Merge branch 'fix_gvn' into 'main'

Fix GVN

See merge request !66

hercules_opt/src/gvn.rs

@@ -17,6 +17,11 @@ pub fn gvn(editor: &mut FunctionEditor) {
     let mut value_numbers: HashMap<Node, NodeID> = HashMap::new();
 
     while let Some(work) = worklist.pop() {
+        // Deleted nodes (and technically the original start) should be skipped.
+        if editor.func().nodes[work.idx()].is_start() {
+            continue;
+        }
+
         // First, simplify the work node by unwrapping identity functions.
         let value = crawl_identities(work, editor);