From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-363211-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 18975 invoked by alias); 20 Jul 2011 17:48:16 -0000
Received: (qmail 18966 invoked by uid 22791); 20 Jul 2011 17:48:15 -0000
X-SWARE-Spam-Status: No, hits=-2.8 required=5.0	tests=ALL_TRUSTED,AWL,BAYES_00,TW_GJ
X-Spam-Check-By: sourceware.org
Received: from localhost (HELO gcc.gnu.org) (127.0.0.1)    by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Wed, 20 Jul 2011 17:48:02 +0000
From: "gjl at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/33970] Missed optimization using unsigned char loop variable
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: middle-end
X-Bugzilla-Keywords: missed-optimization
X-Bugzilla-Severity: enhancement
X-Bugzilla-Who: gjl at gcc dot gnu.org
X-Bugzilla-Status: RESOLVED
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: 4.7.0
X-Bugzilla-Changed-Fields: Status CC Resolution Target Milestone Known to fail
Message-ID: <bug-33970-4-Td6yeFxSAT@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-33970-4@http.gcc.gnu.org/bugzilla/>
References: <bug-33970-4@http.gcc.gnu.org/bugzilla/>
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
Content-Type: text/plain; charset="UTF-8"
MIME-Version: 1.0
Date: Wed, 20 Jul 2011 17:48:00 -0000
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: 2011-07/txt/msg01695.txt.bz2

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33970

Georg-Johann Lay <gjl at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |gjl at gcc dot gnu.org
         Resolution|                            |WORKSFORME
   Target Milestone|---                         |4.7.0
      Known to fail|                            |

--- Comment #13 from Georg-Johann Lay <gjl at gcc dot gnu.org> 2011-07-20 17:47:44 UTC ---
Cloased as WORKS FOR ME.

Using the following test case:


volatile unsigned char bar;

void foo(void)
{
    unsigned char x;
    for(x=0;x<128; x++)
    {
        bar = x;
    }
}

int sub2 (unsigned char);

void foo2 (void)
{
    unsigned char x;
    for(x=0;x<128; x++)
    {
        sub2 (x);
    }
}

void foo21 (void)
{
    unsigned char x;
    for(x=0;x<128; x++)
    {
        sub2 (x+1);
    }
}

And with avr-gcc 4.7 r176517 I get the following result (-Os -mmcu=atmega8).
In no case there is a 16-bit loop variable used.

foo:
    ldi r24,lo8(0)
.L5:
    sts bar,r24
    subi r24,lo8(-(1))
    cpi r24,lo8(-128)
    brne .L5
    ret

foo2:
    push r28
    ldi r28,lo8(0)
.L8:
    mov r24,r28
    rcall sub2
    subi r28,lo8(-(1))
    cpi r28,lo8(-128)
    brne .L8
    pop r28
    ret

foo21:
    push r28
    ldi r28,lo8(0)
.L11:
    subi r28,lo8(-(1))
    mov r24,r28
    rcall sub2
    cpi r28,lo8(-128)
    brne .L11
    pop r28
    ret

    .ident    "GCC: (GNU) 4.7.0 20110720 (experimental)"