[Bug middle-end/48668] New: [4.6/4.7 regression] COMDAT Group signature not emitted in group

[Bug middle-end/48668] New: [4.6/4.7 regression] COMDAT Group signature not emitted in group

[ro at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48668

           Summary: [4.6/4.7 regression] COMDAT Group signature not
                    emitted in group
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: ro@gcc.gnu.org
                CC: hubicka@gcc.gnu.org
              Host: i386-pc-solaris2.11
            Target: i386-pc-solaris2.11
             Build: i386-pc-solaris2.11


I'm currently putting the finishing touches to the COMDAT-with-as patch

  [build, c++, lto] Support COMDAT group with Sun as (PR target/40483)
  http://gcc.gnu.org/ml/gcc-patches/2010-05/msg01365.html
  http://gcc.gnu.org/ml/gcc-patches/2010-06/msg00600.html

When I retested the patch on mainline, I found that there's a single
regression:

FAIL: g++.dg/opt/thunk2.C (test for excess errors)
WARNING: g++.dg/opt/thunk2.C compilation failed to produce executable

Excess errors:
Assembler: thunk2.C
    "/var/tmp//ccLuaW10.s", line 219 : Group Id symbol defined outside of group

This error didn't happen when I originally developed the patch based on GCC
4.5.
Sun as is right, though: the signature symbol _ZN1U3fooEi (U::foo(int)) is
defined inside a group with signature  _ZThn4_N1U3fooEi (non-virtual thunk to
U::foo(int)).  The same happens with gas, which seems to be far more lazy
accepting stuff like this.

A reghunt revealed that this regression was introduced by this patch:

2010-09-29  Jan Hubicka  <jh@suse.cz>

       * cgraphunit.c (assemble_function): Output thunks and aliases before
       the function itself.

http://gcc.gnu.org/ml/gcc-patches/2010-10/msg00354.html

I don't think that the submission contains enough justification for this, and
the result seems to be plain wrong.

I'm attaching the assembler output (with gas since the affected patch isn't
yet integrated) without and with the patch.

It seems like the easiest fix would be to just revert the patch.

[Bug middle-end/48668] [4.6/4.7 regression] COMDAT Group signature not emitted in group

[ro at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48668

--- Comment #1 from Rainer Orth <ro at gcc dot gnu.org> 2011-04-18 17:02:32 UTC ---
Created attachment 24037
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=24037
assembler output before and after the culprit patch

[Bug middle-end/48668] [4.6/4.7 regression] COMDAT Group signature not emitted in group

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48668

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |wrong-code
   Target Milestone|---                         |4.6.1

[Bug middle-end/48668] [4.6/4.7 regression] COMDAT Group signature not emitted in group

[hubicka at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48668

--- Comment #2 from Jan Hubicka <hubicka at gcc dot gnu.org> 2011-05-05 15:30:32 UTC ---
Hi,
I am not 100% I understand the problem.  For 4.6 we indeed probably should go
with reverting to prevous order. 
We are trying to output both the function itself and its thunk into single
named comdat group. The difference is that before patch we first output the
function itself and then the thunk. With the patch we output stuff other way
around.
So the signature always come from the first symbol within the group and there
is no way to output the thunk first (since its symbol is different) and the
function later?
I don't see how the symbol is outside of the group given that both symbols came
into same comdat section.

Honza

[Bug middle-end/48668] [4.6/4.7 regression] COMDAT Group signature not emitted in group

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48668

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |WAITING
   Last reconfirmed|                            |2011.06.12 13:09:43
     Ever Confirmed|0                           |1

--- Comment #3 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-06-12 13:09:43 UTC ---
Q unanswered.

[Bug middle-end/48668] [4.6/4.7 regression] COMDAT Group signature not emitted in group

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48668

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.6.1                       |4.6.2

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-06-27 12:32:39 UTC ---
GCC 4.6.1 is being released.

[Bug middle-end/48668] [4.6/4.7 regression] COMDAT Group signature not emitted in group

[hubicka at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48668

--- Comment #5 from Jan Hubicka <hubicka at gcc dot gnu.org> 2011-10-16 09:02:38 UTC ---
Author: hubicka
Date: Sun Oct 16 09:02:33 2011
New Revision: 180053

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=180053
Log:

    PR target/48668
    PR target/50689
    * cgraphunit.c (cgraph_expand_function): Expand thunks and alises
    after function body.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/cgraphunit.c

[Bug middle-end/48668] [4.6/4.7 regression] COMDAT Group signature not emitted in group

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48668

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.6.2                       |4.6.3

--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-10-26 17:13:21 UTC ---
GCC 4.6.2 is being released.

[Bug middle-end/48668] [4.6/4.7 regression] COMDAT Group signature not emitted in group

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48668

--- Comment #7 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-10-27 09:35:38 UTC ---
Fixed on trunk?  Still broken on the branch?  Does backporting the patch
help there?

[Bug middle-end/48668] [4.6 regression] COMDAT Group signature not emitted in group

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48668

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org
            Summary|[4.6/4.7 regression] COMDAT |[4.6 regression] COMDAT
                   |Group signature not emitted |Group signature not emitted
                   |in group                    |in group

--- Comment #8 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-01-05 17:19:06 UTC ---
Assuming fixed on the trunk.  If not, please respond to Richard's questions and
provide details.

[Bug middle-end/48668] [4.6 regression] COMDAT Group signature not emitted in group

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48668

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.6.3                       |4.6.4

--- Comment #9 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-03-01 14:38:08 UTC ---
GCC 4.6.3 is being released.

[Bug middle-end/48668] [4.6 regression] COMDAT Group signature not emitted in group

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48668

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|4.6.4                       |4.7.0

--- Comment #10 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-04-12 16:17:26 UTC ---
The 4.6 branch has been closed, fixed in GCC 4.7.0.