Subject: Re: [PATCH 1/2] powerpc/boot: Disable vector instructions

From: Segher Boessenkool <[email-masked]>
Date: Wed, 10 Oct 2018 17:05:09 -0500

On Thu, Oct 11, 2018 at 08:22:54AM +1030, Joel Stanley wrote:
> On Wed, 10 Oct 2018 at 22:41, Michael Ellerman <[email-masked]> wrote:
> > Joel Stanley <[email-masked]> writes:
> > >  BOOTCFLAGS    := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
> > > -              -fno-strict-aliasing -Os -msoft-float -pipe \
> > > -              -fomit-frame-pointer -fno-builtin -fPIC -nostdinc \
> > > +              -fno-strict-aliasing -Os -msoft-float -mno-altivec -mno-vsx \
> >
> > That's going to break if the compiler doesn't understand -mno-vsx isn't it?
> >
> > I'm not sure if "support" a compiler that old though.
> 
> Segher, the kernel mandates 4.6 as the minimum. Do we need to worry
> about the compiler not supporting  -mno-altivec -mno-vsx?

-mvsx is gcc 4.5 and later.
https://www.gnu.org/software/gcc/gcc-4.5/changes.html

-maltivec is...  Hrm, not so easy to find...  gcc 3.1 and later it seems.
https://www.gnu.org/software/gcc/gcc-3.1/changes.html

You should be fine.

Segher