Messages in this thread | | | From | Jani Nikula <> | Subject | Re: [PATCH] log2: make is_power_of_2() integer constant expression when possible | Date | Mon, 04 Mar 2019 12:16:02 +0200 |
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On Fri, 01 Mar 2019, Andrew Morton <akpm@linux-foundation.org> wrote: > On Fri, 1 Mar 2019 14:52:07 +0200 Jani Nikula <jani.nikula@intel.com> 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?
I have some drm/i915 patches that have a local compile-time version of IS_POWER_OF_2(). It'll take a while before they hit Linus' master. This can wait.
BR, Jani.
-- Jani Nikula, Intel Open Source Graphics Center
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