private void SplitAndSpillOverlappingInterval(
AllocationContext context,
LiveInterval current,
LiveInterval interval)
{
// If there's a next use after the start of the current interval,
// we need to split the spilled interval twice, and re-insert it
// on the "pending" list to ensure that it will get a new register
// on that use position.
int nextUse = interval.NextUseAfter(current.GetStart());
LiveInterval splitChild;
if (interval.GetStart() < current.GetStart())
{
splitChild = interval.Split(current.GetStart());
}
else
{
splitChild = interval;
}
if (nextUse != -1)
{
Debug.Assert(nextUse > current.GetStart(), "Trying to spill a interval currently being used.");
if (nextUse > splitChild.GetStart())
{
LiveInterval right = splitChild.Split(nextUse);
Spill(context, splitChild);
splitChild = right;
}
InsertInterval(splitChild);
}
else
{
Spill(context, splitChild);
}
}
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);
}
}
private bool TryAllocateRegWithoutSpill(AllocationContext context, LiveInterval current, int cIndex)
{
RegisterType regType = current.Local.Type.ToRegisterType();
int availableRegisters = context.Masks.GetAvailableRegisters(regType);
int[] freePositions = new int[RegistersCount];
for (int index = 0; index < RegistersCount; index++)
{
if ((availableRegisters & (1 << index)) != 0)
{
freePositions[index] = int.MaxValue;
}
}
foreach (int iIndex in context.Active)
{
LiveInterval interval = _intervals[iIndex];
if (interval.Register.Type == regType)
{
freePositions[interval.Register.Index] = 0;
}
}
foreach (int iIndex in context.Inactive)
{
LiveInterval interval = _intervals[iIndex];
if (interval.Register.Type == regType)
{
int overlapPosition = interval.GetOverlapPosition(current);
if (overlapPosition != LiveInterval.NotFound && freePositions[interval.Register.Index] > overlapPosition)
{
freePositions[interval.Register.Index] = overlapPosition;
}
}
}
int selectedReg = GetHighestValueIndex(freePositions);
int selectedNextUse = freePositions[selectedReg];
// Intervals starts and ends at odd positions, unless they span an entire
// block, in this case they will have ranges at a even position.
// When a interval is loaded from the stack to a register, we can only
// do the split at a odd position, because otherwise the split interval
// that is inserted on the list to be processed may clobber a register
// used by the instruction at the same position as the split.
// The problem only happens when a interval ends exactly at this instruction,
// because otherwise they would interfere, and the register wouldn't be selected.
// When the interval is aligned and the above happens, there's no problem as
// the instruction that is actually with the last use is the one
// before that position.
selectedNextUse &= ~InstructionGapMask;
if (selectedNextUse <= current.GetStart())
{
return(false);
}
else if (selectedNextUse < current.GetEnd())
{
Debug.Assert(selectedNextUse > current.GetStart(), "Trying to split interval at the start.");
LiveInterval splitChild = current.Split(selectedNextUse);
if (splitChild.UsesCount != 0)
{
Debug.Assert(splitChild.GetStart() > current.GetStart(), "Split interval has an invalid start position.");
InsertInterval(splitChild);
}
else
{
Spill(context, splitChild);
}
}
current.Register = new Register(selectedReg, regType);
if (regType == RegisterType.Integer)
{
context.IntUsedRegisters |= 1 << selectedReg;
}
else /* if (regType == RegisterType.Vector) */
{
context.VecUsedRegisters |= 1 << selectedReg;
}
context.Active.Set(cIndex);
return(true);
}