Re: [Qemu-devel] [PATCH 1/3] [x86] Clean up vendor identification

[Laurent Vivier]

Le lundi 11 août 2008 à 14:32 +0200, Alexander Graf a écrit :
> On Aug 11, 2008, at 1:56 PM, Laurent Vivier wrote:
> 
> > Le lundi 11 août 2008 à 12:37 +0200, Alexander Graf a écrit :
> >> Right now CPU vendor identification contains a lot of magic numbers.
> >> The
> >> patch cleans them up to defines, so we can identify the CPU later on
> >> without copying magic numbers.
> >>
> >> Signed-off-by: Alexander Graf <address@hidden>
> >>
> >>
> >>
> >> diff --git a/qemu/target-i386/cpu.h b/qemu/target-i386/cpu.h
> >> index 7e95900..3c84dc9 100644
> >> --- a/qemu/target-i386/cpu.h
> >> +++ b/qemu/target-i386/cpu.h
> >> @@ -339,6 +341,14 @@
> >> #define CPUID_EXT3_IBS     (1 << 10)
> >> #define CPUID_EXT3_SKINIT  (1 << 12)
> >>
> >> +#define CPUID_VENDOR_INTEL_1 0x756e6547 /* "Genu" */
> >> +#define CPUID_VENDOR_INTEL_2 0x49656e69 /* "ineI" */
> >> +#define CPUID_VENDOR_INTEL_3 0x6c65746e /* "ntel" */
> >> +
> >> +#define CPUID_VENDOR_AMD_1   0x68747541 /* "Auth" */
> >> +#define CPUID_VENDOR_AMD_2   0x69746e65 /* "enti" */
> >> +#define CPUID_VENDOR_AMD_3   0x444d4163 /* "cAMD" */
> >
> > if you add "-Wno-multichar" in C flags, you can use:
> >
> > #define CPUID_VENDOR_INTEL_1 'Genu'
> > ...
> 
> Is that a real improvement? It won't make the code faster and the  
> readability doesn't improve that much either.

The code is not faster, it is not more readable,
but when you read this, are you sure 0x756e6547 is equal to "Genu" ?

Personally, I'm not.

But I agree using 'Genu' can have an impact on portability.

Regards,
Laurent
-- 
----------------- address@hidden  ------------------
  "La perfection est atteinte non quand il ne reste rien à
ajouter mais quand il ne reste rien à enlever." Saint Exupéry