LoopPass.cpp revision 1a957d563fe894c797e0eba00bf069fbe7ecba77
1//===- LoopPass.cpp - Loop Pass and Loop Pass Manager ---------------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file was developed by Devang Patel and is distributed under 6// the University of Illinois Open Source 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/ScalarEvolutionExpander.h" 18using namespace llvm; 19 20//===----------------------------------------------------------------------===// 21// LPPassManager 22// 23 24char LPPassManager::ID = 0; 25/// LPPassManager manages FPPassManagers and CalLGraphSCCPasses. 26 27LPPassManager::LPPassManager(int Depth) 28 : FunctionPass((intptr_t)&ID), PMDataManager(Depth) { 29 skipThisLoop = false; 30 redoThisLoop = false; 31 LI = NULL; 32 CurrentLoop = NULL; 33} 34 35/// Delete loop from the loop queue and loop hierarcy (LoopInfo). 36void LPPassManager::deleteLoopFromQueue(Loop *L) { 37 38 if (Loop *ParentLoop = L->getParentLoop()) { // Not a top-level loop. 39 // Reparent all of the blocks in this loop. Since BBLoop had a parent, 40 // they are now all in it. 41 for (Loop::block_iterator I = L->block_begin(), E = L->block_end(); 42 I != E; ++I) 43 if (LI->getLoopFor(*I) == L) // Don't change blocks in subloops. 44 LI->changeLoopFor(*I, ParentLoop); 45 46 // Remove the loop from its parent loop. 47 for (Loop::iterator I = ParentLoop->begin(), E = ParentLoop->end();; 48 ++I) { 49 assert(I != E && "Couldn't find loop"); 50 if (*I == L) { 51 ParentLoop->removeChildLoop(I); 52 break; 53 } 54 } 55 56 // Move all subloops into the parent loop. 57 while (L->begin() != L->end()) 58 ParentLoop->addChildLoop(L->removeChildLoop(L->end()-1)); 59 } else { 60 // Reparent all of the blocks in this loop. Since BBLoop had no parent, 61 // they no longer in a loop at all. 62 63 for (unsigned i = 0; i != L->getBlocks().size(); ++i) { 64 // Don't change blocks in subloops. 65 if (LI->getLoopFor(L->getBlocks()[i]) == L) { 66 LI->removeBlock(L->getBlocks()[i]); 67 --i; 68 } 69 } 70 71 // Remove the loop from the top-level LoopInfo object. 72 for (LoopInfo::iterator I = LI->begin(), E = LI->end();; ++I) { 73 assert(I != E && "Couldn't find loop"); 74 if (*I == L) { 75 LI->removeLoop(I); 76 break; 77 } 78 } 79 80 // Move all of the subloops to the top-level. 81 while (L->begin() != L->end()) 82 LI->addTopLevelLoop(L->removeChildLoop(L->end()-1)); 83 } 84 85 delete L; 86 87 // If L is current loop then skip rest of the passes and let 88 // runOnFunction remove L from LQ. Otherwise, remove L from LQ now 89 // and continue applying other passes on CurrentLoop. 90 if (CurrentLoop == L) { 91 skipThisLoop = true; 92 return; 93 } 94 95 for (std::deque<Loop *>::iterator I = LQ.begin(), 96 E = LQ.end(); I != E; ++I) { 97 if (*I == L) { 98 LQ.erase(I); 99 break; 100 } 101 } 102} 103 104// Inset loop into loop nest (LoopInfo) and loop queue (LQ). 105void LPPassManager::insertLoop(Loop *L, Loop *ParentLoop) { 106 107 assert (CurrentLoop != L && "Cannot insert CurrentLoop"); 108 109 // Insert into loop nest 110 if (ParentLoop) 111 ParentLoop->addChildLoop(L); 112 else 113 LI->addTopLevelLoop(L); 114 115 // Insert L into loop queue 116 if (L == CurrentLoop) 117 redoLoop(L); 118 else if (!ParentLoop) 119 // This is top level loop. 120 LQ.push_front(L); 121 else { 122 // Insert L after ParentLoop 123 for (std::deque<Loop *>::iterator I = LQ.begin(), 124 E = LQ.end(); I != E; ++I) { 125 if (*I == ParentLoop) { 126 // deque does not support insert after. 127 ++I; 128 LQ.insert(I, 1, L); 129 break; 130 } 131 } 132 } 133} 134 135// Reoptimize this loop. LPPassManager will re-insert this loop into the 136// queue. This allows LoopPass to change loop nest for the loop. This 137// utility may send LPPassManager into infinite loops so use caution. 138void LPPassManager::redoLoop(Loop *L) { 139 assert (CurrentLoop == L && "Can redo only CurrentLoop"); 140 redoThisLoop = true; 141} 142 143// Recurse through all subloops and all loops into LQ. 144static void addLoopIntoQueue(Loop *L, std::deque<Loop *> &LQ) { 145 LQ.push_back(L); 146 for (Loop::iterator I = L->begin(), E = L->end(); I != E; ++I) 147 addLoopIntoQueue(*I, LQ); 148} 149 150/// Pass Manager itself does not invalidate any analysis info. 151void LPPassManager::getAnalysisUsage(AnalysisUsage &Info) const { 152 // LPPassManager needs LoopInfo. In the long term LoopInfo class will 153 // become part of LPPassManager. 154 Info.addRequired<LoopInfo>(); 155 // Used by IndVar doInitialization. 156 Info.addRequired<ScalarEvolution>(); 157 Info.setPreservesAll(); 158} 159 160/// verifyLoopInfo - Verify loop nest. 161void LPPassManager::verifyLoopInfo() { 162 assert (LI && "Loop Info is missing"); 163 164 for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I) { 165 Loop *L = *I; 166 assert (L->getHeader() && "Loop header is missing"); 167 assert (L->getLoopPreheader() && "Loop preheader is missing"); 168 assert (L->getLoopLatch() && "Loop latch is missing"); 169 } 170} 171 172/// run - Execute all of the passes scheduled for execution. Keep track of 173/// whether any of the passes modifies the function, and if so, return true. 174bool LPPassManager::runOnFunction(Function &F) { 175 LI = &getAnalysis<LoopInfo>(); 176 bool Changed = false; 177 178 // Populate Loop Queue 179 for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I) 180 addLoopIntoQueue(*I, LQ); 181 182 // Initialization 183 for (std::deque<Loop *>::const_iterator I = LQ.begin(), E = LQ.end(); 184 I != E; ++I) { 185 Loop *L = *I; 186 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 187 Pass *P = getContainedPass(Index); 188 LoopPass *LP = dynamic_cast<LoopPass *>(P); 189 if (LP) 190 Changed |= LP->doInitialization(L, *this); 191 } 192 } 193 194 // Walk Loops 195 while (!LQ.empty()) { 196 197 CurrentLoop = LQ.back(); 198 skipThisLoop = false; 199 redoThisLoop = false; 200 201 // Run all passes on current SCC 202 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 203 204 Pass *P = getContainedPass(Index); 205 AnalysisUsage AnUsage; 206 P->getAnalysisUsage(AnUsage); 207 208 dumpPassInfo(P, EXECUTION_MSG, ON_LOOP_MSG, ""); 209 dumpAnalysisSetInfo("Required", P, AnUsage.getRequiredSet()); 210 211 initializeAnalysisImpl(P); 212 213 StartPassTimer(P); 214 LoopPass *LP = dynamic_cast<LoopPass *>(P); 215 assert (LP && "Invalid LPPassManager member"); 216 LP->runOnLoop(CurrentLoop, *this); 217 verifyLoopInfo(); 218 StopPassTimer(P); 219 220 if (Changed) 221 dumpPassInfo(P, MODIFICATION_MSG, ON_LOOP_MSG, ""); 222 dumpAnalysisSetInfo("Preserved", P, AnUsage.getPreservedSet()); 223 224 removeNotPreservedAnalysis(P); 225 recordAvailableAnalysis(P); 226 removeDeadPasses(P, "", ON_LOOP_MSG); 227 228 if (skipThisLoop) 229 // Do not run other passes on this loop. 230 break; 231 } 232 233 // Pop the loop from queue after running all passes. 234 LQ.pop_back(); 235 236 if (redoThisLoop) 237 LQ.push_back(CurrentLoop); 238 } 239 240 // Finalization 241 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 242 Pass *P = getContainedPass(Index); 243 LoopPass *LP = dynamic_cast <LoopPass *>(P); 244 if (LP) 245 Changed |= LP->doFinalization(); 246 } 247 248 return Changed; 249} 250 251 252//===----------------------------------------------------------------------===// 253// LoopPass 254 255// Check if this pass is suitable for the current LPPassManager, if 256// available. This pass P is not suitable for a LPPassManager if P 257// is not preserving higher level analysis info used by other 258// LPPassManager passes. In such case, pop LPPassManager from the 259// stack. This will force assignPassManager() to create new 260// LPPassManger as expected. 261void LoopPass::preparePassManager(PMStack &PMS) { 262 263 // Find LPPassManager 264 while (!PMS.empty()) { 265 if (PMS.top()->getPassManagerType() > PMT_LoopPassManager) 266 PMS.pop(); 267 else; 268 break; 269 } 270 271 LPPassManager *LPPM = dynamic_cast<LPPassManager *>(PMS.top()); 272 273 // If this pass is destroying high level information that is used 274 // by other passes that are managed by LPM then do not insert 275 // this pass in current LPM. Use new LPPassManager. 276 if (LPPM && !LPPM->preserveHigherLevelAnalysis(this)) 277 PMS.pop(); 278} 279 280/// Assign pass manager to manage this pass. 281void LoopPass::assignPassManager(PMStack &PMS, 282 PassManagerType PreferredType) { 283 // Find LPPassManager 284 while (!PMS.empty()) { 285 if (PMS.top()->getPassManagerType() > PMT_LoopPassManager) 286 PMS.pop(); 287 else; 288 break; 289 } 290 291 LPPassManager *LPPM = dynamic_cast<LPPassManager *>(PMS.top()); 292 293 // Create new Loop Pass Manager if it does not exist. 294 if (!LPPM) { 295 296 assert (!PMS.empty() && "Unable to create Loop Pass Manager"); 297 PMDataManager *PMD = PMS.top(); 298 299 // [1] Create new Call Graph Pass Manager 300 LPPM = new LPPassManager(PMD->getDepth() + 1); 301 LPPM->populateInheritedAnalysis(PMS); 302 303 // [2] Set up new manager's top level manager 304 PMTopLevelManager *TPM = PMD->getTopLevelManager(); 305 TPM->addIndirectPassManager(LPPM); 306 307 // [3] Assign manager to manage this new manager. This may create 308 // and push new managers into PMS 309 Pass *P = dynamic_cast<Pass *>(LPPM); 310 TPM->schedulePass(P); 311 312 // [4] Push new manager into PMS 313 PMS.push(LPPM); 314 } 315 316 LPPM->add(this); 317} 318