From: Richard Guenther <richard.guenther@gmail.com>
To: Jason Merrill <jason@redhat.com>
Cc: Richard Guenther <rguenther@suse.de>,
gcc-patches List <gcc-patches@gcc.gnu.org>, GCC <gcc@gcc.gnu.org>
Subject: Re: Is VIEW_CONVERT_EXPR an lvalue? (was Re: RFA (fold): PATCH for c++/49290 (folding *(T*)(ar+10)))
Date: Sun, 12 Jun 2011 13:18:00 -0000 [thread overview]
Message-ID: <BANLkTin8o9=mfL80u_MaWMSDyCYa61vdpQ@mail.gmail.com> (raw)
In-Reply-To: <4DF3C98B.6070006@redhat.com>
On Sat, Jun 11, 2011 at 10:01 PM, Jason Merrill <jason@redhat.com> wrote:
> On 06/10/2011 10:20 AM, Richard Guenther wrote:
>>
>> no, a VIEW_CONVERT_EXPR is generally not an lvalue (fold for example
>> would turn the above to (volatile int) a[1]).
>
> The gimplifier seems to consider it an lvalue: gimplify_expr uses
> gimplify_compound_lval for it, and gimplify_addr_expr handles taking its
> address. And get_inner_reference handles it. So I think fold should be
> changed, and we should clarify that VIEW_CONVERT_EXPR is an lvalue.
>
> If not, we need a new tree code for treating an lvalue as an lvalue of a
> different type without having to take its address; that's what I thought
> VIEW_CONVERT_EXPR was for.
The please provide a specification on what a VIEW_CONVERT_EXPR does
to type-based alias analysis. We are trying to avoid that by the rvalue rule.
Also you can always avoid VIEW_CONVERT_EXPRs for lvalues by simply
moving the conversion to the rvalue side.
Yes, we do handle lvalue VIEW_CONVERT_EXPRs, but that is for Ada
which uses it for aggregates. I don't want us to add more lvalue
VIEW_CONVERT_EXPR
cases, especially not for register types.
Richard.
> Jason
>
next prev parent reply other threads:[~2011-06-12 11:00 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-07 5:39 RFA (fold): PATCH for c++/49290 (folding *(T*)(ar+10)) Jason Merrill
2011-06-07 10:20 ` Richard Guenther
2011-06-07 10:27 ` Jakub Jelinek
2011-06-07 12:03 ` Richard Guenther
2011-06-07 12:22 ` Richard Guenther
2011-06-07 13:46 ` Michael Matz
2011-06-07 13:49 ` Richard Guenther
2011-06-07 13:55 ` Jason Merrill
2011-06-07 14:05 ` Richard Guenther
2011-06-07 14:24 ` Jason Merrill
2011-06-09 19:47 ` Jason Merrill
2011-06-10 8:53 ` Richard Guenther
2011-06-10 14:03 ` Jason Merrill
2011-06-10 14:20 ` Richard Guenther
2011-06-10 14:32 ` Jason Merrill
2011-06-10 14:34 ` Richard Guenther
2011-06-10 14:45 ` Jason Merrill
2011-06-11 18:24 ` Mike Stump
2011-06-12 11:03 ` Richard Guenther
2011-06-13 7:29 ` Mike Stump
2011-06-13 12:46 ` Richard Guenther
2011-06-14 20:31 ` Mike Stump
2011-06-15 9:54 ` Richard Guenther
2011-06-15 18:57 ` Mike Stump
2011-06-16 7:39 ` Richard Guenther
2011-06-17 14:17 ` Michael Matz
2011-06-20 10:24 ` Richard Guenther
2011-06-12 7:58 ` Is VIEW_CONVERT_EXPR an lvalue? (was Re: RFA (fold): PATCH for c++/49290 (folding *(T*)(ar+10))) Jason Merrill
2011-06-12 13:18 ` Richard Guenther [this message]
2011-06-12 13:22 ` Richard Guenther
2011-06-13 6:12 ` Mike Stump
2011-06-12 22:42 ` Jason Merrill
2011-06-13 12:44 ` Richard Guenther
2011-06-13 17:59 ` RFA (fold): PATCH for c++/49290 (folding *(T*)(ar+10)) Jason Merrill
2011-06-14 9:10 ` Richard Guenther
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