Move solution and projects to src

src/ARMeilleure/CodeGen/RegisterAllocators/UseList.cs

@@ -0,0 +1,84 @@
+using System;
+
+namespace ARMeilleure.CodeGen.RegisterAllocators
+{
+    unsafe struct UseList
+    {
+        private int* _items;
+        private int _capacity;
+        private int _count;
+
+        public int Count => _count;
+        public int FirstUse => _count > 0 ? _items[_count - 1] : LiveInterval.NotFound;
+        public Span<int> Span => new(_items, _count);
+
+        public void Add(int position)
+        {
+            if (_count + 1 > _capacity)
+            {
+                var oldSpan = Span;
+
+                _capacity = Math.Max(4, _capacity * 2);
+                _items = Allocators.Default.Allocate<int>((uint)_capacity);
+
+                var newSpan = Span;
+
+                oldSpan.CopyTo(newSpan);
+            }
+
+            // Use positions are usually inserted in descending order, so inserting in descending order is faster,
+            // since the number of half exchanges is reduced.
+            int i = _count - 1;
+
+            while (i >= 0 && _items[i] < position)
+            {
+                _items[i + 1] = _items[i--];
+            }
+
+            _items[i + 1] = position;
+            _count++;
+        }
+
+        public int NextUse(int position)
+        {
+            int index = NextUseIndex(position);
+
+            return index != LiveInterval.NotFound ? _items[index] : LiveInterval.NotFound;
+        }
+
+        public int NextUseIndex(int position)
+        {
+            int i = _count - 1;
+
+            if (i == -1 || position > _items[0])
+            {
+                return LiveInterval.NotFound;
+            }
+
+            while (i >= 0 && _items[i] < position)
+            {
+                i--;
+            }
+
+            return i;
+        }
+
+        public UseList Split(int position)
+        {
+            int index = NextUseIndex(position);
+
+            // Since the list is in descending order, the new split list takes the front of the list and the current
+            // list takes the back of the list.
+            UseList result = new();
+            result._count = index + 1;
+            result._capacity = result._count;
+            result._items = _items;
+
+            _count = _count - result._count;
+            _capacity = _count;
+            _items = _items + result._count;
+
+            return result;
+        }
+    }
+}