Re: optimization/3480: gcc-3.0, bad code generated with -O3 -fomit-frame-pointer on intel x86

[Juergen Keil <jk@tools.de>]

The following reply was made to PR optimization/3480; it has been noted by GNATS.

From: Juergen Keil <jk@tools.de>
To: chr.breitkopf@magrathea.de, rodrigc@gcc.gnu.org, gcc-bugs@gcc.gnu.org,
        gcc-gnats@gcc.gnu.org, gcc-prs@gcc.gnu.org, jk@tools.de,
        nobody@gcc.gnu.org
Cc:  
Subject: Re: optimization/3480: gcc-3.0, bad code generated with -O3 -fomit-frame-pointer on intel x86
Date: Mon, 3 Dec 2001 13:30:00 +0100 (MET)

 > Synopsis: gcc-3.0, bad code generated with -O3 -fomit-frame-pointer on in=
 tel=20
 x86
 >=20
 > State-Changed-From-To: open->feedback
 > State-Changed-By: rodrigc
 > State-Changed-When: Sat Dec  1 22:49:12 2001
 > State-Changed-Why:
 >     I think this has been fixed by:
 >     http://gcc.gnu.org/ml/gcc-patches/2001-11/msg00698.html
 >    =20
 >     Can you try a gcc 3.0.3 snapshot and verify this?
 >=20
 >=20
 http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=3Dview%20audit-trail&pr=3D3480&d=
 atabase=3Dg
 cc
 
 
 Yes, the problem seems to be fixed.
 
 
 I've downloaded and installed snapshot gcc-20011126 and the code
 generated for the problematic function 'acmStreamOpen' looks much better
 now:
 
         .type   acmStreamOpen,@function
 acmStreamOpen:
         pushl   %ebp
         pushl   %edi
         pushl   %esi
         pushl   %ebx
         subl    $16, %esp
         movl    44(%esp), %esi  <-- third parameter is now accessed via %es=
 p=20
 with correct offset
         movzwl  16(%esi), %ecx
         movl    48(%esp), %ebx
 
 
 
 In the released versions of gcc-3.0.x, the following buggy code is generate=
 d
 (from my bug report)
 
 =09.globl acmStreamOpen
 =09.type acmStreamOpen,@function
 =09acmStreamOpen:
 =09pushl %ebp
 =09pushl %edi
 =09pushl %esi
 =09pushl %ebx
 =09subl $96, %esp
 =09movl 12(%ebp), %esi <--- accesses pwfxSrc as offset(%ebp), no
 =09=09=09    <--- valid %ebp setup yet!
 =09movzwl 16(%esi), %edx
 =09movl 16(%ebp), %ebx
 
 
 --
 J=FCrgen Keil          =09=09jk@tools.de
 Tools GmbH=09=09=09+49 (228) 9858011