lkml.org 
[lkml]   [2008]   [Oct]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] x86: do not allow to optimize flag_is_changeable_p() (rev. 2)

* Krzysztof Helt <krzysztof.h1@wp.pl> wrote:

> From: Krzysztof Helt <krzysztof.h1@wp.pl>
>
> The flag_is_changeable_p() is used by
> has_cpuid_p() which can return different results
> in the code sequence below:
>
> if (!have_cpuid_p())
> identify_cpu_without_cpuid(c);
>
> /* cyrix could have cpuid enabled via c_identify()*/
> if (!have_cpuid_p())
> return;
>
> Otherwise, the gcc 3.4.6 optimizes these two calls
> into one which make the code not working correctly.
>
> Cyrix cpus have the CPUID instruction enabled before
> the second call to the have_cpuid_p() but
> it is not detected due to the gcc optimization.
> Thus the ARR registers (mtrr like) are not detected
> on such a cpu.
>
> Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>

applied to tip/x86/core, thanks Krzysztof!

Ingo


\
 
 \ /
  Last update: 2008-10-01 09:15    [W:0.035 / U:0.468 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site