lib/Analysis/LoopPass.cpp

   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 using namespace llvm;
  18
  19 //===----------------------------------------------------------------------===//
  20 // LPPassManager
  21 //
  22
  23 char LPPassManager::ID = 0;
  24 /// LPPassManager manages FPPassManagers and CalLGraphSCCPasses.
  25
  26 LPPassManager::LPPassManager(int Depth)
  27   : FunctionPass(&ID), PMDataManager(Depth) {
  28   skipThisLoop = false;
  29   redoThisLoop = false;
  30   LI = NULL;
  31   CurrentLoop = NULL;
  32 }
  33
  34 /// Delete loop from the loop queue and loop hierarchy (LoopInfo).
  35 void LPPassManager::deleteLoopFromQueue(Loop *L) {
  36
  37   if (Loop *ParentLoop = L->getParentLoop()) { // Not a top-level loop.
  38     // Reparent all of the blocks in this loop.  Since BBLoop had a parent,
  39     // they are now all in it.
  40     for (Loop::block_iterator I = L->block_begin(), E = L->block_end();
  41          I != E; ++I)
  42       if (LI->getLoopFor(*I) == L)    // Don't change blocks in subloops.
  43         LI->changeLoopFor(*I, ParentLoop);
  44
  45     // Remove the loop from its parent loop.
  46     for (Loop::iterator I = ParentLoop->begin(), E = ParentLoop->end();;
  47          ++I) {
  48       assert(I != E && "Couldn't find loop");
  49       if (*I == L) {
  50         ParentLoop->removeChildLoop(I);
  51         break;
  52       }
  53     }
  54
  55     // Move all subloops into the parent loop.
  56     while (!L->empty())
  57       ParentLoop->addChildLoop(L->removeChildLoop(L->end()-1));
  58   } else {
  59     // Reparent all of the blocks in this loop.  Since BBLoop had no parent,
  60     // they no longer in a loop at all.
  61
  62     for (unsigned i = 0; i != L->getBlocks().size(); ++i) {
  63       // Don't change blocks in subloops.
  64       if (LI->getLoopFor(L->getBlocks()[i]) == L) {
  65         LI->removeBlock(L->getBlocks()[i]);
  66         --i;
  67       }
  68     }
  69
  70     // Remove the loop from the top-level LoopInfo object.
  71     for (LoopInfo::iterator I = LI->begin(), E = LI->end();; ++I) {
  72       assert(I != E && "Couldn't find loop");
  73       if (*I == L) {
  74         LI->removeLoop(I);
  75         break;
  76       }
  77     }
  78
  79     // Move all of the subloops to the top-level.
  80     while (!L->empty())
  81       LI->addTopLevelLoop(L->removeChildLoop(L->end()-1));
  82   }
  83
  84   delete L;
  85
  86   // If L is current loop then skip rest of the passes and let
  87   // runOnFunction remove L from LQ. Otherwise, remove L from LQ now
  88   // and continue applying other passes on CurrentLoop.
  89   if (CurrentLoop == L) {
  90     skipThisLoop = true;
  91     return;
  92   }
  93
  94   for (std::deque<Loop *>::iterator I = LQ.begin(),
  95          E = LQ.end(); I != E; ++I) {
  96     if (*I == L) {
  97       LQ.erase(I);
  98       break;
  99     }
 100   }
 101 }
 102
 103 // Inset loop into loop nest (LoopInfo) and loop queue (LQ).
 104 void LPPassManager::insertLoop(Loop *L, Loop *ParentLoop) {
 105
 106   assert (CurrentLoop != L && "Cannot insert CurrentLoop");
 107
 108   // Insert into loop nest
 109   if (ParentLoop)
 110     ParentLoop->addChildLoop(L);
 111   else
 112     LI->addTopLevelLoop(L);
 113
 114   // Insert L into loop queue
 115   if (L == CurrentLoop)
 116     redoLoop(L);
 117   else if (!ParentLoop)
 118     // This is top level loop.
 119     LQ.push_front(L);
 120   else {
 121     // Insert L after ParentLoop
 122     for (std::deque<Loop *>::iterator I = LQ.begin(),
 123            E = LQ.end(); I != E; ++I) {
 124       if (*I == ParentLoop) {
 125         // deque does not support insert after.
 126         ++I;
 127         LQ.insert(I, 1, L);
 128         break;
 129       }
 130     }
 131   }
 132 }
 133
 134 // Reoptimize this loop. LPPassManager will re-insert this loop into the
 135 // queue. This allows LoopPass to change loop nest for the loop. This
 136 // utility may send LPPassManager into infinite loops so use caution.
 137 void LPPassManager::redoLoop(Loop *L) {
 138   assert (CurrentLoop == L && "Can redo only CurrentLoop");
 139   redoThisLoop = true;
 140 }
 141
 142 /// cloneBasicBlockSimpleAnalysis - Invoke cloneBasicBlockAnalysis hook for
 143 /// all loop passes.
 144 void LPPassManager::cloneBasicBlockSimpleAnalysis(BasicBlock *From,
 145                                                   BasicBlock *To, Loop *L) {
 146   for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
 147     Pass *P = getContainedPass(Index);
 148     LoopPass *LP = dynamic_cast<LoopPass *>(P);
 149     LP->cloneBasicBlockAnalysis(From, To, L);
 150   }
 151 }
 152
 153 /// deleteSimpleAnalysisValue - Invoke deleteAnalysisValue hook for all passes.
 154 void LPPassManager::deleteSimpleAnalysisValue(Value *V, Loop *L) {
 155   if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) {
 156     for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;
 157          ++BI) {
 158       Instruction &I = *BI;
 159       deleteSimpleAnalysisValue(&I, L);
 160     }
 161   }
 162   for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
 163     Pass *P = getContainedPass(Index);
 164     LoopPass *LP = dynamic_cast<LoopPass *>(P);
 165     LP->deleteAnalysisValue(V, L);
 166   }
 167 }
 168
 169
 170 // Recurse through all subloops and all loops  into LQ.
 171 static void addLoopIntoQueue(Loop *L, std::deque<Loop *> &LQ) {
 172   LQ.push_back(L);
 173   for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I)
 174     addLoopIntoQueue(*I, LQ);
 175 }
 176
 177 /// Pass Manager itself does not invalidate any analysis info.
 178 void LPPassManager::getAnalysisUsage(AnalysisUsage &Info) const {
 179   // LPPassManager needs LoopInfo. In the long term LoopInfo class will
 180   // become part of LPPassManager.
 181   Info.addRequired<LoopInfo>();
 182   Info.setPreservesAll();
 183 }
 184
 185 /// run - Execute all of the passes scheduled for execution.  Keep track of
 186 /// whether any of the passes modifies the function, and if so, return true.
 187 bool LPPassManager::runOnFunction(Function &F) {
 188   LI = &getAnalysis<LoopInfo>();
 189   bool Changed = false;
 190
 191   // Collect inherited analysis from Module level pass manager.
 192   populateInheritedAnalysis(TPM->activeStack);
 193
 194   // Populate Loop Queue
 195   for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I)
 196     addLoopIntoQueue(*I, LQ);
 197
 198   if (LQ.empty()) // No loops, skip calling finalizers
 199     return false;
 200
 201   // Initialization
 202   for (std::deque<Loop *>::const_iterator I = LQ.begin(), E = LQ.end();
 203        I != E; ++I) {
 204     Loop *L = *I;
 205     for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
 206       Pass *P = getContainedPass(Index);
 207       LoopPass *LP = dynamic_cast<LoopPass *>(P);
 208       if (LP)
 209         Changed |= LP->doInitialization(L, *this);
 210     }
 211   }
 212
 213   // Walk Loops
 214   while (!LQ.empty()) {
 215
 216     CurrentLoop  = LQ.back();
 217     skipThisLoop = false;
 218     redoThisLoop = false;
 219
 220     // Run all passes on current SCC
 221     for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
 222       Pass *P = getContainedPass(Index);
 223
 224       dumpPassInfo(P, EXECUTION_MSG, ON_LOOP_MSG, "");
 225       dumpRequiredSet(P);
 226
 227       initializeAnalysisImpl(P);
 228
 229       LoopPass *LP = dynamic_cast<LoopPass *>(P);
 230       {
 231         PassManagerPrettyStackEntry X(LP, *CurrentLoop->getHeader());
 232         StartPassTimer(P);
 233         assert(LP && "Invalid LPPassManager member");
 234         Changed |= LP->runOnLoop(CurrentLoop, *this);
 235         StopPassTimer(P);
 236       }
 237
 238       if (Changed)
 239         dumpPassInfo(P, MODIFICATION_MSG, ON_LOOP_MSG, "");
 240       dumpPreservedSet(P);
 241
 242       if (!skipThisLoop)
 243         verifyPreservedAnalysis(LP);
 244
 245       removeNotPreservedAnalysis(P);
 246       recordAvailableAnalysis(P);
 247       removeDeadPasses(P, "", ON_LOOP_MSG);
 248
 249       // If dominator information is available then verify the info if requested.
 250       verifyDomInfo(*LP, F);
 251
 252       if (skipThisLoop)
 253         // Do not run other passes on this loop.
 254         break;
 255     }
 256
 257     // Pop the loop from queue after running all passes.
 258     LQ.pop_back();
 259
 260     if (redoThisLoop)
 261       LQ.push_back(CurrentLoop);
 262   }
 263
 264   // Finalization
 265   for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
 266     Pass *P = getContainedPass(Index);
 267     LoopPass *LP = dynamic_cast <LoopPass *>(P);
 268     if (LP)
 269       Changed |= LP->doFinalization();
 270   }
 271
 272   return Changed;
 273 }
 274
 275 /// Print passes managed by this manager
 276 void LPPassManager::dumpPassStructure(unsigned Offset) {
 277   errs().indent(Offset*2) << "Loop Pass Manager\n";
 278   for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) {
 279     Pass *P = getContainedPass(Index);
 280     P->dumpPassStructure(Offset + 1);
 281     dumpLastUses(P, Offset+1);
 282   }
 283 }
 284
 285
 286 //===----------------------------------------------------------------------===//
 287 // LoopPass
 288
 289 // Check if this pass is suitable for the current LPPassManager, if
 290 // available. This pass P is not suitable for a LPPassManager if P
 291 // is not preserving higher level analysis info used by other
 292 // LPPassManager passes. In such case, pop LPPassManager from the
 293 // stack. This will force assignPassManager() to create new
 294 // LPPassManger as expected.
 295 void LoopPass::preparePassManager(PMStack &PMS) {
 296
 297   // Find LPPassManager
 298   while (!PMS.empty() &&
 299          PMS.top()->getPassManagerType() > PMT_LoopPassManager)
 300     PMS.pop();
 301
 302   LPPassManager *LPPM = dynamic_cast<LPPassManager *>(PMS.top());
 303
 304   // If this pass is destroying high level information that is used
 305   // by other passes that are managed by LPM then do not insert
 306   // this pass in current LPM. Use new LPPassManager.
 307   if (LPPM && !LPPM->preserveHigherLevelAnalysis(this))
 308     PMS.pop();
 309 }
 310
 311 /// Assign pass manager to manage this pass.
 312 void LoopPass::assignPassManager(PMStack &PMS,
 313                                  PassManagerType PreferredType) {
 314   // Find LPPassManager
 315   while (!PMS.empty() &&
 316          PMS.top()->getPassManagerType() > PMT_LoopPassManager)
 317     PMS.pop();
 318
 319   LPPassManager *LPPM = dynamic_cast<LPPassManager *>(PMS.top());
 320
 321   // Create new Loop Pass Manager if it does not exist.
 322   if (!LPPM) {
 323
 324     assert (!PMS.empty() && "Unable to create Loop Pass Manager");
 325     PMDataManager *PMD = PMS.top();
 326
 327     // [1] Create new Call Graph Pass Manager
 328     LPPM = new LPPassManager(PMD->getDepth() + 1);
 329     LPPM->populateInheritedAnalysis(PMS);
 330
 331     // [2] Set up new manager's top level manager
 332     PMTopLevelManager *TPM = PMD->getTopLevelManager();
 333     TPM->addIndirectPassManager(LPPM);
 334
 335     // [3] Assign manager to manage this new manager. This may create
 336     // and push new managers into PMS
 337     Pass *P = dynamic_cast<Pass *>(LPPM);
 338     TPM->schedulePass(P);
 339
 340     // [4] Push new manager into PMS
 341     PMS.push(LPPM);
 342   }
 343
 344   LPPM->add(this);
 345 }