http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51663
--- Comment #9 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-03-26
07:05:58 UTC ---
(In reply to comment #8)
> The inconsistency should be solved. The question however is what kind of
> behaviour we want at -O0 from LTO.
>
> It seems to me that at -O0 the LTO/non-LTO output should be as close as
> possible and thus LTO should not privatize symbols and break more silly
> debuggers/tools (this is especially important for SLIM mode).
>
> We still do renaming of statics and other nasty things, but we should not do
> more than neccesary.
>
> On the the other hand, I think -fwhole-program should still do privatization.
> This patch implements it. In addition to this it drops more unobvious
> transformation from -fwhole-program where we bring local COMDAT virtual tables
> and functions w/o address taken since we know duplicating them does not hurt.
>
> Does this look sane?
Yes. I think for -O0 -flto we should default to 1:1 partitioning and
_not_ do the renaming of local symbols though ... of course -O0 -flto
does not make too much sense?
> Honza
>
> Index: ipa.c
> ===================================================================
> --- ipa.c (revision 185777)
> +++ ipa.c (working copy)
> @@ -616,7 +616,8 @@ cgraph_externally_visible_p (struct cgra
> if (TARGET_DLLIMPORT_DECL_ATTRIBUTES
> && lookup_attribute ("dllexport", DECL_ATTRIBUTES (node->decl)))
> return true;
> - if (node->resolution == LDPR_PREVAILING_DEF_IRONLY)
> + if (node->resolution == LDPR_PREVAILING_DEF_IRONLY
> + && optimize)
> return false;
> /* When doing LTO or whole program, we can bring COMDAT functoins static.
> This improves code quality and we know we will duplicate them at most
> twice
> @@ -624,11 +625,13 @@ cgraph_externally_visible_p (struct cgra
> implementing same COMDAT) */
> if ((in_lto_p || whole_program)
> && DECL_COMDAT (node->decl)
> + && optimize
> && cgraph_comdat_can_be_unshared_p (node))
> return false;
>
> /* When doing link time optimizations, hidden symbols become local. */
> if (in_lto_p
> + && optimize
> && (DECL_VISIBILITY (node->decl) == VISIBILITY_HIDDEN
> || DECL_VISIBILITY (node->decl) == VISIBILITY_INTERNAL)
> /* Be sure that node is defined in IR file, not in other object
> @@ -681,7 +684,8 @@ varpool_externally_visible_p (struct var
> This is needed for i.e. references from asm statements. */
> if (varpool_used_from_object_file_p (vnode))
> return true;
> - if (vnode->resolution == LDPR_PREVAILING_DEF_IRONLY)
> + if (vnode->resolution == LDPR_PREVAILING_DEF_IRONLY
> + && optimize)
> return false;
>
> /* As a special case, the COMDAT virutal tables can be unshared.
> @@ -690,6 +694,7 @@ varpool_externally_visible_p (struct var
> is faster for dynamic linking. Also this match logic hidding vtables
> from LTO symbol tables. */
> if ((in_lto_p || flag_whole_program)
> + && optimize
> && !vnode->force_output
> && DECL_COMDAT (vnode->decl) && DECL_VIRTUAL_P (vnode->decl))
> return false;
