[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.