-/// hasRegisterUseBelow - Return true if the specified register is used after
-/// the current instruction and before it's next definition.
-bool LiveVariables::hasRegisterUseBelow(unsigned Reg,
- MachineBasicBlock::iterator I,
- MachineBasicBlock *MBB) {
- if (I == MBB->end())
- return false;
-
- // First find out if there are any uses / defs below.
- bool hasDistInfo = true;
- unsigned CurDist = DistanceMap[I];
- SmallVector<MachineInstr*, 4> Uses;
- SmallVector<MachineInstr*, 4> Defs;
- for (MachineRegisterInfo::reg_iterator RI = MRI->reg_begin(Reg),
- RE = MRI->reg_end(); RI != RE; ++RI) {
- MachineOperand &UDO = RI.getOperand();
- MachineInstr *UDMI = &*RI;
- if (UDMI->getParent() != MBB)
- continue;
- DenseMap<MachineInstr*, unsigned>::iterator DI = DistanceMap.find(UDMI);
- bool isBelow = false;
- if (DI == DistanceMap.end()) {
- // Must be below if it hasn't been assigned a distance yet.
- isBelow = true;
- hasDistInfo = false;
- } else if (DI->second > CurDist)
- isBelow = true;
- if (isBelow) {
- if (UDO.isUse())
- Uses.push_back(UDMI);
- if (UDO.isDef())
- Defs.push_back(UDMI);
- }
- }
-
- if (Uses.empty())
- // No uses below.
- return false;
- else if (!Uses.empty() && Defs.empty())
- // There are uses below but no defs below.
- return true;
- // There are both uses and defs below. We need to know which comes first.
- if (!hasDistInfo) {
- // Complete DistanceMap for this MBB. This information is computed only
- // once per MBB.
- ++I;
- ++CurDist;
- for (MachineBasicBlock::iterator E = MBB->end(); I != E; ++I, ++CurDist)
- DistanceMap.insert(std::make_pair(I, CurDist));
- }
-
- unsigned EarliestUse = DistanceMap[Uses[0]];
- for (unsigned i = 1, e = Uses.size(); i != e; ++i) {
- unsigned Dist = DistanceMap[Uses[i]];
- if (Dist < EarliestUse)
- EarliestUse = Dist;
- }
- for (unsigned i = 0, e = Defs.size(); i != e; ++i) {
- unsigned Dist = DistanceMap[Defs[i]];
- if (Dist < EarliestUse)
- // The register is defined before its first use below.
- return false;
- }
- return true;
-}
-