LoopInfo.h revision b7532e254810aba26da9b65ee2c65788695f8c30
1//===- llvm/Analysis/LoopInfo.h - Natural Loop Calculator -------*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file defines the LoopInfo class that is used to identify natural loops 11// and determine the loop depth of various nodes of the CFG. A natural loop 12// has exactly one entry-point, which is called the header. Note that natural 13// loops may actually be several loops that share the same header node. 14// 15// This analysis calculates the nesting structure of loops in a function. For 16// each natural loop identified, this analysis identifies natural loops 17// contained entirely within the loop and the basic blocks the make up the loop. 18// 19// It can calculate on the fly various bits of information, for example: 20// 21// * whether there is a preheader for the loop 22// * the number of back edges to the header 23// * whether or not a particular block branches out of the loop 24// * the successor blocks of the loop 25// * the loop depth 26// * the trip count 27// * etc... 28// 29//===----------------------------------------------------------------------===// 30 31#ifndef LLVM_ANALYSIS_LOOP_INFO_H 32#define LLVM_ANALYSIS_LOOP_INFO_H 33 34#include "llvm/Pass.h" 35#include "llvm/ADT/DepthFirstIterator.h" 36#include "llvm/ADT/GraphTraits.h" 37#include "llvm/ADT/SmallVector.h" 38#include "llvm/Analysis/Dominators.h" 39#include "llvm/Support/CFG.h" 40#include "llvm/Support/raw_ostream.h" 41#include <algorithm> 42 43namespace llvm { 44 45template<typename T> 46static void RemoveFromVector(std::vector<T*> &V, T *N) { 47 typename std::vector<T*>::iterator I = std::find(V.begin(), V.end(), N); 48 assert(I != V.end() && "N is not in this list!"); 49 V.erase(I); 50} 51 52class DominatorTree; 53class LoopInfo; 54class Loop; 55template<class N, class M> class LoopInfoBase; 56template<class N, class M> class LoopBase; 57 58//===----------------------------------------------------------------------===// 59/// LoopBase class - Instances of this class are used to represent loops that 60/// are detected in the flow graph 61/// 62template<class BlockT, class LoopT> 63class LoopBase { 64 LoopT *ParentLoop; 65 // SubLoops - Loops contained entirely within this one. 66 std::vector<LoopT *> SubLoops; 67 68 // Blocks - The list of blocks in this loop. First entry is the header node. 69 std::vector<BlockT*> Blocks; 70 71 // DO NOT IMPLEMENT 72 LoopBase(const LoopBase<BlockT, LoopT> &); 73 // DO NOT IMPLEMENT 74 const LoopBase<BlockT, LoopT>&operator=(const LoopBase<BlockT, LoopT> &); 75public: 76 /// Loop ctor - This creates an empty loop. 77 LoopBase() : ParentLoop(0) {} 78 ~LoopBase() { 79 for (size_t i = 0, e = SubLoops.size(); i != e; ++i) 80 delete SubLoops[i]; 81 } 82 83 /// getLoopDepth - Return the nesting level of this loop. An outer-most 84 /// loop has depth 1, for consistency with loop depth values used for basic 85 /// blocks, where depth 0 is used for blocks not inside any loops. 86 unsigned getLoopDepth() const { 87 unsigned D = 1; 88 for (const LoopT *CurLoop = ParentLoop; CurLoop; 89 CurLoop = CurLoop->ParentLoop) 90 ++D; 91 return D; 92 } 93 BlockT *getHeader() const { return Blocks.front(); } 94 LoopT *getParentLoop() const { return ParentLoop; } 95 96 /// contains - Return true if the specified basic block is in this loop 97 /// 98 bool contains(const BlockT *BB) const { 99 return std::find(block_begin(), block_end(), BB) != block_end(); 100 } 101 102 /// iterator/begin/end - Return the loops contained entirely within this loop. 103 /// 104 const std::vector<LoopT *> &getSubLoops() const { return SubLoops; } 105 typedef typename std::vector<LoopT *>::const_iterator iterator; 106 iterator begin() const { return SubLoops.begin(); } 107 iterator end() const { return SubLoops.end(); } 108 bool empty() const { return SubLoops.empty(); } 109 110 /// getBlocks - Get a list of the basic blocks which make up this loop. 111 /// 112 const std::vector<BlockT*> &getBlocks() const { return Blocks; } 113 typedef typename std::vector<BlockT*>::const_iterator block_iterator; 114 block_iterator block_begin() const { return Blocks.begin(); } 115 block_iterator block_end() const { return Blocks.end(); } 116 117 /// isLoopExit - True if terminator in the block can branch to another block 118 /// that is outside of the current loop. 119 /// 120 bool isLoopExit(const BlockT *BB) const { 121 typedef GraphTraits<BlockT*> BlockTraits; 122 for (typename BlockTraits::ChildIteratorType SI = 123 BlockTraits::child_begin(const_cast<BlockT*>(BB)), 124 SE = BlockTraits::child_end(const_cast<BlockT*>(BB)); SI != SE; ++SI) { 125 if (!contains(*SI)) 126 return true; 127 } 128 return false; 129 } 130 131 /// getNumBackEdges - Calculate the number of back edges to the loop header 132 /// 133 unsigned getNumBackEdges() const { 134 unsigned NumBackEdges = 0; 135 BlockT *H = getHeader(); 136 137 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 138 for (typename InvBlockTraits::ChildIteratorType I = 139 InvBlockTraits::child_begin(const_cast<BlockT*>(H)), 140 E = InvBlockTraits::child_end(const_cast<BlockT*>(H)); I != E; ++I) 141 if (contains(*I)) 142 ++NumBackEdges; 143 144 return NumBackEdges; 145 } 146 147 //===--------------------------------------------------------------------===// 148 // APIs for simple analysis of the loop. 149 // 150 // Note that all of these methods can fail on general loops (ie, there may not 151 // be a preheader, etc). For best success, the loop simplification and 152 // induction variable canonicalization pass should be used to normalize loops 153 // for easy analysis. These methods assume canonical loops. 154 155 /// getExitingBlocks - Return all blocks inside the loop that have successors 156 /// outside of the loop. These are the blocks _inside of the current loop_ 157 /// which branch out. The returned list is always unique. 158 /// 159 void getExitingBlocks(SmallVectorImpl<BlockT *> &ExitingBlocks) const { 160 // Sort the blocks vector so that we can use binary search to do quick 161 // lookups. 162 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 163 std::sort(LoopBBs.begin(), LoopBBs.end()); 164 165 typedef GraphTraits<BlockT*> BlockTraits; 166 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) 167 for (typename BlockTraits::ChildIteratorType I = 168 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 169 I != E; ++I) 170 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) { 171 // Not in current loop? It must be an exit block. 172 ExitingBlocks.push_back(*BI); 173 break; 174 } 175 } 176 177 /// getExitingBlock - If getExitingBlocks would return exactly one block, 178 /// return that block. Otherwise return null. 179 BlockT *getExitingBlock() const { 180 SmallVector<BlockT*, 8> ExitingBlocks; 181 getExitingBlocks(ExitingBlocks); 182 if (ExitingBlocks.size() == 1) 183 return ExitingBlocks[0]; 184 return 0; 185 } 186 187 /// getExitBlocks - Return all of the successor blocks of this loop. These 188 /// are the blocks _outside of the current loop_ which are branched to. 189 /// 190 void getExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const { 191 // Sort the blocks vector so that we can use binary search to do quick 192 // lookups. 193 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 194 std::sort(LoopBBs.begin(), LoopBBs.end()); 195 196 typedef GraphTraits<BlockT*> BlockTraits; 197 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) 198 for (typename BlockTraits::ChildIteratorType I = 199 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 200 I != E; ++I) 201 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) 202 // Not in current loop? It must be an exit block. 203 ExitBlocks.push_back(*I); 204 } 205 206 /// getExitBlock - If getExitBlocks would return exactly one block, 207 /// return that block. Otherwise return null. 208 BlockT *getExitBlock() const { 209 SmallVector<BlockT*, 8> ExitBlocks; 210 getExitBlocks(ExitBlocks); 211 if (ExitBlocks.size() == 1) 212 return ExitBlocks[0]; 213 return 0; 214 } 215 216 /// getExitEdges - Return all pairs of (_inside_block_,_outside_block_). 217 typedef std::pair<const BlockT*,const BlockT*> Edge; 218 void getExitEdges(SmallVectorImpl<Edge> &ExitEdges) const { 219 // Sort the blocks vector so that we can use binary search to do quick 220 // lookups. 221 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 222 std::sort(LoopBBs.begin(), LoopBBs.end()); 223 224 typedef GraphTraits<BlockT*> BlockTraits; 225 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) 226 for (typename BlockTraits::ChildIteratorType I = 227 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 228 I != E; ++I) 229 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) 230 // Not in current loop? It must be an exit block. 231 ExitEdges.push_back(std::make_pair(*BI, *I)); 232 } 233 234 /// getLoopPreheader - If there is a preheader for this loop, return it. A 235 /// loop has a preheader if there is only one edge to the header of the loop 236 /// from outside of the loop. If this is the case, the block branching to the 237 /// header of the loop is the preheader node. 238 /// 239 /// This method returns null if there is no preheader for the loop. 240 /// 241 BlockT *getLoopPreheader() const { 242 // Keep track of nodes outside the loop branching to the header... 243 BlockT *Out = 0; 244 245 // Loop over the predecessors of the header node... 246 BlockT *Header = getHeader(); 247 typedef GraphTraits<BlockT*> BlockTraits; 248 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 249 for (typename InvBlockTraits::ChildIteratorType PI = 250 InvBlockTraits::child_begin(Header), 251 PE = InvBlockTraits::child_end(Header); PI != PE; ++PI) 252 if (!contains(*PI)) { // If the block is not in the loop... 253 if (Out && Out != *PI) 254 return 0; // Multiple predecessors outside the loop 255 Out = *PI; 256 } 257 258 // Make sure there is only one exit out of the preheader. 259 assert(Out && "Header of loop has no predecessors from outside loop?"); 260 typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out); 261 ++SI; 262 if (SI != BlockTraits::child_end(Out)) 263 return 0; // Multiple exits from the block, must not be a preheader. 264 265 // If there is exactly one preheader, return it. If there was zero, then 266 // Out is still null. 267 return Out; 268 } 269 270 /// getLoopLatch - If there is a single latch block for this loop, return it. 271 /// A latch block is a block that contains a branch back to the header. 272 /// A loop header in normal form has two edges into it: one from a preheader 273 /// and one from a latch block. 274 BlockT *getLoopLatch() const { 275 BlockT *Header = getHeader(); 276 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 277 typename InvBlockTraits::ChildIteratorType PI = 278 InvBlockTraits::child_begin(Header); 279 typename InvBlockTraits::ChildIteratorType PE = 280 InvBlockTraits::child_end(Header); 281 if (PI == PE) return 0; // no preds? 282 283 BlockT *Latch = 0; 284 if (contains(*PI)) 285 Latch = *PI; 286 ++PI; 287 if (PI == PE) return 0; // only one pred? 288 289 if (contains(*PI)) { 290 if (Latch) return 0; // multiple backedges 291 Latch = *PI; 292 } 293 ++PI; 294 if (PI != PE) return 0; // more than two preds 295 296 return Latch; 297 } 298 299 //===--------------------------------------------------------------------===// 300 // APIs for updating loop information after changing the CFG 301 // 302 303 /// addBasicBlockToLoop - This method is used by other analyses to update loop 304 /// information. NewBB is set to be a new member of the current loop. 305 /// Because of this, it is added as a member of all parent loops, and is added 306 /// to the specified LoopInfo object as being in the current basic block. It 307 /// is not valid to replace the loop header with this method. 308 /// 309 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LI); 310 311 /// replaceChildLoopWith - This is used when splitting loops up. It replaces 312 /// the OldChild entry in our children list with NewChild, and updates the 313 /// parent pointer of OldChild to be null and the NewChild to be this loop. 314 /// This updates the loop depth of the new child. 315 void replaceChildLoopWith(LoopT *OldChild, 316 LoopT *NewChild) { 317 assert(OldChild->ParentLoop == this && "This loop is already broken!"); 318 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 319 typename std::vector<LoopT *>::iterator I = 320 std::find(SubLoops.begin(), SubLoops.end(), OldChild); 321 assert(I != SubLoops.end() && "OldChild not in loop!"); 322 *I = NewChild; 323 OldChild->ParentLoop = 0; 324 NewChild->ParentLoop = static_cast<LoopT *>(this); 325 } 326 327 /// addChildLoop - Add the specified loop to be a child of this loop. This 328 /// updates the loop depth of the new child. 329 /// 330 void addChildLoop(LoopT *NewChild) { 331 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 332 NewChild->ParentLoop = static_cast<LoopT *>(this); 333 SubLoops.push_back(NewChild); 334 } 335 336 /// removeChildLoop - This removes the specified child from being a subloop of 337 /// this loop. The loop is not deleted, as it will presumably be inserted 338 /// into another loop. 339 LoopT *removeChildLoop(iterator I) { 340 assert(I != SubLoops.end() && "Cannot remove end iterator!"); 341 LoopT *Child = *I; 342 assert(Child->ParentLoop == this && "Child is not a child of this loop!"); 343 SubLoops.erase(SubLoops.begin()+(I-begin())); 344 Child->ParentLoop = 0; 345 return Child; 346 } 347 348 /// addBlockEntry - This adds a basic block directly to the basic block list. 349 /// This should only be used by transformations that create new loops. Other 350 /// transformations should use addBasicBlockToLoop. 351 void addBlockEntry(BlockT *BB) { 352 Blocks.push_back(BB); 353 } 354 355 /// moveToHeader - This method is used to move BB (which must be part of this 356 /// loop) to be the loop header of the loop (the block that dominates all 357 /// others). 358 void moveToHeader(BlockT *BB) { 359 if (Blocks[0] == BB) return; 360 for (unsigned i = 0; ; ++i) { 361 assert(i != Blocks.size() && "Loop does not contain BB!"); 362 if (Blocks[i] == BB) { 363 Blocks[i] = Blocks[0]; 364 Blocks[0] = BB; 365 return; 366 } 367 } 368 } 369 370 /// removeBlockFromLoop - This removes the specified basic block from the 371 /// current loop, updating the Blocks as appropriate. This does not update 372 /// the mapping in the LoopInfo class. 373 void removeBlockFromLoop(BlockT *BB) { 374 RemoveFromVector(Blocks, BB); 375 } 376 377 /// verifyLoop - Verify loop structure 378 void verifyLoop() const { 379#ifndef NDEBUG 380 assert(!Blocks.empty() && "Loop header is missing"); 381 assert(getHeader() && "Loop header is missing"); 382 383 // Sort the blocks vector so that we can use binary search to do quick 384 // lookups. 385 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 386 std::sort(LoopBBs.begin(), LoopBBs.end()); 387 388 // Check the individual blocks. 389 for (block_iterator I = block_begin(), E = block_end(); I != E; ++I) { 390 BlockT *BB = *I; 391 bool HasInsideLoopSuccs = false; 392 bool HasInsideLoopPreds = false; 393 SmallVector<BlockT *, 2> OutsideLoopPreds; 394 395 typedef GraphTraits<BlockT*> BlockTraits; 396 for (typename BlockTraits::ChildIteratorType SI = 397 BlockTraits::child_begin(BB), SE = BlockTraits::child_end(BB); 398 SI != SE; ++SI) 399 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *SI)) { 400 HasInsideLoopSuccs = true; 401 break; 402 } 403 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 404 for (typename InvBlockTraits::ChildIteratorType PI = 405 InvBlockTraits::child_begin(BB), PE = InvBlockTraits::child_end(BB); 406 PI != PE; ++PI) { 407 if (std::binary_search(LoopBBs.begin(), LoopBBs.end(), *PI)) 408 HasInsideLoopPreds = true; 409 else 410 OutsideLoopPreds.push_back(*PI); 411 } 412 413 if (BB == getHeader()) { 414 assert(!OutsideLoopPreds.empty() && "Loop is unreachable!"); 415 } else if (!OutsideLoopPreds.empty()) { 416 // A non-header loop shouldn't be reachable from outside the loop, 417 // though it is permitted if the predecessor is not itself actually 418 // reachable. 419 BlockT *EntryBB = BB->getParent()->begin(); 420 for (df_iterator<BlockT *> NI = df_begin(EntryBB), 421 NE = df_end(EntryBB); NI != NE; ++NI) 422 for (unsigned i = 0, e = OutsideLoopPreds.size(); i != e; ++i) 423 assert(*NI != OutsideLoopPreds[i] && 424 "Loop has multiple entry points!"); 425 } 426 assert(HasInsideLoopPreds && "Loop block has no in-loop predecessors!"); 427 assert(HasInsideLoopSuccs && "Loop block has no in-loop successors!"); 428 assert(BB != getHeader()->getParent()->begin() && 429 "Loop contains function entry block!"); 430 } 431 432 // Check the subloops. 433 for (iterator I = begin(), E = end(); I != E; ++I) 434 // Each block in each subloop should be contained within this loop. 435 for (block_iterator BI = (*I)->block_begin(), BE = (*I)->block_end(); 436 BI != BE; ++BI) { 437 assert(std::binary_search(LoopBBs.begin(), LoopBBs.end(), *BI) && 438 "Loop does not contain all the blocks of a subloop!"); 439 } 440 441 // Check the parent loop pointer. 442 if (ParentLoop) { 443 assert(std::find(ParentLoop->begin(), ParentLoop->end(), this) != 444 ParentLoop->end() && 445 "Loop is not a subloop of its parent!"); 446 } 447#endif 448 } 449 450 /// verifyLoop - Verify loop structure of this loop and all nested loops. 451 void verifyLoopNest() const { 452 // Verify this loop. 453 verifyLoop(); 454 // Verify the subloops. 455 for (iterator I = begin(), E = end(); I != E; ++I) 456 (*I)->verifyLoopNest(); 457 } 458 459 void print(raw_ostream &OS, unsigned Depth = 0) const { 460 OS.indent(Depth*2) << "Loop at depth " << getLoopDepth() 461 << " containing: "; 462 463 for (unsigned i = 0; i < getBlocks().size(); ++i) { 464 if (i) OS << ","; 465 BlockT *BB = getBlocks()[i]; 466 WriteAsOperand(OS, BB, false); 467 if (BB == getHeader()) OS << "<header>"; 468 if (BB == getLoopLatch()) OS << "<latch>"; 469 if (isLoopExit(BB)) OS << "<exit>"; 470 } 471 OS << "\n"; 472 473 for (iterator I = begin(), E = end(); I != E; ++I) 474 (*I)->print(OS, Depth+2); 475 } 476 477 void dump() const { 478 print(errs()); 479 } 480 481protected: 482 friend class LoopInfoBase<BlockT, LoopT>; 483 explicit LoopBase(BlockT *BB) : ParentLoop(0) { 484 Blocks.push_back(BB); 485 } 486}; 487 488class Loop : public LoopBase<BasicBlock, Loop> { 489public: 490 Loop() {} 491 492 /// isLoopInvariant - Return true if the specified value is loop invariant 493 /// 494 bool isLoopInvariant(Value *V) const; 495 496 /// isLoopInvariant - Return true if the specified instruction is 497 /// loop-invariant. 498 /// 499 bool isLoopInvariant(Instruction *I) const; 500 501 /// makeLoopInvariant - If the given value is an instruction inside of the 502 /// loop and it can be hoisted, do so to make it trivially loop-invariant. 503 /// Return true if the value after any hoisting is loop invariant. This 504 /// function can be used as a slightly more aggressive replacement for 505 /// isLoopInvariant. 506 /// 507 /// If InsertPt is specified, it is the point to hoist instructions to. 508 /// If null, the terminator of the loop preheader is used. 509 /// 510 bool makeLoopInvariant(Value *V, bool &Changed, 511 Instruction *InsertPt = 0) const; 512 513 /// makeLoopInvariant - If the given instruction is inside of the 514 /// loop and it can be hoisted, do so to make it trivially loop-invariant. 515 /// Return true if the instruction after any hoisting is loop invariant. This 516 /// function can be used as a slightly more aggressive replacement for 517 /// isLoopInvariant. 518 /// 519 /// If InsertPt is specified, it is the point to hoist instructions to. 520 /// If null, the terminator of the loop preheader is used. 521 /// 522 bool makeLoopInvariant(Instruction *I, bool &Changed, 523 Instruction *InsertPt = 0) const; 524 525 /// getCanonicalInductionVariable - Check to see if the loop has a canonical 526 /// induction variable: an integer recurrence that starts at 0 and increments 527 /// by one each time through the loop. If so, return the phi node that 528 /// corresponds to it. 529 /// 530 /// The IndVarSimplify pass transforms loops to have a canonical induction 531 /// variable. 532 /// 533 PHINode *getCanonicalInductionVariable() const; 534 535 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds 536 /// the canonical induction variable value for the "next" iteration of the 537 /// loop. This always succeeds if getCanonicalInductionVariable succeeds. 538 /// 539 Instruction *getCanonicalInductionVariableIncrement() const; 540 541 /// getTripCount - Return a loop-invariant LLVM value indicating the number of 542 /// times the loop will be executed. Note that this means that the backedge 543 /// of the loop executes N-1 times. If the trip-count cannot be determined, 544 /// this returns null. 545 /// 546 /// The IndVarSimplify pass transforms loops to have a form that this 547 /// function easily understands. 548 /// 549 Value *getTripCount() const; 550 551 /// getSmallConstantTripCount - Returns the trip count of this loop as a 552 /// normal unsigned value, if possible. Returns 0 if the trip count is unknown 553 /// of not constant. Will also return 0 if the trip count is very large 554 /// (>= 2^32) 555 unsigned getSmallConstantTripCount() const; 556 557 /// getSmallConstantTripMultiple - Returns the largest constant divisor of the 558 /// trip count of this loop as a normal unsigned value, if possible. This 559 /// means that the actual trip count is always a multiple of the returned 560 /// value (don't forget the trip count could very well be zero as well!). 561 /// 562 /// Returns 1 if the trip count is unknown or not guaranteed to be the 563 /// multiple of a constant (which is also the case if the trip count is simply 564 /// constant, use getSmallConstantTripCount for that case), Will also return 1 565 /// if the trip count is very large (>= 2^32). 566 unsigned getSmallConstantTripMultiple() const; 567 568 /// isLCSSAForm - Return true if the Loop is in LCSSA form 569 bool isLCSSAForm() const; 570 571 /// isLoopSimplifyForm - Return true if the Loop is in the form that 572 /// the LoopSimplify form transforms loops to, which is sometimes called 573 /// normal form. 574 bool isLoopSimplifyForm() const; 575 576 /// getUniqueExitBlocks - Return all unique successor blocks of this loop. 577 /// These are the blocks _outside of the current loop_ which are branched to. 578 /// This assumes that loop is in canonical form. 579 /// 580 void getUniqueExitBlocks(SmallVectorImpl<BasicBlock *> &ExitBlocks) const; 581 582 /// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one 583 /// block, return that block. Otherwise return null. 584 BasicBlock *getUniqueExitBlock() const; 585 586private: 587 friend class LoopInfoBase<BasicBlock, Loop>; 588 explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {} 589}; 590 591//===----------------------------------------------------------------------===// 592/// LoopInfo - This class builds and contains all of the top level loop 593/// structures in the specified function. 594/// 595 596template<class BlockT, class LoopT> 597class LoopInfoBase { 598 // BBMap - Mapping of basic blocks to the inner most loop they occur in 599 std::map<BlockT *, LoopT *> BBMap; 600 std::vector<LoopT *> TopLevelLoops; 601 friend class LoopBase<BlockT, LoopT>; 602 603 void operator=(const LoopInfoBase &); // do not implement 604 LoopInfoBase(const LoopInfo &); // do not implement 605public: 606 LoopInfoBase() { } 607 ~LoopInfoBase() { releaseMemory(); } 608 609 void releaseMemory() { 610 for (typename std::vector<LoopT *>::iterator I = 611 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I) 612 delete *I; // Delete all of the loops... 613 614 BBMap.clear(); // Reset internal state of analysis 615 TopLevelLoops.clear(); 616 } 617 618 /// iterator/begin/end - The interface to the top-level loops in the current 619 /// function. 620 /// 621 typedef typename std::vector<LoopT *>::const_iterator iterator; 622 iterator begin() const { return TopLevelLoops.begin(); } 623 iterator end() const { return TopLevelLoops.end(); } 624 bool empty() const { return TopLevelLoops.empty(); } 625 626 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 627 /// block is in no loop (for example the entry node), null is returned. 628 /// 629 LoopT *getLoopFor(const BlockT *BB) const { 630 typename std::map<BlockT *, LoopT *>::const_iterator I= 631 BBMap.find(const_cast<BlockT*>(BB)); 632 return I != BBMap.end() ? I->second : 0; 633 } 634 635 /// operator[] - same as getLoopFor... 636 /// 637 const LoopT *operator[](const BlockT *BB) const { 638 return getLoopFor(BB); 639 } 640 641 /// getLoopDepth - Return the loop nesting level of the specified block. A 642 /// depth of 0 means the block is not inside any loop. 643 /// 644 unsigned getLoopDepth(const BlockT *BB) const { 645 const LoopT *L = getLoopFor(BB); 646 return L ? L->getLoopDepth() : 0; 647 } 648 649 // isLoopHeader - True if the block is a loop header node 650 bool isLoopHeader(BlockT *BB) const { 651 const LoopT *L = getLoopFor(BB); 652 return L && L->getHeader() == BB; 653 } 654 655 /// removeLoop - This removes the specified top-level loop from this loop info 656 /// object. The loop is not deleted, as it will presumably be inserted into 657 /// another loop. 658 LoopT *removeLoop(iterator I) { 659 assert(I != end() && "Cannot remove end iterator!"); 660 LoopT *L = *I; 661 assert(L->getParentLoop() == 0 && "Not a top-level loop!"); 662 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin())); 663 return L; 664 } 665 666 /// changeLoopFor - Change the top-level loop that contains BB to the 667 /// specified loop. This should be used by transformations that restructure 668 /// the loop hierarchy tree. 669 void changeLoopFor(BlockT *BB, LoopT *L) { 670 LoopT *&OldLoop = BBMap[BB]; 671 assert(OldLoop && "Block not in a loop yet!"); 672 OldLoop = L; 673 } 674 675 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 676 /// list with the indicated loop. 677 void changeTopLevelLoop(LoopT *OldLoop, 678 LoopT *NewLoop) { 679 typename std::vector<LoopT *>::iterator I = 680 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop); 681 assert(I != TopLevelLoops.end() && "Old loop not at top level!"); 682 *I = NewLoop; 683 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 && 684 "Loops already embedded into a subloop!"); 685 } 686 687 /// addTopLevelLoop - This adds the specified loop to the collection of 688 /// top-level loops. 689 void addTopLevelLoop(LoopT *New) { 690 assert(New->getParentLoop() == 0 && "Loop already in subloop!"); 691 TopLevelLoops.push_back(New); 692 } 693 694 /// removeBlock - This method completely removes BB from all data structures, 695 /// including all of the Loop objects it is nested in and our mapping from 696 /// BasicBlocks to loops. 697 void removeBlock(BlockT *BB) { 698 typename std::map<BlockT *, LoopT *>::iterator I = BBMap.find(BB); 699 if (I != BBMap.end()) { 700 for (LoopT *L = I->second; L; L = L->getParentLoop()) 701 L->removeBlockFromLoop(BB); 702 703 BBMap.erase(I); 704 } 705 } 706 707 // Internals 708 709 static bool isNotAlreadyContainedIn(const LoopT *SubLoop, 710 const LoopT *ParentLoop) { 711 if (SubLoop == 0) return true; 712 if (SubLoop == ParentLoop) return false; 713 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop); 714 } 715 716 void Calculate(DominatorTreeBase<BlockT> &DT) { 717 BlockT *RootNode = DT.getRootNode()->getBlock(); 718 719 for (df_iterator<BlockT*> NI = df_begin(RootNode), 720 NE = df_end(RootNode); NI != NE; ++NI) 721 if (LoopT *L = ConsiderForLoop(*NI, DT)) 722 TopLevelLoops.push_back(L); 723 } 724 725 LoopT *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) { 726 if (BBMap.find(BB) != BBMap.end()) return 0;// Haven't processed this node? 727 728 std::vector<BlockT *> TodoStack; 729 730 // Scan the predecessors of BB, checking to see if BB dominates any of 731 // them. This identifies backedges which target this node... 732 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 733 for (typename InvBlockTraits::ChildIteratorType I = 734 InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB); 735 I != E; ++I) 736 if (DT.dominates(BB, *I)) // If BB dominates its predecessor... 737 TodoStack.push_back(*I); 738 739 if (TodoStack.empty()) return 0; // No backedges to this block... 740 741 // Create a new loop to represent this basic block... 742 LoopT *L = new LoopT(BB); 743 BBMap[BB] = L; 744 745 BlockT *EntryBlock = BB->getParent()->begin(); 746 747 while (!TodoStack.empty()) { // Process all the nodes in the loop 748 BlockT *X = TodoStack.back(); 749 TodoStack.pop_back(); 750 751 if (!L->contains(X) && // As of yet unprocessed?? 752 DT.dominates(EntryBlock, X)) { // X is reachable from entry block? 753 // Check to see if this block already belongs to a loop. If this occurs 754 // then we have a case where a loop that is supposed to be a child of 755 // the current loop was processed before the current loop. When this 756 // occurs, this child loop gets added to a part of the current loop, 757 // making it a sibling to the current loop. We have to reparent this 758 // loop. 759 if (LoopT *SubLoop = 760 const_cast<LoopT *>(getLoopFor(X))) 761 if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){ 762 // Remove the subloop from its current parent... 763 assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L); 764 LoopT *SLP = SubLoop->ParentLoop; // SubLoopParent 765 typename std::vector<LoopT *>::iterator I = 766 std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop); 767 assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?"); 768 SLP->SubLoops.erase(I); // Remove from parent... 769 770 // Add the subloop to THIS loop... 771 SubLoop->ParentLoop = L; 772 L->SubLoops.push_back(SubLoop); 773 } 774 775 // Normal case, add the block to our loop... 776 L->Blocks.push_back(X); 777 778 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 779 780 // Add all of the predecessors of X to the end of the work stack... 781 TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X), 782 InvBlockTraits::child_end(X)); 783 } 784 } 785 786 // If there are any loops nested within this loop, create them now! 787 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 788 E = L->Blocks.end(); I != E; ++I) 789 if (LoopT *NewLoop = ConsiderForLoop(*I, DT)) { 790 L->SubLoops.push_back(NewLoop); 791 NewLoop->ParentLoop = L; 792 } 793 794 // Add the basic blocks that comprise this loop to the BBMap so that this 795 // loop can be found for them. 796 // 797 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 798 E = L->Blocks.end(); I != E; ++I) 799 BBMap.insert(std::make_pair(*I, L)); 800 801 // Now that we have a list of all of the child loops of this loop, check to 802 // see if any of them should actually be nested inside of each other. We 803 // can accidentally pull loops our of their parents, so we must make sure to 804 // organize the loop nests correctly now. 805 { 806 std::map<BlockT *, LoopT *> ContainingLoops; 807 for (unsigned i = 0; i != L->SubLoops.size(); ++i) { 808 LoopT *Child = L->SubLoops[i]; 809 assert(Child->getParentLoop() == L && "Not proper child loop?"); 810 811 if (LoopT *ContainingLoop = ContainingLoops[Child->getHeader()]) { 812 // If there is already a loop which contains this loop, move this loop 813 // into the containing loop. 814 MoveSiblingLoopInto(Child, ContainingLoop); 815 --i; // The loop got removed from the SubLoops list. 816 } else { 817 // This is currently considered to be a top-level loop. Check to see 818 // if any of the contained blocks are loop headers for subloops we 819 // have already processed. 820 for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) { 821 LoopT *&BlockLoop = ContainingLoops[Child->Blocks[b]]; 822 if (BlockLoop == 0) { // Child block not processed yet... 823 BlockLoop = Child; 824 } else if (BlockLoop != Child) { 825 LoopT *SubLoop = BlockLoop; 826 // Reparent all of the blocks which used to belong to BlockLoops 827 for (unsigned j = 0, e = SubLoop->Blocks.size(); j != e; ++j) 828 ContainingLoops[SubLoop->Blocks[j]] = Child; 829 830 // There is already a loop which contains this block, that means 831 // that we should reparent the loop which the block is currently 832 // considered to belong to to be a child of this loop. 833 MoveSiblingLoopInto(SubLoop, Child); 834 --i; // We just shrunk the SubLoops list. 835 } 836 } 837 } 838 } 839 } 840 841 return L; 842 } 843 844 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside 845 /// of the NewParent Loop, instead of being a sibling of it. 846 void MoveSiblingLoopInto(LoopT *NewChild, 847 LoopT *NewParent) { 848 LoopT *OldParent = NewChild->getParentLoop(); 849 assert(OldParent && OldParent == NewParent->getParentLoop() && 850 NewChild != NewParent && "Not sibling loops!"); 851 852 // Remove NewChild from being a child of OldParent 853 typename std::vector<LoopT *>::iterator I = 854 std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(), 855 NewChild); 856 assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??"); 857 OldParent->SubLoops.erase(I); // Remove from parent's subloops list 858 NewChild->ParentLoop = 0; 859 860 InsertLoopInto(NewChild, NewParent); 861 } 862 863 /// InsertLoopInto - This inserts loop L into the specified parent loop. If 864 /// the parent loop contains a loop which should contain L, the loop gets 865 /// inserted into L instead. 866 void InsertLoopInto(LoopT *L, LoopT *Parent) { 867 BlockT *LHeader = L->getHeader(); 868 assert(Parent->contains(LHeader) && 869 "This loop should not be inserted here!"); 870 871 // Check to see if it belongs in a child loop... 872 for (unsigned i = 0, e = static_cast<unsigned>(Parent->SubLoops.size()); 873 i != e; ++i) 874 if (Parent->SubLoops[i]->contains(LHeader)) { 875 InsertLoopInto(L, Parent->SubLoops[i]); 876 return; 877 } 878 879 // If not, insert it here! 880 Parent->SubLoops.push_back(L); 881 L->ParentLoop = Parent; 882 } 883 884 // Debugging 885 886 void print(raw_ostream &OS) const { 887 for (unsigned i = 0; i < TopLevelLoops.size(); ++i) 888 TopLevelLoops[i]->print(OS); 889 #if 0 890 for (std::map<BasicBlock*, LoopT*>::const_iterator I = BBMap.begin(), 891 E = BBMap.end(); I != E; ++I) 892 OS << "BB '" << I->first->getName() << "' level = " 893 << I->second->getLoopDepth() << "\n"; 894 #endif 895 } 896}; 897 898class LoopInfo : public FunctionPass { 899 LoopInfoBase<BasicBlock, Loop> LI; 900 friend class LoopBase<BasicBlock, Loop>; 901 902 void operator=(const LoopInfo &); // do not implement 903 LoopInfo(const LoopInfo &); // do not implement 904public: 905 static char ID; // Pass identification, replacement for typeid 906 907 LoopInfo() : FunctionPass(&ID) {} 908 909 LoopInfoBase<BasicBlock, Loop>& getBase() { return LI; } 910 911 /// iterator/begin/end - The interface to the top-level loops in the current 912 /// function. 913 /// 914 typedef LoopInfoBase<BasicBlock, Loop>::iterator iterator; 915 inline iterator begin() const { return LI.begin(); } 916 inline iterator end() const { return LI.end(); } 917 bool empty() const { return LI.empty(); } 918 919 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 920 /// block is in no loop (for example the entry node), null is returned. 921 /// 922 inline Loop *getLoopFor(const BasicBlock *BB) const { 923 return LI.getLoopFor(BB); 924 } 925 926 /// operator[] - same as getLoopFor... 927 /// 928 inline const Loop *operator[](const BasicBlock *BB) const { 929 return LI.getLoopFor(BB); 930 } 931 932 /// getLoopDepth - Return the loop nesting level of the specified block. A 933 /// depth of 0 means the block is not inside any loop. 934 /// 935 inline unsigned getLoopDepth(const BasicBlock *BB) const { 936 return LI.getLoopDepth(BB); 937 } 938 939 // isLoopHeader - True if the block is a loop header node 940 inline bool isLoopHeader(BasicBlock *BB) const { 941 return LI.isLoopHeader(BB); 942 } 943 944 /// runOnFunction - Calculate the natural loop information. 945 /// 946 virtual bool runOnFunction(Function &F); 947 948 virtual void verifyAnalysis() const; 949 950 virtual void releaseMemory() { LI.releaseMemory(); } 951 952 virtual void print(raw_ostream &O, const Module* M = 0) const; 953 954 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 955 956 /// removeLoop - This removes the specified top-level loop from this loop info 957 /// object. The loop is not deleted, as it will presumably be inserted into 958 /// another loop. 959 inline Loop *removeLoop(iterator I) { return LI.removeLoop(I); } 960 961 /// changeLoopFor - Change the top-level loop that contains BB to the 962 /// specified loop. This should be used by transformations that restructure 963 /// the loop hierarchy tree. 964 inline void changeLoopFor(BasicBlock *BB, Loop *L) { 965 LI.changeLoopFor(BB, L); 966 } 967 968 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 969 /// list with the indicated loop. 970 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) { 971 LI.changeTopLevelLoop(OldLoop, NewLoop); 972 } 973 974 /// addTopLevelLoop - This adds the specified loop to the collection of 975 /// top-level loops. 976 inline void addTopLevelLoop(Loop *New) { 977 LI.addTopLevelLoop(New); 978 } 979 980 /// removeBlock - This method completely removes BB from all data structures, 981 /// including all of the Loop objects it is nested in and our mapping from 982 /// BasicBlocks to loops. 983 void removeBlock(BasicBlock *BB) { 984 LI.removeBlock(BB); 985 } 986 987 static bool isNotAlreadyContainedIn(const Loop *SubLoop, 988 const Loop *ParentLoop) { 989 return 990 LoopInfoBase<BasicBlock, Loop>::isNotAlreadyContainedIn(SubLoop, 991 ParentLoop); 992 } 993}; 994 995 996// Allow clients to walk the list of nested loops... 997template <> struct GraphTraits<const Loop*> { 998 typedef const Loop NodeType; 999 typedef LoopInfo::iterator ChildIteratorType; 1000 1001 static NodeType *getEntryNode(const 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 <> struct GraphTraits<Loop*> { 1011 typedef Loop NodeType; 1012 typedef LoopInfo::iterator ChildIteratorType; 1013 1014 static NodeType *getEntryNode(Loop *L) { return L; } 1015 static inline ChildIteratorType child_begin(NodeType *N) { 1016 return N->begin(); 1017 } 1018 static inline ChildIteratorType child_end(NodeType *N) { 1019 return N->end(); 1020 } 1021}; 1022 1023template<class BlockT, class LoopT> 1024void 1025LoopBase<BlockT, LoopT>::addBasicBlockToLoop(BlockT *NewBB, 1026 LoopInfoBase<BlockT, LoopT> &LIB) { 1027 assert((Blocks.empty() || LIB[getHeader()] == this) && 1028 "Incorrect LI specified for this loop!"); 1029 assert(NewBB && "Cannot add a null basic block to the loop!"); 1030 assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!"); 1031 1032 LoopT *L = static_cast<LoopT *>(this); 1033 1034 // Add the loop mapping to the LoopInfo object... 1035 LIB.BBMap[NewBB] = L; 1036 1037 // Add the basic block to this loop and all parent loops... 1038 while (L) { 1039 L->Blocks.push_back(NewBB); 1040 L = L->getParentLoop(); 1041 } 1042} 1043 1044} // End llvm namespace 1045 1046#endif 1047