--target=powerpc64-linux_altivec: Use rs6000_linux64_override_options()?

--target=powerpc64-linux_altivec: Use rs6000_linux64_override_options()?

[Jan-Benedict Glaw]

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Hi!

While checking my bot build logs, I noticed that GCC configured for
--target=powerpc64-linux_altivec will pull in linux64.h and
linuxaltivec.h .

linux64.h
  * Will "#define TARGET_USES_LINUX64_OPT 1" (to make static void
    rs6000_linux64_override_options() available in rs6000.cc).
  * Will "#define SUBSUBTARGET_OVERRIDE_OPTIONS" to use
    rs6000_linux64_override_options().

linuxaltivec.h OTOH
  * Will undef / "#define SUBSUBTARGET_OVERRIDE_OPTIONS  rs6000_altivec_abi = 1"
    and thus no longer use rs6000_linux64_override_options()
  * That triggers a warning (unused-function).

To silence that warning, should linuxaltivec.h undefine
TARGET_USES_LINUX64_OPT? Or set rs6000_altivec_abi=1 and call
rs6000_linux64_override_options()?

Thanks,
  Jan-Benedict

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Re: --target=powerpc64-linux_altivec: Use rs6000_linux64_override_options()?

[Segher Boessenkool]

Hi!

On Fri, Oct 28, 2022 at 07:34:24PM +0200, Jan-Benedict Glaw wrote:
> While checking my bot build logs, I noticed that GCC configured for
> --target=powerpc64-linux_altivec will pull in linux64.h and
> linuxaltivec.h .
> 
> linux64.h
>   * Will "#define TARGET_USES_LINUX64_OPT 1" (to make static void
>     rs6000_linux64_override_options() available in rs6000.cc).
>   * Will "#define SUBSUBTARGET_OVERRIDE_OPTIONS" to use
>     rs6000_linux64_override_options().
> 
> linuxaltivec.h OTOH
>   * Will undef / "#define SUBSUBTARGET_OVERRIDE_OPTIONS  rs6000_altivec_abi = 1"
>     and thus no longer use rs6000_linux64_override_options()
>   * That triggers a warning (unused-function).
> 
> To silence that warning, should linuxaltivec.h undefine
> TARGET_USES_LINUX64_OPT? Or set rs6000_altivec_abi=1 and call
> rs6000_linux64_override_options()?

Why do you use powerpc64-linux_altivec?  This things (normally spelled
with a dash, not and underscore, btw) was made for 32-bit targets.  It
never has done anything useful for 64-bit targets, afaik?

(And not for 32-bit targets either really, but that is another issue.)


Segher

Re: --target=powerpc64-linux_altivec: Use rs6000_linux64_override_options()?

[Jan-Benedict Glaw]

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Hi!

On Fri, 2022-10-28 14:19:10 -0500, Segher Boessenkool <segher@kernel.crashing.org> wrote:
> On Fri, Oct 28, 2022 at 07:34:24PM +0200, Jan-Benedict Glaw wrote:
> > While checking my bot build logs, I noticed that GCC configured for
> > --target=powerpc64-linux_altivec will pull in linux64.h and
> > linuxaltivec.h .
> > 
> > linux64.h
> >   * Will "#define TARGET_USES_LINUX64_OPT 1" (to make static void
> >     rs6000_linux64_override_options() available in rs6000.cc).
> >   * Will "#define SUBSUBTARGET_OVERRIDE_OPTIONS" to use
> >     rs6000_linux64_override_options().
> > 
> > linuxaltivec.h OTOH
> >   * Will undef / "#define SUBSUBTARGET_OVERRIDE_OPTIONS  rs6000_altivec_abi = 1"
> >     and thus no longer use rs6000_linux64_override_options()
> >   * That triggers a warning (unused-function).
> > 
> > To silence that warning, should linuxaltivec.h undefine
> > TARGET_USES_LINUX64_OPT? Or set rs6000_altivec_abi=1 and call
> > rs6000_linux64_override_options()?
> 
> Why do you use powerpc64-linux_altivec?  This things (normally spelled
> with a dash, not and underscore, btw) was made for 32-bit targets.  It
> never has done anything useful for 64-bit targets, afaik?

Because it's listed in ./contrib/config-list.mk:

/var/cache/git/gcc [master] # make -f contrib/config-list.mk show | tr ' ' $'\n' | grep altivec
powerpc-eabisimaltivec
powerpc-eabialtivec
powerpc64-linux_altivec

> (And not for 32-bit targets either really, but that is another issue.)

It seems to be on the target list since the very beginning, when
config-list.mk was created by Joern Rennecke. So somebody cared about
this configuration I guess?

  If this configuration isn't ment to be used, we'd just drop it from
the list I guess.

MfG, JBG

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Re: --target=powerpc64-linux_altivec: Use rs6000_linux64_override_options()?

[Segher Boessenkool]

On Fri, Oct 28, 2022 at 10:07:41PM +0200, Jan-Benedict Glaw wrote:
> On Fri, 2022-10-28 14:19:10 -0500, Segher Boessenkool <segher@kernel.crashing.org> wrote:
> > Why do you use powerpc64-linux_altivec?  This things (normally spelled
> > with a dash, not and underscore, btw) was made for 32-bit targets.  It
> > never has done anything useful for 64-bit targets, afaik?
> 
> Because it's listed in ./contrib/config-list.mk:
> 
> /var/cache/git/gcc [master] # make -f contrib/config-list.mk show | tr ' ' $'\n' | grep altivec
> powerpc-eabisimaltivec
> powerpc-eabialtivec
> powerpc64-linux_altivec

Huh.  Okay, that is a bug.  Has that target ever worked (or
alternatively, has it ever existed at all, other than it is recognised
by config.gcc by not very tight REs)?

> It seems to be on the target list since the very beginning, when
> config-list.mk was created by Joern Rennecke. So somebody cared about
> this configuration I guess?

No idea.  rs6000_altivec_abi is always forced on on any linux
configuration that has VMX or VSX or 64 bit enabled:
===
  /* The AltiVec ABI is the default for PowerPC-64 GNU/Linux.  For
     PowerPC-32 GNU/Linux, -maltivec implies the AltiVec ABI.  It can
     be explicitly overridden in either case.  */
  if (TARGET_ELF)
    {
      if (!OPTION_SET_P (rs6000_altivec_abi)
          && (TARGET_64BIT || TARGET_ALTIVEC || TARGET_VSX))
        {
          if (main_target_opt != NULL &&
              !main_target_opt->x_rs6000_altivec_abi)
            error ("target attribute or pragma changes AltiVec ABI");
          else
            rs6000_altivec_abi = 1;
        }
    }
===

>   If this configuration isn't ment to be used, we'd just drop it from
> the list I guess.

Yeah, the config makes no sense.

Thanks,


Segher