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Date: Fri, 10 Jun 2011 14:20:00 -0000
From: Richard Guenther <rguenther@suse.de>
To: Jason Merrill <jason@redhat.com>
Cc: Richard Guenther <richard.guenther@gmail.com>,	gcc-patches List <gcc-patches@gcc.gnu.org>
Subject: Re: RFA (fold): PATCH for c++/49290 (folding *(T*)(ar+10))
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On Fri, 10 Jun 2011, Jason Merrill wrote:

> On 06/10/2011 04:35 AM, Richard Guenther wrote:
> > I'm out of good suggestions ;)  You can do the same-qualifier matching
> > and simply have a mismatched array element vs. array-ref type.
> 
> But I need to allow different qualifiers, too.
> 
> > We could also argue that whoever calls fold_indirect_ref_1 with TYPE
> > that doesn't even have TYPE_MAIN_VARIANT (TREE_TYPE (TREE_TYPE (op0 (!)))
> > == TYPE_MAIN_VARIANT (type) is broken.
> 
> Right, I only want to fold if the main variants match.
> 
> > Thus we could argue that
> > even ignoring qualifiers is ok - but I'd be worried about folding
> > *((volatile int *)&a[0] + 1) to a[1] with lost volatile qualification.
> 
> Right.
> 
> It would be correct to fold it to
> 
> VIEW_CONVERT_EXPR<volatile int,a[1]>

No, it wouldn't be correct.  It isn't correct to fold it to an array-ref
that isn't volatile.

Richard.