1 files changed, 126 insertions, 0 deletions
diff --git a/ARMeilleure/CodeGen/Optimizations/Optimizer.cs b/ARMeilleure/CodeGen/Optimizations/Optimizer.cs
new file mode 100644
index 00000000..c01a8f1e
--- /dev/null
+++ b/ARMeilleure/CodeGen/Optimizations/Optimizer.cs
@@ -0,0 +1,126 @@
+using ARMeilleure.IntermediateRepresentation;
+using ARMeilleure.Translation;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+
+namespace ARMeilleure.CodeGen.Optimizations
+{
+    static class Optimizer
+    {
+        public static void RunPass(ControlFlowGraph cfg)
+        {
+            bool modified;
+
+            do
+            {
+                modified = false;
+
+                foreach (BasicBlock block in cfg.Blocks)
+                {
+                    LinkedListNode<Node> node = block.Operations.First;
+
+                    while (node != null)
+                    {
+                        LinkedListNode<Node> nextNode = node.Next;
+
+                        bool isUnused = IsUnused(node.Value);
+
+                        if (!(node.Value is Operation operation) || isUnused)
+                        {
+                            if (isUnused)
+                            {
+                                RemoveNode(block, node);
+
+                                modified = true;
+                            }
+
+                            node = nextNode;
+
+                            continue;
+                        }
+
+                        ConstantFolding.RunPass(operation);
+
+                        Simplification.RunPass(operation);
+
+                        if (DestIsLocalVar(operation) && IsPropagableCopy(operation))
+                        {
+                            PropagateCopy(operation);
+
+                            RemoveNode(block, node);
+
+                            modified = true;
+                        }
+
+                        node = nextNode;
+                    }
+                }
+            }
+            while (modified);
+        }
+
+        private static void PropagateCopy(Operation copyOp)
+        {
+            // Propagate copy source operand to all uses of the destination operand.
+            Operand dest   = copyOp.Destination;
+            Operand source = copyOp.GetSource(0);
+
+            Node[] uses = dest.Uses.ToArray();
+
+            foreach (Node use in uses)
+            {
+                for (int index = 0; index < use.SourcesCount; index++)
+                {
+                    if (use.GetSource(index) == dest)
+                    {
+                        use.SetSource(index, source);
+                    }
+                }
+            }
+        }
+
+        private static void RemoveNode(BasicBlock block, LinkedListNode<Node> llNode)
+        {
+            // Remove a node from the nodes list, and also remove itself
+            // from all the use lists on the operands that this node uses.
+            block.Operations.Remove(llNode);
+
+            Node node = llNode.Value;
+
+            for (int index = 0; index < node.SourcesCount; index++)
+            {
+                node.SetSource(index, null);
+            }
+
+            Debug.Assert(node.Destination == null || node.Destination.Uses.Count == 0);
+
+            node.Destination = null;
+        }
+
+        private static bool IsUnused(Node node)
+        {
+            return DestIsLocalVar(node) && node.Destination.Uses.Count == 0 && !HasSideEffects(node);
+        }
+
+        private static bool DestIsLocalVar(Node node)
+        {
+            return node.Destination != null && node.Destination.Kind == OperandKind.LocalVariable;
+        }
+
+        private static bool HasSideEffects(Node node)
+        {
+            return (node is Operation operation) && operation.Instruction == Instruction.Call;
+        }
+
+        private static bool IsPropagableCopy(Operation operation)
+        {
+            if (operation.Instruction != Instruction.Copy)
+            {
+                return false;
+            }
+
+            return operation.Destination.Type == operation.GetSource(0).Type;
+        }
+    }
+}
+\ No newline at end of file