minor bugfixes

asm/src/main.rs

@@ -579,6 +579,10 @@ fn process_line(prgm: &mut Program, (linenum, line): (usize, String), rgx: &Rege
             chk(2);
             Instruction::Xor(reg(0), reg(1), Op2::Direct(-1))
         }
+        "swi" => {
+            chk(0);
+            Instruction::Swi()
+        }
         "let" => {
             chk(2);
             let r = reg(0);