Does gcc optimize "if (constant)" inside while loops?

[Timur Tabi <timur@xxxxxxxxxxxxx>]

I have this code:

#define spin_event_timeout(condition, timeout, delay, rc)                   \
{                                                                           \
	unsigned long __loops = tb_ticks_per_usec * timeout;                \
	unsigned long __start = get_tbl();                                  \
	while (!(rc = (condition)) && (tb_ticks_since(__start) <= __loops)) \
		if (delay)                                                  \
			udelay(delay);                                      \
		else	                                                    \
			cpu_relax();                                        \
}

assuming that the 'delay' parameter is a constant, will gcc
optimize-out the "if (delay)" when this macro is compiled?

That is, is the above code equivalent to:

#define spin_event_timeout(condition, timeout, delay, rc)                   \
{                                                                           \
	unsigned long __loops = tb_ticks_per_usec * timeout;                \
	unsigned long __start = get_tbl();                                  \
	if (delay)                                                          \
		while (!(rc = (condition)) && (tb_ticks_since(__start) <= __loops)) \
			udelay(delay);                                      \
	else	                                                            \
		while (!(rc = (condition)) && (tb_ticks_since(__start) <= __loops)) \
			cpu_relax();                                        \
}


-- 
Timur Tabi
Linux kernel developer at Freescale