Re: [PATCH] Add flags for powerpc in order to avoid exceptions

[Andrei Borzenkov <arvidjaar@gmail.com>]

В Sat, 27 Sep 2014 09:06:53 +0400
Andrei Borzenkov <arvidjaar@gmail.com> пишет:

> В Fri, 26 Sep 2014 16:29:40 -0300
> Paulo Flabiano Smorigo <pfsmorigo@linux.vnet.ibm.com> пишет:
> 
> > * conf/Makefile.common [COND_powerpc_ieee1275] (CFLAGS_PLATFORM): Add
> > -msoft-float -mno-vsx -mno-altivec.
> > 
> > Also-By: Adhemerval Zanella <azanella@linux.vnet.ibm.com>
> > ---
> >  ChangeLog            | 7 +++++++
> >  conf/Makefile.common | 3 +++
> >  2 files changed, 10 insertions(+)
> > 
> > diff --git a/ChangeLog b/ChangeLog
> > index 192e8bc..40eb90c 100644
> > --- a/ChangeLog
> > +++ b/ChangeLog
> > @@ -1,3 +1,10 @@
> > +2014-09-26  Paulo Flabiano Smorigo  <pfsmorigo@linux.vnet.ibm.com>
> > +
> > +	Add flags for powerpc in order to avoid exceptions
> > +
> > +	* conf/Makefile.common [COND_powerpc_ieee1275] (CFLAGS_PLATFORM): Add
> > +	-msoft-float -mno-vsx -mno-altivec.
> > +
> >  2014-09-25  Colin Watson  <cjwatson@ubuntu.com>
> >  
> >  	Fix in-tree --platform=none
> > diff --git a/conf/Makefile.common b/conf/Makefile.common
> > index 51fbaf9..57c491a 100644
> > --- a/conf/Makefile.common
> > +++ b/conf/Makefile.common
> > @@ -22,6 +22,9 @@ endif
> >  if COND_arm64
> >    CFLAGS_PLATFORM += -mcmodel=large
> >  endif
> > +if COND_powerpc_ieee1275
> > +  CFLAGS_PLATFORM += -msoft-float -mno-vsx -mno-altivec
> > +endif
> >  
> >  #FIXME: discover and check XEN headers
> >  CPPFLAGS_XEN = -I/usr/include
> 
> Thank you! I confirm that this patch works and does not break grub on
> earlier CPU :)
> 
> There are still differences in generated code, so we probably need to
> tune some more flags.

I looked at compiler options for PowerPC and I think instead of trying
to catch individual flags which may change with every release we should
simply force the most common platform by

+if COND_powerpc_ieee1275
+  CFLAGS_PLATFORM += -mcpu=powerpc -mtune=powerpc
+endif


This makes sure result is identical on every platform and provides most
generic code that is expected to run on every(?) system.

WDYT?