LoopInfo.h revision 206613b289f60b71a76e9190d36b9ea9e47a701e
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 /// getUniqueExitBlocks - Return all unique successor blocks of this loop. 217 /// These are the blocks _outside of the current loop_ which are branched to. 218 /// This assumes that loop is in canonical form. 219 /// 220 void getUniqueExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const { 221 // Sort the blocks vector so that we can use binary search to do quick 222 // lookups. 223 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 224 std::sort(LoopBBs.begin(), LoopBBs.end()); 225 226 std::vector<BlockT*> switchExitBlocks; 227 228 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) { 229 230 BlockT *current = *BI; 231 switchExitBlocks.clear(); 232 233 typedef GraphTraits<BlockT*> BlockTraits; 234 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 235 for (typename BlockTraits::ChildIteratorType I = 236 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 237 I != E; ++I) { 238 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) 239 // If block is inside the loop then it is not a exit block. 240 continue; 241 242 typename InvBlockTraits::ChildIteratorType PI = 243 InvBlockTraits::child_begin(*I); 244 BlockT *firstPred = *PI; 245 246 // If current basic block is this exit block's first predecessor 247 // then only insert exit block in to the output ExitBlocks vector. 248 // This ensures that same exit block is not inserted twice into 249 // ExitBlocks vector. 250 if (current != firstPred) 251 continue; 252 253 // If a terminator has more then two successors, for example SwitchInst, 254 // then it is possible that there are multiple edges from current block 255 // to one exit block. 256 if (std::distance(BlockTraits::child_begin(current), 257 BlockTraits::child_end(current)) <= 2) { 258 ExitBlocks.push_back(*I); 259 continue; 260 } 261 262 // In case of multiple edges from current block to exit block, collect 263 // only one edge in ExitBlocks. Use switchExitBlocks to keep track of 264 // duplicate edges. 265 if (std::find(switchExitBlocks.begin(), switchExitBlocks.end(), *I) 266 == switchExitBlocks.end()) { 267 switchExitBlocks.push_back(*I); 268 ExitBlocks.push_back(*I); 269 } 270 } 271 } 272 } 273 274 /// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one 275 /// block, return that block. Otherwise return null. 276 BlockT *getUniqueExitBlock() const { 277 SmallVector<BlockT*, 8> UniqueExitBlocks; 278 getUniqueExitBlocks(UniqueExitBlocks); 279 if (UniqueExitBlocks.size() == 1) 280 return UniqueExitBlocks[0]; 281 return 0; 282 } 283 284 /// getLoopPreheader - If there is a preheader for this loop, return it. A 285 /// loop has a preheader if there is only one edge to the header of the loop 286 /// from outside of the loop. If this is the case, the block branching to the 287 /// header of the loop is the preheader node. 288 /// 289 /// This method returns null if there is no preheader for the loop. 290 /// 291 BlockT *getLoopPreheader() const { 292 // Keep track of nodes outside the loop branching to the header... 293 BlockT *Out = 0; 294 295 // Loop over the predecessors of the header node... 296 BlockT *Header = getHeader(); 297 typedef GraphTraits<BlockT*> BlockTraits; 298 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 299 for (typename InvBlockTraits::ChildIteratorType PI = 300 InvBlockTraits::child_begin(Header), 301 PE = InvBlockTraits::child_end(Header); PI != PE; ++PI) 302 if (!contains(*PI)) { // If the block is not in the loop... 303 if (Out && Out != *PI) 304 return 0; // Multiple predecessors outside the loop 305 Out = *PI; 306 } 307 308 // Make sure there is only one exit out of the preheader. 309 assert(Out && "Header of loop has no predecessors from outside loop?"); 310 typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out); 311 ++SI; 312 if (SI != BlockTraits::child_end(Out)) 313 return 0; // Multiple exits from the block, must not be a preheader. 314 315 // If there is exactly one preheader, return it. If there was zero, then 316 // Out is still null. 317 return Out; 318 } 319 320 /// getLoopLatch - If there is a single latch block for this loop, return it. 321 /// A latch block is a block that contains a branch back to the header. 322 /// A loop header in normal form has two edges into it: one from a preheader 323 /// and one from a latch block. 324 BlockT *getLoopLatch() const { 325 BlockT *Header = getHeader(); 326 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 327 typename InvBlockTraits::ChildIteratorType PI = 328 InvBlockTraits::child_begin(Header); 329 typename InvBlockTraits::ChildIteratorType PE = 330 InvBlockTraits::child_end(Header); 331 if (PI == PE) return 0; // no preds? 332 333 BlockT *Latch = 0; 334 if (contains(*PI)) 335 Latch = *PI; 336 ++PI; 337 if (PI == PE) return 0; // only one pred? 338 339 if (contains(*PI)) { 340 if (Latch) return 0; // multiple backedges 341 Latch = *PI; 342 } 343 ++PI; 344 if (PI != PE) return 0; // more than two preds 345 346 return Latch; 347 } 348 349 //===--------------------------------------------------------------------===// 350 // APIs for updating loop information after changing the CFG 351 // 352 353 /// addBasicBlockToLoop - This method is used by other analyses to update loop 354 /// information. NewBB is set to be a new member of the current loop. 355 /// Because of this, it is added as a member of all parent loops, and is added 356 /// to the specified LoopInfo object as being in the current basic block. It 357 /// is not valid to replace the loop header with this method. 358 /// 359 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LI); 360 361 /// replaceChildLoopWith - This is used when splitting loops up. It replaces 362 /// the OldChild entry in our children list with NewChild, and updates the 363 /// parent pointer of OldChild to be null and the NewChild to be this loop. 364 /// This updates the loop depth of the new child. 365 void replaceChildLoopWith(LoopT *OldChild, 366 LoopT *NewChild) { 367 assert(OldChild->ParentLoop == this && "This loop is already broken!"); 368 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 369 typename std::vector<LoopT *>::iterator I = 370 std::find(SubLoops.begin(), SubLoops.end(), OldChild); 371 assert(I != SubLoops.end() && "OldChild not in loop!"); 372 *I = NewChild; 373 OldChild->ParentLoop = 0; 374 NewChild->ParentLoop = static_cast<LoopT *>(this); 375 } 376 377 /// addChildLoop - Add the specified loop to be a child of this loop. This 378 /// updates the loop depth of the new child. 379 /// 380 void addChildLoop(LoopT *NewChild) { 381 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 382 NewChild->ParentLoop = static_cast<LoopT *>(this); 383 SubLoops.push_back(NewChild); 384 } 385 386 /// removeChildLoop - This removes the specified child from being a subloop of 387 /// this loop. The loop is not deleted, as it will presumably be inserted 388 /// into another loop. 389 LoopT *removeChildLoop(iterator I) { 390 assert(I != SubLoops.end() && "Cannot remove end iterator!"); 391 LoopT *Child = *I; 392 assert(Child->ParentLoop == this && "Child is not a child of this loop!"); 393 SubLoops.erase(SubLoops.begin()+(I-begin())); 394 Child->ParentLoop = 0; 395 return Child; 396 } 397 398 /// addBlockEntry - This adds a basic block directly to the basic block list. 399 /// This should only be used by transformations that create new loops. Other 400 /// transformations should use addBasicBlockToLoop. 401 void addBlockEntry(BlockT *BB) { 402 Blocks.push_back(BB); 403 } 404 405 /// moveToHeader - This method is used to move BB (which must be part of this 406 /// loop) to be the loop header of the loop (the block that dominates all 407 /// others). 408 void moveToHeader(BlockT *BB) { 409 if (Blocks[0] == BB) return; 410 for (unsigned i = 0; ; ++i) { 411 assert(i != Blocks.size() && "Loop does not contain BB!"); 412 if (Blocks[i] == BB) { 413 Blocks[i] = Blocks[0]; 414 Blocks[0] = BB; 415 return; 416 } 417 } 418 } 419 420 /// removeBlockFromLoop - This removes the specified basic block from the 421 /// current loop, updating the Blocks as appropriate. This does not update 422 /// the mapping in the LoopInfo class. 423 void removeBlockFromLoop(BlockT *BB) { 424 RemoveFromVector(Blocks, BB); 425 } 426 427 /// verifyLoop - Verify loop structure 428 void verifyLoop() const { 429#ifndef NDEBUG 430 assert (getHeader() && "Loop header is missing"); 431 assert (getLoopPreheader() && "Loop preheader is missing"); 432 assert (getLoopLatch() && "Loop latch is missing"); 433 for (iterator I = SubLoops.begin(), E = SubLoops.end(); I != E; ++I) 434 (*I)->verifyLoop(); 435#endif 436 } 437 438 void print(std::ostream &OS, unsigned Depth = 0) const { 439 OS << std::string(Depth*2, ' ') << "Loop at depth " << getLoopDepth() 440 << " containing: "; 441 442 for (unsigned i = 0; i < getBlocks().size(); ++i) { 443 if (i) OS << ","; 444 BlockT *BB = getBlocks()[i]; 445 WriteAsOperand(OS, BB, false); 446 if (BB == getHeader()) OS << "<header>"; 447 if (BB == getLoopLatch()) OS << "<latch>"; 448 if (isLoopExit(BB)) OS << "<exit>"; 449 } 450 OS << "\n"; 451 452 for (iterator I = begin(), E = end(); I != E; ++I) 453 (*I)->print(OS, Depth+2); 454 } 455 456 void print(std::ostream *O, unsigned Depth = 0) const { 457 if (O) print(*O, Depth); 458 } 459 460 void dump() const { 461 print(cerr); 462 } 463 464protected: 465 friend class LoopInfoBase<BlockT, LoopT>; 466 explicit LoopBase(BlockT *BB) : ParentLoop(0) { 467 Blocks.push_back(BB); 468 } 469}; 470 471class Loop : public LoopBase<BasicBlock, Loop> { 472public: 473 Loop() {} 474 475 /// isLoopInvariant - Return true if the specified value is loop invariant 476 /// 477 bool isLoopInvariant(Value *V) const; 478 479 /// isLoopInvariant - Return true if the specified instruction is 480 /// loop-invariant. 481 /// 482 bool isLoopInvariant(Instruction *I) const; 483 484 /// makeLoopInvariant - If the given value is an instruction inside of the 485 /// loop and it can be hoisted, do so to make it trivially loop-invariant. 486 /// Return true if the value after any hoisting is loop invariant. This 487 /// function can be used as a slightly more aggressive replacement for 488 /// isLoopInvariant. 489 /// 490 /// If InsertPt is specified, it is the point to hoist instructions to. 491 /// If null, the terminator of the loop preheader is used. 492 /// 493 bool makeLoopInvariant(Value *V, bool &Changed, 494 Instruction *InsertPt = 0) const; 495 496 /// makeLoopInvariant - If the given instruction is inside of the 497 /// loop and it can be hoisted, do so to make it trivially loop-invariant. 498 /// Return true if the instruction after any hoisting is loop invariant. This 499 /// function can be used as a slightly more aggressive replacement for 500 /// isLoopInvariant. 501 /// 502 /// If InsertPt is specified, it is the point to hoist instructions to. 503 /// If null, the terminator of the loop preheader is used. 504 /// 505 bool makeLoopInvariant(Instruction *I, bool &Changed, 506 Instruction *InsertPt = 0) const; 507 508 /// getCanonicalInductionVariable - Check to see if the loop has a canonical 509 /// induction variable: an integer recurrence that starts at 0 and increments 510 /// by one each time through the loop. If so, return the phi node that 511 /// corresponds to it. 512 /// 513 /// The IndVarSimplify pass transforms loops to have a canonical induction 514 /// variable. 515 /// 516 PHINode *getCanonicalInductionVariable() const; 517 518 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds 519 /// the canonical induction variable value for the "next" iteration of the 520 /// loop. This always succeeds if getCanonicalInductionVariable succeeds. 521 /// 522 Instruction *getCanonicalInductionVariableIncrement() const; 523 524 /// getTripCount - Return a loop-invariant LLVM value indicating the number of 525 /// times the loop will be executed. Note that this means that the backedge 526 /// of the loop executes N-1 times. If the trip-count cannot be determined, 527 /// this returns null. 528 /// 529 /// The IndVarSimplify pass transforms loops to have a form that this 530 /// function easily understands. 531 /// 532 Value *getTripCount() const; 533 534 /// getSmallConstantTripCount - Returns the trip count of this loop as a 535 /// normal unsigned value, if possible. Returns 0 if the trip count is unknown 536 /// of not constant. Will also return 0 if the trip count is very large 537 /// (>= 2^32) 538 unsigned getSmallConstantTripCount() const; 539 540 /// getSmallConstantTripMultiple - Returns the largest constant divisor of the 541 /// trip count of this loop as a normal unsigned value, if possible. This 542 /// means that the actual trip count is always a multiple of the returned 543 /// value (don't forget the trip count could very well be zero as well!). 544 /// 545 /// Returns 1 if the trip count is unknown or not guaranteed to be the 546 /// multiple of a constant (which is also the case if the trip count is simply 547 /// constant, use getSmallConstantTripCount for that case), Will also return 1 548 /// if the trip count is very large (>= 2^32). 549 unsigned getSmallConstantTripMultiple() const; 550 551 /// isLCSSAForm - Return true if the Loop is in LCSSA form 552 bool isLCSSAForm() const; 553 554private: 555 friend class LoopInfoBase<BasicBlock, Loop>; 556 explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {} 557}; 558 559//===----------------------------------------------------------------------===// 560/// LoopInfo - This class builds and contains all of the top level loop 561/// structures in the specified function. 562/// 563 564template<class BlockT, class LoopT> 565class LoopInfoBase { 566 // BBMap - Mapping of basic blocks to the inner most loop they occur in 567 std::map<BlockT *, LoopT *> BBMap; 568 std::vector<LoopT *> TopLevelLoops; 569 friend class LoopBase<BlockT, LoopT>; 570 571 void operator=(const LoopInfoBase &); // do not implement 572 LoopInfoBase(const LoopInfo &); // do not implement 573public: 574 LoopInfoBase() { } 575 ~LoopInfoBase() { releaseMemory(); } 576 577 void releaseMemory() { 578 for (typename std::vector<LoopT *>::iterator I = 579 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I) 580 delete *I; // Delete all of the loops... 581 582 BBMap.clear(); // Reset internal state of analysis 583 TopLevelLoops.clear(); 584 } 585 586 /// iterator/begin/end - The interface to the top-level loops in the current 587 /// function. 588 /// 589 typedef typename std::vector<LoopT *>::const_iterator iterator; 590 iterator begin() const { return TopLevelLoops.begin(); } 591 iterator end() const { return TopLevelLoops.end(); } 592 bool empty() const { return TopLevelLoops.empty(); } 593 594 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 595 /// block is in no loop (for example the entry node), null is returned. 596 /// 597 LoopT *getLoopFor(const BlockT *BB) const { 598 typename std::map<BlockT *, LoopT *>::const_iterator I= 599 BBMap.find(const_cast<BlockT*>(BB)); 600 return I != BBMap.end() ? I->second : 0; 601 } 602 603 /// operator[] - same as getLoopFor... 604 /// 605 const LoopT *operator[](const BlockT *BB) const { 606 return getLoopFor(BB); 607 } 608 609 /// getLoopDepth - Return the loop nesting level of the specified block. A 610 /// depth of 0 means the block is not inside any loop. 611 /// 612 unsigned getLoopDepth(const BlockT *BB) const { 613 const LoopT *L = getLoopFor(BB); 614 return L ? L->getLoopDepth() : 0; 615 } 616 617 // isLoopHeader - True if the block is a loop header node 618 bool isLoopHeader(BlockT *BB) const { 619 const LoopT *L = getLoopFor(BB); 620 return L && L->getHeader() == BB; 621 } 622 623 /// removeLoop - This removes the specified top-level loop from this loop info 624 /// object. The loop is not deleted, as it will presumably be inserted into 625 /// another loop. 626 LoopT *removeLoop(iterator I) { 627 assert(I != end() && "Cannot remove end iterator!"); 628 LoopT *L = *I; 629 assert(L->getParentLoop() == 0 && "Not a top-level loop!"); 630 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin())); 631 return L; 632 } 633 634 /// changeLoopFor - Change the top-level loop that contains BB to the 635 /// specified loop. This should be used by transformations that restructure 636 /// the loop hierarchy tree. 637 void changeLoopFor(BlockT *BB, LoopT *L) { 638 LoopT *&OldLoop = BBMap[BB]; 639 assert(OldLoop && "Block not in a loop yet!"); 640 OldLoop = L; 641 } 642 643 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 644 /// list with the indicated loop. 645 void changeTopLevelLoop(LoopT *OldLoop, 646 LoopT *NewLoop) { 647 typename std::vector<LoopT *>::iterator I = 648 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop); 649 assert(I != TopLevelLoops.end() && "Old loop not at top level!"); 650 *I = NewLoop; 651 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 && 652 "Loops already embedded into a subloop!"); 653 } 654 655 /// addTopLevelLoop - This adds the specified loop to the collection of 656 /// top-level loops. 657 void addTopLevelLoop(LoopT *New) { 658 assert(New->getParentLoop() == 0 && "Loop already in subloop!"); 659 TopLevelLoops.push_back(New); 660 } 661 662 /// removeBlock - This method completely removes BB from all data structures, 663 /// including all of the Loop objects it is nested in and our mapping from 664 /// BasicBlocks to loops. 665 void removeBlock(BlockT *BB) { 666 typename std::map<BlockT *, LoopT *>::iterator I = BBMap.find(BB); 667 if (I != BBMap.end()) { 668 for (LoopT *L = I->second; L; L = L->getParentLoop()) 669 L->removeBlockFromLoop(BB); 670 671 BBMap.erase(I); 672 } 673 } 674 675 // Internals 676 677 static bool isNotAlreadyContainedIn(const LoopT *SubLoop, 678 const LoopT *ParentLoop) { 679 if (SubLoop == 0) return true; 680 if (SubLoop == ParentLoop) return false; 681 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop); 682 } 683 684 void Calculate(DominatorTreeBase<BlockT> &DT) { 685 BlockT *RootNode = DT.getRootNode()->getBlock(); 686 687 for (df_iterator<BlockT*> NI = df_begin(RootNode), 688 NE = df_end(RootNode); NI != NE; ++NI) 689 if (LoopT *L = ConsiderForLoop(*NI, DT)) 690 TopLevelLoops.push_back(L); 691 } 692 693 LoopT *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) { 694 if (BBMap.find(BB) != BBMap.end()) return 0;// Haven't processed this node? 695 696 std::vector<BlockT *> TodoStack; 697 698 // Scan the predecessors of BB, checking to see if BB dominates any of 699 // them. This identifies backedges which target this node... 700 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 701 for (typename InvBlockTraits::ChildIteratorType I = 702 InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB); 703 I != E; ++I) 704 if (DT.dominates(BB, *I)) // If BB dominates it's predecessor... 705 TodoStack.push_back(*I); 706 707 if (TodoStack.empty()) return 0; // No backedges to this block... 708 709 // Create a new loop to represent this basic block... 710 LoopT *L = new LoopT(BB); 711 BBMap[BB] = L; 712 713 BlockT *EntryBlock = BB->getParent()->begin(); 714 715 while (!TodoStack.empty()) { // Process all the nodes in the loop 716 BlockT *X = TodoStack.back(); 717 TodoStack.pop_back(); 718 719 if (!L->contains(X) && // As of yet unprocessed?? 720 DT.dominates(EntryBlock, X)) { // X is reachable from entry block? 721 // Check to see if this block already belongs to a loop. If this occurs 722 // then we have a case where a loop that is supposed to be a child of 723 // the current loop was processed before the current loop. When this 724 // occurs, this child loop gets added to a part of the current loop, 725 // making it a sibling to the current loop. We have to reparent this 726 // loop. 727 if (LoopT *SubLoop = 728 const_cast<LoopT *>(getLoopFor(X))) 729 if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){ 730 // Remove the subloop from it's current parent... 731 assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L); 732 LoopT *SLP = SubLoop->ParentLoop; // SubLoopParent 733 typename std::vector<LoopT *>::iterator I = 734 std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop); 735 assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?"); 736 SLP->SubLoops.erase(I); // Remove from parent... 737 738 // Add the subloop to THIS loop... 739 SubLoop->ParentLoop = L; 740 L->SubLoops.push_back(SubLoop); 741 } 742 743 // Normal case, add the block to our loop... 744 L->Blocks.push_back(X); 745 746 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 747 748 // Add all of the predecessors of X to the end of the work stack... 749 TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X), 750 InvBlockTraits::child_end(X)); 751 } 752 } 753 754 // If there are any loops nested within this loop, create them now! 755 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 756 E = L->Blocks.end(); I != E; ++I) 757 if (LoopT *NewLoop = ConsiderForLoop(*I, DT)) { 758 L->SubLoops.push_back(NewLoop); 759 NewLoop->ParentLoop = L; 760 } 761 762 // Add the basic blocks that comprise this loop to the BBMap so that this 763 // loop can be found for them. 764 // 765 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 766 E = L->Blocks.end(); I != E; ++I) { 767 typename std::map<BlockT*, LoopT *>::iterator BBMI = BBMap.find(*I); 768 if (BBMI == BBMap.end()) // Not in map yet... 769 BBMap.insert(BBMI, std::make_pair(*I, L)); // Must be at this level 770 } 771 772 // Now that we have a list of all of the child loops of this loop, check to 773 // see if any of them should actually be nested inside of each other. We 774 // can accidentally pull loops our of their parents, so we must make sure to 775 // organize the loop nests correctly now. 776 { 777 std::map<BlockT *, LoopT *> ContainingLoops; 778 for (unsigned i = 0; i != L->SubLoops.size(); ++i) { 779 LoopT *Child = L->SubLoops[i]; 780 assert(Child->getParentLoop() == L && "Not proper child loop?"); 781 782 if (LoopT *ContainingLoop = ContainingLoops[Child->getHeader()]) { 783 // If there is already a loop which contains this loop, move this loop 784 // into the containing loop. 785 MoveSiblingLoopInto(Child, ContainingLoop); 786 --i; // The loop got removed from the SubLoops list. 787 } else { 788 // This is currently considered to be a top-level loop. Check to see 789 // if any of the contained blocks are loop headers for subloops we 790 // have already processed. 791 for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) { 792 LoopT *&BlockLoop = ContainingLoops[Child->Blocks[b]]; 793 if (BlockLoop == 0) { // Child block not processed yet... 794 BlockLoop = Child; 795 } else if (BlockLoop != Child) { 796 LoopT *SubLoop = BlockLoop; 797 // Reparent all of the blocks which used to belong to BlockLoops 798 for (unsigned j = 0, e = SubLoop->Blocks.size(); j != e; ++j) 799 ContainingLoops[SubLoop->Blocks[j]] = Child; 800 801 // There is already a loop which contains this block, that means 802 // that we should reparent the loop which the block is currently 803 // considered to belong to to be a child of this loop. 804 MoveSiblingLoopInto(SubLoop, Child); 805 --i; // We just shrunk the SubLoops list. 806 } 807 } 808 } 809 } 810 } 811 812 return L; 813 } 814 815 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside 816 /// of the NewParent Loop, instead of being a sibling of it. 817 void MoveSiblingLoopInto(LoopT *NewChild, 818 LoopT *NewParent) { 819 LoopT *OldParent = NewChild->getParentLoop(); 820 assert(OldParent && OldParent == NewParent->getParentLoop() && 821 NewChild != NewParent && "Not sibling loops!"); 822 823 // Remove NewChild from being a child of OldParent 824 typename std::vector<LoopT *>::iterator I = 825 std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(), 826 NewChild); 827 assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??"); 828 OldParent->SubLoops.erase(I); // Remove from parent's subloops list 829 NewChild->ParentLoop = 0; 830 831 InsertLoopInto(NewChild, NewParent); 832 } 833 834 /// InsertLoopInto - This inserts loop L into the specified parent loop. If 835 /// the parent loop contains a loop which should contain L, the loop gets 836 /// inserted into L instead. 837 void InsertLoopInto(LoopT *L, LoopT *Parent) { 838 BlockT *LHeader = L->getHeader(); 839 assert(Parent->contains(LHeader) && 840 "This loop should not be inserted here!"); 841 842 // Check to see if it belongs in a child loop... 843 for (unsigned i = 0, e = static_cast<unsigned>(Parent->SubLoops.size()); 844 i != e; ++i) 845 if (Parent->SubLoops[i]->contains(LHeader)) { 846 InsertLoopInto(L, Parent->SubLoops[i]); 847 return; 848 } 849 850 // If not, insert it here! 851 Parent->SubLoops.push_back(L); 852 L->ParentLoop = Parent; 853 } 854 855 // Debugging 856 857 void print(std::ostream &OS, const Module* ) const { 858 for (unsigned i = 0; i < TopLevelLoops.size(); ++i) 859 TopLevelLoops[i]->print(OS); 860 #if 0 861 for (std::map<BasicBlock*, LoopT*>::const_iterator I = BBMap.begin(), 862 E = BBMap.end(); I != E; ++I) 863 OS << "BB '" << I->first->getName() << "' level = " 864 << I->second->getLoopDepth() << "\n"; 865 #endif 866 } 867}; 868 869class LoopInfo : public FunctionPass { 870 LoopInfoBase<BasicBlock, Loop> LI; 871 friend class LoopBase<BasicBlock, Loop>; 872 873 void operator=(const LoopInfo &); // do not implement 874 LoopInfo(const LoopInfo &); // do not implement 875public: 876 static char ID; // Pass identification, replacement for typeid 877 878 LoopInfo() : FunctionPass(&ID) {} 879 880 LoopInfoBase<BasicBlock, Loop>& getBase() { return LI; } 881 882 /// iterator/begin/end - The interface to the top-level loops in the current 883 /// function. 884 /// 885 typedef LoopInfoBase<BasicBlock, Loop>::iterator iterator; 886 inline iterator begin() const { return LI.begin(); } 887 inline iterator end() const { return LI.end(); } 888 bool empty() const { return LI.empty(); } 889 890 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 891 /// block is in no loop (for example the entry node), null is returned. 892 /// 893 inline Loop *getLoopFor(const BasicBlock *BB) const { 894 return LI.getLoopFor(BB); 895 } 896 897 /// operator[] - same as getLoopFor... 898 /// 899 inline const Loop *operator[](const BasicBlock *BB) const { 900 return LI.getLoopFor(BB); 901 } 902 903 /// getLoopDepth - Return the loop nesting level of the specified block. A 904 /// depth of 0 means the block is not inside any loop. 905 /// 906 inline unsigned getLoopDepth(const BasicBlock *BB) const { 907 return LI.getLoopDepth(BB); 908 } 909 910 // isLoopHeader - True if the block is a loop header node 911 inline bool isLoopHeader(BasicBlock *BB) const { 912 return LI.isLoopHeader(BB); 913 } 914 915 /// runOnFunction - Calculate the natural loop information. 916 /// 917 virtual bool runOnFunction(Function &F); 918 919 virtual void releaseMemory() { LI.releaseMemory(); } 920 921 virtual void print(std::ostream &O, const Module* M = 0) const { 922 LI.print(O, M); 923 } 924 925 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 926 927 /// removeLoop - This removes the specified top-level loop from this loop info 928 /// object. The loop is not deleted, as it will presumably be inserted into 929 /// another loop. 930 inline Loop *removeLoop(iterator I) { return LI.removeLoop(I); } 931 932 /// changeLoopFor - Change the top-level loop that contains BB to the 933 /// specified loop. This should be used by transformations that restructure 934 /// the loop hierarchy tree. 935 inline void changeLoopFor(BasicBlock *BB, Loop *L) { 936 LI.changeLoopFor(BB, L); 937 } 938 939 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 940 /// list with the indicated loop. 941 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) { 942 LI.changeTopLevelLoop(OldLoop, NewLoop); 943 } 944 945 /// addTopLevelLoop - This adds the specified loop to the collection of 946 /// top-level loops. 947 inline void addTopLevelLoop(Loop *New) { 948 LI.addTopLevelLoop(New); 949 } 950 951 /// removeBlock - This method completely removes BB from all data structures, 952 /// including all of the Loop objects it is nested in and our mapping from 953 /// BasicBlocks to loops. 954 void removeBlock(BasicBlock *BB) { 955 LI.removeBlock(BB); 956 } 957 958 static bool isNotAlreadyContainedIn(const Loop *SubLoop, 959 const Loop *ParentLoop) { 960 return 961 LoopInfoBase<BasicBlock, Loop>::isNotAlreadyContainedIn(SubLoop, 962 ParentLoop); 963 } 964}; 965 966 967// Allow clients to walk the list of nested loops... 968template <> struct GraphTraits<const Loop*> { 969 typedef const Loop NodeType; 970 typedef LoopInfo::iterator ChildIteratorType; 971 972 static NodeType *getEntryNode(const Loop *L) { return L; } 973 static inline ChildIteratorType child_begin(NodeType *N) { 974 return N->begin(); 975 } 976 static inline ChildIteratorType child_end(NodeType *N) { 977 return N->end(); 978 } 979}; 980 981template <> struct GraphTraits<Loop*> { 982 typedef Loop NodeType; 983 typedef LoopInfo::iterator ChildIteratorType; 984 985 static NodeType *getEntryNode(Loop *L) { return L; } 986 static inline ChildIteratorType child_begin(NodeType *N) { 987 return N->begin(); 988 } 989 static inline ChildIteratorType child_end(NodeType *N) { 990 return N->end(); 991 } 992}; 993 994template<class BlockT, class LoopT> 995void 996LoopBase<BlockT, LoopT>::addBasicBlockToLoop(BlockT *NewBB, 997 LoopInfoBase<BlockT, LoopT> &LIB) { 998 assert((Blocks.empty() || LIB[getHeader()] == this) && 999 "Incorrect LI specified for this loop!"); 1000 assert(NewBB && "Cannot add a null basic block to the loop!"); 1001 assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!"); 1002 1003 LoopT *L = static_cast<LoopT *>(this); 1004 1005 // Add the loop mapping to the LoopInfo object... 1006 LIB.BBMap[NewBB] = L; 1007 1008 // Add the basic block to this loop and all parent loops... 1009 while (L) { 1010 L->Blocks.push_back(NewBB); 1011 L = L->getParentLoop(); 1012 } 1013} 1014 1015} // End llvm namespace 1016 1017#endif 1018