[Bug c/17860] New: Wrong generated code for loop with inlined function inside.

[Bug c/17860] New: Wrong generated code for loop with inlined function inside.

[tal dot agmon at nsc dot com]

Compile the following code with: gcc -O3. The output should be 

   foo is: 0, i is: 1

Yet the output is:

   foo is: 0, i is: 0

This is the source code:

#include <stdio.h>
int foo=100;

int f ()
{
  foo = 0;
}

void main ()
{
  int i;

  for (i = 0; i < foo; i++)
    {
      f ();
    }
  printf("foo is: %d, i is: %d\n",foo,i);
}

-- 
           Summary: Wrong generated code for loop with inlined function
                    inside.
           Product: gcc
           Version: 3.4.2
            Status: UNCONFIRMED
          Severity: critical
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: tal dot agmon at nsc dot com
                CC: gcc-bugs at gcc dot gnu dot org,paul dot woegerer at nsc
                    dot com
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17860

[Bug rtl-optimization/17860] Wrong generated code for loop with inlined function inside.

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-10-06 12:55 -------
Since this is not a regression closing as fixed for 4.0.0.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|critical                    |normal
             Status|UNCONFIRMED                 |RESOLVED
          Component|c                           |rtl-optimization
           Keywords|                            |wrong-code
      Known to fail|                            |2.95.3 3.3.2 3.4.2 3.4.3
      Known to work|                            |4.0.0
         Resolution|                            |FIXED
   Target Milestone|---                         |4.0.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17860

[Bug rtl-optimization/17860] Wrong generated code for loop with inlined function inside.

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-10-06 13:06 -------
*** Bug 17861 has been marked as a duplicate of this bug. ***

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rguenth at tat dot physik
                   |                            |dot uni-tuebingen dot de


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17860

[Bug rtl-optimization/17860] Wrong generated code for loop with inlined function inside.

[rguenth at tat dot physik dot uni-tuebingen dot de]

------- Additional Comments From rguenth at tat dot physik dot uni-tuebingen dot de  2004-10-06 13:15 -------
Proper testcase:

extern void abort();
int foo=100;
inline int f ()
{
 foo = 0;
}
void main ()
{
 int i;
 for (i = 0; i < foo; i++)
     f ();
 if (i != 1)
   abort();
}

Also the rtl-optimization bug may be latent on mainline, how do we know?

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17860

[Bug rtl-optimization/17860] Wrong generated code for loop with varying bound

[bonzini at gcc dot gnu dot org]

------- Additional Comments From bonzini at gcc dot gnu dot org  2004-10-06 17:04 -------
It is not fixed.  You can mark it as WONTFIX, but it is not reasonable to mark
it as FIXED.

I tried looking at some dumps for this test case, which is even more severe:

  extern void abort ();

  int
  main ()
  {
    int i;
    int foo = 2;
    for (i = 0; i < foo; i++)
      foo = 0;

    if (i != 1)
      abort ();
  }

If the alias1 pass, which cannot be disabled, wouldn't rewrite "i < foo" to "foo
> i", chances are the test case would still trigger.  I'm preparing a patch to
provide -fno-tree-ssa again, hoping that this will make more 3.4 test cases fail
again with 4.0 (GIMPLE would change the input to the RTL optimzation passes a
lot, but hopefully CSE will make things saner again).

Reopening with a target milestone of 3.4.4.

Paolo

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |critical
             Status|RESOLVED                    |UNCONFIRMED
         Resolution|FIXED                       |
            Summary|Wrong generated code for    |Wrong generated code for
                   |loop with inlined function  |loop with varying bound
                   |inside.                     |
   Target Milestone|4.0.0                       |3.4.4


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17860

[Bug rtl-optimization/17860] Wrong generated code for loop with varying bound

[bonzini at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2004-10-06 17:05:07
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17860

[Bug rtl-optimization/17860] Wrong generated code for loop with varying bound

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-10-06 17:09 -------
Since this is not a regression we should not have the target milestone set, also the old loop invariant 
moving is being removed the last time I heard.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|critical                    |normal
   Target Milestone|3.4.4                       |---


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17860

[Bug rtl-optimization/17860] Wrong generated code for loop with varying bound

[reichelt at gcc dot gnu dot org]

------- Additional Comments From reichelt at gcc dot gnu dot org  2004-10-06 17:18 -------
The bug can be triggered by "-O -fstrength-reduce".


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |reichelt at gcc dot gnu dot
                   |                            |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17860

[Bug rtl-optimization/17860] Wrong generated code for loop with varying bound

[reichelt at gcc dot gnu dot org]

------- Additional Comments From reichelt at gcc dot gnu dot org  2004-10-06 17:26 -------
And it disappears with "-O2 -fno-strength-reduce".


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17860

[Bug rtl-optimization/17860] Wrong generated code for loop with varying bound

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-10-06 17:37 -------
This is most likely related to PR 16052.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
  BugsThisDependsOn|                            |16052


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17860

[Bug rtl-optimization/17860] Wrong generated code for loop with varying bound

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-10-06 17:40 -------
But more related to PR 13299.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17860

[Bug rtl-optimization/17860] Wrong generated code for loop with varying bound

[bonzini at gcc dot gnu dot org]

------- Additional Comments From bonzini at gcc dot gnu dot org  2004-10-07 10:05 -------
Discussion and patch

http://gcc.gnu.org/ml/gcc-patches/2004-10/msg00622.html

A transformation check_dbra_loop that is causing the miscompilation because it 
uses a != test; not related to 16052 which is about signedness.

Also not related to loop invariant motion.  The source is a bogus 
NOTE_INSN_LOOP_VTOP note: after CSE and GCSE's constant propagation, the loop 
is not anymore a duplicate of the loop-entry test:

   if (i < 2)
     do
       foo = 0, i++;
     while (i < 0);

is not reducible to a while loop, while loop thinks it is because the VTOP note 
remains.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bonzini at gcc dot gnu dot
                   |                            |org
  BugsThisDependsOn|16052                       |
             Status|NEW                         |ASSIGNED
           Keywords|                            |patch
   Last reconfirmed|2004-10-06 17:05:07         |2004-10-07 10:05:58
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17860

[Bug rtl-optimization/17860] Wrong generated code for loop with varying bound

[rguenth at tat dot physik dot uni-tuebingen dot de]

------- Additional Comments From rguenth at tat dot physik dot uni-tuebingen dot de  2004-10-07 10:18 -------
Subject: Re:  Wrong generated code for loop with
 varying bound

> Also not related to loop invariant motion.  The source is a bogus
> NOTE_INSN_LOOP_VTOP note: after CSE and GCSE's constant propagation, the loop
> is not anymore a duplicate of the loop-entry test:

Yes, 06.cse is the first wrong dump for with -O, 04.jump looks sane.



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17860

[Bug rtl-optimization/17860] [3.4 only] Wrong generated code for loop with varying bound

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-11-21 01:39 -------
The reason why I say this can never even happen on 4.0 is because the loop notes are not done until 
after the "new" rtl-loop pass is done.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|Wrong generated code for    |[3.4 only] Wrong generated
                   |loop with varying bound     |code for loop with varying
                   |                            |bound
   Target Milestone|---                         |3.4.4


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17860

[Bug rtl-optimization/17860] [3.4 only] Wrong generated code for loop with varying bound

[bonzini at gcc dot gnu dot org]

------- Additional Comments From bonzini at gcc dot gnu dot org  2005-02-10 12:51 -------
Oh, and VTOP notes were killed on mainline.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17860

[Bug rtl-optimization/17860] [3.4 only] Wrong generated code for loop with varying bound

[mmitchel at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|3.4.4                       |3.4.5


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17860

[Bug rtl-optimization/17860] [3.4 only] Wrong generated code for loop with varying bound

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From bonzini at gcc dot gnu dot org  2005-08-09 08:23 -------
Patch committed.
------- Additional Comments From cvs-commit at gcc dot gnu dot org  2005-08-09 08:23 -------
Subject: Bug 17860

CVSROOT:	/cvs/gcc
Module name:	gcc
Branch: 	gcc-3_4-branch
Changes by:	bonzini@gcc.gnu.org	2005-08-09 08:22:55

Modified files:
	gcc            : ChangeLog loop.c 

Log message:
	2005-08-09  Paolo Bonzini  <bonzini@gnu.org>
	
	PR rtl-optimization/17860
	* loop.c (check_dbra_loop): Do not try to use an end condition
	like "i != 0" in the reversed loop.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=2.2326.2.906&r2=2.2326.2.907
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/loop.c.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=1.488.2.8&r2=1.488.2.9



-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17860

[Bug rtl-optimization/17860] [3.4 only] Wrong generated code for loop with varying bound

[bonzini at gcc dot gnu dot org]

------- Additional Comments From bonzini at gcc dot gnu dot org  2005-08-09 08:23 -------
Patch committed.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17860