1 files changed, 159 insertions, 0 deletions
diff --git a/src/ARMeilleure/IntermediateRepresentation/BasicBlock.cs b/src/ARMeilleure/IntermediateRepresentation/BasicBlock.cs
new file mode 100644
index 00000000..07bd8b67
--- /dev/null
+++ b/src/ARMeilleure/IntermediateRepresentation/BasicBlock.cs
@@ -0,0 +1,159 @@
+using System;
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+
+namespace ARMeilleure.IntermediateRepresentation
+{
+    class BasicBlock : IEquatable<BasicBlock>, IIntrusiveListNode<BasicBlock>
+    {
+        private const uint MaxSuccessors = 2;
+
+        private int _succCount;
+        private BasicBlock _succ0;
+        private BasicBlock _succ1;
+        private HashSet<BasicBlock> _domFrontiers;
+
+        public int Index { get; set; }
+        public BasicBlockFrequency Frequency { get; set; }
+        public BasicBlock ListPrevious { get; set; }
+        public BasicBlock ListNext { get; set; }
+        public IntrusiveList<Operation> Operations { get; }
+        public List<BasicBlock> Predecessors { get; }
+        public BasicBlock ImmediateDominator { get; set; }
+
+        public int SuccessorsCount => _succCount;
+
+        public HashSet<BasicBlock> DominanceFrontiers
+        {
+            get
+            {
+                if (_domFrontiers == null)
+                {
+                    _domFrontiers = new HashSet<BasicBlock>();
+                }
+
+                return _domFrontiers;
+            }
+        }
+
+        public BasicBlock() : this(index: -1) { }
+
+        public BasicBlock(int index)
+        {
+            Operations = new IntrusiveList<Operation>();
+            Predecessors = new List<BasicBlock>();
+
+            Index = index;
+        }
+
+        public void AddSuccessor(BasicBlock block)
+        {
+            ArgumentNullException.ThrowIfNull(block);
+
+            if ((uint)_succCount + 1 > MaxSuccessors)
+            {
+                ThrowSuccessorOverflow();
+            }
+
+            block.Predecessors.Add(this);
+
+            GetSuccessorUnsafe(_succCount++) = block;
+        }
+
+        public void RemoveSuccessor(int index)
+        {
+            if ((uint)index >= (uint)_succCount)
+            {
+                ThrowOutOfRange(nameof(index));
+            }
+
+            ref BasicBlock oldBlock = ref GetSuccessorUnsafe(index);
+
+            oldBlock.Predecessors.Remove(this);
+            oldBlock = null;
+
+            if (index == 0)
+            {
+                _succ0 = _succ1;
+            }
+
+            _succCount--;
+        }
+
+        public BasicBlock GetSuccessor(int index)
+        {
+            if ((uint)index >= (uint)_succCount)
+            {
+                ThrowOutOfRange(nameof(index));
+            }
+
+            return GetSuccessorUnsafe(index);
+        }
+
+        private ref BasicBlock GetSuccessorUnsafe(int index)
+        {
+            return ref Unsafe.Add(ref _succ0, index);
+        }
+
+        public void SetSuccessor(int index, BasicBlock block)
+        {
+            ArgumentNullException.ThrowIfNull(block);
+
+            if ((uint)index >= (uint)_succCount)
+            {
+                ThrowOutOfRange(nameof(index));
+            }
+
+            ref BasicBlock oldBlock = ref GetSuccessorUnsafe(index);
+
+            oldBlock.Predecessors.Remove(this);
+            block.Predecessors.Add(this);
+            
+            oldBlock = block;
+        }
+
+        public void Append(Operation node)
+        {
+            Operation last = Operations.Last;
+
+            // Append node before terminal or to end if no terminal.
+            if (last == default)
+            {
+                Operations.AddLast(node);
+
+                return;
+            }
+
+            switch (last.Instruction)
+            {
+                case Instruction.Return:
+                case Instruction.Tailcall:
+                case Instruction.BranchIf:
+                    Operations.AddBefore(last, node);
+                    break;
+
+                default:
+                    Operations.AddLast(node);
+                    break;
+            }
+        }
+
+        private static void ThrowOutOfRange(string name) => throw new ArgumentOutOfRangeException(name);
+        private static void ThrowSuccessorOverflow() => throw new OverflowException($"BasicBlock can only have {MaxSuccessors} successors.");
+
+        public bool Equals(BasicBlock other)
+        {
+            return other == this;
+        }
+
+        public override bool Equals(object obj)
+        {
+            return Equals(obj as BasicBlock);
+        }
+
+        public override int GetHashCode()
+        {
+            return base.GetHashCode();
+        }
+    }
+}
+\ No newline at end of file