT IMPLEMENT 73 const LoopBase<BlockT, LoopT>&operator=(const LoopBase<BlockT, LoopT> &); 74public: 75 /// Loop ctor - This creates an empty loop. 76 LoopBase() : ParentLoop(0) {} 77 ~LoopBase() { 78 for (size_t i = 0, e = SubLoops.size(); i != e; ++i) 79 delete SubLoops[i]; 80 } 81 82 /// getLoopDepth - Return the nesting level of this loop. An outer-most 83 /// loop has depth 1, for consistency with loop depth values used for basic 84 /// blocks, where depth 0 is used for blocks not inside any loops. 85 unsigned getLoopDepth() const { 86 unsigned D = 1; 87 for (const LoopT *CurLoop = ParentLoop; CurLoop; 88 CurLoop = CurLoop->ParentLoop) 89 ++D; 90 return D; 91 } 92 BlockT *getHeader() const { return Blocks.front(); } 93 LoopT *getParentLoop() const { return ParentLoop; } 94 95 /// contains - Return true if the specified basic block is in this loop 96 /// 97 bool contains(const BlockT *BB) const { 98 return std::find(block_begin(), block_end(), BB) != block_end(); 99 } 100 101 /// iterator/begin/end - Return the loops contained entirely within this loop. 102 /// 103 const std::vector<LoopT *> &getSubLoops() const { return SubLoops; } 104 typedef typename std::vector<LoopT *>::const_iterator iterator; 105 iterator begin() const { return SubLoops.begin(); } 106 iterator end() const { return SubLoops.end(); } 107 bool empty() const { return SubLoops.empty(); } 108 109 /// getBlocks - Get a list of the basic blocks which make up this loop. 110 /// 111 const std::vector<BlockT*> &getBlocks() const { return Blocks; } 112 typedef typename std::vector<BlockT*>::const_iterator block_iterator; 113 block_iterator block_begin() const { return Blocks.begin(); } 114 block_iterator block_end() const { return Blocks.end(); } 115 116 /// isLoopExit - True if terminator in the block can branch to another block 117 /// that is outside of the current loop. 118 /// 119 bool isLoopExit(const BlockT *BB) const { 120 typedef GraphTraits<BlockT*> BlockTraits; 121 for (typename BlockTraits::ChildIteratorType SI = 122 BlockTraits::child_begin(const_cast<BlockT*>(BB)), 123 SE = BlockTraits::child_end(const_cast<BlockT*>(BB)); SI != SE; ++SI) { 124 if (!contains(*SI)) 125 return true; 126 } 127 return false; 128 } 129 130 /// getNumBackEdges - Calculate the number of back edges to the loop header 131 /// 132 unsigned getNumBackEdges() const { 133 unsigned NumBackEdges = 0; 134 BlockT *H = getHeader(); 135 136 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 137 for (typename InvBlockTraits::ChildIteratorType I = 138 InvBlockTraits::child_begin(const_cast<BlockT*>(H)), 139 E = InvBlockTraits::child_end(const_cast<BlockT*>(H)); I != E; ++I) 140 if (contains(*I)) 141 ++NumBackEdges; 142 143 return NumBackEdges; 144 } 145 146 //===--------------------------------------------------------------------===// 147 // APIs for simple analysis of the loop. 148 // 149 // Note that all of these methods can fail on general loops (ie, there may not 150 // be a preheader, etc). For best success, the loop simplification and 151 // induction variable canonicalization pass should be used to normalize loops 152 // for easy analysis. These methods assume canonical loops. 153 154 /// getExitingBlocks - Return all blocks inside the loop that have successors 155 /// outside of the loop. These are the blocks _inside of the current loop_ 156 /// which branch out. The returned list is always unique. 157 /// 158 void getExitingBlocks(SmallVectorImpl<BlockT *> &ExitingBlocks) const { 159 // Sort the blocks vector so that we can use binary search to do quick 160 // lookups. 161 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 162 std::sort(LoopBBs.begin(), LoopBBs.end()); 163 164 typedef GraphTraits<BlockT*> BlockTraits; 165 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) 166 for (typename BlockTraits::ChildIteratorType I = 167 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 168 I != E; ++I) 169 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) { 170 // Not in current loop? It must be an exit block. 171 ExitingBlocks.push_back(*BI); 172 break; 173 } 174 } 175 176 /// getExitingBlock - If getExitingBlocks would return exactly one block, 177 /// return that block. Otherwise return null. 178 BlockT *getExitingBlock() const { 179 SmallVector<BlockT*, 8> ExitingBlocks; 180 getExitingBlocks(ExitingBlocks); 181 if (ExitingBlocks.size() == 1) 182 return ExitingBlocks[0]; 183 return 0; 184 } 185 186 /// getExitBlocks - Return all of the successor blocks of this loop. These 187 /// are the blocks _outside of the current loop_ which are branched to. 188 /// 189 void getExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const { 190 // Sort the blocks vector so that we can use binary search to do quick 191 // lookups. 192 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 193 std::sort(LoopBBs.begin(), LoopBBs.end()); 194 195 typedef GraphTraits<BlockT*> BlockTraits; 196 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) 197 for (typename BlockTraits::ChildIteratorType I = 198 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 199 I != E; ++I) 200 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) 201 // Not in current loop? It must be an exit block. 202 ExitBlocks.push_back(*I); 203 } 204 205 /// getExitBlock - If getExitBlocks would return exactly one block, 206 /// return that block. Otherwise return null. 207 BlockT *getExitBlock() const { 208 SmallVector<BlockT*, 8> ExitBlocks; 209 getExitBlocks(ExitBlocks); 210 if (ExitBlocks.size() == 1) 211 return ExitBlocks[0]; 212 return 0; 213 } 214 215 /// getExitEdges - Return all pairs of (_inside_block_,_outside_block_). 216 typedef std::pair<const BlockT*,const BlockT*> Edge; 217 void getExitEdges(SmallVectorImpl<Edge> &ExitEdges) const { 218 // Sort the blocks vector so that we can use binary search to do quick 219 // lookups. 220 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 221 std::sort(LoopBBs.begin(), LoopBBs.end()); 222 223 typedef GraphTraits<BlockT*> BlockTraits; 224 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) 225 for (typename BlockTraits::ChildIteratorType I = 226 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 227 I != E; ++I) 228 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) 229 // Not in current loop? It must be an exit block. 230 ExitEdges.push_back(std::make_pair(*BI, *I)); 231 } 232 233 /// getUniqueExitBlocks - Return all unique successor blocks of this loop. 234 /// These are the blocks _outside of the current loop_ which are branched to. 235 /// This assumes that loop is in canonical form. 236 /// 237 void getUniqueExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const { 238 // Sort the blocks vector so that we can use binary search to do quick 239 // lookups. 240 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 241 std::sort(LoopBBs.begin(), LoopBBs.end()); 242 243 std::vector<BlockT*> switchExitBlocks; 244 245 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) { 246 247 BlockT *current = *BI; 248 switchExitBlocks.clear(); 249 250 typedef GraphTraits<BlockT*> BlockTraits; 251 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 252 for (typename BlockTraits::ChildIteratorType I = 253 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 254 I != E; ++I) { 255 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) 256 // If block is inside the loop then it is not a exit block. 257 continue; 258 259 typename InvBlockTraits::ChildIteratorType PI = 260 InvBlockTraits::child_begin(*I); 261 BlockT *firstPred = *PI; 262 263 // If current basic block is this exit block's first predecessor 264 // then only insert exit block in to the output ExitBlocks vector. 265 // This ensures that same exit block is not inserted twice into 266 // ExitBlocks vector. 267 if (current != firstPred) 268 continue; 269 270 // If a terminator has more then two successors, for example SwitchInst, 271 // then it is possible that there are multiple edges from current block 272 // to one exit block. 273 if (std::distance(BlockTraits::child_begin(current), 274 BlockTraits::child_end(current)) <= 2) { 275 ExitBlocks.push_back(*I); 276 continue; 277 } 278 279 // In case of multiple edges from current block to exit block, collect 280 // only one edge in ExitBlocks. Use switchExitBlocks to keep track of 281 // duplicate edges. 282 if (std::find(switchExitBlocks.begin(), switchExitBlocks.end(), *I) 283 == switchExitBlocks.end()) { 284 switchExitBlocks.push_back(*I); 285 ExitBlocks.push_back(*I); 286 } 287 } 288 } 289 } 290 291 /// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one 292 /// block, return that block. Otherwise return null. 293 BlockT *getUniqueExitBlock() const { 294 SmallVector<BlockT*, 8> UniqueExitBlocks; 295 getUniqueExitBlocks(UniqueExitBlocks); 296 if (UniqueExitBlocks.size() == 1) 297 return UniqueExitBlocks[0]; 298 return 0; 299 } 300 301 /// getLoopPreheader - If there is a preheader for this loop, return it. A 302 /// loop has a preheader if there is only one edge to the header of the loop 303 /// from outside of the loop. If this is the case, the block branching to the 304 /// header of the loop is the preheader node. 305 /// 306 /// This method returns null if there is no preheader for the loop. 307 /// 308 BlockT *getLoopPreheader() const { 309 // Keep track of nodes outside the loop branching to the header... 310 BlockT *Out = 0; 311 312 // Loop over the predecessors of the header node... 313 BlockT *Header = getHeader(); 314 typedef GraphTraits<BlockT*> BlockTraits; 315 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 316 for (typename InvBlockTraits::ChildIteratorType PI = 317 InvBlockTraits::child_begin(Header), 318 PE = InvBlockTraits::child_end(Header); PI != PE; ++PI) 319 if (!contains(*PI)) { // If the block is not in the loop... 320 if (Out && Out != *PI) 321 return 0; // Multiple predecessors outside the loop 322 Out = *PI; 323 } 324 325 // Make sure there is only one exit out of the preheader. 326 assert(Out && "Header of loop has no predecessors from outside loop?"); 327 typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out); 328 ++SI; 329 if (SI != BlockTraits::child_end(Out)) 330 return 0; // Multiple exits from the block, must not be a preheader. 331 332 // If there is exactly one preheader, return it. If there was zero, then 333 // Out is still null. 334 return Out; 335 } 336 337 /// getLoopLatch - If there is a single latch block for this loop, return it. 338 /// A latch block is a block that contains a branch back to the header. 339 /// A loop header in normal form has two edges into it: one from a preheader 340 /// and one from a latch block. 341 BlockT *getLoopLatch() const { 342 BlockT *Header = getHeader(); 343 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 344 typename InvBlockTraits::ChildIteratorType PI = 345 InvBlockTraits::child_begin(Header); 346 typename InvBlockTraits::ChildIteratorType PE = 347 InvBlockTraits::child_end(Header); 348 if (PI == PE) return 0; // no preds? 349 350 BlockT *Latch = 0; 351 if (contains(*PI)) 352 Latch = *PI; 353 ++PI; 354 if (PI == PE) return 0; // only one pred? 355 356 if (contains(*PI)) { 357 if (Latch) return 0; // multiple backedges 358 Latch = *PI; 359 } 360 ++PI; 361 if (PI != PE) return 0; // more than two preds 362 363 return Latch; 364 } 365 366 //===--------------------------------------------------------------------===// 367 // APIs for updating loop information after changing the CFG 368 // 369 370 /// addBasicBlockToLoop - This method is used by other analyses to update loop 371 /// information. NewBB is set to be a new member of the current loop. 372 /// Because of this, it is added as a member of all parent loops, and is added 373 /// to the specified LoopInfo object as being in the current basic block. It 374 /// is not valid to replace the loop header with this method. 375 /// 376 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LI); 377 378 /// replaceChildLoopWith - This is used when splitting loops up. It replaces 379 /// the OldChild entry in our children list with NewChild, and updates the 380 /// parent pointer of OldChild to be null and the NewChild to be this loop. 381 /// This updates the loop depth of the new child. 382 void replaceChildLoopWith(LoopT *OldChild, 383 LoopT *NewChild) { 384 assert(OldChild->ParentLoop == this && "This loop is already broken!"); 385 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 386 typename std::vector<LoopT *>::iterator I = 387 std::find(SubLoops.begin(), SubLoops.end(), OldChild); 388 assert(I != SubLoops.end() && "OldChild not in loop!"); 389 *I = NewChild; 390 OldChild->ParentLoop = 0; 391 NewChild->ParentLoop = static_cast<LoopT *>(this); 392 } 393 394 /// addChildLoop - Add the specified loop to be a child of this loop. This 395 /// updates the loop depth of the new child. 396 /// 397 void addChildLoop(LoopT *NewChild) { 398 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 399 NewChild->ParentLoop = static_cast<LoopT *>(this); 400 SubLoops.push_back(NewChild); 401 } 402 403 /// removeChildLoop - This removes the specified child from being a subloop of 404 /// this loop. The loop is not deleted, as it will presumably be inserted 405 /// into another loop. 406 LoopT *removeChildLoop(iterator I) { 407 assert(I != SubLoops.end() && "Cannot remove end iterator!"); 408 LoopT *Child = *I; 409 assert(Child->ParentLoop == this && "Child is not a child of this loop!"); 410 SubLoops.erase(SubLoops.begin()+(I-begin())); 411 Child->ParentLoop = 0; 412 return Child; 413 } 414 415 /// addBlockEntry - This adds a basic block directly to the basic block list. 416 /// This should only be used by transformations that create new loops. Other 417 /// transformations should use addBasicBlockToLoop. 418 void addBlockEntry(BlockT *BB) { 419 Blocks.push_back(BB); 420 } 421 422 /// moveToHeader - This method is used to move BB (which must be part of this 423 /// loop) to be the loop header of the loop (the block that dominates all 424 /// others). 425 void moveToHeader(BlockT *BB) { 426 if (Blocks[0] == BB) return; 427 for (unsigned i = 0; ; ++i) { 428 assert(i != Blocks.size() && "Loop does not contain BB!"); 429 if (Blocks[i] == BB) { 430 Blocks[i] = Blocks[0]; 431 Blocks[0] = BB; 432 return; 433 } 434 } 435 } 436 437 /// removeBlockFromLoop - This removes the specified basic block from the 438 /// current loop, updating the Blocks as appropriate. This does not update 439 /// the mapping in the LoopInfo class. 440 void removeBlockFromLoop(BlockT *BB) { 441 RemoveFromVector(Blocks, BB); 442 } 443 444 /// verifyLoop - Verify loop structure 445 void verifyLoop() const { 446#ifndef NDEBUG 447 assert (getHeader() && "Loop header is missing"); 448 assert (getLoopPreheader() && "Loop preheader is missing"); 449 assert (getLoopLatch() && "Loop latch is missing"); 450 for (iterator I = SubLoops.begin(), E = SubLoops.end(); I != E; ++I) 451 (*I)->verifyLoop(); 452#endif 453 } 454 455 void print(raw_ostream &OS, unsigned Depth = 0) const { 456 OS.indent(Depth*2) << "Loop at depth " << getLoopDepth() 457 << " containing: "; 458 459 for (unsigned i = 0; i < getBlocks().size(); ++i) { 460 if (i) OS << ","; 461 BlockT *BB = getBlocks()[i]; 462 WriteAsOperand(OS, BB, false); 463 if (BB == getHeader()) OS << "<header>"; 464 if (BB == getLoopLatch()) OS << "<latch>"; 465 if (isLoopExit(BB)) OS << "<exit>"; 466 } 467 OS << "\n"; 468 469 for (iterator I = begin(), E = end(); I != E; ++I) 470 (*I)->print(OS, Depth+2); 471 } 472 473 void dump() const { 474 print(errs()); 475 } 476 477protected: 478 friend class LoopInfoBase<BlockT, LoopT>; 479 explicit LoopBase(BlockT *BB) : ParentLoop(0) { 480 Blocks.push_back(BB); 481 } 482}; 483 484class Loop : public LoopBase<BasicBlock, Loop> { 485public: 486 Loop() {} 487 488 /// isLoopInvariant - Return true if the specified value is loop invariant 489 /// 490 bool isLoopInvariant(Value *V) const; 491 492 /// isLoopInvariant - Return true if the specified instruction is 493 /// loop-invariant. 494 /// 495 bool isLoopInvariant(Instruction *I) const; 496 497 /// makeLoopInvariant - If the given value is an instruction inside of the 498 /// loop and it can be hoisted, do so to make it trivially loop-invariant. 499 /// Return true if the value after any hoisting is loop invariant. This 500 /// function can be used as a slightly more aggressive replacement for 501 /// isLoopInvariant. 502 /// 503 /// If InsertPt is specified, it is the point to hoist instructions to. 504 /// If null, the terminator of the loop preheader is used. 505 /// 506 bool makeLoopInvariant(Value *V, bool &Changed, 507 Instruction *InsertPt = 0) const; 508 509 /// makeLoopInvariant - If the given instruction is inside of the 510 /// loop and it can be hoisted, do so to make it trivially loop-invariant. 511 /// Return true if the instruction after any hoisting is loop invariant. This 512 /// function can be used as a slightly more aggressive replacement for 513 /// isLoopInvariant. 514 /// 515 /// If InsertPt is specified, it is the point to hoist instructions to. 516 /// If null, the terminator of the loop preheader is used. 517 /// 518 bool makeLoopInvariant(Instruction *I, bool &Changed, 519 Instruction *InsertPt = 0) const; 520 521 /// getCanonicalInductionVariable - Check to see if the loop has a canonical 522 /// induction variable: an integer recurrence that starts at 0 and increments 523 /// by one each time through the loop. If so, return the phi node that 524 /// corresponds to it. 525 /// 526 /// The IndVarSimplify pass transforms loops to have a canonical induction 527 /// variable. 528 /// 529 PHINode *getCanonicalInductionVariable() const; 530 531 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds 532 /// the canonical induction variable value for the "next" iteration of the 533 /// loop. This always succeeds if getCanonicalInductionVariable succeeds. 534 /// 535 Instruction *getCanonicalInductionVariableIncrement() const; 536 537 /// getTripCount - Return a loop-invariant LLVM value indicating the number of 538 /// times the loop will be executed. Note that this means that the backedge 539 /// of the loop executes N-1 times. If the trip-count cannot be determined, 540 /// this returns null. 541 /// 542 /// The IndVarSimplify pass transforms loops to have a form that this 543 /// function easily understands. 544 /// 545 Value *getTripCount() const; 546 547 /// getSmallConstantTripCount - Returns the trip count of this loop as a 548 /// normal unsigned value, if possible. Returns 0 if the trip count is unknown 549 /// of not constant. Will also return 0 if the trip count is very large 550 /// (>= 2^32) 551 unsigned getSmallConstantTripCount() const; 552 553 /// getSmallConstantTripMultiple - Returns the largest constant divisor of the 554 /// trip count of this loop as a normal unsigned value, if possible. This 555 /// means that the actual trip count is always a multiple of the returned 556 /// value (don't forget the trip count could very well be zero as well!). 557 /// 558 /// Returns 1 if the trip count is unknown or not guaranteed to be the 559 /// multiple of a constant (which is also the case if the trip count is simply 560 /// constant, use getSmallConstantTripCount for that case), Will also return 1 561 /// if the trip count is very large (>= 2^32). 562 unsigned getSmallConstantTripMultiple() const; 563 564 /// isLCSSAForm - Return true if the Loop is in LCSSA form 565 bool isLCSSAForm() const; 566 567 /// isLoopSimplifyForm - Return true if the Loop is in the form that 568 /// the LoopSimplify form transforms loops to, which is sometimes called 569 /// normal form. 570 bool isLoopSimplifyForm() const; 571 572private: 573 friend class LoopInfoBase<BasicBlock, Loop>; 574 explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {} 575}; 576 577//===----------------------------------------------------------------------===// 578/// LoopInfo - This class builds and contains all of the top level loop 579/// structures in the specified function. 580/// 581 582template<class BlockT, class LoopT> 583class LoopInfoBase { 584 // BBMap - Mapping of basic blocks to the inner most loop they occur in 585 std::map<BlockT *, LoopT *> BBMap; 586 std::vector<LoopT *> TopLevelLoops; 587 friend class LoopBase<BlockT, LoopT>; 588 589 void operator=(const LoopInfoBase &); // do not implement 590 LoopInfoBase(const LoopInfo &); // do not implement 591public: 592 LoopInfoBase() { } 593 ~LoopInfoBase() { releaseMemory(); } 594 595 void releaseMemory() { 596 for (typename std::vector<LoopT *>::iterator I = 597 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I) 598 delete *I; // Delete all of the loops... 599 600 BBMap.clear(); // Reset internal state of analysis 601 TopLevelLoops.clear(); 602 } 603 604 /// iterator/begin/end - The interface to the top-level loops in the current 605 /// function. 606 /// 607 typedef typename std::vector<LoopT *>::const_iterator iterator; 608 iterator begin() const { return TopLevelLoops.begin(); } 609 iterator end() const { return TopLevelLoops.end(); } 610 bool empty() const { return TopLevelLoops.empty(); } 611 612 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 613 /// block is in no loop (for example the entry node), null is returned. 614 /// 615 LoopT *getLoopFor(const BlockT *BB) const { 616 typename std::map<BlockT *, LoopT *>::const_iterator I= 617 BBMap.find(const_cast<BlockT*>(BB)); 618 return I != BBMap.end() ? I->second : 0; 619 } 620 621 /// operator[] - same as getLoopFor... 622 /// 623 const LoopT *operator[](const BlockT *BB) const { 624 return getLoopFor(BB); 625 } 626 627 /// getLoopDepth - Return the loop nesting level of the specified block. A 628 /// depth of 0 means the block is not inside any loop. 629 /// 630 unsigned getLoopDepth(const BlockT *BB) const { 631 const LoopT *L = getLoopFor(BB); 632 return L ? L->getLoopDepth() : 0; 633 } 634 635 // isLoopHeader - True if the block is a loop header node 636 bool isLoopHeader(BlockT *BB) const { 637 const LoopT *L = getLoopFor(BB); 638 return L && L->getHeader() == BB; 639 } 640 641 /// removeLoop - This removes the specified top-level loop from this loop info 642 /// object. The loop is not deleted, as it will presumably be inserted into 643 /// another loop. 644 LoopT *removeLoop(iterator I) { 645 assert(I != end() && "Cannot remove end iterator!"); 646 LoopT *L = *I; 647 assert(L->getParentLoop() == 0 && "Not a top-level loop!"); 648 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin())); 649 return L; 650 } 651 652 /// changeLoopFor - Change the top-level loop that contains BB to the 653 /// specified loop. This should be used by transformations that restructure 654 /// the loop hierarchy tree. 655 void changeLoopFor(BlockT *BB, LoopT *L) { 656 LoopT *&OldLoop = BBMap[BB]; 657 assert(OldLoop && "Block not in a loop yet!"); 658 OldLoop = L; 659 } 660 661 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 662 /// list with the indicated loop. 663 void changeTopLevelLoop(LoopT *OldLoop, 664 LoopT *NewLoop) { 665 typename std::vector<LoopT *>::iterator I = 666 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop); 667 assert(I != TopLevelLoops.end() && "Old loop not at top level!"); 668 *I = NewLoop; 669 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 && 670 "Loops already embedded into a subloop!"); 671 } 672 673 /// addTopLevelLoop - This adds the specified loop to the collection of 674 /// top-level loops. 675 void addTopLevelLoop(LoopT *New) { 676 assert(New->getParentLoop() == 0 && "Loop already in subloop!"); 677 TopLevelLoops.push_back(New); 678 } 679 680 /// removeBlock - This method completely removes BB from all data structures, 681 /// including all of the Loop objects it is nested in and our mapping from 682 /// BasicBlocks to loops. 683 void removeBlock(BlockT *BB) { 684 typename std::map<BlockT *, LoopT *>::iterator I = BBMap.find(BB); 685 if (I != BBMap.end()) { 686 for (LoopT *L = I->second; L; L = L->getParentLoop()) 687 L->removeBlockFromLoop(BB); 688 689 BBMap.erase(I); 690 } 691 } 692 693 // Internals 694 695 static bool isNotAlreadyContainedIn(const LoopT *SubLoop, 696 const LoopT *ParentLoop) { 697 if (SubLoop == 0) return true; 698 if (SubLoop == ParentLoop) return false; 699 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop); 700 } 701 702 void Calculate(DominatorTreeBase<BlockT> &DT) { 703 BlockT *RootNode = DT.getRootNode()->getBlock(); 704 705 for (df_iterator<BlockT*> NI = df_begin(RootNode), 706 NE = df_end(RootNode); NI != NE; ++NI) 707 if (LoopT *L = ConsiderForLoop(*NI, DT)) 708 TopLevelLoops.push_back(L); 709 } 710 711 LoopT *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) { 712 if (BBMap.find(BB) != BBMap.end()) return 0;// Haven't processed this node? 713 714 std::vector<BlockT *> TodoStack; 715 716 // Scan the predecessors of BB, checking to see if BB dominates any of 717 // them. This identifies backedges which target this node... 718 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 719 for (typename InvBlockTraits::ChildIteratorType I = 720 InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB); 721 I != E; ++I) 722 if (DT.dominates(BB, *I)) // If BB dominates it's predecessor... 723 TodoStack.push_back(*I); 724 725 if (TodoStack.empty()) return 0; // No backedges to this block... 726 727 // Create a new loop to represent this basic block... 728 LoopT *L = new LoopT(BB); 729 BBMap[BB] = L; 730 731 BlockT *EntryBlock = BB->getParent()->begin(); 732 733 while (!TodoStack.empty()) { // Process all the nodes in the loop 734 BlockT *X = TodoStack.back(); 735 TodoStack.pop_back(); 736 737 if (!L->contains(X) && // As of yet unprocessed?? 738 DT.dominates(EntryBlock, X)) { // X is reachable from entry block? 739 // Check to see if this block already belongs to a loop. If this occurs 740 // then we have a case where a loop that is supposed to be a child of 741 // the current loop was processed before the current loop. When this 742 // occurs, this child loop gets added to a part of the current loop, 743 // making it a sibling to the current loop. We have to reparent this 744 // loop. 745 if (LoopT *SubLoop = 746 const_cast<LoopT *>(getLoopFor(X))) 747 if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){ 748 // Remove the subloop from it's current parent... 749 assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L); 750 LoopT *SLP = SubLoop->ParentLoop; // SubLoopParent 751 typename std::vector<LoopT *>::iterator I = 752 std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop); 753 assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?"); 754 SLP->SubLoops.erase(I); // Remove from parent... 755 756 // Add the subloop to THIS loop... 757 SubLoop->ParentLoop = L; 758 L->SubLoops.push_back(SubLoop); 759 } 760 761 // Normal case, add the block to our loop... 762 L->Blocks.push_back(X); 763 764 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 765 766 // Add all of the predecessors of X to the end of the work stack... 767 TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X), 768 InvBlockTraits::child_end(X)); 769 } 770 } 771 772 // If there are any loops nested within this loop, create them now! 773 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 774 E = L->Blocks.end(); I != E; ++I) 775 if (LoopT *NewLoop = ConsiderForLoop(*I, DT)) { 776 L->SubLoops.push_back(NewLoop); 777 NewLoop->ParentLoop = L; 778 } 779 780 // Add the basic blocks that comprise this loop to the BBMap so that this 781 // loop can be found for them. 782 // 783 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 784 E = L->Blocks.end(); I != E; ++I) { 785 typename std::map<BlockT*, LoopT *>::iterator BBMI = BBMap.find(*I); 786 if (BBMI == BBMap.end()) // Not in map yet... 787 BBMap.insert(BBMI, std::make_pair(*I, L)); // Must be at this level 788 } 789 790 // Now that we have a list of all of the child loops of this loop, check to 791 // see if any of them should actually be nested inside of each other. We 792 // can accidentally pull loops our of their parents, so we must make sure to 793 // organize the loop nests correctly now. 794 { 795 std::map<BlockT *, LoopT *> ContainingLoops; 796 for (unsigned i = 0; i != L->SubLoops.size(); ++i) { 797 LoopT *Child = L->SubLoops[i]; 798 assert(Child->getParentLoop() == L && "Not proper child loop?"); 799 800 if (LoopT *ContainingLoop = ContainingLoops[Child->getHeader()]) { 801 // If there is already a loop which contains this loop, move this loop 802 // into the containing loop. 803 MoveSiblingLoopInto(Child, ContainingLoop); 804 --i; // The loop got removed from the SubLoops list. 805 } else { 806 // This is currently considered to be a top-level loop. Check to see 807 // if any of the contained blocks are loop headers for subloops we 808 // have already processed. 809 for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) { 810 LoopT *&BlockLoop = ContainingLoops[Child->Blocks[b]]; 811 if (BlockLoop == 0) { // Child block not processed yet... 812 BlockLoop = Child; 813 } else if (BlockLoop != Child) { 814 LoopT *SubLoop = BlockLoop; 815 // Reparent all of the blocks which used to belong to BlockLoops 816 for (unsigned j = 0, e = SubLoop->Blocks.size(); j != e; ++j) 817 ContainingLoops[SubLoop->Blocks[j]] = Child; 818 819 // There is already a loop which contains this block, that means 820 // that we should reparent the loop which the block is currently 821 // considered to belong to to be a child of this loop. 822 MoveSiblingLoopInto(SubLoop, Child); 823 --i; // We just shrunk the SubLoops list. 824 } 825 } 826 } 827 } 828 } 829 830 return L; 831 } 832 833 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside 834 /// of the NewParent Loop, instead of being a sibling of it. 835 void MoveSiblingLoopInto(LoopT *NewChild, 836 LoopT *NewParent) { 837 LoopT *OldParent = NewChild->getParentLoop(); 838 assert(OldParent && OldParent == NewParent->getParentLoop() && 839 NewChild != NewParent && "Not sibling loops!"); 840 841 // Remove NewChild from being a child of OldParent 842 typename std::vector<LoopT *>::iterator I = 843 std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(), 844 NewChild); 845 assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??"); 846 OldParent->SubLoops.erase(I); // Remove from parent's subloops list 847 NewChild->ParentLoop = 0; 848 849 InsertLoopInto(NewChild, NewParent); 850 } 851 852 /// InsertLoopInto - This inserts loop L into the specified parent loop. If 853 /// the parent loop contains a loop which should contain L, the loop gets 854 /// inserted into L instead. 855 void InsertLoopInto(LoopT *L, LoopT *Parent) { 856 BlockT *LHeader = L->getHeader(); 857 assert(Parent->contains(LHeader) && 858 "This loop should not be inserted here!"); 859 860 // Check to see if it belongs in a child loop... 861 for (unsigned i = 0, e = static_cast<unsigned>(Parent->SubLoops.size()); 862 i != e; ++i) 863 if (Parent->SubLoops[i]->contains(LHeader)) { 864 InsertLoopInto(L, Parent->SubLoops[i]); 865 return; 866 } 867 868 // If not, insert it here! 869 Parent->SubLoops.push_back(L); 870 L->ParentLoop = Parent; 871 } 872 873 // Debugging 874 875 void print(raw_ostream &OS) const { 876 for (unsigned i = 0; i < TopLevelLoops.size(); ++i) 877 TopLevelLoops[i]->print(OS); 878 #if 0 879 for (std::map<BasicBlock*, LoopT*>::const_iterator I = BBMap.begin(), 880 E = BBMap.end(); I != E; ++I) 881 OS << "BB '" << I->first->getName() << "' level = " 882 << I->second->getLoopDepth() << "\n"; 883 #endif 884 } 885}; 886 887class LoopInfo : public FunctionPass { 888 LoopInfoBase<BasicBlock, Loop> LI; 889 friend class LoopBase<BasicBlock, Loop>; 890 891 void operator=(const LoopInfo &); // do not implement 892 LoopInfo(const LoopInfo &); // do not implement 893public: 894 static char ID; // Pass identification, replacement for typeid 895 896 LoopInfo() : FunctionPass(&ID) {} 897 898 LoopInfoBase<BasicBlock, Loop>& getBase() { return LI; } 899 900 /// iterator/begin/end - The interface to the top-level loops in the current 901 /// function. 902 /// 903 typedef LoopInfoBase<BasicBlock, Loop>::iterator iterator; 904 inline iterator begin() const { return LI.begin(); } 905 inline iterator end() const { return LI.end(); } 906 bool empty() const { return LI.empty(); } 907 908 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 909 /// block is in no loop (for example the entry node), null is returned. 910 /// 911 inline Loop *getLoopFor(const BasicBlock *BB) const { 912 return LI.getLoopFor(BB); 913 } 914 915 /// operator[] - same as getLoopFor... 916 /// 917 inline const Loop *operator[](const BasicBlock *BB) const { 918 return LI.getLoopFor(BB); 919 } 920 921 /// getLoopDepth - Return the loop nesting level of the specified block. A 922 /// depth of 0 means the block is not inside any loop. 923 /// 924 inline unsigned getLoopDepth(const BasicBlock *BB) const { 925 return LI.getLoopDepth(BB); 926 } 927 928 // isLoopHeader - True if the block is a loop header node 929 inline bool isLoopHeader(BasicBlock *BB) const { 930 return LI.isLoopHeader(BB); 931 } 932 933 /// runOnFunction - Calculate the natural loop information. 934 /// 935 virtual bool runOnFunction(Function &F); 936 937 virtual void releaseMemory() { LI.releaseMemory(); } 938 939 virtual void print(raw_ostream &O, const Module* M = 0) const; 940 941 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 942 943 /// removeLoop - This removes the specified top-level loop from this loop info 944 /// object. The loop is not deleted, as it will presumably be inserted into 945 /// another loop. 946 inline Loop *removeLoop(iterator I) { return LI.removeLoop(I); } 947 948 /// changeLoopFor - Change the top-level loop that contains BB to the 949 /// specified loop. This should be used by transformations that restructure 950 /// the loop hierarchy tree. 951 inline void changeLoopFor(BasicBlock *BB, Loop *L) { 952 LI.changeLoopFor(BB, L); 953 } 954 955 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 956 /// list with the indicated loop. 957 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) { 958 LI.changeTopLevelLoop(OldLoop, NewLoop); 959 } 960 961 /// addTopLevelLoop - This adds the specified loop to the collection of 962 /// top-level loops. 963 inline void addTopLevelLoop(Loop *New) { 964 LI.addTopLevelLoop(New); 965 } 966 967 /// removeBlock - This method completely removes BB from all data structures, 968 /// including all of the Loop objects it is nested in and our mapping from 969 /// BasicBlocks to loops. 970 void removeBlock(BasicBlock *BB) { 971 LI.removeBlock(BB); 972 } 973 974 static bool isNotAlreadyContainedIn(const Loop *SubLoop, 975 const Loop *ParentLoop) { 976 return 977 LoopInfoBase<BasicBlock, Loop>::isNotAlreadyContainedIn(SubLoop, 978 ParentLoop); 979 } 980}; 981 982 983// Allow clients to walk the list of nested loops... 984template <> struct GraphTraits<const Loop*> { 985 typedef const Loop NodeType; 986 typedef LoopInfo::iterator ChildIteratorType; 987 988 static NodeType *getEntryNode(const Loop *L) { return L; } 989 static inline ChildIteratorType child_begin(NodeType *N) { 990 return N->begin(); 991 } 992 static inline ChildIteratorType child_end(NodeType *N) { 993 return N->end(); 994 } 995}; 996 997template <> struct GraphTraits<Loop*> { 998 typedef Loop NodeType; 999 typedef LoopInfo::iterator ChildIteratorType; 1000 1001 static NodeType *getEntryNode(Loop *L) { return L; } 1002 static inline ChildIteratorType child_begin(NodeType *N) { 1003 return N->begin(); 1004 } 1005 static inline ChildIteratorType child_end(NodeType *N) { 1006 return N->end(); 1007 } 1008}; 1009 1010template<class BlockT, class LoopT> 1011void 1012LoopBase<BlockT, LoopT>::addBasicBlockToLoop(BlockT *NewBB, 1013 LoopInfoBase<BlockT, LoopT> &LIB) { 1014 assert((Blocks.empty() || LIB[getHeader()] == this) && 1015 "Incorrect LI specified for this loop!"); 1016 assert(NewBB && "Cannot add a null basic block to the loop!"); 1017 assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!"); 1018 1019 LoopT *L = static_cast<LoopT *>(this); 1020 1021 // Add the loop mapping to the LoopInfo object... 1022 LIB.BBMap[NewBB] = L; 1023 1024 // Add the basic block to this loop and all parent loops... 1025 while (L) { 1026 L->Blocks.push_back(NewBB); 1027 L = L->getParentLoop(); 1028 } 1029} 1030 1031} // End llvm namespace 1032 1033#endif 1034