LoopPass.cpp revision 1f74590e9d1b9cf0f1f81a156efea73f76546e05
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/Assembly/PrintModulePass.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() : LoopPass(&ID), Out(dbgs()) {} 34 PrintLoopPass(const std::string &B, raw_ostream &o) 35 : LoopPass(&ID), Banner(B), Out(o) {} 36 37 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 38 AU.setPreservesAll(); 39 } 40 41 bool runOnLoop(Loop *L, LPPassManager &) { 42 Out << Banner; 43 for (Loop::block_iterator b = L->block_begin(), be = L->block_end(); 44 b != be; 45 ++b) { 46 (*b)->print(Out); 47 } 48 return false; 49 } 50}; 51 52char PrintLoopPass::ID = 0; 53} 54 55//===----------------------------------------------------------------------===// 56// LPPassManager 57// 58 59char LPPassManager::ID = 0; 60 61LPPassManager::LPPassManager(int Depth) 62 : FunctionPass(&ID), PMDataManager(Depth) { 63 skipThisLoop = false; 64 redoThisLoop = false; 65 LI = NULL; 66 CurrentLoop = NULL; 67} 68 69/// Delete loop from the loop queue and loop hierarchy (LoopInfo). 70void LPPassManager::deleteLoopFromQueue(Loop *L) { 71 72 if (Loop *ParentLoop = L->getParentLoop()) { // Not a top-level loop. 73 // Reparent all of the blocks in this loop. Since BBLoop had a parent, 74 // they are now all in it. 75 for (Loop::block_iterator I = L->block_begin(), E = L->block_end(); 76 I != E; ++I) 77 if (LI->getLoopFor(*I) == L) // Don't change blocks in subloops. 78 LI->changeLoopFor(*I, ParentLoop); 79 80 // Remove the loop from its parent loop. 81 for (Loop::iterator I = ParentLoop->begin(), E = ParentLoop->end();; 82 ++I) { 83 assert(I != E && "Couldn't find loop"); 84 if (*I == L) { 85 ParentLoop->removeChildLoop(I); 86 break; 87 } 88 } 89 90 // Move all subloops into the parent loop. 91 while (!L->empty()) 92 ParentLoop->addChildLoop(L->removeChildLoop(L->end()-1)); 93 } else { 94 // Reparent all of the blocks in this loop. Since BBLoop had no parent, 95 // they no longer in a loop at all. 96 97 for (unsigned i = 0; i != L->getBlocks().size(); ++i) { 98 // Don't change blocks in subloops. 99 if (LI->getLoopFor(L->getBlocks()[i]) == L) { 100 LI->removeBlock(L->getBlocks()[i]); 101 --i; 102 } 103 } 104 105 // Remove the loop from the top-level LoopInfo object. 106 for (LoopInfo::iterator I = LI->begin(), E = LI->end();; ++I) { 107 assert(I != E && "Couldn't find loop"); 108 if (*I == L) { 109 LI->removeLoop(I); 110 break; 111 } 112 } 113 114 // Move all of the subloops to the top-level. 115 while (!L->empty()) 116 LI->addTopLevelLoop(L->removeChildLoop(L->end()-1)); 117 } 118 119 delete L; 120 121 // If L is current loop then skip rest of the passes and let 122 // runOnFunction remove L from LQ. Otherwise, remove L from LQ now 123 // and continue applying other passes on CurrentLoop. 124 if (CurrentLoop == L) { 125 skipThisLoop = true; 126 return; 127 } 128 129 for (std::deque<Loop *>::iterator I = LQ.begin(), 130 E = LQ.end(); I != E; ++I) { 131 if (*I == L) { 132 LQ.erase(I); 133 break; 134 } 135 } 136} 137 138// Inset loop into loop nest (LoopInfo) and loop queue (LQ). 139void LPPassManager::insertLoop(Loop *L, Loop *ParentLoop) { 140 141 assert (CurrentLoop != L && "Cannot insert CurrentLoop"); 142 143 // Insert into loop nest 144 if (ParentLoop) 145 ParentLoop->addChildLoop(L); 146 else 147 LI->addTopLevelLoop(L); 148 149 insertLoopIntoQueue(L); 150} 151 152void LPPassManager::insertLoopIntoQueue(Loop *L) { 153 // Insert L into loop queue 154 if (L == CurrentLoop) 155 redoLoop(L); 156 else if (!L->getParentLoop()) 157 // This is top level loop. 158 LQ.push_front(L); 159 else { 160 // Insert L after the parent loop. 161 for (std::deque<Loop *>::iterator I = LQ.begin(), 162 E = LQ.end(); I != E; ++I) { 163 if (*I == L->getParentLoop()) { 164 // deque does not support insert after. 165 ++I; 166 LQ.insert(I, 1, L); 167 break; 168 } 169 } 170 } 171} 172 173// Reoptimize this loop. LPPassManager will re-insert this loop into the 174// queue. This allows LoopPass to change loop nest for the loop. This 175// utility may send LPPassManager into infinite loops so use caution. 176void LPPassManager::redoLoop(Loop *L) { 177 assert (CurrentLoop == L && "Can redo only CurrentLoop"); 178 redoThisLoop = true; 179} 180 181/// cloneBasicBlockSimpleAnalysis - Invoke cloneBasicBlockAnalysis hook for 182/// all loop passes. 183void LPPassManager::cloneBasicBlockSimpleAnalysis(BasicBlock *From, 184 BasicBlock *To, Loop *L) { 185 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 186 LoopPass *LP = (LoopPass *)getContainedPass(Index); 187 LP->cloneBasicBlockAnalysis(From, To, L); 188 } 189} 190 191/// deleteSimpleAnalysisValue - Invoke deleteAnalysisValue hook for all passes. 192void LPPassManager::deleteSimpleAnalysisValue(Value *V, Loop *L) { 193 if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) { 194 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE; 195 ++BI) { 196 Instruction &I = *BI; 197 deleteSimpleAnalysisValue(&I, L); 198 } 199 } 200 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 201 LoopPass *LP = (LoopPass *)getContainedPass(Index); 202 LP->deleteAnalysisValue(V, L); 203 } 204} 205 206 207// Recurse through all subloops and all loops into LQ. 208static void addLoopIntoQueue(Loop *L, std::deque<Loop *> &LQ) { 209 LQ.push_back(L); 210 for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I) 211 addLoopIntoQueue(*I, LQ); 212} 213 214/// Pass Manager itself does not invalidate any analysis info. 215void LPPassManager::getAnalysisUsage(AnalysisUsage &Info) const { 216 // LPPassManager needs LoopInfo. In the long term LoopInfo class will 217 // become part of LPPassManager. 218 Info.addRequired<LoopInfo>(); 219 Info.setPreservesAll(); 220} 221 222/// run - Execute all of the passes scheduled for execution. Keep track of 223/// whether any of the passes modifies the function, and if so, return true. 224bool LPPassManager::runOnFunction(Function &F) { 225 LI = &getAnalysis<LoopInfo>(); 226 bool Changed = false; 227 228 // Collect inherited analysis from Module level pass manager. 229 populateInheritedAnalysis(TPM->activeStack); 230 231 // Populate Loop Queue 232 for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I) 233 addLoopIntoQueue(*I, LQ); 234 235 if (LQ.empty()) // No loops, skip calling finalizers 236 return false; 237 238 // Initialization 239 for (std::deque<Loop *>::const_iterator I = LQ.begin(), E = LQ.end(); 240 I != E; ++I) { 241 Loop *L = *I; 242 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 243 LoopPass *P = (LoopPass*)getContainedPass(Index); 244 Changed |= P->doInitialization(L, *this); 245 } 246 } 247 248 // Walk Loops 249 while (!LQ.empty()) { 250 251 CurrentLoop = LQ.back(); 252 skipThisLoop = false; 253 redoThisLoop = false; 254 255 // Run all passes on the current Loop. 256 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 257 LoopPass *P = (LoopPass*)getContainedPass(Index); 258 259 dumpPassInfo(P, EXECUTION_MSG, ON_LOOP_MSG, 260 CurrentLoop->getHeader()->getName()); 261 dumpRequiredSet(P); 262 263 initializeAnalysisImpl(P); 264 265 { 266 PassManagerPrettyStackEntry X(P, *CurrentLoop->getHeader()); 267 TimeRegion PassTimer(getPassTimer(P)); 268 269 Changed |= P->runOnLoop(CurrentLoop, *this); 270 } 271 272 if (Changed) 273 dumpPassInfo(P, MODIFICATION_MSG, ON_LOOP_MSG, 274 skipThisLoop ? "<deleted>" : 275 CurrentLoop->getHeader()->getName()); 276 dumpPreservedSet(P); 277 278 if (!skipThisLoop) { 279 // Manually check that this loop is still healthy. This is done 280 // instead of relying on LoopInfo::verifyLoop since LoopInfo 281 // is a function pass and it's really expensive to verify every 282 // loop in the function every time. That level of checking can be 283 // enabled with the -verify-loop-info option. 284 { 285 TimeRegion PassTimer(getPassTimer(LI)); 286 CurrentLoop->verifyLoop(); 287 } 288 289 // Then call the regular verifyAnalysis functions. 290 verifyPreservedAnalysis(P); 291 } 292 293 removeNotPreservedAnalysis(P); 294 recordAvailableAnalysis(P); 295 removeDeadPasses(P, 296 skipThisLoop ? "<deleted>" : 297 CurrentLoop->getHeader()->getName(), 298 ON_LOOP_MSG); 299 300 if (skipThisLoop) 301 // Do not run other passes on this loop. 302 break; 303 } 304 305 // If the loop was deleted, release all the loop passes. This frees up 306 // some memory, and avoids trouble with the pass manager trying to call 307 // verifyAnalysis on them. 308 if (skipThisLoop) 309 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 310 Pass *P = getContainedPass(Index); 311 freePass(P, "<deleted>", ON_LOOP_MSG); 312 } 313 314 // Pop the loop from queue after running all passes. 315 LQ.pop_back(); 316 317 if (redoThisLoop) 318 LQ.push_back(CurrentLoop); 319 } 320 321 // Finalization 322 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 323 LoopPass *P = (LoopPass *)getContainedPass(Index); 324 Changed |= P->doFinalization(); 325 } 326 327 return Changed; 328} 329 330/// Print passes managed by this manager 331void LPPassManager::dumpPassStructure(unsigned Offset) { 332 errs().indent(Offset*2) << "Loop Pass Manager\n"; 333 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 334 Pass *P = getContainedPass(Index); 335 P->dumpPassStructure(Offset + 1); 336 dumpLastUses(P, Offset+1); 337 } 338} 339 340 341//===----------------------------------------------------------------------===// 342// LoopPass 343 344Pass *LoopPass::createPrinterPass(raw_ostream &O, 345 const std::string &Banner) const { 346 return new PrintLoopPass(Banner, O); 347} 348 349// Check if this pass is suitable for the current LPPassManager, if 350// available. This pass P is not suitable for a LPPassManager if P 351// is not preserving higher level analysis info used by other 352// LPPassManager passes. In such case, pop LPPassManager from the 353// stack. This will force assignPassManager() to create new 354// LPPassManger as expected. 355void LoopPass::preparePassManager(PMStack &PMS) { 356 357 // Find LPPassManager 358 while (!PMS.empty() && 359 PMS.top()->getPassManagerType() > PMT_LoopPassManager) 360 PMS.pop(); 361 362 // If this pass is destroying high level information that is used 363 // by other passes that are managed by LPM then do not insert 364 // this pass in current LPM. Use new LPPassManager. 365 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager && 366 !PMS.top()->preserveHigherLevelAnalysis(this)) 367 PMS.pop(); 368} 369 370/// Assign pass manager to manage this pass. 371void LoopPass::assignPassManager(PMStack &PMS, 372 PassManagerType PreferredType) { 373 // Find LPPassManager 374 while (!PMS.empty() && 375 PMS.top()->getPassManagerType() > PMT_LoopPassManager) 376 PMS.pop(); 377 378 LPPassManager *LPPM; 379 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager) 380 LPPM = (LPPassManager*)PMS.top(); 381 else { 382 // Create new Loop Pass Manager if it does not exist. 383 assert (!PMS.empty() && "Unable to create Loop Pass Manager"); 384 PMDataManager *PMD = PMS.top(); 385 386 // [1] Create new Call Graph Pass Manager 387 LPPM = new LPPassManager(PMD->getDepth() + 1); 388 LPPM->populateInheritedAnalysis(PMS); 389 390 // [2] Set up new manager's top level manager 391 PMTopLevelManager *TPM = PMD->getTopLevelManager(); 392 TPM->addIndirectPassManager(LPPM); 393 394 // [3] Assign manager to manage this new manager. This may create 395 // and push new managers into PMS 396 Pass *P = LPPM->getAsPass(); 397 TPM->schedulePass(P); 398 399 // [4] Push new manager into PMS 400 PMS.push(LPPM); 401 } 402 403 LPPM->add(this); 404} 405