LoopInfo.h revision 8fc5ad33691b2a0672a7487da1f56b6f7f675a1b
1//===- llvm/Analysis/LoopInfo.h - Natural Loop Calculator -------*- C++ -*-===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// This file defines the LoopInfo class that is used to identify natural loops 11// and determine the loop depth of various nodes of the CFG. Note that natural 12// loops may actually be several loops that share the same header node. 13// 14// This analysis calculates the nesting structure of loops in a function. For 15// each natural loop identified, this analysis identifies natural loops 16// contained entirely within the loop and the basic blocks the make up the loop. 17// 18// It can calculate on the fly various bits of information, for example: 19// 20// * whether there is a preheader for the loop 21// * the number of back edges to the header 22// * whether or not a particular block branches out of the loop 23// * the successor blocks of the loop 24// * the loop depth 25// * the trip count 26// * etc... 27// 28//===----------------------------------------------------------------------===// 29 30#ifndef LLVM_ANALYSIS_LOOP_INFO_H 31#define LLVM_ANALYSIS_LOOP_INFO_H 32 33#include "llvm/Pass.h" 34#include "llvm/ADT/DepthFirstIterator.h" 35#include "llvm/ADT/GraphTraits.h" 36#include "llvm/ADT/SmallVector.h" 37#include "llvm/Analysis/Dominators.h" 38#include "llvm/Support/CFG.h" 39#include "llvm/Support/raw_ostream.h" 40#include <algorithm> 41 42namespace llvm { 43 44template<typename T> 45static void RemoveFromVector(std::vector<T*> &V, T *N) { 46 typename std::vector<T*>::iterator I = std::find(V.begin(), V.end(), N); 47 assert(I != V.end() && "N is not in this list!"); 48 V.erase(I); 49} 50 51class DominatorTree; 52class LoopInfo; 53class Loop; 54template<class N, class M> class LoopInfoBase; 55template<class N, class M> class LoopBase; 56 57//===----------------------------------------------------------------------===// 58/// LoopBase class - Instances of this class are used to represent loops that 59/// are detected in the flow graph 60/// 61template<class BlockT, class LoopT> 62class LoopBase { 63 LoopT *ParentLoop; 64 // SubLoops - Loops contained entirely within this one. 65 std::vector<LoopT *> SubLoops; 66 67 // Blocks - The list of blocks in this loop. First entry is the header node. 68 std::vector<BlockT*> Blocks; 69 70 // DO NOT IMPLEMENT 71 LoopBase(const LoopBase<BlockT, LoopT> &); 72 // DO NOT IMPLEMENT 73 const LoopBase<BlockT, LoopT>&operator=(const LoopBase<BlockT, LoopT> &); 74public: 75 /// Loop ctor - This creates an empty loop. 76 LoopBase() : ParentLoop(0) {} 77 ~LoopBase() { 78 for (size_t i = 0, e = SubLoops.size(); i != e; ++i) 79 delete SubLoops[i]; 80 } 81 82 /// getLoopDepth - Return the nesting level of this loop. An outer-most 83 /// loop has depth 1, for consistency with loop depth values used for basic 84 /// blocks, where depth 0 is used for blocks not inside any loops. 85 unsigned getLoopDepth() const { 86 unsigned D = 1; 87 for (const LoopT *CurLoop = ParentLoop; CurLoop; 88 CurLoop = CurLoop->ParentLoop) 89 ++D; 90 return D; 91 } 92 BlockT *getHeader() const { return Blocks.front(); } 93 LoopT *getParentLoop() const { return ParentLoop; } 94 95 /// contains - Return true if the specified basic block is in this loop 96 /// 97 bool contains(const BlockT *BB) const { 98 return std::find(block_begin(), block_end(), BB) != block_end(); 99 } 100 101 /// iterator/begin/end - Return the loops contained entirely within this loop. 102 /// 103 const std::vector<LoopT *> &getSubLoops() const { return SubLoops; } 104 typedef typename std::vector<LoopT *>::const_iterator iterator; 105 iterator begin() const { return SubLoops.begin(); } 106 iterator end() const { return SubLoops.end(); } 107 bool empty() const { return SubLoops.empty(); } 108 109 /// getBlocks - Get a list of the basic blocks which make up this loop. 110 /// 111 const std::vector<BlockT*> &getBlocks() const { return Blocks; } 112 typedef typename std::vector<BlockT*>::const_iterator block_iterator; 113 block_iterator block_begin() const { return Blocks.begin(); } 114 block_iterator block_end() const { return Blocks.end(); } 115 116 /// isLoopExit - True if terminator in the block can branch to another block 117 /// that is outside of the current loop. 118 /// 119 bool isLoopExit(const BlockT *BB) const { 120 typedef GraphTraits<BlockT*> BlockTraits; 121 for (typename BlockTraits::ChildIteratorType SI = 122 BlockTraits::child_begin(const_cast<BlockT*>(BB)), 123 SE = BlockTraits::child_end(const_cast<BlockT*>(BB)); SI != SE; ++SI) { 124 if (!contains(*SI)) 125 return true; 126 } 127 return false; 128 } 129 130 /// getNumBackEdges - Calculate the number of back edges to the loop header 131 /// 132 unsigned getNumBackEdges() const { 133 unsigned NumBackEdges = 0; 134 BlockT *H = getHeader(); 135 136 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 137 for (typename InvBlockTraits::ChildIteratorType I = 138 InvBlockTraits::child_begin(const_cast<BlockT*>(H)), 139 E = InvBlockTraits::child_end(const_cast<BlockT*>(H)); I != E; ++I) 140 if (contains(*I)) 141 ++NumBackEdges; 142 143 return NumBackEdges; 144 } 145 146 //===--------------------------------------------------------------------===// 147 // APIs for simple analysis of the loop. 148 // 149 // Note that all of these methods can fail on general loops (ie, there may not 150 // be a preheader, etc). For best success, the loop simplification and 151 // induction variable canonicalization pass should be used to normalize loops 152 // for easy analysis. These methods assume canonical loops. 153 154 /// getExitingBlocks - Return all blocks inside the loop that have successors 155 /// outside of the loop. These are the blocks _inside of the current loop_ 156 /// which branch out. The returned list is always unique. 157 /// 158 void getExitingBlocks(SmallVectorImpl<BlockT *> &ExitingBlocks) const { 159 // Sort the blocks vector so that we can use binary search to do quick 160 // lookups. 161 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 162 std::sort(LoopBBs.begin(), LoopBBs.end()); 163 164 typedef GraphTraits<BlockT*> BlockTraits; 165 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) 166 for (typename BlockTraits::ChildIteratorType I = 167 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 168 I != E; ++I) 169 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) { 170 // Not in current loop? It must be an exit block. 171 ExitingBlocks.push_back(*BI); 172 break; 173 } 174 } 175 176 /// getExitingBlock - If getExitingBlocks would return exactly one block, 177 /// return that block. Otherwise return null. 178 BlockT *getExitingBlock() const { 179 SmallVector<BlockT*, 8> ExitingBlocks; 180 getExitingBlocks(ExitingBlocks); 181 if (ExitingBlocks.size() == 1) 182 return ExitingBlocks[0]; 183 return 0; 184 } 185 186 /// getExitBlocks - Return all of the successor blocks of this loop. These 187 /// are the blocks _outside of the current loop_ which are branched to. 188 /// 189 void getExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const { 190 // Sort the blocks vector so that we can use binary search to do quick 191 // lookups. 192 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 193 std::sort(LoopBBs.begin(), LoopBBs.end()); 194 195 typedef GraphTraits<BlockT*> BlockTraits; 196 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) 197 for (typename BlockTraits::ChildIteratorType I = 198 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 199 I != E; ++I) 200 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) 201 // Not in current loop? It must be an exit block. 202 ExitBlocks.push_back(*I); 203 } 204 205 /// getExitBlock - If getExitBlocks would return exactly one block, 206 /// return that block. Otherwise return null. 207 BlockT *getExitBlock() const { 208 SmallVector<BlockT*, 8> ExitBlocks; 209 getExitBlocks(ExitBlocks); 210 if (ExitBlocks.size() == 1) 211 return ExitBlocks[0]; 212 return 0; 213 } 214 215 /// getExitEdges - Return all pairs of (_inside_block_,_outside_block_). 216 typedef std::pair<const BlockT*,const BlockT*> Edge; 217 void getExitEdges(SmallVectorImpl<Edge> &ExitEdges) const { 218 // Sort the blocks vector so that we can use binary search to do quick 219 // lookups. 220 SmallVector<BlockT*, 128> LoopBBs(block_begin(), block_end()); 221 std::sort(LoopBBs.begin(), LoopBBs.end()); 222 223 typedef GraphTraits<BlockT*> BlockTraits; 224 for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) 225 for (typename BlockTraits::ChildIteratorType I = 226 BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 227 I != E; ++I) 228 if (!std::binary_search(LoopBBs.begin(), LoopBBs.end(), *I)) 229 // Not in current loop? It must be an exit block. 230 ExitEdges.push_back(std::make_pair(*BI, *I)); 231 } 232 233 /// getLoopPreheader - If there is a preheader for this loop, return it. A 234 /// loop has a preheader if there is only one edge to the header of the loop 235 /// from outside of the loop. If this is the case, the block branching to the 236 /// header of the loop is the preheader node. 237 /// 238 /// This method returns null if there is no preheader for the loop. 239 /// 240 BlockT *getLoopPreheader() const { 241 // Keep track of nodes outside the loop branching to the header... 242 BlockT *Out = 0; 243 244 // Loop over the predecessors of the header node... 245 BlockT *Header = getHeader(); 246 typedef GraphTraits<BlockT*> BlockTraits; 247 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 248 for (typename InvBlockTraits::ChildIteratorType PI = 249 InvBlockTraits::child_begin(Header), 250 PE = InvBlockTraits::child_end(Header); PI != PE; ++PI) 251 if (!contains(*PI)) { // If the block is not in the loop... 252 if (Out && Out != *PI) 253 return 0; // Multiple predecessors outside the loop 254 Out = *PI; 255 } 256 257 // Make sure there is only one exit out of the preheader. 258 assert(Out && "Header of loop has no predecessors from outside loop?"); 259 typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out); 260 ++SI; 261 if (SI != BlockTraits::child_end(Out)) 262 return 0; // Multiple exits from the block, must not be a preheader. 263 264 // If there is exactly one preheader, return it. If there was zero, then 265 // Out is still null. 266 return Out; 267 } 268 269 /// getLoopLatch - If there is a single latch block for this loop, return it. 270 /// A latch block is a block that contains a branch back to the header. 271 /// A loop header in normal form has two edges into it: one from a preheader 272 /// and one from a latch block. 273 BlockT *getLoopLatch() const { 274 BlockT *Header = getHeader(); 275 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 276 typename InvBlockTraits::ChildIteratorType PI = 277 InvBlockTraits::child_begin(Header); 278 typename InvBlockTraits::ChildIteratorType PE = 279 InvBlockTraits::child_end(Header); 280 if (PI == PE) return 0; // no preds? 281 282 BlockT *Latch = 0; 283 if (contains(*PI)) 284 Latch = *PI; 285 ++PI; 286 if (PI == PE) return 0; // only one pred? 287 288 if (contains(*PI)) { 289 if (Latch) return 0; // multiple backedges 290 Latch = *PI; 291 } 292 ++PI; 293 if (PI != PE) return 0; // more than two preds 294 295 return Latch; 296 } 297 298 //===--------------------------------------------------------------------===// 299 // APIs for updating loop information after changing the CFG 300 // 301 302 /// addBasicBlockToLoop - This method is used by other analyses to update loop 303 /// information. NewBB is set to be a new member of the current loop. 304 /// Because of this, it is added as a member of all parent loops, and is added 305 /// to the specified LoopInfo object as being in the current basic block. It 306 /// is not valid to replace the loop header with this method. 307 /// 308 void addBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LI); 309 310 /// replaceChildLoopWith - This is used when splitting loops up. It replaces 311 /// the OldChild entry in our children list with NewChild, and updates the 312 /// parent pointer of OldChild to be null and the NewChild to be this loop. 313 /// This updates the loop depth of the new child. 314 void replaceChildLoopWith(LoopT *OldChild, 315 LoopT *NewChild) { 316 assert(OldChild->ParentLoop == this && "This loop is already broken!"); 317 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 318 typename std::vector<LoopT *>::iterator I = 319 std::find(SubLoops.begin(), SubLoops.end(), OldChild); 320 assert(I != SubLoops.end() && "OldChild not in loop!"); 321 *I = NewChild; 322 OldChild->ParentLoop = 0; 323 NewChild->ParentLoop = static_cast<LoopT *>(this); 324 } 325 326 /// addChildLoop - Add the specified loop to be a child of this loop. This 327 /// updates the loop depth of the new child. 328 /// 329 void addChildLoop(LoopT *NewChild) { 330 assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 331 NewChild->ParentLoop = static_cast<LoopT *>(this); 332 SubLoops.push_back(NewChild); 333 } 334 335 /// removeChildLoop - This removes the specified child from being a subloop of 336 /// this loop. The loop is not deleted, as it will presumably be inserted 337 /// into another loop. 338 LoopT *removeChildLoop(iterator I) { 339 assert(I != SubLoops.end() && "Cannot remove end iterator!"); 340 LoopT *Child = *I; 341 assert(Child->ParentLoop == this && "Child is not a child of this loop!"); 342 SubLoops.erase(SubLoops.begin()+(I-begin())); 343 Child->ParentLoop = 0; 344 return Child; 345 } 346 347 /// addBlockEntry - This adds a basic block directly to the basic block list. 348 /// This should only be used by transformations that create new loops. Other 349 /// transformations should use addBasicBlockToLoop. 350 void addBlockEntry(BlockT *BB) { 351 Blocks.push_back(BB); 352 } 353 354 /// moveToHeader - This method is used to move BB (which must be part of this 355 /// loop) to be the loop header of the loop (the block that dominates all 356 /// others). 357 void moveToHeader(BlockT *BB) { 358 if (Blocks[0] == BB) return; 359 for (unsigned i = 0; ; ++i) { 360 assert(i != Blocks.size() && "Loop does not contain BB!"); 361 if (Blocks[i] == BB) { 362 Blocks[i] = Blocks[0]; 363 Blocks[0] = BB; 364 return; 365 } 366 } 367 } 368 369 /// removeBlockFromLoop - This removes the specified basic block from the 370 /// current loop, updating the Blocks as appropriate. This does not update 371 /// the mapping in the LoopInfo class. 372 void removeBlockFromLoop(BlockT *BB) { 373 RemoveFromVector(Blocks, BB); 374 } 375 376 /// verifyLoop - Verify loop structure 377 void verifyLoop() const { 378#ifndef NDEBUG 379 assert(!Blocks.empty() && "Loop header is missing"); 380 assert(getHeader() && "Loop header is missing"); 381 382 // Verify the individual blocks. 383 for (block_iterator I = block_begin(), E = block_end(); I != E; ++I) { 384 BlockT *BB = *I; 385 bool HasInsideLoopSuccs = false; 386 bool HasInsideLoopPreds = false; 387 SmallVector<BlockT *, 2> OutsideLoopPreds; 388 389 typedef GraphTraits<BlockT*> BlockTraits; 390 for (typename BlockTraits::ChildIteratorType SI = 391 BlockTraits::child_begin(BB), SE = BlockTraits::child_end(BB); 392 SI != SE; ++SI) 393 if (contains(*SI)) 394 HasInsideLoopSuccs = true; 395 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 396 for (typename InvBlockTraits::ChildIteratorType PI = 397 InvBlockTraits::child_begin(BB), PE = InvBlockTraits::child_end(BB); 398 PI != PE; ++PI) { 399 if (contains(*PI)) 400 HasInsideLoopPreds = true; 401 else 402 OutsideLoopPreds.push_back(*PI); 403 } 404 405 if (BB == getHeader()) { 406 assert(!OutsideLoopPreds.empty() && "Loop is unreachable!"); 407 } else if (!OutsideLoopPreds.empty()) { 408 // A non-header loop shouldn't be reachable from outside the loop, 409 // though it is permitted if the predecessor is not itself actually 410 // reachable. 411 BlockT *EntryBB = BB->getParent()->begin(); 412 for (df_iterator<BlockT *> NI = df_begin(EntryBB), 413 NE = df_end(EntryBB); NI != NE; ++NI) 414 for (unsigned i = 0, e = OutsideLoopPreds.size(); i != e; ++i) 415 assert(*NI != OutsideLoopPreds[i] && 416 "Loop has multiple entry points!"); 417 } 418 assert(HasInsideLoopPreds && "Loop block has no in-loop predecessors!"); 419 assert(HasInsideLoopSuccs && "Loop block has no in-loop successors!"); 420 assert(BB != getHeader()->getParent()->begin() && 421 "Loop contains function entry block!"); 422 } 423 424 // Verify the subloops. 425 for (iterator I = begin(), E = end(); I != E; ++I) { 426 // Each block in each subloop should be contained within this loop. 427 for (block_iterator BI = (*I)->block_begin(), BE = (*I)->block_end(); 428 BI != BE; ++BI) { 429 assert(contains(*BI) && 430 "Loop does not contain all the blocks of a subloop!"); 431 } 432 // Recursively check the subloop. 433 (*I)->verifyLoop(); 434 } 435 436 // Verify the parent loop. 437 if (ParentLoop) { 438 bool FoundSelf = false; 439 for (iterator I = ParentLoop->begin(), E = ParentLoop->end(); I != E; ++I) 440 if (*I == this) { 441 FoundSelf = true; 442 break; 443 } 444 assert(FoundSelf && "Loop is not a subloop of its parent!"); 445 } 446#endif 447 } 448 449 void print(raw_ostream &OS, unsigned Depth = 0) const { 450 OS.indent(Depth*2) << "Loop at depth " << getLoopDepth() 451 << " containing: "; 452 453 for (unsigned i = 0; i < getBlocks().size(); ++i) { 454 if (i) OS << ","; 455 BlockT *BB = getBlocks()[i]; 456 WriteAsOperand(OS, BB, false); 457 if (BB == getHeader()) OS << "<header>"; 458 if (BB == getLoopLatch()) OS << "<latch>"; 459 if (isLoopExit(BB)) OS << "<exit>"; 460 } 461 OS << "\n"; 462 463 for (iterator I = begin(), E = end(); I != E; ++I) 464 (*I)->print(OS, Depth+2); 465 } 466 467 void dump() const { 468 print(errs()); 469 } 470 471protected: 472 friend class LoopInfoBase<BlockT, LoopT>; 473 explicit LoopBase(BlockT *BB) : ParentLoop(0) { 474 Blocks.push_back(BB); 475 } 476}; 477 478class Loop : public LoopBase<BasicBlock, Loop> { 479public: 480 Loop() {} 481 482 /// isLoopInvariant - Return true if the specified value is loop invariant 483 /// 484 bool isLoopInvariant(Value *V) const; 485 486 /// isLoopInvariant - Return true if the specified instruction is 487 /// loop-invariant. 488 /// 489 bool isLoopInvariant(Instruction *I) const; 490 491 /// makeLoopInvariant - If the given value is an instruction inside of the 492 /// loop and it can be hoisted, do so to make it trivially loop-invariant. 493 /// Return true if the value after any hoisting is loop invariant. This 494 /// function can be used as a slightly more aggressive replacement for 495 /// isLoopInvariant. 496 /// 497 /// If InsertPt is specified, it is the point to hoist instructions to. 498 /// If null, the terminator of the loop preheader is used. 499 /// 500 bool makeLoopInvariant(Value *V, bool &Changed, 501 Instruction *InsertPt = 0) const; 502 503 /// makeLoopInvariant - If the given instruction is inside of the 504 /// loop and it can be hoisted, do so to make it trivially loop-invariant. 505 /// Return true if the instruction after any hoisting is loop invariant. This 506 /// function can be used as a slightly more aggressive replacement for 507 /// isLoopInvariant. 508 /// 509 /// If InsertPt is specified, it is the point to hoist instructions to. 510 /// If null, the terminator of the loop preheader is used. 511 /// 512 bool makeLoopInvariant(Instruction *I, bool &Changed, 513 Instruction *InsertPt = 0) const; 514 515 /// getCanonicalInductionVariable - Check to see if the loop has a canonical 516 /// induction variable: an integer recurrence that starts at 0 and increments 517 /// by one each time through the loop. If so, return the phi node that 518 /// corresponds to it. 519 /// 520 /// The IndVarSimplify pass transforms loops to have a canonical induction 521 /// variable. 522 /// 523 PHINode *getCanonicalInductionVariable() const; 524 525 /// getCanonicalInductionVariableIncrement - Return the LLVM value that holds 526 /// the canonical induction variable value for the "next" iteration of the 527 /// loop. This always succeeds if getCanonicalInductionVariable succeeds. 528 /// 529 Instruction *getCanonicalInductionVariableIncrement() const; 530 531 /// getTripCount - Return a loop-invariant LLVM value indicating the number of 532 /// times the loop will be executed. Note that this means that the backedge 533 /// of the loop executes N-1 times. If the trip-count cannot be determined, 534 /// this returns null. 535 /// 536 /// The IndVarSimplify pass transforms loops to have a form that this 537 /// function easily understands. 538 /// 539 Value *getTripCount() const; 540 541 /// getSmallConstantTripCount - Returns the trip count of this loop as a 542 /// normal unsigned value, if possible. Returns 0 if the trip count is unknown 543 /// of not constant. Will also return 0 if the trip count is very large 544 /// (>= 2^32) 545 unsigned getSmallConstantTripCount() const; 546 547 /// getSmallConstantTripMultiple - Returns the largest constant divisor of the 548 /// trip count of this loop as a normal unsigned value, if possible. This 549 /// means that the actual trip count is always a multiple of the returned 550 /// value (don't forget the trip count could very well be zero as well!). 551 /// 552 /// Returns 1 if the trip count is unknown or not guaranteed to be the 553 /// multiple of a constant (which is also the case if the trip count is simply 554 /// constant, use getSmallConstantTripCount for that case), Will also return 1 555 /// if the trip count is very large (>= 2^32). 556 unsigned getSmallConstantTripMultiple() const; 557 558 /// isLCSSAForm - Return true if the Loop is in LCSSA form 559 bool isLCSSAForm() const; 560 561 /// isLoopSimplifyForm - Return true if the Loop is in the form that 562 /// the LoopSimplify form transforms loops to, which is sometimes called 563 /// normal form. 564 bool isLoopSimplifyForm() const; 565 566 /// getUniqueExitBlocks - Return all unique successor blocks of this loop. 567 /// These are the blocks _outside of the current loop_ which are branched to. 568 /// This assumes that loop is in canonical form. 569 /// 570 void getUniqueExitBlocks(SmallVectorImpl<BasicBlock *> &ExitBlocks) const; 571 572 /// getUniqueExitBlock - If getUniqueExitBlocks would return exactly one 573 /// block, return that block. Otherwise return null. 574 BasicBlock *getUniqueExitBlock() const; 575 576private: 577 friend class LoopInfoBase<BasicBlock, Loop>; 578 explicit Loop(BasicBlock *BB) : LoopBase<BasicBlock, Loop>(BB) {} 579}; 580 581//===----------------------------------------------------------------------===// 582/// LoopInfo - This class builds and contains all of the top level loop 583/// structures in the specified function. 584/// 585 586template<class BlockT, class LoopT> 587class LoopInfoBase { 588 // BBMap - Mapping of basic blocks to the inner most loop they occur in 589 std::map<BlockT *, LoopT *> BBMap; 590 std::vector<LoopT *> TopLevelLoops; 591 friend class LoopBase<BlockT, LoopT>; 592 593 void operator=(const LoopInfoBase &); // do not implement 594 LoopInfoBase(const LoopInfo &); // do not implement 595public: 596 LoopInfoBase() { } 597 ~LoopInfoBase() { releaseMemory(); } 598 599 void releaseMemory() { 600 for (typename std::vector<LoopT *>::iterator I = 601 TopLevelLoops.begin(), E = TopLevelLoops.end(); I != E; ++I) 602 delete *I; // Delete all of the loops... 603 604 BBMap.clear(); // Reset internal state of analysis 605 TopLevelLoops.clear(); 606 } 607 608 /// iterator/begin/end - The interface to the top-level loops in the current 609 /// function. 610 /// 611 typedef typename std::vector<LoopT *>::const_iterator iterator; 612 iterator begin() const { return TopLevelLoops.begin(); } 613 iterator end() const { return TopLevelLoops.end(); } 614 bool empty() const { return TopLevelLoops.empty(); } 615 616 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 617 /// block is in no loop (for example the entry node), null is returned. 618 /// 619 LoopT *getLoopFor(const BlockT *BB) const { 620 typename std::map<BlockT *, LoopT *>::const_iterator I= 621 BBMap.find(const_cast<BlockT*>(BB)); 622 return I != BBMap.end() ? I->second : 0; 623 } 624 625 /// operator[] - same as getLoopFor... 626 /// 627 const LoopT *operator[](const BlockT *BB) const { 628 return getLoopFor(BB); 629 } 630 631 /// getLoopDepth - Return the loop nesting level of the specified block. A 632 /// depth of 0 means the block is not inside any loop. 633 /// 634 unsigned getLoopDepth(const BlockT *BB) const { 635 const LoopT *L = getLoopFor(BB); 636 return L ? L->getLoopDepth() : 0; 637 } 638 639 // isLoopHeader - True if the block is a loop header node 640 bool isLoopHeader(BlockT *BB) const { 641 const LoopT *L = getLoopFor(BB); 642 return L && L->getHeader() == BB; 643 } 644 645 /// removeLoop - This removes the specified top-level loop from this loop info 646 /// object. The loop is not deleted, as it will presumably be inserted into 647 /// another loop. 648 LoopT *removeLoop(iterator I) { 649 assert(I != end() && "Cannot remove end iterator!"); 650 LoopT *L = *I; 651 assert(L->getParentLoop() == 0 && "Not a top-level loop!"); 652 TopLevelLoops.erase(TopLevelLoops.begin() + (I-begin())); 653 return L; 654 } 655 656 /// changeLoopFor - Change the top-level loop that contains BB to the 657 /// specified loop. This should be used by transformations that restructure 658 /// the loop hierarchy tree. 659 void changeLoopFor(BlockT *BB, LoopT *L) { 660 LoopT *&OldLoop = BBMap[BB]; 661 assert(OldLoop && "Block not in a loop yet!"); 662 OldLoop = L; 663 } 664 665 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 666 /// list with the indicated loop. 667 void changeTopLevelLoop(LoopT *OldLoop, 668 LoopT *NewLoop) { 669 typename std::vector<LoopT *>::iterator I = 670 std::find(TopLevelLoops.begin(), TopLevelLoops.end(), OldLoop); 671 assert(I != TopLevelLoops.end() && "Old loop not at top level!"); 672 *I = NewLoop; 673 assert(NewLoop->ParentLoop == 0 && OldLoop->ParentLoop == 0 && 674 "Loops already embedded into a subloop!"); 675 } 676 677 /// addTopLevelLoop - This adds the specified loop to the collection of 678 /// top-level loops. 679 void addTopLevelLoop(LoopT *New) { 680 assert(New->getParentLoop() == 0 && "Loop already in subloop!"); 681 TopLevelLoops.push_back(New); 682 } 683 684 /// removeBlock - This method completely removes BB from all data structures, 685 /// including all of the Loop objects it is nested in and our mapping from 686 /// BasicBlocks to loops. 687 void removeBlock(BlockT *BB) { 688 typename std::map<BlockT *, LoopT *>::iterator I = BBMap.find(BB); 689 if (I != BBMap.end()) { 690 for (LoopT *L = I->second; L; L = L->getParentLoop()) 691 L->removeBlockFromLoop(BB); 692 693 BBMap.erase(I); 694 } 695 } 696 697 // Internals 698 699 static bool isNotAlreadyContainedIn(const LoopT *SubLoop, 700 const LoopT *ParentLoop) { 701 if (SubLoop == 0) return true; 702 if (SubLoop == ParentLoop) return false; 703 return isNotAlreadyContainedIn(SubLoop->getParentLoop(), ParentLoop); 704 } 705 706 void Calculate(DominatorTreeBase<BlockT> &DT) { 707 BlockT *RootNode = DT.getRootNode()->getBlock(); 708 709 for (df_iterator<BlockT*> NI = df_begin(RootNode), 710 NE = df_end(RootNode); NI != NE; ++NI) 711 if (LoopT *L = ConsiderForLoop(*NI, DT)) 712 TopLevelLoops.push_back(L); 713 } 714 715 LoopT *ConsiderForLoop(BlockT *BB, DominatorTreeBase<BlockT> &DT) { 716 if (BBMap.find(BB) != BBMap.end()) return 0;// Haven't processed this node? 717 718 std::vector<BlockT *> TodoStack; 719 720 // Scan the predecessors of BB, checking to see if BB dominates any of 721 // them. This identifies backedges which target this node... 722 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 723 for (typename InvBlockTraits::ChildIteratorType I = 724 InvBlockTraits::child_begin(BB), E = InvBlockTraits::child_end(BB); 725 I != E; ++I) 726 if (DT.dominates(BB, *I)) // If BB dominates it's predecessor... 727 TodoStack.push_back(*I); 728 729 if (TodoStack.empty()) return 0; // No backedges to this block... 730 731 // Create a new loop to represent this basic block... 732 LoopT *L = new LoopT(BB); 733 BBMap[BB] = L; 734 735 BlockT *EntryBlock = BB->getParent()->begin(); 736 737 while (!TodoStack.empty()) { // Process all the nodes in the loop 738 BlockT *X = TodoStack.back(); 739 TodoStack.pop_back(); 740 741 if (!L->contains(X) && // As of yet unprocessed?? 742 DT.dominates(EntryBlock, X)) { // X is reachable from entry block? 743 // Check to see if this block already belongs to a loop. If this occurs 744 // then we have a case where a loop that is supposed to be a child of 745 // the current loop was processed before the current loop. When this 746 // occurs, this child loop gets added to a part of the current loop, 747 // making it a sibling to the current loop. We have to reparent this 748 // loop. 749 if (LoopT *SubLoop = 750 const_cast<LoopT *>(getLoopFor(X))) 751 if (SubLoop->getHeader() == X && isNotAlreadyContainedIn(SubLoop, L)){ 752 // Remove the subloop from it's current parent... 753 assert(SubLoop->ParentLoop && SubLoop->ParentLoop != L); 754 LoopT *SLP = SubLoop->ParentLoop; // SubLoopParent 755 typename std::vector<LoopT *>::iterator I = 756 std::find(SLP->SubLoops.begin(), SLP->SubLoops.end(), SubLoop); 757 assert(I != SLP->SubLoops.end() &&"SubLoop not a child of parent?"); 758 SLP->SubLoops.erase(I); // Remove from parent... 759 760 // Add the subloop to THIS loop... 761 SubLoop->ParentLoop = L; 762 L->SubLoops.push_back(SubLoop); 763 } 764 765 // Normal case, add the block to our loop... 766 L->Blocks.push_back(X); 767 768 typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 769 770 // Add all of the predecessors of X to the end of the work stack... 771 TodoStack.insert(TodoStack.end(), InvBlockTraits::child_begin(X), 772 InvBlockTraits::child_end(X)); 773 } 774 } 775 776 // If there are any loops nested within this loop, create them now! 777 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 778 E = L->Blocks.end(); I != E; ++I) 779 if (LoopT *NewLoop = ConsiderForLoop(*I, DT)) { 780 L->SubLoops.push_back(NewLoop); 781 NewLoop->ParentLoop = L; 782 } 783 784 // Add the basic blocks that comprise this loop to the BBMap so that this 785 // loop can be found for them. 786 // 787 for (typename std::vector<BlockT*>::iterator I = L->Blocks.begin(), 788 E = L->Blocks.end(); I != E; ++I) 789 BBMap.insert(std::make_pair(*I, L)); 790 791 // Now that we have a list of all of the child loops of this loop, check to 792 // see if any of them should actually be nested inside of each other. We 793 // can accidentally pull loops our of their parents, so we must make sure to 794 // organize the loop nests correctly now. 795 { 796 std::map<BlockT *, LoopT *> ContainingLoops; 797 for (unsigned i = 0; i != L->SubLoops.size(); ++i) { 798 LoopT *Child = L->SubLoops[i]; 799 assert(Child->getParentLoop() == L && "Not proper child loop?"); 800 801 if (LoopT *ContainingLoop = ContainingLoops[Child->getHeader()]) { 802 // If there is already a loop which contains this loop, move this loop 803 // into the containing loop. 804 MoveSiblingLoopInto(Child, ContainingLoop); 805 --i; // The loop got removed from the SubLoops list. 806 } else { 807 // This is currently considered to be a top-level loop. Check to see 808 // if any of the contained blocks are loop headers for subloops we 809 // have already processed. 810 for (unsigned b = 0, e = Child->Blocks.size(); b != e; ++b) { 811 LoopT *&BlockLoop = ContainingLoops[Child->Blocks[b]]; 812 if (BlockLoop == 0) { // Child block not processed yet... 813 BlockLoop = Child; 814 } else if (BlockLoop != Child) { 815 LoopT *SubLoop = BlockLoop; 816 // Reparent all of the blocks which used to belong to BlockLoops 817 for (unsigned j = 0, e = SubLoop->Blocks.size(); j != e; ++j) 818 ContainingLoops[SubLoop->Blocks[j]] = Child; 819 820 // There is already a loop which contains this block, that means 821 // that we should reparent the loop which the block is currently 822 // considered to belong to to be a child of this loop. 823 MoveSiblingLoopInto(SubLoop, Child); 824 --i; // We just shrunk the SubLoops list. 825 } 826 } 827 } 828 } 829 } 830 831 return L; 832 } 833 834 /// MoveSiblingLoopInto - This method moves the NewChild loop to live inside 835 /// of the NewParent Loop, instead of being a sibling of it. 836 void MoveSiblingLoopInto(LoopT *NewChild, 837 LoopT *NewParent) { 838 LoopT *OldParent = NewChild->getParentLoop(); 839 assert(OldParent && OldParent == NewParent->getParentLoop() && 840 NewChild != NewParent && "Not sibling loops!"); 841 842 // Remove NewChild from being a child of OldParent 843 typename std::vector<LoopT *>::iterator I = 844 std::find(OldParent->SubLoops.begin(), OldParent->SubLoops.end(), 845 NewChild); 846 assert(I != OldParent->SubLoops.end() && "Parent fields incorrect??"); 847 OldParent->SubLoops.erase(I); // Remove from parent's subloops list 848 NewChild->ParentLoop = 0; 849 850 InsertLoopInto(NewChild, NewParent); 851 } 852 853 /// InsertLoopInto - This inserts loop L into the specified parent loop. If 854 /// the parent loop contains a loop which should contain L, the loop gets 855 /// inserted into L instead. 856 void InsertLoopInto(LoopT *L, LoopT *Parent) { 857 BlockT *LHeader = L->getHeader(); 858 assert(Parent->contains(LHeader) && 859 "This loop should not be inserted here!"); 860 861 // Check to see if it belongs in a child loop... 862 for (unsigned i = 0, e = static_cast<unsigned>(Parent->SubLoops.size()); 863 i != e; ++i) 864 if (Parent->SubLoops[i]->contains(LHeader)) { 865 InsertLoopInto(L, Parent->SubLoops[i]); 866 return; 867 } 868 869 // If not, insert it here! 870 Parent->SubLoops.push_back(L); 871 L->ParentLoop = Parent; 872 } 873 874 // Debugging 875 876 void print(raw_ostream &OS) const { 877 for (unsigned i = 0; i < TopLevelLoops.size(); ++i) 878 TopLevelLoops[i]->print(OS); 879 #if 0 880 for (std::map<BasicBlock*, LoopT*>::const_iterator I = BBMap.begin(), 881 E = BBMap.end(); I != E; ++I) 882 OS << "BB '" << I->first->getName() << "' level = " 883 << I->second->getLoopDepth() << "\n"; 884 #endif 885 } 886}; 887 888class LoopInfo : public FunctionPass { 889 LoopInfoBase<BasicBlock, Loop> LI; 890 friend class LoopBase<BasicBlock, Loop>; 891 892 void operator=(const LoopInfo &); // do not implement 893 LoopInfo(const LoopInfo &); // do not implement 894public: 895 static char ID; // Pass identification, replacement for typeid 896 897 LoopInfo() : FunctionPass(&ID) {} 898 899 LoopInfoBase<BasicBlock, Loop>& getBase() { return LI; } 900 901 /// iterator/begin/end - The interface to the top-level loops in the current 902 /// function. 903 /// 904 typedef LoopInfoBase<BasicBlock, Loop>::iterator iterator; 905 inline iterator begin() const { return LI.begin(); } 906 inline iterator end() const { return LI.end(); } 907 bool empty() const { return LI.empty(); } 908 909 /// getLoopFor - Return the inner most loop that BB lives in. If a basic 910 /// block is in no loop (for example the entry node), null is returned. 911 /// 912 inline Loop *getLoopFor(const BasicBlock *BB) const { 913 return LI.getLoopFor(BB); 914 } 915 916 /// operator[] - same as getLoopFor... 917 /// 918 inline const Loop *operator[](const BasicBlock *BB) const { 919 return LI.getLoopFor(BB); 920 } 921 922 /// getLoopDepth - Return the loop nesting level of the specified block. A 923 /// depth of 0 means the block is not inside any loop. 924 /// 925 inline unsigned getLoopDepth(const BasicBlock *BB) const { 926 return LI.getLoopDepth(BB); 927 } 928 929 // isLoopHeader - True if the block is a loop header node 930 inline bool isLoopHeader(BasicBlock *BB) const { 931 return LI.isLoopHeader(BB); 932 } 933 934 /// runOnFunction - Calculate the natural loop information. 935 /// 936 virtual bool runOnFunction(Function &F); 937 938 virtual void verifyAnalysis() const; 939 940 virtual void releaseMemory() { LI.releaseMemory(); } 941 942 virtual void print(raw_ostream &O, const Module* M = 0) const; 943 944 virtual void getAnalysisUsage(AnalysisUsage &AU) const; 945 946 /// removeLoop - This removes the specified top-level loop from this loop info 947 /// object. The loop is not deleted, as it will presumably be inserted into 948 /// another loop. 949 inline Loop *removeLoop(iterator I) { return LI.removeLoop(I); } 950 951 /// changeLoopFor - Change the top-level loop that contains BB to the 952 /// specified loop. This should be used by transformations that restructure 953 /// the loop hierarchy tree. 954 inline void changeLoopFor(BasicBlock *BB, Loop *L) { 955 LI.changeLoopFor(BB, L); 956 } 957 958 /// changeTopLevelLoop - Replace the specified loop in the top-level loops 959 /// list with the indicated loop. 960 inline void changeTopLevelLoop(Loop *OldLoop, Loop *NewLoop) { 961 LI.changeTopLevelLoop(OldLoop, NewLoop); 962 } 963 964 /// addTopLevelLoop - This adds the specified loop to the collection of 965 /// top-level loops. 966 inline void addTopLevelLoop(Loop *New) { 967 LI.addTopLevelLoop(New); 968 } 969 970 /// removeBlock - This method completely removes BB from all data structures, 971 /// including all of the Loop objects it is nested in and our mapping from 972 /// BasicBlocks to loops. 973 void removeBlock(BasicBlock *BB) { 974 LI.removeBlock(BB); 975 } 976 977 static bool isNotAlreadyContainedIn(const Loop *SubLoop, 978 const Loop *ParentLoop) { 979 return 980 LoopInfoBase<BasicBlock, Loop>::isNotAlreadyContainedIn(SubLoop, 981 ParentLoop); 982 } 983}; 984 985 986// Allow clients to walk the list of nested loops... 987template <> struct GraphTraits<const Loop*> { 988 typedef const Loop NodeType; 989 typedef LoopInfo::iterator ChildIteratorType; 990 991 static NodeType *getEntryNode(const Loop *L) { return L; } 992 static inline ChildIteratorType child_begin(NodeType *N) { 993 return N->begin(); 994 } 995 static inline ChildIteratorType child_end(NodeType *N) { 996 return N->end(); 997 } 998}; 999 1000template <> struct GraphTraits<Loop*> { 1001 typedef Loop NodeType; 1002 typedef LoopInfo::iterator ChildIteratorType; 1003 1004 static NodeType *getEntryNode(Loop *L) { return L; } 1005 static inline ChildIteratorType child_begin(NodeType *N) { 1006 return N->begin(); 1007 } 1008 static inline ChildIteratorType child_end(NodeType *N) { 1009 return N->end(); 1010 } 1011}; 1012 1013template<class BlockT, class LoopT> 1014void 1015LoopBase<BlockT, LoopT>::addBasicBlockToLoop(BlockT *NewBB, 1016 LoopInfoBase<BlockT, LoopT> &LIB) { 1017 assert((Blocks.empty() || LIB[getHeader()] == this) && 1018 "Incorrect LI specified for this loop!"); 1019 assert(NewBB && "Cannot add a null basic block to the loop!"); 1020 assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!"); 1021 1022 LoopT *L = static_cast<LoopT *>(this); 1023 1024 // Add the loop mapping to the LoopInfo object... 1025 LIB.BBMap[NewBB] = L; 1026 1027 // Add the basic block to this loop and all parent loops... 1028 while (L) { 1029 L->Blocks.push_back(NewBB); 1030 L = L->getParentLoop(); 1031 } 1032} 1033 1034} // End llvm namespace 1035 1036#endif 1037