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/IR/LLVMContext.h" 19 #include "llvm/Support/Debug.h" 20 #include "llvm/Support/Timer.h" 21 using namespace llvm; 22 23 #define DEBUG_TYPE "loop-pass-manager" 24 25 namespace { 26 27 /// PrintLoopPass - Print a Function corresponding to a Loop. 28 /// 29 class PrintLoopPass : public LoopPass { 30 private: 31 std::string Banner; 32 raw_ostream &Out; // raw_ostream to print on. 33 34 public: 35 static char ID; 36 PrintLoopPass(const std::string &B, raw_ostream &o) 37 : LoopPass(ID), Banner(B), Out(o) {} 38 39 void getAnalysisUsage(AnalysisUsage &AU) const override { 40 AU.setPreservesAll(); 41 } 42 43 bool runOnLoop(Loop *L, LPPassManager &) override { 44 Out << Banner; 45 for (Loop::block_iterator b = L->block_begin(), be = L->block_end(); 46 b != be; 47 ++b) { 48 if (*b) 49 (*b)->print(Out); 50 else 51 Out << "Printing <null> block"; 52 } 53 return false; 54 } 55 }; 56 57 char PrintLoopPass::ID = 0; 58 } 59 60 //===----------------------------------------------------------------------===// 61 // LPPassManager 62 // 63 64 char LPPassManager::ID = 0; 65 66 LPPassManager::LPPassManager() 67 : FunctionPass(ID), PMDataManager() { 68 skipThisLoop = false; 69 redoThisLoop = false; 70 LI = nullptr; 71 CurrentLoop = nullptr; 72 } 73 74 /// Delete loop from the loop queue and loop hierarchy (LoopInfo). 75 void LPPassManager::deleteLoopFromQueue(Loop *L) { 76 77 LI->updateUnloop(L); 78 79 // If L is current loop then skip rest of the passes and let 80 // runOnFunction remove L from LQ. Otherwise, remove L from LQ now 81 // and continue applying other passes on CurrentLoop. 82 if (CurrentLoop == L) 83 skipThisLoop = true; 84 85 delete L; 86 87 if (skipThisLoop) 88 return; 89 90 for (std::deque<Loop *>::iterator I = LQ.begin(), 91 E = LQ.end(); I != E; ++I) { 92 if (*I == L) { 93 LQ.erase(I); 94 break; 95 } 96 } 97 } 98 99 // Inset loop into loop nest (LoopInfo) and loop queue (LQ). 100 void LPPassManager::insertLoop(Loop *L, Loop *ParentLoop) { 101 102 assert (CurrentLoop != L && "Cannot insert CurrentLoop"); 103 104 // Insert into loop nest 105 if (ParentLoop) 106 ParentLoop->addChildLoop(L); 107 else 108 LI->addTopLevelLoop(L); 109 110 insertLoopIntoQueue(L); 111 } 112 113 void LPPassManager::insertLoopIntoQueue(Loop *L) { 114 // Insert L into loop queue 115 if (L == CurrentLoop) 116 redoLoop(L); 117 else if (!L->getParentLoop()) 118 // This is top level loop. 119 LQ.push_front(L); 120 else { 121 // Insert L after the parent loop. 122 for (std::deque<Loop *>::iterator I = LQ.begin(), 123 E = LQ.end(); I != E; ++I) { 124 if (*I == L->getParentLoop()) { 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 LoopPass *LP = getContainedPass(Index); 148 LP->cloneBasicBlockAnalysis(From, To, L); 149 } 150 } 151 152 /// deleteSimpleAnalysisValue - Invoke deleteAnalysisValue hook for all passes. 153 void LPPassManager::deleteSimpleAnalysisValue(Value *V, Loop *L) { 154 if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) { 155 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE; 156 ++BI) { 157 Instruction &I = *BI; 158 deleteSimpleAnalysisValue(&I, L); 159 } 160 } 161 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 162 LoopPass *LP = getContainedPass(Index); 163 LP->deleteAnalysisValue(V, L); 164 } 165 } 166 167 168 // Recurse through all subloops and all loops into LQ. 169 static void addLoopIntoQueue(Loop *L, std::deque<Loop *> &LQ) { 170 LQ.push_back(L); 171 for (Loop::reverse_iterator I = L->rbegin(), E = L->rend(); I != E; ++I) 172 addLoopIntoQueue(*I, LQ); 173 } 174 175 /// Pass Manager itself does not invalidate any analysis info. 176 void LPPassManager::getAnalysisUsage(AnalysisUsage &Info) const { 177 // LPPassManager needs LoopInfo. In the long term LoopInfo class will 178 // become part of LPPassManager. 179 Info.addRequired<LoopInfo>(); 180 Info.setPreservesAll(); 181 } 182 183 /// run - Execute all of the passes scheduled for execution. Keep track of 184 /// whether any of the passes modifies the function, and if so, return true. 185 bool LPPassManager::runOnFunction(Function &F) { 186 LI = &getAnalysis<LoopInfo>(); 187 bool Changed = false; 188 189 // Collect inherited analysis from Module level pass manager. 190 populateInheritedAnalysis(TPM->activeStack); 191 192 // Populate the loop queue in reverse program order. There is no clear need to 193 // process sibling loops in either forward or reverse order. There may be some 194 // advantage in deleting uses in a later loop before optimizing the 195 // definitions in an earlier loop. If we find a clear reason to process in 196 // forward order, then a forward variant of LoopPassManager should be created. 197 // 198 // Note that LoopInfo::iterator visits loops in reverse program 199 // order. Here, reverse_iterator gives us a forward order, and the LoopQueue 200 // reverses the order a third time by popping from the back. 201 for (LoopInfo::reverse_iterator I = LI->rbegin(), E = LI->rend(); I != E; ++I) 202 addLoopIntoQueue(*I, LQ); 203 204 if (LQ.empty()) // No loops, skip calling finalizers 205 return false; 206 207 // Initialization 208 for (std::deque<Loop *>::const_iterator I = LQ.begin(), E = LQ.end(); 209 I != E; ++I) { 210 Loop *L = *I; 211 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 212 LoopPass *P = getContainedPass(Index); 213 Changed |= P->doInitialization(L, *this); 214 } 215 } 216 217 // Walk Loops 218 while (!LQ.empty()) { 219 220 CurrentLoop = LQ.back(); 221 skipThisLoop = false; 222 redoThisLoop = false; 223 224 // Run all passes on the current Loop. 225 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 226 LoopPass *P = getContainedPass(Index); 227 228 dumpPassInfo(P, EXECUTION_MSG, ON_LOOP_MSG, 229 CurrentLoop->getHeader()->getName()); 230 dumpRequiredSet(P); 231 232 initializeAnalysisImpl(P); 233 234 { 235 PassManagerPrettyStackEntry X(P, *CurrentLoop->getHeader()); 236 TimeRegion PassTimer(getPassTimer(P)); 237 238 Changed |= P->runOnLoop(CurrentLoop, *this); 239 } 240 241 if (Changed) 242 dumpPassInfo(P, MODIFICATION_MSG, ON_LOOP_MSG, 243 skipThisLoop ? "<deleted>" : 244 CurrentLoop->getHeader()->getName()); 245 dumpPreservedSet(P); 246 247 if (!skipThisLoop) { 248 // Manually check that this loop is still healthy. This is done 249 // instead of relying on LoopInfo::verifyLoop since LoopInfo 250 // is a function pass and it's really expensive to verify every 251 // loop in the function every time. That level of checking can be 252 // enabled with the -verify-loop-info option. 253 { 254 TimeRegion PassTimer(getPassTimer(LI)); 255 CurrentLoop->verifyLoop(); 256 } 257 258 // Then call the regular verifyAnalysis functions. 259 verifyPreservedAnalysis(P); 260 261 F.getContext().yield(); 262 } 263 264 removeNotPreservedAnalysis(P); 265 recordAvailableAnalysis(P); 266 removeDeadPasses(P, 267 skipThisLoop ? "<deleted>" : 268 CurrentLoop->getHeader()->getName(), 269 ON_LOOP_MSG); 270 271 if (skipThisLoop) 272 // Do not run other passes on this loop. 273 break; 274 } 275 276 // If the loop was deleted, release all the loop passes. This frees up 277 // some memory, and avoids trouble with the pass manager trying to call 278 // verifyAnalysis on them. 279 if (skipThisLoop) 280 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 281 Pass *P = getContainedPass(Index); 282 freePass(P, "<deleted>", ON_LOOP_MSG); 283 } 284 285 // Pop the loop from queue after running all passes. 286 LQ.pop_back(); 287 288 if (redoThisLoop) 289 LQ.push_back(CurrentLoop); 290 } 291 292 // Finalization 293 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 294 LoopPass *P = getContainedPass(Index); 295 Changed |= P->doFinalization(); 296 } 297 298 return Changed; 299 } 300 301 /// Print passes managed by this manager 302 void LPPassManager::dumpPassStructure(unsigned Offset) { 303 errs().indent(Offset*2) << "Loop Pass Manager\n"; 304 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 305 Pass *P = getContainedPass(Index); 306 P->dumpPassStructure(Offset + 1); 307 dumpLastUses(P, Offset+1); 308 } 309 } 310 311 312 //===----------------------------------------------------------------------===// 313 // LoopPass 314 315 Pass *LoopPass::createPrinterPass(raw_ostream &O, 316 const std::string &Banner) const { 317 return new PrintLoopPass(Banner, O); 318 } 319 320 // Check if this pass is suitable for the current LPPassManager, if 321 // available. This pass P is not suitable for a LPPassManager if P 322 // is not preserving higher level analysis info used by other 323 // LPPassManager passes. In such case, pop LPPassManager from the 324 // stack. This will force assignPassManager() to create new 325 // LPPassManger as expected. 326 void LoopPass::preparePassManager(PMStack &PMS) { 327 328 // Find LPPassManager 329 while (!PMS.empty() && 330 PMS.top()->getPassManagerType() > PMT_LoopPassManager) 331 PMS.pop(); 332 333 // If this pass is destroying high level information that is used 334 // by other passes that are managed by LPM then do not insert 335 // this pass in current LPM. Use new LPPassManager. 336 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager && 337 !PMS.top()->preserveHigherLevelAnalysis(this)) 338 PMS.pop(); 339 } 340 341 /// Assign pass manager to manage this pass. 342 void LoopPass::assignPassManager(PMStack &PMS, 343 PassManagerType PreferredType) { 344 // Find LPPassManager 345 while (!PMS.empty() && 346 PMS.top()->getPassManagerType() > PMT_LoopPassManager) 347 PMS.pop(); 348 349 LPPassManager *LPPM; 350 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager) 351 LPPM = (LPPassManager*)PMS.top(); 352 else { 353 // Create new Loop Pass Manager if it does not exist. 354 assert (!PMS.empty() && "Unable to create Loop Pass Manager"); 355 PMDataManager *PMD = PMS.top(); 356 357 // [1] Create new Loop Pass Manager 358 LPPM = new LPPassManager(); 359 LPPM->populateInheritedAnalysis(PMS); 360 361 // [2] Set up new manager's top level manager 362 PMTopLevelManager *TPM = PMD->getTopLevelManager(); 363 TPM->addIndirectPassManager(LPPM); 364 365 // [3] Assign manager to manage this new manager. This may create 366 // and push new managers into PMS 367 Pass *P = LPPM->getAsPass(); 368 TPM->schedulePass(P); 369 370 // [4] Push new manager into PMS 371 PMS.push(LPPM); 372 } 373 374 LPPM->add(this); 375 } 376 377 // Containing function has Attribute::OptimizeNone and transformation 378 // passes should skip it. 379 bool LoopPass::skipOptnoneFunction(const Loop *L) const { 380 const Function *F = L->getHeader()->getParent(); 381 if (F && F->hasFnAttribute(Attribute::OptimizeNone)) { 382 // FIXME: Report this to dbgs() only once per function. 383 DEBUG(dbgs() << "Skipping pass '" << getPassName() 384 << "' in function " << F->getName() << "\n"); 385 // FIXME: Delete loop from pass manager's queue? 386 return true; 387 } 388 return false; 389 } 390