Exemplo n.º 1
0
// SimplifyFunction - Given information about callees, simplify the specified
// function if we have invokes to non-unwinding functions or code after calls to
// no-return functions.
bool PruneEH::SimplifyFunction(Function *F) {
  bool MadeChange = false;
  for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
    if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator()))
      if (II->doesNotThrow()) {
        SmallVector<Value*, 8> Args(II->op_begin(), II->op_end() - 3);
        // Insert a call instruction before the invoke.
        CallInst *Call = CallInst::Create(II->getCalledValue(),
                                          Args.begin(), Args.end(), "", II);
        Call->takeName(II);
        Call->setCallingConv(II->getCallingConv());
        Call->setAttributes(II->getAttributes());
        Call->setDebugLoc(II->getDebugLoc());

        // Anything that used the value produced by the invoke instruction
        // now uses the value produced by the call instruction.  Note that we
        // do this even for void functions and calls with no uses so that the
        // callgraph edge is updated.
        II->replaceAllUsesWith(Call);
        BasicBlock *UnwindBlock = II->getUnwindDest();
        UnwindBlock->removePredecessor(II->getParent());

        // Insert a branch to the normal destination right before the
        // invoke.
        BranchInst::Create(II->getNormalDest(), II);

        // Finally, delete the invoke instruction!
        BB->getInstList().pop_back();

        // If the unwind block is now dead, nuke it.
        if (pred_begin(UnwindBlock) == pred_end(UnwindBlock))
          DeleteBasicBlock(UnwindBlock);  // Delete the new BB.

        ++NumRemoved;
        MadeChange = true;
      }

    for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; )
      if (CallInst *CI = dyn_cast<CallInst>(I++))
        if (CI->doesNotReturn() && !isa<UnreachableInst>(I)) {
          // This call calls a function that cannot return.  Insert an
          // unreachable instruction after it and simplify the code.  Do this
          // by splitting the BB, adding the unreachable, then deleting the
          // new BB.
          BasicBlock *New = BB->splitBasicBlock(I);

          // Remove the uncond branch and add an unreachable.
          BB->getInstList().pop_back();
          new UnreachableInst(BB->getContext(), BB);

          DeleteBasicBlock(New);  // Delete the new BB.
          MadeChange = true;
          ++NumUnreach;
          break;
        }
  }

  return MadeChange;
}
Exemplo n.º 2
0
// SimplifyFunction - Given information about callees, simplify the specified
// function if we have invokes to non-unwinding functions or code after calls to
// no-return functions.
static bool SimplifyFunction(Function *F, CallGraph &CG) {
  bool MadeChange = false;
  for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
    if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator()))
      if (II->doesNotThrow() && canSimplifyInvokeNoUnwind(F)) {
        BasicBlock *UnwindBlock = II->getUnwindDest();
        removeUnwindEdge(&*BB);

        // If the unwind block is now dead, nuke it.
        if (pred_empty(UnwindBlock))
          DeleteBasicBlock(UnwindBlock, CG);  // Delete the new BB.

        ++NumRemoved;
        MadeChange = true;
      }

    for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; )
      if (CallInst *CI = dyn_cast<CallInst>(I++))
        if (CI->doesNotReturn() && !isa<UnreachableInst>(I)) {
          // This call calls a function that cannot return.  Insert an
          // unreachable instruction after it and simplify the code.  Do this
          // by splitting the BB, adding the unreachable, then deleting the
          // new BB.
          BasicBlock *New = BB->splitBasicBlock(I);

          // Remove the uncond branch and add an unreachable.
          BB->getInstList().pop_back();
          new UnreachableInst(BB->getContext(), &*BB);

          DeleteBasicBlock(New, CG);  // Delete the new BB.
          MadeChange = true;
          ++NumUnreach;
          break;
        }
  }

  return MadeChange;
}
Exemplo n.º 3
0
bool ReduceCrashingBlocks::TestBlocks(std::vector<const BasicBlock*> &BBs) {
  // Clone the program to try hacking it apart...
  ValueToValueMapTy VMap;
  Module *M = CloneModule(BD.getProgram(), VMap);

  // Convert list to set for fast lookup...
  SmallPtrSet<BasicBlock*, 8> Blocks;
  for (unsigned i = 0, e = BBs.size(); i != e; ++i)
    Blocks.insert(cast<BasicBlock>(VMap[BBs[i]]));

  outs() << "Checking for crash with only these blocks:";
  unsigned NumPrint = Blocks.size();
  if (NumPrint > 10) NumPrint = 10;
  for (unsigned i = 0, e = NumPrint; i != e; ++i)
    outs() << " " << BBs[i]->getName();
  if (NumPrint < Blocks.size())
    outs() << "... <" << Blocks.size() << " total>";
  outs() << ": ";

  // Loop over and delete any hack up any blocks that are not listed...
  for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
    for (Function::iterator BB = I->begin(), E = I->end(); BB != E; ++BB)
      if (!Blocks.count(&*BB) && BB->getTerminator()->getNumSuccessors()) {
        // Loop over all of the successors of this block, deleting any PHI nodes
        // that might include it.
        for (succ_iterator SI = succ_begin(&*BB), E = succ_end(&*BB); SI != E;
             ++SI)
          (*SI)->removePredecessor(&*BB);

        TerminatorInst *BBTerm = BB->getTerminator();

        if (!BB->getTerminator()->getType()->isVoidTy())
          BBTerm->replaceAllUsesWith(Constant::getNullValue(BBTerm->getType()));

        // Replace the old terminator instruction.
        BB->getInstList().pop_back();
        new UnreachableInst(BB->getContext(), &*BB);
      }

  // The CFG Simplifier pass may delete one of the basic blocks we are
  // interested in.  If it does we need to take the block out of the list.  Make
  // a "persistent mapping" by turning basic blocks into <function, name> pairs.
  // This won't work well if blocks are unnamed, but that is just the risk we
  // have to take.
  std::vector<std::pair<std::string, std::string> > BlockInfo;

  for (BasicBlock *BB : Blocks)
    BlockInfo.emplace_back(BB->getParent()->getName(), BB->getName());

  // Now run the CFG simplify pass on the function...
  std::vector<std::string> Passes;
  Passes.push_back("simplifycfg");
  Passes.push_back("verify");
  std::unique_ptr<Module> New = BD.runPassesOn(M, Passes);
  delete M;
  if (!New) {
    errs() << "simplifycfg failed!\n";
    exit(1);
  }
  M = New.release();

  // Try running on the hacked up program...
  if (TestFn(BD, M)) {
    BD.setNewProgram(M);      // It crashed, keep the trimmed version...

    // Make sure to use basic block pointers that point into the now-current
    // module, and that they don't include any deleted blocks.
    BBs.clear();
    const ValueSymbolTable &GST = M->getValueSymbolTable();
    for (unsigned i = 0, e = BlockInfo.size(); i != e; ++i) {
      Function *F = cast<Function>(GST.lookup(BlockInfo[i].first));
      ValueSymbolTable &ST = F->getValueSymbolTable();
      Value* V = ST.lookup(BlockInfo[i].second);
      if (V && V->getType() == Type::getLabelTy(V->getContext()))
        BBs.push_back(cast<BasicBlock>(V));
    }
    return true;
  }
  delete M;  // It didn't crash, try something else.
  return false;
}