[Bug tree-optimization/33562] New: aggregate DSE disabled

[Bug tree-optimization/33562] New: aggregate DSE disabled

[rguenth at gcc dot gnu dot org]

Author: rguenth
Date: Wed Sep 26 11:55:17 2007
New Revision: 128810

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=128810
Log:
2007-09-26  Richard Guenther  <rguenther@suse.de>

        PR tree-optimization/30375
        PR tree-optimization/33560
...
        * gcc.dg/tree-ssa/complex-4.c: XFAIL.
        * gcc.dg/tree-ssa/complex-5.c: Likewise.
        * gcc.dg/tree-ssa/ssa-dse-9.c: Likewise.


-- 
           Summary: aggregate DSE disabled
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Keywords: missed-optimization, xfail
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rguenth at gcc dot gnu dot org
 BugsThisDependsOn: 30375


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33562

[Bug tree-optimization/33562] aggregate DSE disabled

[belyshev at depni dot sinp dot msu dot ru]

-- 

belyshev at depni dot sinp dot msu dot ru changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |belyshev at depni dot sinp
                   |                            |dot msu dot ru
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2007-09-26 12:03:25
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33562

[Bug tree-optimization/33562] [4.3 Regression] aggregate DSE disabled

[pinskia at gcc dot gnu dot org]

------- Comment #1 from pinskia at gcc dot gnu dot org  2007-09-26 19:04 -------
        * gcc.dg/tree-ssa/complex-4.c: XFAIL.
is a regression then because the testcase was added back in 2006-02-18 (by me).


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pinskia at gcc dot gnu dot
                   |                            |org
            Summary|aggregate DSE disabled      |[4.3 Regression] aggregate
                   |                            |DSE disabled
   Target Milestone|---                         |4.3.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33562

[Bug tree-optimization/33562] [4.3 Regression] aggregate DSE disabled

[rguenther at suse dot de]

------- Comment #2 from rguenther at suse dot de  2007-09-27 09:08 -------
Subject: Re:  [4.3 Regression] aggregate DSE
 disabled

On Wed, 26 Sep 2007, pinskia at gcc dot gnu dot org wrote:

> ------- Comment #1 from pinskia at gcc dot gnu dot org  2007-09-26 19:04 -------
>         * gcc.dg/tree-ssa/complex-4.c: XFAIL.
> is a regression then because the testcase was added back in 2006-02-18
> (by me).

I did wonder what optimized that before...  (maybe a separate bug for
this is more appropriate)

Richard.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33562

Re: [Bug tree-optimization/33562] [4.3 Regression] aggregate DSE disabled

[Andrew Pinski]

On 27 Sep 2007 09:08:17 -0000, rguenther at suse dot de
<gcc-bugzilla@gcc.gnu.org> wrote:
> I did wonder what optimized that before...  (maybe a separate bug for
> this is more appropriate)

Must_def cause the optimization to work IIRC.  In fact this is the
reason why aggregate DSE was added was specifically to fix this
testcase.

See http://gcc.gnu.org/ml/gcc-patches/2006-05/msg01115.html which
specifically mentions this.  I am still trying to understand why we
removed must_def anyways.  Everything points to the removal of
must_def caused many different regressions.

Thanks,
Andrew Pinski

[Bug tree-optimization/33562] [4.3 Regression] aggregate DSE disabled

[pinskia at gmail dot com]

------- Comment #3 from pinskia at gmail dot com  2007-09-27 09:19 -------
Subject: Re:  [4.3 Regression] aggregate DSE disabled

On 27 Sep 2007 09:08:17 -0000, rguenther at suse dot de
<gcc-bugzilla@gcc.gnu.org> wrote:
> I did wonder what optimized that before...  (maybe a separate bug for
> this is more appropriate)

Must_def cause the optimization to work IIRC.  In fact this is the
reason why aggregate DSE was added was specifically to fix this
testcase.

See http://gcc.gnu.org/ml/gcc-patches/2006-05/msg01115.html which
specifically mentions this.  I am still trying to understand why we
removed must_def anyways.  Everything points to the removal of
must_def caused many different regressions.

Thanks,
Andrew Pinski


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33562

[Bug tree-optimization/33562] [4.3 Regression] aggregate DSE disabled

[rguenth at gcc dot gnu dot org]

------- Comment #4 from rguenth at gcc dot gnu dot org  2007-09-27 10:17 -------
Created an attachment (id=14254)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=14254&action=view)
restore DCE of killing defs

some ssa updating is broken in dce though:

/space/rguenther/src/svn/pointer_plus/gcc/testsuite/gcc.dg/tree-ssa/complex-4.c:
In function 'f':
/space/rguenther/src/svn/pointer_plus/gcc/testsuite/gcc.dg/tree-ssa/complex-4.c:5:
error: type mismatch between an SSA_NAME and its symbol
/space/rguenther/src/svn/pointer_plus/gcc/testsuite/gcc.dg/tree-ssa/complex-4.c:5:
error: in statement
# SFT.1_12 = VDEF <SFT.1_11> { SFT.1 }
REALPART_EXPR <t> = 2;
/space/rguenther/src/svn/pointer_plus/gcc/testsuite/gcc.dg/tree-ssa/complex-4.c:5:
internal compiler error: verify_ssa failed
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://gcc.gnu.org/bugs.html> for instructions.

but dceloop now removes the dead store and we get:

f ()
{
  complex int t;
  int D.1551;

<bb 2>:
  # SFT.1_12 = VDEF <SFT.1_11>
  REALPART_EXPR <t> = 2;
  # SFT.0_13 = VDEF <SFT.0_10>
  IMAGPART_EXPR <t> = 2;
  # SFT.0_14 = VDEF <SFT.0_13>
  # SFT.1_15 = VDEF <SFT.1_12>
  D.1551_5 = g (&t);
  return D.1551_5;

}


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33562

[Bug tree-optimization/33562] [4.3 Regression] aggregate DSE disabled

[rguenth at gcc dot gnu dot org]

------- Comment #5 from rguenth at gcc dot gnu dot org  2007-09-27 13:38 -------
Created an attachment (id=14256)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=14256&action=view)
more complete patch to resture DCE of killing defs

It still breaks in some cases.  With the unfortunate fact that we need the
VMAYUSEs even for killing defs we might end up to need to do a two-phase DCE
for those :/  (See the special casing of PHI_NODEs in the patch, it seems some
more special casing is missing)


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #14254|0                           |1
        is obsolete|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33562

[Bug tree-optimization/33562] [4.3 Regression] aggregate DSE disabled

[rguenth at gcc dot gnu dot org]

------- Comment #6 from rguenth at gcc dot gnu dot org  2007-09-27 13:42 -------
Diego, it sucks that we need to jump through hoops to get V_MUST_DEF "back".


-- 

rguenth 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=33562

[Bug tree-optimization/33562] [4.3 Regression] aggregate DSE disabled

[dnovillo at google dot com]

------- Comment #7 from dnovillo at google dot com  2007-09-27 13:48 -------
Subject: Re:  [4.3 Regression] aggregate DSE disabled

On 27 Sep 2007 13:42:11 -0000, rguenth at gcc dot gnu dot org
<gcc-bugzilla@gcc.gnu.org> wrote:

> Diego, it sucks that we need to jump through hoops to get V_MUST_DEF "back".

Unless we can prove that it is impossible to implement DSE any other
way, I would prefer to keep virtual SSA as simple as possible.  It's
meant as a safety net and a "good enough" UD web for passes that do
not care for being too aggressive.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33562

[Bug tree-optimization/33562] [4.3 Regression] aggregate DSE disabled

[rguenther at suse dot de]

------- Comment #8 from rguenther at suse dot de  2007-09-27 14:01 -------
Subject: Re:  [4.3 Regression] aggregate DSE
 disabled

On Thu, 27 Sep 2007, dnovillo at google dot com wrote:

> ------- Comment #7 from dnovillo at google dot com  2007-09-27 13:48 -------
> Subject: Re:  [4.3 Regression] aggregate DSE disabled
> 
> On 27 Sep 2007 13:42:11 -0000, rguenth at gcc dot gnu dot org
> <gcc-bugzilla@gcc.gnu.org> wrote:
> 
> > Diego, it sucks that we need to jump through hoops to get V_MUST_DEF "back".
> 
> Unless we can prove that it is impossible to implement DSE any other
> way, I would prefer to keep virtual SSA as simple as possible.  It's
> meant as a safety net and a "good enough" UD web for passes that do
> not care for being too aggressive.

I sort-of agree.  Still DCE was able to handle tree-ssa/complex-4.c
before we removed V_MUST_DEF.  Which is what I'm trying to get back.

As "good enough" UD web it would be nice to have only single VDEFs on
stores (I don't care for clobbers at call sites).  Though finding the
optimal static partitioning to ensure this is probably hard?

Richard.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33562

[Bug tree-optimization/33562] [4.3 Regression] aggregate DSE disabled

[dnovillo at google dot com]

------- Comment #9 from dnovillo at google dot com  2007-09-27 14:12 -------
Subject: Re:  [4.3 Regression] aggregate DSE disabled

On 27 Sep 2007 14:01:18 -0000, rguenther at suse dot de
<gcc-bugzilla@gcc.gnu.org> wrote:

> I sort-of agree.  Still DCE was able to handle tree-ssa/complex-4.c
> before we removed V_MUST_DEF.  Which is what I'm trying to get back.

Yeah, it is somewhat tempting to make the infrastructure more powerful
because you suddenly get more out of seemingly innocent passes.
However, a more powerful infrastructure creates problems of its own,
it needs to be maintained and it causes slowdowns even in passes that
do not need all the expressive power.

> As "good enough" UD web it would be nice to have only single VDEFs on
> stores (I don't care for clobbers at call sites).  Though finding the
> optimal static partitioning to ensure this is probably hard?

Yeah, that is the whole motivation behind the dynamic aspects of
mem-ssa, but getting it right has proven tricky.  Unfortunately, I
have not had time to come back to that idea in some time.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33562

[Bug tree-optimization/33562] [4.3 Regression] aggregate DSE disabled

[rguenth at gcc dot gnu dot org]

------- Comment #10 from rguenth at gcc dot gnu dot org  2007-09-28 09:41 -------
Last patch before I stopped working on enhancing DCE:
http://gcc.gnu.org/ml/gcc-patches/2007-09/msg01978.html


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33562

[Bug tree-optimization/33562] [4.3 Regression] aggregate DSE disabled

[mmitchel at gcc dot gnu dot org]

-- 

mmitchel at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33562

[Bug tree-optimization/33562] [4.3/4.4 Regression] aggregate DSE disabled

[rguenth at gcc dot gnu dot org]

------- Comment #11 from rguenth at gcc dot gnu dot org  2008-03-14 17:02 -------
We won't fix this on the 4.3 branch.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to fail|                            |4.3.0
   Target Milestone|4.3.0                       |4.4.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33562

[Bug tree-optimization/33562] [4.3/4.4/4.5 Regression] aggregate DSE disabled

[rguenth at gcc dot gnu dot org]

------- Comment #12 from rguenth at gcc dot gnu dot org  2009-01-08 22:56 -------
Neither for GCC 4.4.  Re-targeting for GCC 4.5.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[4.3/4.4 Regression]        |[4.3/4.4/4.5 Regression]
                   |aggregate DSE disabled      |aggregate DSE disabled
   Target Milestone|4.4.0                       |4.5.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33562

[Bug tree-optimization/33562] [4.3/4.4/4.5 Regression] aggregate DSE disabled

[rguenth at gcc dot gnu dot org]

------- Comment #13 from rguenth at gcc dot gnu dot org  2010-04-06 11:19 -------
GCC 4.5.0 is being released.  Deferring to 4.5.1.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.5.0                       |4.5.1


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33562

[Bug tree-optimization/33562] [4.3/4.4/4.5/4.6 Regression] aggregate DSE disabled

[rguenth at gcc dot gnu dot org]

------- Comment #14 from rguenth at gcc dot gnu dot org  2010-07-31 09:29 -------
GCC 4.5.1 is being released, adjusting target milestone.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.5.1                       |4.5.2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33562