[PATCH] 32-bit PowerPC ELF Position Independent Code

[Hal Finkel]

----- Original Message -----
> From: "Bill Schmidt" <wschmidt at linux.vnet.ibm.com>
> To: "Justin Hibbits" <chmeeedalf at gmail.com>
> Cc: llvm-commits at cs.uiuc.edu
> Sent: Wednesday, July 16, 2014 7:33:58 AM
> Subject: Re: [PATCH] 32-bit PowerPC ELF Position Independent Code
> 
> On Wed, 2014-07-16 at 07:10 -0500, Bill Schmidt wrote:
> > Hi Justin,
> > 
> > On Tue, 2014-07-15 at 22:36 -0700, Justin Hibbits wrote:
> > 
> > > Thanks for reviewing the code.  I think I've addressed all your
> > > comments, including adding a few rudimentary tests for it.  I've
> > > attached the most recent patch for review.  I hope this can get
> > > in
> > > before the 3.5 branch, so will also be looking for somebody with
> > > commit privileges to do the honors.
> > 
> > Thanks for the changes.  You did address all the changes but one:
> >  I'm
> > still unsure why you are using .got2 rather than .got.  Can you
> > please
> > explain?  In the end it's no skin off my back if you want to keep
> > the
> > redundant PLT stubs, as I don't have any investment in 32-bit
> > efficiency; so this isn't a showstopper for me, but others may
> > care.
> > This may be the right thing for you, but it would be good to
> > understand
> > why.
> 
> Justin had actually clarified this in IRC overnight, but I didn't see
> the message until now.  He uses .got2 because this is what he sees
> from
> GCC.  Justin, this is a fine reason, but I suggest that you follow up
> with Alan Modra to see whether GCC always uses this or whether this
> behavior depends on any options.  This is no reason to hold up the
> patch, though.

Okay, thanks. I'll look at this today.

 -Hal

> 
> Thanks,
> Bill
> 
> > 
> > The tests are a good start.  You should also have a test that
> > demonstrates the use of R30 as GOT base when accessing a global,
> > and a
> > test that demonstrates the use of R29 as the base register when
> > needed.
> > There are probably existing tests that you can modify for these
> > purposes, though I can't point to them offhand.
> > 
> > I'm constrained by company policy from committing patches on behalf
> > of
> > others except in urgent circumstances, so I hope one of the other
> > PPC32-interested folks will be willing to step up here once the
> > patch is
> > complete.
> > 
> > Thanks,
> > Bill
> > 
> > > 
> > > Thanks,
> > > Justin
> > 
> > 
> > _______________________________________________
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> > llvm-commits at cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
> > 
> 
> 
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-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory