[Bug optimization/15387] New: Misscompilation in sibcall optimization

[Bug optimization/15387] New: Misscompilation in sibcall optimization

[rakdver at gcc dot gnu dot org]

The following testcase aborts when compiled with -O2:

struct foo { int a, b, c; };

void
brother (int a, int b)
{
  if (a)
    abort ();
}


void
sister (struct foo f, int b)
{
  int *tmp = &f.b;

  brother (*tmp == b, b);
}

int
main (void)
{
  struct foo f;

  f.a = 7;
  f.b = 8;
  f.c = 9;
  sister (f, 1);
  exit (0);
}

The problem is that a sibcall is created for a call of brother, but the
arguments are rewritten in place.  Therefore first the place on the stack
where f.b is stored is rewritten by b, and then it is compared to b.

Probably caused by some interaction between the new way how the tail calls are
handled (information passed from tree level) and calls.c.

-- 
           Summary: Misscompilation in sibcall optimization
           Product: gcc
           Version: tree-ssa
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P2
         Component: optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rakdver at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org,jh at suse dot cz
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15387

[Bug middle-end/15387] [tree-ssa] Misscompilation in sibcall optimization

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-05-11 21:46 -------
Confirmed, the issue is that it is putting the variable b in the slot too early so it is comparing against 
itself which gets optimized in later passes to 1.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
          Component|optimization                |middle-end
     Ever Confirmed|                            |1
           Keywords|                            |RTL
   Last reconfirmed|0000-00-00 00:00:00         |2004-05-11 21:46:15
               date|                            |
            Summary|Misscompilation in sibcall  |[tree-ssa] Misscompilation
                   |optimization                |in sibcall optimization
   Target Milestone|---                         |tree-ssa


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15387

[Bug rtl-optimization/15387] [3.5 Regression] Misscompilation in sibcall optimization

[rakdver at gcc dot gnu dot org]

------- Additional Comments From rakdver at gcc dot gnu dot org  2004-05-21 21:38 -------
Analysis and possible patch:

http://gcc.gnu.org/ml/gcc-patches/2004-05/msg01396.html

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15387

[Bug rtl-optimization/15387] [3.5 Regression] Misscompilation in sibcall optimization

[rakdver at gcc dot gnu dot org]

------- Additional Comments From rakdver at gcc dot gnu dot org  2004-07-11 02:53 -------
Fixed.

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15387