LCOV - code coverage report
Current view: top level - lib/Analysis - LoopPass.cpp (source / functions) Hit Total Coverage
Test: llvm-toolchain.info Lines: 127 132 96.2 %
Date: 2018-06-17 00:07:59 Functions: 20 21 95.2 %
Legend: Lines: hit not hit

          Line data    Source code
       1             : //===- LoopPass.cpp - Loop Pass and Loop Pass Manager ---------------------===//
       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 implements LoopPass and LPPassManager. All loop optimization
      11             : // and transformation passes are derived from LoopPass. LPPassManager is
      12             : // responsible for managing LoopPasses.
      13             : //
      14             : //===----------------------------------------------------------------------===//
      15             : 
      16             : #include "llvm/Analysis/LoopPass.h"
      17             : #include "llvm/Analysis/LoopAnalysisManager.h"
      18             : #include "llvm/IR/Dominators.h"
      19             : #include "llvm/IR/IRPrintingPasses.h"
      20             : #include "llvm/IR/LLVMContext.h"
      21             : #include "llvm/IR/OptBisect.h"
      22             : #include "llvm/IR/PassManager.h"
      23             : #include "llvm/Support/Debug.h"
      24             : #include "llvm/Support/Timer.h"
      25             : #include "llvm/Support/raw_ostream.h"
      26             : using namespace llvm;
      27             : 
      28             : #define DEBUG_TYPE "loop-pass-manager"
      29             : 
      30             : namespace {
      31             : 
      32             : /// PrintLoopPass - Print a Function corresponding to a Loop.
      33             : ///
      34          57 : class PrintLoopPassWrapper : public LoopPass {
      35             :   raw_ostream &OS;
      36             :   std::string Banner;
      37             : 
      38             : public:
      39             :   static char ID;
      40             :   PrintLoopPassWrapper() : LoopPass(ID), OS(dbgs()) {}
      41             :   PrintLoopPassWrapper(raw_ostream &OS, const std::string &Banner)
      42          38 :       : LoopPass(ID), OS(OS), Banner(Banner) {}
      43             : 
      44          19 :   void getAnalysisUsage(AnalysisUsage &AU) const override {
      45             :     AU.setPreservesAll();
      46          19 :   }
      47             : 
      48           6 :   bool runOnLoop(Loop *L, LPPassManager &) override {
      49             :     auto BBI = llvm::find_if(L->blocks(), [](BasicBlock *BB) { return BB; });
      50          12 :     if (BBI != L->blocks().end() &&
      51           6 :         isFunctionInPrintList((*BBI)->getParent()->getName())) {
      52           4 :       printLoop(*L, OS, Banner);
      53             :     }
      54           6 :     return false;
      55             :   }
      56             : 
      57           0 :   StringRef getPassName() const override { return "Print Loop IR"; }
      58             : };
      59             : 
      60             : char PrintLoopPassWrapper::ID = 0;
      61             : }
      62             : 
      63             : //===----------------------------------------------------------------------===//
      64             : // LPPassManager
      65             : //
      66             : 
      67             : char LPPassManager::ID = 0;
      68             : 
      69       29355 : LPPassManager::LPPassManager()
      70       29355 :   : FunctionPass(ID), PMDataManager() {
      71       29355 :   LI = nullptr;
      72       29355 :   CurrentLoop = nullptr;
      73       29355 : }
      74             : 
      75             : // Insert loop into loop nest (LoopInfo) and loop queue (LQ).
      76         227 : void LPPassManager::addLoop(Loop &L) {
      77         227 :   if (!L.getParentLoop()) {
      78             :     // This is the top level loop.
      79         346 :     LQ.push_front(&L);
      80         173 :     return;
      81             :   }
      82             : 
      83             :   // Insert L into the loop queue after the parent loop.
      84          78 :   for (auto I = LQ.begin(), E = LQ.end(); I != E; ++I) {
      85          78 :     if (*I == L.getParentLoop()) {
      86             :       // deque does not support insert after.
      87             :       ++I;
      88         108 :       LQ.insert(I, 1, &L);
      89             :       return;
      90             :     }
      91             :   }
      92             : }
      93             : 
      94             : /// cloneBasicBlockSimpleAnalysis - Invoke cloneBasicBlockAnalysis hook for
      95             : /// all loop passes.
      96         408 : void LPPassManager::cloneBasicBlockSimpleAnalysis(BasicBlock *From,
      97             :                                                   BasicBlock *To, Loop *L) {
      98        1318 :   for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
      99             :     LoopPass *LP = getContainedPass(Index);
     100         455 :     LP->cloneBasicBlockAnalysis(From, To, L);
     101             :   }
     102         408 : }
     103             : 
     104             : /// deleteSimpleAnalysisValue - Invoke deleteAnalysisValue hook for all passes.
     105         141 : void LPPassManager::deleteSimpleAnalysisValue(Value *V, Loop *L) {
     106             :   if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) {
     107           0 :     for (Instruction &I : *BB) {
     108           0 :       deleteSimpleAnalysisValue(&I, L);
     109             :     }
     110             :   }
     111         459 :   for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
     112             :     LoopPass *LP = getContainedPass(Index);
     113         159 :     LP->deleteAnalysisValue(V, L);
     114             :   }
     115         141 : }
     116             : 
     117             : /// Invoke deleteAnalysisLoop hook for all passes.
     118         597 : void LPPassManager::deleteSimpleAnalysisLoop(Loop *L) {
     119        3267 :   for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
     120             :     LoopPass *LP = getContainedPass(Index);
     121        1335 :     LP->deleteAnalysisLoop(L);
     122             :   }
     123         597 : }
     124             : 
     125             : 
     126             : // Recurse through all subloops and all loops  into LQ.
     127       30121 : static void addLoopIntoQueue(Loop *L, std::deque<Loop *> &LQ) {
     128       30121 :   LQ.push_back(L);
     129       65740 :   for (Loop *I : reverse(*L))
     130        5498 :     addLoopIntoQueue(I, LQ);
     131       30121 : }
     132             : 
     133             : /// Pass Manager itself does not invalidate any analysis info.
     134       29355 : void LPPassManager::getAnalysisUsage(AnalysisUsage &Info) const {
     135             :   // LPPassManager needs LoopInfo. In the long term LoopInfo class will
     136             :   // become part of LPPassManager.
     137             :   Info.addRequired<LoopInfoWrapperPass>();
     138             :   Info.addRequired<DominatorTreeWrapperPass>();
     139             :   Info.setPreservesAll();
     140       29355 : }
     141             : 
     142         425 : void LPPassManager::markLoopAsDeleted(Loop &L) {
     143             :   assert((&L == CurrentLoop || CurrentLoop->contains(&L)) &&
     144             :          "Must not delete loop outside the current loop tree!");
     145         425 :   if (&L == CurrentLoop)
     146         425 :     CurrentLoopDeleted = true;
     147         425 : }
     148             : 
     149             : /// run - Execute all of the passes scheduled for execution.  Keep track of
     150             : /// whether any of the passes modifies the function, and if so, return true.
     151      338999 : bool LPPassManager::runOnFunction(Function &F) {
     152      338999 :   auto &LIWP = getAnalysis<LoopInfoWrapperPass>();
     153      338999 :   LI = &LIWP.getLoopInfo();
     154      338999 :   Module &M = *F.getParent();
     155             : #if 0
     156             :   DominatorTree *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
     157             : #endif
     158             :   bool Changed = false;
     159             : 
     160             :   // Collect inherited analysis from Module level pass manager.
     161      338999 :   populateInheritedAnalysis(TPM->activeStack);
     162             : 
     163             :   // Populate the loop queue in reverse program order. There is no clear need to
     164             :   // process sibling loops in either forward or reverse order. There may be some
     165             :   // advantage in deleting uses in a later loop before optimizing the
     166             :   // definitions in an earlier loop. If we find a clear reason to process in
     167             :   // forward order, then a forward variant of LoopPassManager should be created.
     168             :   //
     169             :   // Note that LoopInfo::iterator visits loops in reverse program
     170             :   // order. Here, reverse_iterator gives us a forward order, and the LoopQueue
     171             :   // reverses the order a third time by popping from the back.
     172      363622 :   for (Loop *L : reverse(*LI))
     173       24623 :     addLoopIntoQueue(L, LQ);
     174             : 
     175      338999 :   if (LQ.empty()) // No loops, skip calling finalizers
     176             :     return false;
     177             : 
     178             :   // Initialization
     179       48610 :   for (Loop *L : LQ) {
     180      139403 :     for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
     181             :       LoopPass *P = getContainedPass(Index);
     182       54641 :       Changed |= P->doInitialization(L, *this);
     183             :     }
     184             :   }
     185             : 
     186             :   // Walk Loops
     187       79185 :   while (!LQ.empty()) {
     188       30348 :     CurrentLoopDeleted = false;
     189       30348 :     CurrentLoop = LQ.back();
     190             : 
     191             :     // Run all passes on the current Loop.
     192      139018 :     for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
     193             :       LoopPass *P = getContainedPass(Index);
     194             : 
     195      109520 :       dumpPassInfo(P, EXECUTION_MSG, ON_LOOP_MSG,
     196       54760 :                    CurrentLoop->getHeader()->getName());
     197       54760 :       dumpRequiredSet(P);
     198             : 
     199       54760 :       initializeAnalysisImpl(P);
     200             : 
     201             :       {
     202      109520 :         PassManagerPrettyStackEntry X(P, *CurrentLoop->getHeader());
     203       54760 :         TimeRegion PassTimer(getPassTimer(P));
     204       54760 :         unsigned InstrCount = initSizeRemarkInfo(M);
     205       54760 :         Changed |= P->runOnLoop(CurrentLoop, *this);
     206       54760 :         emitInstrCountChangedRemark(P, M, InstrCount);
     207             :       }
     208             : 
     209       54760 :       if (Changed)
     210       37743 :         dumpPassInfo(P, MODIFICATION_MSG, ON_LOOP_MSG,
     211       19084 :                      CurrentLoopDeleted ? "<deleted loop>"
     212       18659 :                                         : CurrentLoop->getName());
     213       54760 :       dumpPreservedSet(P);
     214             : 
     215       54760 :       if (CurrentLoopDeleted) {
     216             :         // Notify passes that the loop is being deleted.
     217         425 :         deleteSimpleAnalysisLoop(CurrentLoop);
     218             :       } else {
     219             :         // Manually check that this loop is still healthy. This is done
     220             :         // instead of relying on LoopInfo::verifyLoop since LoopInfo
     221             :         // is a function pass and it's really expensive to verify every
     222             :         // loop in the function every time. That level of checking can be
     223             :         // enabled with the -verify-loop-info option.
     224             :         {
     225       54335 :           TimeRegion PassTimer(getPassTimer(&LIWP));
     226       54335 :           CurrentLoop->verifyLoop();
     227             :         }
     228             :         // Here we apply same reasoning as in the above case. Only difference
     229             :         // is that LPPassManager might run passes which do not require LCSSA
     230             :         // form (LoopPassPrinter for example). We should skip verification for
     231             :         // such passes.
     232             :         // FIXME: Loop-sink currently break LCSSA. Fix it and reenable the
     233             :         // verification!
     234             : #if 0
     235             :         if (mustPreserveAnalysisID(LCSSAVerificationPass::ID))
     236             :           assert(CurrentLoop->isRecursivelyLCSSAForm(*DT, *LI));
     237             : #endif
     238             : 
     239             :         // Then call the regular verifyAnalysis functions.
     240       54335 :         verifyPreservedAnalysis(P);
     241             : 
     242       54335 :         F.getContext().yield();
     243             :       }
     244             : 
     245       54760 :       removeNotPreservedAnalysis(P);
     246       54760 :       recordAvailableAnalysis(P);
     247      109095 :       removeDeadPasses(P,
     248       54760 :                        CurrentLoopDeleted ? "<deleted>"
     249      108670 :                                           : CurrentLoop->getHeader()->getName(),
     250             :                        ON_LOOP_MSG);
     251             : 
     252       54760 :       if (CurrentLoopDeleted)
     253             :         // Do not run other passes on this loop.
     254             :         break;
     255             :     }
     256             : 
     257             :     // If the loop was deleted, release all the loop passes. This frees up
     258             :     // some memory, and avoids trouble with the pass manager trying to call
     259             :     // verifyAnalysis on them.
     260       30348 :     if (CurrentLoopDeleted) {
     261        2731 :       for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
     262             :         Pass *P = getContainedPass(Index);
     263        2306 :         freePass(P, "<deleted>", ON_LOOP_MSG);
     264             :       }
     265             :     }
     266             : 
     267             :     // Pop the loop from queue after running all passes.
     268       30348 :     LQ.pop_back();
     269             :   }
     270             : 
     271             :   // Finalization
     272       86137 :   for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
     273             :     LoopPass *P = getContainedPass(Index);
     274       33824 :     Changed |= P->doFinalization();
     275             :   }
     276             : 
     277             :   return Changed;
     278             : }
     279             : 
     280             : /// Print passes managed by this manager
     281          64 : void LPPassManager::dumpPassStructure(unsigned Offset) {
     282          64 :   errs().indent(Offset*2) << "Loop Pass Manager\n";
     283         288 :   for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
     284             :     Pass *P = getContainedPass(Index);
     285         112 :     P->dumpPassStructure(Offset + 1);
     286         112 :     dumpLastUses(P, Offset+1);
     287             :   }
     288          64 : }
     289             : 
     290             : 
     291             : //===----------------------------------------------------------------------===//
     292             : // LoopPass
     293             : 
     294          19 : Pass *LoopPass::createPrinterPass(raw_ostream &O,
     295             :                                   const std::string &Banner) const {
     296          38 :   return new PrintLoopPassWrapper(O, Banner);
     297             : }
     298             : 
     299             : // Check if this pass is suitable for the current LPPassManager, if
     300             : // available. This pass P is not suitable for a LPPassManager if P
     301             : // is not preserving higher level analysis info used by other
     302             : // LPPassManager passes. In such case, pop LPPassManager from the
     303             : // stack. This will force assignPassManager() to create new
     304             : // LPPassManger as expected.
     305       54339 : void LoopPass::preparePassManager(PMStack &PMS) {
     306             : 
     307             :   // Find LPPassManager
     308      108678 :   while (!PMS.empty() &&
     309       54339 :          PMS.top()->getPassManagerType() > PMT_LoopPassManager)
     310           0 :     PMS.pop();
     311             : 
     312             :   // If this pass is destroying high level information that is used
     313             :   // by other passes that are managed by LPM then do not insert
     314             :   // this pass in current LPM. Use new LPPassManager.
     315       60313 :   if (PMS.top()->getPassManagerType() == PMT_LoopPassManager &&
     316        5974 :       !PMS.top()->preserveHigherLevelAnalysis(this))
     317          28 :     PMS.pop();
     318       54339 : }
     319             : 
     320             : /// Assign pass manager to manage this pass.
     321       54358 : void LoopPass::assignPassManager(PMStack &PMS,
     322             :                                  PassManagerType PreferredType) {
     323             :   // Find LPPassManager
     324      108716 :   while (!PMS.empty() &&
     325       54358 :          PMS.top()->getPassManagerType() > PMT_LoopPassManager)
     326           0 :     PMS.pop();
     327             : 
     328             :   LPPassManager *LPPM;
     329       54358 :   if (PMS.top()->getPassManagerType() == PMT_LoopPassManager)
     330       25003 :     LPPM = (LPPassManager*)PMS.top();
     331             :   else {
     332             :     // Create new Loop Pass Manager if it does not exist.
     333             :     assert (!PMS.empty() && "Unable to create Loop Pass Manager");
     334             :     PMDataManager *PMD = PMS.top();
     335             : 
     336             :     // [1] Create new Loop Pass Manager
     337       29355 :     LPPM = new LPPassManager();
     338             :     LPPM->populateInheritedAnalysis(PMS);
     339             : 
     340             :     // [2] Set up new manager's top level manager
     341       29355 :     PMTopLevelManager *TPM = PMD->getTopLevelManager();
     342       29355 :     TPM->addIndirectPassManager(LPPM);
     343             : 
     344             :     // [3] Assign manager to manage this new manager. This may create
     345             :     // and push new managers into PMS
     346       29355 :     Pass *P = LPPM->getAsPass();
     347       29355 :     TPM->schedulePass(P);
     348             : 
     349             :     // [4] Push new manager into PMS
     350       29355 :     PMS.push(LPPM);
     351             :   }
     352             : 
     353       54358 :   LPPM->add(this);
     354       54358 : }
     355             : 
     356       47821 : bool LoopPass::skipLoop(const Loop *L) const {
     357       47821 :   const Function *F = L->getHeader()->getParent();
     358       47821 :   if (!F)
     359             :     return false;
     360             :   // Check the opt bisect limit.
     361       47821 :   LLVMContext &Context = F->getContext();
     362       47821 :   if (!Context.getOptPassGate().shouldRunPass(this, *L))
     363             :     return true;
     364             :   // Check for the OptimizeNone attribute.
     365       47631 :   if (F->hasFnAttribute(Attribute::OptimizeNone)) {
     366             :     // FIXME: Report this to dbgs() only once per function.
     367             :     LLVM_DEBUG(dbgs() << "Skipping pass '" << getPassName() << "' in function "
     368             :                       << F->getName() << "\n");
     369             :     // FIXME: Delete loop from pass manager's queue?
     370             :     return true;
     371             :   }
     372       47580 :   return false;
     373             : }
     374             : 
     375             : char LCSSAVerificationPass::ID = 0;
     376      346274 : INITIALIZE_PASS(LCSSAVerificationPass, "lcssa-verification", "LCSSA Verifier",
     377             :                 false, false)

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