[Bug tree-optimization/19341] New: [4.0 Regression] DCE eliminating non-dead code

[Bug tree-optimization/19341] New: [4.0 Regression] DCE eliminating non-dead code

[belyshev at depni dot sinp dot msu dot ru]

void abort (void);

void __attribute__((regparm(1))) g (int *p)
{
  if (*p != 1)
    abort ();
}

int main ()
{
  int k;
  
  k = 1;
  asm volatile ("call g" :: "a" (&k));
  return 0;
}

-- 
           Summary: [4.0 Regression] DCE eliminating non-dead code
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P1
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: belyshev at depni dot sinp dot msu dot ru
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19341

[Bug tree-optimization/19341] [4.0 Regression] DCE eliminating non-dead code

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-01-09 01:37 -------
This code is invalid, for one you should not do a call in inline-asm.
Second the store to k is dead as the inline-asm is not told that k is accessed.

asm volatile ("call g" :: "a" (&k), "m" (k)); will fix the DCE issue but the code is still invalid because 
control flow 

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19341

[Bug tree-optimization/19341] [4.0 Regression] DCE eliminating non-dead code

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-01-09 01:54 -------
Another way to fix this is to add that this inline-asm clobers memory, aka:
  asm volatile ("call g" :: "a" (&k):"memory");


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19341

[Bug tree-optimization/19341] [4.0 Regression] DCE eliminating non-dead code

[rth at gcc dot gnu dot org]

------- Additional Comments From rth at gcc dot gnu dot org  2005-01-12 05:41 -------
.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |UNCONFIRMED
         Resolution|INVALID                     |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19341

[Bug tree-optimization/19341] [4.0 Regression] DCE eliminating non-dead code

[rth at gcc dot gnu dot org]

------- Additional Comments From rth at gcc dot gnu dot org  2005-01-12 05:41 -------
Not invalid.  The asm is a pointer escape point.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|0000-00-00 00:00:00         |2005-01-12 05:41:12
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19341

[Bug tree-optimization/19341] [4.0 Regression] DCE eliminating non-dead code

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
   Last reconfirmed|2005-01-12 05:41:12         |2005-01-12 06:08:11
               date|                            |
   Target Milestone|---                         |4.0.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19341

[Bug tree-optimization/19341] [4.0 Regression] DCE eliminating non-dead code

[steven at gcc dot gnu dot org]

------- Additional Comments From steven at gcc dot gnu dot org  2005-01-12 10:37 -------
Is an asm a pointer escape point even if it does not have a memory clobber 
constraint? 
 
 
 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19341

[Bug tree-optimization/19341] [4.0 Regression] DCE eliminating non-dead code

[rth at gcc dot gnu dot org]

------- Additional Comments From rth at gcc dot gnu dot org  2005-02-02 07:15 -------
Good point.  You've got to indicate that you touch memory in some way in order
to force the compiler to make memory consistent before the asm.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19341

[Bug tree-optimization/19341] [4.0 Regression] DCE eliminating non-dead code

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-09-30 14:04 -------
*** Bug 24146 has been marked as a duplicate of this bug. ***

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19341