LoopExtractor.cpp revision f5a86f45e75ec744c203270ffa03659eb0a220c1
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/FunctionUtils.h" 27#include "llvm/ADT/Statistic.h" 28#include <fstream> 29#include <set> 30using namespace llvm; 31 32STATISTIC(NumExtracted, "Number of loops extracted"); 33 34namespace { 35 struct LoopExtractor : public LoopPass { 36 static char ID; // Pass identification, replacement for typeid 37 unsigned NumLoops; 38 39 explicit LoopExtractor(unsigned numLoops = ~0) 40 : LoopPass(&ID), NumLoops(numLoops) {} 41 42 virtual bool runOnLoop(Loop *L, LPPassManager &LPM); 43 44 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 45 AU.addRequiredID(BreakCriticalEdgesID); 46 AU.addRequiredID(LoopSimplifyID); 47 AU.addRequired<DominatorTree>(); 48 } 49 }; 50} 51 52char LoopExtractor::ID = 0; 53static RegisterPass<LoopExtractor> 54X("loop-extract", "Extract loops into new functions"); 55 56namespace { 57 /// SingleLoopExtractor - For bugpoint. 58 struct SingleLoopExtractor : public LoopExtractor { 59 static char ID; // Pass identification, replacement for typeid 60 SingleLoopExtractor() : LoopExtractor(1) {} 61 }; 62} // End anonymous namespace 63 64char SingleLoopExtractor::ID = 0; 65static RegisterPass<SingleLoopExtractor> 66Y("loop-extract-single", "Extract at most one loop into a new function"); 67 68// createLoopExtractorPass - This pass extracts all natural loops from the 69// program into a function if it can. 70// 71Pass *llvm::createLoopExtractorPass() { return new LoopExtractor(); } 72 73bool LoopExtractor::runOnLoop(Loop *L, LPPassManager &LPM) { 74 // Only visit top-level loops. 75 if (L->getParentLoop()) 76 return false; 77 78 DominatorTree &DT = getAnalysis<DominatorTree>(); 79 bool Changed = false; 80 81 // If there is more than one top-level loop in this function, extract all of 82 // the loops. Otherwise there is exactly one top-level loop; in this case if 83 // this function is more than a minimal wrapper around the loop, extract 84 // the loop. 85 bool ShouldExtractLoop = false; 86 87 // Extract the loop if the entry block doesn't branch to the loop header. 88 TerminatorInst *EntryTI = 89 L->getHeader()->getParent()->getEntryBlock().getTerminator(); 90 if (!isa<BranchInst>(EntryTI) || 91 !cast<BranchInst>(EntryTI)->isUnconditional() || 92 EntryTI->getSuccessor(0) != L->getHeader()) 93 ShouldExtractLoop = true; 94 else { 95 // Check to see if any exits from the loop are more than just return 96 // blocks. 97 SmallVector<BasicBlock*, 8> ExitBlocks; 98 L->getExitBlocks(ExitBlocks); 99 for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) 100 if (!isa<ReturnInst>(ExitBlocks[i]->getTerminator())) { 101 ShouldExtractLoop = true; 102 break; 103 } 104 } 105 if (ShouldExtractLoop) { 106 if (NumLoops == 0) return Changed; 107 --NumLoops; 108 if (ExtractLoop(DT, L) != 0) { 109 Changed = true; 110 // After extraction, the loop is replaced by a function call, so 111 // we shouldn't try to run any more loop passes on it. 112 LPM.deleteLoopFromQueue(L); 113 } 114 ++NumExtracted; 115 } 116 117 return Changed; 118} 119 120// createSingleLoopExtractorPass - This pass extracts one natural loop from the 121// program into a function if it can. This is used by bugpoint. 122// 123Pass *llvm::createSingleLoopExtractorPass() { 124 return new SingleLoopExtractor(); 125} 126 127 128// BlockFile - A file which contains a list of blocks that should not be 129// extracted. 130static cl::opt<std::string> 131BlockFile("extract-blocks-file", cl::value_desc("filename"), 132 cl::desc("A file containing list of basic blocks to not extract"), 133 cl::Hidden); 134 135namespace { 136 /// BlockExtractorPass - This pass is used by bugpoint to extract all blocks 137 /// from the module into their own functions except for those specified by the 138 /// BlocksToNotExtract list. 139 class BlockExtractorPass : public ModulePass { 140 void LoadFile(const char *Filename); 141 142 std::vector<BasicBlock*> BlocksToNotExtract; 143 std::vector<std::pair<std::string, std::string> > BlocksToNotExtractByName; 144 public: 145 static char ID; // Pass identification, replacement for typeid 146 explicit BlockExtractorPass(const std::vector<BasicBlock*> &B) 147 : ModulePass(&ID), BlocksToNotExtract(B) { 148 if (!BlockFile.empty()) 149 LoadFile(BlockFile.c_str()); 150 } 151 BlockExtractorPass() : ModulePass(&ID) {} 152 153 bool runOnModule(Module &M); 154 }; 155} 156 157char BlockExtractorPass::ID = 0; 158static RegisterPass<BlockExtractorPass> 159XX("extract-blocks", "Extract Basic Blocks From Module (for bugpoint use)"); 160 161// createBlockExtractorPass - This pass extracts all blocks (except those 162// specified in the argument list) from the functions in the module. 163// 164ModulePass *llvm::createBlockExtractorPass(const std::vector<BasicBlock*> &BTNE) 165{ 166 return new BlockExtractorPass(BTNE); 167} 168 169void BlockExtractorPass::LoadFile(const char *Filename) { 170 // Load the BlockFile... 171 std::ifstream In(Filename); 172 if (!In.good()) { 173 errs() << "WARNING: BlockExtractor couldn't load file '" << Filename 174 << "'!\n"; 175 return; 176 } 177 while (In) { 178 std::string FunctionName, BlockName; 179 In >> FunctionName; 180 In >> BlockName; 181 if (!BlockName.empty()) 182 BlocksToNotExtractByName.push_back( 183 std::make_pair(FunctionName, BlockName)); 184 } 185} 186 187bool BlockExtractorPass::runOnModule(Module &M) { 188 std::set<BasicBlock*> TranslatedBlocksToNotExtract; 189 for (unsigned i = 0, e = BlocksToNotExtract.size(); i != e; ++i) { 190 BasicBlock *BB = BlocksToNotExtract[i]; 191 Function *F = BB->getParent(); 192 193 // Map the corresponding function in this module. 194 Function *MF = M.getFunction(F->getName()); 195 assert(MF->getFunctionType() == F->getFunctionType() && "Wrong function?"); 196 197 // Figure out which index the basic block is in its function. 198 Function::iterator BBI = MF->begin(); 199 std::advance(BBI, std::distance(F->begin(), Function::iterator(BB))); 200 TranslatedBlocksToNotExtract.insert(BBI); 201 } 202 203 while (!BlocksToNotExtractByName.empty()) { 204 // There's no way to find BBs by name without looking at every BB inside 205 // every Function. Fortunately, this is always empty except when used by 206 // bugpoint in which case correctness is more important than performance. 207 208 std::string &FuncName = BlocksToNotExtractByName.back().first; 209 std::string &BlockName = BlocksToNotExtractByName.back().second; 210 211 for (Module::iterator FI = M.begin(), FE = M.end(); FI != FE; ++FI) { 212 Function &F = *FI; 213 if (F.getName() != FuncName) continue; 214 215 for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE; ++BI) { 216 BasicBlock &BB = *BI; 217 if (BB.getName() != BlockName) continue; 218 219 TranslatedBlocksToNotExtract.insert(BI); 220 } 221 } 222 223 BlocksToNotExtractByName.pop_back(); 224 } 225 226 // Now that we know which blocks to not extract, figure out which ones we WANT 227 // to extract. 228 std::vector<BasicBlock*> BlocksToExtract; 229 for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) 230 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) 231 if (!TranslatedBlocksToNotExtract.count(BB)) 232 BlocksToExtract.push_back(BB); 233 234 for (unsigned i = 0, e = BlocksToExtract.size(); i != e; ++i) 235 ExtractBasicBlock(BlocksToExtract[i]); 236 237 return !BlocksToExtract.empty(); 238} 239