LoopPass.cpp revision 36b56886974eae4f9c5ebc96befd3e7bfe5de338
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/IR/IRPrintingPasses.h" 18#include "llvm/Support/Debug.h" 19#include "llvm/Support/Timer.h" 20using namespace llvm; 21 22namespace { 23 24/// PrintLoopPass - Print a Function corresponding to a Loop. 25/// 26class PrintLoopPass : public LoopPass { 27private: 28 std::string Banner; 29 raw_ostream &Out; // raw_ostream to print on. 30 31public: 32 static char ID; 33 PrintLoopPass(const std::string &B, raw_ostream &o) 34 : LoopPass(ID), Banner(B), Out(o) {} 35 36 void getAnalysisUsage(AnalysisUsage &AU) const override { 37 AU.setPreservesAll(); 38 } 39 40 bool runOnLoop(Loop *L, LPPassManager &) override { 41 Out << Banner; 42 for (Loop::block_iterator b = L->block_begin(), be = L->block_end(); 43 b != be; 44 ++b) { 45 (*b)->print(Out); 46 } 47 return false; 48 } 49}; 50 51char PrintLoopPass::ID = 0; 52} 53 54//===----------------------------------------------------------------------===// 55// LPPassManager 56// 57 58char LPPassManager::ID = 0; 59 60LPPassManager::LPPassManager() 61 : FunctionPass(ID), PMDataManager() { 62 skipThisLoop = false; 63 redoThisLoop = false; 64 LI = NULL; 65 CurrentLoop = NULL; 66} 67 68/// Delete loop from the loop queue and loop hierarchy (LoopInfo). 69void LPPassManager::deleteLoopFromQueue(Loop *L) { 70 71 LI->updateUnloop(L); 72 73 // If L is current loop then skip rest of the passes and let 74 // runOnFunction remove L from LQ. Otherwise, remove L from LQ now 75 // and continue applying other passes on CurrentLoop. 76 if (CurrentLoop == L) 77 skipThisLoop = true; 78 79 delete L; 80 81 if (skipThisLoop) 82 return; 83 84 for (std::deque<Loop *>::iterator I = LQ.begin(), 85 E = LQ.end(); I != E; ++I) { 86 if (*I == L) { 87 LQ.erase(I); 88 break; 89 } 90 } 91} 92 93// Inset loop into loop nest (LoopInfo) and loop queue (LQ). 94void LPPassManager::insertLoop(Loop *L, Loop *ParentLoop) { 95 96 assert (CurrentLoop != L && "Cannot insert CurrentLoop"); 97 98 // Insert into loop nest 99 if (ParentLoop) 100 ParentLoop->addChildLoop(L); 101 else 102 LI->addTopLevelLoop(L); 103 104 insertLoopIntoQueue(L); 105} 106 107void LPPassManager::insertLoopIntoQueue(Loop *L) { 108 // Insert L into loop queue 109 if (L == CurrentLoop) 110 redoLoop(L); 111 else if (!L->getParentLoop()) 112 // This is top level loop. 113 LQ.push_front(L); 114 else { 115 // Insert L after the parent loop. 116 for (std::deque<Loop *>::iterator I = LQ.begin(), 117 E = LQ.end(); I != E; ++I) { 118 if (*I == L->getParentLoop()) { 119 // deque does not support insert after. 120 ++I; 121 LQ.insert(I, 1, L); 122 break; 123 } 124 } 125 } 126} 127 128// Reoptimize this loop. LPPassManager will re-insert this loop into the 129// queue. This allows LoopPass to change loop nest for the loop. This 130// utility may send LPPassManager into infinite loops so use caution. 131void LPPassManager::redoLoop(Loop *L) { 132 assert (CurrentLoop == L && "Can redo only CurrentLoop"); 133 redoThisLoop = true; 134} 135 136/// cloneBasicBlockSimpleAnalysis - Invoke cloneBasicBlockAnalysis hook for 137/// all loop passes. 138void LPPassManager::cloneBasicBlockSimpleAnalysis(BasicBlock *From, 139 BasicBlock *To, Loop *L) { 140 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 141 LoopPass *LP = getContainedPass(Index); 142 LP->cloneBasicBlockAnalysis(From, To, L); 143 } 144} 145 146/// deleteSimpleAnalysisValue - Invoke deleteAnalysisValue hook for all passes. 147void LPPassManager::deleteSimpleAnalysisValue(Value *V, Loop *L) { 148 if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) { 149 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE; 150 ++BI) { 151 Instruction &I = *BI; 152 deleteSimpleAnalysisValue(&I, L); 153 } 154 } 155 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 156 LoopPass *LP = getContainedPass(Index); 157 LP->deleteAnalysisValue(V, L); 158 } 159} 160 161 162// Recurse through all subloops and all loops into LQ. 163static void addLoopIntoQueue(Loop *L, std::deque<Loop *> &LQ) { 164 LQ.push_back(L); 165 for (Loop::reverse_iterator I = L->rbegin(), E = L->rend(); I != E; ++I) 166 addLoopIntoQueue(*I, LQ); 167} 168 169/// Pass Manager itself does not invalidate any analysis info. 170void LPPassManager::getAnalysisUsage(AnalysisUsage &Info) const { 171 // LPPassManager needs LoopInfo. In the long term LoopInfo class will 172 // become part of LPPassManager. 173 Info.addRequired<LoopInfo>(); 174 Info.setPreservesAll(); 175} 176 177/// run - Execute all of the passes scheduled for execution. Keep track of 178/// whether any of the passes modifies the function, and if so, return true. 179bool LPPassManager::runOnFunction(Function &F) { 180 LI = &getAnalysis<LoopInfo>(); 181 bool Changed = false; 182 183 // Collect inherited analysis from Module level pass manager. 184 populateInheritedAnalysis(TPM->activeStack); 185 186 // Populate the loop queue in reverse program order. There is no clear need to 187 // process sibling loops in either forward or reverse order. There may be some 188 // advantage in deleting uses in a later loop before optimizing the 189 // definitions in an earlier loop. If we find a clear reason to process in 190 // forward order, then a forward variant of LoopPassManager should be created. 191 // 192 // Note that LoopInfo::iterator visits loops in reverse program 193 // order. Here, reverse_iterator gives us a forward order, and the LoopQueue 194 // reverses the order a third time by popping from the back. 195 for (LoopInfo::reverse_iterator I = LI->rbegin(), E = LI->rend(); 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 LoopPass *P = getContainedPass(Index); 207 Changed |= P->doInitialization(L, *this); 208 } 209 } 210 211 // Walk Loops 212 while (!LQ.empty()) { 213 214 CurrentLoop = LQ.back(); 215 skipThisLoop = false; 216 redoThisLoop = false; 217 218 // Run all passes on the current Loop. 219 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 220 LoopPass *P = getContainedPass(Index); 221 222 dumpPassInfo(P, EXECUTION_MSG, ON_LOOP_MSG, 223 CurrentLoop->getHeader()->getName()); 224 dumpRequiredSet(P); 225 226 initializeAnalysisImpl(P); 227 228 { 229 PassManagerPrettyStackEntry X(P, *CurrentLoop->getHeader()); 230 TimeRegion PassTimer(getPassTimer(P)); 231 232 Changed |= P->runOnLoop(CurrentLoop, *this); 233 } 234 235 if (Changed) 236 dumpPassInfo(P, MODIFICATION_MSG, ON_LOOP_MSG, 237 skipThisLoop ? "<deleted>" : 238 CurrentLoop->getHeader()->getName()); 239 dumpPreservedSet(P); 240 241 if (!skipThisLoop) { 242 // Manually check that this loop is still healthy. This is done 243 // instead of relying on LoopInfo::verifyLoop since LoopInfo 244 // is a function pass and it's really expensive to verify every 245 // loop in the function every time. That level of checking can be 246 // enabled with the -verify-loop-info option. 247 { 248 TimeRegion PassTimer(getPassTimer(LI)); 249 CurrentLoop->verifyLoop(); 250 } 251 252 // Then call the regular verifyAnalysis functions. 253 verifyPreservedAnalysis(P); 254 } 255 256 removeNotPreservedAnalysis(P); 257 recordAvailableAnalysis(P); 258 removeDeadPasses(P, 259 skipThisLoop ? "<deleted>" : 260 CurrentLoop->getHeader()->getName(), 261 ON_LOOP_MSG); 262 263 if (skipThisLoop) 264 // Do not run other passes on this loop. 265 break; 266 } 267 268 // If the loop was deleted, release all the loop passes. This frees up 269 // some memory, and avoids trouble with the pass manager trying to call 270 // verifyAnalysis on them. 271 if (skipThisLoop) 272 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 273 Pass *P = getContainedPass(Index); 274 freePass(P, "<deleted>", ON_LOOP_MSG); 275 } 276 277 // Pop the loop from queue after running all passes. 278 LQ.pop_back(); 279 280 if (redoThisLoop) 281 LQ.push_back(CurrentLoop); 282 } 283 284 // Finalization 285 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 286 LoopPass *P = getContainedPass(Index); 287 Changed |= P->doFinalization(); 288 } 289 290 return Changed; 291} 292 293/// Print passes managed by this manager 294void LPPassManager::dumpPassStructure(unsigned Offset) { 295 errs().indent(Offset*2) << "Loop Pass Manager\n"; 296 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 297 Pass *P = getContainedPass(Index); 298 P->dumpPassStructure(Offset + 1); 299 dumpLastUses(P, Offset+1); 300 } 301} 302 303 304//===----------------------------------------------------------------------===// 305// LoopPass 306 307Pass *LoopPass::createPrinterPass(raw_ostream &O, 308 const std::string &Banner) const { 309 return new PrintLoopPass(Banner, O); 310} 311 312// Check if this pass is suitable for the current LPPassManager, if 313// available. This pass P is not suitable for a LPPassManager if P 314// is not preserving higher level analysis info used by other 315// LPPassManager passes. In such case, pop LPPassManager from the 316// stack. This will force assignPassManager() to create new 317// LPPassManger as expected. 318void LoopPass::preparePassManager(PMStack &PMS) { 319 320 // Find LPPassManager 321 while (!PMS.empty() && 322 PMS.top()->getPassManagerType() > PMT_LoopPassManager) 323 PMS.pop(); 324 325 // If this pass is destroying high level information that is used 326 // by other passes that are managed by LPM then do not insert 327 // this pass in current LPM. Use new LPPassManager. 328 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager && 329 !PMS.top()->preserveHigherLevelAnalysis(this)) 330 PMS.pop(); 331} 332 333/// Assign pass manager to manage this pass. 334void LoopPass::assignPassManager(PMStack &PMS, 335 PassManagerType PreferredType) { 336 // Find LPPassManager 337 while (!PMS.empty() && 338 PMS.top()->getPassManagerType() > PMT_LoopPassManager) 339 PMS.pop(); 340 341 LPPassManager *LPPM; 342 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager) 343 LPPM = (LPPassManager*)PMS.top(); 344 else { 345 // Create new Loop Pass Manager if it does not exist. 346 assert (!PMS.empty() && "Unable to create Loop Pass Manager"); 347 PMDataManager *PMD = PMS.top(); 348 349 // [1] Create new Loop Pass Manager 350 LPPM = new LPPassManager(); 351 LPPM->populateInheritedAnalysis(PMS); 352 353 // [2] Set up new manager's top level manager 354 PMTopLevelManager *TPM = PMD->getTopLevelManager(); 355 TPM->addIndirectPassManager(LPPM); 356 357 // [3] Assign manager to manage this new manager. This may create 358 // and push new managers into PMS 359 Pass *P = LPPM->getAsPass(); 360 TPM->schedulePass(P); 361 362 // [4] Push new manager into PMS 363 PMS.push(LPPM); 364 } 365 366 LPPM->add(this); 367} 368 369// Containing function has Attribute::OptimizeNone and transformation 370// passes should skip it. 371bool LoopPass::skipOptnoneFunction(const Loop *L) const { 372 const Function *F = L->getHeader()->getParent(); 373 if (F && F->hasFnAttribute(Attribute::OptimizeNone)) { 374 // FIXME: Report this to dbgs() only once per function. 375 DEBUG(dbgs() << "Skipping pass '" << getPassName() 376 << "' in function " << F->getName() << "\n"); 377 // FIXME: Delete loop from pass manager's queue? 378 return true; 379 } 380 return false; 381} 382