diff --git a/src/main/java/chocopy/pa3/CodeGenImpl.java b/src/main/java/chocopy/pa3/CodeGenImpl.java
index 24ad42d..cbf3287 100644
--- a/src/main/java/chocopy/pa3/CodeGenImpl.java
+++ b/src/main/java/chocopy/pa3/CodeGenImpl.java
@@ -212,13 +212,16 @@ public class CodeGenImpl extends CodeGenBase
         private int getRegister(){ //return a handle of a vacant register
             for(int i = 0; i < 10; ++i)
                 if(registerAvilMap[i])
+                {
+                    registerAvilMap[i]=false;
                     return i;
+                }
             for(int i = 0; i < 10; ++i)
                 registerAvilMap[i] = true; //freeall;
             return 0;
         }
         private void freeRegister(int handle){ //handle used to free the register
-            registerAvilMap[handle] = false;
+            registerAvilMap[handle] = true;
         }
         
         private int getParamLocationOffset(int index, int paramSize) {
@@ -987,6 +990,7 @@ public class CodeGenImpl extends CodeGenBase
             {
                 Label startLoop = generateLocalLabel();
                 Label endLoop = generateLocalLabel();
+                Label temp = generateLocalLabel();
                 r=getRegister();
                 regs.add(r);
                 Register iden = registerPool[r];
@@ -997,15 +1001,28 @@ public class CodeGenImpl extends CodeGenBase
                 r=getRegister();
                 regs.add(r);
                 Register ln = registerPool[r];
+                backend.emitBNEZ(Register.A0, temp, "Ensure not none");
+                backend.emitJ(errorNone, "Empty List");
+                backend.emitLocalLabel(temp, "Continue execution for for-loop");
                 backend.emitMV(l,Register.A0,"Location of list");
                 r=getRegister();
                 regs.add(r);
                 Register iter = registerPool[r];
+                backend.emitSW(l, Register.FP, -sp_off*wordSize, "Store index on stack");
+                incSp(1);
                 backend.emitMV(iter, Register.ZERO, "Initialize index variable");
+                backend.emitSW(iter, Register.FP, -sp_off*wordSize, "Store index on stack");
+                incSp(1);
                 backend.emitLocalLabel(startLoop, "Start for loop");
+                sp_off--;
+                backend.emitLW(iter, Register.FP, -sp_off*wordSize, "Load index from stack");
+                backend.emitLW(l, Register.FP, -(sp_off-1)*wordSize, "Store list location from stack");
                 backend.emitLW(ln, l, getAttrOffset(listClass, "__len__"), "Get attribute __len__");
-                backend.emitBGE(iter, ln, endLoop, "Jump to end loop if counter exceeds length");
-                backend.emitADDI(iden, iter, 4, "Compute list element offset in words");
+                backend.emitBGEU(iter, ln, endLoop, "Jump to end loop if counter exceeds length");
+                backend.emitADDI(iter, iter, 1, "Increment counter");
+                backend.emitSW(iter, Register.FP, -sp_off*wordSize, "Store index on stack");
+                incSp(1);
+                backend.emitADDI(iden, iter, 3, "Compute list element offset in words");
                 backend.emitLI(ln, wordSize, "Word size in bytes");
                 backend.emitMUL(iden, iden, ln, "Compute list element offset in bytes");
                 backend.emitADD(iden, l, iden, "Pointer to list element");
@@ -1024,7 +1041,6 @@ public class CodeGenImpl extends CodeGenBase
                 }
                 for(Stmt stmt:node.body)
                     stmt.dispatch(this);
-                backend.emitADDI(iter, iter, 1, "Increment counter");
                 backend.emitJ(startLoop, "Jump to beginning of loop");
                 backend.emitLocalLabel(endLoop, "End of for loop");
             }
diff --git a/test_sample.sh b/test_sample.sh
index eaaa8bf..b6da460 100755
--- a/test_sample.sh
+++ b/test_sample.sh
@@ -2,4 +2,4 @@
 
 
 echo "Running all test cases inside src/test/data/pa3/sample/ folder)"
-java -cp "chocopy-ref.jar:target/assignment.jar" chocopy.ChocoPy --pass=rrs --test --run --dir src/test/data/pa3/sample/
+java -cp "chocopy-ref.jar:target/assignment.jar" chocopy.ChocoPy --pass=rrs --test --run --dir src/test/data/pa3/sample/  --maxCycles 65536