private bool IsSafeToDeRegister(DelayGraphVertex vertex)
{
if (vertex.IsRegistered)
{
return(false);
}
// get incoming delay
int incomingDelay;
if (!InputDelayMap.TryGetValue(vertex, out incomingDelay))
{
incomingDelay = 0;
}
// get outgoing delay
int outgoingDelay;
if (!OutputDelayMap.TryGetValue(vertex, out outgoingDelay))
{
outgoingDelay = 0;
}
int totalDelay = incomingDelay + outgoingDelay;
if (totalDelay > TargetPeriod)
{
return(false);
}
// double check for cycles if vertex register is removed
HashSet <DelayGraphVertex> faninRegisters;
if (FaninRegistersMap.TryGetValue(vertex, out faninRegisters))
{
if (faninRegisters.Contains(vertex))
{
return(false); // vertex is its own fanin register - cannot remove register or there would be a cycle
}
}
HashSet <DelayGraphVertex> fanoutRegisters;
if (FanoutRegistersMap.TryGetValue(vertex, out fanoutRegisters))
{
if (fanoutRegisters.Contains(vertex))
{
return(false); // vertex is its own fanout register - cannot remove register or there would be a cycle
}
}
UpdateFanInRegisters(vertex, outgoingDelay, faninRegisters, fanoutRegisters);
UpdateFanOutRegisters(vertex, incomingDelay, faninRegisters, fanoutRegisters);
CleanFromRegisterToRegisterMap(vertex, faninRegisters, fanoutRegisters);
return(true);
}
private void UpdateFanOutRegisters(DelayGraphVertex vertex, int incomingDelay, HashSet <DelayGraphVertex> faninRegisters, HashSet <DelayGraphVertex> fanoutRegisters)
{
// update fanin and fanout registers maps and delays now that vertex is NOT a register anymore
if (fanoutRegisters == null)
{
return;
}
// update each downstream register vertex
foreach (var fanoutReg in fanoutRegisters)
{
int fanoutDelay = GetRegisterToRegisterDelay(@from: vertex, to: fanoutReg);
int totalDelay = incomingDelay + fanoutDelay;
// update reg's input delay to be max of total delay and original delay
int origDelay;
if (!InputDelayMap.TryGetValue(fanoutReg, out origDelay) ||
origDelay < totalDelay)
{
InputDelayMap[fanoutReg] = totalDelay;
}
// remove vertex from fanout reg's fanin registers
HashSet <DelayGraphVertex> origFaninRegs;
if (FaninRegistersMap.TryGetValue(fanoutReg, out origFaninRegs))
{
origFaninRegs.Remove(vertex);
}
// add vertex's fanin registers to reg's fanin registers
if (faninRegisters != null)
{
if (origFaninRegs == null)
{
origFaninRegs = new HashSet <DelayGraphVertex>(faninRegisters);
FaninRegistersMap[fanoutReg] = origFaninRegs;
}
else
{
foreach (var next in faninRegisters)
{
origFaninRegs.Add(next);
}
}
// update faninReg -> fanoutRegister with faninDelay + v->fanoutRegister delay
foreach (var faninReg in faninRegisters)
{
int faninDelay = GetRegisterToRegisterDelay(@from: faninReg, to: vertex);
UpdateRegisterRegisterDelay(@from: faninReg, to: fanoutReg, delay: faninDelay + fanoutDelay);
}
}
}
}
