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