1 //===- LoopExtractor.cpp - Extract each loop into a new function ----------===// 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 // A pass wrapper around the ExtractLoop() scalar transformation to extract each 11 // top-level loop into its own new function. If the loop is the ONLY loop in a 12 // given function, it is not touched. This is a pass most useful for debugging 13 // via bugpoint. 14 // 15 //===----------------------------------------------------------------------===// 16 17 #define DEBUG_TYPE "loop-extract" 18 #include "llvm/Transforms/IPO.h" 19 #include "llvm/Instructions.h" 20 #include "llvm/Module.h" 21 #include "llvm/Pass.h" 22 #include "llvm/Analysis/Dominators.h" 23 #include "llvm/Analysis/LoopPass.h" 24 #include "llvm/Support/CommandLine.h" 25 #include "llvm/Transforms/Scalar.h" 26 #include "llvm/Transforms/Utils/BasicBlockUtils.h" 27 #include "llvm/Transforms/Utils/FunctionUtils.h" 28 #include "llvm/ADT/Statistic.h" 29 #include <fstream> 30 #include <set> 31 using namespace llvm; 32 33 STATISTIC(NumExtracted, "Number of loops extracted"); 34 35 namespace { 36 struct LoopExtractor : public LoopPass { 37 static char ID; // Pass identification, replacement for typeid 38 unsigned NumLoops; 39 40 explicit LoopExtractor(unsigned numLoops = ~0) 41 : LoopPass(ID), NumLoops(numLoops) { 42 initializeLoopExtractorPass(*PassRegistry::getPassRegistry()); 43 } 44 45 virtual bool runOnLoop(Loop *L, LPPassManager &LPM); 46 47 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 48 AU.addRequiredID(BreakCriticalEdgesID); 49 AU.addRequiredID(LoopSimplifyID); 50 AU.addRequired<DominatorTree>(); 51 } 52 }; 53 } 54 55 char LoopExtractor::ID = 0; 56 INITIALIZE_PASS_BEGIN(LoopExtractor, "loop-extract", 57 "Extract loops into new functions", false, false) 58 INITIALIZE_PASS_DEPENDENCY(BreakCriticalEdges) 59 INITIALIZE_PASS_DEPENDENCY(LoopSimplify) 60 INITIALIZE_PASS_DEPENDENCY(DominatorTree) 61 INITIALIZE_PASS_END(LoopExtractor, "loop-extract", 62 "Extract loops into new functions", false, false) 63 64 namespace { 65 /// SingleLoopExtractor - For bugpoint. 66 struct SingleLoopExtractor : public LoopExtractor { 67 static char ID; // Pass identification, replacement for typeid 68 SingleLoopExtractor() : LoopExtractor(1) {} 69 }; 70 } // End anonymous namespace 71 72 char SingleLoopExtractor::ID = 0; 73 INITIALIZE_PASS(SingleLoopExtractor, "loop-extract-single", 74 "Extract at most one loop into a new function", false, false) 75 76 // createLoopExtractorPass - This pass extracts all natural loops from the 77 // program into a function if it can. 78 // 79 Pass *llvm::createLoopExtractorPass() { return new LoopExtractor(); } 80 81 bool LoopExtractor::runOnLoop(Loop *L, LPPassManager &LPM) { 82 // Only visit top-level loops. 83 if (L->getParentLoop()) 84 return false; 85 86 // If LoopSimplify form is not available, stay out of trouble. 87 if (!L->isLoopSimplifyForm()) 88 return false; 89 90 DominatorTree &DT = getAnalysis<DominatorTree>(); 91 bool Changed = false; 92 93 // If there is more than one top-level loop in this function, extract all of 94 // the loops. Otherwise there is exactly one top-level loop; in this case if 95 // this function is more than a minimal wrapper around the loop, extract 96 // the loop. 97 bool ShouldExtractLoop = false; 98 99 // Extract the loop if the entry block doesn't branch to the loop header. 100 TerminatorInst *EntryTI = 101 L->getHeader()->getParent()->getEntryBlock().getTerminator(); 102 if (!isa<BranchInst>(EntryTI) || 103 !cast<BranchInst>(EntryTI)->isUnconditional() || 104 EntryTI->getSuccessor(0) != L->getHeader()) { 105 ShouldExtractLoop = true; 106 } else { 107 // Check to see if any exits from the loop are more than just return 108 // blocks. 109 SmallVector<BasicBlock*, 8> ExitBlocks; 110 L->getExitBlocks(ExitBlocks); 111 for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) 112 if (!isa<ReturnInst>(ExitBlocks[i]->getTerminator())) { 113 ShouldExtractLoop = true; 114 break; 115 } 116 } 117 118 if (ShouldExtractLoop) { 119 // We must omit landing pads. Landing pads must accompany the invoke 120 // instruction. But this would result in a loop in the extracted 121 // function. An infinite cycle occurs when it tries to extract that loop as 122 // well. 123 SmallVector<BasicBlock*, 8> ExitBlocks; 124 L->getExitBlocks(ExitBlocks); 125 for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) 126 if (ExitBlocks[i]->isLandingPad()) { 127 ShouldExtractLoop = false; 128 break; 129 } 130 } 131 132 if (ShouldExtractLoop) { 133 if (NumLoops == 0) return Changed; 134 --NumLoops; 135 if (ExtractLoop(DT, L) != 0) { 136 Changed = true; 137 // After extraction, the loop is replaced by a function call, so 138 // we shouldn't try to run any more loop passes on it. 139 LPM.deleteLoopFromQueue(L); 140 } 141 ++NumExtracted; 142 } 143 144 return Changed; 145 } 146 147 // createSingleLoopExtractorPass - This pass extracts one natural loop from the 148 // program into a function if it can. This is used by bugpoint. 149 // 150 Pass *llvm::createSingleLoopExtractorPass() { 151 return new SingleLoopExtractor(); 152 } 153 154 155 // BlockFile - A file which contains a list of blocks that should not be 156 // extracted. 157 static cl::opt<std::string> 158 BlockFile("extract-blocks-file", cl::value_desc("filename"), 159 cl::desc("A file containing list of basic blocks to not extract"), 160 cl::Hidden); 161 162 namespace { 163 /// BlockExtractorPass - This pass is used by bugpoint to extract all blocks 164 /// from the module into their own functions except for those specified by the 165 /// BlocksToNotExtract list. 166 class BlockExtractorPass : public ModulePass { 167 void LoadFile(const char *Filename); 168 void SplitLandingPadPreds(Function *F); 169 170 std::vector<BasicBlock*> BlocksToNotExtract; 171 std::vector<std::pair<std::string, std::string> > BlocksToNotExtractByName; 172 public: 173 static char ID; // Pass identification, replacement for typeid 174 BlockExtractorPass() : ModulePass(ID) { 175 if (!BlockFile.empty()) 176 LoadFile(BlockFile.c_str()); 177 } 178 179 bool runOnModule(Module &M); 180 }; 181 } 182 183 char BlockExtractorPass::ID = 0; 184 INITIALIZE_PASS(BlockExtractorPass, "extract-blocks", 185 "Extract Basic Blocks From Module (for bugpoint use)", 186 false, false) 187 188 // createBlockExtractorPass - This pass extracts all blocks (except those 189 // specified in the argument list) from the functions in the module. 190 // 191 ModulePass *llvm::createBlockExtractorPass() { 192 return new BlockExtractorPass(); 193 } 194 195 void BlockExtractorPass::LoadFile(const char *Filename) { 196 // Load the BlockFile... 197 std::ifstream In(Filename); 198 if (!In.good()) { 199 errs() << "WARNING: BlockExtractor couldn't load file '" << Filename 200 << "'!\n"; 201 return; 202 } 203 while (In) { 204 std::string FunctionName, BlockName; 205 In >> FunctionName; 206 In >> BlockName; 207 if (!BlockName.empty()) 208 BlocksToNotExtractByName.push_back( 209 std::make_pair(FunctionName, BlockName)); 210 } 211 } 212 213 /// SplitLandingPadPreds - The landing pad needs to be extracted with the invoke 214 /// instruction. The critical edge breaker will refuse to break critical edges 215 /// to a landing pad. So do them here. After this method runs, all landing pads 216 /// should have only one predecessor. 217 void BlockExtractorPass::SplitLandingPadPreds(Function *F) { 218 for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) { 219 InvokeInst *II = dyn_cast<InvokeInst>(I); 220 if (!II) continue; 221 BasicBlock *Parent = II->getParent(); 222 BasicBlock *LPad = II->getUnwindDest(); 223 224 // Look through the landing pad's predecessors. If one of them ends in an 225 // 'invoke', then we want to split the landing pad. 226 bool Split = false; 227 for (pred_iterator 228 PI = pred_begin(LPad), PE = pred_end(LPad); PI != PE; ++PI) { 229 BasicBlock *BB = *PI; 230 if (BB->isLandingPad() && BB != Parent && 231 isa<InvokeInst>(Parent->getTerminator())) { 232 Split = true; 233 break; 234 } 235 } 236 237 if (!Split) continue; 238 239 SmallVector<BasicBlock*, 2> NewBBs; 240 SplitLandingPadPredecessors(LPad, Parent, ".1", ".2", 0, NewBBs); 241 } 242 } 243 244 bool BlockExtractorPass::runOnModule(Module &M) { 245 std::set<BasicBlock*> TranslatedBlocksToNotExtract; 246 for (unsigned i = 0, e = BlocksToNotExtract.size(); i != e; ++i) { 247 BasicBlock *BB = BlocksToNotExtract[i]; 248 Function *F = BB->getParent(); 249 250 // Map the corresponding function in this module. 251 Function *MF = M.getFunction(F->getName()); 252 assert(MF->getFunctionType() == F->getFunctionType() && "Wrong function?"); 253 254 // Figure out which index the basic block is in its function. 255 Function::iterator BBI = MF->begin(); 256 std::advance(BBI, std::distance(F->begin(), Function::iterator(BB))); 257 TranslatedBlocksToNotExtract.insert(BBI); 258 } 259 260 while (!BlocksToNotExtractByName.empty()) { 261 // There's no way to find BBs by name without looking at every BB inside 262 // every Function. Fortunately, this is always empty except when used by 263 // bugpoint in which case correctness is more important than performance. 264 265 std::string &FuncName = BlocksToNotExtractByName.back().first; 266 std::string &BlockName = BlocksToNotExtractByName.back().second; 267 268 for (Module::iterator FI = M.begin(), FE = M.end(); FI != FE; ++FI) { 269 Function &F = *FI; 270 if (F.getName() != FuncName) continue; 271 272 for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE; ++BI) { 273 BasicBlock &BB = *BI; 274 if (BB.getName() != BlockName) continue; 275 276 TranslatedBlocksToNotExtract.insert(BI); 277 } 278 } 279 280 BlocksToNotExtractByName.pop_back(); 281 } 282 283 // Now that we know which blocks to not extract, figure out which ones we WANT 284 // to extract. 285 std::vector<BasicBlock*> BlocksToExtract; 286 for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) { 287 SplitLandingPadPreds(&*F); 288 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) 289 if (!TranslatedBlocksToNotExtract.count(BB)) 290 BlocksToExtract.push_back(BB); 291 } 292 293 for (unsigned i = 0, e = BlocksToExtract.size(); i != e; ++i) { 294 SmallVector<BasicBlock*, 2> BlocksToExtractVec; 295 BlocksToExtractVec.push_back(BlocksToExtract[i]); 296 if (const InvokeInst *II = 297 dyn_cast<InvokeInst>(BlocksToExtract[i]->getTerminator())) 298 BlocksToExtractVec.push_back(II->getUnwindDest()); 299 ExtractBasicBlock(BlocksToExtractVec); 300 } 301 302 return !BlocksToExtract.empty(); 303 } 304