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;
}
// 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) {
  CallGraph &CG = getAnalysis<CallGraph>();
  bool MadeChange = false;
  for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
    if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator()))
      if (Function *F = II->getCalledFunction())
        if (DoesNotUnwind.count(CG[F])) {
          SmallVector<Value*, 8> Args(II->op_begin()+3, II->op_end());
          // Insert a call instruction before the invoke.
          CallInst *Call = new CallInst(II->getCalledValue(),
                                        &Args[0], Args.size(), "", II);
          Call->takeName(II);
          Call->setCallingConv(II->getCallingConv());

          // Anything that used the value produced by the invoke instruction
          // now uses the value produced by the call instruction.
          II->replaceAllUsesWith(Call);
          BasicBlock *UnwindBlock = II->getUnwindDest();
          UnwindBlock->removePredecessor(II->getParent());

          // Insert a branch to the normal destination right before the
          // invoke.
          new BranchInst(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 (Function *Callee = CI->getCalledFunction())
          if (DoesNotReturn.count(CG[Callee]) && !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);

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

  }
  return MadeChange;
}
Exemplo n.º 3
0
bool LowerInvoke::insertCheapEHSupport(Function &F) {
  bool Changed = false;
  for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
    if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
      SmallVector<Value*,16> CallArgs(II->op_begin(), II->op_end() - 3);
      // Insert a normal call instruction...
      CallInst *NewCall = CallInst::Create(II->getCalledValue(),
                                           CallArgs, "", II);
      NewCall->takeName(II);
      NewCall->setCallingConv(II->getCallingConv());
      NewCall->setAttributes(II->getAttributes());
      NewCall->setDebugLoc(II->getDebugLoc());
      II->replaceAllUsesWith(NewCall);

      // Insert an unconditional branch to the normal destination.
      BranchInst::Create(II->getNormalDest(), II);

      // Remove any PHI node entries from the exception destination.
      II->getUnwindDest()->removePredecessor(BB);

      // Remove the invoke instruction now.
      BB->getInstList().erase(II);

      ++NumInvokes; Changed = true;
    }
  return Changed;
}
Exemplo n.º 4
0
bool LowerInvoke::insertCheapEHSupport(Function &F) {
  bool Changed = false;
  for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
    if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
      std::vector<Value*> CallArgs(II->op_begin()+3, II->op_end());
      // Insert a normal call instruction...
      CallInst *NewCall = CallInst::Create(II->getCalledValue(),
                                           CallArgs.begin(), CallArgs.end(), "",II);
      NewCall->takeName(II);
      NewCall->setCallingConv(II->getCallingConv());
      NewCall->setAttributes(II->getAttributes());
      II->replaceAllUsesWith(NewCall);

      // Insert an unconditional branch to the normal destination.
      BranchInst::Create(II->getNormalDest(), II);

      // Remove any PHI node entries from the exception destination.
      II->getUnwindDest()->removePredecessor(BB);

      // Remove the invoke instruction now.
      BB->getInstList().erase(II);

      ++NumInvokes; Changed = true;
    } else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
      // Insert a new call to write(2, AbortMessage, AbortMessageLength);
      writeAbortMessage(UI);

      // Insert a call to abort()
      CallInst::Create(AbortFn, "", UI)->setTailCall();

      // Insert a return instruction.  This really should be a "barrier", as it
      // is unreachable.
      ReturnInst::Create(F.getContext(),
                         F.getReturnType() == Type::getVoidTy(F.getContext()) ?
                          0 : Constant::getNullValue(F.getReturnType()), UI);

      // Remove the unwind instruction now.
      BB->getInstList().erase(UI);

      ++NumUnwinds; Changed = true;
    }
  return Changed;
}
Exemplo n.º 5
0
bool Mutator::runOnModule(Module &M) {
	
  unsigned siteId = 0;
  
  OperatorManager   *OMgr = OperatorManager::getInstance();
  OperatorInfoList  oplst;

  // Loop through all functions within module
  for (Module::iterator F = M.begin(), ME = M.end(); F != ME; ++F) {	
    // Loop through all basic blocks within function
    for (Function::iterator B = F->begin(), FE = F->end(); B != FE; ++B) {
      // Loop through all instructions within basic block
      for (BasicBlock::iterator I = B->begin(), BE = B->end(); I != BE; I++) {
        // Consider only mutable instructions
        OMgr->getCompatibleOperators(I, oplst);
        
        bool mutated = false;
        for (OperatorInfoList::iterator opi = oplst.begin(); opi != oplst.end(); opi++) {
          cl::list<unsigned>::iterator sid = find (MutationIDS.begin(), MutationIDS.end(), siteId++);
          if (sid != MutationIDS.end()) {
            // One of the specified mutations was found
            if (!mutated) {
              MutationOperator *op = (*opi)->build();
              Value *newv = op->apply(I);
              //cerr << *I << " --> " << *newv << "\n";
              
              if (newv != NULL) {
                  ReplaceInstWithValue(B->getInstList(), I, newv);
              } else {
                  
              }
              mutated = true;
            } else {
              throw std::string("An instruction is being mutated twice! Aborting...");
            }
          }
		}
      }
    }
  }
  
  // notify change of program 
  return true;
}
Exemplo n.º 6
0
// This is basically the split basic block function but it does not create
// a new basic block.
void Decompiler::splitBasicBlockIntoBlock(Function::iterator Src,
  BasicBlock::iterator FirstInst, BasicBlock *Tgt) {
  assert(Src->getTerminator() && "Can't use splitBasicBlock on degenerate BB!");
  assert(FirstInst != Src->end() &&
         "Trying to get me to create degenerate basic block!");

  Tgt->moveAfter(Src);

  // Move all of the specified instructions from the original basic block into
  // the new basic block.
  Tgt->getInstList().splice(Tgt->end(), Src->getInstList(),
    FirstInst, Src->end());

  // Add a branch instruction to the newly formed basic block.
  BranchInst *BI = BranchInst::Create(Tgt, Src);
  // Set debugLoc to the instruction before the terminator's DebugLoc.
  // Note the pre-inc which can confuse folks.
  BI->setDebugLoc((++Src->rbegin())->getDebugLoc());

  // Now we must loop through all of the successors of the New block (which
  // _were_ the successors of the 'this' block), and update any PHI nodes in
  // successors.  If there were PHI nodes in the successors, then they need to
  // know that incoming branches will be from New, not from Old.
  //
  for (succ_iterator I = succ_begin(Tgt), E = succ_end(Tgt); I != E; ++I) {
    // Loop over any phi nodes in the basic block, updating the BB field of
    // incoming values...
    BasicBlock *Successor = *I;
    PHINode *PN;
    for (BasicBlock::iterator II = Successor->begin();
         (PN = dyn_cast<PHINode>(II)); ++II) {
      int IDX = PN->getBasicBlockIndex(Src);
      while (IDX != -1) {
        PN->setIncomingBlock((unsigned)IDX, Tgt);
        IDX = PN->getBasicBlockIndex(Src);
      }
    }
  }
}
Exemplo n.º 7
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;
}
// RemoveDeadStuffFromFunction - Remove any arguments and return values from F
// that are not in LiveValues. Transform the function and all of the callees of
// the function to not have these arguments and return values.
//
bool DAE::RemoveDeadStuffFromFunction(Function *F) {
  // Don't modify fully live functions
  if (LiveFunctions.count(F))
    return false;

  // Start by computing a new prototype for the function, which is the same as
  // the old function, but has fewer arguments and a different return type.
  FunctionType *FTy = F->getFunctionType();
  std::vector<Type*> Params;

  // Set up to build a new list of parameter attributes.
  SmallVector<AttributeWithIndex, 8> AttributesVec;
  const AttributeSet &PAL = F->getAttributes();

  // Find out the new return value.
  Type *RetTy = FTy->getReturnType();
  Type *NRetTy = NULL;
  unsigned RetCount = NumRetVals(F);

  // -1 means unused, other numbers are the new index
  SmallVector<int, 5> NewRetIdxs(RetCount, -1);
  std::vector<Type*> RetTypes;
  if (RetTy->isVoidTy()) {
    NRetTy = RetTy;
  } else {
    StructType *STy = dyn_cast<StructType>(RetTy);
    if (STy)
      // Look at each of the original return values individually.
      for (unsigned i = 0; i != RetCount; ++i) {
        RetOrArg Ret = CreateRet(F, i);
        if (LiveValues.erase(Ret)) {
          RetTypes.push_back(STy->getElementType(i));
          NewRetIdxs[i] = RetTypes.size() - 1;
        } else {
          ++NumRetValsEliminated;
          DEBUG(dbgs() << "DAE - Removing return value " << i << " from "
                << F->getName() << "\n");
        }
      }
    else
      // We used to return a single value.
      if (LiveValues.erase(CreateRet(F, 0))) {
        RetTypes.push_back(RetTy);
        NewRetIdxs[0] = 0;
      } else {
        DEBUG(dbgs() << "DAE - Removing return value from " << F->getName()
              << "\n");
        ++NumRetValsEliminated;
      }
    if (RetTypes.size() > 1)
      // More than one return type? Return a struct with them. Also, if we used
      // to return a struct and didn't change the number of return values,
      // return a struct again. This prevents changing {something} into
      // something and {} into void.
      // Make the new struct packed if we used to return a packed struct
      // already.
      NRetTy = StructType::get(STy->getContext(), RetTypes, STy->isPacked());
    else if (RetTypes.size() == 1)
      // One return type? Just a simple value then, but only if we didn't use to
      // return a struct with that simple value before.
      NRetTy = RetTypes.front();
    else if (RetTypes.size() == 0)
      // No return types? Make it void, but only if we didn't use to return {}.
      NRetTy = Type::getVoidTy(F->getContext());
  }

  assert(NRetTy && "No new return type found?");

  // The existing function return attributes.
  AttributeSet RAttrs = PAL.getRetAttributes();

  // Remove any incompatible attributes, but only if we removed all return
  // values. Otherwise, ensure that we don't have any conflicting attributes
  // here. Currently, this should not be possible, but special handling might be
  // required when new return value attributes are added.
  if (NRetTy->isVoidTy())
    RAttrs =
      AttributeSet::get(NRetTy->getContext(), AttributeSet::ReturnIndex,
                        AttrBuilder(RAttrs, AttributeSet::ReturnIndex).
                    removeAttributes(AttributeFuncs::typeIncompatible(NRetTy)));
  else
    assert(!AttrBuilder(RAttrs, AttributeSet::ReturnIndex).
             hasAttributes(AttributeFuncs::typeIncompatible(NRetTy)) &&
           "Return attributes no longer compatible?");

  if (RAttrs.hasAttributes(AttributeSet::ReturnIndex))
    AttributesVec.push_back(AttributeWithIndex::get(NRetTy->getContext(),
                                                    AttributeSet::ReturnIndex,
                                                    RAttrs));

  // Remember which arguments are still alive.
  SmallVector<bool, 10> ArgAlive(FTy->getNumParams(), false);
  // Construct the new parameter list from non-dead arguments. Also construct
  // a new set of parameter attributes to correspond. Skip the first parameter
  // attribute, since that belongs to the return value.
  unsigned i = 0;
  for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
       I != E; ++I, ++i) {
    RetOrArg Arg = CreateArg(F, i);
    if (LiveValues.erase(Arg)) {
      Params.push_back(I->getType());
      ArgAlive[i] = true;

      // Get the original parameter attributes (skipping the first one, that is
      // for the return value.
      if (PAL.hasAttributes(i + 1)) {
        AttributesVec.
          push_back(AttributeWithIndex::get(F->getContext(), i + 1,
                                            PAL.getParamAttributes(i + 1)));
        AttributesVec.back().Index = Params.size();
      }
    } else {
      ++NumArgumentsEliminated;
      DEBUG(dbgs() << "DAE - Removing argument " << i << " (" << I->getName()
            << ") from " << F->getName() << "\n");
    }
  }

  if (PAL.hasAttributes(AttributeSet::FunctionIndex))
    AttributesVec.push_back(AttributeWithIndex::get(F->getContext(),
                                                    AttributeSet::FunctionIndex,
                                                    PAL.getFnAttributes()));

  // Reconstruct the AttributesList based on the vector we constructed.
  AttributeSet NewPAL = AttributeSet::get(F->getContext(), AttributesVec);

  // Create the new function type based on the recomputed parameters.
  FunctionType *NFTy = FunctionType::get(NRetTy, Params, FTy->isVarArg());

  // No change?
  if (NFTy == FTy)
    return false;

  // Create the new function body and insert it into the module...
  Function *NF = Function::Create(NFTy, F->getLinkage());
  NF->copyAttributesFrom(F);
  NF->setAttributes(NewPAL);
  // Insert the new function before the old function, so we won't be processing
  // it again.
  F->getParent()->getFunctionList().insert(F, NF);
  NF->takeName(F);

  // Loop over all of the callers of the function, transforming the call sites
  // to pass in a smaller number of arguments into the new function.
  //
  std::vector<Value*> Args;
  while (!F->use_empty()) {
    CallSite CS(F->use_back());
    Instruction *Call = CS.getInstruction();

    AttributesVec.clear();
    const AttributeSet &CallPAL = CS.getAttributes();

    // The call return attributes.
    AttributeSet RAttrs = CallPAL.getRetAttributes();

    // Adjust in case the function was changed to return void.
    RAttrs =
      AttributeSet::get(NF->getContext(), AttributeSet::ReturnIndex,
                        AttrBuilder(RAttrs, AttributeSet::ReturnIndex).
      removeAttributes(AttributeFuncs::typeIncompatible(NF->getReturnType())));
    if (RAttrs.hasAttributes(AttributeSet::ReturnIndex))
      AttributesVec.push_back(AttributeWithIndex::get(NF->getContext(),
                                                      AttributeSet::ReturnIndex,
                                                      RAttrs));

    // Declare these outside of the loops, so we can reuse them for the second
    // loop, which loops the varargs.
    CallSite::arg_iterator I = CS.arg_begin();
    unsigned i = 0;
    // Loop over those operands, corresponding to the normal arguments to the
    // original function, and add those that are still alive.
    for (unsigned e = FTy->getNumParams(); i != e; ++I, ++i)
      if (ArgAlive[i]) {
        Args.push_back(*I);
        // Get original parameter attributes, but skip return attributes.
        if (CallPAL.hasAttributes(i + 1)) {
          AttributesVec.
            push_back(AttributeWithIndex::get(F->getContext(), i + 1,
                                            CallPAL.getParamAttributes(i + 1)));
          AttributesVec.back().Index = Args.size();
        }
      }

    // Push any varargs arguments on the list. Don't forget their attributes.
    for (CallSite::arg_iterator E = CS.arg_end(); I != E; ++I, ++i) {
      Args.push_back(*I);
      if (CallPAL.hasAttributes(i + 1)) {
        AttributesVec.
          push_back(AttributeWithIndex::get(F->getContext(), i + 1,
                                            CallPAL.getParamAttributes(i + 1)));
        AttributesVec.back().Index = Args.size();
      }
    }

    if (CallPAL.hasAttributes(AttributeSet::FunctionIndex))
      AttributesVec.push_back(AttributeWithIndex::get(Call->getContext(),
                                                      AttributeSet::FunctionIndex,
                                                      CallPAL.getFnAttributes()));

    // Reconstruct the AttributesList based on the vector we constructed.
    AttributeSet NewCallPAL = AttributeSet::get(F->getContext(), AttributesVec);

    Instruction *New;
    if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
      New = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
                               Args, "", Call);
      cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
      cast<InvokeInst>(New)->setAttributes(NewCallPAL);
    } else {
      New = CallInst::Create(NF, Args, "", Call);
      cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
      cast<CallInst>(New)->setAttributes(NewCallPAL);
      if (cast<CallInst>(Call)->isTailCall())
        cast<CallInst>(New)->setTailCall();
    }
    New->setDebugLoc(Call->getDebugLoc());

    Args.clear();

    if (!Call->use_empty()) {
      if (New->getType() == Call->getType()) {
        // Return type not changed? Just replace users then.
        Call->replaceAllUsesWith(New);
        New->takeName(Call);
      } else if (New->getType()->isVoidTy()) {
        // Our return value has uses, but they will get removed later on.
        // Replace by null for now.
        if (!Call->getType()->isX86_MMXTy())
          Call->replaceAllUsesWith(Constant::getNullValue(Call->getType()));
      } else {
        assert(RetTy->isStructTy() &&
               "Return type changed, but not into a void. The old return type"
               " must have been a struct!");
        Instruction *InsertPt = Call;
        if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
          BasicBlock::iterator IP = II->getNormalDest()->begin();
          while (isa<PHINode>(IP)) ++IP;
          InsertPt = IP;
        }

        // We used to return a struct. Instead of doing smart stuff with all the
        // uses of this struct, we will just rebuild it using
        // extract/insertvalue chaining and let instcombine clean that up.
        //
        // Start out building up our return value from undef
        Value *RetVal = UndefValue::get(RetTy);
        for (unsigned i = 0; i != RetCount; ++i)
          if (NewRetIdxs[i] != -1) {
            Value *V;
            if (RetTypes.size() > 1)
              // We are still returning a struct, so extract the value from our
              // return value
              V = ExtractValueInst::Create(New, NewRetIdxs[i], "newret",
                                           InsertPt);
            else
              // We are now returning a single element, so just insert that
              V = New;
            // Insert the value at the old position
            RetVal = InsertValueInst::Create(RetVal, V, i, "oldret", InsertPt);
          }
        // Now, replace all uses of the old call instruction with the return
        // struct we built
        Call->replaceAllUsesWith(RetVal);
        New->takeName(Call);
      }
    }

    // Finally, remove the old call from the program, reducing the use-count of
    // F.
    Call->eraseFromParent();
  }

  // Since we have now created the new function, splice the body of the old
  // function right into the new function, leaving the old rotting hulk of the
  // function empty.
  NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList());

  // Loop over the argument list, transferring uses of the old arguments over to
  // the new arguments, also transferring over the names as well.
  i = 0;
  for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(),
       I2 = NF->arg_begin(); I != E; ++I, ++i)
    if (ArgAlive[i]) {
      // If this is a live argument, move the name and users over to the new
      // version.
      I->replaceAllUsesWith(I2);
      I2->takeName(I);
      ++I2;
    } else {
      // If this argument is dead, replace any uses of it with null constants
      // (these are guaranteed to become unused later on).
      if (!I->getType()->isX86_MMXTy())
        I->replaceAllUsesWith(Constant::getNullValue(I->getType()));
    }

  // If we change the return value of the function we must rewrite any return
  // instructions.  Check this now.
  if (F->getReturnType() != NF->getReturnType())
    for (Function::iterator BB = NF->begin(), E = NF->end(); BB != E; ++BB)
      if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
        Value *RetVal;

        if (NFTy->getReturnType()->isVoidTy()) {
          RetVal = 0;
        } else {
          assert (RetTy->isStructTy());
          // The original return value was a struct, insert
          // extractvalue/insertvalue chains to extract only the values we need
          // to return and insert them into our new result.
          // This does generate messy code, but we'll let it to instcombine to
          // clean that up.
          Value *OldRet = RI->getOperand(0);
          // Start out building up our return value from undef
          RetVal = UndefValue::get(NRetTy);
          for (unsigned i = 0; i != RetCount; ++i)
            if (NewRetIdxs[i] != -1) {
              ExtractValueInst *EV = ExtractValueInst::Create(OldRet, i,
                                                              "oldret", RI);
              if (RetTypes.size() > 1) {
                // We're still returning a struct, so reinsert the value into
                // our new return value at the new index

                RetVal = InsertValueInst::Create(RetVal, EV, NewRetIdxs[i],
                                                 "newret", RI);
              } else {
                // We are now only returning a simple value, so just return the
                // extracted value.
                RetVal = EV;
              }
            }
        }
        // Replace the return instruction with one returning the new return
        // value (possibly 0 if we became void).
        ReturnInst::Create(F->getContext(), RetVal, RI);
        BB->getInstList().erase(RI);
      }

  // Patch the pointer to LLVM function in debug info descriptor.
  FunctionDIMap::iterator DI = FunctionDIs.find(F);
  if (DI != FunctionDIs.end())
    DI->second.replaceFunction(NF);

  // Now that the old function is dead, delete it.
  F->eraseFromParent();

  return true;
}
Exemplo n.º 9
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;
}
Exemplo n.º 10
0
/// HandleInlinedInvoke - If we inlined an invoke site, we need to convert calls
/// in the body of the inlined function into invokes and turn unwind
/// instructions into branches to the invoke unwind dest.
///
/// II is the invoke instruction being inlined.  FirstNewBlock is the first
/// block of the inlined code (the last block is the end of the function),
/// and InlineCodeInfo is information about the code that got inlined.
static void HandleInlinedInvoke(InvokeInst *II, BasicBlock *FirstNewBlock,
                                ClonedCodeInfo &InlinedCodeInfo) {
  BasicBlock *InvokeDest = II->getUnwindDest();
  std::vector<Value*> InvokeDestPHIValues;

  // If there are PHI nodes in the unwind destination block, we need to
  // keep track of which values came into them from this invoke, then remove
  // the entry for this block.
  BasicBlock *InvokeBlock = II->getParent();
  for (BasicBlock::iterator I = InvokeDest->begin(); isa<PHINode>(I); ++I) {
    PHINode *PN = cast<PHINode>(I);
    // Save the value to use for this edge.
    InvokeDestPHIValues.push_back(PN->getIncomingValueForBlock(InvokeBlock));
  }

  Function *Caller = FirstNewBlock->getParent();

  // The inlined code is currently at the end of the function, scan from the
  // start of the inlined code to its end, checking for stuff we need to
  // rewrite.
  if (InlinedCodeInfo.ContainsCalls || InlinedCodeInfo.ContainsUnwinds) {
    for (Function::iterator BB = FirstNewBlock, E = Caller->end();
         BB != E; ++BB) {
      if (InlinedCodeInfo.ContainsCalls) {
        for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ){
          Instruction *I = BBI++;

          // We only need to check for function calls: inlined invoke
          // instructions require no special handling.
          if (!isa<CallInst>(I)) continue;
          CallInst *CI = cast<CallInst>(I);

          // If this call cannot unwind, don't convert it to an invoke.
          if (CI->doesNotThrow())
            continue;

          // Convert this function call into an invoke instruction.
          // First, split the basic block.
          BasicBlock *Split = BB->splitBasicBlock(CI, CI->getName()+".noexc");

          // Next, create the new invoke instruction, inserting it at the end
          // of the old basic block.
          SmallVector<Value*, 8> InvokeArgs(CI->op_begin()+1, CI->op_end());
          InvokeInst *II =
            InvokeInst::Create(CI->getCalledValue(), Split, InvokeDest,
                               InvokeArgs.begin(), InvokeArgs.end(),
                               CI->getName(), BB->getTerminator());
          II->setCallingConv(CI->getCallingConv());
          II->setAttributes(CI->getAttributes());

          // Make sure that anything using the call now uses the invoke!
          CI->replaceAllUsesWith(II);

          // Delete the unconditional branch inserted by splitBasicBlock
          BB->getInstList().pop_back();
          Split->getInstList().pop_front();  // Delete the original call

          // Update any PHI nodes in the exceptional block to indicate that
          // there is now a new entry in them.
          unsigned i = 0;
          for (BasicBlock::iterator I = InvokeDest->begin();
               isa<PHINode>(I); ++I, ++i) {
            PHINode *PN = cast<PHINode>(I);
            PN->addIncoming(InvokeDestPHIValues[i], BB);
          }

          // This basic block is now complete, start scanning the next one.
          break;
        }
      }

      if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
        // An UnwindInst requires special handling when it gets inlined into an
        // invoke site.  Once this happens, we know that the unwind would cause
        // a control transfer to the invoke exception destination, so we can
        // transform it into a direct branch to the exception destination.
        BranchInst::Create(InvokeDest, UI);

        // Delete the unwind instruction!
        UI->eraseFromParent();

        // Update any PHI nodes in the exceptional block to indicate that
        // there is now a new entry in them.
        unsigned i = 0;
        for (BasicBlock::iterator I = InvokeDest->begin();
             isa<PHINode>(I); ++I, ++i) {
          PHINode *PN = cast<PHINode>(I);
          PN->addIncoming(InvokeDestPHIValues[i], BB);
        }
      }
    }
  }

  // Now that everything is happy, we have one final detail.  The PHI nodes in
  // the exception destination block still have entries due to the original
  // invoke instruction.  Eliminate these entries (which might even delete the
  // PHI node) now.
  InvokeDest->removePredecessor(II->getParent());
}
Exemplo n.º 11
0
// InlineFunction - This function inlines the called function into the basic
// block of the caller.  This returns false if it is not possible to inline this
// call.  The program is still in a well defined state if this occurs though.
//
// Note that this only does one level of inlining.  For example, if the
// instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now
// exists in the instruction stream.  Similiarly this will inline a recursive
// function by one level.
//
bool llvm::InlineFunction(CallSite CS, CallGraph *CG, const TargetData *TD) {
  Instruction *TheCall = CS.getInstruction();
  assert(TheCall->getParent() && TheCall->getParent()->getParent() &&
         "Instruction not in function!");

  const Function *CalledFunc = CS.getCalledFunction();
  if (CalledFunc == 0 ||          // Can't inline external function or indirect
      CalledFunc->isDeclaration() || // call, or call to a vararg function!
      CalledFunc->getFunctionType()->isVarArg()) return false;


  // If the call to the callee is not a tail call, we must clear the 'tail'
  // flags on any calls that we inline.
  bool MustClearTailCallFlags =
    !(isa<CallInst>(TheCall) && cast<CallInst>(TheCall)->isTailCall());

  // If the call to the callee cannot throw, set the 'nounwind' flag on any
  // calls that we inline.
  bool MarkNoUnwind = CS.doesNotThrow();

  BasicBlock *OrigBB = TheCall->getParent();
  Function *Caller = OrigBB->getParent();

  // GC poses two hazards to inlining, which only occur when the callee has GC:
  //  1. If the caller has no GC, then the callee's GC must be propagated to the
  //     caller.
  //  2. If the caller has a differing GC, it is invalid to inline.
  if (CalledFunc->hasGC()) {
    if (!Caller->hasGC())
      Caller->setGC(CalledFunc->getGC());
    else if (CalledFunc->getGC() != Caller->getGC())
      return false;
  }

  // Get an iterator to the last basic block in the function, which will have
  // the new function inlined after it.
  //
  Function::iterator LastBlock = &Caller->back();

  // Make sure to capture all of the return instructions from the cloned
  // function.
  std::vector<ReturnInst*> Returns;
  ClonedCodeInfo InlinedFunctionInfo;
  Function::iterator FirstNewBlock;

  { // Scope to destroy ValueMap after cloning.
    DenseMap<const Value*, Value*> ValueMap;

    assert(CalledFunc->arg_size() == CS.arg_size() &&
           "No varargs calls can be inlined!");

    // Calculate the vector of arguments to pass into the function cloner, which
    // matches up the formal to the actual argument values.
    CallSite::arg_iterator AI = CS.arg_begin();
    unsigned ArgNo = 0;
    for (Function::const_arg_iterator I = CalledFunc->arg_begin(),
         E = CalledFunc->arg_end(); I != E; ++I, ++AI, ++ArgNo) {
      Value *ActualArg = *AI;

      // When byval arguments actually inlined, we need to make the copy implied
      // by them explicit.  However, we don't do this if the callee is readonly
      // or readnone, because the copy would be unneeded: the callee doesn't
      // modify the struct.
      if (CalledFunc->paramHasAttr(ArgNo+1, Attribute::ByVal) &&
          !CalledFunc->onlyReadsMemory()) {
        const Type *AggTy = cast<PointerType>(I->getType())->getElementType();
        const Type *VoidPtrTy = PointerType::getUnqual(Type::Int8Ty);

        // Create the alloca.  If we have TargetData, use nice alignment.
        unsigned Align = 1;
        if (TD) Align = TD->getPrefTypeAlignment(AggTy);
        Value *NewAlloca = new AllocaInst(AggTy, 0, Align, I->getName(),
                                          Caller->begin()->begin());
        // Emit a memcpy.
        const Type *Tys[] = { Type::Int64Ty };
        Function *MemCpyFn = Intrinsic::getDeclaration(Caller->getParent(),
                                                       Intrinsic::memcpy, 
                                                       Tys, 1);
        Value *DestCast = new BitCastInst(NewAlloca, VoidPtrTy, "tmp", TheCall);
        Value *SrcCast = new BitCastInst(*AI, VoidPtrTy, "tmp", TheCall);

        Value *Size;
        if (TD == 0)
          Size = ConstantExpr::getSizeOf(AggTy);
        else
          Size = ConstantInt::get(Type::Int64Ty, TD->getTypeStoreSize(AggTy));

        // Always generate a memcpy of alignment 1 here because we don't know
        // the alignment of the src pointer.  Other optimizations can infer
        // better alignment.
        Value *CallArgs[] = {
          DestCast, SrcCast, Size, ConstantInt::get(Type::Int32Ty, 1)
        };
        CallInst *TheMemCpy =
          CallInst::Create(MemCpyFn, CallArgs, CallArgs+4, "", TheCall);

        // If we have a call graph, update it.
        if (CG) {
          CallGraphNode *MemCpyCGN = CG->getOrInsertFunction(MemCpyFn);
          CallGraphNode *CallerNode = (*CG)[Caller];
          CallerNode->addCalledFunction(TheMemCpy, MemCpyCGN);
        }

        // Uses of the argument in the function should use our new alloca
        // instead.
        ActualArg = NewAlloca;
      }

      ValueMap[I] = ActualArg;
    }

    // We want the inliner to prune the code as it copies.  We would LOVE to
    // have no dead or constant instructions leftover after inlining occurs
    // (which can happen, e.g., because an argument was constant), but we'll be
    // happy with whatever the cloner can do.
    CloneAndPruneFunctionInto(Caller, CalledFunc, ValueMap, Returns, ".i",
                              &InlinedFunctionInfo, TD);

    // Remember the first block that is newly cloned over.
    FirstNewBlock = LastBlock; ++FirstNewBlock;

    // Update the callgraph if requested.
    if (CG)
      UpdateCallGraphAfterInlining(CS, FirstNewBlock, ValueMap, *CG);
  }

  // If there are any alloca instructions in the block that used to be the entry
  // block for the callee, move them to the entry block of the caller.  First
  // calculate which instruction they should be inserted before.  We insert the
  // instructions at the end of the current alloca list.
  //
  {
    BasicBlock::iterator InsertPoint = Caller->begin()->begin();
    for (BasicBlock::iterator I = FirstNewBlock->begin(),
           E = FirstNewBlock->end(); I != E; )
      if (AllocaInst *AI = dyn_cast<AllocaInst>(I++)) {
        // If the alloca is now dead, remove it.  This often occurs due to code
        // specialization.
        if (AI->use_empty()) {
          AI->eraseFromParent();
          continue;
        }

        if (isa<Constant>(AI->getArraySize())) {
          // Scan for the block of allocas that we can move over, and move them
          // all at once.
          while (isa<AllocaInst>(I) &&
                 isa<Constant>(cast<AllocaInst>(I)->getArraySize()))
            ++I;

          // Transfer all of the allocas over in a block.  Using splice means
          // that the instructions aren't removed from the symbol table, then
          // reinserted.
          Caller->getEntryBlock().getInstList().splice(
              InsertPoint,
              FirstNewBlock->getInstList(),
              AI, I);
        }
      }
  }

  // If the inlined code contained dynamic alloca instructions, wrap the inlined
  // code with llvm.stacksave/llvm.stackrestore intrinsics.
  if (InlinedFunctionInfo.ContainsDynamicAllocas) {
    Module *M = Caller->getParent();
    // Get the two intrinsics we care about.
    Constant *StackSave, *StackRestore;
    StackSave    = Intrinsic::getDeclaration(M, Intrinsic::stacksave);
    StackRestore = Intrinsic::getDeclaration(M, Intrinsic::stackrestore);

    // If we are preserving the callgraph, add edges to the stacksave/restore
    // functions for the calls we insert.
    CallGraphNode *StackSaveCGN = 0, *StackRestoreCGN = 0, *CallerNode = 0;
    if (CG) {
      // We know that StackSave/StackRestore are Function*'s, because they are
      // intrinsics which must have the right types.
      StackSaveCGN    = CG->getOrInsertFunction(cast<Function>(StackSave));
      StackRestoreCGN = CG->getOrInsertFunction(cast<Function>(StackRestore));
      CallerNode = (*CG)[Caller];
    }

    // Insert the llvm.stacksave.
    CallInst *SavedPtr = CallInst::Create(StackSave, "savedstack",
                                          FirstNewBlock->begin());
    if (CG) CallerNode->addCalledFunction(SavedPtr, StackSaveCGN);

    // Insert a call to llvm.stackrestore before any return instructions in the
    // inlined function.
    for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
      CallInst *CI = CallInst::Create(StackRestore, SavedPtr, "", Returns[i]);
      if (CG) CallerNode->addCalledFunction(CI, StackRestoreCGN);
    }

    // Count the number of StackRestore calls we insert.
    unsigned NumStackRestores = Returns.size();

    // If we are inlining an invoke instruction, insert restores before each
    // unwind.  These unwinds will be rewritten into branches later.
    if (InlinedFunctionInfo.ContainsUnwinds && isa<InvokeInst>(TheCall)) {
      for (Function::iterator BB = FirstNewBlock, E = Caller->end();
           BB != E; ++BB)
        if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
          CallInst::Create(StackRestore, SavedPtr, "", UI);
          ++NumStackRestores;
        }
    }
  }

  // If we are inlining tail call instruction through a call site that isn't
  // marked 'tail', we must remove the tail marker for any calls in the inlined
  // code.  Also, calls inlined through a 'nounwind' call site should be marked
  // 'nounwind'.
  if (InlinedFunctionInfo.ContainsCalls &&
      (MustClearTailCallFlags || MarkNoUnwind)) {
    for (Function::iterator BB = FirstNewBlock, E = Caller->end();
         BB != E; ++BB)
      for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
        if (CallInst *CI = dyn_cast<CallInst>(I)) {
          if (MustClearTailCallFlags)
            CI->setTailCall(false);
          if (MarkNoUnwind)
            CI->setDoesNotThrow();
        }
  }

  // If we are inlining through a 'nounwind' call site then any inlined 'unwind'
  // instructions are unreachable.
  if (InlinedFunctionInfo.ContainsUnwinds && MarkNoUnwind)
    for (Function::iterator BB = FirstNewBlock, E = Caller->end();
         BB != E; ++BB) {
      TerminatorInst *Term = BB->getTerminator();
      if (isa<UnwindInst>(Term)) {
        new UnreachableInst(Term);
        BB->getInstList().erase(Term);
      }
    }

  // If we are inlining for an invoke instruction, we must make sure to rewrite
  // any inlined 'unwind' instructions into branches to the invoke exception
  // destination, and call instructions into invoke instructions.
  if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall))
    HandleInlinedInvoke(II, FirstNewBlock, InlinedFunctionInfo);

  // If we cloned in _exactly one_ basic block, and if that block ends in a
  // return instruction, we splice the body of the inlined callee directly into
  // the calling basic block.
  if (Returns.size() == 1 && std::distance(FirstNewBlock, Caller->end()) == 1) {
    // Move all of the instructions right before the call.
    OrigBB->getInstList().splice(TheCall, FirstNewBlock->getInstList(),
                                 FirstNewBlock->begin(), FirstNewBlock->end());
    // Remove the cloned basic block.
    Caller->getBasicBlockList().pop_back();

    // If the call site was an invoke instruction, add a branch to the normal
    // destination.
    if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall))
      BranchInst::Create(II->getNormalDest(), TheCall);

    // If the return instruction returned a value, replace uses of the call with
    // uses of the returned value.
    if (!TheCall->use_empty()) {
      ReturnInst *R = Returns[0];
      TheCall->replaceAllUsesWith(R->getReturnValue());
    }
    // Since we are now done with the Call/Invoke, we can delete it.
    TheCall->eraseFromParent();

    // Since we are now done with the return instruction, delete it also.
    Returns[0]->eraseFromParent();

    // We are now done with the inlining.
    return true;
  }

  // Otherwise, we have the normal case, of more than one block to inline or
  // multiple return sites.

  // We want to clone the entire callee function into the hole between the
  // "starter" and "ender" blocks.  How we accomplish this depends on whether
  // this is an invoke instruction or a call instruction.
  BasicBlock *AfterCallBB;
  if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) {

    // Add an unconditional branch to make this look like the CallInst case...
    BranchInst *NewBr = BranchInst::Create(II->getNormalDest(), TheCall);

    // Split the basic block.  This guarantees that no PHI nodes will have to be
    // updated due to new incoming edges, and make the invoke case more
    // symmetric to the call case.
    AfterCallBB = OrigBB->splitBasicBlock(NewBr,
                                          CalledFunc->getName()+".exit");

  } else {  // It's a call
    // If this is a call instruction, we need to split the basic block that
    // the call lives in.
    //
    AfterCallBB = OrigBB->splitBasicBlock(TheCall,
                                          CalledFunc->getName()+".exit");
  }

  // Change the branch that used to go to AfterCallBB to branch to the first
  // basic block of the inlined function.
  //
  TerminatorInst *Br = OrigBB->getTerminator();
  assert(Br && Br->getOpcode() == Instruction::Br &&
         "splitBasicBlock broken!");
  Br->setOperand(0, FirstNewBlock);


  // Now that the function is correct, make it a little bit nicer.  In
  // particular, move the basic blocks inserted from the end of the function
  // into the space made by splitting the source basic block.
  Caller->getBasicBlockList().splice(AfterCallBB, Caller->getBasicBlockList(),
                                     FirstNewBlock, Caller->end());

  // Handle all of the return instructions that we just cloned in, and eliminate
  // any users of the original call/invoke instruction.
  const Type *RTy = CalledFunc->getReturnType();

  if (Returns.size() > 1) {
    // The PHI node should go at the front of the new basic block to merge all
    // possible incoming values.
    PHINode *PHI = 0;
    if (!TheCall->use_empty()) {
      PHI = PHINode::Create(RTy, TheCall->getName(),
                            AfterCallBB->begin());
      // Anything that used the result of the function call should now use the
      // PHI node as their operand.
      TheCall->replaceAllUsesWith(PHI);
    }

    // Loop over all of the return instructions adding entries to the PHI node
    // as appropriate.
    if (PHI) {
      for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
        ReturnInst *RI = Returns[i];
        assert(RI->getReturnValue()->getType() == PHI->getType() &&
               "Ret value not consistent in function!");
        PHI->addIncoming(RI->getReturnValue(), RI->getParent());
      }
    }

    // Add a branch to the merge points and remove return instructions.
    for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
      ReturnInst *RI = Returns[i];
      BranchInst::Create(AfterCallBB, RI);
      RI->eraseFromParent();
    }
  } else if (!Returns.empty()) {
    // Otherwise, if there is exactly one return value, just replace anything
    // using the return value of the call with the computed value.
    if (!TheCall->use_empty())
      TheCall->replaceAllUsesWith(Returns[0]->getReturnValue());

    // Splice the code from the return block into the block that it will return
    // to, which contains the code that was after the call.
    BasicBlock *ReturnBB = Returns[0]->getParent();
    AfterCallBB->getInstList().splice(AfterCallBB->begin(),
                                      ReturnBB->getInstList());

    // Update PHI nodes that use the ReturnBB to use the AfterCallBB.
    ReturnBB->replaceAllUsesWith(AfterCallBB);

    // Delete the return instruction now and empty ReturnBB now.
    Returns[0]->eraseFromParent();
    ReturnBB->eraseFromParent();
  } else if (!TheCall->use_empty()) {
    // No returns, but something is using the return value of the call.  Just
    // nuke the result.
    TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType()));
  }

  // Since we are now done with the Call/Invoke, we can delete it.
  TheCall->eraseFromParent();

  // We should always be able to fold the entry block of the function into the
  // single predecessor of the block...
  assert(cast<BranchInst>(Br)->isUnconditional() && "splitBasicBlock broken!");
  BasicBlock *CalleeEntry = cast<BranchInst>(Br)->getSuccessor(0);

  // Splice the code entry block into calling block, right before the
  // unconditional branch.
  OrigBB->getInstList().splice(Br, CalleeEntry->getInstList());
  CalleeEntry->replaceAllUsesWith(OrigBB);  // Update PHI nodes

  // Remove the unconditional branch.
  OrigBB->getInstList().erase(Br);

  // Now we can remove the CalleeEntry block, which is now empty.
  Caller->getBasicBlockList().erase(CalleeEntry);

  return true;
}
Exemplo n.º 12
0
/// This works like CloneAndPruneFunctionInto, except that it does not clone the
/// entire function. Instead it starts at an instruction provided by the caller
/// and copies (and prunes) only the code reachable from that instruction.
void llvm::CloneAndPruneIntoFromInst(Function *NewFunc, const Function *OldFunc,
                                     const Instruction *StartingInst,
                                     ValueToValueMapTy &VMap,
                                     bool ModuleLevelChanges,
                                     SmallVectorImpl<ReturnInst *> &Returns,
                                     const char *NameSuffix,
                                     ClonedCodeInfo *CodeInfo) {
  assert(NameSuffix && "NameSuffix cannot be null!");

  ValueMapTypeRemapper *TypeMapper = nullptr;
  ValueMaterializer *Materializer = nullptr;

#ifndef NDEBUG
  // If the cloning starts at the beginning of the function, verify that
  // the function arguments are mapped.
  if (!StartingInst)
    for (const Argument &II : OldFunc->args())
      assert(VMap.count(&II) && "No mapping from source argument specified!");
#endif

  PruningFunctionCloner PFC(NewFunc, OldFunc, VMap, ModuleLevelChanges,
                            NameSuffix, CodeInfo);
  const BasicBlock *StartingBB;
  if (StartingInst)
    StartingBB = StartingInst->getParent();
  else {
    StartingBB = &OldFunc->getEntryBlock();
    StartingInst = &StartingBB->front();
  }

  // Clone the entry block, and anything recursively reachable from it.
  std::vector<const BasicBlock*> CloneWorklist;
  PFC.CloneBlock(StartingBB, StartingInst->getIterator(), CloneWorklist);
  while (!CloneWorklist.empty()) {
    const BasicBlock *BB = CloneWorklist.back();
    CloneWorklist.pop_back();
    PFC.CloneBlock(BB, BB->begin(), CloneWorklist);
  }
  
  // Loop over all of the basic blocks in the old function.  If the block was
  // reachable, we have cloned it and the old block is now in the value map:
  // insert it into the new function in the right order.  If not, ignore it.
  //
  // Defer PHI resolution until rest of function is resolved.
  SmallVector<const PHINode*, 16> PHIToResolve;
  for (const BasicBlock &BI : *OldFunc) {
    Value *V = VMap[&BI];
    BasicBlock *NewBB = cast_or_null<BasicBlock>(V);
    if (!NewBB) continue;  // Dead block.

    // Add the new block to the new function.
    NewFunc->getBasicBlockList().push_back(NewBB);

    // Handle PHI nodes specially, as we have to remove references to dead
    // blocks.
    for (BasicBlock::const_iterator I = BI.begin(), E = BI.end(); I != E; ++I) {
      // PHI nodes may have been remapped to non-PHI nodes by the caller or
      // during the cloning process.
      if (const PHINode *PN = dyn_cast<PHINode>(I)) {
        if (isa<PHINode>(VMap[PN]))
          PHIToResolve.push_back(PN);
        else
          break;
      } else {
        break;
      }
    }

    // Finally, remap the terminator instructions, as those can't be remapped
    // until all BBs are mapped.
    RemapInstruction(NewBB->getTerminator(), VMap,
                     ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges,
                     TypeMapper, Materializer);
  }
  
  // Defer PHI resolution until rest of function is resolved, PHI resolution
  // requires the CFG to be up-to-date.
  for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) {
    const PHINode *OPN = PHIToResolve[phino];
    unsigned NumPreds = OPN->getNumIncomingValues();
    const BasicBlock *OldBB = OPN->getParent();
    BasicBlock *NewBB = cast<BasicBlock>(VMap[OldBB]);

    // Map operands for blocks that are live and remove operands for blocks
    // that are dead.
    for (; phino != PHIToResolve.size() &&
         PHIToResolve[phino]->getParent() == OldBB; ++phino) {
      OPN = PHIToResolve[phino];
      PHINode *PN = cast<PHINode>(VMap[OPN]);
      for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) {
        Value *V = VMap[PN->getIncomingBlock(pred)];
        if (BasicBlock *MappedBlock = cast_or_null<BasicBlock>(V)) {
          Value *InVal = MapValue(PN->getIncomingValue(pred),
                                  VMap, 
                        ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges);
          assert(InVal && "Unknown input value?");
          PN->setIncomingValue(pred, InVal);
          PN->setIncomingBlock(pred, MappedBlock);
        } else {
          PN->removeIncomingValue(pred, false);
          --pred, --e;  // Revisit the next entry.
        }
      } 
    }
    
    // The loop above has removed PHI entries for those blocks that are dead
    // and has updated others.  However, if a block is live (i.e. copied over)
    // but its terminator has been changed to not go to this block, then our
    // phi nodes will have invalid entries.  Update the PHI nodes in this
    // case.
    PHINode *PN = cast<PHINode>(NewBB->begin());
    NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB));
    if (NumPreds != PN->getNumIncomingValues()) {
      assert(NumPreds < PN->getNumIncomingValues());
      // Count how many times each predecessor comes to this block.
      std::map<BasicBlock*, unsigned> PredCount;
      for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB);
           PI != E; ++PI)
        --PredCount[*PI];
      
      // Figure out how many entries to remove from each PHI.
      for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
        ++PredCount[PN->getIncomingBlock(i)];
      
      // At this point, the excess predecessor entries are positive in the
      // map.  Loop over all of the PHIs and remove excess predecessor
      // entries.
      BasicBlock::iterator I = NewBB->begin();
      for (; (PN = dyn_cast<PHINode>(I)); ++I) {
        for (std::map<BasicBlock*, unsigned>::iterator PCI =PredCount.begin(),
             E = PredCount.end(); PCI != E; ++PCI) {
          BasicBlock *Pred     = PCI->first;
          for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove)
            PN->removeIncomingValue(Pred, false);
        }
      }
    }
    
    // If the loops above have made these phi nodes have 0 or 1 operand,
    // replace them with undef or the input value.  We must do this for
    // correctness, because 0-operand phis are not valid.
    PN = cast<PHINode>(NewBB->begin());
    if (PN->getNumIncomingValues() == 0) {
      BasicBlock::iterator I = NewBB->begin();
      BasicBlock::const_iterator OldI = OldBB->begin();
      while ((PN = dyn_cast<PHINode>(I++))) {
        Value *NV = UndefValue::get(PN->getType());
        PN->replaceAllUsesWith(NV);
        assert(VMap[&*OldI] == PN && "VMap mismatch");
        VMap[&*OldI] = NV;
        PN->eraseFromParent();
        ++OldI;
      }
    }
  }

  // Make a second pass over the PHINodes now that all of them have been
  // remapped into the new function, simplifying the PHINode and performing any
  // recursive simplifications exposed. This will transparently update the
  // WeakVH in the VMap. Notably, we rely on that so that if we coalesce
  // two PHINodes, the iteration over the old PHIs remains valid, and the
  // mapping will just map us to the new node (which may not even be a PHI
  // node).
  for (unsigned Idx = 0, Size = PHIToResolve.size(); Idx != Size; ++Idx)
    if (PHINode *PN = dyn_cast<PHINode>(VMap[PHIToResolve[Idx]]))
      recursivelySimplifyInstruction(PN);

  // Now that the inlined function body has been fully constructed, go through
  // and zap unconditional fall-through branches. This happens all the time when
  // specializing code: code specialization turns conditional branches into
  // uncond branches, and this code folds them.
  Function::iterator Begin = cast<BasicBlock>(VMap[StartingBB])->getIterator();
  Function::iterator I = Begin;
  while (I != NewFunc->end()) {
    // Check if this block has become dead during inlining or other
    // simplifications. Note that the first block will appear dead, as it has
    // not yet been wired up properly.
    if (I != Begin && (pred_begin(&*I) == pred_end(&*I) ||
                       I->getSinglePredecessor() == &*I)) {
      BasicBlock *DeadBB = &*I++;
      DeleteDeadBlock(DeadBB);
      continue;
    }

    // We need to simplify conditional branches and switches with a constant
    // operand. We try to prune these out when cloning, but if the
    // simplification required looking through PHI nodes, those are only
    // available after forming the full basic block. That may leave some here,
    // and we still want to prune the dead code as early as possible.
    ConstantFoldTerminator(&*I);

    BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator());
    if (!BI || BI->isConditional()) { ++I; continue; }
    
    BasicBlock *Dest = BI->getSuccessor(0);
    if (!Dest->getSinglePredecessor()) {
      ++I; continue;
    }

    // We shouldn't be able to get single-entry PHI nodes here, as instsimplify
    // above should have zapped all of them..
    assert(!isa<PHINode>(Dest->begin()));

    // We know all single-entry PHI nodes in the inlined function have been
    // removed, so we just need to splice the blocks.
    BI->eraseFromParent();
    
    // Make all PHI nodes that referred to Dest now refer to I as their source.
    Dest->replaceAllUsesWith(&*I);

    // Move all the instructions in the succ to the pred.
    I->getInstList().splice(I->end(), Dest->getInstList());
    
    // Remove the dest block.
    Dest->eraseFromParent();
    
    // Do not increment I, iteratively merge all things this block branches to.
  }

  // Make a final pass over the basic blocks from the old function to gather
  // any return instructions which survived folding. We have to do this here
  // because we can iteratively remove and merge returns above.
  for (Function::iterator I = cast<BasicBlock>(VMap[StartingBB])->getIterator(),
                          E = NewFunc->end();
       I != E; ++I)
    if (ReturnInst *RI = dyn_cast<ReturnInst>(I->getTerminator()))
      Returns.push_back(RI);
}
Exemplo n.º 13
0
bool ReduceCrashingBlocks::TestBlocks(std::vector<const BasicBlock*> &BBs) {
  // Clone the program to try hacking it apart...
  DenseMap<const Value*, Value*> ValueMap;
  Module *M = CloneModule(BD.getProgram(), ValueMap);

  // 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>(ValueMap[BBs[i]]));

  std::cout << "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)
    std::cout << " " << BBs[i]->getName();
  if (NumPrint < Blocks.size())
    std::cout << "... <" << Blocks.size() << " total>";
  std::cout << ": ";

  // 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 (isa<StructType>(BBTerm->getType()))
           BBTerm->replaceAllUsesWith(UndefValue::get(BBTerm->getType()));
        else if (BB->getTerminator()->getType() != Type::VoidTy)
          BBTerm->replaceAllUsesWith(Constant::getNullValue(BBTerm->getType()));

        // Replace the old terminator instruction.
        BB->getInstList().pop_back();
        new UnreachableInst(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<Function*, std::string> > BlockInfo;

  for (SmallPtrSet<BasicBlock*, 8>::iterator I = Blocks.begin(),
         E = Blocks.end(); I != E; ++I)
    BlockInfo.push_back(std::make_pair((*I)->getParent(), (*I)->getName()));

  // Now run the CFG simplify pass on the function...
  PassManager Passes;
  Passes.add(createCFGSimplificationPass());
  Passes.add(createVerifierPass());
  Passes.run(*M);

  // 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();
    for (unsigned i = 0, e = BlockInfo.size(); i != e; ++i) {
      ValueSymbolTable &ST = BlockInfo[i].first->getValueSymbolTable();
      Value* V = ST.lookup(BlockInfo[i].second);
      if (V && V->getType() == Type::LabelTy)
        BBs.push_back(cast<BasicBlock>(V));
    }
    return true;
  }
  delete M;  // It didn't crash, try something else.
  return false;
}
Exemplo n.º 14
0
/// InlineFunction - This function inlines the called function into the basic
/// block of the caller.  This returns false if it is not possible to inline
/// this call.  The program is still in a well defined state if this occurs
/// though.
///
/// Note that this only does one level of inlining.  For example, if the
/// instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now
/// exists in the instruction stream.  Similarly this will inline a recursive
/// function by one level.
bool llvm::InlineFunction(CallSite CS, InlineFunctionInfo &IFI,
                          bool InsertLifetime) {
  Instruction *TheCall = CS.getInstruction();
  assert(TheCall->getParent() && TheCall->getParent()->getParent() &&
         "Instruction not in function!");

  // If IFI has any state in it, zap it before we fill it in.
  IFI.reset();
  
  const Function *CalledFunc = CS.getCalledFunction();
  if (CalledFunc == 0 ||          // Can't inline external function or indirect
      CalledFunc->isDeclaration() || // call, or call to a vararg function!
      CalledFunc->getFunctionType()->isVarArg()) return false;

  // If the call to the callee is not a tail call, we must clear the 'tail'
  // flags on any calls that we inline.
  bool MustClearTailCallFlags =
    !(isa<CallInst>(TheCall) && cast<CallInst>(TheCall)->isTailCall());

  // If the call to the callee cannot throw, set the 'nounwind' flag on any
  // calls that we inline.
  bool MarkNoUnwind = CS.doesNotThrow();

  BasicBlock *OrigBB = TheCall->getParent();
  Function *Caller = OrigBB->getParent();

  // GC poses two hazards to inlining, which only occur when the callee has GC:
  //  1. If the caller has no GC, then the callee's GC must be propagated to the
  //     caller.
  //  2. If the caller has a differing GC, it is invalid to inline.
  if (CalledFunc->hasGC()) {
    if (!Caller->hasGC())
      Caller->setGC(CalledFunc->getGC());
    else if (CalledFunc->getGC() != Caller->getGC())
      return false;
  }

  // Get the personality function from the callee if it contains a landing pad.
  Value *CalleePersonality = 0;
  for (Function::const_iterator I = CalledFunc->begin(), E = CalledFunc->end();
       I != E; ++I)
    if (const InvokeInst *II = dyn_cast<InvokeInst>(I->getTerminator())) {
      const BasicBlock *BB = II->getUnwindDest();
      const LandingPadInst *LP = BB->getLandingPadInst();
      CalleePersonality = LP->getPersonalityFn();
      break;
    }

  // Find the personality function used by the landing pads of the caller. If it
  // exists, then check to see that it matches the personality function used in
  // the callee.
  if (CalleePersonality) {
    for (Function::const_iterator I = Caller->begin(), E = Caller->end();
         I != E; ++I)
      if (const InvokeInst *II = dyn_cast<InvokeInst>(I->getTerminator())) {
        const BasicBlock *BB = II->getUnwindDest();
        const LandingPadInst *LP = BB->getLandingPadInst();

        // If the personality functions match, then we can perform the
        // inlining. Otherwise, we can't inline.
        // TODO: This isn't 100% true. Some personality functions are proper
        //       supersets of others and can be used in place of the other.
        if (LP->getPersonalityFn() != CalleePersonality)
          return false;

        break;
      }
  }

  // Get an iterator to the last basic block in the function, which will have
  // the new function inlined after it.
  Function::iterator LastBlock = &Caller->back();

  // Make sure to capture all of the return instructions from the cloned
  // function.
  SmallVector<ReturnInst*, 8> Returns;
  ClonedCodeInfo InlinedFunctionInfo;
  Function::iterator FirstNewBlock;

  { // Scope to destroy VMap after cloning.
    ValueToValueMapTy VMap;

    assert(CalledFunc->arg_size() == CS.arg_size() &&
           "No varargs calls can be inlined!");

    // Calculate the vector of arguments to pass into the function cloner, which
    // matches up the formal to the actual argument values.
    CallSite::arg_iterator AI = CS.arg_begin();
    unsigned ArgNo = 0;
    for (Function::const_arg_iterator I = CalledFunc->arg_begin(),
         E = CalledFunc->arg_end(); I != E; ++I, ++AI, ++ArgNo) {
      Value *ActualArg = *AI;
      const Argument *Arg = I;

      // When byval arguments actually inlined, we need to make the copy implied
      // by them explicit.  However, we don't do this if the callee is readonly
      // or readnone, because the copy would be unneeded: the callee doesn't
      // modify the struct.
      if (CS.isByValArgument(ArgNo)) {
        ActualArg = HandleByValArgument(ActualArg, Arg, TheCall, CalledFunc, IFI,
                                        CalledFunc->getParamAlignment(ArgNo+1));
 
        // Calls that we inline may use the new alloca, so we need to clear
        // their 'tail' flags if HandleByValArgument introduced a new alloca and
        // the callee has calls.
        MustClearTailCallFlags |= ActualArg != *AI;
      }

      VMap[I] = ActualArg;
    }

    // We want the inliner to prune the code as it copies.  We would LOVE to
    // have no dead or constant instructions leftover after inlining occurs
    // (which can happen, e.g., because an argument was constant), but we'll be
    // happy with whatever the cloner can do.
    CloneAndPruneFunctionInto(Caller, CalledFunc, VMap, 
                              /*ModuleLevelChanges=*/false, Returns, ".i",
                              &InlinedFunctionInfo, IFI.TD, TheCall);

    // Remember the first block that is newly cloned over.
    FirstNewBlock = LastBlock; ++FirstNewBlock;

    // Update the callgraph if requested.
    if (IFI.CG)
      UpdateCallGraphAfterInlining(CS, FirstNewBlock, VMap, IFI);

    // Update inlined instructions' line number information.
    fixupLineNumbers(Caller, FirstNewBlock, TheCall);
  }

  // If there are any alloca instructions in the block that used to be the entry
  // block for the callee, move them to the entry block of the caller.  First
  // calculate which instruction they should be inserted before.  We insert the
  // instructions at the end of the current alloca list.
  {
    BasicBlock::iterator InsertPoint = Caller->begin()->begin();
    for (BasicBlock::iterator I = FirstNewBlock->begin(),
         E = FirstNewBlock->end(); I != E; ) {
      AllocaInst *AI = dyn_cast<AllocaInst>(I++);
      if (AI == 0) continue;
      
      // If the alloca is now dead, remove it.  This often occurs due to code
      // specialization.
      if (AI->use_empty()) {
        AI->eraseFromParent();
        continue;
      }

      if (!isa<Constant>(AI->getArraySize()))
        continue;
      
      // Keep track of the static allocas that we inline into the caller.
      IFI.StaticAllocas.push_back(AI);
      
      // Scan for the block of allocas that we can move over, and move them
      // all at once.
      while (isa<AllocaInst>(I) &&
             isa<Constant>(cast<AllocaInst>(I)->getArraySize())) {
        IFI.StaticAllocas.push_back(cast<AllocaInst>(I));
        ++I;
      }

      // Transfer all of the allocas over in a block.  Using splice means
      // that the instructions aren't removed from the symbol table, then
      // reinserted.
      Caller->getEntryBlock().getInstList().splice(InsertPoint,
                                                   FirstNewBlock->getInstList(),
                                                   AI, I);
    }
  }

  // Leave lifetime markers for the static alloca's, scoping them to the
  // function we just inlined.
  if (InsertLifetime && !IFI.StaticAllocas.empty()) {
    IRBuilder<> builder(FirstNewBlock->begin());
    for (unsigned ai = 0, ae = IFI.StaticAllocas.size(); ai != ae; ++ai) {
      AllocaInst *AI = IFI.StaticAllocas[ai];

      // If the alloca is already scoped to something smaller than the whole
      // function then there's no need to add redundant, less accurate markers.
      if (hasLifetimeMarkers(AI))
        continue;

      // Try to determine the size of the allocation.
      ConstantInt *AllocaSize = 0;
      if (ConstantInt *AIArraySize =
          dyn_cast<ConstantInt>(AI->getArraySize())) {
        if (IFI.TD) {
          Type *AllocaType = AI->getAllocatedType();
          uint64_t AllocaTypeSize = IFI.TD->getTypeAllocSize(AllocaType);
          uint64_t AllocaArraySize = AIArraySize->getLimitedValue();
          assert(AllocaArraySize > 0 && "array size of AllocaInst is zero");
          // Check that array size doesn't saturate uint64_t and doesn't
          // overflow when it's multiplied by type size.
          if (AllocaArraySize != ~0ULL &&
              UINT64_MAX / AllocaArraySize >= AllocaTypeSize) {
            AllocaSize = ConstantInt::get(Type::getInt64Ty(AI->getContext()),
                                          AllocaArraySize * AllocaTypeSize);
          }
        }
      }

      builder.CreateLifetimeStart(AI, AllocaSize);
      for (unsigned ri = 0, re = Returns.size(); ri != re; ++ri) {
        IRBuilder<> builder(Returns[ri]);
        builder.CreateLifetimeEnd(AI, AllocaSize);
      }
    }
  }

  // If the inlined code contained dynamic alloca instructions, wrap the inlined
  // code with llvm.stacksave/llvm.stackrestore intrinsics.
  if (InlinedFunctionInfo.ContainsDynamicAllocas) {
    Module *M = Caller->getParent();
    // Get the two intrinsics we care about.
    Function *StackSave = Intrinsic::getDeclaration(M, Intrinsic::stacksave);
    Function *StackRestore=Intrinsic::getDeclaration(M,Intrinsic::stackrestore);

    // Insert the llvm.stacksave.
    CallInst *SavedPtr = IRBuilder<>(FirstNewBlock, FirstNewBlock->begin())
      .CreateCall(StackSave, "savedstack");

    // Insert a call to llvm.stackrestore before any return instructions in the
    // inlined function.
    for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
      IRBuilder<>(Returns[i]).CreateCall(StackRestore, SavedPtr);
    }
  }

  // If we are inlining tail call instruction through a call site that isn't
  // marked 'tail', we must remove the tail marker for any calls in the inlined
  // code.  Also, calls inlined through a 'nounwind' call site should be marked
  // 'nounwind'.
  if (InlinedFunctionInfo.ContainsCalls &&
      (MustClearTailCallFlags || MarkNoUnwind)) {
    for (Function::iterator BB = FirstNewBlock, E = Caller->end();
         BB != E; ++BB)
      for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
        if (CallInst *CI = dyn_cast<CallInst>(I)) {
          if (MustClearTailCallFlags)
            CI->setTailCall(false);
          if (MarkNoUnwind)
            CI->setDoesNotThrow();
        }
  }

  // If we are inlining for an invoke instruction, we must make sure to rewrite
  // any call instructions into invoke instructions.
  if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall))
    HandleInlinedInvoke(II, FirstNewBlock, InlinedFunctionInfo);

  // If we cloned in _exactly one_ basic block, and if that block ends in a
  // return instruction, we splice the body of the inlined callee directly into
  // the calling basic block.
  if (Returns.size() == 1 && std::distance(FirstNewBlock, Caller->end()) == 1) {
    // Move all of the instructions right before the call.
    OrigBB->getInstList().splice(TheCall, FirstNewBlock->getInstList(),
                                 FirstNewBlock->begin(), FirstNewBlock->end());
    // Remove the cloned basic block.
    Caller->getBasicBlockList().pop_back();

    // If the call site was an invoke instruction, add a branch to the normal
    // destination.
    if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) {
      BranchInst *NewBr = BranchInst::Create(II->getNormalDest(), TheCall);
      NewBr->setDebugLoc(Returns[0]->getDebugLoc());
    }

    // If the return instruction returned a value, replace uses of the call with
    // uses of the returned value.
    if (!TheCall->use_empty()) {
      ReturnInst *R = Returns[0];
      if (TheCall == R->getReturnValue())
        TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType()));
      else
        TheCall->replaceAllUsesWith(R->getReturnValue());
    }
    // Since we are now done with the Call/Invoke, we can delete it.
    TheCall->eraseFromParent();

    // Since we are now done with the return instruction, delete it also.
    Returns[0]->eraseFromParent();

    // We are now done with the inlining.
    return true;
  }

  // Otherwise, we have the normal case, of more than one block to inline or
  // multiple return sites.

  // We want to clone the entire callee function into the hole between the
  // "starter" and "ender" blocks.  How we accomplish this depends on whether
  // this is an invoke instruction or a call instruction.
  BasicBlock *AfterCallBB;
  BranchInst *CreatedBranchToNormalDest = NULL;
  if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) {

    // Add an unconditional branch to make this look like the CallInst case...
    CreatedBranchToNormalDest = BranchInst::Create(II->getNormalDest(), TheCall);

    // Split the basic block.  This guarantees that no PHI nodes will have to be
    // updated due to new incoming edges, and make the invoke case more
    // symmetric to the call case.
    AfterCallBB = OrigBB->splitBasicBlock(CreatedBranchToNormalDest,
                                          CalledFunc->getName()+".exit");

  } else {  // It's a call
    // If this is a call instruction, we need to split the basic block that
    // the call lives in.
    //
    AfterCallBB = OrigBB->splitBasicBlock(TheCall,
                                          CalledFunc->getName()+".exit");
  }

  // Change the branch that used to go to AfterCallBB to branch to the first
  // basic block of the inlined function.
  //
  TerminatorInst *Br = OrigBB->getTerminator();
  assert(Br && Br->getOpcode() == Instruction::Br &&
         "splitBasicBlock broken!");
  Br->setOperand(0, FirstNewBlock);


  // Now that the function is correct, make it a little bit nicer.  In
  // particular, move the basic blocks inserted from the end of the function
  // into the space made by splitting the source basic block.
  Caller->getBasicBlockList().splice(AfterCallBB, Caller->getBasicBlockList(),
                                     FirstNewBlock, Caller->end());

  // Handle all of the return instructions that we just cloned in, and eliminate
  // any users of the original call/invoke instruction.
  Type *RTy = CalledFunc->getReturnType();

  PHINode *PHI = 0;
  if (Returns.size() > 1) {
    // The PHI node should go at the front of the new basic block to merge all
    // possible incoming values.
    if (!TheCall->use_empty()) {
      PHI = PHINode::Create(RTy, Returns.size(), TheCall->getName(),
                            AfterCallBB->begin());
      // Anything that used the result of the function call should now use the
      // PHI node as their operand.
      TheCall->replaceAllUsesWith(PHI);
    }

    // Loop over all of the return instructions adding entries to the PHI node
    // as appropriate.
    if (PHI) {
      for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
        ReturnInst *RI = Returns[i];
        assert(RI->getReturnValue()->getType() == PHI->getType() &&
               "Ret value not consistent in function!");
        PHI->addIncoming(RI->getReturnValue(), RI->getParent());
      }
    }


    // Add a branch to the merge points and remove return instructions.
    DebugLoc Loc;
    for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
      ReturnInst *RI = Returns[i];
      BranchInst* BI = BranchInst::Create(AfterCallBB, RI);
      Loc = RI->getDebugLoc();
      BI->setDebugLoc(Loc);
      RI->eraseFromParent();
    }
    // We need to set the debug location to *somewhere* inside the
    // inlined function. The line number may be nonsensical, but the
    // instruction will at least be associated with the right
    // function.
    if (CreatedBranchToNormalDest)
      CreatedBranchToNormalDest->setDebugLoc(Loc);
  } else if (!Returns.empty()) {
    // Otherwise, if there is exactly one return value, just replace anything
    // using the return value of the call with the computed value.
    if (!TheCall->use_empty()) {
      if (TheCall == Returns[0]->getReturnValue())
        TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType()));
      else
        TheCall->replaceAllUsesWith(Returns[0]->getReturnValue());
    }

    // Update PHI nodes that use the ReturnBB to use the AfterCallBB.
    BasicBlock *ReturnBB = Returns[0]->getParent();
    ReturnBB->replaceAllUsesWith(AfterCallBB);

    // Splice the code from the return block into the block that it will return
    // to, which contains the code that was after the call.
    AfterCallBB->getInstList().splice(AfterCallBB->begin(),
                                      ReturnBB->getInstList());

    if (CreatedBranchToNormalDest)
      CreatedBranchToNormalDest->setDebugLoc(Returns[0]->getDebugLoc());

    // Delete the return instruction now and empty ReturnBB now.
    Returns[0]->eraseFromParent();
    ReturnBB->eraseFromParent();
  } else if (!TheCall->use_empty()) {
    // No returns, but something is using the return value of the call.  Just
    // nuke the result.
    TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType()));
  }

  // Since we are now done with the Call/Invoke, we can delete it.
  TheCall->eraseFromParent();

  // We should always be able to fold the entry block of the function into the
  // single predecessor of the block...
  assert(cast<BranchInst>(Br)->isUnconditional() && "splitBasicBlock broken!");
  BasicBlock *CalleeEntry = cast<BranchInst>(Br)->getSuccessor(0);

  // Splice the code entry block into calling block, right before the
  // unconditional branch.
  CalleeEntry->replaceAllUsesWith(OrigBB);  // Update PHI nodes
  OrigBB->getInstList().splice(Br, CalleeEntry->getInstList());

  // Remove the unconditional branch.
  OrigBB->getInstList().erase(Br);

  // Now we can remove the CalleeEntry block, which is now empty.
  Caller->getBasicBlockList().erase(CalleeEntry);

  // If we inserted a phi node, check to see if it has a single value (e.g. all
  // the entries are the same or undef).  If so, remove the PHI so it doesn't
  // block other optimizations.
  if (PHI) {
    if (Value *V = SimplifyInstruction(PHI, IFI.TD)) {
      PHI->replaceAllUsesWith(V);
      PHI->eraseFromParent();
    }
  }

  return true;
}
// InlineFunction - This function inlines the called function into the basic
// block of the caller.  This returns false if it is not possible to inline this
// call.  The program is still in a well defined state if this occurs though.
//
// Note that this only does one level of inlining.  For example, if the
// instruction 'call B' is inlined, and 'B' calls 'C', then the call to 'C' now
// exists in the instruction stream.  Similiarly this will inline a recursive
// function by one level.
//
bool llvm::InlineFunction(CallSite CS, CallGraph *CG, const TargetData *TD) {
  Instruction *TheCall = CS.getInstruction();
  assert(TheCall->getParent() && TheCall->getParent()->getParent() &&
         "Instruction not in function!");

  const Function *CalledFunc = CS.getCalledFunction();
  if (CalledFunc == 0 ||          // Can't inline external function or indirect
      CalledFunc->isDeclaration() || // call, or call to a vararg function!
      CalledFunc->getFunctionType()->isVarArg()) return false;


  // If the call to the callee is a non-tail call, we must clear the 'tail'
  // flags on any calls that we inline.
  bool MustClearTailCallFlags =
    isa<CallInst>(TheCall) && !cast<CallInst>(TheCall)->isTailCall();

  BasicBlock *OrigBB = TheCall->getParent();
  Function *Caller = OrigBB->getParent();

  // Get an iterator to the last basic block in the function, which will have
  // the new function inlined after it.
  //
  Function::iterator LastBlock = &Caller->back();

  // Make sure to capture all of the return instructions from the cloned
  // function.
  std::vector<ReturnInst*> Returns;
  ClonedCodeInfo InlinedFunctionInfo;
  Function::iterator FirstNewBlock;
  
  { // Scope to destroy ValueMap after cloning.
    DenseMap<const Value*, Value*> ValueMap;

    // Calculate the vector of arguments to pass into the function cloner, which
    // matches up the formal to the actual argument values.
    assert(std::distance(CalledFunc->arg_begin(), CalledFunc->arg_end()) ==
           std::distance(CS.arg_begin(), CS.arg_end()) &&
           "No varargs calls can be inlined!");
    CallSite::arg_iterator AI = CS.arg_begin();
    for (Function::const_arg_iterator I = CalledFunc->arg_begin(),
           E = CalledFunc->arg_end(); I != E; ++I, ++AI)
      ValueMap[I] = *AI;

    // We want the inliner to prune the code as it copies.  We would LOVE to
    // have no dead or constant instructions leftover after inlining occurs
    // (which can happen, e.g., because an argument was constant), but we'll be
    // happy with whatever the cloner can do.
    CloneAndPruneFunctionInto(Caller, CalledFunc, ValueMap, Returns, ".i",
                              &InlinedFunctionInfo, TD);
    
    // Remember the first block that is newly cloned over.
    FirstNewBlock = LastBlock; ++FirstNewBlock;
    
    // Update the callgraph if requested.
    if (CG)
      UpdateCallGraphAfterInlining(Caller, CalledFunc, FirstNewBlock, ValueMap,
                                   *CG);
  }
 
  // If there are any alloca instructions in the block that used to be the entry
  // block for the callee, move them to the entry block of the caller.  First
  // calculate which instruction they should be inserted before.  We insert the
  // instructions at the end of the current alloca list.
  //
  {
    BasicBlock::iterator InsertPoint = Caller->begin()->begin();
    for (BasicBlock::iterator I = FirstNewBlock->begin(),
           E = FirstNewBlock->end(); I != E; )
      if (AllocaInst *AI = dyn_cast<AllocaInst>(I++)) {
        // If the alloca is now dead, remove it.  This often occurs due to code
        // specialization.
        if (AI->use_empty()) {
          AI->eraseFromParent();
          continue;
        }
        
        if (isa<Constant>(AI->getArraySize())) {
          // Scan for the block of allocas that we can move over, and move them
          // all at once.
          while (isa<AllocaInst>(I) &&
                 isa<Constant>(cast<AllocaInst>(I)->getArraySize()))
            ++I;

          // Transfer all of the allocas over in a block.  Using splice means
          // that the instructions aren't removed from the symbol table, then
          // reinserted.
          Caller->getEntryBlock().getInstList().splice(
              InsertPoint,
              FirstNewBlock->getInstList(),
              AI, I);
        }
      }
  }

  // If the inlined code contained dynamic alloca instructions, wrap the inlined
  // code with llvm.stacksave/llvm.stackrestore intrinsics.
  if (InlinedFunctionInfo.ContainsDynamicAllocas) {
    Module *M = Caller->getParent();
    const Type *BytePtr = PointerType::get(Type::Int8Ty);
    // Get the two intrinsics we care about.
    Constant *StackSave, *StackRestore;
    StackSave    = M->getOrInsertFunction("llvm.stacksave", BytePtr, NULL);
    StackRestore = M->getOrInsertFunction("llvm.stackrestore", Type::VoidTy,
                                          BytePtr, NULL);

    // If we are preserving the callgraph, add edges to the stacksave/restore
    // functions for the calls we insert.
    CallGraphNode *StackSaveCGN = 0, *StackRestoreCGN = 0, *CallerNode = 0;
    if (CG) {
      // We know that StackSave/StackRestore are Function*'s, because they are
      // intrinsics which must have the right types.
      StackSaveCGN    = CG->getOrInsertFunction(cast<Function>(StackSave));
      StackRestoreCGN = CG->getOrInsertFunction(cast<Function>(StackRestore));
      CallerNode = (*CG)[Caller];
    }
      
    // Insert the llvm.stacksave.
    CallInst *SavedPtr = new CallInst(StackSave, "savedstack", 
                                      FirstNewBlock->begin());
    if (CG) CallerNode->addCalledFunction(SavedPtr, StackSaveCGN);
      
    // Insert a call to llvm.stackrestore before any return instructions in the
    // inlined function.
    for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
      CallInst *CI = new CallInst(StackRestore, SavedPtr, "", Returns[i]);
      if (CG) CallerNode->addCalledFunction(CI, StackRestoreCGN);
    }

    // Count the number of StackRestore calls we insert.
    unsigned NumStackRestores = Returns.size();
    
    // If we are inlining an invoke instruction, insert restores before each
    // unwind.  These unwinds will be rewritten into branches later.
    if (InlinedFunctionInfo.ContainsUnwinds && isa<InvokeInst>(TheCall)) {
      for (Function::iterator BB = FirstNewBlock, E = Caller->end();
           BB != E; ++BB)
        if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
          new CallInst(StackRestore, SavedPtr, "", UI);
          ++NumStackRestores;
        }
    }
  }

  // If we are inlining tail call instruction through a call site that isn't 
  // marked 'tail', we must remove the tail marker for any calls in the inlined
  // code.
  if (MustClearTailCallFlags && InlinedFunctionInfo.ContainsCalls) {
    for (Function::iterator BB = FirstNewBlock, E = Caller->end();
         BB != E; ++BB)
      for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
        if (CallInst *CI = dyn_cast<CallInst>(I))
          CI->setTailCall(false);
  }

  // If we are inlining for an invoke instruction, we must make sure to rewrite
  // any inlined 'unwind' instructions into branches to the invoke exception
  // destination, and call instructions into invoke instructions.
  if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall))
    HandleInlinedInvoke(II, FirstNewBlock, InlinedFunctionInfo);

  // If we cloned in _exactly one_ basic block, and if that block ends in a
  // return instruction, we splice the body of the inlined callee directly into
  // the calling basic block.
  if (Returns.size() == 1 && std::distance(FirstNewBlock, Caller->end()) == 1) {
    // Move all of the instructions right before the call.
    OrigBB->getInstList().splice(TheCall, FirstNewBlock->getInstList(),
                                 FirstNewBlock->begin(), FirstNewBlock->end());
    // Remove the cloned basic block.
    Caller->getBasicBlockList().pop_back();

    // If the call site was an invoke instruction, add a branch to the normal
    // destination.
    if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall))
      new BranchInst(II->getNormalDest(), TheCall);

    // If the return instruction returned a value, replace uses of the call with
    // uses of the returned value.
    if (!TheCall->use_empty())
      TheCall->replaceAllUsesWith(Returns[0]->getReturnValue());

    // Since we are now done with the Call/Invoke, we can delete it.
    TheCall->getParent()->getInstList().erase(TheCall);

    // Since we are now done with the return instruction, delete it also.
    Returns[0]->getParent()->getInstList().erase(Returns[0]);

    // We are now done with the inlining.
    return true;
  }

  // Otherwise, we have the normal case, of more than one block to inline or
  // multiple return sites.

  // We want to clone the entire callee function into the hole between the
  // "starter" and "ender" blocks.  How we accomplish this depends on whether
  // this is an invoke instruction or a call instruction.
  BasicBlock *AfterCallBB;
  if (InvokeInst *II = dyn_cast<InvokeInst>(TheCall)) {

    // Add an unconditional branch to make this look like the CallInst case...
    BranchInst *NewBr = new BranchInst(II->getNormalDest(), TheCall);

    // Split the basic block.  This guarantees that no PHI nodes will have to be
    // updated due to new incoming edges, and make the invoke case more
    // symmetric to the call case.
    AfterCallBB = OrigBB->splitBasicBlock(NewBr,
                                          CalledFunc->getName()+".exit");

  } else {  // It's a call
    // If this is a call instruction, we need to split the basic block that
    // the call lives in.
    //
    AfterCallBB = OrigBB->splitBasicBlock(TheCall,
                                          CalledFunc->getName()+".exit");
  }

  // Change the branch that used to go to AfterCallBB to branch to the first
  // basic block of the inlined function.
  //
  TerminatorInst *Br = OrigBB->getTerminator();
  assert(Br && Br->getOpcode() == Instruction::Br &&
         "splitBasicBlock broken!");
  Br->setOperand(0, FirstNewBlock);


  // Now that the function is correct, make it a little bit nicer.  In
  // particular, move the basic blocks inserted from the end of the function
  // into the space made by splitting the source basic block.
  //
  Caller->getBasicBlockList().splice(AfterCallBB, Caller->getBasicBlockList(),
                                     FirstNewBlock, Caller->end());

  // Handle all of the return instructions that we just cloned in, and eliminate
  // any users of the original call/invoke instruction.
  if (Returns.size() > 1) {
    // The PHI node should go at the front of the new basic block to merge all
    // possible incoming values.
    //
    PHINode *PHI = 0;
    if (!TheCall->use_empty()) {
      PHI = new PHINode(CalledFunc->getReturnType(),
                        TheCall->getName(), AfterCallBB->begin());

      // Anything that used the result of the function call should now use the
      // PHI node as their operand.
      //
      TheCall->replaceAllUsesWith(PHI);
    }

    // Loop over all of the return instructions, turning them into unconditional
    // branches to the merge point now, and adding entries to the PHI node as
    // appropriate.
    for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
      ReturnInst *RI = Returns[i];

      if (PHI) {
        assert(RI->getReturnValue() && "Ret should have value!");
        assert(RI->getReturnValue()->getType() == PHI->getType() &&
               "Ret value not consistent in function!");
        PHI->addIncoming(RI->getReturnValue(), RI->getParent());
      }

      // Add a branch to the merge point where the PHI node lives if it exists.
      new BranchInst(AfterCallBB, RI);

      // Delete the return instruction now
      RI->getParent()->getInstList().erase(RI);
    }

  } else if (!Returns.empty()) {
    // Otherwise, if there is exactly one return value, just replace anything
    // using the return value of the call with the computed value.
    if (!TheCall->use_empty())
      TheCall->replaceAllUsesWith(Returns[0]->getReturnValue());

    // Splice the code from the return block into the block that it will return
    // to, which contains the code that was after the call.
    BasicBlock *ReturnBB = Returns[0]->getParent();
    AfterCallBB->getInstList().splice(AfterCallBB->begin(),
                                      ReturnBB->getInstList());

    // Update PHI nodes that use the ReturnBB to use the AfterCallBB.
    ReturnBB->replaceAllUsesWith(AfterCallBB);

    // Delete the return instruction now and empty ReturnBB now.
    Returns[0]->eraseFromParent();
    ReturnBB->eraseFromParent();
  } else if (!TheCall->use_empty()) {
    // No returns, but something is using the return value of the call.  Just
    // nuke the result.
    TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType()));
  }

  // Since we are now done with the Call/Invoke, we can delete it.
  TheCall->eraseFromParent();

  // We should always be able to fold the entry block of the function into the
  // single predecessor of the block...
  assert(cast<BranchInst>(Br)->isUnconditional() && "splitBasicBlock broken!");
  BasicBlock *CalleeEntry = cast<BranchInst>(Br)->getSuccessor(0);

  // Splice the code entry block into calling block, right before the
  // unconditional branch.
  OrigBB->getInstList().splice(Br, CalleeEntry->getInstList());
  CalleeEntry->replaceAllUsesWith(OrigBB);  // Update PHI nodes

  // Remove the unconditional branch.
  OrigBB->getInstList().erase(Br);

  // Now we can remove the CalleeEntry block, which is now empty.
  Caller->getBasicBlockList().erase(CalleeEntry);
  
  return true;
}
Exemplo n.º 16
0
/// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto,
/// except that it does some simple constant prop and DCE on the fly.  The
/// effect of this is to copy significantly less code in cases where (for
/// example) a function call with constant arguments is inlined, and those
/// constant arguments cause a significant amount of code in the callee to be
/// dead.  Since this doesn't produce an exact copy of the input, it can't be
/// used for things like CloneFunction or CloneModule.
void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
                                     ValueToValueMapTy &VMap,
                                     bool ModuleLevelChanges,
                                     SmallVectorImpl<ReturnInst*> &Returns,
                                     const char *NameSuffix, 
                                     ClonedCodeInfo *CodeInfo,
                                     const TargetData *TD,
                                     Instruction *TheCall) {
  assert(NameSuffix && "NameSuffix cannot be null!");
  
#ifndef NDEBUG
  for (Function::const_arg_iterator II = OldFunc->arg_begin(), 
       E = OldFunc->arg_end(); II != E; ++II)
    assert(VMap.count(II) && "No mapping from source argument specified!");
#endif

  PruningFunctionCloner PFC(NewFunc, OldFunc, VMap, ModuleLevelChanges,
                            Returns, NameSuffix, CodeInfo, TD);

  // Clone the entry block, and anything recursively reachable from it.
  std::vector<const BasicBlock*> CloneWorklist;
  CloneWorklist.push_back(&OldFunc->getEntryBlock());
  while (!CloneWorklist.empty()) {
    const BasicBlock *BB = CloneWorklist.back();
    CloneWorklist.pop_back();
    PFC.CloneBlock(BB, CloneWorklist);
  }
  
  // Loop over all of the basic blocks in the old function.  If the block was
  // reachable, we have cloned it and the old block is now in the value map:
  // insert it into the new function in the right order.  If not, ignore it.
  //
  // Defer PHI resolution until rest of function is resolved.
  SmallVector<const PHINode*, 16> PHIToResolve;
  for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
       BI != BE; ++BI) {
    Value *V = VMap[BI];
    BasicBlock *NewBB = cast_or_null<BasicBlock>(V);
    if (NewBB == 0) continue;  // Dead block.

    // Add the new block to the new function.
    NewFunc->getBasicBlockList().push_back(NewBB);
    
    // Loop over all of the instructions in the block, fixing up operand
    // references as we go.  This uses VMap to do all the hard work.
    //
    BasicBlock::iterator I = NewBB->begin();

    DebugLoc TheCallDL;
    if (TheCall) 
      TheCallDL = TheCall->getDebugLoc();
    
    // Handle PHI nodes specially, as we have to remove references to dead
    // blocks.
    if (PHINode *PN = dyn_cast<PHINode>(I)) {
      // Skip over all PHI nodes, remembering them for later.
      BasicBlock::const_iterator OldI = BI->begin();
      for (; (PN = dyn_cast<PHINode>(I)); ++I, ++OldI)
        PHIToResolve.push_back(cast<PHINode>(OldI));
    }
    
    // Otherwise, remap the rest of the instructions normally.
    for (; I != NewBB->end(); ++I)
      RemapInstruction(I, VMap,
                       ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges);
  }
  
  // Defer PHI resolution until rest of function is resolved, PHI resolution
  // requires the CFG to be up-to-date.
  for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) {
    const PHINode *OPN = PHIToResolve[phino];
    unsigned NumPreds = OPN->getNumIncomingValues();
    const BasicBlock *OldBB = OPN->getParent();
    BasicBlock *NewBB = cast<BasicBlock>(VMap[OldBB]);

    // Map operands for blocks that are live and remove operands for blocks
    // that are dead.
    for (; phino != PHIToResolve.size() &&
         PHIToResolve[phino]->getParent() == OldBB; ++phino) {
      OPN = PHIToResolve[phino];
      PHINode *PN = cast<PHINode>(VMap[OPN]);
      for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) {
        Value *V = VMap[PN->getIncomingBlock(pred)];
        if (BasicBlock *MappedBlock = cast_or_null<BasicBlock>(V)) {
          Value *InVal = MapValue(PN->getIncomingValue(pred),
                                  VMap, 
                        ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges);
          assert(InVal && "Unknown input value?");
          PN->setIncomingValue(pred, InVal);
          PN->setIncomingBlock(pred, MappedBlock);
        } else {
          PN->removeIncomingValue(pred, false);
          --pred, --e;  // Revisit the next entry.
        }
      } 
    }
    
    // The loop above has removed PHI entries for those blocks that are dead
    // and has updated others.  However, if a block is live (i.e. copied over)
    // but its terminator has been changed to not go to this block, then our
    // phi nodes will have invalid entries.  Update the PHI nodes in this
    // case.
    PHINode *PN = cast<PHINode>(NewBB->begin());
    NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB));
    if (NumPreds != PN->getNumIncomingValues()) {
      assert(NumPreds < PN->getNumIncomingValues());
      // Count how many times each predecessor comes to this block.
      std::map<BasicBlock*, unsigned> PredCount;
      for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB);
           PI != E; ++PI)
        --PredCount[*PI];
      
      // Figure out how many entries to remove from each PHI.
      for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
        ++PredCount[PN->getIncomingBlock(i)];
      
      // At this point, the excess predecessor entries are positive in the
      // map.  Loop over all of the PHIs and remove excess predecessor
      // entries.
      BasicBlock::iterator I = NewBB->begin();
      for (; (PN = dyn_cast<PHINode>(I)); ++I) {
        for (std::map<BasicBlock*, unsigned>::iterator PCI =PredCount.begin(),
             E = PredCount.end(); PCI != E; ++PCI) {
          BasicBlock *Pred     = PCI->first;
          for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove)
            PN->removeIncomingValue(Pred, false);
        }
      }
    }
    
    // If the loops above have made these phi nodes have 0 or 1 operand,
    // replace them with undef or the input value.  We must do this for
    // correctness, because 0-operand phis are not valid.
    PN = cast<PHINode>(NewBB->begin());
    if (PN->getNumIncomingValues() == 0) {
      BasicBlock::iterator I = NewBB->begin();
      BasicBlock::const_iterator OldI = OldBB->begin();
      while ((PN = dyn_cast<PHINode>(I++))) {
        Value *NV = UndefValue::get(PN->getType());
        PN->replaceAllUsesWith(NV);
        assert(VMap[OldI] == PN && "VMap mismatch");
        VMap[OldI] = NV;
        PN->eraseFromParent();
        ++OldI;
      }
    }
    // NOTE: We cannot eliminate single entry phi nodes here, because of
    // VMap.  Single entry phi nodes can have multiple VMap entries
    // pointing at them.  Thus, deleting one would require scanning the VMap
    // to update any entries in it that would require that.  This would be
    // really slow.
  }
  
  // Now that the inlined function body has been fully constructed, go through
  // and zap unconditional fall-through branches.  This happen all the time when
  // specializing code: code specialization turns conditional branches into
  // uncond branches, and this code folds them.
  Function::iterator I = cast<BasicBlock>(VMap[&OldFunc->getEntryBlock()]);
  while (I != NewFunc->end()) {
    BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator());
    if (!BI || BI->isConditional()) { ++I; continue; }
    
    // Note that we can't eliminate uncond branches if the destination has
    // single-entry PHI nodes.  Eliminating the single-entry phi nodes would
    // require scanning the VMap to update any entries that point to the phi
    // node.
    BasicBlock *Dest = BI->getSuccessor(0);
    if (!Dest->getSinglePredecessor() || isa<PHINode>(Dest->begin())) {
      ++I; continue;
    }
    
    // We know all single-entry PHI nodes in the inlined function have been
    // removed, so we just need to splice the blocks.
    BI->eraseFromParent();
    
    // Make all PHI nodes that referred to Dest now refer to I as their source.
    Dest->replaceAllUsesWith(I);

    // Move all the instructions in the succ to the pred.
    I->getInstList().splice(I->end(), Dest->getInstList());
    
    // Remove the dest block.
    Dest->eraseFromParent();
    
    // Do not increment I, iteratively merge all things this block branches to.
  }
}
// RemoveDeadStuffFromFunction - Remove any arguments and return values from F
// that are not in LiveValues. Transform the function and all of the callees of
// the function to not have these arguments and return values.
//
bool DAE::RemoveDeadStuffFromFunction(Function *F) {
  // Don't modify fully live functions
  if (LiveFunctions.count(F))
    return false;

  // Start by computing a new prototype for the function, which is the same as
  // the old function, but has fewer arguments and a different return type.
  FunctionType *FTy = F->getFunctionType();
  std::vector<Type*> Params;

  // Keep track of if we have a live 'returned' argument
  bool HasLiveReturnedArg = false;

  // Set up to build a new list of parameter attributes.
  SmallVector<AttributeSet, 8> AttributesVec;
  const AttributeSet &PAL = F->getAttributes();

  // Remember which arguments are still alive.
  SmallVector<bool, 10> ArgAlive(FTy->getNumParams(), false);
  // Construct the new parameter list from non-dead arguments. Also construct
  // a new set of parameter attributes to correspond. Skip the first parameter
  // attribute, since that belongs to the return value.
  unsigned i = 0;
  for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
       I != E; ++I, ++i) {
    RetOrArg Arg = CreateArg(F, i);
    if (LiveValues.erase(Arg)) {
      Params.push_back(I->getType());
      ArgAlive[i] = true;

      // Get the original parameter attributes (skipping the first one, that is
      // for the return value.
      if (PAL.hasAttributes(i + 1)) {
        AttrBuilder B(PAL, i + 1);
        if (B.contains(Attribute::Returned))
          HasLiveReturnedArg = true;
        AttributesVec.
          push_back(AttributeSet::get(F->getContext(), Params.size(), B));
      }
    } else {
      ++NumArgumentsEliminated;
      DEBUG(dbgs() << "DAE - Removing argument " << i << " (" << I->getName()
            << ") from " << F->getName() << "\n");
    }
  }

  // Find out the new return value.
  Type *RetTy = FTy->getReturnType();
  Type *NRetTy = nullptr;
  unsigned RetCount = NumRetVals(F);

  // -1 means unused, other numbers are the new index
  SmallVector<int, 5> NewRetIdxs(RetCount, -1);
  std::vector<Type*> RetTypes;

  // If there is a function with a live 'returned' argument but a dead return
  // value, then there are two possible actions:
  // 1) Eliminate the return value and take off the 'returned' attribute on the
  //    argument.
  // 2) Retain the 'returned' attribute and treat the return value (but not the
  //    entire function) as live so that it is not eliminated.
  // 
  // It's not clear in the general case which option is more profitable because,
  // even in the absence of explicit uses of the return value, code generation
  // is free to use the 'returned' attribute to do things like eliding
  // save/restores of registers across calls. Whether or not this happens is
  // target and ABI-specific as well as depending on the amount of register
  // pressure, so there's no good way for an IR-level pass to figure this out.
  //
  // Fortunately, the only places where 'returned' is currently generated by
  // the FE are places where 'returned' is basically free and almost always a
  // performance win, so the second option can just be used always for now.
  //
  // This should be revisited if 'returned' is ever applied more liberally.
  if (RetTy->isVoidTy() || HasLiveReturnedArg) {
    NRetTy = RetTy;
  } else {
    // Look at each of the original return values individually.
    for (unsigned i = 0; i != RetCount; ++i) {
      RetOrArg Ret = CreateRet(F, i);
      if (LiveValues.erase(Ret)) {
        RetTypes.push_back(getRetComponentType(F, i));
        NewRetIdxs[i] = RetTypes.size() - 1;
      } else {
        ++NumRetValsEliminated;
        DEBUG(dbgs() << "DAE - Removing return value " << i << " from "
              << F->getName() << "\n");
      }
    }
    if (RetTypes.size() > 1) {
      // More than one return type? Reduce it down to size.
      if (StructType *STy = dyn_cast<StructType>(RetTy)) {
        // Make the new struct packed if we used to return a packed struct
        // already.
        NRetTy = StructType::get(STy->getContext(), RetTypes, STy->isPacked());
      } else {
        assert(isa<ArrayType>(RetTy) && "unexpected multi-value return");
        NRetTy = ArrayType::get(RetTypes[0], RetTypes.size());
      }
    } else if (RetTypes.size() == 1)
      // One return type? Just a simple value then, but only if we didn't use to
      // return a struct with that simple value before.
      NRetTy = RetTypes.front();
    else if (RetTypes.size() == 0)
      // No return types? Make it void, but only if we didn't use to return {}.
      NRetTy = Type::getVoidTy(F->getContext());
  }

  assert(NRetTy && "No new return type found?");

  // The existing function return attributes.
  AttributeSet RAttrs = PAL.getRetAttributes();

  // Remove any incompatible attributes, but only if we removed all return
  // values. Otherwise, ensure that we don't have any conflicting attributes
  // here. Currently, this should not be possible, but special handling might be
  // required when new return value attributes are added.
  if (NRetTy->isVoidTy())
    RAttrs = RAttrs.removeAttributes(NRetTy->getContext(),
                                     AttributeSet::ReturnIndex,
                                     AttributeFuncs::typeIncompatible(NRetTy));
  else
    assert(!AttrBuilder(RAttrs, AttributeSet::ReturnIndex).
             overlaps(AttributeFuncs::typeIncompatible(NRetTy)) &&
           "Return attributes no longer compatible?");

  if (RAttrs.hasAttributes(AttributeSet::ReturnIndex))
    AttributesVec.push_back(AttributeSet::get(NRetTy->getContext(), RAttrs));

  if (PAL.hasAttributes(AttributeSet::FunctionIndex))
    AttributesVec.push_back(AttributeSet::get(F->getContext(),
                                              PAL.getFnAttributes()));

  // Reconstruct the AttributesList based on the vector we constructed.
  AttributeSet NewPAL = AttributeSet::get(F->getContext(), AttributesVec);

  // Create the new function type based on the recomputed parameters.
  FunctionType *NFTy = FunctionType::get(NRetTy, Params, FTy->isVarArg());

  // No change?
  if (NFTy == FTy)
    return false;

  // Create the new function body and insert it into the module...
  Function *NF = Function::Create(NFTy, F->getLinkage());
  NF->copyAttributesFrom(F);
  NF->setAttributes(NewPAL);
  // Insert the new function before the old function, so we won't be processing
  // it again.
  F->getParent()->getFunctionList().insert(F->getIterator(), NF);
  NF->takeName(F);

  // Loop over all of the callers of the function, transforming the call sites
  // to pass in a smaller number of arguments into the new function.
  //
  std::vector<Value*> Args;
  while (!F->use_empty()) {
    CallSite CS(F->user_back());
    Instruction *Call = CS.getInstruction();

    AttributesVec.clear();
    const AttributeSet &CallPAL = CS.getAttributes();

    // The call return attributes.
    AttributeSet RAttrs = CallPAL.getRetAttributes();

    // Adjust in case the function was changed to return void.
    RAttrs = RAttrs.removeAttributes(NRetTy->getContext(),
                                     AttributeSet::ReturnIndex,
                        AttributeFuncs::typeIncompatible(NF->getReturnType()));
    if (RAttrs.hasAttributes(AttributeSet::ReturnIndex))
      AttributesVec.push_back(AttributeSet::get(NF->getContext(), RAttrs));

    // Declare these outside of the loops, so we can reuse them for the second
    // loop, which loops the varargs.
    CallSite::arg_iterator I = CS.arg_begin();
    unsigned i = 0;
    // Loop over those operands, corresponding to the normal arguments to the
    // original function, and add those that are still alive.
    for (unsigned e = FTy->getNumParams(); i != e; ++I, ++i)
      if (ArgAlive[i]) {
        Args.push_back(*I);
        // Get original parameter attributes, but skip return attributes.
        if (CallPAL.hasAttributes(i + 1)) {
          AttrBuilder B(CallPAL, i + 1);
          // If the return type has changed, then get rid of 'returned' on the
          // call site. The alternative is to make all 'returned' attributes on
          // call sites keep the return value alive just like 'returned'
          // attributes on function declaration but it's less clearly a win
          // and this is not an expected case anyway
          if (NRetTy != RetTy && B.contains(Attribute::Returned))
            B.removeAttribute(Attribute::Returned);
          AttributesVec.
            push_back(AttributeSet::get(F->getContext(), Args.size(), B));
        }
      }

    // Push any varargs arguments on the list. Don't forget their attributes.
    for (CallSite::arg_iterator E = CS.arg_end(); I != E; ++I, ++i) {
      Args.push_back(*I);
      if (CallPAL.hasAttributes(i + 1)) {
        AttrBuilder B(CallPAL, i + 1);
        AttributesVec.
          push_back(AttributeSet::get(F->getContext(), Args.size(), B));
      }
    }

    if (CallPAL.hasAttributes(AttributeSet::FunctionIndex))
      AttributesVec.push_back(AttributeSet::get(Call->getContext(),
                                                CallPAL.getFnAttributes()));

    // Reconstruct the AttributesList based on the vector we constructed.
    AttributeSet NewCallPAL = AttributeSet::get(F->getContext(), AttributesVec);

    Instruction *New;
    if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
      New = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
                               Args, "", Call->getParent());
      cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
      cast<InvokeInst>(New)->setAttributes(NewCallPAL);
    } else {
      New = CallInst::Create(NF, Args, "", Call);
      cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
      cast<CallInst>(New)->setAttributes(NewCallPAL);
      if (cast<CallInst>(Call)->isTailCall())
        cast<CallInst>(New)->setTailCall();
    }
    New->setDebugLoc(Call->getDebugLoc());

    Args.clear();

    if (!Call->use_empty()) {
      if (New->getType() == Call->getType()) {
        // Return type not changed? Just replace users then.
        Call->replaceAllUsesWith(New);
        New->takeName(Call);
      } else if (New->getType()->isVoidTy()) {
        // Our return value has uses, but they will get removed later on.
        // Replace by null for now.
        if (!Call->getType()->isX86_MMXTy())
          Call->replaceAllUsesWith(Constant::getNullValue(Call->getType()));
      } else {
        assert((RetTy->isStructTy() || RetTy->isArrayTy()) &&
               "Return type changed, but not into a void. The old return type"
               " must have been a struct or an array!");
        Instruction *InsertPt = Call;
        if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
          BasicBlock *NewEdge = SplitEdge(New->getParent(), II->getNormalDest());
          InsertPt = &*NewEdge->getFirstInsertionPt();
        }

        // We used to return a struct or array. Instead of doing smart stuff
        // with all the uses, we will just rebuild it using extract/insertvalue
        // chaining and let instcombine clean that up.
        //
        // Start out building up our return value from undef
        Value *RetVal = UndefValue::get(RetTy);
        for (unsigned i = 0; i != RetCount; ++i)
          if (NewRetIdxs[i] != -1) {
            Value *V;
            if (RetTypes.size() > 1)
              // We are still returning a struct, so extract the value from our
              // return value
              V = ExtractValueInst::Create(New, NewRetIdxs[i], "newret",
                                           InsertPt);
            else
              // We are now returning a single element, so just insert that
              V = New;
            // Insert the value at the old position
            RetVal = InsertValueInst::Create(RetVal, V, i, "oldret", InsertPt);
          }
        // Now, replace all uses of the old call instruction with the return
        // struct we built
        Call->replaceAllUsesWith(RetVal);
        New->takeName(Call);
      }
    }

    // Finally, remove the old call from the program, reducing the use-count of
    // F.
    Call->eraseFromParent();
  }

  // Since we have now created the new function, splice the body of the old
  // function right into the new function, leaving the old rotting hulk of the
  // function empty.
  NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList());

  // Loop over the argument list, transferring uses of the old arguments over to
  // the new arguments, also transferring over the names as well.
  i = 0;
  for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(),
       I2 = NF->arg_begin(); I != E; ++I, ++i)
    if (ArgAlive[i]) {
      // If this is a live argument, move the name and users over to the new
      // version.
      I->replaceAllUsesWith(&*I2);
      I2->takeName(&*I);
      ++I2;
    } else {
      // If this argument is dead, replace any uses of it with null constants
      // (these are guaranteed to become unused later on).
      if (!I->getType()->isX86_MMXTy())
        I->replaceAllUsesWith(Constant::getNullValue(I->getType()));
    }

  // If we change the return value of the function we must rewrite any return
  // instructions.  Check this now.
  if (F->getReturnType() != NF->getReturnType())
    for (Function::iterator BB = NF->begin(), E = NF->end(); BB != E; ++BB)
      if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
        Value *RetVal;

        if (NFTy->getReturnType()->isVoidTy()) {
          RetVal = nullptr;
        } else {
          assert(RetTy->isStructTy() || RetTy->isArrayTy());
          // The original return value was a struct or array, insert
          // extractvalue/insertvalue chains to extract only the values we need
          // to return and insert them into our new result.
          // This does generate messy code, but we'll let it to instcombine to
          // clean that up.
          Value *OldRet = RI->getOperand(0);
          // Start out building up our return value from undef
          RetVal = UndefValue::get(NRetTy);
          for (unsigned i = 0; i != RetCount; ++i)
            if (NewRetIdxs[i] != -1) {
              ExtractValueInst *EV = ExtractValueInst::Create(OldRet, i,
                                                              "oldret", RI);
              if (RetTypes.size() > 1) {
                // We're still returning a struct, so reinsert the value into
                // our new return value at the new index

                RetVal = InsertValueInst::Create(RetVal, EV, NewRetIdxs[i],
                                                 "newret", RI);
              } else {
                // We are now only returning a simple value, so just return the
                // extracted value.
                RetVal = EV;
              }
            }
        }
        // Replace the return instruction with one returning the new return
        // value (possibly 0 if we became void).
        ReturnInst::Create(F->getContext(), RetVal, RI);
        BB->getInstList().erase(RI);
      }

  // Patch the pointer to LLVM function in debug info descriptor.
  NF->setSubprogram(F->getSubprogram());

  // Now that the old function is dead, delete it.
  F->eraseFromParent();

  return true;
}
Exemplo n.º 18
0
/*
 * Rewrite the given module according to the ComponentInterfaceTransformer.
 */
bool
TransformComponentWithoutUse(Module& M, ComponentInterfaceTransform& T)
{
    assert(T.interface != NULL);
    bool modified = false;
    for (Module::iterator f = M.begin(), e = M.end(); f != e; ++f) {
        for (Function::iterator bb = f->begin(), bbe = f->end(); bb != bbe; ++bb) {
            for (BasicBlock::iterator I = bb->begin(), E = bb->end(); I != E; ++I) {
                // TODO: Handle the operands


                CallSite call;
                if (CallInst* ci = dyn_cast<CallInst>(&*I)) {
                    if (ci->isInlineAsm())
                        continue;
                    call = CallSite(ci);
                } else if (InvokeInst* ci = dyn_cast<InvokeInst>(&*I)) {
                    call = CallSite(ci);
                } else {
                    // TODO: We need to find all references, including ones stored in variables
                    //       we'll be conservative and say that if it is stored in a variable then
                    //       we can't optimize it at all
                    continue;
                }

                Function* target = call.getCalledFunction();
                if (target == NULL || !target->isDeclaration()) {
                    continue;
                }

                //iam          const CallRewrite* const rw = T.lookupRewrite(target->getNameStr(), call.arg_begin(), call.arg_end());
                const CallRewrite* const rw = T.lookupRewrite(target->getName().str(), call.arg_begin(), call.arg_end());

                if (rw == NULL) {
                    // There is no rewrite for this function
                    continue;
                }

                // Get/Create the function
                Function* newTarget = M.getFunction(rw->function);
                if (newTarget == NULL) {
                    // There isn't a function, we need to construct it
                    FunctionType* newType = target->getFunctionType();
                    std::vector<Type*> argTypes;
                    for (std::vector<unsigned>::const_iterator i = rw->args.begin(), e =
                                rw->args.end(); i != e; ++i)
                        argTypes.push_back(newType->getParamType(*i));
                    ArrayRef<Type*> params(argTypes);
                    newType = FunctionType::get(target->getReturnType(), params, target->isVarArg());

                    newTarget = dyn_cast<Function> (M.getOrInsertFunction(rw->function,
                                                    newType));
                }

                assert(newTarget != NULL);

                Instruction* newInst = specializeCallSite(I, newTarget, rw->args);
                llvm::ReplaceInstWithInst(bb->getInstList(), I, newInst);
                modified = true;
            }
        }
    }
    return modified;
}