private void DeleteRegisterToRegisterDelay(DelayGraphVertex from, DelayGraphVertex to)
{
var key = Tuple.Create(from, to);
if (!RegisterToRegisterDelays.Remove(key))
{
throw new Exception("this should not happen");
}
}
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 int GetRegisterToRegisterDelay(DelayGraphVertex from, DelayGraphVertex to)
{
var key = Tuple.Create(from, to);
int delay;
if (!RegisterToRegisterDelays.TryGetValue(key, out delay))
{
throw new Exception("This is not supposed to ever happen");
}
return(delay);
}
private void UpdateRegisterRegisterDelay(DelayGraphVertex from, DelayGraphVertex to, int delay)
{
var key = Tuple.Create(from, to);
int origDelay;
if (!RegisterToRegisterDelays.TryGetValue(key, out origDelay) ||
origDelay < delay)
{
RegisterToRegisterDelays[key] = delay;
}
}
private void UpdateFanInRegisters(DelayGraphVertex vertex, int outgoingDelay, HashSet <DelayGraphVertex> faninRegisters, HashSet <DelayGraphVertex> fanoutRegisters)
{
// update fanin and fanout registers maps and delays now that vertex is NOT a register anymore
if (faninRegisters == null)
{
return;
}
// update each upstream register vertex
foreach (var faninReg in faninRegisters)
{
int faninDelay = GetRegisterToRegisterDelay(@from: faninReg, to: vertex);
int totalDelay = faninDelay + outgoingDelay;
// update faninReg's output delay to be max of total delay and original delay
int origDelay;
if (!OutputDelayMap.TryGetValue(faninReg, out origDelay) ||
origDelay < totalDelay)
{
OutputDelayMap[faninReg] = totalDelay;
}
// remove vertex from reg's fanout registers
HashSet <DelayGraphVertex> origFanoutRegs;
if (FanoutRegistersMap.TryGetValue(faninReg, out origFanoutRegs))
{
origFanoutRegs.Remove(vertex);
}
// add vertex's fanout registers to reg's fanout registers
if (fanoutRegisters != null)
{
if (origFanoutRegs == null)
{
origFanoutRegs = new HashSet <DelayGraphVertex>(fanoutRegisters);
FanoutRegistersMap[faninReg] = origFanoutRegs;
}
else
{
foreach (var next in fanoutRegisters)
{
origFanoutRegs.Add(next);
}
}
// update faninReg -> fanoutRegister with faninDelay + v->fanoutRegister delay
foreach (var fanoutReg in fanoutRegisters)
{
int fanoutDelay = GetRegisterToRegisterDelay(@from: vertex, to: fanoutReg);
UpdateRegisterRegisterDelay(@from: faninReg, to: fanoutReg, delay: faninDelay + fanoutDelay);
}
}
}
}
/// <summary>
/// clean up data structures when vertex is no longer a register
/// </summary>
/// <param name="vertex"></param>
/// <param name="faninRegisters"></param>
/// <param name="fanoutRegisters"></param>
private void CleanFromRegisterToRegisterMap(DelayGraphVertex vertex, HashSet <DelayGraphVertex> faninRegisters, HashSet <DelayGraphVertex> fanoutRegisters)
{
if (faninRegisters != null)
{
foreach (var faninReg in faninRegisters)
{
DeleteRegisterToRegisterDelay(@from: faninReg, to: vertex);
}
}
if (fanoutRegisters != null)
{
foreach (var fanoutReg in fanoutRegisters)
{
DeleteRegisterToRegisterDelay(@from: vertex, to: fanoutReg);
}
}
FaninRegistersMap.Remove(vertex);
FanoutRegistersMap.Remove(vertex);
}
