Re: [PATCH v6 03/10] x86, mpx: add macro cpu_has_mpx

[Dave Hansen]

On 06/19/2014 11:02 AM, H. Peter Anvin wrote:
> On 06/18/2014 09:25 AM, Dave Hansen wrote:
>> How about something like the attached patch?
>>
>> This lets us use static_cpu_has() for the checks, and allows us to
>> easily add new checks for other features that might be compile-time
>> disabled.
> 
> Hmm... I would like something similar to required-features.h which
> reflect features which *cannot* be enabled or will always be ignored; we
> actually already have a handful of those

Could you elaborate a bit?  I'll try and include them in the approach to
make sure it works broadly.

Is there a benefit to the required-features.h approach that's missing
from mine?  I _believe_ all of the compiler optimization around
__builtin_constant_p() continues to work with the inline function
instead of the #defines and bitmasks.  I think the inline function
approach is a bit easier to work with.

Could the required-features.h approach just be from a time before
__builtin_constant_p() worked well across inlines?
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