Move solution and projects to src

1 files changed, 1101 insertions, 0 deletions

diff --git a/src/ARMeilleure/CodeGen/RegisterAllocators/LinearScanAllocator.cs b/src/ARMeilleure/CodeGen/RegisterAllocators/LinearScanAllocator.cs
new file mode 100644
index 00000000..d80157af
--- /dev/null
+++ b/src/ARMeilleure/CodeGen/RegisterAllocators/LinearScanAllocator.cs
@@ -0,0 +1,1101 @@
+using ARMeilleure.Common;
+using ARMeilleure.IntermediateRepresentation;
+using ARMeilleure.Translation;
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+using System.Numerics;
+
+namespace ARMeilleure.CodeGen.RegisterAllocators
+{
+    // Based on:
+    // "Linear Scan Register Allocation for the Java(tm) HotSpot Client Compiler".
+    // http://www.christianwimmer.at/Publications/Wimmer04a/Wimmer04a.pdf
+    class LinearScanAllocator : IRegisterAllocator
+    {
+        private const int InstructionGap     = 2;
+        private const int InstructionGapMask = InstructionGap - 1;
+
+        private HashSet<int> _blockEdges;
+        private LiveRange[] _blockRanges;
+        private BitMap[] _blockLiveIn;
+
+        private List<LiveInterval> _intervals;
+        private LiveInterval[] _parentIntervals;
+
+        private List<(IntrusiveList<Operation>, Operation)> _operationNodes;
+        private int _operationsCount;
+
+        private class AllocationContext
+        {
+            public RegisterMasks Masks { get; }
+
+            public StackAllocator StackAlloc { get; }
+
+            public BitMap Active   { get; }
+            public BitMap Inactive { get; }
+
+            public int IntUsedRegisters { get; set; }
+            public int VecUsedRegisters { get; set; }
+
+            private readonly int[] _intFreePositions;
+            private readonly int[] _vecFreePositions;
+            private readonly int _intFreePositionsCount;
+            private readonly int _vecFreePositionsCount;
+
+            public AllocationContext(StackAllocator stackAlloc, RegisterMasks masks, int intervalsCount)
+            {
+                StackAlloc = stackAlloc;
+                Masks      = masks;
+
+                Active   = new BitMap(Allocators.Default, intervalsCount);
+                Inactive = new BitMap(Allocators.Default, intervalsCount);
+
+                PopulateFreePositions(RegisterType.Integer, out _intFreePositions, out _intFreePositionsCount);
+                PopulateFreePositions(RegisterType.Vector, out _vecFreePositions, out _vecFreePositionsCount);
+
+                void PopulateFreePositions(RegisterType type, out int[] positions, out int count)
+                {
+                    positions = new int[masks.RegistersCount];
+                    count = BitOperations.PopCount((uint)masks.GetAvailableRegisters(type));
+
+                    int mask = masks.GetAvailableRegisters(type);
+
+                    for (int i = 0; i < positions.Length; i++)
+                    {
+                        if ((mask & (1 << i)) != 0)
+                        {
+                            positions[i] = int.MaxValue;
+                        }
+                    }
+                }
+            }
+
+            public void GetFreePositions(RegisterType type, in Span<int> positions, out int count)
+            {
+                if (type == RegisterType.Integer)
+                {
+                    _intFreePositions.CopyTo(positions);
+
+                    count = _intFreePositionsCount;
+                }
+                else
+                {
+                    Debug.Assert(type == RegisterType.Vector);
+
+                    _vecFreePositions.CopyTo(positions);
+
+                    count = _vecFreePositionsCount;
+                }
+            }
+
+            public void MoveActiveToInactive(int bit)
+            {
+                Move(Active, Inactive, bit);
+            }
+
+            public void MoveInactiveToActive(int bit)
+            {
+                Move(Inactive, Active, bit);
+            }
+
+            private static void Move(BitMap source, BitMap dest, int bit)
+            {
+                source.Clear(bit);
+
+                dest.Set(bit);
+            }
+        }
+
+        public AllocationResult RunPass(
+            ControlFlowGraph cfg,
+            StackAllocator stackAlloc,
+            RegisterMasks regMasks)
+        {
+            NumberLocals(cfg, regMasks.RegistersCount);
+
+            var context = new AllocationContext(stackAlloc, regMasks, _intervals.Count);
+
+            BuildIntervals(cfg, context);
+
+            for (int index = 0; index < _intervals.Count; index++)
+            {
+                LiveInterval current = _intervals[index];
+
+                if (current.IsEmpty)
+                {
+                    continue;
+                }
+
+                if (current.IsFixed)
+                {
+                    context.Active.Set(index);
+
+                    if (current.IsFixedAndUsed)
+                    {
+                        if (current.Register.Type == RegisterType.Integer)
+                        {
+                            context.IntUsedRegisters |= 1 << current.Register.Index;
+                        }
+                        else /* if (interval.Register.Type == RegisterType.Vector) */
+                        {
+                            context.VecUsedRegisters |= 1 << current.Register.Index;
+                        }
+                    }
+
+                    continue;
+                }
+
+                AllocateInterval(context, current, index, regMasks.RegistersCount);
+            }
+
+            for (int index = regMasks.RegistersCount * 2; index < _intervals.Count; index++)
+            {
+                if (!_intervals[index].IsSpilled)
+                {
+                    ReplaceLocalWithRegister(_intervals[index]);
+                }
+            }
+
+            InsertSplitCopies();
+            InsertSplitCopiesAtEdges(cfg);
+
+            return new AllocationResult(context.IntUsedRegisters, context.VecUsedRegisters, context.StackAlloc.TotalSize);
+        }
+
+        private void AllocateInterval(AllocationContext context, LiveInterval current, int cIndex, int registersCount)
+        {
+            // Check active intervals that already ended.
+            foreach (int iIndex in context.Active)
+            {
+                LiveInterval interval = _intervals[iIndex];
+
+                interval.Forward(current.GetStart());
+
+                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];
+
+                interval.Forward(current.GetStart());
+
+                if (interval.GetEnd() < current.GetStart())
+                {
+                    context.Inactive.Clear(iIndex);
+                }
+                else if (interval.Overlaps(current.GetStart()))
+                {
+                    context.MoveInactiveToActive(iIndex);
+                }
+            }
+
+            if (!TryAllocateRegWithoutSpill(context, current, cIndex, registersCount))
+            {
+                AllocateRegWithSpill(context, current, cIndex, registersCount);
+            }
+        }
+
+        private bool TryAllocateRegWithoutSpill(AllocationContext context, LiveInterval current, int cIndex, int registersCount)
+        {
+            RegisterType regType = current.Local.Type.ToRegisterType();
+
+            Span<int> freePositions = stackalloc int[registersCount];
+
+            context.GetFreePositions(regType, freePositions, out int freePositionsCount);
+
+            foreach (int iIndex in context.Active)
+            {
+                LiveInterval interval = _intervals[iIndex];
+                Register reg = interval.Register;
+
+                if (reg.Type == regType)
+                {
+                    freePositions[reg.Index] = 0;
+                    freePositionsCount--;
+                }
+            }
+
+            // If all registers are already active, return early. No point in inspecting the inactive set to look for
+            // holes.
+            if (freePositionsCount == 0)
+            {
+                return false;
+            }
+
+            foreach (int iIndex in context.Inactive)
+            {
+                LiveInterval interval = _intervals[iIndex];
+                Register reg = interval.Register;
+
+                ref int freePosition = ref freePositions[reg.Index];
+
+                if (reg.Type == regType && freePosition != 0)
+                {
+                    int overlapPosition = interval.GetOverlapPosition(current);
+
+                    if (overlapPosition != LiveInterval.NotFound && freePosition > overlapPosition)
+                    {
+                        freePosition = 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())
+            {
+                LiveInterval splitChild = current.Split(selectedNextUse);
+
+                if (splitChild.UsesCount != 0)
+                {
+                    Debug.Assert(splitChild.GetStart() > current.GetStart(), "Split interval has an invalid start position.");
+
+                    InsertInterval(splitChild, registersCount);
+                }
+                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;
+        }
+
+        private void AllocateRegWithSpill(AllocationContext context, LiveInterval current, int cIndex, int registersCount)
+        {
+            RegisterType regType = current.Local.Type.ToRegisterType();
+
+            Span<int> usePositions = stackalloc int[registersCount];
+            Span<int> blockedPositions = stackalloc int[registersCount];
+
+            context.GetFreePositions(regType, usePositions, out _);
+            context.GetFreePositions(regType, blockedPositions, out _);
+
+            foreach (int iIndex in context.Active)
+            {
+                LiveInterval interval = _intervals[iIndex];
+                Register reg = interval.Register;
+
+                if (reg.Type == regType)
+                {
+                    ref int usePosition = ref usePositions[reg.Index];
+                    ref int blockedPosition = ref blockedPositions[reg.Index];
+
+                    if (interval.IsFixed)
+                    {
+                        usePosition = 0;
+                        blockedPosition = 0;
+                    }
+                    else
+                    {
+                        int nextUse = interval.NextUseAfter(current.GetStart());
+
+                        if (nextUse != LiveInterval.NotFound && usePosition > nextUse)
+                        {
+                            usePosition = nextUse;
+                        }
+                    }
+                }
+            }
+
+            foreach (int iIndex in context.Inactive)
+            {
+                LiveInterval interval = _intervals[iIndex];
+                Register reg = interval.Register;
+
+                if (reg.Type == regType)
+                {
+                    ref int usePosition = ref usePositions[reg.Index];
+                    ref int blockedPosition = ref blockedPositions[reg.Index];
+
+                    if (interval.IsFixed)
+                    {
+                        int overlapPosition = interval.GetOverlapPosition(current);
+
+                        if (overlapPosition != LiveInterval.NotFound)
+                        {
+                            blockedPosition = Math.Min(blockedPosition, overlapPosition);
+                            usePosition = Math.Min(usePosition, overlapPosition);
+                        }
+                    }
+                    else if (interval.Overlaps(current))
+                    {
+                        int nextUse = interval.NextUseAfter(current.GetStart());
+
+                        if (nextUse != LiveInterval.NotFound && usePosition > nextUse)
+                        {
+                            usePosition = nextUse;
+                        }
+                    }
+                }
+            }
+
+            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, registersCount);
+
+                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, registersCount);
+
+                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, registersCount);
+                }
+                else
+                {
+                    Spill(context, splitChild);
+                }
+
+                SplitAndSpillOverlappingIntervals(context, current, registersCount);
+
+                context.Active.Set(cIndex);
+            }
+        }
+
+        private static int GetHighestValueIndex(Span<int> span)
+        {
+            int highest = int.MinValue;
+
+            int selected = 0;
+
+            for (int index = 0; index < span.Length; index++)
+            {
+                int current = span[index];
+
+                if (highest < current)
+                {
+                    highest  = current;
+                    selected = index;
+
+                    if (current == int.MaxValue)
+                    {
+                        break;
+                    }
+                }
+            }
+
+            return selected;
+        }
+
+        private void SplitAndSpillOverlappingIntervals(AllocationContext context, LiveInterval current, int registersCount)
+        {
+            foreach (int iIndex in context.Active)
+            {
+                LiveInterval interval = _intervals[iIndex];
+
+                if (!interval.IsFixed && interval.Register == current.Register)
+                {
+                    SplitAndSpillOverlappingInterval(context, current, interval, registersCount);
+
+                    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, registersCount);
+
+                    context.Inactive.Clear(iIndex);
+                }
+            }
+        }
+
+        private void SplitAndSpillOverlappingInterval(
+            AllocationContext context,
+            LiveInterval      current,
+            LiveInterval      interval,
+            int               registersCount)
+        {
+            // 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, registersCount);
+            }
+            else
+            {
+                Spill(context, splitChild);
+            }
+        }
+
+        private void InsertInterval(LiveInterval interval, int registersCount)
+        {
+            Debug.Assert(interval.UsesCount != 0, "Trying to insert a interval without uses.");
+            Debug.Assert(!interval.IsEmpty,       "Trying to insert a empty interval.");
+            Debug.Assert(!interval.IsSpilled,     "Trying to insert a spilled interval.");
+
+            int startIndex = registersCount * 2;
+
+            int insertIndex = _intervals.BinarySearch(startIndex, _intervals.Count - startIndex, interval, null);
+
+            if (insertIndex < 0)
+            {
+                insertIndex = ~insertIndex;
+            }
+
+            _intervals.Insert(insertIndex, interval);
+        }
+
+        private void Spill(AllocationContext context, LiveInterval interval)
+        {
+            Debug.Assert(!interval.IsFixed,       "Trying to spill a fixed interval.");
+            Debug.Assert(interval.UsesCount == 0, "Trying to spill a interval with uses.");
+
+            // We first check if any of the siblings were spilled, if so we can reuse
+            // the stack offset. Otherwise, we allocate a new space on the stack.
+            // This prevents stack-to-stack copies being necessary for a split interval.
+            if (!interval.TrySpillWithSiblingOffset())
+            {
+                interval.Spill(context.StackAlloc.Allocate(interval.Local.Type));
+            }
+        }
+
+        private void InsertSplitCopies()
+        {
+            Dictionary<int, CopyResolver> copyResolvers = new Dictionary<int, CopyResolver>();
+
+            CopyResolver GetCopyResolver(int position)
+            {
+                if (!copyResolvers.TryGetValue(position, out CopyResolver copyResolver))
+                {
+                    copyResolver = new CopyResolver();
+
+                    copyResolvers.Add(position, copyResolver);
+                }
+
+                return copyResolver;
+            }
+
+            foreach (LiveInterval interval in _intervals.Where(x => x.IsSplit))
+            {
+                LiveInterval previous = interval;
+
+                foreach (LiveInterval splitChild in interval.SplitChildren())
+                {
+                    int splitPosition = splitChild.GetStart();
+
+                    if (!_blockEdges.Contains(splitPosition) && previous.GetEnd() == splitPosition)
+                    {
+                        GetCopyResolver(splitPosition).AddSplit(previous, splitChild);
+                    }
+
+                    previous = splitChild;
+                }
+            }
+
+            foreach (KeyValuePair<int, CopyResolver> kv in copyResolvers)
+            {
+                CopyResolver copyResolver = kv.Value;
+
+                if (!copyResolver.HasCopy)
+                {
+                    continue;
+                }
+
+                int splitPosition = kv.Key;
+
+                (IntrusiveList<Operation> nodes, Operation node) = GetOperationNode(splitPosition);
+
+                Operation[] sequence = copyResolver.Sequence();
+
+                nodes.AddBefore(node, sequence[0]);
+
+                node = sequence[0];
+
+                for (int index = 1; index < sequence.Length; index++)
+                {
+                    nodes.AddAfter(node, sequence[index]);
+
+                    node = sequence[index];
+                }
+            }
+        }
+
+        private void InsertSplitCopiesAtEdges(ControlFlowGraph cfg)
+        {
+            int blocksCount = cfg.Blocks.Count;
+
+            bool IsSplitEdgeBlock(BasicBlock block)
+            {
+                return block.Index >= blocksCount;
+            }
+
+            // Reset iterators to beginning because GetSplitChild depends on the state of the iterator.
+            foreach (LiveInterval interval in _intervals)
+            {
+                interval.Reset();
+            }
+
+            for (BasicBlock block = cfg.Blocks.First; block != null; block = block.ListNext)
+            {
+                if (IsSplitEdgeBlock(block))
+                {
+                    continue;
+                }
+
+                bool hasSingleOrNoSuccessor = block.SuccessorsCount <= 1;
+
+                for (int i = 0; i < block.SuccessorsCount; i++)
+                {
+                    BasicBlock successor = block.GetSuccessor(i);
+
+                    int succIndex = successor.Index;
+
+                    // If the current node is a split node, then the actual successor node
+                    // (the successor before the split) should be right after it.
+                    if (IsSplitEdgeBlock(successor))
+                    {
+                        succIndex = successor.GetSuccessor(0).Index;
+                    }
+
+                    CopyResolver copyResolver = null;
+
+                    foreach (int iIndex in _blockLiveIn[succIndex])
+                    {
+                        LiveInterval interval = _parentIntervals[iIndex];
+
+                        if (!interval.IsSplit)
+                        {
+                            continue;
+                        }
+
+                        int lEnd   = _blockRanges[block.Index].End - 1;
+                        int rStart = _blockRanges[succIndex].Start;
+
+                        LiveInterval left  = interval.GetSplitChild(lEnd);
+                        LiveInterval right = interval.GetSplitChild(rStart);
+
+                        if (left != default && right != default && left != right)
+                        {
+                            if (copyResolver == null)
+                            {
+                                copyResolver = new CopyResolver();
+                            }
+
+                            copyResolver.AddSplit(left, right);
+                        }
+                    }
+
+                    if (copyResolver == null || !copyResolver.HasCopy)
+                    {
+                        continue;
+                    }
+
+                    Operation[] sequence = copyResolver.Sequence();
+
+                    if (hasSingleOrNoSuccessor)
+                    {
+                        foreach (Operation operation in sequence)
+                        {
+                            block.Append(operation);
+                        }
+                    }
+                    else if (successor.Predecessors.Count == 1)
+                    {
+                        successor.Operations.AddFirst(sequence[0]);
+
+                        Operation prependNode = sequence[0];
+
+                        for (int index = 1; index < sequence.Length; index++)
+                        {
+                            Operation operation = sequence[index];
+
+                            successor.Operations.AddAfter(prependNode, operation);
+
+                            prependNode = operation;
+                        }
+                    }
+                    else
+                    {
+                        // Split the critical edge.
+                        BasicBlock splitBlock = cfg.SplitEdge(block, successor);
+
+                        foreach (Operation operation in sequence)
+                        {
+                            splitBlock.Append(operation);
+                        }
+                    }
+                }
+            }
+        }
+
+        private void ReplaceLocalWithRegister(LiveInterval current)
+        {
+            Operand register = GetRegister(current);
+
+            foreach (int usePosition in current.UsePositions())
+            {
+                (_, Operation operation) = GetOperationNode(usePosition);
+
+                for (int index = 0; index < operation.SourcesCount; index++)
+                {
+                    Operand source = operation.GetSource(index);
+
+                    if (source == current.Local)
+                    {
+                        operation.SetSource(index, register);
+                    }
+                    else if (source.Kind == OperandKind.Memory)
+                    {
+                        MemoryOperand memOp = source.GetMemory();
+
+                        if (memOp.BaseAddress == current.Local)
+                        {
+                            memOp.BaseAddress = register;
+                        }
+
+                        if (memOp.Index == current.Local)
+                        {
+                            memOp.Index = register;
+                        }
+                    }
+                }
+
+                for (int index = 0; index < operation.DestinationsCount; index++)
+                {
+                    Operand dest = operation.GetDestination(index);
+
+                    if (dest == current.Local)
+                    {
+                        operation.SetDestination(index, register);
+                    }
+                }
+            }
+        }
+
+        private static Operand GetRegister(LiveInterval interval)
+        {
+            Debug.Assert(!interval.IsSpilled, "Spilled intervals are not allowed.");
+
+            return Operand.Factory.Register(
+                interval.Register.Index,
+                interval.Register.Type,
+                interval.Local.Type);
+        }
+
+        private (IntrusiveList<Operation>, Operation) GetOperationNode(int position)
+        {
+            return _operationNodes[position / InstructionGap];
+        }
+
+        private void NumberLocals(ControlFlowGraph cfg, int registersCount)
+        {
+            _operationNodes = new List<(IntrusiveList<Operation>, Operation)>();
+            _intervals = new List<LiveInterval>();
+
+            for (int index = 0; index < registersCount; index++)
+            {
+                _intervals.Add(new LiveInterval(new Register(index, RegisterType.Integer)));
+                _intervals.Add(new LiveInterval(new Register(index, RegisterType.Vector)));
+            }
+
+            // The "visited" state is stored in the MSB of the local's value.
+            const ulong VisitedMask = 1ul << 63;
+
+            bool IsVisited(Operand local)
+            {
+                return (local.GetValueUnsafe() & VisitedMask) != 0;
+            }
+
+            void SetVisited(Operand local)
+            {
+                local.GetValueUnsafe() |= VisitedMask;
+            }
+
+            _operationsCount = 0;
+
+            for (int index = cfg.PostOrderBlocks.Length - 1; index >= 0; index--)
+            {
+                BasicBlock block = cfg.PostOrderBlocks[index];
+
+                for (Operation node = block.Operations.First; node != default; node = node.ListNext)
+                {
+                    _operationNodes.Add((block.Operations, node));
+
+                    for (int i = 0; i < node.DestinationsCount; i++)
+                    {
+                        Operand dest = node.GetDestination(i);
+
+                        if (dest.Kind == OperandKind.LocalVariable && !IsVisited(dest))
+                        {
+                            dest.NumberLocal(_intervals.Count);
+
+                            _intervals.Add(new LiveInterval(dest));
+
+                            SetVisited(dest);
+                        }
+                    }
+                }
+
+                _operationsCount += block.Operations.Count * InstructionGap;
+
+                if (block.Operations.Count == 0)
+                {
+                    // Pretend we have a dummy instruction on the empty block.
+                    _operationNodes.Add((default, default));
+
+                    _operationsCount += InstructionGap;
+                }
+            }
+
+            _parentIntervals = _intervals.ToArray();
+        }
+
+        private void BuildIntervals(ControlFlowGraph cfg, AllocationContext context)
+        {
+            _blockRanges = new LiveRange[cfg.Blocks.Count];
+
+            int mapSize = _intervals.Count;
+
+            BitMap[] blkLiveGen  = new BitMap[cfg.Blocks.Count];
+            BitMap[] blkLiveKill = new BitMap[cfg.Blocks.Count];
+
+            // Compute local live sets.
+            for (BasicBlock block = cfg.Blocks.First; block != null; block = block.ListNext)
+            {
+                BitMap liveGen  = new BitMap(Allocators.Default, mapSize);
+                BitMap liveKill = new BitMap(Allocators.Default, mapSize);
+
+                for (Operation node = block.Operations.First; node != default; node = node.ListNext)
+                {
+                    for (int i = 0; i < node.SourcesCount; i++)
+                    {
+                        VisitSource(node.GetSource(i));
+                    }
+
+                    for (int i = 0; i < node.DestinationsCount; i++)
+                    {
+                        VisitDestination(node.GetDestination(i));
+                    }
+
+                    void VisitSource(Operand source)
+                    {
+                        if (IsLocalOrRegister(source.Kind))
+                        {
+                            int id = GetOperandId(source);
+
+                            if (!liveKill.IsSet(id))
+                            {
+                                liveGen.Set(id);
+                            }
+                        }
+                        else if (source.Kind == OperandKind.Memory)
+                        {
+                            MemoryOperand memOp = source.GetMemory();
+
+                            if (memOp.BaseAddress != default)
+                            {
+                                VisitSource(memOp.BaseAddress);
+                            }
+
+                            if (memOp.Index != default)
+                            {
+                                VisitSource(memOp.Index);
+                            }
+                        }
+                    }
+
+                    void VisitDestination(Operand dest)
+                    {
+                        liveKill.Set(GetOperandId(dest));
+                    }
+                }
+
+                blkLiveGen [block.Index] = liveGen;
+                blkLiveKill[block.Index] = liveKill;
+            }
+
+            // Compute global live sets.
+            BitMap[] blkLiveIn  = new BitMap[cfg.Blocks.Count];
+            BitMap[] blkLiveOut = new BitMap[cfg.Blocks.Count];
+
+            for (int index = 0; index < cfg.Blocks.Count; index++)
+            {
+                blkLiveIn [index] = new BitMap(Allocators.Default, mapSize);
+                blkLiveOut[index] = new BitMap(Allocators.Default, mapSize);
+            }
+
+            bool modified;
+
+            do
+            {
+                modified = false;
+
+                for (int index = 0; index < cfg.PostOrderBlocks.Length; index++)
+                {
+                    BasicBlock block = cfg.PostOrderBlocks[index];
+
+                    BitMap liveOut = blkLiveOut[block.Index];
+
+                    for (int i = 0; i < block.SuccessorsCount; i++)
+                    {
+                        BasicBlock succ = block.GetSuccessor(i);
+
+                        modified |= liveOut.Set(blkLiveIn[succ.Index]);
+                    }
+
+                    BitMap liveIn = blkLiveIn[block.Index];
+
+                    liveIn.Set  (liveOut);
+                    liveIn.Clear(blkLiveKill[block.Index]);
+                    liveIn.Set  (blkLiveGen [block.Index]);
+                }
+            }
+            while (modified);
+
+            _blockLiveIn = blkLiveIn;
+
+            _blockEdges = new HashSet<int>();
+
+            // Compute lifetime intervals.
+            int operationPos = _operationsCount;
+
+            for (int index = 0; index < cfg.PostOrderBlocks.Length; index++)
+            {
+                BasicBlock block = cfg.PostOrderBlocks[index];
+
+                // We handle empty blocks by pretending they have a dummy instruction,
+                // because otherwise the block would have the same start and end position,
+                // and this is not valid.
+                int instCount = Math.Max(block.Operations.Count, 1);
+
+                int blockStart = operationPos - instCount * InstructionGap;
+                int blockEnd   = operationPos;
+
+                _blockRanges[block.Index] = new LiveRange(blockStart, blockEnd);
+
+                _blockEdges.Add(blockStart);
+
+                BitMap liveOut = blkLiveOut[block.Index];
+
+                foreach (int id in liveOut)
+                {
+                    _intervals[id].AddRange(blockStart, blockEnd);
+                }
+
+                if (block.Operations.Count == 0)
+                {
+                    operationPos -= InstructionGap;
+
+                    continue;
+                }
+
+                for (Operation node = block.Operations.Last; node != default; node = node.ListPrevious)
+                {
+                    operationPos -= InstructionGap;
+
+                    for (int i = 0; i < node.DestinationsCount; i++)
+                    {
+                        VisitDestination(node.GetDestination(i));
+                    }
+
+                    for (int i = 0; i < node.SourcesCount; i++)
+                    {
+                        VisitSource(node.GetSource(i));
+                    }
+
+                    if (node.Instruction == Instruction.Call)
+                    {
+                        AddIntervalCallerSavedReg(context.Masks.IntCallerSavedRegisters, operationPos, RegisterType.Integer);
+                        AddIntervalCallerSavedReg(context.Masks.VecCallerSavedRegisters, operationPos, RegisterType.Vector);
+                    }
+
+                    void VisitSource(Operand source)
+                    {
+                        if (IsLocalOrRegister(source.Kind))
+                        {
+                            LiveInterval interval = _intervals[GetOperandId(source)];
+
+                            interval.AddRange(blockStart, operationPos + 1);
+                            interval.AddUsePosition(operationPos);
+                        }
+                        else if (source.Kind == OperandKind.Memory)
+                        {
+                            MemoryOperand memOp = source.GetMemory();
+
+                            if (memOp.BaseAddress != default)
+                            {
+                                VisitSource(memOp.BaseAddress);
+                            }
+
+                            if (memOp.Index != default)
+                            {
+                                VisitSource(memOp.Index);
+                            }
+                        }
+                    }
+
+                    void VisitDestination(Operand dest)
+                    {
+                        LiveInterval interval = _intervals[GetOperandId(dest)];
+
+                        if (interval.IsFixed)
+                        {
+                            interval.IsFixedAndUsed = true;
+                        }
+
+                        interval.SetStart(operationPos + 1);
+                        interval.AddUsePosition(operationPos + 1);
+                    }
+                }
+            }
+
+            foreach (LiveInterval interval in _parentIntervals)
+            {
+                interval.Reset();
+            }
+        }
+
+        private void AddIntervalCallerSavedReg(int mask, int operationPos, RegisterType regType)
+        {
+            while (mask != 0)
+            {
+                int regIndex = BitOperations.TrailingZeroCount(mask);
+
+                Register callerSavedReg = new Register(regIndex, regType);
+
+                LiveInterval interval = _intervals[GetRegisterId(callerSavedReg)];
+
+                interval.AddRange(operationPos + 1, operationPos + InstructionGap);
+
+                mask &= ~(1 << regIndex);
+            }
+        }
+
+        private static int GetOperandId(Operand operand)
+        {
+            if (operand.Kind == OperandKind.LocalVariable)
+            {
+                return operand.GetLocalNumber();
+            }
+            else if (operand.Kind == OperandKind.Register)
+            {
+                return GetRegisterId(operand.GetRegister());
+            }
+            else
+            {
+                throw new ArgumentException($"Invalid operand kind \"{operand.Kind}\".");
+            }
+        }
+
+        private static int GetRegisterId(Register register)
+        {
+            return (register.Index << 1) | (register.Type == RegisterType.Vector ? 1 : 0);
+        }
+
+        private static bool IsLocalOrRegister(OperandKind kind)
+        {
+            return kind == OperandKind.LocalVariable ||
+                   kind == OperandKind.Register;
+        }
+    }
+}
\ No newline at end of file