Re: [PATCH] log2: make is_power_of_2() integer constant expression when possible

[Andrew Morton]

On Fri,  1 Mar 2019 14:52:07 +0200 Jani Nikula <jani.nikula@xxxxxxxxx> wrote:

> While is_power_of_2() is an inline function and likely gets optimized
> for compile time constant arguments, it still doesn't produce an integer
> constant expression that could be used in, say, static data
> initialization or case labels.

hm, what code wants to do these things?

> Make is_power_of_2() an integer constant expression when possible,
> otherwise using the inline function to avoid multiple evaluation of the
> parameter.

Spose so.  But I fear that some gcc versions will get it right and
others will mess it up.  While this patch is under test I think it
would be best to also have at least one or two callsites which actually
use the compile-time evaluation feature.  Possible?