[Bug treelang/33593] New: tree-outof-ssa moves sources of non-call exceptions past sequence points

[Bug treelang/33593] New: tree-outof-ssa moves sources of non-call exceptions past sequence points

[rsandifo at gcc dot gnu dot org]

tree-outof-ssa can move potentially-trapping operations across what were
sequence points, even when compiled with -fnon-call-exceptions.  E.g.,
consider the following C++ code, compiled with -fnon-call-exceptions:

------------------------------------------------------------------------
#include <stdio.h>

void foo (int) { printf ("Bar\n"); }

int
main (void)
{
  int a = 1 / 0;
  printf ("Foo\n");
  foo (a);
}
------------------------------------------------------------------------

The tree optimisers themselves preserve the intent of the code,
but tree-outof-ssa.c propogates the division into the call to foo():

------------------------------------------------------------------------
int main() ()
{
<bb 2>:
  __builtin_puts (&"Foo"[0]);
  foo (1 / 0);
  return 0;

}
------------------------------------------------------------------------

So the unoptimised program behaves as expected, raising the divide-by-zero
trap before printing "Foo".  The optimised version prints "Foo" first.


-- 
           Summary: tree-outof-ssa moves sources of non-call exceptions past
                    sequence points
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: treelang
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rsandifo at gcc dot gnu dot org
 GCC build triplet: x86_64-linux-gnu
  GCC host triplet: x86_64-linux-gnu
GCC target triplet: x86_64-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33593

[Bug tree-optimization/33593] tree-outof-ssa moves sources of non-call exceptions past sequence points

[rsandifo at gcc dot gnu dot org]

------- Comment #1 from rsandifo at gcc dot gnu dot org  2007-09-29 19:05 -------
Assigning to Diego as he already has a patch (thanks!)


-- 

rsandifo at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |dnovillo at google dot com
                   |dot org                     |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33593

[Bug tree-optimization/33593] tree-outof-ssa moves sources of non-call exceptions past sequence points

[pinskia at gcc dot gnu dot org]

------- Comment #2 from pinskia at gcc dot gnu dot org  2007-09-29 19:05 -------
1 / 0;

that does not aways trap.  on ppc an undefined value is returned.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33593

[Bug tree-optimization/33593] tree-outof-ssa moves sources of non-call exceptions past sequence points

[pinskia at gcc dot gnu dot org]

------- Comment #4 from pinskia at gcc dot gnu dot org  2007-09-29 19:08 -------
I think 1/0 should not be marked as throwing though as it is target dependent
if it actually will trap or not.  In fact as I mentioned on PPC, it does not
trap.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33593

[Bug tree-optimization/33593] tree-outof-ssa moves sources of non-call exceptions past sequence points

[dnovillo at google dot com]

------- Comment #3 from dnovillo at google dot com  2007-09-29 19:08 -------
Subject: Re:  tree-outof-ssa moves sources of non-call exceptions past sequence
points

On 29 Sep 2007 19:05:20 -0000, pinskia at gcc dot gnu dot org
<gcc-bugzilla@gcc.gnu.org> wrote:

> 1 / 0;
>
> that does not aways trap.  on ppc an undefined value is returned.

In which case tree_could_trap_p() will/should return false on this
expression then.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33593

[Bug tree-optimization/33593] tree-outof-ssa moves sources of non-call exceptions past sequence points

[dnovillo at gcc dot gnu dot org]

------- Comment #5 from dnovillo at gcc dot gnu dot org  2007-09-30 16:00 -------
Subject: Bug 33593

Author: dnovillo
Date: Sun Sep 30 16:00:36 2007
New Revision: 128893

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=128893
Log:

        PR 33593
        * tree-ssa-ter.c (is_replaceable_p): Return false if STMT may
        throw an exception.


testsuite/ChangeLog

        PR 33593
        * g++.dg/tree-ssa/pr33593.C: New test.


Added:
    trunk/gcc/testsuite/g++.dg/tree-ssa/pr33593.C
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/tree-ssa-ter.c


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33593

[Bug tree-optimization/33593] tree-outof-ssa moves sources of non-call exceptions past sequence points

[steven at gcc dot gnu dot org]

------- Comment #6 from steven at gcc dot gnu dot org  2008-02-03 14:35 -------
Should be fixed on the trunk.


-- 

steven at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.3.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33593