Re: [Minios-devel] Should we have to be aware of GCC version in Unikraft?

[Wei Chen <Wei.Chen@xxxxxxx>]

Hi Simon,

> -----Original Message-----
> From: Simon Kuenzer [mailto:simon.kuenzer@xxxxxxxxx]
> Sent: 2018年3月12日 21:06
> To: Wei Chen <Wei.Chen@xxxxxxx>
> Cc: Costin Lupu <costin.lup@xxxxxxxxx>; Felipe Huici <Felipe.Huici@xxxxxxxxx>;
> Kaly Xin <Kaly.Xin@xxxxxxx>; Shijie Huang <Shijie.Huang@xxxxxxx>; Florian
> Schmidt <Florian.Schmidt@xxxxxxxxx>; nd <nd@xxxxxxx>; minios-
> devel@xxxxxxxxxxxxx
> Subject: Re: Should we have to be aware of GCC version in Unikraft?
> 
> Hey Wei,
> 
> we have some code in the build system that stores the used GCC version
> in a variable already. Have a look to Makefile in the base directory and
> search for CC_VERSION. Maybe you need to modify it - e.g., separate
> major and minor number. There is no code or Makefile that uses this
> variable currently. So, you do not need to worry that something would break.
> 

Thanks.
Yes, I will use the retrieve the major and minor number from CC_VERSION.

> On 12.03.2018 08:26, Wei Chen wrote:
> > Hi Simon,
> >
> > In Unikraft, we will add corresponding GCC flags to do processor
> optimization
> > for target processor. In this case, I want to list a full set of standard
> ARMv8
> > Cortex-A series processors (from Cortex-a53 to latest Cortex-a75) in this
> menu.
> >
> > But different GCC version supports different processors set for -mtune. For
> > example the latest gcc-7 can support the full set of standard ARMv8 Cortex-A
> > series processors, but gcc-4.9 only supports cortex-a53 and cortex-a57.
> Other
> > processor values for -mtune will get an error about "invalid parameter" for
> > gcc-4.9.
> >
> 
> What I would raise an error with Make via the architecture's Makefile.uk
> if the used GCC version is too old for a specific CPU mtune switch. The
> error should tell the user that a newer GCC version is required.
> 

That makes sense, I will add this patch to my series.

> > In this case, should we import the GCC version into Unikraft's build system?
> > If yes, we can provide different processor list for different GCC version.
> > Another method is to use a minimal set of processors (cortex-a53, 
> > cortex-a57)
> > to avoid such error. But we will not be able to optimize code for latest ARM
> > processors.
> >
> > I am not sure whether x86 has similar issue?
> >
> 
> Did not happen yet but might in the future, too.
> 
> > Regards,
> > Wei Chen
> >
> 
> Thanks,
> 
> Simon
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