2010/5/21 Jan Hubicka <hubi...@ucw.cz>:
>> On Thu, May 20, 2010 at 11:21 PM, Xinliang David Li <davi...@google.com>
>> wrote:
>> > On Thu, May 20, 2010 at 2:18 PM, Steven Bosscher <stevenb....@gmail.com>
>> > wrote:
>> >> On Thu, May 20, 2010 at 11:14 PM, Xinliang David Li <davi...@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.
But a clobber for (stack) memory objects doesn't work in the granularity
we want it to be applied, does it?
Richard.
