fixed sp_off initial value

src/main/java/chocopy/pa3/CodeGenImpl.java

@@ -252,7 +252,7 @@ public class CodeGenImpl extends CodeGenBase
                 size_label = "@..main.size";
             } else {
                 sym = funcInfo.getSymbolTable();
-                sp_off = max_sp = funcInfo0.getLocals().size() + 2;
+                sp_off = max_sp = funcInfo0.getLocals().size() + 2 + 1;
                 size_label = "@"+funcInfo0.getFuncName()+".size";
             }
             epilogue = generateLocalLabel();
@@ -643,10 +643,12 @@ public class CodeGenImpl extends CodeGenBase
 
             if(node.left.getInferredType().equals(Type.INT_TYPE) && node.right.getInferredType().equals(Type.INT_TYPE))
             {
-                node.right.dispatch(this);
-                backend.emitSW(Register.A0, Register.FP, -sp_off*wordSize, "Push on stack slot "+sp_off);
+                Register r = node.right.dispatch(this);
+                backend.emitSW(r, Register.FP, -sp_off*wordSize, "Push on stack slot "+sp_off);
                 incSp(1);
-                node.left.dispatch(this);
+                Register l = node.left.dispatch(this);
+                if(l != A0)
+                    backend.emitMV(A0, l, "mv l to A0");
                 sp_off--;
                 backend.emitLW(Register.T0, Register.FP, -sp_off*wordSize, "Pop stack slot "+sp_off);