LoopExtractor.cpp revision 36b56886974eae4f9c5ebc96befd3e7bfe5de338
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/ADT/Statistic.h" 20#include "llvm/Analysis/LoopPass.h" 21#include "llvm/IR/Dominators.h" 22#include "llvm/IR/Instructions.h" 23#include "llvm/IR/Module.h" 24#include "llvm/Pass.h" 25#include "llvm/Support/CommandLine.h" 26#include "llvm/Transforms/Scalar.h" 27#include "llvm/Transforms/Utils/BasicBlockUtils.h" 28#include "llvm/Transforms/Utils/CodeExtractor.h" 29#include <fstream> 30#include <set> 31using namespace llvm; 32 33STATISTIC(NumExtracted, "Number of loops extracted"); 34 35namespace { 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 bool runOnLoop(Loop *L, LPPassManager &LPM) override; 46 47 void getAnalysisUsage(AnalysisUsage &AU) const override { 48 AU.addRequiredID(BreakCriticalEdgesID); 49 AU.addRequiredID(LoopSimplifyID); 50 AU.addRequired<DominatorTreeWrapperPass>(); 51 } 52 }; 53} 54 55char LoopExtractor::ID = 0; 56INITIALIZE_PASS_BEGIN(LoopExtractor, "loop-extract", 57 "Extract loops into new functions", false, false) 58INITIALIZE_PASS_DEPENDENCY(BreakCriticalEdges) 59INITIALIZE_PASS_DEPENDENCY(LoopSimplify) 60INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass) 61INITIALIZE_PASS_END(LoopExtractor, "loop-extract", 62 "Extract loops into new functions", false, false) 63 64namespace { 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 72char SingleLoopExtractor::ID = 0; 73INITIALIZE_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// 79Pass *llvm::createLoopExtractorPass() { return new LoopExtractor(); } 80 81bool LoopExtractor::runOnLoop(Loop *L, LPPassManager &LPM) { 82 if (skipOptnoneFunction(L)) 83 return false; 84 85 // Only visit top-level loops. 86 if (L->getParentLoop()) 87 return false; 88 89 // If LoopSimplify form is not available, stay out of trouble. 90 if (!L->isLoopSimplifyForm()) 91 return false; 92 93 DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree(); 94 bool Changed = false; 95 96 // If there is more than one top-level loop in this function, extract all of 97 // the loops. Otherwise there is exactly one top-level loop; in this case if 98 // this function is more than a minimal wrapper around the loop, extract 99 // the loop. 100 bool ShouldExtractLoop = false; 101 102 // Extract the loop if the entry block doesn't branch to the loop header. 103 TerminatorInst *EntryTI = 104 L->getHeader()->getParent()->getEntryBlock().getTerminator(); 105 if (!isa<BranchInst>(EntryTI) || 106 !cast<BranchInst>(EntryTI)->isUnconditional() || 107 EntryTI->getSuccessor(0) != L->getHeader()) { 108 ShouldExtractLoop = true; 109 } else { 110 // Check to see if any exits from the loop are more than just return 111 // blocks. 112 SmallVector<BasicBlock*, 8> ExitBlocks; 113 L->getExitBlocks(ExitBlocks); 114 for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) 115 if (!isa<ReturnInst>(ExitBlocks[i]->getTerminator())) { 116 ShouldExtractLoop = true; 117 break; 118 } 119 } 120 121 if (ShouldExtractLoop) { 122 // We must omit landing pads. Landing pads must accompany the invoke 123 // instruction. But this would result in a loop in the extracted 124 // function. An infinite cycle occurs when it tries to extract that loop as 125 // well. 126 SmallVector<BasicBlock*, 8> ExitBlocks; 127 L->getExitBlocks(ExitBlocks); 128 for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) 129 if (ExitBlocks[i]->isLandingPad()) { 130 ShouldExtractLoop = false; 131 break; 132 } 133 } 134 135 if (ShouldExtractLoop) { 136 if (NumLoops == 0) return Changed; 137 --NumLoops; 138 CodeExtractor Extractor(DT, *L); 139 if (Extractor.extractCodeRegion() != 0) { 140 Changed = true; 141 // After extraction, the loop is replaced by a function call, so 142 // we shouldn't try to run any more loop passes on it. 143 LPM.deleteLoopFromQueue(L); 144 } 145 ++NumExtracted; 146 } 147 148 return Changed; 149} 150 151// createSingleLoopExtractorPass - This pass extracts one natural loop from the 152// program into a function if it can. This is used by bugpoint. 153// 154Pass *llvm::createSingleLoopExtractorPass() { 155 return new SingleLoopExtractor(); 156} 157 158 159// BlockFile - A file which contains a list of blocks that should not be 160// extracted. 161static cl::opt<std::string> 162BlockFile("extract-blocks-file", cl::value_desc("filename"), 163 cl::desc("A file containing list of basic blocks to not extract"), 164 cl::Hidden); 165 166namespace { 167 /// BlockExtractorPass - This pass is used by bugpoint to extract all blocks 168 /// from the module into their own functions except for those specified by the 169 /// BlocksToNotExtract list. 170 class BlockExtractorPass : public ModulePass { 171 void LoadFile(const char *Filename); 172 void SplitLandingPadPreds(Function *F); 173 174 std::vector<BasicBlock*> BlocksToNotExtract; 175 std::vector<std::pair<std::string, std::string> > BlocksToNotExtractByName; 176 public: 177 static char ID; // Pass identification, replacement for typeid 178 BlockExtractorPass() : ModulePass(ID) { 179 if (!BlockFile.empty()) 180 LoadFile(BlockFile.c_str()); 181 } 182 183 bool runOnModule(Module &M) override; 184 }; 185} 186 187char BlockExtractorPass::ID = 0; 188INITIALIZE_PASS(BlockExtractorPass, "extract-blocks", 189 "Extract Basic Blocks From Module (for bugpoint use)", 190 false, false) 191 192// createBlockExtractorPass - This pass extracts all blocks (except those 193// specified in the argument list) from the functions in the module. 194// 195ModulePass *llvm::createBlockExtractorPass() { 196 return new BlockExtractorPass(); 197} 198 199void BlockExtractorPass::LoadFile(const char *Filename) { 200 // Load the BlockFile... 201 std::ifstream In(Filename); 202 if (!In.good()) { 203 errs() << "WARNING: BlockExtractor couldn't load file '" << Filename 204 << "'!\n"; 205 return; 206 } 207 while (In) { 208 std::string FunctionName, BlockName; 209 In >> FunctionName; 210 In >> BlockName; 211 if (!BlockName.empty()) 212 BlocksToNotExtractByName.push_back( 213 std::make_pair(FunctionName, BlockName)); 214 } 215} 216 217/// SplitLandingPadPreds - The landing pad needs to be extracted with the invoke 218/// instruction. The critical edge breaker will refuse to break critical edges 219/// to a landing pad. So do them here. After this method runs, all landing pads 220/// should have only one predecessor. 221void BlockExtractorPass::SplitLandingPadPreds(Function *F) { 222 for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) { 223 InvokeInst *II = dyn_cast<InvokeInst>(I); 224 if (!II) continue; 225 BasicBlock *Parent = II->getParent(); 226 BasicBlock *LPad = II->getUnwindDest(); 227 228 // Look through the landing pad's predecessors. If one of them ends in an 229 // 'invoke', then we want to split the landing pad. 230 bool Split = false; 231 for (pred_iterator 232 PI = pred_begin(LPad), PE = pred_end(LPad); PI != PE; ++PI) { 233 BasicBlock *BB = *PI; 234 if (BB->isLandingPad() && BB != Parent && 235 isa<InvokeInst>(Parent->getTerminator())) { 236 Split = true; 237 break; 238 } 239 } 240 241 if (!Split) continue; 242 243 SmallVector<BasicBlock*, 2> NewBBs; 244 SplitLandingPadPredecessors(LPad, Parent, ".1", ".2", 0, NewBBs); 245 } 246} 247 248bool BlockExtractorPass::runOnModule(Module &M) { 249 std::set<BasicBlock*> TranslatedBlocksToNotExtract; 250 for (unsigned i = 0, e = BlocksToNotExtract.size(); i != e; ++i) { 251 BasicBlock *BB = BlocksToNotExtract[i]; 252 Function *F = BB->getParent(); 253 254 // Map the corresponding function in this module. 255 Function *MF = M.getFunction(F->getName()); 256 assert(MF->getFunctionType() == F->getFunctionType() && "Wrong function?"); 257 258 // Figure out which index the basic block is in its function. 259 Function::iterator BBI = MF->begin(); 260 std::advance(BBI, std::distance(F->begin(), Function::iterator(BB))); 261 TranslatedBlocksToNotExtract.insert(BBI); 262 } 263 264 while (!BlocksToNotExtractByName.empty()) { 265 // There's no way to find BBs by name without looking at every BB inside 266 // every Function. Fortunately, this is always empty except when used by 267 // bugpoint in which case correctness is more important than performance. 268 269 std::string &FuncName = BlocksToNotExtractByName.back().first; 270 std::string &BlockName = BlocksToNotExtractByName.back().second; 271 272 for (Module::iterator FI = M.begin(), FE = M.end(); FI != FE; ++FI) { 273 Function &F = *FI; 274 if (F.getName() != FuncName) continue; 275 276 for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE; ++BI) { 277 BasicBlock &BB = *BI; 278 if (BB.getName() != BlockName) continue; 279 280 TranslatedBlocksToNotExtract.insert(BI); 281 } 282 } 283 284 BlocksToNotExtractByName.pop_back(); 285 } 286 287 // Now that we know which blocks to not extract, figure out which ones we WANT 288 // to extract. 289 std::vector<BasicBlock*> BlocksToExtract; 290 for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) { 291 SplitLandingPadPreds(&*F); 292 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) 293 if (!TranslatedBlocksToNotExtract.count(BB)) 294 BlocksToExtract.push_back(BB); 295 } 296 297 for (unsigned i = 0, e = BlocksToExtract.size(); i != e; ++i) { 298 SmallVector<BasicBlock*, 2> BlocksToExtractVec; 299 BlocksToExtractVec.push_back(BlocksToExtract[i]); 300 if (const InvokeInst *II = 301 dyn_cast<InvokeInst>(BlocksToExtract[i]->getTerminator())) 302 BlocksToExtractVec.push_back(II->getUnwindDest()); 303 CodeExtractor(BlocksToExtractVec).extractCodeRegion(); 304 } 305 306 return !BlocksToExtract.empty(); 307} 308