From: Richard Henderson <rth@redhat.com>
To: Sergey Ostanevich <sergos.gnu@gmail.com>
Cc: Richard Guenther <rguenther@suse.de>,
Uros Bizjak <ubizjak@gmail.com>,
gcc-patches@gcc.gnu.org, "H.J. Lu" <hjl.tools@gmail.com>
Subject: Re: [PATCH i386] PR47698 no CMOV for volatile mem
Date: Fri, 28 Oct 2011 16:07:00 -0000 [thread overview]
Message-ID: <4EAACF6C.1000104@redhat.com> (raw)
In-Reply-To: <CAGYS_TKCCRgaG8U6-=77imhBG7JmNtUN=bYoZX7b1ajYDQPZhQ@mail.gmail.com>
On 10/28/2011 05:49 AM, Sergey Ostanevich wrote:
> - the code for CMOV is under #ifdef in the mddle-end, which is
> explicitly marked as "have to be removed" (ifcvt.c:1446)
> - I have no clear evidence all platforms that support conditional move
> have the same semantics that lead to the PR
We're on solid ground here. The arguments are assumed to always be
evaluated in RTL, *except* in the case of COND_EXEC. Only true
predication can avoid an exception or side effects of touching memory.
> I think the best way to address both concerns is to implement code
> that relies on а new hookup "volatile-safe CMOV" that is false by
> default.
We do not need a new hook.
r~
next prev parent reply other threads:[~2011-10-28 15:51 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-27 19:47 Uros Bizjak
2011-10-28 8:49 ` Richard Guenther
2011-10-28 13:25 ` Sergey Ostanevich
2011-10-28 13:39 ` Richard Guenther
2011-10-28 15:49 ` Sergey Ostanevich
2011-10-28 21:55 ` Sergey Ostanevich
2011-11-02 11:55 ` Richard Guenther
2011-11-06 18:48 ` Sergey Ostanevich
2011-11-07 21:00 ` Eric Botcazou
2011-10-28 16:07 ` Richard Henderson [this message]
-- strict thread matches above, loose matches on Subject: below --
2011-10-27 13:04 Sergey Ostanevich
2011-10-28 1:44 ` Richard Henderson
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=4EAACF6C.1000104@redhat.com \
--to=rth@redhat.com \
--cc=gcc-patches@gcc.gnu.org \
--cc=hjl.tools@gmail.com \
--cc=rguenther@suse.de \
--cc=sergos.gnu@gmail.com \
--cc=ubizjak@gmail.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).