1 files changed, 52 insertions, 0 deletions
diff --git a/llparse-frontend/src/peephole.ts b/llparse-frontend/src/peephole.ts
new file mode 100644
index 0000000..19ac13f
--- /dev/null
+++ b/llparse-frontend/src/peephole.ts
@@ -0,0 +1,52 @@
+import { Node, Empty } from './node';
+import { IWrap } from './wrap';
+
+type WrapNode = IWrap<Node>;
+type WrapList = ReadonlyArray<WrapNode>;
+
+export class Peephole {
+  public optimize(root: WrapNode, nodes: WrapList): WrapNode {
+    let changed = new Set(nodes);
+
+    while (changed.size !== 0) {
+      const previous = changed;
+      changed = new Set();
+
+      for (const node of previous) {
+        if (this.optimizeNode(node)) {
+          changed.add(node);
+        }
+      }
+    }
+
+    while (root.ref instanceof Empty) {
+      if (!root.ref.otherwise!.noAdvance) {
+        break;
+      }
+
+      root = root.ref.otherwise!.node;
+    }
+
+    return root;
+  }
+
+  public optimizeNode(node: WrapNode): boolean {
+    let changed = false;
+    for (const slot of node.ref.getSlots()) {
+      if (!(slot.node.ref instanceof Empty)) {
+        continue;
+      }
+
+      const otherwise = slot.node.ref.otherwise!;
+
+      // Node actively skips, can't optimize!
+      if (!otherwise.noAdvance) {
+        continue;
+      }
+
+      slot.node = otherwise.node;
+      changed = true;
+    }
+    return changed;
+  }
+}