C++ BinaryOperator::setOperand方法代码示例

// Given an expression of the form '(A+B)+(D+C)', turn it into '(((A+B)+C)+D)'.
// Note that if D is also part of the expression tree that we recurse to
// linearize it as well.  Besides that case, this does not recurse into A,B, or
// C.
void Reassociate::LinearizeExpr(BinaryOperator *I) {
  BinaryOperator *LHS = cast<BinaryOperator>(I->getOperand(0));
  BinaryOperator *RHS = cast<BinaryOperator>(I->getOperand(1));
  assert(isReassociableOp(LHS, I->getOpcode()) &&
         isReassociableOp(RHS, I->getOpcode()) &&
         "Not an expression that needs linearization?");

  DEBUG(dbgs() << "Linear" << *LHS << '\n' << *RHS << '\n' << *I << '\n');

  // Move the RHS instruction to live immediately before I, avoiding breaking
  // dominator properties.
  RHS->moveBefore(I);

  // Move operands around to do the linearization.
  I->setOperand(1, RHS->getOperand(0));
  RHS->setOperand(0, LHS);
  I->setOperand(0, RHS);

  // Conservatively clear all the optional flags, which may not hold
  // after the reassociation.
  I->clearSubclassOptionalData();
  LHS->clearSubclassOptionalData();
  RHS->clearSubclassOptionalData();

  ++NumLinear;
  MadeChange = true;
  DEBUG(dbgs() << "Linearized: " << *I << '\n');

  // If D is part of this expression tree, tail recurse.
  if (isReassociableOp(I->getOperand(1), I->getOpcode()))
    LinearizeExpr(I);
}

Value *ConstantOffsetExtractor::removeConstOffset(unsigned ChainIndex) {
  if (ChainIndex == 0) {
    assert(isa<ConstantInt>(UserChain[ChainIndex]));
    return ConstantInt::getNullValue(UserChain[ChainIndex]->getType());
  }

  BinaryOperator *BO = cast<BinaryOperator>(UserChain[ChainIndex]);
  unsigned OpNo = (BO->getOperand(0) == UserChain[ChainIndex - 1] ? 0 : 1);
  assert(BO->getOperand(OpNo) == UserChain[ChainIndex - 1]);
  Value *NextInChain = removeConstOffset(ChainIndex - 1);
  Value *TheOther = BO->getOperand(1 - OpNo);

  // If NextInChain is 0 and not the LHS of a sub, we can simplify the
  // sub-expression to be just TheOther.
  if (ConstantInt *CI = dyn_cast<ConstantInt>(NextInChain)) {
    if (CI->isZero() && !(BO->getOpcode() == Instruction::Sub && OpNo == 0))
      return TheOther;
  }

  if (BO->getOpcode() == Instruction::Or) {
    // Rebuild "or" as "add", because "or" may be invalid for the new
    // epxression.
    //
    // For instance, given
    //   a | (b + 5) where a and b + 5 have no common bits,
    // we can extract 5 as the constant offset.
    //
    // However, reusing the "or" in the new index would give us
    //   (a | b) + 5
    // which does not equal a | (b + 5).
    //
    // Replacing the "or" with "add" is fine, because
    //   a | (b + 5) = a + (b + 5) = (a + b) + 5
    if (OpNo == 0) {
      return BinaryOperator::CreateAdd(NextInChain, TheOther, BO->getName(),
                                       IP);
    } else {
      return BinaryOperator::CreateAdd(TheOther, NextInChain, BO->getName(),
                                       IP);
    }
  }

  // We can reuse BO in this case, because the new expression shares the same
  // instruction type and BO is used at most once.
  assert(BO->getNumUses() <= 1 &&
         "distributeExtsAndCloneChain clones each BinaryOperator in "
         "UserChain, so no one should be used more than "
         "once");
  BO->setOperand(OpNo, NextInChain);
  BO->setHasNoSignedWrap(false);
  BO->setHasNoUnsignedWrap(false);
  // Make sure it appears after all instructions we've inserted so far.
  BO->moveBefore(IP);
  return BO;
}

/// SimplifyDivRemOfSelect - Try to fold a divide or remainder of a select
/// instruction.
bool InstCombiner::SimplifyDivRemOfSelect(BinaryOperator &I) {
  SelectInst *SI = cast<SelectInst>(I.getOperand(1));
  
  // div/rem X, (Cond ? 0 : Y) -> div/rem X, Y
  int NonNullOperand = -1;
  if (Constant *ST = dyn_cast<Constant>(SI->getOperand(1)))
    if (ST->isNullValue())
      NonNullOperand = 2;
  // div/rem X, (Cond ? Y : 0) -> div/rem X, Y
  if (Constant *ST = dyn_cast<Constant>(SI->getOperand(2)))
    if (ST->isNullValue())
      NonNullOperand = 1;
  
  if (NonNullOperand == -1)
    return false;
  
  Value *SelectCond = SI->getOperand(0);
  
  // Change the div/rem to use 'Y' instead of the select.
  I.setOperand(1, SI->getOperand(NonNullOperand));
  
  // Okay, we know we replace the operand of the div/rem with 'Y' with no
  // problem.  However, the select, or the condition of the select may have
  // multiple uses.  Based on our knowledge that the operand must be non-zero,
  // propagate the known value for the select into other uses of it, and
  // propagate a known value of the condition into its other users.
  
  // If the select and condition only have a single use, don't bother with this,
  // early exit.
  if (SI->use_empty() && SelectCond->hasOneUse())
    return true;
  
  // Scan the current block backward, looking for other uses of SI.
  BasicBlock::iterator BBI = &I, BBFront = I.getParent()->begin();
  
  while (BBI != BBFront) {
    --BBI;
    // If we found a call to a function, we can't assume it will return, so
    // information from below it cannot be propagated above it.
    if (isa<CallInst>(BBI) && !isa<IntrinsicInst>(BBI))
      break;
    
    // Replace uses of the select or its condition with the known values.
    for (Instruction::op_iterator I = BBI->op_begin(), E = BBI->op_end();
         I != E; ++I) {
      if (*I == SI) {
        *I = SI->getOperand(NonNullOperand);
        Worklist.Add(BBI);
      } else if (*I == SelectCond) {
        *I = NonNullOperand == 1 ? ConstantInt::getTrue(BBI->getContext()) :
                                   ConstantInt::getFalse(BBI->getContext());
        Worklist.Add(BBI);
      }
    }
    
    // If we past the instruction, quit looking for it.
    if (&*BBI == SI)
      SI = 0;
    if (&*BBI == SelectCond)
      SelectCond = 0;
    
    // If we ran out of things to eliminate, break out of the loop.
    if (SelectCond == 0 && SI == 0)
      break;
    
  }
  return true;
}

/// GetShiftedValue - When CanEvaluateShifted returned true for an expression,
/// this value inserts the new computation that produces the shifted value.
static Value *GetShiftedValue(Value *V, unsigned NumBits, bool isLeftShift,
                              InstCombiner &IC) {
  // We can always evaluate constants shifted.
  if (Constant *C = dyn_cast<Constant>(V)) {
    if (isLeftShift)
      V = IC.Builder->CreateShl(C, NumBits);
    else
      V = IC.Builder->CreateLShr(C, NumBits);
    // If we got a constantexpr back, try to simplify it with TD info.
    if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
      V = ConstantFoldConstantExpression(CE, IC.getDataLayout(),
                                         IC.getTargetLibraryInfo());
    return V;
  }

  Instruction *I = cast<Instruction>(V);
  IC.Worklist.Add(I);

  switch (I->getOpcode()) {
  default: llvm_unreachable("Inconsistency with CanEvaluateShifted");
  case Instruction::And:
  case Instruction::Or:
  case Instruction::Xor:
    // Bitwise operators can all arbitrarily be arbitrarily evaluated shifted.
    I->setOperand(0, GetShiftedValue(I->getOperand(0), NumBits,isLeftShift,IC));
    I->setOperand(1, GetShiftedValue(I->getOperand(1), NumBits,isLeftShift,IC));
    return I;

  case Instruction::Shl: {
    BinaryOperator *BO = cast<BinaryOperator>(I);
    unsigned TypeWidth = BO->getType()->getScalarSizeInBits();

    // We only accept shifts-by-a-constant in CanEvaluateShifted.
    ConstantInt *CI = cast<ConstantInt>(BO->getOperand(1));

    // We can always fold shl(c1)+shl(c2) -> shl(c1+c2).
    if (isLeftShift) {
      // If this is oversized composite shift, then unsigned shifts get 0.
      unsigned NewShAmt = NumBits+CI->getZExtValue();
      if (NewShAmt >= TypeWidth)
        return Constant::getNullValue(I->getType());

      BO->setOperand(1, ConstantInt::get(BO->getType(), NewShAmt));
      BO->setHasNoUnsignedWrap(false);
      BO->setHasNoSignedWrap(false);
      return I;
    }

    // We turn shl(c)+lshr(c) -> and(c2) if the input doesn't already have
    // zeros.
    if (CI->getValue() == NumBits) {
      APInt Mask(APInt::getLowBitsSet(TypeWidth, TypeWidth - NumBits));
      V = IC.Builder->CreateAnd(BO->getOperand(0),
                                ConstantInt::get(BO->getContext(), Mask));
      if (Instruction *VI = dyn_cast<Instruction>(V)) {
        VI->moveBefore(BO);
        VI->takeName(BO);
      }
      return V;
    }

    // We turn shl(c1)+shr(c2) -> shl(c3)+and(c4), but only when we know that
    // the and won't be needed.
    assert(CI->getZExtValue() > NumBits);
    BO->setOperand(1, ConstantInt::get(BO->getType(),
                                       CI->getZExtValue() - NumBits));
    BO->setHasNoUnsignedWrap(false);
    BO->setHasNoSignedWrap(false);
    return BO;
  }
  case Instruction::LShr: {
    BinaryOperator *BO = cast<BinaryOperator>(I);
    unsigned TypeWidth = BO->getType()->getScalarSizeInBits();
    // We only accept shifts-by-a-constant in CanEvaluateShifted.
    ConstantInt *CI = cast<ConstantInt>(BO->getOperand(1));

    // We can always fold lshr(c1)+lshr(c2) -> lshr(c1+c2).
    if (!isLeftShift) {
      // If this is oversized composite shift, then unsigned shifts get 0.
      unsigned NewShAmt = NumBits+CI->getZExtValue();
      if (NewShAmt >= TypeWidth)
        return Constant::getNullValue(BO->getType());

      BO->setOperand(1, ConstantInt::get(BO->getType(), NewShAmt));
      BO->setIsExact(false);
      return I;
    }

    // We turn lshr(c)+shl(c) -> and(c2) if the input doesn't already have
    // zeros.
    if (CI->getValue() == NumBits) {
      APInt Mask(APInt::getHighBitsSet(TypeWidth, TypeWidth - NumBits));
      V = IC.Builder->CreateAnd(I->getOperand(0),
                                ConstantInt::get(BO->getContext(), Mask));
      if (Instruction *VI = dyn_cast<Instruction>(V)) {
        VI->moveBefore(I);
        VI->takeName(I);
      }
//.........这里部分代码省略.........

/*
BalanceTree(root I)
  worklist: set
  leaves: vector
  mark I visited
  Push(worklist, Ra. Rb)
  // find all the leaves of the tree rooted at I
  while worklist not empty
    // look backwards following def-use from use
    T = ’R1 <- op1, Ra1, Rb1’ = Def(Pop(worklist))
    if T is a root
      // balance computes weight in this case
      if T not visited
         BalanceTree(T)
      SortedInsert(leaves, T, Weight(T))
    else if op(T) == op(I)
      // add uses to worklist
      Push(worklist, Ra1, Rb1)
*/
BinaryOperator* balanceTree(BinaryOperator* root, std::map<Instruction*,bool>& visitMap, std::vector<BinaryOperator*>& roots)
{
  assert(root);
  if(visitMap[root])
    return NULL;
  std::list<Value*> worklist;
  std::set<std::pair<int,Value*>,weight_less_than> leaves;
  visitMap[root] = true;
  worklist.push_back( root->getOperand(0) );
  worklist.push_back( root->getOperand(1) );
  while( !worklist.empty() )
  {
    Value* v = worklist.front();
    worklist.pop_front();
    assert(v);
    BinaryOperator* T = dynamic_cast<BinaryOperator*>(v);
    if( T and std::find(roots.begin(), roots.end(), T) != roots.end() ) // T is a binary operator that exists in the root list
    {
      if( !visitMap[T] ) //if we havent visited it, replace it with its balanced version
      {
        T = balanceTree(T, visitMap, roots);
      }
      if( !T )
      {
        INTERNAL_ERROR("balanceTree(" << *root << ") failed while attempting to balance leaf node " << *v << "; balance returned NULL!\n");
      }
      assert( T and "Balancing operation that was a root resulted in NULL being returned from balance function!" );
      leaves.insert(std::pair<int,Instruction*>(calculateWeight(T, roots), T));
    }
    else if( T and !isDifferentOperation(T, root) ) //if T isnt a root, and isnt a different operation than our root, we need to process it
    {
      worklist.push_back( T->getOperand(0) );
      worklist.push_back( T->getOperand(1) );
      //remove all of the signed, name, and size call uses
      for(Value::use_iterator UI = T->use_begin(); UI != T->use_end();)
      {
        CallInst* CI = dynamic_cast<CallInst*>(*UI);
        if( isROCCCFunctionCall(CI, ROCCCNames::VariableName) or
            isROCCCFunctionCall(CI, ROCCCNames::VariableSize) or
            isROCCCFunctionCall(CI, ROCCCNames::VariableSigned) )
        {
          CI->eraseFromParent();
          UI = T->use_begin();
        }
        else
          ++UI;
      }
    }
    else //T isnt a BinaryOperator, or isn't a root, or is a different operation than our root - just add it as a single leaf
    {
      leaves.insert(std::pair<int,Value*>(1, v));
    }
  }
  /*
  // construct a balanced tree from leaves
  while size(leaves) > 1
    Ra1 = Dequeue(leaves)
    Rb1 = Dequeue(leaves)
    T = ’R1 <- op1, Ra1, Rb1’
    insert T before I
    Weight(R1) = Weight(Ra1) + Weight(Rb1)
    SortedInsert(leaves, R1, Weight(R1))
  */
  while( leaves.size() > 1 )
  {
    std::pair<int,Value*> Ra1 = *leaves.begin();
    leaves.erase(leaves.begin());
    std::pair<int,Value*> Rb1 = *leaves.begin();
    leaves.erase(leaves.begin());
    int weight = Ra1.first + Rb1.first;
    //workaround to create a binary instruction with different operand types; create with undefs, then replace
    BinaryOperator* T = BinaryOperator::create(root->getOpcode(), UndefValue::get(root->getType()), UndefValue::get(root->getType()), "tmp", root);
    T->setOperand(0, Ra1.second);
    T->setOperand(1, Rb1.second);
    setSizeInBits(T, getSizeInBits(root));
    setValueSigned(T, isValueSigned(root));
    leaves.insert(std::pair<int,Value*>(weight, T));
  }
  BinaryOperator* last_inserted = NULL;
  if(leaves.begin() != leaves.end())
    last_inserted = dynamic_cast<BinaryOperator*>(leaves.begin()->second);
//.........这里部分代码省略.........