Update homework 1 and 2

src/opt/mem2reg.rs

@@ -0,0 +1,11 @@
+use crate::ir;
+use crate::*;
+
+#[derive(Default)]
+pub struct Mem2reg {}
+
+impl Optimize<ir::TranslationUnit> for Mem2reg {
+    fn optimize(&mut self, _code: &mut ir::TranslationUnit) -> bool {
+        todo!()
+    }
+}