[LLVMdev] SU aliasing

[Sergei Larin]

Sorry if it is described somewhere, but is there any hidden danger in doing
the following during DAG lowering:

The problem is that at some point I seem to get stale data from
(MMOa->getValue()) which produces bogus alias result.
...and it seems that there should be a more elegant way to implement the
function...

Thanks.

bool SUsDoNotAliasEachOther (SUnit *SU1, SUnit *SU2, AliasAnalysis *AA) {
  if (!SU1 || !SU2)  return false;
  if (SU1->isInstr() || SU2->isInstr())  return false;
  SDNode *SDN1 = SU1->getNode();
  SDNode *SDN2 = SU2->getNode();

  if (!SDN1 || !SDN2)  return false;

  if (SDN1->isMachineOpcode() && SDN2->isMachineOpcode()) {
    MachineMemOperand *MMOa = NULL;
    MachineMemOperand *MMOb = NULL;
    const MachineSDNode *MNb = dyn_cast<MachineSDNode>(SDN2);
    const MachineSDNode *MNa = dyn_cast<MachineSDNode>(SDN1);
    // Check that they are LD/ST
    if (MNa) MMOa = !MNa->memoperands_empty() ?
                    (*MNa->memoperands_begin()) : NULL;
    if (MNb) MMOb = !MNb->memoperands_empty() ?
                    (*MNb->memoperands_begin()) : NULL;
    if (MMOa && MMOa->getValue() && MMOb && MMOb->getValue()) {

      if (!AA->alias (MMOa->getValue(), MMOa->getSize(),
                      MMOb->getValue(), MMOb->getSize())) {
        return true;
      }
    }
  }
  return false;
}

Sergei