Re: [Tinycc-devel] [ RFC] About packing two infos in a long v2

[robotux]

On Sat, 10 Nov 2012 16:33:33 +0100, Daniel Glöckner wrote:
> On Wed, Nov 07, 2012 at 04:18:00PM +0100, Thomas Preud'homme wrote:
> > Le mercredi 7 novembre 2012 16:09:51, Milutin Jovanović a écrit :
> > > Other then that, looks OK to me. BTW, I did not check correctness, 
> > just
> > > reviewed the style and logic.
> >
> > Don't worry for the correctness. GOT needs to be aligned on 4 bytes 
> > on ARM so
> > I know it's fine. I tested the code successfully on ARM and it 
> > yields the
> > correct result on my tests.
>
> Can we assume GOT entries are aligned to 2 bytes on all 
> architectures?

In fact currently in tcc, GOT entries are all at least 4 bytes aligned. 
Indeed, s1->got->data_offset is always incremented by PTR_SIZE which is 
4 or greater. Thus I could use the new structure unconditionnally and 
add a #if PTR_SIZE < 2 #error + a check in section_ptr_add to unsure we 
catch any changes of how GOT entries are aligned. That would make for a 
much smaller patch and more consistent situation.

Any thought people?

By the way, why is the following code used in fill_got_entry:

offset = get_got_offset(s1, sym_index);
section_reserve(s1->got, offset + PTR_SIZE);

when section_ptr_add(s1->got, PTR_SIZE) would have the same effect?

>   Daniel

Best regards,

Thomas