LoopPass.cpp revision dce4a407a24b04eebc6a376f8e62b41aaa7b071f
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" 21using namespace llvm; 22 23#define DEBUG_TYPE "loop-pass-manager" 24 25namespace { 26 27/// PrintLoopPass - Print a Function corresponding to a Loop. 28/// 29class PrintLoopPass : public LoopPass { 30private: 31 std::string Banner; 32 raw_ostream &Out; // raw_ostream to print on. 33 34public: 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 (*b)->print(Out); 49 } 50 return false; 51 } 52}; 53 54char PrintLoopPass::ID = 0; 55} 56 57//===----------------------------------------------------------------------===// 58// LPPassManager 59// 60 61char LPPassManager::ID = 0; 62 63LPPassManager::LPPassManager() 64 : FunctionPass(ID), PMDataManager() { 65 skipThisLoop = false; 66 redoThisLoop = false; 67 LI = nullptr; 68 CurrentLoop = nullptr; 69} 70 71/// Delete loop from the loop queue and loop hierarchy (LoopInfo). 72void LPPassManager::deleteLoopFromQueue(Loop *L) { 73 74 LI->updateUnloop(L); 75 76 // If L is current loop then skip rest of the passes and let 77 // runOnFunction remove L from LQ. Otherwise, remove L from LQ now 78 // and continue applying other passes on CurrentLoop. 79 if (CurrentLoop == L) 80 skipThisLoop = true; 81 82 delete L; 83 84 if (skipThisLoop) 85 return; 86 87 for (std::deque<Loop *>::iterator I = LQ.begin(), 88 E = LQ.end(); I != E; ++I) { 89 if (*I == L) { 90 LQ.erase(I); 91 break; 92 } 93 } 94} 95 96// Inset loop into loop nest (LoopInfo) and loop queue (LQ). 97void LPPassManager::insertLoop(Loop *L, Loop *ParentLoop) { 98 99 assert (CurrentLoop != L && "Cannot insert CurrentLoop"); 100 101 // Insert into loop nest 102 if (ParentLoop) 103 ParentLoop->addChildLoop(L); 104 else 105 LI->addTopLevelLoop(L); 106 107 insertLoopIntoQueue(L); 108} 109 110void LPPassManager::insertLoopIntoQueue(Loop *L) { 111 // Insert L into loop queue 112 if (L == CurrentLoop) 113 redoLoop(L); 114 else if (!L->getParentLoop()) 115 // This is top level loop. 116 LQ.push_front(L); 117 else { 118 // Insert L after the parent loop. 119 for (std::deque<Loop *>::iterator I = LQ.begin(), 120 E = LQ.end(); I != E; ++I) { 121 if (*I == L->getParentLoop()) { 122 // deque does not support insert after. 123 ++I; 124 LQ.insert(I, 1, L); 125 break; 126 } 127 } 128 } 129} 130 131// Reoptimize this loop. LPPassManager will re-insert this loop into the 132// queue. This allows LoopPass to change loop nest for the loop. This 133// utility may send LPPassManager into infinite loops so use caution. 134void LPPassManager::redoLoop(Loop *L) { 135 assert (CurrentLoop == L && "Can redo only CurrentLoop"); 136 redoThisLoop = true; 137} 138 139/// cloneBasicBlockSimpleAnalysis - Invoke cloneBasicBlockAnalysis hook for 140/// all loop passes. 141void LPPassManager::cloneBasicBlockSimpleAnalysis(BasicBlock *From, 142 BasicBlock *To, Loop *L) { 143 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 144 LoopPass *LP = getContainedPass(Index); 145 LP->cloneBasicBlockAnalysis(From, To, L); 146 } 147} 148 149/// deleteSimpleAnalysisValue - Invoke deleteAnalysisValue hook for all passes. 150void LPPassManager::deleteSimpleAnalysisValue(Value *V, Loop *L) { 151 if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) { 152 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE; 153 ++BI) { 154 Instruction &I = *BI; 155 deleteSimpleAnalysisValue(&I, L); 156 } 157 } 158 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 159 LoopPass *LP = getContainedPass(Index); 160 LP->deleteAnalysisValue(V, L); 161 } 162} 163 164 165// Recurse through all subloops and all loops into LQ. 166static void addLoopIntoQueue(Loop *L, std::deque<Loop *> &LQ) { 167 LQ.push_back(L); 168 for (Loop::reverse_iterator I = L->rbegin(), E = L->rend(); I != E; ++I) 169 addLoopIntoQueue(*I, LQ); 170} 171 172/// Pass Manager itself does not invalidate any analysis info. 173void LPPassManager::getAnalysisUsage(AnalysisUsage &Info) const { 174 // LPPassManager needs LoopInfo. In the long term LoopInfo class will 175 // become part of LPPassManager. 176 Info.addRequired<LoopInfo>(); 177 Info.setPreservesAll(); 178} 179 180/// run - Execute all of the passes scheduled for execution. Keep track of 181/// whether any of the passes modifies the function, and if so, return true. 182bool LPPassManager::runOnFunction(Function &F) { 183 LI = &getAnalysis<LoopInfo>(); 184 bool Changed = false; 185 186 // Collect inherited analysis from Module level pass manager. 187 populateInheritedAnalysis(TPM->activeStack); 188 189 // Populate the loop queue in reverse program order. There is no clear need to 190 // process sibling loops in either forward or reverse order. There may be some 191 // advantage in deleting uses in a later loop before optimizing the 192 // definitions in an earlier loop. If we find a clear reason to process in 193 // forward order, then a forward variant of LoopPassManager should be created. 194 // 195 // Note that LoopInfo::iterator visits loops in reverse program 196 // order. Here, reverse_iterator gives us a forward order, and the LoopQueue 197 // reverses the order a third time by popping from the back. 198 for (LoopInfo::reverse_iterator I = LI->rbegin(), E = LI->rend(); I != E; ++I) 199 addLoopIntoQueue(*I, LQ); 200 201 if (LQ.empty()) // No loops, skip calling finalizers 202 return false; 203 204 // Initialization 205 for (std::deque<Loop *>::const_iterator I = LQ.begin(), E = LQ.end(); 206 I != E; ++I) { 207 Loop *L = *I; 208 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 209 LoopPass *P = getContainedPass(Index); 210 Changed |= P->doInitialization(L, *this); 211 } 212 } 213 214 // Walk Loops 215 while (!LQ.empty()) { 216 217 CurrentLoop = LQ.back(); 218 skipThisLoop = false; 219 redoThisLoop = false; 220 221 // Run all passes on the current Loop. 222 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 223 LoopPass *P = getContainedPass(Index); 224 225 dumpPassInfo(P, EXECUTION_MSG, ON_LOOP_MSG, 226 CurrentLoop->getHeader()->getName()); 227 dumpRequiredSet(P); 228 229 initializeAnalysisImpl(P); 230 231 { 232 PassManagerPrettyStackEntry X(P, *CurrentLoop->getHeader()); 233 TimeRegion PassTimer(getPassTimer(P)); 234 235 Changed |= P->runOnLoop(CurrentLoop, *this); 236 } 237 238 if (Changed) 239 dumpPassInfo(P, MODIFICATION_MSG, ON_LOOP_MSG, 240 skipThisLoop ? "<deleted>" : 241 CurrentLoop->getHeader()->getName()); 242 dumpPreservedSet(P); 243 244 if (!skipThisLoop) { 245 // Manually check that this loop is still healthy. This is done 246 // instead of relying on LoopInfo::verifyLoop since LoopInfo 247 // is a function pass and it's really expensive to verify every 248 // loop in the function every time. That level of checking can be 249 // enabled with the -verify-loop-info option. 250 { 251 TimeRegion PassTimer(getPassTimer(LI)); 252 CurrentLoop->verifyLoop(); 253 } 254 255 // Then call the regular verifyAnalysis functions. 256 verifyPreservedAnalysis(P); 257 258 F.getContext().yield(); 259 } 260 261 removeNotPreservedAnalysis(P); 262 recordAvailableAnalysis(P); 263 removeDeadPasses(P, 264 skipThisLoop ? "<deleted>" : 265 CurrentLoop->getHeader()->getName(), 266 ON_LOOP_MSG); 267 268 if (skipThisLoop) 269 // Do not run other passes on this loop. 270 break; 271 } 272 273 // If the loop was deleted, release all the loop passes. This frees up 274 // some memory, and avoids trouble with the pass manager trying to call 275 // verifyAnalysis on them. 276 if (skipThisLoop) 277 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 278 Pass *P = getContainedPass(Index); 279 freePass(P, "<deleted>", ON_LOOP_MSG); 280 } 281 282 // Pop the loop from queue after running all passes. 283 LQ.pop_back(); 284 285 if (redoThisLoop) 286 LQ.push_back(CurrentLoop); 287 } 288 289 // Finalization 290 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 291 LoopPass *P = getContainedPass(Index); 292 Changed |= P->doFinalization(); 293 } 294 295 return Changed; 296} 297 298/// Print passes managed by this manager 299void LPPassManager::dumpPassStructure(unsigned Offset) { 300 errs().indent(Offset*2) << "Loop Pass Manager\n"; 301 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 302 Pass *P = getContainedPass(Index); 303 P->dumpPassStructure(Offset + 1); 304 dumpLastUses(P, Offset+1); 305 } 306} 307 308 309//===----------------------------------------------------------------------===// 310// LoopPass 311 312Pass *LoopPass::createPrinterPass(raw_ostream &O, 313 const std::string &Banner) const { 314 return new PrintLoopPass(Banner, O); 315} 316 317// Check if this pass is suitable for the current LPPassManager, if 318// available. This pass P is not suitable for a LPPassManager if P 319// is not preserving higher level analysis info used by other 320// LPPassManager passes. In such case, pop LPPassManager from the 321// stack. This will force assignPassManager() to create new 322// LPPassManger as expected. 323void LoopPass::preparePassManager(PMStack &PMS) { 324 325 // Find LPPassManager 326 while (!PMS.empty() && 327 PMS.top()->getPassManagerType() > PMT_LoopPassManager) 328 PMS.pop(); 329 330 // If this pass is destroying high level information that is used 331 // by other passes that are managed by LPM then do not insert 332 // this pass in current LPM. Use new LPPassManager. 333 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager && 334 !PMS.top()->preserveHigherLevelAnalysis(this)) 335 PMS.pop(); 336} 337 338/// Assign pass manager to manage this pass. 339void LoopPass::assignPassManager(PMStack &PMS, 340 PassManagerType PreferredType) { 341 // Find LPPassManager 342 while (!PMS.empty() && 343 PMS.top()->getPassManagerType() > PMT_LoopPassManager) 344 PMS.pop(); 345 346 LPPassManager *LPPM; 347 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager) 348 LPPM = (LPPassManager*)PMS.top(); 349 else { 350 // Create new Loop Pass Manager if it does not exist. 351 assert (!PMS.empty() && "Unable to create Loop Pass Manager"); 352 PMDataManager *PMD = PMS.top(); 353 354 // [1] Create new Loop Pass Manager 355 LPPM = new LPPassManager(); 356 LPPM->populateInheritedAnalysis(PMS); 357 358 // [2] Set up new manager's top level manager 359 PMTopLevelManager *TPM = PMD->getTopLevelManager(); 360 TPM->addIndirectPassManager(LPPM); 361 362 // [3] Assign manager to manage this new manager. This may create 363 // and push new managers into PMS 364 Pass *P = LPPM->getAsPass(); 365 TPM->schedulePass(P); 366 367 // [4] Push new manager into PMS 368 PMS.push(LPPM); 369 } 370 371 LPPM->add(this); 372} 373 374// Containing function has Attribute::OptimizeNone and transformation 375// passes should skip it. 376bool LoopPass::skipOptnoneFunction(const Loop *L) const { 377 const Function *F = L->getHeader()->getParent(); 378 if (F && F->hasFnAttribute(Attribute::OptimizeNone)) { 379 // FIXME: Report this to dbgs() only once per function. 380 DEBUG(dbgs() << "Skipping pass '" << getPassName() 381 << "' in function " << F->getName() << "\n"); 382 // FIXME: Delete loop from pass manager's queue? 383 return true; 384 } 385 return false; 386} 387