Re: bfd_perform_relocation() and split fields

[Eric DeVolder <devolder at evsx dot com>]

Ian Lance Taylor wrote:

>    Date: Wed, 17 Nov 1999 08:49:20 -0600
>    From: Eric DeVolder <devolder@evsx.com>
>
>    > The CPU specific hook is already there: the special_function field in
>    > the howto structure.  Just make that do whatever you need your
>    > relocation to do.
>
>    The call to special_function occurs way too early in bfd_perform_relocation().
>    There are several statements that perform calculations or modify reloc_entry
>    that would not be able to "preserve" a split-field value all the way thru to
>    where the bits are actually placed back into the insn. What I'm suggesting is
>    a hook right before the switch(howto-size) statement that gives you a chance
>    to munge the reloc value before it gets inserted.
>
> Just do all that stuff in your special_function code.  You won't need
> most of it anyhow; most of what bfd_perform_relocation does is pretty
> bogus.

Doug Evans pointed me to the sparc reloc/howtos (specifically WDISP16) and this
confirms what you've just stated. I will proceed using the special_function approach.

> I would not accept a patch which added a new hook when you could just
> use the existing special_function hook instead.
>
>    > Note that in the ``new'' linker approach, bfd_perform_relocation is
>    > not used while linking.
>
>    I'm not familiar with this...is there a pointer available? or email thread?
>
> See the top of bfd/linker.c.

Thanks,
Eric

>
>
> Ian