diff --git a/src/opt/deadcode.rs b/src/opt/deadcode.rs
index f9f1d22..9588281 100644
--- a/src/opt/deadcode.rs
+++ b/src/opt/deadcode.rs
@@ -1,6 +1,5 @@
 use core::ops::Deref;
 use std::collections::{HashMap, HashSet};
-use std::ops::DerefMut;
 
 use crate::ir::*;
 use crate::opt::opt_utils::*;
@@ -81,18 +80,15 @@ impl Optimize<FunctionDefinition> for DeadcodeInner {
             }
         }
 
-        println!("{used_allocations:?} /// {used_registers:?}");
-
-        let mut replaces = HashMap::new();
-
         let survived_allocations = code
             .allocations
             .iter()
             .enumerate()
             .filter(|(aid, _)| used_allocations.contains(aid))
             .collect::<Vec<_>>();
+        let mut replaces = HashMap::new();
+
         if survived_allocations.len() != code.allocations.len() {
-            println!("hi~!");
             for (new_aid, (old_aid, dtype)) in survived_allocations.iter().enumerate() {
                 let _unused = replaces.insert(
                     RegisterId::local(*old_aid),
@@ -122,6 +118,13 @@ impl Optimize<FunctionDefinition> for DeadcodeInner {
                 })
                 .collect::<HashSet<_>>();
 
+            for iid_nop in &nop_instructions {
+                let _unused = replaces.insert(
+                    RegisterId::temp(*bid, *iid_nop),
+                    Operand::constant(Constant::unit()),
+                );
+            }
+
             let survived_instructions = block
                 .instructions
                 .iter()
@@ -132,6 +135,7 @@ impl Optimize<FunctionDefinition> for DeadcodeInner {
                         || !inst.has_no_side_effects()
                 })
                 .collect::<Vec<_>>();
+
             if survived_instructions.len() != block.instructions.len() {
                 for (new_iid, (old_iid, inst)) in survived_instructions.iter().enumerate() {
                     let _unused = replaces.insert(
@@ -140,13 +144,6 @@ impl Optimize<FunctionDefinition> for DeadcodeInner {
                     );
                 }
 
-                for iid_nop in &nop_instructions {
-                    let _unused = replaces.insert(
-                        RegisterId::temp(*bid, *iid_nop),
-                        Operand::constant(Constant::unit()),
-                    );
-                }
-
                 block.instructions = survived_instructions
                     .into_iter()
                     .map(|(_, inst)| inst.clone())
@@ -184,8 +181,6 @@ impl Optimize<FunctionDefinition> for DeadcodeInner {
             }
         }
 
-        println!("replaces: {replaces:?}");
-
         for (bid, block) in code.blocks.iter_mut() {
             for inst in block.instructions.iter_mut() {
                 let _ = replace_instruction_operands(inst, &replaces);
@@ -221,16 +216,12 @@ fn mark_as_used(
     used_allocations: &mut HashSet<usize>,
     used_registers: &mut HashSet<RegisterId>,
 ) {
-    match operand {
-        Operand::Register { rid, .. } => match rid {
-            RegisterId::Local { aid } => {
-                let _ = used_allocations.insert(*aid);
-            }
-            _ => {
-                let _ = used_registers.insert(*rid);
-            }
-        },
-        _ => (),
+    if let Some((rid, _)) = operand.get_register() {
+        if let RegisterId::Local { aid } = rid {
+            let _ = used_allocations.insert(*aid);
+        } else {
+            let _ = used_registers.insert(*rid);
+        }
     }
 }
 
@@ -257,6 +248,6 @@ fn kill_jump_args(arg: &mut JumpArg, survived_phinodess: &HashMap<BlockId, HashS
                 None
             }
         })
-        .collect::<Vec<_>>();
+        .collect();
     arg.args = survived_args;
 }