RE: [PATCH] Use rtx_refs_may_alias_p instead of alias_sets_conflict_p in

["Bingfeng Mei" <bmei at broadcom dot com>]

> -----Original Message-----
> From: Richard Guenther [mailto:richard.guenther@gmail.com]
> Sent: 04 August 2010 16:02
> To: Diego Novillo
> Cc: Bingfeng Mei; gcc-patches@gcc.gnu.org
> Subject: Re: [PATCH] Use rtx_refs_may_alias_p instead of
> alias_sets_conflict_p in
> 
> On Wed, Aug 4, 2010 at 4:58 PM, Richard Guenther
> <richard.guenther@gmail.com> wrote:
> > On Wed, Aug 4, 2010 at 4:57 PM, Richard Guenther
> > <richard.guenther@gmail.com> wrote:
> >> On Wed, Aug 4, 2010 at 4:56 PM, Diego Novillo <dnovillo@google.com>
> wrote:
> >>> On Wed, Aug 4, 2010 at 14:52, Bingfeng Mei <bmei@broadcom.com>
> wrote:
> >>>
> >>>> 2010-08-04 ?Bingfeng Mei ?<bmei@broadcom.com>
> >>>>
> >>>> ? ? ? ?* alias.c (walk_mems_2): Call rtx_refs_may_alias_p
> >>>> ? ? ? ?instead of alias_sets_conflict_p to get more accurate
> >>>> ? ? ? ?alias set information.
> >>>
> >>> OK.
> >>
> >> Wait. ?You need to use a proper dependence function instead,
> >> rtx_refs_may_alias_p isn't supposed to be used directly.
> >
> > Which would be true_dependence if using TBAA is valid here
> > (which I am not sure).
> 
> After this patch insn_alias_sets_conflict_p is also seriously
> misnamed.  As it is used only from within ddg.c it should
> be moved there and made private.

So I need to make rtx_refs_may_alias_p global? 

> 
> /* Given two nodes, analyze their RTL insns and add inter-loop mem deps
>    to ddg G.  */
> static void
> add_inter_loop_mem_dep (ddg_ptr g, ddg_node_ptr from, ddg_node_ptr to)
> {
>   if (!insn_alias_sets_conflict_p (from->insn, to->insn))
>     /* Do not create edge if memory references have disjoint alias sets.
> */
>     return;
> 
> the comment ("inter-loop mem deps") suggests that using TBAA
> is not valid here.
Does TBAA mean type-based alias analysis? Why is it not valid here? 

> 
> Richard.
> 
> > Richard.
> >
> >> Richard.
> >>
> >>>
> >>> Diego.
> >>>
> >>
> >