32-bit PowerPC sdata linker problem

[Alan Modra]

On Fri, Jun 06, 2014 at 01:31:48PM +0200, Sebastian Huber wrote:
> On 2014-06-06 13:23, Sebastian Huber wrote:
> >Ok, so this "cmplwi cr0, rX, ppc_exc_lock_std@sdarel" is illegal, since
> >ppc_exc_lock_std@sdarel is signed and the immediate is unsigned 16-bit?  The
> >assembler doesn't issue a warning about this.
> >
> >Exists there a way to rescue this cmplwi hack without relaxing the overflow
> >checks?
> 
> Hm, sorry, it was surprisingly simple.  This works:
> 
> "cmplwi cr0, rX, ppc_exc_lock_std@sdarel@l"
> 
> I was not aware that you can add several @ in a row.

That is the wrong thing to use here.  sdarel@l translates to a VLE
reloc which applies to a split 16-bit field in VLE insns.

You want
 cmpwi cr0, rX, ppc_exc_lock_std@sdarel
to properly compare a 16-bit signed number from sym@sdarel.

Note that the assembler does error if you write something like
 cmplwi 3,-30000
or
 cmpwi 3,40000
so what the linker is now doing is extending this behaviour to link
time.

-- 
Alan Modra
Australia Development Lab, IBM