LoopPass.cpp revision 4c5e43da7792f75567b693105cc53e3f1992ad98
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#include "llvm/Support/raw_ostream.h" 22using namespace llvm; 23 24#define DEBUG_TYPE "loop-pass-manager" 25 26namespace { 27 28/// PrintLoopPass - Print a Function corresponding to a Loop. 29/// 30class PrintLoopPass : public LoopPass { 31private: 32 std::string Banner; 33 raw_ostream &Out; // raw_ostream to print on. 34 35public: 36 static char ID; 37 PrintLoopPass(const std::string &B, raw_ostream &o) 38 : LoopPass(ID), Banner(B), Out(o) {} 39 40 void getAnalysisUsage(AnalysisUsage &AU) const override { 41 AU.setPreservesAll(); 42 } 43 44 bool runOnLoop(Loop *L, LPPassManager &) override { 45 Out << Banner; 46 for (Loop::block_iterator b = L->block_begin(), be = L->block_end(); 47 b != be; 48 ++b) { 49 if (*b) 50 (*b)->print(Out); 51 else 52 Out << "Printing <null> block"; 53 } 54 return false; 55 } 56}; 57 58char PrintLoopPass::ID = 0; 59} 60 61//===----------------------------------------------------------------------===// 62// LPPassManager 63// 64 65char LPPassManager::ID = 0; 66 67LPPassManager::LPPassManager() 68 : FunctionPass(ID), PMDataManager() { 69 skipThisLoop = false; 70 redoThisLoop = false; 71 LI = nullptr; 72 CurrentLoop = nullptr; 73} 74 75/// Delete loop from the loop queue and loop hierarchy (LoopInfo). 76void LPPassManager::deleteLoopFromQueue(Loop *L) { 77 78 LI->updateUnloop(L); 79 80 // Notify passes that the loop is being deleted. 81 deleteSimpleAnalysisLoop(L); 82 83 // If L is current loop then skip rest of the passes and let 84 // runOnFunction remove L from LQ. Otherwise, remove L from LQ now 85 // and continue applying other passes on CurrentLoop. 86 if (CurrentLoop == L) 87 skipThisLoop = true; 88 89 delete L; 90 91 if (skipThisLoop) 92 return; 93 94 for (std::deque<Loop *>::iterator I = LQ.begin(), 95 E = LQ.end(); I != E; ++I) { 96 if (*I == L) { 97 LQ.erase(I); 98 break; 99 } 100 } 101} 102 103// Inset loop into loop nest (LoopInfo) and loop queue (LQ). 104void LPPassManager::insertLoop(Loop *L, Loop *ParentLoop) { 105 106 assert (CurrentLoop != L && "Cannot insert CurrentLoop"); 107 108 // Insert into loop nest 109 if (ParentLoop) 110 ParentLoop->addChildLoop(L); 111 else 112 LI->addTopLevelLoop(L); 113 114 insertLoopIntoQueue(L); 115} 116 117void LPPassManager::insertLoopIntoQueue(Loop *L) { 118 // Insert L into loop queue 119 if (L == CurrentLoop) 120 redoLoop(L); 121 else if (!L->getParentLoop()) 122 // This is top level loop. 123 LQ.push_front(L); 124 else { 125 // Insert L after the parent loop. 126 for (std::deque<Loop *>::iterator I = LQ.begin(), 127 E = LQ.end(); I != E; ++I) { 128 if (*I == L->getParentLoop()) { 129 // deque does not support insert after. 130 ++I; 131 LQ.insert(I, 1, L); 132 break; 133 } 134 } 135 } 136} 137 138// Reoptimize this loop. LPPassManager will re-insert this loop into the 139// queue. This allows LoopPass to change loop nest for the loop. This 140// utility may send LPPassManager into infinite loops so use caution. 141void LPPassManager::redoLoop(Loop *L) { 142 assert (CurrentLoop == L && "Can redo only CurrentLoop"); 143 redoThisLoop = true; 144} 145 146/// cloneBasicBlockSimpleAnalysis - Invoke cloneBasicBlockAnalysis hook for 147/// all loop passes. 148void LPPassManager::cloneBasicBlockSimpleAnalysis(BasicBlock *From, 149 BasicBlock *To, Loop *L) { 150 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 151 LoopPass *LP = getContainedPass(Index); 152 LP->cloneBasicBlockAnalysis(From, To, L); 153 } 154} 155 156/// deleteSimpleAnalysisValue - Invoke deleteAnalysisValue hook for all passes. 157void LPPassManager::deleteSimpleAnalysisValue(Value *V, Loop *L) { 158 if (BasicBlock *BB = dyn_cast<BasicBlock>(V)) { 159 for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE; 160 ++BI) { 161 Instruction &I = *BI; 162 deleteSimpleAnalysisValue(&I, L); 163 } 164 } 165 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 166 LoopPass *LP = getContainedPass(Index); 167 LP->deleteAnalysisValue(V, L); 168 } 169} 170 171/// Invoke deleteAnalysisLoop hook for all passes. 172void LPPassManager::deleteSimpleAnalysisLoop(Loop *L) { 173 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 174 LoopPass *LP = getContainedPass(Index); 175 LP->deleteAnalysisLoop(L); 176 } 177} 178 179 180// Recurse through all subloops and all loops into LQ. 181static void addLoopIntoQueue(Loop *L, std::deque<Loop *> &LQ) { 182 LQ.push_back(L); 183 for (Loop::reverse_iterator I = L->rbegin(), E = L->rend(); I != E; ++I) 184 addLoopIntoQueue(*I, LQ); 185} 186 187/// Pass Manager itself does not invalidate any analysis info. 188void LPPassManager::getAnalysisUsage(AnalysisUsage &Info) const { 189 // LPPassManager needs LoopInfo. In the long term LoopInfo class will 190 // become part of LPPassManager. 191 Info.addRequired<LoopInfoWrapperPass>(); 192 Info.setPreservesAll(); 193} 194 195/// run - Execute all of the passes scheduled for execution. Keep track of 196/// whether any of the passes modifies the function, and if so, return true. 197bool LPPassManager::runOnFunction(Function &F) { 198 auto &LIWP = getAnalysis<LoopInfoWrapperPass>(); 199 LI = &LIWP.getLoopInfo(); 200 bool Changed = false; 201 202 // Collect inherited analysis from Module level pass manager. 203 populateInheritedAnalysis(TPM->activeStack); 204 205 // Populate the loop queue in reverse program order. There is no clear need to 206 // process sibling loops in either forward or reverse order. There may be some 207 // advantage in deleting uses in a later loop before optimizing the 208 // definitions in an earlier loop. If we find a clear reason to process in 209 // forward order, then a forward variant of LoopPassManager should be created. 210 // 211 // Note that LoopInfo::iterator visits loops in reverse program 212 // order. Here, reverse_iterator gives us a forward order, and the LoopQueue 213 // reverses the order a third time by popping from the back. 214 for (LoopInfo::reverse_iterator I = LI->rbegin(), E = LI->rend(); I != E; ++I) 215 addLoopIntoQueue(*I, LQ); 216 217 if (LQ.empty()) // No loops, skip calling finalizers 218 return false; 219 220 // Initialization 221 for (std::deque<Loop *>::const_iterator I = LQ.begin(), E = LQ.end(); 222 I != E; ++I) { 223 Loop *L = *I; 224 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 225 LoopPass *P = getContainedPass(Index); 226 Changed |= P->doInitialization(L, *this); 227 } 228 } 229 230 // Walk Loops 231 while (!LQ.empty()) { 232 233 CurrentLoop = LQ.back(); 234 skipThisLoop = false; 235 redoThisLoop = false; 236 237 // Run all passes on the current Loop. 238 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 239 LoopPass *P = getContainedPass(Index); 240 241 dumpPassInfo(P, EXECUTION_MSG, ON_LOOP_MSG, 242 CurrentLoop->getHeader()->getName()); 243 dumpRequiredSet(P); 244 245 initializeAnalysisImpl(P); 246 247 { 248 PassManagerPrettyStackEntry X(P, *CurrentLoop->getHeader()); 249 TimeRegion PassTimer(getPassTimer(P)); 250 251 Changed |= P->runOnLoop(CurrentLoop, *this); 252 } 253 254 if (Changed) 255 dumpPassInfo(P, MODIFICATION_MSG, ON_LOOP_MSG, 256 skipThisLoop ? "<deleted>" : 257 CurrentLoop->getHeader()->getName()); 258 dumpPreservedSet(P); 259 260 if (!skipThisLoop) { 261 // Manually check that this loop is still healthy. This is done 262 // instead of relying on LoopInfo::verifyLoop since LoopInfo 263 // is a function pass and it's really expensive to verify every 264 // loop in the function every time. That level of checking can be 265 // enabled with the -verify-loop-info option. 266 { 267 TimeRegion PassTimer(getPassTimer(&LIWP)); 268 CurrentLoop->verifyLoop(); 269 } 270 271 // Then call the regular verifyAnalysis functions. 272 verifyPreservedAnalysis(P); 273 274 F.getContext().yield(); 275 } 276 277 removeNotPreservedAnalysis(P); 278 recordAvailableAnalysis(P); 279 removeDeadPasses(P, 280 skipThisLoop ? "<deleted>" : 281 CurrentLoop->getHeader()->getName(), 282 ON_LOOP_MSG); 283 284 if (skipThisLoop) 285 // Do not run other passes on this loop. 286 break; 287 } 288 289 // If the loop was deleted, release all the loop passes. This frees up 290 // some memory, and avoids trouble with the pass manager trying to call 291 // verifyAnalysis on them. 292 if (skipThisLoop) 293 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 294 Pass *P = getContainedPass(Index); 295 freePass(P, "<deleted>", ON_LOOP_MSG); 296 } 297 298 // Pop the loop from queue after running all passes. 299 LQ.pop_back(); 300 301 if (redoThisLoop) 302 LQ.push_back(CurrentLoop); 303 } 304 305 // Finalization 306 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 307 LoopPass *P = getContainedPass(Index); 308 Changed |= P->doFinalization(); 309 } 310 311 return Changed; 312} 313 314/// Print passes managed by this manager 315void LPPassManager::dumpPassStructure(unsigned Offset) { 316 errs().indent(Offset*2) << "Loop Pass Manager\n"; 317 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 318 Pass *P = getContainedPass(Index); 319 P->dumpPassStructure(Offset + 1); 320 dumpLastUses(P, Offset+1); 321 } 322} 323 324 325//===----------------------------------------------------------------------===// 326// LoopPass 327 328Pass *LoopPass::createPrinterPass(raw_ostream &O, 329 const std::string &Banner) const { 330 return new PrintLoopPass(Banner, O); 331} 332 333// Check if this pass is suitable for the current LPPassManager, if 334// available. This pass P is not suitable for a LPPassManager if P 335// is not preserving higher level analysis info used by other 336// LPPassManager passes. In such case, pop LPPassManager from the 337// stack. This will force assignPassManager() to create new 338// LPPassManger as expected. 339void LoopPass::preparePassManager(PMStack &PMS) { 340 341 // Find LPPassManager 342 while (!PMS.empty() && 343 PMS.top()->getPassManagerType() > PMT_LoopPassManager) 344 PMS.pop(); 345 346 // If this pass is destroying high level information that is used 347 // by other passes that are managed by LPM then do not insert 348 // this pass in current LPM. Use new LPPassManager. 349 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager && 350 !PMS.top()->preserveHigherLevelAnalysis(this)) 351 PMS.pop(); 352} 353 354/// Assign pass manager to manage this pass. 355void LoopPass::assignPassManager(PMStack &PMS, 356 PassManagerType PreferredType) { 357 // Find LPPassManager 358 while (!PMS.empty() && 359 PMS.top()->getPassManagerType() > PMT_LoopPassManager) 360 PMS.pop(); 361 362 LPPassManager *LPPM; 363 if (PMS.top()->getPassManagerType() == PMT_LoopPassManager) 364 LPPM = (LPPassManager*)PMS.top(); 365 else { 366 // Create new Loop Pass Manager if it does not exist. 367 assert (!PMS.empty() && "Unable to create Loop Pass Manager"); 368 PMDataManager *PMD = PMS.top(); 369 370 // [1] Create new Loop Pass Manager 371 LPPM = new LPPassManager(); 372 LPPM->populateInheritedAnalysis(PMS); 373 374 // [2] Set up new manager's top level manager 375 PMTopLevelManager *TPM = PMD->getTopLevelManager(); 376 TPM->addIndirectPassManager(LPPM); 377 378 // [3] Assign manager to manage this new manager. This may create 379 // and push new managers into PMS 380 Pass *P = LPPM->getAsPass(); 381 TPM->schedulePass(P); 382 383 // [4] Push new manager into PMS 384 PMS.push(LPPM); 385 } 386 387 LPPM->add(this); 388} 389 390// Containing function has Attribute::OptimizeNone and transformation 391// passes should skip it. 392bool LoopPass::skipOptnoneFunction(const Loop *L) const { 393 const Function *F = L->getHeader()->getParent(); 394 if (F && F->hasFnAttribute(Attribute::OptimizeNone)) { 395 // FIXME: Report this to dbgs() only once per function. 396 DEBUG(dbgs() << "Skipping pass '" << getPassName() 397 << "' in function " << F->getName() << "\n"); 398 // FIXME: Delete loop from pass manager's queue? 399 return true; 400 } 401 return false; 402} 403