From: "Winalski, Paul" <paul.winalski@intel.com>
To: "'Steve Ellcey'" <sje@cup.hp.com>, gcc@gcc.gnu.org, rth@redhat.com
Subject: RE: gcc and the IA64 ABI
Date: Wed, 28 May 2003 15:12:00 -0000 [thread overview]
Message-ID: <A5974D8E5F98D511BB910002A50A6647065013C7@hdsmsx103.hd.intel.com> (raw)
Actually, I was speaking about our (Intel's) compiler, not gcc.
-Paul W.
-----Original Message-----
From: Steve Ellcey [mailto:sje@cup.hp.com]
Sent: Friday, May 23, 2003 4:36 PM
To: Winalski, Paul; gcc@gcc.gnu.org; rth@redhat.com
Subject: RE: gcc and the IA64 ABI
> > But eliminating caller gp save/restore
> > seems to be promising. Early testing seems to indicate significant
> > improvement on some important programs; we're still in the process of
> > collecting performance data.
>
> I wouldn't have suspected that this would produce that much of a win,
> given that restoring the gp is so cheap; just a single mov instruction.
I wonder if the speed up is you are seeing is due to a side-effect of
how the GP is saved and restored. GCC on IA64 was (is?) using a single
register to save/restore gp and it always used the same register. This
made otherwise loop invariant function calls (like integer division with
loop invariant arguments) look like they were never loop-invariant and
could not be moved out of the loop, especially when there were multiple
divisions (all loop invariant) in one loop. See
http://gcc.gnu.org/ml/gcc-patches/2002-03/msg00179.html for a change I
proposed that allowed loop invariant code motion of calls, this change
was not checked in and I believe this situation still exists in 3.3. It
may have been fixed on the top-of-tree as the way calls are expanded has
been changed and the routine ia64_gp_save_reg no longer exists. See
http://gcc.gnu.org/ml/gcc-patches/2003-03/msg01196.html for where that
was removed by Richard Henderson.
Steve Ellcey
sje@cup.hp.com
next reply other threads:[~2003-05-28 14:38 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-05-28 15:12 Winalski, Paul [this message]
-- strict thread matches above, loose matches on Subject: below --
2003-05-23 20:38 Steve Ellcey
[not found] <A5974D8E5F98D511BB910002A50A6647065013B8@hdsmsx103.hd.intel.com>
2003-05-23 19:09 ` Richard Henderson
2003-05-23 18:41 Winalski, Paul
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=A5974D8E5F98D511BB910002A50A6647065013C7@hdsmsx103.hd.intel.com \
--to=paul.winalski@intel.com \
--cc=gcc@gcc.gnu.org \
--cc=rth@redhat.com \
--cc=sje@cup.hp.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).