LoopInfo.h revision a342026504e65e2c8dc5600dab4b45ab4f94026d
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 instruciton 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, Instruction *InsertPt = 0) const; 494 495 /// makeLoopInvariant - If the given instruction is inside of the 496 /// loop and it can be hoisted, do so to make it trivially loop-invariant. 497 /// Return true if the instruction after any hoisting is loop invariant. This 498 /// function can be used as a slightly more aggressive replacement for 499 /// isLoopInvariant. 500 /// 501 /// If InsertPt is specified, it is the point to hoist instructions to. 502 /// If null, the terminator of the loop preheader is used. 503 /// 504 bool makeLoopInvariant(Instruction *I, Instruction *InsertPt = 0) const; 505 506 /// getCanonicalInductionVariable - Check to see if the loop has a canonical 507 /// induction variable: an integer recurrence that starts at 0 and increments 508 /// by one each time through the loop. If so, return the phi node that 509 /// corresponds to it. 510 /// 511 /// The IndVarSimplify pass transforms loops to have a canonical induction 512 /// variable. 513 /// 514 PHINode *getCanonicalInductionVariable() const; 515 516 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds 517 /// the canonical induction variable value for the "next" iteration of the 518 /// loop. This always succeeds if getCanonicalInductionVariable succeeds. 519 /// 520 Instruction *getCanonicalInductionVariableIncrement() const; 521 522 /// getTripCount - Return a loop-invariant LLVM value indicating the number of 523 /// times the loop will be executed. Note that this means that the backedge 524 /// of the loop executes N-1 times. If the trip-count cannot be determined, 525 /// this returns null. 526 /// 527 /// The IndVarSimplify pass transforms loops to have a form that this 528 /// function easily understands. 529 /// 530 Value *getTripCount() const; 531 532 /// getSmallConstantTripCount - Returns the trip count of this loop as a 533 /// normal unsigned value, if possible. Returns 0 if the trip count is unknown 534 /// of not constant. Will also return 0 if the trip count is very large 535 /// (>= 2^32) 536 unsigned getSmallConstantTripCount() const; 537 538 /// getSmallConstantTripMultiple - Returns the largest constant divisor of the 539 /// trip count of this loop as a normal unsigned value, if possible. This 540 /// means that the actual trip count is always a multiple of the returned 541 /// value (don't forget the trip count could very well be zero as well!). 542 /// 543 /// Returns 1 if the trip count is unknown or not guaranteed to be the 544 /// multiple of a constant (which is also the case if the trip count is simply 545 /// constant, use getSmallConstantTripCount for that case), Will also return 1 546 /// if the trip count is very large (>= 2^32). 547 unsigned getSmallConstantTripMultiple() const; 548 549 /// isLCSSAForm - Return true if the Loop is in LCSSA form 550 bool isLCSSAForm() const; 551 552private: 553 friend class LoopInfoBase<BasicBlock, Loop>; 554 explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {} 555}; 556 557//===----------------------------------------------------------------------===// 558/// LoopInfo - This class builds and contains all of the top level loop 559/// structures in the specified function. 560/// 561 562template<class BlockT, class LoopT> 563class LoopInfoBase { 564 // BBMap - Mapping of basic blocks to the inner most loop they occur in 565 std::map<BlockT *, LoopT *> BBMap; 566 std::vector<LoopT *> TopLevelLoops; 567 friend class LoopBase<BlockT, LoopT>; 568 569 void operator=(const LoopInfoBase &); // do not implement 570 LoopInfoBase(const LoopInfo &); // do not implement 571public: 572 LoopInfoBase() { } 573 ~LoopInfoBase() { releaseMemory(); } 574 575 void releaseMemory() { 576 for (typename std::vector<LoopT *>::iterator I = 577 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I) 578 delete *I; // Delete all of the loops... 579 580 BBMap.clear(); // Reset internal state of analysis 581 TopLevelLoops.clear(); 582 } 583 584 /// iterator/begin/end - The interface to the top-level loops in the current 585 /// function. 586 /// 587 typedef typename std::vector<LoopT *>::const_iterator iterator; 588 iterator begin() const { return TopLevelLoops.begin(); } 589 iterator end() const { return TopLevelLoops.end(); } 590 bool empty() const { return TopLevelLoops.empty(); } 591 592 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 593 /// block is in no loop (for example the entry node), null is returned. 594 /// 595 LoopT *getLoopFor(const BlockT *BB) const { 596 typename std::map<BlockT *, LoopT *>::const_iterator I= 597 BBMap.find(const_cast<BlockT*>(BB)); 598 return I != BBMap.end() ? I->second : 0; 599 } 600 601 /// operator[] - same as getLoopFor... 602 /// 603 const LoopT *operator[](const BlockT *BB) const { 604 return getLoopFor(BB); 605 } 606 607 /// getLoopDepth - Return the loop nesting level of the specified block. A 608 /// depth of 0 means the block is not inside any loop. 609 /// 610 unsigned getLoopDepth(const BlockT *BB) const { 611 const LoopT *L = getLoopFor(BB); 612 return L ? L->getLoopDepth() : 0; 613 } 614 615 // isLoopHeader - True if the block is a loop header node 616 bool isLoopHeader(BlockT *BB) const { 617 const LoopT *L = getLoopFor(BB); 618 return L && L->getHeader() == BB; 619 } 620 621 /// removeLoop - This removes the specified top-level loop from this loop info 622 /// object. The loop is not deleted, as it will presumably be inserted into 623 /// another loop. 624 LoopT *removeLoop(iterator I) { 625 assert(I != end() && "Cannot remove end iterator!"); 626 LoopT *L = *I; 627 assert(L->getParentLoop() == 0 && "Not a top-level loop!"); 628 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin())); 629 return L; 630 } 631 632 /// changeLoopFor - Change the top-level loop that contains BB to the 633 /// specified loop. This should be used by transformations that restructure 634 /// the loop hierarchy tree. 635 void changeLoopFor(BlockT *BB, LoopT *L) { 636 LoopT *&OldLoop = BBMap[BB]; 637 assert(OldLoop && "Block not in a loop yet!"); 638 OldLoop = L; 639 } 640 641 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 642 /// list with the indicated loop. 643 void changeTopLevelLoop(LoopT *OldLoop, 644 LoopT *NewLoop) { 645 typename std::vector<LoopT *>::iterator I = 646 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop); 647 assert(I != TopLevelLoops.end() && "Old loop not at top level!"); 648 *I = NewLoop; 649 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 && 650 "Loops already embedded into a subloop!"); 651 } 652 653 /// addTopLevelLoop - This adds the specified loop to the collection of 654 /// top-level loops. 655 void addTopLevelLoop(LoopT *New) { 656 assert(New->getParentLoop() == 0 && "Loop already in subloop!"); 657 TopLevelLoops.push_back(New); 658 } 659 660 /// removeBlock - This method completely removes BB from all data structures, 661 /// including all of the Loop objects it is nested in and our mapping from 662 /// BasicBlocks to loops. 663 void removeBlock(BlockT *BB) { 664 typename std::map<BlockT *, LoopT *>::iterator I = BBMap.find(BB); 665 if (I != BBMap.end()) { 666 for (LoopT *L = I->second; L; L = L->getParentLoop()) 667 L->removeBlockFromLoop(BB); 668 669 BBMap.erase(I); 670 } 671 } 672 673 // Internals 674 675 static bool isNotAlreadyContainedIn(const LoopT *SubLoop, 676 const LoopT *ParentLoop) { 677 if (SubLoop == 0) return true; 678 if (SubLoop == ParentLoop) return false; 679 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop); 680 } 681 682 void Calculate(DominatorTreeBase<BlockT> &DT) { 683 BlockT *RootNode = DT.getRootNode()->getBlock(); 684 685 for (df_iterator<BlockT*> NI = df_begin(RootNode), 686 NE = df_end(RootNode); NI != NE; ++NI) 687 if (LoopT *L = ConsiderForLoop(*NI, DT)) 688 TopLevelLoops.push_back(L); 689 } 690 691 LoopT *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) { 692 if (BBMap.find(BB) != BBMap.end()) return 0;// Haven't processed this node? 693 694 std::vector<BlockT *> TodoStack; 695 696 // Scan the predecessors of BB, checking to see if BB dominates any of 697 // them. This identifies backedges which target this node... 698 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 699 for (typename InvBlockTraits::ChildIteratorType I = 700 InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB); 701 I != E; ++I) 702 if (DT.dominates(BB, *I)) // If BB dominates it's predecessor... 703 TodoStack.push_back(*I); 704 705 if (TodoStack.empty()) return 0; // No backedges to this block... 706 707 // Create a new loop to represent this basic block... 708 LoopT *L = new LoopT(BB); 709 BBMap[BB] = L; 710 711 BlockT *EntryBlock = BB->getParent()->begin(); 712 713 while (!TodoStack.empty()) { // Process all the nodes in the loop 714 BlockT *X = TodoStack.back(); 715 TodoStack.pop_back(); 716 717 if (!L->contains(X) && // As of yet unprocessed?? 718 DT.dominates(EntryBlock, X)) { // X is reachable from entry block? 719 // Check to see if this block already belongs to a loop. If this occurs 720 // then we have a case where a loop that is supposed to be a child of 721 // the current loop was processed before the current loop. When this 722 // occurs, this child loop gets added to a part of the current loop, 723 // making it a sibling to the current loop. We have to reparent this 724 // loop. 725 if (LoopT *SubLoop = 726 const_cast<LoopT *>(getLoopFor(X))) 727 if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){ 728 // Remove the subloop from it's current parent... 729 assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L); 730 LoopT *SLP = SubLoop->ParentLoop; // SubLoopParent 731 typename std::vector<LoopT *>::iterator I = 732 std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop); 733 assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?"); 734 SLP->SubLoops.erase(I); // Remove from parent... 735 736 // Add the subloop to THIS loop... 737 SubLoop->ParentLoop = L; 738 L->SubLoops.push_back(SubLoop); 739 } 740 741 // Normal case, add the block to our loop... 742 L->Blocks.push_back(X); 743 744 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 745 746 // Add all of the predecessors of X to the end of the work stack... 747 TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X), 748 InvBlockTraits::child_end(X)); 749 } 750 } 751 752 // If there are any loops nested within this loop, create them now! 753 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 754 E = L->Blocks.end(); I != E; ++I) 755 if (LoopT *NewLoop = ConsiderForLoop(*I, DT)) { 756 L->SubLoops.push_back(NewLoop); 757 NewLoop->ParentLoop = L; 758 } 759 760 // Add the basic blocks that comprise this loop to the BBMap so that this 761 // loop can be found for them. 762 // 763 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 764 E = L->Blocks.end(); I != E; ++I) { 765 typename std::map<BlockT*, LoopT *>::iterator BBMI = BBMap.find(*I); 766 if (BBMI == BBMap.end()) // Not in map yet... 767 BBMap.insert(BBMI, std::make_pair(*I, L)); // Must be at this level 768 } 769 770 // Now that we have a list of all of the child loops of this loop, check to 771 // see if any of them should actually be nested inside of each other. We 772 // can accidentally pull loops our of their parents, so we must make sure to 773 // organize the loop nests correctly now. 774 { 775 std::map<BlockT *, LoopT *> ContainingLoops; 776 for (unsigned i = 0; i != L->SubLoops.size(); ++i) { 777 LoopT *Child = L->SubLoops[i]; 778 assert(Child->getParentLoop() == L && "Not proper child loop?"); 779 780 if (LoopT *ContainingLoop = ContainingLoops[Child->getHeader()]) { 781 // If there is already a loop which contains this loop, move this loop 782 // into the containing loop. 783 MoveSiblingLoopInto(Child, ContainingLoop); 784 --i; // The loop got removed from the SubLoops list. 785 } else { 786 // This is currently considered to be a top-level loop. Check to see 787 // if any of the contained blocks are loop headers for subloops we 788 // have already processed. 789 for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) { 790 LoopT *&BlockLoop = ContainingLoops[Child->Blocks[b]]; 791 if (BlockLoop == 0) { // Child block not processed yet... 792 BlockLoop = Child; 793 } else if (BlockLoop != Child) { 794 LoopT *SubLoop = BlockLoop; 795 // Reparent all of the blocks which used to belong to BlockLoops 796 for (unsigned j = 0, e = SubLoop->Blocks.size(); j != e; ++j) 797 ContainingLoops[SubLoop->Blocks[j]] = Child; 798 799 // There is already a loop which contains this block, that means 800 // that we should reparent the loop which the block is currently 801 // considered to belong to to be a child of this loop. 802 MoveSiblingLoopInto(SubLoop, Child); 803 --i; // We just shrunk the SubLoops list. 804 } 805 } 806 } 807 } 808 } 809 810 return L; 811 } 812 813 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside 814 /// of the NewParent Loop, instead of being a sibling of it. 815 void MoveSiblingLoopInto(LoopT *NewChild, 816 LoopT *NewParent) { 817 LoopT *OldParent = NewChild->getParentLoop(); 818 assert(OldParent && OldParent == NewParent->getParentLoop() && 819 NewChild != NewParent && "Not sibling loops!"); 820 821 // Remove NewChild from being a child of OldParent 822 typename std::vector<LoopT *>::iterator I = 823 std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(), 824 NewChild); 825 assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??"); 826 OldParent->SubLoops.erase(I); // Remove from parent's subloops list 827 NewChild->ParentLoop = 0; 828 829 InsertLoopInto(NewChild, NewParent); 830 } 831 832 /// InsertLoopInto - This inserts loop L into the specified parent loop. If 833 /// the parent loop contains a loop which should contain L, the loop gets 834 /// inserted into L instead. 835 void InsertLoopInto(LoopT *L, LoopT *Parent) { 836 BlockT *LHeader = L->getHeader(); 837 assert(Parent->contains(LHeader) && 838 "This loop should not be inserted here!"); 839 840 // Check to see if it belongs in a child loop... 841 for (unsigned i = 0, e = static_cast<unsigned>(Parent->SubLoops.size()); 842 i != e; ++i) 843 if (Parent->SubLoops[i]->contains(LHeader)) { 844 InsertLoopInto(L, Parent->SubLoops[i]); 845 return; 846 } 847 848 // If not, insert it here! 849 Parent->SubLoops.push_back(L); 850 L->ParentLoop = Parent; 851 } 852 853 // Debugging 854 855 void print(std::ostream &OS, const Module* ) const { 856 for (unsigned i = 0; i < TopLevelLoops.size(); ++i) 857 TopLevelLoops[i]->print(OS); 858 #if 0 859 for (std::map<BasicBlock*, LoopT*>::const_iterator I = BBMap.begin(), 860 E = BBMap.end(); I != E; ++I) 861 OS << "BB '" << I->first->getName() << "' level = " 862 << I->second->getLoopDepth() << "\n"; 863 #endif 864 } 865}; 866 867class LoopInfo : public FunctionPass { 868 LoopInfoBase<BasicBlock, Loop> LI; 869 friend class LoopBase<BasicBlock, Loop>; 870 871 void operator=(const LoopInfo &); // do not implement 872 LoopInfo(const LoopInfo &); // do not implement 873public: 874 static char ID; // Pass identification, replacement for typeid 875 876 LoopInfo() : FunctionPass(&ID) {} 877 878 LoopInfoBase<BasicBlock, Loop>& getBase() { return LI; } 879 880 /// iterator/begin/end - The interface to the top-level loops in the current 881 /// function. 882 /// 883 typedef LoopInfoBase<BasicBlock, Loop>::iterator iterator; 884 inline iterator begin() const { return LI.begin(); } 885 inline iterator end() const { return LI.end(); } 886 bool empty() const { return LI.empty(); } 887 888 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 889 /// block is in no loop (for example the entry node), null is returned. 890 /// 891 inline Loop *getLoopFor(const BasicBlock *BB) const { 892 return LI.getLoopFor(BB); 893 } 894 895 /// operator[] - same as getLoopFor... 896 /// 897 inline const Loop *operator[](const BasicBlock *BB) const { 898 return LI.getLoopFor(BB); 899 } 900 901 /// getLoopDepth - Return the loop nesting level of the specified block. A 902 /// depth of 0 means the block is not inside any loop. 903 /// 904 inline unsigned getLoopDepth(const BasicBlock *BB) const { 905 return LI.getLoopDepth(BB); 906 } 907 908 // isLoopHeader - True if the block is a loop header node 909 inline bool isLoopHeader(BasicBlock *BB) const { 910 return LI.isLoopHeader(BB); 911 } 912 913 /// runOnFunction - Calculate the natural loop information. 914 /// 915 virtual bool runOnFunction(Function &F); 916 917 virtual void releaseMemory() { LI.releaseMemory(); } 918 919 virtual void print(std::ostream &O, const Module* M = 0) const { 920 LI.print(O, M); 921 } 922 923 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 924 925 /// removeLoop - This removes the specified top-level loop from this loop info 926 /// object. The loop is not deleted, as it will presumably be inserted into 927 /// another loop. 928 inline Loop *removeLoop(iterator I) { return LI.removeLoop(I); } 929 930 /// changeLoopFor - Change the top-level loop that contains BB to the 931 /// specified loop. This should be used by transformations that restructure 932 /// the loop hierarchy tree. 933 inline void changeLoopFor(BasicBlock *BB, Loop *L) { 934 LI.changeLoopFor(BB, L); 935 } 936 937 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 938 /// list with the indicated loop. 939 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) { 940 LI.changeTopLevelLoop(OldLoop, NewLoop); 941 } 942 943 /// addTopLevelLoop - This adds the specified loop to the collection of 944 /// top-level loops. 945 inline void addTopLevelLoop(Loop *New) { 946 LI.addTopLevelLoop(New); 947 } 948 949 /// removeBlock - This method completely removes BB from all data structures, 950 /// including all of the Loop objects it is nested in and our mapping from 951 /// BasicBlocks to loops. 952 void removeBlock(BasicBlock *BB) { 953 LI.removeBlock(BB); 954 } 955 956 static bool isNotAlreadyContainedIn(const Loop *SubLoop, 957 const Loop *ParentLoop) { 958 return 959 LoopInfoBase<BasicBlock, Loop>::isNotAlreadyContainedIn(SubLoop, 960 ParentLoop); 961 } 962}; 963 964 965// Allow clients to walk the list of nested loops... 966template <> struct GraphTraits<const Loop*> { 967 typedef const Loop NodeType; 968 typedef LoopInfo::iterator ChildIteratorType; 969 970 static NodeType *getEntryNode(const Loop *L) { return L; } 971 static inline ChildIteratorType child_begin(NodeType *N) { 972 return N->begin(); 973 } 974 static inline ChildIteratorType child_end(NodeType *N) { 975 return N->end(); 976 } 977}; 978 979template <> struct GraphTraits<Loop*> { 980 typedef Loop NodeType; 981 typedef LoopInfo::iterator ChildIteratorType; 982 983 static NodeType *getEntryNode(Loop *L) { return L; } 984 static inline ChildIteratorType child_begin(NodeType *N) { 985 return N->begin(); 986 } 987 static inline ChildIteratorType child_end(NodeType *N) { 988 return N->end(); 989 } 990}; 991 992template<class BlockT, class LoopT> 993void 994LoopBase<BlockT, LoopT>::addBasicBlockToLoop(BlockT *NewBB, 995 LoopInfoBase<BlockT, LoopT> &LIB) { 996 assert((Blocks.empty() || LIB[getHeader()] == this) && 997 "Incorrect LI specified for this loop!"); 998 assert(NewBB && "Cannot add a null basic block to the loop!"); 999 assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!"); 1000 1001 LoopT *L = static_cast<LoopT *>(this); 1002 1003 // Add the loop mapping to the LoopInfo object... 1004 LIB.BBMap[NewBB] = L; 1005 1006 // Add the basic block to this loop and all parent loops... 1007 while (L) { 1008 L->Blocks.push_back(NewBB); 1009 L = L->getParentLoop(); 1010 } 1011} 1012 1013} // End llvm namespace 1014 1015#endif 1016