From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-316091-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 27247 invoked by alias); 26 Apr 2010 14:43:30 -0000
Received: (qmail 27098 invoked by uid 48); 26 Apr 2010 14:43:04 -0000
Date: Mon, 26 Apr 2010 14:43:00 -0000
Message-ID: <20100426144304.27096.qmail@sourceware.org>
X-Bugzilla-Reason: CC
References: <bug-43892-19087@http.gcc.gnu.org/bugzilla/>
Subject: [Bug rtl-optimization/43892] PowerPC suboptimal "add with carry" optimization
In-Reply-To: <bug-43892-19087@http.gcc.gnu.org/bugzilla/>
Reply-To: gcc-bugzilla@gcc.gnu.org
To: gcc-bugs@gcc.gnu.org
From: "rguenth at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>
Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm
Precedence: bulk
List-Id: <gcc-bugs.gcc.gnu.org>
List-Archive: <http://gcc.gnu.org/ml/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-help@gcc.gnu.org>
Sender: gcc-bugs-owner@gcc.gnu.org
X-SW-Source: 2010-04/txt/msg02731.txt.bz2



------- Comment #5 from rguenth at gcc dot gnu dot org  2010-04-26 14:43 -------
(In reply to comment #4)
> Subject: Re:  PowerPC suboptimal "add with carry" optimization
> 
> "dje at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org> wrote on 2010/04/26
> 15:53:01:
> >
> > ------- Comment #3 from dje at gcc dot gnu dot org  2010-04-26 13:52 -------
> > As Jakub mentioned, i386.md implements the addcc named pattern and rs6000.md
> > does not provide that named pattern yet.
> 
> Will that also address the loop optimization? I don't think so.

No.

Actually compilable testcase:

typedef unsigned int u32;

u32
add32carry(u32 sum, u32 x)
{
  u32 z = sum + x;
  if (sum + x < x)
    z++;
  return z;
}

u32
loop(u32 *buf, int len)
{
  u32 sum = 0;
  for(; len; --len)
    sum = add32carry(sum, *++buf);
  return sum;
}


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43892