LoopPass.cpp revision 794fd75c67a2cdc128d67342c6d88a504d186896
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 24const int 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/// run - Execute all of the passes scheduled for execution. Keep track of 161/// whether any of the passes modifies the function, and if so, return true. 162bool LPPassManager::runOnFunction(Function &F) { 163 LI = &getAnalysis<LoopInfo>(); 164 bool Changed = false; 165 166 // Populate Loop Queue 167 for (LoopInfo::iterator I = LI->begin(), E = LI->end(); I != E; ++I) 168 addLoopIntoQueue(*I, LQ); 169 170 // Initialization 171 for (std::deque<Loop *>::const_iterator I = LQ.begin(), E = LQ.end(); 172 I != E; ++I) { 173 Loop *L = *I; 174 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 175 Pass *P = getContainedPass(Index); 176 LoopPass *LP = dynamic_cast<LoopPass *>(P); 177 if (LP) 178 Changed |= LP->doInitialization(L, *this); 179 } 180 } 181 182 // Walk Loops 183 while (!LQ.empty()) { 184 185 CurrentLoop = LQ.back(); 186 skipThisLoop = false; 187 redoThisLoop = false; 188 189 // Run all passes on current SCC 190 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 191 192 Pass *P = getContainedPass(Index); 193 AnalysisUsage AnUsage; 194 P->getAnalysisUsage(AnUsage); 195 196 dumpPassInfo(P, EXECUTION_MSG, ON_LOOP_MSG, ""); 197 dumpAnalysisSetInfo("Required", P, AnUsage.getRequiredSet()); 198 199 initializeAnalysisImpl(P); 200 201 StartPassTimer(P); 202 LoopPass *LP = dynamic_cast<LoopPass *>(P); 203 assert (LP && "Invalid LPPassManager member"); 204 LP->runOnLoop(CurrentLoop, *this); 205 StopPassTimer(P); 206 207 if (Changed) 208 dumpPassInfo(P, MODIFICATION_MSG, ON_LOOP_MSG, ""); 209 dumpAnalysisSetInfo("Preserved", P, AnUsage.getPreservedSet()); 210 211 removeNotPreservedAnalysis(P); 212 recordAvailableAnalysis(P); 213 removeDeadPasses(P, "", ON_LOOP_MSG); 214 215 if (skipThisLoop) 216 // Do not run other passes on this loop. 217 break; 218 } 219 220 // Pop the loop from queue after running all passes. 221 LQ.pop_back(); 222 223 if (redoThisLoop) 224 LQ.push_back(CurrentLoop); 225 } 226 227 // Finalization 228 for (unsigned Index = 0; Index < getNumContainedPasses(); ++Index) { 229 Pass *P = getContainedPass(Index); 230 LoopPass *LP = dynamic_cast <LoopPass *>(P); 231 if (LP) 232 Changed |= LP->doFinalization(); 233 } 234 235 return Changed; 236} 237 238 239//===----------------------------------------------------------------------===// 240// LoopPass 241 242// Check if this pass is suitable for the current LPPassManager, if 243// available. This pass P is not suitable for a LPPassManager if P 244// is not preserving higher level analysis info used by other 245// LPPassManager passes. In such case, pop LPPassManager from the 246// stack. This will force assignPassManager() to create new 247// LPPassManger as expected. 248void LoopPass::preparePassManager(PMStack &PMS) { 249 250 // Find LPPassManager 251 while (!PMS.empty()) { 252 if (PMS.top()->getPassManagerType() > PMT_LoopPassManager) 253 PMS.pop(); 254 else; 255 break; 256 } 257 258 LPPassManager *LPPM = dynamic_cast<LPPassManager *>(PMS.top()); 259 260 // If this pass is destroying high level information that is used 261 // by other passes that are managed by LPM then do not insert 262 // this pass in current LPM. Use new LPPassManager. 263 if (LPPM && !LPPM->preserveHigherLevelAnalysis(this)) 264 PMS.pop(); 265} 266 267/// Assign pass manager to manage this pass. 268void LoopPass::assignPassManager(PMStack &PMS, 269 PassManagerType PreferredType) { 270 // Find LPPassManager 271 while (!PMS.empty()) { 272 if (PMS.top()->getPassManagerType() > PMT_LoopPassManager) 273 PMS.pop(); 274 else; 275 break; 276 } 277 278 LPPassManager *LPPM = dynamic_cast<LPPassManager *>(PMS.top()); 279 280 // Create new Loop Pass Manager if it does not exist. 281 if (!LPPM) { 282 283 assert (!PMS.empty() && "Unable to create Loop Pass Manager"); 284 PMDataManager *PMD = PMS.top(); 285 286 // [1] Create new Call Graph Pass Manager 287 LPPM = new LPPassManager(PMD->getDepth() + 1); 288 LPPM->populateInheritedAnalysis(PMS); 289 290 // [2] Set up new manager's top level manager 291 PMTopLevelManager *TPM = PMD->getTopLevelManager(); 292 TPM->addIndirectPassManager(LPPM); 293 294 // [3] Assign manager to manage this new manager. This may create 295 // and push new managers into PMS 296 Pass *P = dynamic_cast<Pass *>(LPPM); 297 TPM->schedulePass(P); 298 299 // [4] Push new manager into PMS 300 PMS.push(LPPM); 301 } 302 303 LPPM->add(this); 304} 305 306