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Date: Fri, 28 Oct 2022 16:13:04 -0500
From: Segher Boessenkool <segher@kernel.crashing.org>
To: Jan-Benedict Glaw <jbglaw@lug-owl.de>
Cc: Aldy Hernandez <aldyh@redhat.com>, David Edelsohn <dje.gcc@gmail.com>,
        Kewen Lin <linkw@gcc.gnu.org>, gcc@gcc.gnu.org
Subject: Re: --target=powerpc64-linux_altivec: Use rs6000_linux64_override_options()?
Message-ID: <20221028211304.GF25951@gate.crashing.org>
References: <20221028173424.vxsqkj6wf2k3inoa@lug-owl.de> <20221028191910.GE25951@gate.crashing.org> <20221028200741.dau6ut2edeq5cusw@lug-owl.de>
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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