private void SplitAndSpillOverlappingIntervals(AllocationContext context, LiveInterval current)
{
foreach (int iIndex in context.Active)
{
LiveInterval interval = _intervals[iIndex];
if (!interval.IsFixed && interval.Register == current.Register)
{
SplitAndSpillOverlappingInterval(context, current, interval);
context.Active.Clear(iIndex);
}
}
foreach (int iIndex in context.Inactive)
{
LiveInterval interval = _intervals[iIndex];
if (!interval.IsFixed && interval.Register == current.Register && interval.Overlaps(current))
{
SplitAndSpillOverlappingInterval(context, current, interval);
context.Inactive.Clear(iIndex);
}
}
}
private void AllocateInterval(AllocationContext context, LiveInterval current, int cIndex)
{
// Check active intervals that already ended.
foreach (int iIndex in context.Active)
{
LiveInterval interval = _intervals[iIndex];
if (interval.GetEnd() < current.GetStart())
{
context.Active.Clear(iIndex);
}
else if (!interval.Overlaps(current.GetStart()))
{
context.MoveActiveToInactive(iIndex);
}
}
// Check inactive intervals that already ended or were reactivated.
foreach (int iIndex in context.Inactive)
{
LiveInterval interval = _intervals[iIndex];
if (interval.GetEnd() < current.GetStart())
{
context.Inactive.Clear(iIndex);
}
else if (interval.Overlaps(current.GetStart()))
{
context.MoveInactiveToActive(iIndex);
}
}
if (!TryAllocateRegWithoutSpill(context, current, cIndex))
{
AllocateRegWithSpill(context, current, cIndex);
}
}
private void AllocateRegWithSpill(AllocationContext context, LiveInterval current, int cIndex)
{
RegisterType regType = current.Local.Type.ToRegisterType();
int availableRegisters = context.Masks.GetAvailableRegisters(regType);
int[] usePositions = new int[RegistersCount];
int[] blockedPositions = new int[RegistersCount];
for (int index = 0; index < RegistersCount; index++)
{
if ((availableRegisters & (1 << index)) != 0)
{
usePositions[index] = int.MaxValue;
blockedPositions[index] = int.MaxValue;
}
}
void SetUsePosition(int index, int position)
{
usePositions[index] = Math.Min(usePositions[index], position);
}
void SetBlockedPosition(int index, int position)
{
blockedPositions[index] = Math.Min(blockedPositions[index], position);
SetUsePosition(index, position);
}
foreach (int iIndex in context.Active)
{
LiveInterval interval = _intervals[iIndex];
if (!interval.IsFixed && interval.Register.Type == regType)
{
int nextUse = interval.NextUseAfter(current.GetStart());
if (nextUse != -1)
{
SetUsePosition(interval.Register.Index, nextUse);
}
}
}
foreach (int iIndex in context.Inactive)
{
LiveInterval interval = _intervals[iIndex];
if (!interval.IsFixed && interval.Register.Type == regType && interval.Overlaps(current))
{
int nextUse = interval.NextUseAfter(current.GetStart());
if (nextUse != -1)
{
SetUsePosition(interval.Register.Index, nextUse);
}
}
}
foreach (int iIndex in context.Active)
{
LiveInterval interval = _intervals[iIndex];
if (interval.IsFixed && interval.Register.Type == regType)
{
SetBlockedPosition(interval.Register.Index, 0);
}
}
foreach (int iIndex in context.Inactive)
{
LiveInterval interval = _intervals[iIndex];
if (interval.IsFixed && interval.Register.Type == regType)
{
int overlapPosition = interval.GetOverlapPosition(current);
if (overlapPosition != LiveInterval.NotFound)
{
SetBlockedPosition(interval.Register.Index, overlapPosition);
}
}
}
int selectedReg = GetHighestValueIndex(usePositions);
int currentFirstUse = current.FirstUse();
Debug.Assert(currentFirstUse >= 0, "Current interval has no uses.");
if (usePositions[selectedReg] < currentFirstUse)
{
// All intervals on inactive and active are being used before current,
// so spill the current interval.
Debug.Assert(currentFirstUse > current.GetStart(), "Trying to spill a interval currently being used.");
LiveInterval splitChild = current.Split(currentFirstUse);
Debug.Assert(splitChild.GetStart() > current.GetStart(), "Split interval has an invalid start position.");
InsertInterval(splitChild);
Spill(context, current);
}
else if (blockedPositions[selectedReg] > current.GetEnd())
{
// Spill made the register available for the entire current lifetime,
// so we only need to split the intervals using the selected register.
current.Register = new Register(selectedReg, regType);
SplitAndSpillOverlappingIntervals(context, current);
context.Active.Set(cIndex);
}
else
{
// There are conflicts even after spill due to the use of fixed registers
// that can't be spilled, so we need to also split current at the point of
// the first fixed register use.
current.Register = new Register(selectedReg, regType);
int splitPosition = blockedPositions[selectedReg] & ~InstructionGapMask;
Debug.Assert(splitPosition > current.GetStart(), "Trying to split a interval at a invalid position.");
LiveInterval splitChild = current.Split(splitPosition);
if (splitChild.UsesCount != 0)
{
Debug.Assert(splitChild.GetStart() > current.GetStart(), "Split interval has an invalid start position.");
InsertInterval(splitChild);
}
else
{
Spill(context, splitChild);
}
SplitAndSpillOverlappingIntervals(context, current);
context.Active.Set(cIndex);
}
}