Re: optimization/8896: '-mcpu=xscale -fno-strict-aliasing -O2' generates wrong code

Re: optimization/8896: '-mcpu=xscale -fno-strict-aliasing -O2' generates wrong code

[Daniel Jacobowitz]

The following reply was made to PR optimization/8896; it has been noted by GNATS.

From: Daniel Jacobowitz <drow@mvista.com>
To: Richard Earnshaw <rearnsha@arm.com>
Cc: gcc-gnats@gcc.gnu.org, enrico.scholz@informatik.tu-chemnitz.de,
	gcc-bugs@gcc.gnu.org
Subject: Re: optimization/8896: '-mcpu=xscale -fno-strict-aliasing -O2' generates wrong code
Date: Thu, 15 May 2003 14:36:28 -0400

 On Thu, Dec 12, 2002 at 03:14:52PM +0000, Richard Earnshaw wrote:
 > http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=8896
 > 
 > I've attached what I believe to be the fix to the above PR.  It would be 
 > helpful if you could give it a whirl.
 
 I've added an updated testcase (produced after much labor by Russell
 King) which shows the problem in 3.2.3.  The testcase is extremely
 delicate.  It doesn't show the problem in 3.3 or HEAD, but I wouldn't
 be at all surprised if the problem was still there.  Making a
 testcase to show it is beyond me though.
 
 For the curious, here's a diff of the first differing dump with and
 without Richard's patch, using the 3.2 CVS branch.  It fails using
 only "-march=armv4 -O2".
 
 --- 32.s.22.postreload	2003-05-15 14:29:58.000000000 -0400
 +++ 32p.s.22.postreload	2003-05-15 14:29:59.000000000 -0400
 @@ -155,18 +155,25 @@
  (note 79 843 95 NOTE_INSN_DELETED)
  
  (insn 95 79 107 (set (reg/v:SI 11 fp [47])
 -        (const_int 2 [0x2])) 175 {*arm_movsi_insn} (insn_list:REG_DEP_ANTI 79 (nil))
 -    (nil))
 +        (const_int 1 [0x1])) 175 {*arm_movsi_insn} (insn_list:REG_DEP_ANTI 79 (nil))
 +    (expr_list:REG_EQUAL (const_int 1 [0x1])
 +        (nil)))
 +
 +(note 107 95 117 NOTE_INSN_DELETED)
  
 -(note 107 95 129 NOTE_INSN_DELETED)
 +(insn 117 107 129 (set (reg/v:SI 11 fp [47])
 +        (plus:SI (reg/v:SI 11 fp [47])
 +            (reg/f:SI 11 fp))) 4 {*arm_addsi3} (insn_list:REG_DEP_ANTI 107 (insn_list 95 (nil)))
 +    (expr_list:REG_EQUAL (const_int 2 [0x2])
 +        (nil)))
  
 -(note 129 107 135 NOTE_INSN_DELETED)
 +(note 129 117 135 NOTE_INSN_DELETED)
  
  (note 135 129 137 NOTE_INSN_DELETED)
  
  (insn 137 135 141 (set (reg/v:SI 11 fp [47])
          (plus:SI (reg/v:SI 11 fp [47])
 -            (reg/f:SI 11 fp))) 4 {*arm_addsi3} (insn_list:REG_DEP_ANTI 129 (insn_list 117 (nil)))
 +            (const_int 1 [0x1]))) 4 {*arm_addsi3} (insn_list:REG_DEP_ANTI 129 (insn_list 117 (nil)))
      (expr_list:REG_EQUAL (const_int 3 [0x3])
          (nil)))
  
 @@ -177,7 +184,7 @@
  
  (insn 197 141 221 (set (reg/v:SI 11 fp [47])
          (plus:SI (reg/v:SI 11 fp [47])
 -            (const_int 2 [0x2]))) 4 {*arm_addsi3} (insn_list:REG_DEP_ANTI 141 (insn_list:REG_DEP_OUTPUT 137 (insn_list 135 (nil))))
 +            (const_int 3 [0x3]))) 4 {*arm_addsi3} (insn_list:REG_DEP_ANTI 141 (insn_list:REG_DEP_OUTPUT 137 (insn_list 135 (nil))))
      (expr_list:REG_EQUAL (const_int 6 [0x6])
          (nil)))
  
 
 
 -- 
 Daniel Jacobowitz
 MontaVista Software                         Debian GNU/Linux Developer

Re: optimization/8896: '-mcpu=xscale -fno-strict-aliasing -O2' generates wrong code

[Dara Hazeghi]

The following reply was made to PR optimization/8896; it has been noted by GNATS.

From: Dara Hazeghi <dhazeghi@yahoo.com>
To: gcc-gnats@gcc.gnu.org, rearnsha@gcc.gnu.org
Cc: enrico.scholz@informatik.tu-chemnitz.de
Subject: Re: optimization/8896: '-mcpu=xscale -fno-strict-aliasing -O2' generates wrong code
Date: Wed, 14 May 2003 10:44:01 -0700

 http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit- 
 trail&database=gcc&pr=8896
 
 Hello,
 
 this PR has a patch that seems not to have been applied yet. Is this  
 the case? Richard, would it be possible try to get this patch reviewed  
 and checked in soon? Thanks,
 
 Dara
 

Re: optimization/8896: '-mcpu=xscale -fno-strict-aliasing -O2' generates wrong code

[steven]

Synopsis: '-mcpu=xscale -fno-strict-aliasing -O2' generates wrong code

State-Changed-From-To: closed->analyzed
State-Changed-By: steven
State-Changed-When: Sat Mar 22 13:54:13 2003
State-Changed-Why:
    The patch was never commited.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=8896

Re: optimization/8896: '-mcpu=xscale -fno-strict-aliasing -O2' generates wrong code

[Richard Earnshaw]

The following reply was made to PR optimization/8896; it has been noted by GNATS.

From: Richard Earnshaw <rearnsha@arm.com>
To: steven@gcc.gnu.org, enrico.scholz@informatik.tu-chemnitz.de,
        gcc-bugs@gcc.gnu.org, gcc-prs@gcc.gnu.org, rearnsha@gcc.gnu.org,
        gcc-gnats@gcc.gnu.org
Cc: Richard.Earnshaw@arm.com
Subject: Re: optimization/8896: '-mcpu=xscale -fno-strict-aliasing -O2' 
 generates wrong code
Date: Sat, 22 Mar 2003 13:28:25 +0000

 > Synopsis: '-mcpu=xscale -fno-strict-aliasing -O2' generates wrong code
 > 
 > State-Changed-From-To: analyzed->closed
 > State-Changed-By: steven
 > State-Changed-When: Sat Mar 22 10:05:37 2003
 > State-Changed-Why:
 >     Fixed according to reporter.  Richard Earnshaw posted a patch for this months ago -- apparently without mentioning the PR in the ChangeLog.
 > 
 > http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=8896
 
 That's 'cos I never got around to committing the patch...
 
 R.
 

Re: optimization/8896: '-mcpu=xscale -fno-strict-aliasing -O2' generates wrong code

[Steven Bosscher]

The following reply was made to PR optimization/8896; it has been noted by GNATS.

From: Steven Bosscher <s.bosscher@student.tudelft.nl>
To: Richard.Earnshaw@arm.com
Cc: steven@gcc.gnu.org, enrico.scholz@informatik.tu-chemnitz.de,
	gcc-bugs@gcc.gnu.org, gcc-prs@gcc.gnu.org, rearnsha@gcc.gnu.org,
	gcc-gnats@gcc.gnu.org
Subject: Re: optimization/8896: '-mcpu=xscale -fno-strict-aliasing -O2'
	generates wrong code
Date: 22 Mar 2003 14:33:14 +0100

 Op za 22-03-2003, om 14:28 schreef Richard Earnshaw:
 > > Synopsis: '-mcpu=xscale -fno-strict-aliasing -O2' generates wrong code
 > > 
 > > State-Changed-From-To: analyzed->closed
 > > State-Changed-By: steven
 > > State-Changed-When: Sat Mar 22 10:05:37 2003
 > > State-Changed-Why:
 > >     Fixed according to reporter.  Richard Earnshaw posted a patch for this months ago -- apparently without mentioning the PR in the ChangeLog.
 > > 
 > > http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=8896
 > 
 > That's 'cos I never got around to committing the patch...
 > 
 > R.
 
 Ah, that explains why I couldn't find the PR in the ChangeLog.
 Should I re-open the PR?
 
 Greetz
 Steven
 
 

Re: optimization/8896: '-mcpu=xscale -fno-strict-aliasing -O2' generates wrong code

[steven]

Synopsis: '-mcpu=xscale -fno-strict-aliasing -O2' generates wrong code

State-Changed-From-To: analyzed->closed
State-Changed-By: steven
State-Changed-When: Sat Mar 22 10:05:37 2003
State-Changed-Why:
    Fixed according to reporter.  Richard Earnshaw posted a patch for this months ago -- apparently without mentioning the PR in the ChangeLog.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=8896

Re: optimization/8896: '-mcpu=xscale -fno-strict-aliasing -O2' generates wrong code

[Enrico Scholz]

The following reply was made to PR optimization/8896; it has been noted by GNATS.

From: Enrico Scholz <enrico.scholz@sigma-chemnitz.de>
To: gcc-gnats@gcc.gnu.org, gcc-prs@gcc.gnu.org,
   enrico.scholz@informatik.tu-chemnitz.de, gcc-bugs@gcc.gnu.org,
   rearnsha@gcc.gnu.org
Cc:  
Subject: Re: optimization/8896: '-mcpu=xscale -fno-strict-aliasing -O2' generates wrong code
Date: 16 Dec 2002 18:59:14 +0100

 http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=8896
 
 The patch fixes the testcase, the kernel is running fine with it
 and I have not seen other/new errors since using it.
 
 
 Thanks for the fast fix
 Enrico

Re: optimization/8896: '-mcpu=xscale -fno-strict-aliasing -O2' generates wrong code

[Richard Earnshaw]

The following reply was made to PR optimization/8896; it has been noted by GNATS.

From: Richard Earnshaw <rearnsha@arm.com>
To: gcc-gnats@gcc.gnu.org, gcc-prs@gcc.gnu.org,
        enrico.scholz@informatik.tu-chemnitz.de, gcc-bugs@gcc.gnu.org
Cc:  
Subject: Re: optimization/8896: '-mcpu=xscale -fno-strict-aliasing -O2' generates
 wrong code
Date: Thu, 12 Dec 2002 15:14:52 +0000

 http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=8896
 
 I've attached what I believe to be the fix to the above PR.  It would be 
 helpful if you could give it a whirl.
 
 R.
 

Re: optimization/8896: '-mcpu=xscale -fno-strict-aliasing -O2' generates wrong code

[rearnsha]

Synopsis: '-mcpu=xscale -fno-strict-aliasing -O2' generates wrong code

Responsible-Changed-From-To: unassigned->rearnsha
Responsible-Changed-By: rearnsha
Responsible-Changed-When: Thu Dec 12 07:03:41 2002
Responsible-Changed-Why:
    .

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=8896

Re: optimization/8896: '-mcpu=xscale -fno-strict-aliasing -O2' generates wrong code

[rearnsha]

Synopsis: '-mcpu=xscale -fno-strict-aliasing -O2' generates wrong code

State-Changed-From-To: open->analyzed
State-Changed-By: rearnsha
State-Changed-When: Wed Dec 11 09:57:33 2002
State-Changed-Why:
    Confirmed.  The same bug does not occur with the latest compiler, but I think that's because an earlier pass of the compiler has optimized the problem away before it trips the bug.  
    
    Initial investigation suggests this is a problem with reload_combine().

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=8896

optimization/8896: '-mcpu=xscale -fno-strict-aliasing -O2' generates wrong code

[enrico.scholz]

>Number:         8896
>Category:       optimization
>Synopsis:       '-mcpu=xscale -fno-strict-aliasing -O2' generates wrong code
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          wrong-code
>Submitter-Id:   net
>Arrival-Date:   Tue Dec 10 15:46:01 PST 2002
>Closed-Date:
>Last-Modified:
>Originator:     Enrico Scholz
>Release:        gcc-3.2.1
>Organization:
>Environment:
Reading specs from /usr/lib/gcc-lib/arm-linux/3.2.1/specs
Configured with: ../configure --host=i386-redhat-linux --target=arm-linux --prefix=/usr --mandir=/usr/share/man --disable-checking --with-cpu=strongarm1100 --enable-languages=c
Thread model: posix
gcc version 3.2.1
>Description:
The arm-linux-gcc miscompiles XScale linux-kernels (the attached testcase is derived from fs/binfmt_elf.c of linux-2.5.49 + various ARM patches).

Because of other environment-problems, I do not have a complete test-program, but the miscompilation is visible in the disassembled .o-file. The interesting code is:

 ---- objdump -d binfmt_elf.o
  70:   e3a04002        mov     r4, #2  ; 0x2
  7c:   e0844004        add     r4, r4, r4
  84:   e1a0e004        mov     lr, r4
  e0:   e50be0b0        str     lr, [fp, -#176]


These statements are the result of:

|  60          elf_info[ei_index++] =  3; ...

which is wrong. Other ELF-tags are incorrect too, but this is the most obvious one.
>How-To-Repeat:
Compile the testprogram with

| arm-linux-gcc -O2 -fno-strict-aliasing -mcpu=xscale -c binfmt_elf.c

Watch the output with 'objdump -d binfmt_elf.o'
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted:
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