[Bug tree-optimization/49618] When building uClibc with GCC 4.6.1 old_atexit is miscompiled

["ebotcazou at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49618

--- Comment #10 from Eric Botcazou <ebotcazou at gcc dot gnu.org> 2011-07-04 10:14:40 UTC ---
> Eric/Richard, what do you think?  The comments seem to be fuzzy to me, some
> comments say that MEM_NOTRAP_P only apply to the position where the MEM is
> originally used (and in this case the __dso_handle var is read only guarded
> with if (__dso_handle != NULL), on the other side I wonder if we ever clear
> MEM_NOTRAP_P on unguarded DECL_WEAK var references.

I think that DECL_WEAK should always prevent MEM_NOTRAP_P from being set.  This
is a regression because of the change in set_mem_attributes_minus_bitpos,
right?

The code on the 4.5 branch reads:

      if (DECL_P (base))
    {
      if (CODE_CONTAINS_STRUCT (TREE_CODE (base), TS_DECL_WITH_VIS))
        MEM_NOTRAP_P (ref) = !DECL_WEAK (base);
      else
        MEM_NOTRAP_P (ref) = 1;
    }
      else
    MEM_NOTRAP_P (ref) = TREE_THIS_NOTRAP (base);

Maybe the first part should be reinstated.