Re: [commit] Use -mabi=altivec for AltiVec tests

["Ulrich Weigand" <uweigand@de.ibm.com>]

Daniel Jacobowitz wrote:

> I don't think this is a good idea.  -mabi=altivec is an ABI-changing
> option; you're supposed to match the ABI of your system libraries.
> It will work out OK in practice though since the stack alignment is
> already large enough on powerpc-linux.

Sorry, I didn't consider this controversial, or I would have posted an RFC
first ...  I understand it to be general practice to use -mabi=altivec
with applications on Linux, and that should be OK as long as no system
library interface using vector arguments is used.  Is this a problem
in other environments?

However, if you prefer, I certainly have no objections to reverting the
patch (or maybe restricting it to Linux only) ...

> I committed a GCC HEAD patch several weeks ago to mark the vector ABI of
> PowerPC object files.  I also posted a linker patch to propogate this
> into linked objects and I have the matching patch to GDB to
> auto-detect the correct ABI and support both in GDB.  That also
> fixes this test.

Supporting both ABIs in GDB is certainly a good thing.  However, the
point of this test case is to verify that GDB implements the AltiVec
ABI correctly, so IMO we really want to exercise that code path, not
bypass it.  In fact, if we support both ABIs in GDB, we probably want
to run the test twice, once compiled with -mabi=altivec and once with
-mabi=no-altivec ...

> Unfortunately the linker patch is hung up right now because it notices
> this same dubious action (linking -mabi=altivec and -mabi=no-altivec
> code) and warns about it.  That causes a bunch of GCC testcase
> failures.  The GCC testcases in question use, but do not actually
> need, -mabi=altivec; they just need a nasty bug in -maltivec
> -mabi=no-altivec fixed and my patch for that didn't get any comments
> :-(

Can you point me to the patch in question?  Maybe I can ping David ...

Bye,
Ulrich

-- 
  Dr. Ulrich Weigand
  GNU Toolchain for Linux on System z and Cell BE
  Ulrich.Weigand@de.ibm.com