[Bug tree-optimization/28410] New: [4.2 Regression] Wrong aliasing with global var grouping during call clobbering

[Bug tree-optimization/28410] New: [4.2 Regression] Wrong aliasing with global var grouping during call clobbering

[rguenth at gcc dot gnu dot org]

struct Bar { int p; };
struct Foo { struct Bar *p; };
int foo(struct Foo *f)
{
  f->p->p = 1;
  bar(f);
  return f->p->p;
}

.alias1:

  #   VUSE <SMT.4_6>;
  D.1528_2 = f_1->p; 
  #   SMT.5_8 = V_MAY_DEF <SMT.5_7>;
  D.1528_2->p = 1;
  #   .GLOBAL_VAR_10 = V_MAY_DEF <.GLOBAL_VAR_9>;
  bar (f_1);
  #   VUSE <SMT.4_6>;
  D.1528_3 = f_1->p;
  #   VUSE <SMT.5_8>;
  D.1529_4 = D.1528_3->p;
  return D.1529_4;

and fre then does:

  #   VUSE <SMT.4_6>;
  D.1528_2 = f_1->p;
  #   SMT.5_8 = V_MAY_DEF <SMT.5_7>;
  D.1528_2->p = 1;
  #   .GLOBAL_VAR_10 = V_MAY_DEF <.GLOBAL_VAR_9>;
  bar (f_1);
  D.1528_3 = D.1528_2;
  #   VUSE <SMT.5_8>;
  D.1529_4 = D.1528_3->p;
  return D.1529_4;


miscompiles kde4.


-- 
           Summary: [4.2 Regression] Wrong aliasing with global var grouping
                    during call clobbering
           Product: gcc
           Version: 4.2.0
            Status: UNCONFIRMED
          Keywords: wrong-code, alias
          Severity: blocker
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rguenth at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28410

[Bug tree-optimization/28410] [4.2 Regression] Wrong aliasing with global var grouping during call clobbering

[rguenth at gcc dot gnu dot org]

------- Comment #1 from rguenth at gcc dot gnu dot org  2006-07-17 12:51 -------
Oh - build with -O2 --param global-var-threshold=1


-- 

rguenth at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28410

[Bug tree-optimization/28410] [4.2 Regression] Wrong aliasing with global var grouping during call clobbering

[pinskia at gcc dot gnu dot org]

-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pinskia at gcc dot gnu dot
                   |                            |org
   Target Milestone|---                         |4.3.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28410

[Bug tree-optimization/28410] [4.2 Regression] Wrong aliasing with global var grouping during call clobbering

[pinskia at gcc dot gnu dot org]

-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.3.0                       |4.2.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28410

[Bug tree-optimization/28410] [4.2 Regression] Wrong aliasing with global var grouping during call clobbering

[rguenth at gcc dot gnu dot org]

------- Comment #2 from rguenth at gcc dot gnu dot org  2006-07-17 13:29 -------
Runnable testcase:

extern void abort(void);
struct Bar { int p; };
struct Foo { struct Bar *p; };
struct Bar p0 = { 0 };
struct Bar p1 = { 1 };
void bar(struct Foo *f)
{
  f->p = &p0;
}
int foo(struct Foo *f)
{
  f->p->p = 1;
  bar(f);
  return f->p->p;
}
int main()
{
  struct Foo f;
  f.p = &p1;
  if (foo(&f) != 0)
    abort ();
  return 0;
}


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28410

[Bug tree-optimization/28410] [4.2 Regression] Wrong aliasing with global var grouping during call clobbering

[dnovillo at gcc dot gnu dot org]

-- 

dnovillo at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |dnovillo at gcc dot gnu dot
                   |dot org                     |org
             Status|UNCONFIRMED                 |ASSIGNED
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2006-07-17 13:30:56
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28410

[Bug tree-optimization/28410] [4.2 Regression] Wrong aliasing with global var grouping during call clobbering

[dnovillo at gcc dot gnu dot org]

------- Comment #3 from dnovillo at gcc dot gnu dot org  2006-07-18 13:25 -------

Testing patch.  The bug was in the alias pruning code.  We need to handle
.GLOBAL_VAR in access_can_touch_variable.  A memory reference that uses a
call-clobbered memory tag should always be considered to touch .GLOBAL_VAR.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28410

[Bug tree-optimization/28410] [4.2 Regression] Wrong aliasing with global var grouping during call clobbering

[dberlin at dberlin dot org]

------- Comment #4 from dberlin at gcc dot gnu dot org  2006-07-18 14:06 -------
Subject: Re:  [4.2 Regression] Wrong aliasing
 with global var grouping during call clobbering

dnovillo at gcc dot gnu dot org wrote:
> ------- Comment #3 from dnovillo at gcc dot gnu dot org  2006-07-18 13:25 -------
> 
> Testing patch.  The bug was in the alias pruning code.  We need to handle
> .GLOBAL_VAR in access_can_touch_variable.  A memory reference that uses a
> call-clobbered memory tag should always be considered to touch .GLOBAL_VAR.

Yay for random invariants!


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28410

[Bug tree-optimization/28410] [4.2 Regression] Wrong aliasing with global var grouping during call clobbering

[dnovillo at gcc dot gnu dot org]

------- Comment #5 from dnovillo at gcc dot gnu dot org  2006-07-18 17:28 -------
Subject: Bug 28410

Author: dnovillo
Date: Tue Jul 18 17:27:57 2006
New Revision: 115564

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=115564
Log:

        PR 28410
        * tree-ssa-operands.c (access_can_touch_variable): Update
        comment.
        Return true if ALIAS is .GLOBAL_VAR.

testsuite/ChangeLog

        PR 28410
        * gcc.dg/tree-ssa/pr28410.c: New test.

Added:
    trunk/gcc/testsuite/gcc.dg/tree-ssa/pr28410.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-ssa-operands.c


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28410

[Bug tree-optimization/28410] [4.2 Regression] Wrong aliasing with global var grouping during call clobbering

[dnovillo at gcc dot gnu dot org]

------- Comment #6 from dnovillo at gcc dot gnu dot org  2006-07-18 17:29 -------

Fixed.  http://gcc.gnu.org/ml/gcc-patches/2006-07/msg00786.html


-- 

dnovillo at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28410