Re: [PATCH v2] raid6/ppc: Fix build for clang

[Joel Stanley]

On Tue, 4 Dec 2018 at 05:15, Nick Desaulniers <ndesaulniers@xxxxxxxxxx> wrote:
> > > > +ifdef CONFIG_CC_IS_CLANG
> > > > +# clang ppc port does not yet support -maltivec when -msoft-float is
> > > > +# enabled. A future release of clang will resolve this
> > > > +# https://bugs.llvm.org/show_bug.cgi?id=31177
> > > > +CFLAGS_REMOVE_altivec1.o  += -msoft-float
> > > > +CFLAGS_REMOVE_altivec2.o  += -msoft-float
> > > > +CFLAGS_REMOVE_altivec4.o  += -msoft-float
> > > > +CFLAGS_REMOVE_altivec8.o  += -msoft-float
> > > > +CFLAGS_REMOVE_altivec8.o  += -msoft-float
> > > > +CFLAGS_REMOVE_vpermxor1.o += -msoft-float
> > > > +CFLAGS_REMOVE_vpermxor2.o += -msoft-float
> > > > +CFLAGS_REMOVE_vpermxor4.o += -msoft-float
> > > > +CFLAGS_REMOVE_vpermxor8.o += -msoft-float
> > > > +endif
> > >
> > > Hi Joel, thanks for this patch!  My same thoughts about
> > > CONFIG_CC_IS_CLANG vs cc-option from
> > > https://lists.ozlabs.org/pipermail/linuxppc-dev/2018-November/180939.html
> > > apply here as well.  I don't feel strongly about either though.  What
> > > are your thoughts?
> >
> > I'm not sure that we can test for this one with cc-option. The result
> > of having -maltivec with -msoft-float is a error about the internals
> > of clang, which isn't something that kbuild is set up to test for.
>
> As in clang itself crashes, and cc-option/kbuild can't handle that gracefully?

The developer gets something like this:

SplitVectorResult #0: t196: v16i8 = llvm.ppc.altivec.vcmpgtsb
TargetConstant:i64<4823>, t146, t195
fatal error: error in backend: Do not know how to split the result of
this operator!
clang-8: error: clang frontend command failed with exit code 70 (use
-v to see invocation)

>
> >
> > When clang is fixed to allow this combination we will still build this
> > code in the same way, so in that sense it fails "open".
> >