[PATCH] check alias sets in add_inter_loop_mem_dep (ddg.c)

Bingfeng Mei bmei@broadcom.com
Tue Jan 20 13:23:00 GMT 2009


Hello,
Does that mean my patch is approved? I am new to the procedures. 
I am wondering what is next step? Will someone with SVN write permission 
do check-in for me? Thanks.

Bingfeng  

> -----Original Message-----
> From: Daniel Berlin [mailto:dberlin@dberlin.org] 
> Sent: 19 January 2009 18:55
> To: Revital1 Eres
> Cc: Bingfeng Mei; Andrey Belevantsev; Ayal Zaks; 
> gcc-patches@gcc.gnu.org
> Subject: Re: [PATCH] check alias sets in 
> add_inter_loop_mem_dep (ddg.c)
> 
> On Mon, Jan 19, 2009 at 4:59 AM, Revital1 Eres 
> <ERES@il.ibm.com> wrote:
> > Hello,
> >
> >> I asked on the GCC mailing list about the DDG export patch 
> a few months
> > ago. I
> >> tried to merged it recently into the mainline, without 
> much success. A
> >> immediate issue I have with modulo scheduling is that it 
> doesn't handle
> >> restrict keyword. I just adapt these the walker functions 
> in the above
> > patch,
> >> which I think is generic and simple.
> >
> > OK, thanks.
> > I am a little confused regarding how alias_sets_conflict_p 
> will handle
> > cross-iteration dependencies when constructing DDG for SMS.
> >
> > From previous talks with Andrey I understood that data dependency
> > graph construction for SMS can not use rtl alias analysis 
> because of the
> > following explanation:
> > When adding cross-iteration dependencies, because rtl AA includes
> > base+offset disambiguation, which allows to disambiguate 
> a[i] and a[i+1]
> > on targets with base+offset memory addressing; while a[i] and a[i+1]
> > are independent within one iteration, cross-iteration 
> dependency still
> > must be added; thus, DDG construction adds dependency edges for all
> > pairs of memory references.
> 
> You can check the alias sets without having to check the base+offset,
> which is what Bingfeng's patch does.
> If the alias sets do not conflict, they will *never* be aliased,
> cross-iteration or otherwise.
> 
> --Dan
> 
> 



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