/// <summary>
/// Selects an output register number, given an input register number
/// An improved implementation might be more picky about the selection, this one grabs the next available off a stack.
/// </summary>
/// <param name="nInputRegister"></param>
/// <param name="nInstruction"></param>
/// <returns></returns>
int GetOutputRegister(int nInputRegister, NaiveRegisterPacker narp)
{
// see if it's already transformed
int nOutputRegister = -1;
if (RegisterTransforms.TryGetValue(nInputRegister, out nOutputRegister))
{
return nOutputRegister;
}
Stack<int> Rejects = new Stack<int>();
do
{
// it's not.
if (AvailableRegisters.Count == 0)
{
throw new NotImplementedException("Out of registers!");
}
nOutputRegister = AvailableRegisters.Pop();
if (narp.AllowRegisterTransform(nInputRegister, nOutputRegister))
{
break;
}
Rejects.Push(nOutputRegister);
}
while (true);
while (Rejects.Count > 0)
{
AvailableRegisters.Push(Rejects.Peek());
Rejects.Pop();
}
UnavailableRegisters.Add(nOutputRegister, nInputRegister);
RegisterTransforms.Add(nInputRegister, nOutputRegister);
if (nOutputRegister >= NumOutputRegisters)
NumOutputRegisters = nOutputRegister + 1;
return nOutputRegister;
}
void PackRegisters(BasicBlock bb)
{
NaiveRegisterPacker nrp = new NaiveRegisterPacker(bb,this);
List<int> registerPastWrites = bb.GetRegisterPastWrites();
List<int> registerFutureReads = bb.GetRegisterFutureReads();
{
List<int> listReserved = new List<int>();
// listReserved is the intersection of RegisterPastWrites with RegisterReads OR RegisterFutureReads
foreach (int n in registerPastWrites)
{
if (bb.RegisterReads.Contains(n) || registerFutureReads.Contains(n))
listReserved.Add(n);
}
if (listReserved.Count>0)
nrp.HeadRegisters(listReserved, bb.Instructions);
}
nrp.ScanRanges(bb.Instructions);
{
List<int> listReserved = new List<int>();
// listReserved is the intersection of RegisterFutureReads with RegisterWrites OR RegisterPastWrites
foreach (int n in registerFutureReads)
{
if (bb.RegisterWrites.Contains(n) || registerPastWrites.Contains(n))
listReserved.Add(n);
}
if (listReserved.Count > 0)
nrp.TailRegisters(listReserved, bb.Instructions);
}
nrp.Condense(bb.Instructions);
}
