This is the mail archive of the gcc@gcc.gnu.org mailing list for the GCC project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: Where does the time go?


> On Thu, May 20, 2010 at 11:21 PM, Xinliang David Li <davidxl@google.com> wrote:
> > On Thu, May 20, 2010 at 2:18 PM, Steven Bosscher <stevenb.gcc@gmail.com> wrote:
> >> On Thu, May 20, 2010 at 11:14 PM, Xinliang David Li <davidxl@google.com> wrote:
> >>> stack variable overlay and stack slot assignments is here too.
> >>
> >> Yes, and for these I would like to add a separate timevar. Agree?
> >
> > Yes. ?(By the way, we are rewriting this pass to eliminate the code
> > motion/aliasing problem -- but that is a different topic).
> 
> Btw, we want to address the same problem by representing the
> points where (big) variables go out-of scope in the IL, also to
> help DSE.  The original idea was to simply drop in an aggregate
> assignment from an undefined value at the end of the scope
> during lowering, like
> 
>   var = {undefined};
> 
> which we'd expand to nothing.  Of course shifting the problem to
> the RTL optimizers, so better expand to a similar RTL construct.
> But then are you addressing the similar problem on the RTL side?

Well, RTL already has the clobber insns, that are pretty much what you need
(and RTL land plays with this at least for double word arithmetic). But
I am not quite sure how much of DSE we want to deffer to RTL.

Honza
> 
> Richard.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]