[Bug middle-end/24434] New: [4.0/4.1 Regression] get_varargs_alias_set returns 0 always

[Bug middle-end/24434] New: [4.0/4.1 Regression] get_varargs_alias_set returns 0 always

[pinskia at gcc dot gnu dot org]

With the following change:
2004-06-08  Jason Merrill  <jason@redhat.com>

        Gimplify VA_ARG_EXPR into simpler forms.

get_varargs_alias_set will always return 0, which causes us to miss some
loads/store elimination and such at the rtl level (and tree level also).

The comment in alias.c is:
  /* We now lower VA_ARG_EXPR, and there's currently no way to attach the
     varargs alias set to an INDIRECT_REF (FIXME!), so we can't
     consistently use the varargs alias set for loads from the varargs
     area.  So don't use it anywhere.  */


-- 
           Summary: [4.0/4.1 Regression] get_varargs_alias_set returns 0
                    always
           Product: gcc
           Version: 4.1.0
            Status: UNCONFIRMED
          Keywords: missed-optimization, alias
          Severity: minor
          Priority: P2
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: pinskia at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24434

[Bug middle-end/24434] [4.0/4.1 Regression] get_varargs_alias_set returns 0 always

[pinskia at gcc dot gnu dot org]

------- Comment #1 from pinskia at gcc dot gnu dot org  2005-10-18 19:56 -------
Setting target milestone to 4.2 so we don't forget about this since it is a
regression.


-- 

pinskia at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24434

[Bug middle-end/24434] [4.0/4.1 Regression] get_varargs_alias_set returns 0 always

[pinskia at gcc dot gnu dot org]

-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P2                          |P5
   Target Milestone|4.2.0                       |4.1.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24434

[Bug middle-end/24434] [4.0/4.1 Regression] get_varargs_alias_set returns 0 always

[pinskia at gcc dot gnu dot org]

------- Comment #2 from pinskia at gcc dot gnu dot org  2005-11-11 17:55 -------
Confirmed.


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pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2005-11-11 17:55:39
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24434

[Bug middle-end/24434] [4.0/4.1/4.2 Regression] get_varargs_alias_set returns 0 always

[mmitchel at gcc dot gnu dot org]

-- 

mmitchel at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.1.0                       |4.1.1


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24434

[Bug middle-end/24434] [4.0/4.1/4.2 Regression] get_varargs_alias_set returns 0 always

[mmitchel at gcc dot gnu dot org]

------- Comment #3 from mmitchel at gcc dot gnu dot org  2006-05-25 02:36 -------
Will not be fixed in 4.1.1; adjust target milestone to 4.1.2.


-- 

mmitchel at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.1.1                       |4.1.2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24434

[Bug middle-end/24434] [4.0/4.1/4.2 Regression] get_varargs_alias_set returns 0 always

[steven at gcc dot gnu dot org]

------- Comment #4 from steven at gcc dot gnu dot org  2006-05-28 09:53 -------
This looks like one that the mem-ssa folks may want to give a look.

Will it be easier in mem-ssa to attach alias info to INDIRECT_REF nodes?


-- 

steven at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24434

[Bug middle-end/24434] [4.0/4.1/4.2/4.3 Regression] get_varargs_alias_set returns 0 always

[mmitchel at gcc dot gnu dot org]

-- 

mmitchel at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.1.2                       |4.1.3


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24434

[Bug middle-end/24434] [4.2/4.3/4.4 Regression] get_varargs_alias_set returns 0 always

[jsm28 at gcc dot gnu dot org]

------- Comment #5 from jsm28 at gcc dot gnu dot org  2008-07-04 20:06 -------
Closing 4.1 branch.


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jsm28 at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[4.1/4.2/4.3/4.4 Regression]|[4.2/4.3/4.4 Regression]
                   |get_varargs_alias_set       |get_varargs_alias_set
                   |returns 0 always            |returns 0 always
   Target Milestone|4.1.3                       |4.2.5


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24434

[Bug middle-end/24434] [4.3/4.4/4.5 Regression] get_varargs_alias_set returns 0 always

[jsm28 at gcc dot gnu dot org]

------- Comment #6 from jsm28 at gcc dot gnu dot org  2009-03-31 19:00 -------
Closing 4.2 branch.


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jsm28 at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[4.2/4.3/4.4/4.5 Regression]|[4.3/4.4/4.5 Regression]
                   |get_varargs_alias_set       |get_varargs_alias_set
                   |returns 0 always            |returns 0 always
   Target Milestone|4.2.5                       |4.3.4


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24434

[Bug middle-end/24434] [4.3/4.4/4.5 Regression] get_varargs_alias_set returns 0 always

[rguenth at gcc dot gnu dot org]

------- Comment #7 from rguenth at gcc dot gnu dot org  2009-08-04 12:27 -------
GCC 4.3.4 is being released, adjusting target milestone.


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rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.3.4                       |4.3.5


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24434

[Bug middle-end/24434] [4.3/4.4/4.5/4.6 Regression] get_varargs_alias_set returns 0 always

[rguenth at gcc dot gnu dot org]

------- Comment #8 from rguenth at gcc dot gnu dot org  2010-05-22 18:10 -------
GCC 4.3.5 is being released, adjusting target milestone.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.3.5                       |4.3.6


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24434

[Bug middle-end/24434] [4.3/4.4/4.5/4.6 Regression] get_varargs_alias_set returns 0 always

[steven at gcc dot gnu dot org]

------- Comment #9 from steven at gcc dot gnu dot org  2010-07-15 23:08 -------
If the quoted comment in this bug's comment #0 is true, then this bug should be
fixable with MEM_REF.


-- 

steven at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24434

[Bug middle-end/24434] [4.3/4.4/4.5/4.6 Regression] get_varargs_alias_set returns 0 always

[steven at gcc dot gnu dot org]

------- Comment #10 from steven at gcc dot gnu dot org  2010-07-15 23:09 -------
Pinski, got test case?


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steven at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |WAITING


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24434

[Bug middle-end/24434] [4.3/4.4/4.5/4.6 Regression] get_varargs_alias_set returns 0 always

[pinskia at gcc dot gnu dot org]

------- Comment #11 from pinskia at gcc dot gnu dot org  2010-07-15 23:13 -------
(In reply to comment #10)
> Pinski, got test case?

No I don't have one.  At this point I was filing bugs about the FIXME's inside
the compiler itself.  This comment is still there.  If this is now fixable with
MEM_REF, then we should be able to fix it and removed the FIXME.  If it is not
fixable at all, then we should remove the FIXME part of the comment.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |NEW
   Last reconfirmed|2010-03-02 19:24:00         |2010-07-15 23:13:16
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24434

[Bug middle-end/24434] [4.3/4.4/4.5/4.6 Regression] get_varargs_alias_set returns 0 always

[rguenth at gcc dot gnu dot org]

------- Comment #12 from rguenth at gcc dot gnu dot org  2010-07-16 08:22 -------
What does the standard say here?  What is the type in effect for aliasing
when doing

 int i = va_arg (va, int);

?  Is type-punning allowed when unpacking args?

Note that we would need to make sure to use the correct alias set when
setting up args at the callers site as well.

But yes, this now looks easily fixable (and also was with INDIRECT_REFs
via type casts).


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24434

[Bug middle-end/24434] [4.3/4.4/4.5/4.6 Regression] get_varargs_alias_set returns 0 always

[segher at gcc dot gnu dot org]

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------- Comment #13 from segher at gcc dot gnu dot org  2010-07-17 19:04 -------
(In reply to comment #12)
> What does the standard say here?  What is the type in effect for aliasing
> when doing
> 
>  int i = va_arg (va, int);
> 
> ?  Is type-punning allowed when unpacking args?

>From C99, 7.15.1.1/2:

[...] if type is not compatible with the type of the actual next argument (as
promoted according to the default argument promotions), the behavior is
undefined, except for the following cases:

— one type is a signed integer type, the other type is the corresponding
unsigned integer type, and the value is representable in both types;

— one type is pointer to void and the other is a pointer to a character type.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24434