Re: [PATCH] powerpc64: Implement TLS using PC-relative addressing

[Alan Modra <amodra@gmail.com>]

On Thu, Oct 01, 2020 at 10:49:43AM +0200, Florian Weimer wrote:
> * Tulio Magno Quites Machado Filho via Libc-alpha:
> 
> > diff --git a/sysdeps/powerpc/mod-tlsopt-powerpc.c b/sysdeps/powerpc/mod-tlsopt-powerpc.c
> > index ee0db12a73..5856dab60b 100644
> > --- a/sysdeps/powerpc/mod-tlsopt-powerpc.c
> > +++ b/sysdeps/powerpc/mod-tlsopt-powerpc.c
> > @@ -24,7 +24,14 @@ tls_get_addr_opt_test (void)
> >    tls_index *tls_arg;
> >  #ifdef __powerpc64__
> >    register unsigned long thread_pointer __asm__ ("r13");
> > +  /* PC-relative addressing is available when compiling with -mpcrel.
> > +     The first releases of GCC 10 do support -mpcrel, but do not export
> > +     __PCREL__.  */
> > +# if defined(__PCREL__) || __GNUC__ <= 10 && defined(_ARCH_PWR10)
> > +  asm ("pla %0,foo@got@tlsgd@pcrel" : "=r" (tls_arg));
> > +# else
> >    asm ("addi %0,2,foo@got@tlsgd" : "=r" (tls_arg));
> > +# endif
> 
> Should this check for binutils support for @pcrel?  Or won't GCC enable
> _ARCH_PWR10 in this case?

Right, gcc doesn't support power10 without the requisite binutils
support.  In any case, this file is only used when running the
testsuite so it hardly seems worth the bother of configure checks.
The patch looks good to me.

-- 
Alan Modra
Australia Development Lab, IBM