lib/Transforms/IPO/LoopExtractor.cpp

   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/LoopInfo.h"
  24 #include "llvm/Support/CommandLine.h"
  25 #include "llvm/Support/Compiler.h"
  26 #include "llvm/Transforms/Scalar.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   // FIXME: This is not a function pass, but the PassManager doesn't allow
  37   // Module passes to require FunctionPasses, so we can't get loop info if we're
  38   // not a function pass.
  39   struct VISIBILITY_HIDDEN LoopExtractor : public FunctionPass {
  40     static char ID; // Pass identification, replacement for typeid
  41     unsigned NumLoops;
  42
  43     explicit LoopExtractor(unsigned numLoops = ~0)
  44       : FunctionPass(&ID), NumLoops(numLoops) {}
  45
  46     virtual bool runOnFunction(Function &F);
  47
  48     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
  49       AU.addRequiredID(BreakCriticalEdgesID);
  50       AU.addRequiredID(LoopSimplifyID);
  51       AU.addRequired<DominatorTree>();
  52       AU.addRequired<LoopInfo>();
  53     }
  54   };
  55 }
  56
  57 char LoopExtractor::ID = 0;
  58 static RegisterPass<LoopExtractor>
  59 X("loop-extract", "Extract loops into new functions");
  60
  61 namespace {
  62   /// SingleLoopExtractor - For bugpoint.
  63   struct SingleLoopExtractor : public LoopExtractor {
  64     static char ID; // Pass identification, replacement for typeid
  65     SingleLoopExtractor() : LoopExtractor(1) {}
  66   };
  67 } // End anonymous namespace
  68
  69 char SingleLoopExtractor::ID = 0;
  70 static RegisterPass<SingleLoopExtractor>
  71 Y("loop-extract-single", "Extract at most one loop into a new function");
  72
  73 // createLoopExtractorPass - This pass extracts all natural loops from the
  74 // program into a function if it can.
  75 //
  76 FunctionPass *llvm::createLoopExtractorPass() { return new LoopExtractor(); }
  77
  78 bool LoopExtractor::runOnFunction(Function &F) {
  79   LoopInfo &LI = getAnalysis<LoopInfo>();
  80
  81   // If this function has no loops, there is nothing to do.
  82   if (LI.empty())
  83     return false;
  84
  85   DominatorTree &DT = getAnalysis<DominatorTree>();
  86
  87   // If there is more than one top-level loop in this function, extract all of
  88   // the loops.
  89   bool Changed = false;
  90   if (LI.end()-LI.begin() > 1) {
  91     for (LoopInfo::iterator i = LI.begin(), e = LI.end(); i != e; ++i) {
  92       if (NumLoops == 0) return Changed;
  93       --NumLoops;
  94       Changed |= ExtractLoop(DT, *i) != 0;
  95       ++NumExtracted;
  96     }
  97   } else {
  98     // Otherwise there is exactly one top-level loop.  If this function is more
  99     // than a minimal wrapper around the loop, extract the loop.
 100     Loop *TLL = *LI.begin();
 101     bool ShouldExtractLoop = false;
 102
 103     // Extract the loop if the entry block doesn't branch to the loop header.
 104     TerminatorInst *EntryTI = F.getEntryBlock().getTerminator();
 105     if (!isa<BranchInst>(EntryTI) ||
 106         !cast<BranchInst>(EntryTI)->isUnconditional() ||
 107         EntryTI->getSuccessor(0) != TLL->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       TLL->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       if (NumLoops == 0) return Changed;
 123       --NumLoops;
 124       Changed |= ExtractLoop(DT, TLL) != 0;
 125       ++NumExtracted;
 126     } else {
 127       // Okay, this function is a minimal container around the specified loop.
 128       // If we extract the loop, we will continue to just keep extracting it
 129       // infinitely... so don't extract it.  However, if the loop contains any
 130       // subloops, extract them.
 131       for (Loop::iterator i = TLL->begin(), e = TLL->end(); i != e; ++i) {
 132         if (NumLoops == 0) return Changed;
 133         --NumLoops;
 134         Changed |= ExtractLoop(DT, *i) != 0;
 135         ++NumExtracted;
 136       }
 137     }
 138   }
 139
 140   return Changed;
 141 }
 142
 143 // createSingleLoopExtractorPass - This pass extracts one natural loop from the
 144 // program into a function if it can.  This is used by bugpoint.
 145 //
 146 FunctionPass *llvm::createSingleLoopExtractorPass() {
 147   return new SingleLoopExtractor();
 148 }
 149
 150
 151 // BlockFile - A file which contains a list of blocks that should not be
 152 // extracted.
 153 static cl::opt<std::string>
 154 BlockFile("extract-blocks-file", cl::value_desc("filename"),
 155           cl::desc("A file containing list of basic blocks to not extract"),
 156           cl::Hidden);
 157
 158 namespace {
 159   /// BlockExtractorPass - This pass is used by bugpoint to extract all blocks
 160   /// from the module into their own functions except for those specified by the
 161   /// BlocksToNotExtract list.
 162   class BlockExtractorPass : public ModulePass {
 163     void LoadFile(const char *Filename);
 164
 165     std::vector<BasicBlock*> BlocksToNotExtract;
 166     std::vector<std::pair<std::string, std::string> > BlocksToNotExtractByName;
 167   public:
 168     static char ID; // Pass identification, replacement for typeid
 169     explicit BlockExtractorPass(const std::vector<BasicBlock*> &B)
 170       : ModulePass(&ID), BlocksToNotExtract(B) {
 171       if (!BlockFile.empty())
 172         LoadFile(BlockFile.c_str());
 173     }
 174     BlockExtractorPass() : ModulePass(&ID) {}
 175
 176     bool runOnModule(Module &M);
 177   };
 178 }
 179
 180 char BlockExtractorPass::ID = 0;
 181 static RegisterPass<BlockExtractorPass>
 182 XX("extract-blocks", "Extract Basic Blocks From Module (for bugpoint use)");
 183
 184 // createBlockExtractorPass - This pass extracts all blocks (except those
 185 // specified in the argument list) from the functions in the module.
 186 //
 187 ModulePass *llvm::createBlockExtractorPass(const std::vector<BasicBlock*> &BTNE)
 188 {
 189   return new BlockExtractorPass(BTNE);
 190 }
 191
 192 void BlockExtractorPass::LoadFile(const char *Filename) {
 193   // Load the BlockFile...
 194   std::ifstream In(Filename);
 195   if (!In.good()) {
 196     cerr << "WARNING: BlockExtractor couldn't load file '" << Filename
 197          << "'!\n";
 198     return;
 199   }
 200   while (In) {
 201     std::string FunctionName, BlockName;
 202     In >> FunctionName;
 203     In >> BlockName;
 204     if (!BlockName.empty())
 205       BlocksToNotExtractByName.push_back(
 206           std::make_pair(FunctionName, BlockName));
 207   }
 208 }
 209
 210 bool BlockExtractorPass::runOnModule(Module &M) {
 211   std::set<BasicBlock*> TranslatedBlocksToNotExtract;
 212   for (unsigned i = 0, e = BlocksToNotExtract.size(); i != e; ++i) {
 213     BasicBlock *BB = BlocksToNotExtract[i];
 214     Function *F = BB->getParent();
 215
 216     // Map the corresponding function in this module.
 217     Function *MF = M.getFunction(F->getName());
 218     assert(MF->getFunctionType() == F->getFunctionType() && "Wrong function?");
 219
 220     // Figure out which index the basic block is in its function.
 221     Function::iterator BBI = MF->begin();
 222     std::advance(BBI, std::distance(F->begin(), Function::iterator(BB)));
 223     TranslatedBlocksToNotExtract.insert(BBI);
 224   }
 225
 226   while (!BlocksToNotExtractByName.empty()) {
 227     // There's no way to find BBs by name without looking at every BB inside
 228     // every Function. Fortunately, this is always empty except when used by
 229     // bugpoint in which case correctness is more important than performance.
 230
 231     std::string &FuncName  = BlocksToNotExtractByName.back().first;
 232     std::string &BlockName = BlocksToNotExtractByName.back().second;
 233
 234     for (Module::iterator FI = M.begin(), FE = M.end(); FI != FE; ++FI) {
 235       Function &F = *FI;
 236       if (F.getName() != FuncName) continue;
 237
 238       for (Function::iterator BI = F.begin(), BE = F.end(); BI != BE; ++BI) {
 239         BasicBlock &BB = *BI;
 240         if (BB.getName() != BlockName) continue;
 241
 242         TranslatedBlocksToNotExtract.insert(BI);
 243       }
 244     }
 245
 246     BlocksToNotExtractByName.pop_back();
 247   }
 248
 249   // Now that we know which blocks to not extract, figure out which ones we WANT
 250   // to extract.
 251   std::vector<BasicBlock*> BlocksToExtract;
 252   for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F)
 253     for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
 254       if (!TranslatedBlocksToNotExtract.count(BB))
 255         BlocksToExtract.push_back(BB);
 256
 257   for (unsigned i = 0, e = BlocksToExtract.size(); i != e; ++i)
 258     ExtractBasicBlock(BlocksToExtract[i]);
 259
 260   return !BlocksToExtract.empty();
 261 }