public void visitJumpInsn(final int opcode, final Label lbl) {
        super.visitJumpInsn(opcode, lbl);
        LabelNode ln = ((JumpInsnNode) instructions.getLast()).label;
        if (opcode == JSR && !subroutineHeads.containsKey(ln)) {
            subroutineHeads.put(ln, new Subroutine());
        }
    }