Re: [patch] Pushing Inferior Function Arguments onto Stack on PowerPC64 machines

[janani@linux.ibm.com]

Thanks for all the feedback. Will try to write up the fix along the  
lines which Daniel mentioned and post to the list.

Janani

Daniel Jacobowitz <drow@false.org> wrote on 10/04/2006 03:52:21 PM:

> On Wed, Oct 04, 2006 at 04:43:04PM -0400, David Edelsohn wrote:
> > >>>>> Daniel Jacobowitz writes:
> > > >> From reading the PPC64 Platform ABI  at
> > >> http://www.freestandards.org/spec/ELF/ppc64/PPC-elf64abi-1.9.html
> > >> ( see section 3.1.7)  it appears that on Big Endian machines,
> > >> values are  left aligned. But looks like GCC has different  
> rules and right
> > >> aligns the values which are put on the
> > >> registers. This matches  Andrew Cagney  comment in the code,  
> that says that
> > >> ABI specifies that the values
> > >> should be left aligned. But like I said in my earlier note,  
> GCCappears to
> > >> want the values to be
> > >> right aligned.  Would appreciate another set of eyes looking at it as I
> > >> don't have too much experience
> > >> in this area.
> > >    The PPC64 Linux ABI changed.  AIX always pads upwards.  PPC64
> > Linux pads aggregates smaller than a doubleword downward.
> > > "An aggregate or union smaller than one doubleword in size is padded so
> > that it appears in the least significant bits of the doubleword.  All
> > others are padded, if necessary, at their tail."
>
> Thank you (and thanks to Andreas for answering, too).
>
> In that case, the Linux and AIX configurations ought to be calling
> different functions here.  Janani, if you want to try to fix this,
> I would recommend:
>
>   - Rename the existing function.  Add an argument to it, is_linux.
>   - Create a wrapper function with the old name, in the same file,
>     for AIX to use.
>   - Create a wrapper function in ppc-linux-tdep.c which calls it with
>     is_linux == 1.
>   - Call set_gdbarch_push_dummy_call in the PPC64 section of
>     ppc_linux_init_abi.
>
> -- 
> Daniel Jacobowitz
> CodeSourcery