question oh macros and gcc's intelligence

DISCUSSION Oliver Neukum 2 participants 2 messages Mar 17, 2011

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Oliver Neukum

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2011-03-17 08:55 UTC #0 lore raw

Hi,

if I write:

if (le16_to_cpu(p) == CONST) a();

is gcc smart enough to convert CONST to le16 and do a simple comparison?

Regards
Oliver

2011-03-17 09:06 UTC #1 lore raw

Quoted 8 lines · Oliver Neukum

Hi,
if I write:
if (le16_to_cpu(p) == CONST) a();
is gcc smart enough to convert CONST to le16 and do a simple comparison?

On little-endian - certainly, on big-endian - forget it.

	if (p == cpu_to_le16(CONST))

would obviously work on any architecture and yes, it would be a comparison with compile-time constant.