LCOV - code coverage report
Current view: top level - include/llvm/Analysis - LoopInfoImpl.h (source / functions) Hit Total Coverage
Test: llvm-toolchain.info Lines: 177 179 98.9 %
Date: 2018-10-16 05:50:02 Functions: 46 59 78.0 %
Legend: Lines: hit not hit

          Line data    Source code
       1             : //===- llvm/Analysis/LoopInfoImpl.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 is the generic implementation of LoopInfo used for both Loops and
      11             : // MachineLoops.
      12             : //
      13             : //===----------------------------------------------------------------------===//
      14             : 
      15             : #ifndef LLVM_ANALYSIS_LOOPINFOIMPL_H
      16             : #define LLVM_ANALYSIS_LOOPINFOIMPL_H
      17             : 
      18             : #include "llvm/ADT/DepthFirstIterator.h"
      19             : #include "llvm/ADT/PostOrderIterator.h"
      20             : #include "llvm/ADT/STLExtras.h"
      21             : #include "llvm/ADT/SetVector.h"
      22             : #include "llvm/Analysis/LoopInfo.h"
      23             : #include "llvm/IR/Dominators.h"
      24             : 
      25             : namespace llvm {
      26             : 
      27             : //===----------------------------------------------------------------------===//
      28             : // APIs for simple analysis of the loop. See header notes.
      29             : 
      30             : /// getExitingBlocks - Return all blocks inside the loop that have successors
      31             : /// outside of the loop.  These are the blocks _inside of the current loop_
      32             : /// which branch out.  The returned list is always unique.
      33             : ///
      34             : template <class BlockT, class LoopT>
      35      504249 : void LoopBase<BlockT, LoopT>::getExitingBlocks(
      36             :     SmallVectorImpl<BlockT *> &ExitingBlocks) const {
      37             :   assert(!isInvalid() && "Loop not in a valid state!");
      38     3444328 :   for (const auto BB : blocks())
      39     9168111 :     for (const auto &Succ : children<BlockT *>(BB))
      40     4449614 :       if (!contains(Succ)) {
      41             :         // Not in current loop? It must be an exit block.
      42     1076175 :         ExitingBlocks.push_back(BB);
      43     1076175 :         break;
      44             :       }
      45      504249 : }
      46             : 
      47             : /// getExitingBlock - If getExitingBlocks would return exactly one block,
      48             : /// return that block. Otherwise return null.
      49             : template <class BlockT, class LoopT>
      50      129752 : BlockT *LoopBase<BlockT, LoopT>::getExitingBlock() const {
      51             :   assert(!isInvalid() && "Loop not in a valid state!");
      52             :   SmallVector<BlockT *, 8> ExitingBlocks;
      53      129752 :   getExitingBlocks(ExitingBlocks);
      54      129752 :   if (ExitingBlocks.size() == 1)
      55       90413 :     return ExitingBlocks[0];
      56             :   return nullptr;
      57             : }
      58             : 
      59             : /// getExitBlocks - Return all of the successor blocks of this loop.  These
      60             : /// are the blocks _outside of the current loop_ which are branched to.
      61             : ///
      62             : template <class BlockT, class LoopT>
      63      270459 : void LoopBase<BlockT, LoopT>::getExitBlocks(
      64             :     SmallVectorImpl<BlockT *> &ExitBlocks) const {
      65             :   assert(!isInvalid() && "Loop not in a valid state!");
      66     2294538 :   for (const auto BB : blocks())
      67    10705469 :     for (const auto &Succ : children<BlockT *>(BB))
      68     3433013 :       if (!contains(Succ))
      69             :         // Not in current loop? It must be an exit block.
      70      808880 :         ExitBlocks.push_back(Succ);
      71      270459 : }
      72             : 
      73             : /// getExitBlock - If getExitBlocks would return exactly one block,
      74             : /// return that block. Otherwise return null.
      75             : template <class BlockT, class LoopT>
      76        7642 : BlockT *LoopBase<BlockT, LoopT>::getExitBlock() const {
      77             :   assert(!isInvalid() && "Loop not in a valid state!");
      78             :   SmallVector<BlockT *, 8> ExitBlocks;
      79        7642 :   getExitBlocks(ExitBlocks);
      80        7642 :   if (ExitBlocks.size() == 1)
      81        5062 :     return ExitBlocks[0];
      82             :   return nullptr;
      83             : }
      84             : 
      85             : template <class BlockT, class LoopT>
      86      127170 : bool LoopBase<BlockT, LoopT>::hasDedicatedExits() const {
      87             :   // Each predecessor of each exit block of a normal loop is contained
      88             :   // within the loop.
      89             :   SmallVector<BlockT *, 4> ExitBlocks;
      90      127170 :   getExitBlocks(ExitBlocks);
      91      518900 :   for (BlockT *EB : ExitBlocks)
      92     2098170 :     for (BlockT *Predecessor : children<Inverse<BlockT *>>(EB))
      93     1706440 :       if (!contains(Predecessor))
      94          59 :         return false;
      95             :   // All the requirements are met.
      96             :   return true;
      97             : }
      98             : 
      99             : template <class BlockT, class LoopT>
     100       35516 : void LoopBase<BlockT, LoopT>::getUniqueExitBlocks(
     101             :     SmallVectorImpl<BlockT *> &ExitBlocks) const {
     102             :   typedef GraphTraits<BlockT *> BlockTraits;
     103             :   typedef GraphTraits<Inverse<BlockT *>> InvBlockTraits;
     104             : 
     105             :   assert(hasDedicatedExits() &&
     106             :          "getUniqueExitBlocks assumes the loop has canonical form exits!");
     107             : 
     108             :   SmallVector<BlockT *, 32> SwitchExitBlocks;
     109      247915 :   for (BlockT *Block : this->blocks()) {
     110             :     SwitchExitBlocks.clear();
     111     1155792 :     for (BlockT *Successor : children<BlockT *>(Block)) {
     112             :       // If block is inside the loop then it is not an exit block.
     113      365497 :       if (contains(Successor))
     114             :         continue;
     115             : 
     116       90835 :       BlockT *FirstPred = *InvBlockTraits::child_begin(Successor);
     117             : 
     118             :       // If current basic block is this exit block's first predecessor then only
     119             :       // insert exit block in to the output ExitBlocks vector. This ensures that
     120             :       // same exit block is not inserted twice into ExitBlocks vector.
     121       90835 :       if (Block != FirstPred)
     122             :         continue;
     123             : 
     124             :       // If a terminator has more then two successors, for example SwitchInst,
     125             :       // then it is possible that there are multiple edges from current block to
     126             :       // one exit block.
     127       77944 :       if (std::distance(BlockTraits::child_begin(Block),
     128             :                         BlockTraits::child_end(Block)) <= 2) {
     129       76468 :         ExitBlocks.push_back(Successor);
     130       76468 :         continue;
     131             :       }
     132             : 
     133             :       // In case of multiple edges from current block to exit block, collect
     134             :       // only one edge in ExitBlocks. Use switchExitBlocks to keep track of
     135             :       // duplicate edges.
     136        1476 :       if (!is_contained(SwitchExitBlocks, Successor)) {
     137        1081 :         SwitchExitBlocks.push_back(Successor);
     138        1081 :         ExitBlocks.push_back(Successor);
     139             :       }
     140             :     }
     141             :   }
     142       35516 : }
     143             : 
     144             : template <class BlockT, class LoopT>
     145        8880 : BlockT *LoopBase<BlockT, LoopT>::getUniqueExitBlock() const {
     146             :   SmallVector<BlockT *, 8> UniqueExitBlocks;
     147        8880 :   getUniqueExitBlocks(UniqueExitBlocks);
     148        8880 :   if (UniqueExitBlocks.size() == 1)
     149        7117 :     return UniqueExitBlocks[0];
     150             :   return nullptr;
     151             : }
     152             : 
     153             : /// getExitEdges - Return all pairs of (_inside_block_,_outside_block_).
     154             : template <class BlockT, class LoopT>
     155          48 : void LoopBase<BlockT, LoopT>::getExitEdges(
     156             :     SmallVectorImpl<Edge> &ExitEdges) const {
     157             :   assert(!isInvalid() && "Loop not in a valid state!");
     158         118 :   for (const auto BB : blocks())
     159         404 :     for (const auto &Succ : children<BlockT *>(BB))
     160         132 :       if (!contains(Succ))
     161             :         // Not in current loop? It must be an exit block.
     162          54 :         ExitEdges.emplace_back(BB, Succ);
     163          48 : }
     164             : 
     165             : /// getLoopPreheader - If there is a preheader for this loop, return it.  A
     166             : /// loop has a preheader if there is only one edge to the header of the loop
     167             : /// from outside of the loop and it is legal to hoist instructions into the
     168             : /// predecessor. If this is the case, the block branching to the header of the
     169             : /// loop is the preheader node.
     170             : ///
     171             : /// This method returns null if there is no preheader for the loop.
     172             : ///
     173             : template <class BlockT, class LoopT>
     174      339992 : BlockT *LoopBase<BlockT, LoopT>::getLoopPreheader() const {
     175             :   assert(!isInvalid() && "Loop not in a valid state!");
     176             :   // Keep track of nodes outside the loop branching to the header...
     177      339992 :   BlockT *Out = getLoopPredecessor();
     178      339992 :   if (!Out)
     179             :     return nullptr;
     180             : 
     181             :   // Make sure we are allowed to hoist instructions into the predecessor.
     182      339691 :   if (!Out->isLegalToHoistInto())
     183             :     return nullptr;
     184             : 
     185             :   // Make sure there is only one exit out of the preheader.
     186             :   typedef GraphTraits<BlockT *> BlockTraits;
     187             :   typename BlockTraits::ChildIteratorType SI = BlockTraits::child_begin(Out);
     188           1 :   ++SI;
     189      339643 :   if (SI != BlockTraits::child_end(Out))
     190        8724 :     return nullptr; // Multiple exits from the block, must not be a preheader.
     191             : 
     192             :   // The predecessor has exactly one successor, so it is a preheader.
     193             :   return Out;
     194             : }
     195             : 
     196             : /// getLoopPredecessor - If the given loop's header has exactly one unique
     197             : /// predecessor outside the loop, return it. Otherwise return null.
     198             : /// This is less strict that the loop "preheader" concept, which requires
     199             : /// the predecessor to have exactly one successor.
     200             : ///
     201             : template <class BlockT, class LoopT>
     202      388318 : BlockT *LoopBase<BlockT, LoopT>::getLoopPredecessor() const {
     203             :   assert(!isInvalid() && "Loop not in a valid state!");
     204             :   // Keep track of nodes outside the loop branching to the header...
     205             :   BlockT *Out = nullptr;
     206             : 
     207             :   // Loop over the predecessors of the header node...
     208             :   BlockT *Header = getHeader();
     209     1160015 :   for (const auto Pred : children<Inverse<BlockT *>>(Header)) {
     210      772137 :     if (!contains(Pred)) { // If the block is not in the loop...
     211      388762 :       if (Out && Out != Pred)
     212         237 :         return nullptr; // Multiple predecessors outside the loop
     213             :       Out = Pred;
     214             :     }
     215             :   }
     216             : 
     217             :   // Make sure there is only one exit out of the preheader.
     218             :   assert(Out && "Header of loop has no predecessors from outside loop?");
     219      363138 :   return Out;
     220             : }
     221             : 
     222             : /// getLoopLatch - If there is a single latch block for this loop, return it.
     223             : /// A latch block is a block that contains a branch back to the header.
     224             : template <class BlockT, class LoopT>
     225      515018 : BlockT *LoopBase<BlockT, LoopT>::getLoopLatch() const {
     226             :   assert(!isInvalid() && "Loop not in a valid state!");
     227             :   BlockT *Header = getHeader();
     228             :   BlockT *Latch = nullptr;
     229     1543752 :   for (const auto Pred : children<Inverse<BlockT *>>(Header)) {
     230     1029745 :     if (contains(Pred)) {
     231      515134 :       if (Latch)
     232        1007 :         return nullptr;
     233             :       Latch = Pred;
     234             :     }
     235             :   }
     236             : 
     237      510999 :   return Latch;
     238             : }
     239             : 
     240             : //===----------------------------------------------------------------------===//
     241             : // APIs for updating loop information after changing the CFG
     242             : //
     243             : 
     244             : /// addBasicBlockToLoop - This method is used by other analyses to update loop
     245             : /// information.  NewBB is set to be a new member of the current loop.
     246             : /// Because of this, it is added as a member of all parent loops, and is added
     247             : /// to the specified LoopInfo object as being in the current basic block.  It
     248             : /// is not valid to replace the loop header with this method.
     249             : ///
     250             : template <class BlockT, class LoopT>
     251       31307 : void LoopBase<BlockT, LoopT>::addBasicBlockToLoop(
     252             :     BlockT *NewBB, LoopInfoBase<BlockT, LoopT> &LIB) {
     253             :   assert(!isInvalid() && "Loop not in a valid state!");
     254             : #ifndef NDEBUG
     255             :   if (!Blocks.empty()) {
     256             :     auto SameHeader = LIB[getHeader()];
     257             :     assert(contains(SameHeader) && getHeader() == SameHeader->getHeader() &&
     258             :            "Incorrect LI specified for this loop!");
     259             :   }
     260             : #endif
     261             :   assert(NewBB && "Cannot add a null basic block to the loop!");
     262             :   assert(!LIB[NewBB] && "BasicBlock already in the loop!");
     263             : 
     264             :   LoopT *L = static_cast<LoopT *>(this);
     265             : 
     266             :   // Add the loop mapping to the LoopInfo object...
     267       31307 :   LIB.BBMap[NewBB] = L;
     268             : 
     269             :   // Add the basic block to this loop and all parent loops...
     270       67558 :   while (L) {
     271       36251 :     L->addBlockEntry(NewBB);
     272             :     L = L->getParentLoop();
     273             :   }
     274       31307 : }
     275             : 
     276             : /// replaceChildLoopWith - This is used when splitting loops up.  It replaces
     277             : /// the OldChild entry in our children list with NewChild, and updates the
     278             : /// parent pointer of OldChild to be null and the NewChild to be this loop.
     279             : /// This updates the loop depth of the new child.
     280             : template <class BlockT, class LoopT>
     281           6 : void LoopBase<BlockT, LoopT>::replaceChildLoopWith(LoopT *OldChild,
     282             :                                                    LoopT *NewChild) {
     283             :   assert(!isInvalid() && "Loop not in a valid state!");
     284             :   assert(OldChild->ParentLoop == this && "This loop is already broken!");
     285             :   assert(!NewChild->ParentLoop && "NewChild already has a parent!");
     286             :   typename std::vector<LoopT *>::iterator I = find(SubLoops, OldChild);
     287             :   assert(I != SubLoops.end() && "OldChild not in loop!");
     288           6 :   *I = NewChild;
     289           6 :   OldChild->ParentLoop = nullptr;
     290           6 :   NewChild->ParentLoop = static_cast<LoopT *>(this);
     291           6 : }
     292             : 
     293             : /// verifyLoop - Verify loop structure
     294             : template <class BlockT, class LoopT>
     295       73692 : void LoopBase<BlockT, LoopT>::verifyLoop() const {
     296             :   assert(!isInvalid() && "Loop not in a valid state!");
     297             : #ifndef NDEBUG
     298             :   assert(!Blocks.empty() && "Loop header is missing");
     299             : 
     300             :   // Setup for using a depth-first iterator to visit every block in the loop.
     301             :   SmallVector<BlockT *, 8> ExitBBs;
     302             :   getExitBlocks(ExitBBs);
     303             :   df_iterator_default_set<BlockT *> VisitSet;
     304             :   VisitSet.insert(ExitBBs.begin(), ExitBBs.end());
     305             :   df_ext_iterator<BlockT *, df_iterator_default_set<BlockT *>>
     306             :       BI = df_ext_begin(getHeader(), VisitSet),
     307             :       BE = df_ext_end(getHeader(), VisitSet);
     308             : 
     309             :   // Keep track of the BBs visited.
     310             :   SmallPtrSet<BlockT *, 8> VisitedBBs;
     311             : 
     312             :   // Check the individual blocks.
     313             :   for (; BI != BE; ++BI) {
     314             :     BlockT *BB = *BI;
     315             : 
     316             :     assert(std::any_of(GraphTraits<BlockT *>::child_begin(BB),
     317             :                        GraphTraits<BlockT *>::child_end(BB),
     318             :                        [&](BlockT *B) { return contains(B); }) &&
     319             :            "Loop block has no in-loop successors!");
     320             : 
     321             :     assert(std::any_of(GraphTraits<Inverse<BlockT *>>::child_begin(BB),
     322             :                        GraphTraits<Inverse<BlockT *>>::child_end(BB),
     323             :                        [&](BlockT *B) { return contains(B); }) &&
     324             :            "Loop block has no in-loop predecessors!");
     325             : 
     326             :     SmallVector<BlockT *, 2> OutsideLoopPreds;
     327             :     std::for_each(GraphTraits<Inverse<BlockT *>>::child_begin(BB),
     328             :                   GraphTraits<Inverse<BlockT *>>::child_end(BB),
     329             :                   [&](BlockT *B) {
     330             :                     if (!contains(B))
     331             :                       OutsideLoopPreds.push_back(B);
     332             :                   });
     333             : 
     334             :     if (BB == getHeader()) {
     335             :       assert(!OutsideLoopPreds.empty() && "Loop is unreachable!");
     336             :     } else if (!OutsideLoopPreds.empty()) {
     337             :       // A non-header loop shouldn't be reachable from outside the loop,
     338             :       // though it is permitted if the predecessor is not itself actually
     339             :       // reachable.
     340             :       BlockT *EntryBB = &BB->getParent()->front();
     341             :       for (BlockT *CB : depth_first(EntryBB))
     342             :         for (unsigned i = 0, e = OutsideLoopPreds.size(); i != e; ++i)
     343             :           assert(CB != OutsideLoopPreds[i] &&
     344             :                  "Loop has multiple entry points!");
     345             :     }
     346             :     assert(BB != &getHeader()->getParent()->front() &&
     347             :            "Loop contains function entry block!");
     348             : 
     349             :     VisitedBBs.insert(BB);
     350             :   }
     351             : 
     352             :   if (VisitedBBs.size() != getNumBlocks()) {
     353             :     dbgs() << "The following blocks are unreachable in the loop: ";
     354             :     for (auto BB : Blocks) {
     355             :       if (!VisitedBBs.count(BB)) {
     356             :         dbgs() << *BB << "\n";
     357             :       }
     358             :     }
     359             :     assert(false && "Unreachable block in loop");
     360             :   }
     361             : 
     362             :   // Check the subloops.
     363             :   for (iterator I = begin(), E = end(); I != E; ++I)
     364             :     // Each block in each subloop should be contained within this loop.
     365             :     for (block_iterator BI = (*I)->block_begin(), BE = (*I)->block_end();
     366             :          BI != BE; ++BI) {
     367             :       assert(contains(*BI) &&
     368             :              "Loop does not contain all the blocks of a subloop!");
     369             :     }
     370             : 
     371             :   // Check the parent loop pointer.
     372             :   if (ParentLoop) {
     373             :     assert(is_contained(*ParentLoop, this) &&
     374             :            "Loop is not a subloop of its parent!");
     375             :   }
     376             : #endif
     377       73692 : }
     378             : 
     379             : /// verifyLoop - Verify loop structure of this loop and all nested loops.
     380             : template <class BlockT, class LoopT>
     381         217 : void LoopBase<BlockT, LoopT>::verifyLoopNest(
     382             :     DenseSet<const LoopT *> *Loops) const {
     383             :   assert(!isInvalid() && "Loop not in a valid state!");
     384         217 :   Loops->insert(static_cast<const LoopT *>(this));
     385             :   // Verify this loop.
     386         217 :   verifyLoop();
     387             :   // Verify the subloops.
     388         298 :   for (iterator I = begin(), E = end(); I != E; ++I)
     389          81 :     (*I)->verifyLoopNest(Loops);
     390         217 : }
     391             : 
     392             : template <class BlockT, class LoopT>
     393         735 : void LoopBase<BlockT, LoopT>::print(raw_ostream &OS, unsigned Depth,
     394             :                                     bool Verbose) const {
     395        1470 :   OS.indent(Depth * 2) << "Loop at depth " << getLoopDepth() << " containing: ";
     396             : 
     397             :   BlockT *H = getHeader();
     398        2889 :   for (unsigned i = 0; i < getBlocks().size(); ++i) {
     399        1419 :     BlockT *BB = getBlocks()[i];
     400        1419 :     if (!Verbose) {
     401        1419 :       if (i)
     402         684 :         OS << ",";
     403        1419 :       BB->printAsOperand(OS, false);
     404             :     } else
     405           0 :       OS << "\n";
     406             : 
     407        1419 :     if (BB == H)
     408         735 :       OS << "<header>";
     409        1419 :     if (isLoopLatch(BB))
     410         735 :       OS << "<latch>";
     411        1419 :     if (isLoopExiting(BB))
     412         896 :       OS << "<exiting>";
     413        1419 :     if (Verbose)
     414           0 :       BB->print(OS);
     415             :   }
     416         735 :   OS << "\n";
     417             : 
     418         873 :   for (iterator I = begin(), E = end(); I != E; ++I)
     419         138 :     (*I)->print(OS, Depth + 2);
     420         735 : }
     421             : 
     422             : //===----------------------------------------------------------------------===//
     423             : /// Stable LoopInfo Analysis - Build a loop tree using stable iterators so the
     424             : /// result does / not depend on use list (block predecessor) order.
     425             : ///
     426             : 
     427             : /// Discover a subloop with the specified backedges such that: All blocks within
     428             : /// this loop are mapped to this loop or a subloop. And all subloops within this
     429             : /// loop have their parent loop set to this loop or a subloop.
     430             : template <class BlockT, class LoopT>
     431      146450 : static void discoverAndMapSubloop(LoopT *L, ArrayRef<BlockT *> Backedges,
     432             :                                   LoopInfoBase<BlockT, LoopT> *LI,
     433             :                                   const DomTreeBase<BlockT> &DomTree) {
     434             :   typedef GraphTraits<Inverse<BlockT *>> InvBlockTraits;
     435             : 
     436             :   unsigned NumBlocks = 0;
     437             :   unsigned NumSubloops = 0;
     438             : 
     439             :   // Perform a backward CFG traversal using a worklist.
     440      146450 :   std::vector<BlockT *> ReverseCFGWorklist(Backedges.begin(), Backedges.end());
     441     1112820 :   while (!ReverseCFGWorklist.empty()) {
     442      966370 :     BlockT *PredBB = ReverseCFGWorklist.back();
     443             :     ReverseCFGWorklist.pop_back();
     444             : 
     445             :     LoopT *Subloop = LI->getLoopFor(PredBB);
     446      217421 :     if (!Subloop) {
     447      748949 :       if (!DomTree.isReachableFromEntry(PredBB))
     448             :         continue;
     449             : 
     450             :       // This is an undiscovered block. Map it to the current loop.
     451      748925 :       LI->changeLoopFor(PredBB, L);
     452      748925 :       ++NumBlocks;
     453      748925 :       if (PredBB == L->getHeader())
     454             :         continue;
     455             :       // Push all block predecessors on the worklist.
     456      602465 :       ReverseCFGWorklist.insert(ReverseCFGWorklist.end(),
     457             :                                 InvBlockTraits::child_begin(PredBB),
     458             :                                 InvBlockTraits::child_end(PredBB));
     459             :     } else {
     460             :       // This is a discovered block. Find its outermost discovered loop.
     461      224198 :       while (LoopT *Parent = Subloop->getParentLoop())
     462             :         Subloop = Parent;
     463             : 
     464             :       // If it is already discovered to be a subloop of this loop, continue.
     465      217421 :       if (Subloop == L)
     466             :         continue;
     467             : 
     468             :       // Discover a subloop of this loop.
     469             :       Subloop->setParentLoop(L);
     470       25207 :       ++NumSubloops;
     471       50414 :       NumBlocks += Subloop->getBlocksVector().capacity();
     472             :       PredBB = Subloop->getHeader();
     473             :       // Continue traversal along predecessors that are not loop-back edges from
     474             :       // within this subloop tree itself. Note that a predecessor may directly
     475             :       // reach another subloop that is not yet discovered to be a subloop of
     476             :       // this loop, which we must traverse.
     477       76224 :       for (const auto Pred : children<Inverse<BlockT *>>(PredBB)) {
     478       51017 :         if (LI->getLoopFor(Pred) != Subloop)
     479       25406 :           ReverseCFGWorklist.push_back(Pred);
     480             :       }
     481             :     }
     482             :   }
     483      146450 :   L->getSubLoopsVector().reserve(NumSubloops);
     484             :   L->reserveBlocks(NumBlocks);
     485      146450 : }
     486             : 
     487             : /// Populate all loop data in a stable order during a single forward DFS.
     488             : template <class BlockT, class LoopT> class PopulateLoopsDFS {
     489             :   typedef GraphTraits<BlockT *> BlockTraits;
     490             :   typedef typename BlockTraits::ChildIteratorType SuccIterTy;
     491             : 
     492             :   LoopInfoBase<BlockT, LoopT> *LI;
     493             : 
     494             : public:
     495     2453018 :   PopulateLoopsDFS(LoopInfoBase<BlockT, LoopT> *li) : LI(li) {}
     496             : 
     497             :   void traverse(BlockT *EntryBlock);
     498             : 
     499             : protected:
     500             :   void insertIntoLoop(BlockT *Block);
     501             : };
     502             : 
     503             : /// Top-level driver for the forward DFS within the loop.
     504             : template <class BlockT, class LoopT>
     505     2453017 : void PopulateLoopsDFS<BlockT, LoopT>::traverse(BlockT *EntryBlock) {
     506    12135057 :   for (BlockT *BB : post_order(EntryBlock))
     507     7229023 :     insertIntoLoop(BB);
     508     2453018 : }
     509             : 
     510             : /// Add a single Block to its ancestor loops in PostOrder. If the block is a
     511             : /// subloop header, add the subloop to its parent in PostOrder, then reverse the
     512             : /// Block and Subloop vectors of the now complete subloop to achieve RPO.
     513             : template <class BlockT, class LoopT>
     514     7229023 : void PopulateLoopsDFS<BlockT, LoopT>::insertIntoLoop(BlockT *Block) {
     515     7229023 :   LoopT *Subloop = LI->getLoopFor(Block);
     516     7229023 :   if (Subloop && Block == Subloop->getHeader()) {
     517             :     // We reach this point once per subloop after processing all the blocks in
     518             :     // the subloop.
     519      146450 :     if (Subloop->getParentLoop())
     520       25207 :       Subloop->getParentLoop()->getSubLoopsVector().push_back(Subloop);
     521             :     else
     522      121243 :       LI->addTopLevelLoop(Subloop);
     523             : 
     524             :     // For convenience, Blocks and Subloops are inserted in postorder. Reverse
     525             :     // the lists, except for the loop header, which is always at the beginning.
     526      146450 :     Subloop->reverseBlock(1);
     527             :     std::reverse(Subloop->getSubLoopsVector().begin(),
     528             :                  Subloop->getSubLoopsVector().end());
     529             : 
     530      292892 :     Subloop = Subloop->getParentLoop();
     531             :   }
     532     8756427 :   for (; Subloop; Subloop = Subloop->getParentLoop())
     533      763708 :     Subloop->addBlockEntry(Block);
     534     7229023 : }
     535             : 
     536             : /// Analyze LoopInfo discovers loops during a postorder DominatorTree traversal
     537             : /// interleaved with backward CFG traversals within each subloop
     538             : /// (discoverAndMapSubloop). The backward traversal skips inner subloops, so
     539             : /// this part of the algorithm is linear in the number of CFG edges. Subloop and
     540             : /// Block vectors are then populated during a single forward CFG traversal
     541             : /// (PopulateLoopDFS).
     542             : ///
     543             : /// During the two CFG traversals each block is seen three times:
     544             : /// 1) Discovered and mapped by a reverse CFG traversal.
     545             : /// 2) Visited during a forward DFS CFG traversal.
     546             : /// 3) Reverse-inserted in the loop in postorder following forward DFS.
     547             : ///
     548             : /// The Block vectors are inclusive, so step 3 requires loop-depth number of
     549             : /// insertions per block.
     550             : template <class BlockT, class LoopT>
     551     2453018 : void LoopInfoBase<BlockT, LoopT>::analyze(const DomTreeBase<BlockT> &DomTree) {
     552             :   // Postorder traversal of the dominator tree.
     553     2453018 :   const DomTreeNodeBase<BlockT> *DomRoot = DomTree.getRootNode();
     554    12135057 :   for (auto DomNode : post_order(DomRoot)) {
     555             : 
     556     7229022 :     BlockT *Header = DomNode->getBlock();
     557             :     SmallVector<BlockT *, 4> Backedges;
     558             : 
     559             :     // Check each predecessor of the potential loop header.
     560    13820061 :     for (const auto Backedge : children<Inverse<BlockT *>>(Header)) {
     561             :       // If Header dominates predBB, this is a new loop. Collect the backedges.
     562     6591038 :       if (DomTree.dominates(Header, Backedge) &&
     563             :           DomTree.isReachableFromEntry(Backedge)) {
     564      150174 :         Backedges.push_back(Backedge);
     565             :       }
     566             :     }
     567             :     // Perform a backward CFG traversal to discover and map blocks in this loop.
     568     7229023 :     if (!Backedges.empty()) {
     569      146450 :       LoopT *L = AllocateLoop(Header);
     570      146450 :       discoverAndMapSubloop(L, ArrayRef<BlockT *>(Backedges), this, DomTree);
     571             :     }
     572             :   }
     573             :   // Perform a single forward CFG traversal to populate block and subloop
     574             :   // vectors for all loops.
     575             :   PopulateLoopsDFS<BlockT, LoopT> DFS(this);
     576     2453018 :   DFS.traverse(DomRoot->getBlock());
     577     2453018 : }
     578             : 
     579             : template <class BlockT, class LoopT>
     580          53 : SmallVector<LoopT *, 4> LoopInfoBase<BlockT, LoopT>::getLoopsInPreorder() {
     581             :   SmallVector<LoopT *, 4> PreOrderLoops, PreOrderWorklist;
     582             :   // The outer-most loop actually goes into the result in the same relative
     583             :   // order as we walk it. But LoopInfo stores the top level loops in reverse
     584             :   // program order so for here we reverse it to get forward program order.
     585             :   // FIXME: If we change the order of LoopInfo we will want to remove the
     586             :   // reverse here.
     587         106 :   for (LoopT *RootL : reverse(*this)) {
     588             :     assert(PreOrderWorklist.empty() &&
     589             :            "Must start with an empty preorder walk worklist.");
     590          53 :     PreOrderWorklist.push_back(RootL);
     591             :     do {
     592          66 :       LoopT *L = PreOrderWorklist.pop_back_val();
     593             :       // Sub-loops are stored in forward program order, but will process the
     594             :       // worklist backwards so append them in reverse order.
     595          66 :       PreOrderWorklist.append(L->rbegin(), L->rend());
     596          66 :       PreOrderLoops.push_back(L);
     597          66 :     } while (!PreOrderWorklist.empty());
     598             :   }
     599             : 
     600          53 :   return PreOrderLoops;
     601             : }
     602             : 
     603             : template <class BlockT, class LoopT>
     604             : SmallVector<LoopT *, 4>
     605         462 : LoopInfoBase<BlockT, LoopT>::getLoopsInReverseSiblingPreorder() {
     606             :   SmallVector<LoopT *, 4> PreOrderLoops, PreOrderWorklist;
     607             :   // The outer-most loop actually goes into the result in the same relative
     608             :   // order as we walk it. LoopInfo stores the top level loops in reverse
     609             :   // program order so we walk in order here.
     610             :   // FIXME: If we change the order of LoopInfo we will want to add a reverse
     611             :   // here.
     612        1030 :   for (LoopT *RootL : *this) {
     613             :     assert(PreOrderWorklist.empty() &&
     614             :            "Must start with an empty preorder walk worklist.");
     615         568 :     PreOrderWorklist.push_back(RootL);
     616             :     do {
     617         740 :       LoopT *L = PreOrderWorklist.pop_back_val();
     618             :       // Sub-loops are stored in forward program order, but will process the
     619             :       // worklist backwards so we can just append them in order.
     620         740 :       PreOrderWorklist.append(L->begin(), L->end());
     621         740 :       PreOrderLoops.push_back(L);
     622         740 :     } while (!PreOrderWorklist.empty());
     623             :   }
     624             : 
     625         462 :   return PreOrderLoops;
     626             : }
     627             : 
     628             : // Debugging
     629             : template <class BlockT, class LoopT>
     630          10 : void LoopInfoBase<BlockT, LoopT>::print(raw_ostream &OS) const {
     631          35 :   for (unsigned i = 0; i < TopLevelLoops.size(); ++i)
     632          15 :     TopLevelLoops[i]->print(OS);
     633             : #if 0
     634             :   for (DenseMap<BasicBlock*, LoopT*>::const_iterator I = BBMap.begin(),
     635             :          E = BBMap.end(); I != E; ++I)
     636             :     OS << "BB '" << I->first->getName() << "' level = "
     637             :        << I->second->getLoopDepth() << "\n";
     638             : #endif
     639          10 : }
     640             : 
     641             : template <typename T>
     642             : bool compareVectors(std::vector<T> &BB1, std::vector<T> &BB2) {
     643             :   llvm::sort(BB1);
     644             :   llvm::sort(BB2);
     645             :   return BB1 == BB2;
     646             : }
     647             : 
     648             : template <class BlockT, class LoopT>
     649             : void addInnerLoopsToHeadersMap(DenseMap<BlockT *, const LoopT *> &LoopHeaders,
     650             :                                const LoopInfoBase<BlockT, LoopT> &LI,
     651             :                                const LoopT &L) {
     652             :   LoopHeaders[L.getHeader()] = &L;
     653             :   for (LoopT *SL : L)
     654             :     addInnerLoopsToHeadersMap(LoopHeaders, LI, *SL);
     655             : }
     656             : 
     657             : #ifndef NDEBUG
     658             : template <class BlockT, class LoopT>
     659             : static void compareLoops(const LoopT *L, const LoopT *OtherL,
     660             :                          DenseMap<BlockT *, const LoopT *> &OtherLoopHeaders) {
     661             :   BlockT *H = L->getHeader();
     662             :   BlockT *OtherH = OtherL->getHeader();
     663             :   assert(H == OtherH &&
     664             :          "Mismatched headers even though found in the same map entry!");
     665             : 
     666             :   assert(L->getLoopDepth() == OtherL->getLoopDepth() &&
     667             :          "Mismatched loop depth!");
     668             :   const LoopT *ParentL = L, *OtherParentL = OtherL;
     669             :   do {
     670             :     assert(ParentL->getHeader() == OtherParentL->getHeader() &&
     671             :            "Mismatched parent loop headers!");
     672             :     ParentL = ParentL->getParentLoop();
     673             :     OtherParentL = OtherParentL->getParentLoop();
     674             :   } while (ParentL);
     675             : 
     676             :   for (const LoopT *SubL : *L) {
     677             :     BlockT *SubH = SubL->getHeader();
     678             :     const LoopT *OtherSubL = OtherLoopHeaders.lookup(SubH);
     679             :     assert(OtherSubL && "Inner loop is missing in computed loop info!");
     680             :     OtherLoopHeaders.erase(SubH);
     681             :     compareLoops(SubL, OtherSubL, OtherLoopHeaders);
     682             :   }
     683             : 
     684             :   std::vector<BlockT *> BBs = L->getBlocks();
     685             :   std::vector<BlockT *> OtherBBs = OtherL->getBlocks();
     686             :   assert(compareVectors(BBs, OtherBBs) &&
     687             :          "Mismatched basic blocks in the loops!");
     688             : 
     689             :   const SmallPtrSetImpl<const BlockT *> &BlocksSet = L->getBlocksSet();
     690             :   const SmallPtrSetImpl<const BlockT *> &OtherBlocksSet = L->getBlocksSet();
     691             :   assert(BlocksSet.size() == OtherBlocksSet.size() &&
     692             :          std::all_of(BlocksSet.begin(), BlocksSet.end(),
     693             :                      [&OtherBlocksSet](const BlockT *BB) {
     694             :                        return OtherBlocksSet.count(BB);
     695             :                      }) &&
     696             :          "Mismatched basic blocks in BlocksSets!");
     697             : }
     698             : #endif
     699             : 
     700             : template <class BlockT, class LoopT>
     701          94 : void LoopInfoBase<BlockT, LoopT>::verify(
     702             :     const DomTreeBase<BlockT> &DomTree) const {
     703             :   DenseSet<const LoopT *> Loops;
     704         230 :   for (iterator I = begin(), E = end(); I != E; ++I) {
     705             :     assert(!(*I)->getParentLoop() && "Top-level loop has a parent!");
     706         136 :     (*I)->verifyLoopNest(&Loops);
     707             :   }
     708             : 
     709             : // Verify that blocks are mapped to valid loops.
     710             : #ifndef NDEBUG
     711             :   for (auto &Entry : BBMap) {
     712             :     const BlockT *BB = Entry.first;
     713             :     LoopT *L = Entry.second;
     714             :     assert(Loops.count(L) && "orphaned loop");
     715             :     assert(L->contains(BB) && "orphaned block");
     716             :     for (LoopT *ChildLoop : *L)
     717             :       assert(!ChildLoop->contains(BB) &&
     718             :              "BBMap should point to the innermost loop containing BB");
     719             :   }
     720             : 
     721             :   // Recompute LoopInfo to verify loops structure.
     722             :   LoopInfoBase<BlockT, LoopT> OtherLI;
     723             :   OtherLI.analyze(DomTree);
     724             : 
     725             :   // Build a map we can use to move from our LI to the computed one. This
     726             :   // allows us to ignore the particular order in any layer of the loop forest
     727             :   // while still comparing the structure.
     728             :   DenseMap<BlockT *, const LoopT *> OtherLoopHeaders;
     729             :   for (LoopT *L : OtherLI)
     730             :     addInnerLoopsToHeadersMap(OtherLoopHeaders, OtherLI, *L);
     731             : 
     732             :   // Walk the top level loops and ensure there is a corresponding top-level
     733             :   // loop in the computed version and then recursively compare those loop
     734             :   // nests.
     735             :   for (LoopT *L : *this) {
     736             :     BlockT *Header = L->getHeader();
     737             :     const LoopT *OtherL = OtherLoopHeaders.lookup(Header);
     738             :     assert(OtherL && "Top level loop is missing in computed loop info!");
     739             :     // Now that we've matched this loop, erase its header from the map.
     740             :     OtherLoopHeaders.erase(Header);
     741             :     // And recursively compare these loops.
     742             :     compareLoops(L, OtherL, OtherLoopHeaders);
     743             :   }
     744             : 
     745             :   // Any remaining entries in the map are loops which were found when computing
     746             :   // a fresh LoopInfo but not present in the current one.
     747             :   if (!OtherLoopHeaders.empty()) {
     748             :     for (const auto &HeaderAndLoop : OtherLoopHeaders)
     749             :       dbgs() << "Found new loop: " << *HeaderAndLoop.second << "\n";
     750             :     llvm_unreachable("Found new loops when recomputing LoopInfo!");
     751             :   }
     752             : #endif
     753          94 : }
     754             : 
     755             : } // End llvm namespace
     756             : 
     757             : #endif

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