//===- LoopExtractor.cpp - Extract each loop into a new function ----------===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // A pass wrapper around the ExtractLoop() scalar transformation to extract each // top-level loop into its own new function. If the loop is the ONLY loop in a // given function, it is not touched. This is a pass most useful for debugging // via bugpoint. // //===----------------------------------------------------------------------===// #include "llvm/Transforms/IPO.h" #include "llvm/ADT/Statistic.h" #include "llvm/Analysis/LoopPass.h" #include "llvm/IR/Dominators.h" #include "llvm/IR/Instructions.h" #include "llvm/IR/Module.h" #include "llvm/Pass.h" #include "llvm/Support/CommandLine.h" #include "llvm/Transforms/Scalar.h" #include "llvm/Transforms/Utils/BasicBlockUtils.h" #include "llvm/Transforms/Utils/CodeExtractor.h" #include <fstream> #include <set> using namespace llvm; #define DEBUG_TYPE "loop-extract" STATISTIC(NumExtracted, "Number of loops extracted"); namespace { struct LoopExtractor : public LoopPass { static char ID; // Pass identification, replacement for typeid unsigned NumLoops; explicit LoopExtractor(unsigned numLoops = ~0) : LoopPass(ID), NumLoops(numLoops) { initializeLoopExtractorPass(*PassRegistry::getPassRegistry()); } bool runOnLoop(Loop *L, LPPassManager &LPM) override; void getAnalysisUsage(AnalysisUsage &AU) const override { AU.addRequiredID(BreakCriticalEdgesID); AU.addRequiredID(LoopSimplifyID); AU.addRequired<DominatorTreeWrapperPass>(); } }; } char LoopExtractor::ID = 0; INITIALIZE_PASS_BEGIN(LoopExtractor, "loop-extract", "Extract loops into new functions", false, false) INITIALIZE_PASS_DEPENDENCY(BreakCriticalEdges) INITIALIZE_PASS_DEPENDENCY(LoopSimplify) INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass) INITIALIZE_PASS_END(LoopExtractor, "loop-extract", "Extract loops into new functions", false, false) namespace { /// SingleLoopExtractor - For bugpoint. struct SingleLoopExtractor : public LoopExtractor { static char ID; // Pass identification, replacement for typeid SingleLoopExtractor() : LoopExtractor(1) {} }; } // End anonymous namespace char SingleLoopExtractor::ID = 0; INITIALIZE_PASS(SingleLoopExtractor, "loop-extract-single", "Extract at most one loop into a new function", false, false) // createLoopExtractorPass - This pass extracts all natural loops from the // program into a function if it can. // Pass *llvm::createLoopExtractorPass() { return new LoopExtractor(); } bool LoopExtractor::runOnLoop(Loop *L, LPPassManager &LPM) { if (skipOptnoneFunction(L)) return false; // Only visit top-level loops. if (L->getParentLoop()) return false; // If LoopSimplify form is not available, stay out of trouble. if (!L->isLoopSimplifyForm()) return false; DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree(); bool Changed = false; // If there is more than one top-level loop in this function, extract all of // the loops. Otherwise there is exactly one top-level loop; in this case if // this function is more than a minimal wrapper around the loop, extract // the loop. bool ShouldExtractLoop = false; // Extract the loop if the entry block doesn't branch to the loop header. TerminatorInst *EntryTI = L->getHeader()->getParent()->getEntryBlock().getTerminator(); if (!isa<BranchInst>(EntryTI) || !cast<BranchInst>(EntryTI)->isUnconditional() || EntryTI->getSuccessor(0) != L->getHeader()) { ShouldExtractLoop = true; } else { // Check to see if any exits from the loop are more than just return // blocks. SmallVector<BasicBlock*, 8> ExitBlocks; L->getExitBlocks(ExitBlocks); for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) if (!isa<ReturnInst>(ExitBlocks[i]->getTerminator())) { ShouldExtractLoop = true; break; } } if (ShouldExtractLoop) { // We must omit landing pads. Landing pads must accompany the invoke // instruction. But this would result in a loop in the extracted // function. An infinite cycle occurs when it tries to extract that loop as // well. SmallVector<BasicBlock*, 8> ExitBlocks; L->getExitBlocks(ExitBlocks); for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) if (ExitBlocks[i]->isLandingPad()) { ShouldExtractLoop = false; break; } } if (ShouldExtractLoop) { if (NumLoops == 0) return Changed; --NumLoops; CodeExtractor Extractor(DT, *L); if (Extractor.extractCodeRegion() != nullptr) { Changed = true; // After extraction, the loop is replaced by a function call, so // we shouldn't try to run any more loop passes on it. LPM.deleteLoopFromQueue(L); } ++NumExtracted; } return Changed; } // createSingleLoopExtractorPass - This pass extracts one natural loop from the // program into a function if it can. This is used by bugpoint. // Pass *llvm::createSingleLoopExtractorPass() { return new SingleLoopExtractor(); } // BlockFile - A file which contains a list of blocks that should not be // extracted. static cl::opt<std::string> BlockFile("extract-blocks-file", cl::value_desc("filename"), cl::desc("A file containing list of basic blocks to not extract"), cl::Hidden); namespace { /// BlockExtractorPass - This pass is used by bugpoint to extract all blocks /// from the module into their own functions except for those specified by the /// BlocksToNotExtract list. class BlockExtractorPass : public ModulePass { void LoadFile(const char *Filename); void SplitLandingPadPreds(Function *F); std::vector<BasicBlock*> BlocksToNotExtract; std::vector<std::pair<std::string, std::string> > BlocksToNotExtractByName; public: static char ID; // Pass identification, replacement for typeid BlockExtractorPass() : ModulePass(ID) { if (!BlockFile.empty()) LoadFile(BlockFile.c_str()); } bool runOnModule(Module &M) override; }; } char BlockExtractorPass::ID = 0; INITIALIZE_PASS(BlockExtractorPass, "extract-blocks", "Extract Basic Blocks From Module (for bugpoint use)", false, false) // createBlockExtractorPass - This pass extracts all blocks (except those // specified in the argument list) from the functions in the module. // ModulePass *llvm::createBlockExtractorPass() { return new BlockExtractorPass(); } void BlockExtractorPass::LoadFile(const char *Filename) { // Load the BlockFile... std::ifstream In(Filename); if (!In.good()) { errs() << "WARNING: BlockExtractor couldn't load file '" << Filename << "'!\n"; return; } while (In) { std::string FunctionName, BlockName; In >> FunctionName; In >> BlockName; if (!BlockName.empty()) BlocksToNotExtractByName.push_back( std::make_pair(FunctionName, BlockName)); } } /// SplitLandingPadPreds - The landing pad needs to be extracted with the invoke /// instruction. The critical edge breaker will refuse to break critical edges /// to a landing pad. So do them here. After this method runs, all landing pads /// should have only one predecessor. void BlockExtractorPass::SplitLandingPadPreds(Function *F) { for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) { InvokeInst *II = dyn_cast<InvokeInst>(I); if (!II) continue; BasicBlock *Parent = II->getParent(); BasicBlock *LPad = II->getUnwindDest(); // Look through the landing pad's predecessors. If one of them ends in an // 'invoke', then we want to split the landing pad. bool Split = false; for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad); PI != PE; ++PI) { BasicBlock *BB = *PI; if (BB->isLandingPad() && BB != Parent && isa<InvokeInst>(Parent->getTerminator())) { Split = true; break; } } if (!Split) continue; SmallVector<BasicBlock*, 2> NewBBs; SplitLandingPadPredecessors(LPad, Parent, ".1", ".2", nullptr, NewBBs); } } bool BlockExtractorPass::runOnModule(Module &M) { std::set<BasicBlock*> TranslatedBlocksToNotExtract; for (unsigned i = 0, e = BlocksToNotExtract.size(); i != e; ++i) { BasicBlock *BB = BlocksToNotExtract[i]; Function *F = BB->getParent(); // Map the corresponding function in this module. Function *MF = M.getFunction(F->getName()); assert(MF->getFunctionType() == F->getFunctionType() && "Wrong function?"); // Figure out which index the basic block is in its function. Function::iterator BBI = MF->begin(); std::advance(BBI, std::distance(F->begin(), Function::iterator(BB))); TranslatedBlocksToNotExtract.insert(BBI); } while (!BlocksToNotExtractByName.empty()) { // There's no way to find BBs by name without looking at every BB inside // every Function. Fortunately, this is always empty except when used by // bugpoint in which case correctness is more important than performance. std::string &FuncName = BlocksToNotExtractByName.back().first; std::string &BlockName = BlocksToNotExtractByName.back().second; for (Module::iterator FI = M.begin(), FE = M.end(); FI != FE; ++FI) { Function &F = *FI; if (F.getName() != FuncName) continue; for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE; ++BI) { BasicBlock &BB = *BI; if (BB.getName() != BlockName) continue; TranslatedBlocksToNotExtract.insert(BI); } } BlocksToNotExtractByName.pop_back(); } // Now that we know which blocks to not extract, figure out which ones we WANT // to extract. std::vector<BasicBlock*> BlocksToExtract; for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) { SplitLandingPadPreds(&*F); for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) if (!TranslatedBlocksToNotExtract.count(BB)) BlocksToExtract.push_back(BB); } for (unsigned i = 0, e = BlocksToExtract.size(); i != e; ++i) { SmallVector<BasicBlock*, 2> BlocksToExtractVec; BlocksToExtractVec.push_back(BlocksToExtract[i]); if (const InvokeInst *II = dyn_cast<InvokeInst>(BlocksToExtract[i]->getTerminator())) BlocksToExtractVec.push_back(II->getUnwindDest()); CodeExtractor(BlocksToExtractVec).extractCodeRegion(); } return !BlocksToExtract.empty(); }