C++ (Cpp) BinaryOperator::clearSubclassOptionalData示例

示例#1

// 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);
}