The Kadamba Tree says...

#ifdef __SMP__
#error "Me no hablo Alpha SMP"
#else
#define irq_enter(cpu, irq)     (++local_irq_count[cpu])
#define irq_exit(cpu, irq)      (--local_irq_count[cpu])
#endif
		-- from kernel 2.1.90, arch/alpha/kernel/irc.c