Fix verifier ICE on CLOBBER of COMPONENT_REF

[Jan Hubicka]

> On Mon, 1 Jul 2019, Jan Hubicka wrote:
> 
> > Hi,
> > the testcase makes inliner to substitute RESULT_DECL by COMPONENT_REF
> > inside CLOBBER statement. This is not allowed and leads to ICE in
> > verifier (while I think we should fix code to support this).
> > This patch simply makes inliner to watch for this case and do not remap
> > the statement at all.
> > 
> > The testcase works for 32bit only which is bit unfortunate. For 64bit
> > build NRV does not happen, i did not look into why.
> > 
> > OK?
> 
> Hmm, a bit ugly and seemingly in a "wrong place" but I cannot think
> of a better solution.
> 
> Thus OK.
> 
> We indeed might reconsider the CLOBBER restriction - it's from
> the time they were used for stack slot sharing but now they are
> re-purposed...

Agreed, I think we want to relax the restriction - it is useful to kill
part of structure.  But I will go with the fix first :)

Honza