Joakim Tjernlund/Transmode wrote on 2010/10/12 11:00:36:
>
> Alan Modra <amo...@gmail.com> wrote on 2010/10/11 14:58:45:
> >
> > On Sun, Oct 10, 2010 at 11:20:06AM +0200, Joakim Tjernlund wrote:
> > > Now I have had a closer look at this and it looks much like -fpic
> > > on ppc32, you still use the GOT/TOC to load the address where the
data is.
> >
> > No, with ppc64 -mcmodel=medium you use the GOT/TOC pointer plus an
> > offset to address local data.
> >
> > > I was looking for true %pc relative addressing of data. I guess this
is really
> > > hard on PowerPC?
> >
> > Yes, PowerPC lacks pc-relative instructions.
> >
> > > I am not sure this is all it takes to make -fpic to work with
-mrelocatable,
> > > any ideas?
> >
> > You might be lucky. With -mrelocatable, .got2 only contains
> > addresses. No other constants. So a simple run-time loader can
> > relocate the entire .got2 section, plus those locations specified in
> > .fixup. You'll have to make sure gcc does the same for .got, and your
> > run-time loader will need to be modified to handle .got (watch out for
> > the .got header!).
> Got it working now. It was just u-boot reloc routine I first failed
> to extend properly to reloc *got too.
>
> I think this is safe as one can mix fpic with fPIC and
> mrelocatable is the same as fPIC+fixups.
>
> Will you accept this patch into gcc?
Ping?
>From d8ff0b3f0b44480542eab04d1659f4368b6b09cf Mon Sep 17 00:00:00 2001
From: Joakim Tjernlund <joakim.tjernl...@transmode.se>
Date: Sun, 10 Oct 2010 10:34:50 +0200
Subject: [PATCH] powerpc: Support -fpic too with mrelocatable
Signed-off-by: Joakim Tjernlund <joakim.tjernl...@transmode.se>
---
sysv4.h | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)
diff --git a/gcc/config/rs6000/sysv4.h b/gcc/config/rs6000/sysv4.h
index 8da8410..e4b8280 100644
--- a/gcc/config/rs6000/sysv4.h
+++ b/gcc/config/rs6000/sysv4.h
@@ -227,7 +227,8 @@ do { \
} \
\
else if (TARGET_RELOCATABLE) \
- flag_pic = 2; \
+ if (!flag_pic) \
+ flag_pic = 2; \
} while (0)
#ifndef RS6000_BI_ARCH
--
1.7.2.2
