From: Kai Tietz <ktietz70@googlemail.com>
To: Jason Merrill <jason@redhat.com>
Cc: Kai Tietz <ktietz@redhat.com>,
gcc-patches List <gcc-patches@gcc.gnu.org>
Subject: Re: C++ delayed folding branch review
Date: Mon, 03 Aug 2015 09:42:00 -0000 [thread overview]
Message-ID: <CAEwic4aQeu6c88q+RfZ=mGu6tObjzq9tWR4YgRnxCjk2PG=cXQ@mail.gmail.com> (raw)
In-Reply-To: <55BEE4CE.9070706@redhat.com>
2015-08-03 5:49 GMT+02:00 Jason Merrill <jason@redhat.com>:
> On 07/31/2015 05:54 PM, Kai Tietz wrote:
>>
>> The "STRIP_NOPS-requirement in 'reduced_constant_expression_p'" I could
>> remove, but for one case in constexpr. Without folding we don't do
>> type-sinking/raising.
>
>
> Right.
>
>> So binary/unary operations might be containing cast, which were in the
>> past unexpected.
>
>
> Why aren't the casts folded away?
On such cast constructs, as for this vector-sample, we can't fold away
the cast chain. The difference here to none-delayed-folding branch is
that the cast isn't moved out of the plus-expr. What we see now is
(plus ((vec) (const vector ...) { .... }), ...). Before we had (vec)
(plus (const vector ...) { ... }).
>> On verify_constant we check by reduced_constant_expression_p, if value is
>> a constant. We don't handle here, that NOP_EXPRs are something we want to
>> look through here, as it doesn't change anything if this is a constant, or
>> not.
>
>
> NOPs around constants should have been folded away by the time we get there.
Not in this cases, as the we actually have here a switch from const to
none-const. So there is an attribute-change, which we can't ignore in
general. But I agree that for constexpr's we could special case cast
from const to none-const (as required in expressions like const vec v
= v + 1).
> Jason
>
Kai
next prev parent reply other threads:[~2015-08-03 9:42 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-12 5:41 Jason Merrill
2015-06-12 16:17 ` Kai Tietz
2015-06-13 7:58 ` Jason Merrill
2015-07-27 19:01 ` Jason Merrill
2015-07-28 2:40 ` Kai Tietz
2015-07-28 20:35 ` Kai Tietz
2015-07-29 18:48 ` Jason Merrill
2015-07-29 23:03 ` Kai Tietz
2015-07-30 14:40 ` Kai Tietz
2015-07-30 18:41 ` Jason Merrill
2015-07-30 21:33 ` Kai Tietz
2015-07-31 0:43 ` Jason Merrill
2015-07-31 7:08 ` Jeff Law
2015-07-31 23:00 ` Kai Tietz
2015-08-03 3:49 ` Jason Merrill
2015-08-03 9:42 ` Kai Tietz [this message]
2015-08-03 15:39 ` Jason Merrill
2015-08-24 7:20 ` Kai Tietz
2015-08-27 2:57 ` Jason Merrill
2015-08-27 10:54 ` Kai Tietz
2015-08-27 13:35 ` Jason Merrill
2015-08-27 13:44 ` Kai Tietz
2015-08-27 18:15 ` Kai Tietz
2015-08-28 3:03 ` Jason Merrill
2015-08-28 7:43 ` Kai Tietz
2015-08-28 11:18 ` Kai Tietz
2015-08-28 2:12 ` Jason Merrill
2015-07-31 4:00 ` Jeff Law
2015-07-31 16:26 ` Jason Merrill
2015-07-31 16:43 ` Kai Tietz
2015-07-31 16:52 ` Jakub Jelinek
2015-07-31 16:53 ` Jason Merrill
2015-07-31 21:31 ` Kai Tietz
-- strict thread matches above, loose matches on Subject: below --
2015-04-24 4:23 Jason Merrill
2015-04-24 13:46 ` Kai Tietz
2015-04-24 18:25 ` Jason Merrill
2015-04-28 12:06 ` Kai Tietz
2015-04-28 13:57 ` Jason Merrill
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAEwic4aQeu6c88q+RfZ=mGu6tObjzq9tWR4YgRnxCjk2PG=cXQ@mail.gmail.com' \
--to=ktietz70@googlemail.com \
--cc=gcc-patches@gcc.gnu.org \
--cc=jason@redhat.com \
--cc=ktietz@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).