1239310Sdim//===- llvm/Analysis/LoopInfoImpl.h - Natural Loop Calculator ---*- C++ -*-===// 2239310Sdim// 3239310Sdim// The LLVM Compiler Infrastructure 4239310Sdim// 5239310Sdim// This file is distributed under the University of Illinois Open Source 6239310Sdim// License. See LICENSE.TXT for details. 7239310Sdim// 8239310Sdim//===----------------------------------------------------------------------===// 9239310Sdim// 10239310Sdim// This is the generic implementation of LoopInfo used for both Loops and 11239310Sdim// MachineLoops. 12239310Sdim// 13239310Sdim//===----------------------------------------------------------------------===// 14239310Sdim 15249423Sdim#ifndef LLVM_ANALYSIS_LOOPINFOIMPL_H 16249423Sdim#define LLVM_ANALYSIS_LOOPINFOIMPL_H 17239310Sdim 18249423Sdim#include "llvm/ADT/PostOrderIterator.h" 19249423Sdim#include "llvm/ADT/STLExtras.h" 20239310Sdim#include "llvm/Analysis/LoopInfo.h" 21239310Sdim 22239310Sdimnamespace llvm { 23239310Sdim 24239310Sdim//===----------------------------------------------------------------------===// 25239310Sdim// APIs for simple analysis of the loop. See header notes. 26239310Sdim 27239310Sdim/// getExitingBlocks - Return all blocks inside the loop that have successors 28239310Sdim/// outside of the loop. These are the blocks _inside of the current loop_ 29239310Sdim/// which branch out. The returned list is always unique. 30239310Sdim/// 31239310Sdimtemplate<class BlockT, class LoopT> 32239310Sdimvoid LoopBase<BlockT, LoopT>:: 33239310SdimgetExitingBlocks(SmallVectorImpl<BlockT *> &ExitingBlocks) const { 34239310Sdim typedef GraphTraits<BlockT*> BlockTraits; 35239310Sdim for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) 36239310Sdim for (typename BlockTraits::ChildIteratorType I = 37239310Sdim BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 38239310Sdim I != E; ++I) 39263508Sdim if (!contains(*I)) { 40239310Sdim // Not in current loop? It must be an exit block. 41239310Sdim ExitingBlocks.push_back(*BI); 42239310Sdim break; 43239310Sdim } 44239310Sdim} 45239310Sdim 46239310Sdim/// getExitingBlock - If getExitingBlocks would return exactly one block, 47239310Sdim/// return that block. Otherwise return null. 48239310Sdimtemplate<class BlockT, class LoopT> 49239310SdimBlockT *LoopBase<BlockT, LoopT>::getExitingBlock() const { 50239310Sdim SmallVector<BlockT*, 8> ExitingBlocks; 51239310Sdim getExitingBlocks(ExitingBlocks); 52239310Sdim if (ExitingBlocks.size() == 1) 53239310Sdim return ExitingBlocks[0]; 54239310Sdim return 0; 55239310Sdim} 56239310Sdim 57239310Sdim/// getExitBlocks - Return all of the successor blocks of this loop. These 58239310Sdim/// are the blocks _outside of the current loop_ which are branched to. 59239310Sdim/// 60239310Sdimtemplate<class BlockT, class LoopT> 61239310Sdimvoid LoopBase<BlockT, LoopT>:: 62239310SdimgetExitBlocks(SmallVectorImpl<BlockT*> &ExitBlocks) const { 63239310Sdim typedef GraphTraits<BlockT*> BlockTraits; 64239310Sdim for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) 65239310Sdim for (typename BlockTraits::ChildIteratorType I = 66239310Sdim BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 67239310Sdim I != E; ++I) 68263508Sdim if (!contains(*I)) 69239310Sdim // Not in current loop? It must be an exit block. 70239310Sdim ExitBlocks.push_back(*I); 71239310Sdim} 72239310Sdim 73239310Sdim/// getExitBlock - If getExitBlocks would return exactly one block, 74239310Sdim/// return that block. Otherwise return null. 75239310Sdimtemplate<class BlockT, class LoopT> 76239310SdimBlockT *LoopBase<BlockT, LoopT>::getExitBlock() const { 77239310Sdim SmallVector<BlockT*, 8> ExitBlocks; 78239310Sdim getExitBlocks(ExitBlocks); 79239310Sdim if (ExitBlocks.size() == 1) 80239310Sdim return ExitBlocks[0]; 81239310Sdim return 0; 82239310Sdim} 83239310Sdim 84239310Sdim/// getExitEdges - Return all pairs of (_inside_block_,_outside_block_). 85239310Sdimtemplate<class BlockT, class LoopT> 86239310Sdimvoid LoopBase<BlockT, LoopT>:: 87239310SdimgetExitEdges(SmallVectorImpl<Edge> &ExitEdges) const { 88239310Sdim typedef GraphTraits<BlockT*> BlockTraits; 89239310Sdim for (block_iterator BI = block_begin(), BE = block_end(); BI != BE; ++BI) 90239310Sdim for (typename BlockTraits::ChildIteratorType I = 91239310Sdim BlockTraits::child_begin(*BI), E = BlockTraits::child_end(*BI); 92239310Sdim I != E; ++I) 93263508Sdim if (!contains(*I)) 94239310Sdim // Not in current loop? It must be an exit block. 95239310Sdim ExitEdges.push_back(Edge(*BI, *I)); 96239310Sdim} 97239310Sdim 98239310Sdim/// getLoopPreheader - If there is a preheader for this loop, return it. A 99239310Sdim/// loop has a preheader if there is only one edge to the header of the loop 100239310Sdim/// from outside of the loop. If this is the case, the block branching to the 101239310Sdim/// header of the loop is the preheader node. 102239310Sdim/// 103239310Sdim/// This method returns null if there is no preheader for the loop. 104239310Sdim/// 105239310Sdimtemplate<class BlockT, class LoopT> 106239310SdimBlockT *LoopBase<BlockT, LoopT>::getLoopPreheader() const { 107239310Sdim // Keep track of nodes outside the loop branching to the header... 108239310Sdim BlockT *Out = getLoopPredecessor(); 109239310Sdim if (!Out) return 0; 110239310Sdim 111239310Sdim // Make sure there is only one exit out of the preheader. 112239310Sdim typedef GraphTraits<BlockT*> BlockTraits; 113239310Sdim typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out); 114239310Sdim ++SI; 115239310Sdim if (SI != BlockTraits::child_end(Out)) 116239310Sdim return 0; // Multiple exits from the block, must not be a preheader. 117239310Sdim 118239310Sdim // The predecessor has exactly one successor, so it is a preheader. 119239310Sdim return Out; 120239310Sdim} 121239310Sdim 122239310Sdim/// getLoopPredecessor - If the given loop's header has exactly one unique 123239310Sdim/// predecessor outside the loop, return it. Otherwise return null. 124239310Sdim/// This is less strict that the loop "preheader" concept, which requires 125239310Sdim/// the predecessor to have exactly one successor. 126239310Sdim/// 127239310Sdimtemplate<class BlockT, class LoopT> 128239310SdimBlockT *LoopBase<BlockT, LoopT>::getLoopPredecessor() const { 129239310Sdim // Keep track of nodes outside the loop branching to the header... 130239310Sdim BlockT *Out = 0; 131239310Sdim 132239310Sdim // Loop over the predecessors of the header node... 133239310Sdim BlockT *Header = getHeader(); 134239310Sdim typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 135239310Sdim for (typename InvBlockTraits::ChildIteratorType PI = 136239310Sdim InvBlockTraits::child_begin(Header), 137239310Sdim PE = InvBlockTraits::child_end(Header); PI != PE; ++PI) { 138239310Sdim typename InvBlockTraits::NodeType *N = *PI; 139239310Sdim if (!contains(N)) { // If the block is not in the loop... 140239310Sdim if (Out && Out != N) 141239310Sdim return 0; // Multiple predecessors outside the loop 142239310Sdim Out = N; 143239310Sdim } 144239310Sdim } 145239310Sdim 146239310Sdim // Make sure there is only one exit out of the preheader. 147239310Sdim assert(Out && "Header of loop has no predecessors from outside loop?"); 148239310Sdim return Out; 149239310Sdim} 150239310Sdim 151239310Sdim/// getLoopLatch - If there is a single latch block for this loop, return it. 152239310Sdim/// A latch block is a block that contains a branch back to the header. 153239310Sdimtemplate<class BlockT, class LoopT> 154239310SdimBlockT *LoopBase<BlockT, LoopT>::getLoopLatch() const { 155239310Sdim BlockT *Header = getHeader(); 156239310Sdim typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 157239310Sdim typename InvBlockTraits::ChildIteratorType PI = 158239310Sdim InvBlockTraits::child_begin(Header); 159239310Sdim typename InvBlockTraits::ChildIteratorType PE = 160239310Sdim InvBlockTraits::child_end(Header); 161239310Sdim BlockT *Latch = 0; 162239310Sdim for (; PI != PE; ++PI) { 163239310Sdim typename InvBlockTraits::NodeType *N = *PI; 164239310Sdim if (contains(N)) { 165239310Sdim if (Latch) return 0; 166239310Sdim Latch = N; 167239310Sdim } 168239310Sdim } 169239310Sdim 170239310Sdim return Latch; 171239310Sdim} 172239310Sdim 173239310Sdim//===----------------------------------------------------------------------===// 174239310Sdim// APIs for updating loop information after changing the CFG 175239310Sdim// 176239310Sdim 177239310Sdim/// addBasicBlockToLoop - This method is used by other analyses to update loop 178239310Sdim/// information. NewBB is set to be a new member of the current loop. 179239310Sdim/// Because of this, it is added as a member of all parent loops, and is added 180239310Sdim/// to the specified LoopInfo object as being in the current basic block. It 181239310Sdim/// is not valid to replace the loop header with this method. 182239310Sdim/// 183239310Sdimtemplate<class BlockT, class LoopT> 184239310Sdimvoid LoopBase<BlockT, LoopT>:: 185239310SdimaddBasicBlockToLoop(BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LIB) { 186239310Sdim assert((Blocks.empty() || LIB[getHeader()] == this) && 187239310Sdim "Incorrect LI specified for this loop!"); 188239310Sdim assert(NewBB && "Cannot add a null basic block to the loop!"); 189239310Sdim assert(LIB[NewBB] == 0 && "BasicBlock already in the loop!"); 190239310Sdim 191239310Sdim LoopT *L = static_cast<LoopT *>(this); 192239310Sdim 193239310Sdim // Add the loop mapping to the LoopInfo object... 194239310Sdim LIB.BBMap[NewBB] = L; 195239310Sdim 196239310Sdim // Add the basic block to this loop and all parent loops... 197239310Sdim while (L) { 198263508Sdim L->addBlockEntry(NewBB); 199239310Sdim L = L->getParentLoop(); 200239310Sdim } 201239310Sdim} 202239310Sdim 203239310Sdim/// replaceChildLoopWith - This is used when splitting loops up. It replaces 204239310Sdim/// the OldChild entry in our children list with NewChild, and updates the 205239310Sdim/// parent pointer of OldChild to be null and the NewChild to be this loop. 206239310Sdim/// This updates the loop depth of the new child. 207239310Sdimtemplate<class BlockT, class LoopT> 208239310Sdimvoid LoopBase<BlockT, LoopT>:: 209239310SdimreplaceChildLoopWith(LoopT *OldChild, LoopT *NewChild) { 210239310Sdim assert(OldChild->ParentLoop == this && "This loop is already broken!"); 211239310Sdim assert(NewChild->ParentLoop == 0 && "NewChild already has a parent!"); 212239310Sdim typename std::vector<LoopT *>::iterator I = 213239310Sdim std::find(SubLoops.begin(), SubLoops.end(), OldChild); 214239310Sdim assert(I != SubLoops.end() && "OldChild not in loop!"); 215239310Sdim *I = NewChild; 216239310Sdim OldChild->ParentLoop = 0; 217239310Sdim NewChild->ParentLoop = static_cast<LoopT *>(this); 218239310Sdim} 219239310Sdim 220239310Sdim/// verifyLoop - Verify loop structure 221239310Sdimtemplate<class BlockT, class LoopT> 222239310Sdimvoid LoopBase<BlockT, LoopT>::verifyLoop() const { 223239310Sdim#ifndef NDEBUG 224239310Sdim assert(!Blocks.empty() && "Loop header is missing"); 225239310Sdim 226239310Sdim // Setup for using a depth-first iterator to visit every block in the loop. 227239310Sdim SmallVector<BlockT*, 8> ExitBBs; 228239310Sdim getExitBlocks(ExitBBs); 229239310Sdim llvm::SmallPtrSet<BlockT*, 8> VisitSet; 230239310Sdim VisitSet.insert(ExitBBs.begin(), ExitBBs.end()); 231239310Sdim df_ext_iterator<BlockT*, llvm::SmallPtrSet<BlockT*, 8> > 232239310Sdim BI = df_ext_begin(getHeader(), VisitSet), 233239310Sdim BE = df_ext_end(getHeader(), VisitSet); 234239310Sdim 235239310Sdim // Keep track of the number of BBs visited. 236239310Sdim unsigned NumVisited = 0; 237239310Sdim 238239310Sdim // Check the individual blocks. 239239310Sdim for ( ; BI != BE; ++BI) { 240239310Sdim BlockT *BB = *BI; 241239310Sdim bool HasInsideLoopSuccs = false; 242239310Sdim bool HasInsideLoopPreds = false; 243239310Sdim SmallVector<BlockT *, 2> OutsideLoopPreds; 244239310Sdim 245239310Sdim typedef GraphTraits<BlockT*> BlockTraits; 246239310Sdim for (typename BlockTraits::ChildIteratorType SI = 247239310Sdim BlockTraits::child_begin(BB), SE = BlockTraits::child_end(BB); 248239310Sdim SI != SE; ++SI) 249263508Sdim if (contains(*SI)) { 250239310Sdim HasInsideLoopSuccs = true; 251239310Sdim break; 252239310Sdim } 253239310Sdim typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 254239310Sdim for (typename InvBlockTraits::ChildIteratorType PI = 255239310Sdim InvBlockTraits::child_begin(BB), PE = InvBlockTraits::child_end(BB); 256239310Sdim PI != PE; ++PI) { 257239310Sdim BlockT *N = *PI; 258263508Sdim if (contains(N)) 259239310Sdim HasInsideLoopPreds = true; 260239310Sdim else 261239310Sdim OutsideLoopPreds.push_back(N); 262239310Sdim } 263239310Sdim 264239310Sdim if (BB == getHeader()) { 265239310Sdim assert(!OutsideLoopPreds.empty() && "Loop is unreachable!"); 266239310Sdim } else if (!OutsideLoopPreds.empty()) { 267239310Sdim // A non-header loop shouldn't be reachable from outside the loop, 268239310Sdim // though it is permitted if the predecessor is not itself actually 269239310Sdim // reachable. 270239310Sdim BlockT *EntryBB = BB->getParent()->begin(); 271239310Sdim for (df_iterator<BlockT *> NI = df_begin(EntryBB), 272239310Sdim NE = df_end(EntryBB); NI != NE; ++NI) 273239310Sdim for (unsigned i = 0, e = OutsideLoopPreds.size(); i != e; ++i) 274239310Sdim assert(*NI != OutsideLoopPreds[i] && 275239310Sdim "Loop has multiple entry points!"); 276239310Sdim } 277239310Sdim assert(HasInsideLoopPreds && "Loop block has no in-loop predecessors!"); 278239310Sdim assert(HasInsideLoopSuccs && "Loop block has no in-loop successors!"); 279239310Sdim assert(BB != getHeader()->getParent()->begin() && 280239310Sdim "Loop contains function entry block!"); 281239310Sdim 282239310Sdim NumVisited++; 283239310Sdim } 284239310Sdim 285239310Sdim assert(NumVisited == getNumBlocks() && "Unreachable block in loop"); 286239310Sdim 287239310Sdim // Check the subloops. 288239310Sdim for (iterator I = begin(), E = end(); I != E; ++I) 289239310Sdim // Each block in each subloop should be contained within this loop. 290239310Sdim for (block_iterator BI = (*I)->block_begin(), BE = (*I)->block_end(); 291239310Sdim BI != BE; ++BI) { 292263508Sdim assert(contains(*BI) && 293239310Sdim "Loop does not contain all the blocks of a subloop!"); 294239310Sdim } 295239310Sdim 296239310Sdim // Check the parent loop pointer. 297239310Sdim if (ParentLoop) { 298239310Sdim assert(std::find(ParentLoop->begin(), ParentLoop->end(), this) != 299239310Sdim ParentLoop->end() && 300239310Sdim "Loop is not a subloop of its parent!"); 301239310Sdim } 302239310Sdim#endif 303239310Sdim} 304239310Sdim 305239310Sdim/// verifyLoop - Verify loop structure of this loop and all nested loops. 306239310Sdimtemplate<class BlockT, class LoopT> 307239310Sdimvoid LoopBase<BlockT, LoopT>::verifyLoopNest( 308239310Sdim DenseSet<const LoopT*> *Loops) const { 309239310Sdim Loops->insert(static_cast<const LoopT *>(this)); 310239310Sdim // Verify this loop. 311239310Sdim verifyLoop(); 312239310Sdim // Verify the subloops. 313239310Sdim for (iterator I = begin(), E = end(); I != E; ++I) 314239310Sdim (*I)->verifyLoopNest(Loops); 315239310Sdim} 316239310Sdim 317239310Sdimtemplate<class BlockT, class LoopT> 318239310Sdimvoid LoopBase<BlockT, LoopT>::print(raw_ostream &OS, unsigned Depth) const { 319239310Sdim OS.indent(Depth*2) << "Loop at depth " << getLoopDepth() 320239310Sdim << " containing: "; 321239310Sdim 322239310Sdim for (unsigned i = 0; i < getBlocks().size(); ++i) { 323239310Sdim if (i) OS << ","; 324239310Sdim BlockT *BB = getBlocks()[i]; 325239310Sdim WriteAsOperand(OS, BB, false); 326239310Sdim if (BB == getHeader()) OS << "<header>"; 327239310Sdim if (BB == getLoopLatch()) OS << "<latch>"; 328239310Sdim if (isLoopExiting(BB)) OS << "<exiting>"; 329239310Sdim } 330239310Sdim OS << "\n"; 331239310Sdim 332239310Sdim for (iterator I = begin(), E = end(); I != E; ++I) 333239310Sdim (*I)->print(OS, Depth+2); 334239310Sdim} 335239310Sdim 336239310Sdim//===----------------------------------------------------------------------===// 337239310Sdim/// Stable LoopInfo Analysis - Build a loop tree using stable iterators so the 338239310Sdim/// result does / not depend on use list (block predecessor) order. 339239310Sdim/// 340239310Sdim 341239310Sdim/// Discover a subloop with the specified backedges such that: All blocks within 342239310Sdim/// this loop are mapped to this loop or a subloop. And all subloops within this 343239310Sdim/// loop have their parent loop set to this loop or a subloop. 344239310Sdimtemplate<class BlockT, class LoopT> 345239310Sdimstatic void discoverAndMapSubloop(LoopT *L, ArrayRef<BlockT*> Backedges, 346239310Sdim LoopInfoBase<BlockT, LoopT> *LI, 347239310Sdim DominatorTreeBase<BlockT> &DomTree) { 348239310Sdim typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 349239310Sdim 350239310Sdim unsigned NumBlocks = 0; 351239310Sdim unsigned NumSubloops = 0; 352239310Sdim 353239310Sdim // Perform a backward CFG traversal using a worklist. 354239310Sdim std::vector<BlockT *> ReverseCFGWorklist(Backedges.begin(), Backedges.end()); 355239310Sdim while (!ReverseCFGWorklist.empty()) { 356239310Sdim BlockT *PredBB = ReverseCFGWorklist.back(); 357239310Sdim ReverseCFGWorklist.pop_back(); 358239310Sdim 359239310Sdim LoopT *Subloop = LI->getLoopFor(PredBB); 360239310Sdim if (!Subloop) { 361239310Sdim if (!DomTree.isReachableFromEntry(PredBB)) 362239310Sdim continue; 363239310Sdim 364239310Sdim // This is an undiscovered block. Map it to the current loop. 365239310Sdim LI->changeLoopFor(PredBB, L); 366239310Sdim ++NumBlocks; 367239310Sdim if (PredBB == L->getHeader()) 368239310Sdim continue; 369239310Sdim // Push all block predecessors on the worklist. 370239310Sdim ReverseCFGWorklist.insert(ReverseCFGWorklist.end(), 371239310Sdim InvBlockTraits::child_begin(PredBB), 372239310Sdim InvBlockTraits::child_end(PredBB)); 373239310Sdim } 374239310Sdim else { 375239310Sdim // This is a discovered block. Find its outermost discovered loop. 376239310Sdim while (LoopT *Parent = Subloop->getParentLoop()) 377239310Sdim Subloop = Parent; 378239310Sdim 379239310Sdim // If it is already discovered to be a subloop of this loop, continue. 380239310Sdim if (Subloop == L) 381239310Sdim continue; 382239310Sdim 383239310Sdim // Discover a subloop of this loop. 384239310Sdim Subloop->setParentLoop(L); 385239310Sdim ++NumSubloops; 386239310Sdim NumBlocks += Subloop->getBlocks().capacity(); 387239310Sdim PredBB = Subloop->getHeader(); 388239310Sdim // Continue traversal along predecessors that are not loop-back edges from 389239310Sdim // within this subloop tree itself. Note that a predecessor may directly 390239310Sdim // reach another subloop that is not yet discovered to be a subloop of 391239310Sdim // this loop, which we must traverse. 392239310Sdim for (typename InvBlockTraits::ChildIteratorType PI = 393239310Sdim InvBlockTraits::child_begin(PredBB), 394239310Sdim PE = InvBlockTraits::child_end(PredBB); PI != PE; ++PI) { 395239310Sdim if (LI->getLoopFor(*PI) != Subloop) 396239310Sdim ReverseCFGWorklist.push_back(*PI); 397239310Sdim } 398239310Sdim } 399239310Sdim } 400239310Sdim L->getSubLoopsVector().reserve(NumSubloops); 401263508Sdim L->reserveBlocks(NumBlocks); 402239310Sdim} 403239310Sdim 404239310Sdimnamespace { 405239310Sdim/// Populate all loop data in a stable order during a single forward DFS. 406239310Sdimtemplate<class BlockT, class LoopT> 407239310Sdimclass PopulateLoopsDFS { 408239310Sdim typedef GraphTraits<BlockT*> BlockTraits; 409239310Sdim typedef typename BlockTraits::ChildIteratorType SuccIterTy; 410239310Sdim 411239310Sdim LoopInfoBase<BlockT, LoopT> *LI; 412239310Sdim DenseSet<const BlockT *> VisitedBlocks; 413239310Sdim std::vector<std::pair<BlockT*, SuccIterTy> > DFSStack; 414239310Sdim 415239310Sdimpublic: 416239310Sdim PopulateLoopsDFS(LoopInfoBase<BlockT, LoopT> *li): 417239310Sdim LI(li) {} 418239310Sdim 419239310Sdim void traverse(BlockT *EntryBlock); 420239310Sdim 421239310Sdimprotected: 422239310Sdim void insertIntoLoop(BlockT *Block); 423239310Sdim 424239310Sdim BlockT *dfsSource() { return DFSStack.back().first; } 425239310Sdim SuccIterTy &dfsSucc() { return DFSStack.back().second; } 426239310Sdim SuccIterTy dfsSuccEnd() { return BlockTraits::child_end(dfsSource()); } 427239310Sdim 428239310Sdim void pushBlock(BlockT *Block) { 429239310Sdim DFSStack.push_back(std::make_pair(Block, BlockTraits::child_begin(Block))); 430239310Sdim } 431239310Sdim}; 432239310Sdim} // anonymous 433239310Sdim 434239310Sdim/// Top-level driver for the forward DFS within the loop. 435239310Sdimtemplate<class BlockT, class LoopT> 436239310Sdimvoid PopulateLoopsDFS<BlockT, LoopT>::traverse(BlockT *EntryBlock) { 437239310Sdim pushBlock(EntryBlock); 438239310Sdim VisitedBlocks.insert(EntryBlock); 439239310Sdim while (!DFSStack.empty()) { 440239310Sdim // Traverse the leftmost path as far as possible. 441239310Sdim while (dfsSucc() != dfsSuccEnd()) { 442239310Sdim BlockT *BB = *dfsSucc(); 443239310Sdim ++dfsSucc(); 444239310Sdim if (!VisitedBlocks.insert(BB).second) 445239310Sdim continue; 446239310Sdim 447239310Sdim // Push the next DFS successor onto the stack. 448239310Sdim pushBlock(BB); 449239310Sdim } 450239310Sdim // Visit the top of the stack in postorder and backtrack. 451239310Sdim insertIntoLoop(dfsSource()); 452239310Sdim DFSStack.pop_back(); 453239310Sdim } 454239310Sdim} 455239310Sdim 456239310Sdim/// Add a single Block to its ancestor loops in PostOrder. If the block is a 457239310Sdim/// subloop header, add the subloop to its parent in PostOrder, then reverse the 458239310Sdim/// Block and Subloop vectors of the now complete subloop to achieve RPO. 459239310Sdimtemplate<class BlockT, class LoopT> 460239310Sdimvoid PopulateLoopsDFS<BlockT, LoopT>::insertIntoLoop(BlockT *Block) { 461239310Sdim LoopT *Subloop = LI->getLoopFor(Block); 462239310Sdim if (Subloop && Block == Subloop->getHeader()) { 463239310Sdim // We reach this point once per subloop after processing all the blocks in 464239310Sdim // the subloop. 465239310Sdim if (Subloop->getParentLoop()) 466239310Sdim Subloop->getParentLoop()->getSubLoopsVector().push_back(Subloop); 467239310Sdim else 468239310Sdim LI->addTopLevelLoop(Subloop); 469239310Sdim 470239310Sdim // For convenience, Blocks and Subloops are inserted in postorder. Reverse 471239310Sdim // the lists, except for the loop header, which is always at the beginning. 472263508Sdim Subloop->reverseBlock(1); 473239310Sdim std::reverse(Subloop->getSubLoopsVector().begin(), 474239310Sdim Subloop->getSubLoopsVector().end()); 475239310Sdim 476239310Sdim Subloop = Subloop->getParentLoop(); 477239310Sdim } 478239310Sdim for (; Subloop; Subloop = Subloop->getParentLoop()) 479263508Sdim Subloop->addBlockEntry(Block); 480239310Sdim} 481239310Sdim 482239310Sdim/// Analyze LoopInfo discovers loops during a postorder DominatorTree traversal 483239310Sdim/// interleaved with backward CFG traversals within each subloop 484239310Sdim/// (discoverAndMapSubloop). The backward traversal skips inner subloops, so 485239310Sdim/// this part of the algorithm is linear in the number of CFG edges. Subloop and 486239310Sdim/// Block vectors are then populated during a single forward CFG traversal 487239310Sdim/// (PopulateLoopDFS). 488239310Sdim/// 489239310Sdim/// During the two CFG traversals each block is seen three times: 490239310Sdim/// 1) Discovered and mapped by a reverse CFG traversal. 491239310Sdim/// 2) Visited during a forward DFS CFG traversal. 492239310Sdim/// 3) Reverse-inserted in the loop in postorder following forward DFS. 493239310Sdim/// 494239310Sdim/// The Block vectors are inclusive, so step 3 requires loop-depth number of 495239310Sdim/// insertions per block. 496239310Sdimtemplate<class BlockT, class LoopT> 497239310Sdimvoid LoopInfoBase<BlockT, LoopT>:: 498239310SdimAnalyze(DominatorTreeBase<BlockT> &DomTree) { 499239310Sdim 500239310Sdim // Postorder traversal of the dominator tree. 501239310Sdim DomTreeNodeBase<BlockT>* DomRoot = DomTree.getRootNode(); 502239310Sdim for (po_iterator<DomTreeNodeBase<BlockT>*> DomIter = po_begin(DomRoot), 503239310Sdim DomEnd = po_end(DomRoot); DomIter != DomEnd; ++DomIter) { 504239310Sdim 505239310Sdim BlockT *Header = DomIter->getBlock(); 506239310Sdim SmallVector<BlockT *, 4> Backedges; 507239310Sdim 508239310Sdim // Check each predecessor of the potential loop header. 509239310Sdim typedef GraphTraits<Inverse<BlockT*> > InvBlockTraits; 510239310Sdim for (typename InvBlockTraits::ChildIteratorType PI = 511239310Sdim InvBlockTraits::child_begin(Header), 512239310Sdim PE = InvBlockTraits::child_end(Header); PI != PE; ++PI) { 513239310Sdim 514239310Sdim BlockT *Backedge = *PI; 515239310Sdim 516239310Sdim // If Header dominates predBB, this is a new loop. Collect the backedges. 517239310Sdim if (DomTree.dominates(Header, Backedge) 518239310Sdim && DomTree.isReachableFromEntry(Backedge)) { 519239310Sdim Backedges.push_back(Backedge); 520239310Sdim } 521239310Sdim } 522239310Sdim // Perform a backward CFG traversal to discover and map blocks in this loop. 523239310Sdim if (!Backedges.empty()) { 524239310Sdim LoopT *L = new LoopT(Header); 525239310Sdim discoverAndMapSubloop(L, ArrayRef<BlockT*>(Backedges), this, DomTree); 526239310Sdim } 527239310Sdim } 528239310Sdim // Perform a single forward CFG traversal to populate block and subloop 529239310Sdim // vectors for all loops. 530239310Sdim PopulateLoopsDFS<BlockT, LoopT> DFS(this); 531239310Sdim DFS.traverse(DomRoot->getBlock()); 532239310Sdim} 533239310Sdim 534239310Sdim// Debugging 535239310Sdimtemplate<class BlockT, class LoopT> 536239310Sdimvoid LoopInfoBase<BlockT, LoopT>::print(raw_ostream &OS) const { 537239310Sdim for (unsigned i = 0; i < TopLevelLoops.size(); ++i) 538239310Sdim TopLevelLoops[i]->print(OS); 539239310Sdim#if 0 540239310Sdim for (DenseMap<BasicBlock*, LoopT*>::const_iterator I = BBMap.begin(), 541239310Sdim E = BBMap.end(); I != E; ++I) 542239310Sdim OS << "BB '" << I->first->getName() << "' level = " 543239310Sdim << I->second->getLoopDepth() << "\n"; 544239310Sdim#endif 545239310Sdim} 546239310Sdim 547239310Sdim} // End llvm namespace 548239310Sdim 549239310Sdim#endif 550