llvm dev - Oct 2008 - [LLVMdev] A new project proposal for LLVM and calling help from a chinese student

Hi, Benoit,
Thanks very much for your advice.
You see the algorithm greatly improve the performance of liveness analysis.
However, it seems still not efficient.
First, it is inefficient in space. You have to pre-compute all Tq for every
Tq and save them, even though only the highest nodes of Tq are needed for a
given query(q,v); Second, it is inefficient in time. Given any query(q,v),
you have to  traverse all Tq to find the highest nodes. When the Tq is
large, it maybe will cost a lot. To conquer this problem, you first order
nodes according to dominance, and then the "highest node" will be the
first
node. However, when many nodes are not dominated by each other, you have to
traverse them.
In fact, I think the highest node proposed in your new slice is very similar
to the entry of SCC if the node is a loop entry. So, maybe I could use this
information to improve this algorithm, even though I don't know clearly how
to improve it now.
Thanks again, I will try to implement it in LLVM, and further more, try my
best to improve it.

Best wishes,
Star.

-----Original Message-----
From: Benoit Boissinot [mailto:bboissin at gmail.com] 
Sent: Wednesday, October 29, 2008 10:06 PM
To: LLVM Developers Mailing List
Cc: 谭明星
Subject: Re: [LLVMdev] A new project proposal for LLVM and calling help from
a chinese student

Hello,
> On Oct 28, 2008, at 10:10 AM, 谭明星 wrote:
>>
>> PS: The following are links about this paper:
>> http://portal.acm.org/citation.cfm?id=1356064
>>
http://www.if.insa-lyon.fr/chercheurs/jpbabau/emsoc/presentations/EmSoC07_Bo
issinot.pdf
>>
I've put the slides from CGO online:
http://perso.ens-lyon.fr/benoit.boissinot/upload/bboissin-liveness-cgo-slide
s.pdf
They should be much better than the one from my presentation at EmSoC.

regards,

Benoit

On Thu, Oct 30, 2008 at 01:39:46PM +0800, Star wrote:
> Hi, Benoit,
> Thanks very much for your advice.
> You see the algorithm greatly improve the performance of liveness analysis.
> However, it seems still not efficient.
> First, it is inefficient in space. You have to pre-compute all Tq for every
> Tq and save them, even though only the highest nodes of Tq are needed for a
> given query(q,v);
Sure there are probably some improvements to be done. But remember that
you don't know what the highest point is because you want the highest
point from the set "Tq intersected with the nodes dominated by the
definition".
So the highest point depends on the variable you're interested in, while
Tq only depends on the CFG (that's the point of the algorithm).

Maybe you can compute the Tq more lazily. Or use sparse bitsets.
> Second, it is inefficient in time. Given any query(q,v),
> you have to  traverse all Tq to find the highest nodes. When the Tq is
> large, it maybe will cost a lot. To conquer this problem, you first order
> nodes according to dominance, and then the "highest node" will be
the first
> node. However, when many nodes are not dominated by each other, you have to
> traverse them.
If you have no highest point, then the CFG is not reducible, this is
not the common case.
> In fact, I think the highest node proposed in your new slice is very
similar
> to the entry of SCC if the node is a loop entry. So, maybe I could use this
> information to improve this algorithm, even though I don't know clearly
how
> to improve it now.
Yes, we later discovered we can generalize the algorithm to use the loop
forest information. I don't think it makes the algorithm faster, because
you'll still have some problem with irreducible CFG.
> Thanks again, I will try to implement it in LLVM, and further more, try my
> best to improve it.
Have fun!

regards,

Benoit
-- 
:wq

This is an excellent project. We look forward to seeing your work!

Is it possible for you to implement your work on the mainline and  
contribute back patches along the way? That way, the community can  
offer suggestions and we will try *harder* not to break your pass.

Evan

On Oct 29, 2008, at 10:39 PM, Star wrote:
> Hi, Benoit,
> Thanks very much for your advice.
> You see the algorithm greatly improve the performance of liveness  
> analysis.
> However, it seems still not efficient.
> First, it is inefficient in space. You have to pre-compute all Tq  
> for every
> Tq and save them, even though only the highest nodes of Tq are  
> needed for a
> given query(q,v); Second, it is inefficient in time. Given any  
> query(q,v),
> you have to  traverse all Tq to find the highest nodes. When the Tq is
> large, it maybe will cost a lot. To conquer this problem, you first  
> order
> nodes according to dominance, and then the "highest node" will be
> the first
> node. However, when many nodes are not dominated by each other, you  
> have to
> traverse them.
> In fact, I think the highest node proposed in your new slice is very  
> similar
> to the entry of SCC if the node is a loop entry. So, maybe I could  
> use this
> information to improve this algorithm, even though I don't know  
> clearly how
> to improve it now.
> Thanks again, I will try to implement it in LLVM, and further more,  
> try my
> best to improve it.
>
> Best wishes,
> Star.
>
> -----Original Message-----
> From: Benoit Boissinot [mailto:bboissin at gmail.com]
> Sent: Wednesday, October 29, 2008 10:06 PM
> To: LLVM Developers Mailing List
> Cc: 谭明星
> Subject: Re: [LLVMdev] A new project proposal for LLVM and calling  
> help from
> a chinese student
>
> Hello,
>
>> On Oct 28, 2008, at 10:10 AM, 谭明星 wrote:
>>>
>>> PS: The following are links about this paper:
>>> http://portal.acm.org/citation.cfm?id=1356064
>>>
>
http://www.if.insa-lyon.fr/chercheurs/jpbabau/emsoc/presentations/EmSoC07_Bo
> issinot.pdf
>>>
>
> I've put the slides from CGO online:
>
http://perso.ens-lyon.fr/benoit.boissinot/upload/bboissin-liveness-cgo-slide
> s.pdf
> They should be much better than the one from my presentation at EmSoC.
>
> regards,
>
> Benoit
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev

Hi, Evan.
I'm new in LLVM project developing.
How should I work on the mainline? I have check out the latest copy of LLVM
from Subvresion using the Read-Only account. 
Do you mean I should provide the patch to the mainline periodic in this
LLVMDEV mailing list?

Anyway, thanks for your advice :)

Star
> -----Original Message-----
> From: Evan Cheng [mailto:evan.cheng at apple.com]
> Sent: Thursday, October 30, 2008 11:54 PM
> To: LLVM Developers Mailing List
> Subject: Re: [LLVMdev] A new project proposal for LLVM and calling
> helpfrom a chinese student
> 
> This is an excellent project. We look forward to seeing your work!
> 
> Is it possible for you to implement your work on the mainline and
> contribute back patches along the way? That way, the community can
> offer suggestions and we will try *harder* not to break your pass.
> 
> Evan
> 
> On Oct 29, 2008, at 10:39 PM, Star wrote:
> 
> > Hi, Benoit,
> > Thanks very much for your advice.
> > You see the algorithm greatly improve the performance of liveness
> > analysis.
> > However, it seems still not efficient.
> > First, it is inefficient in space. You have to pre-compute all Tq
> > for every
> > Tq and save them, even though only the highest nodes of Tq are
> > needed for a
> > given query(q,v); Second, it is inefficient in time. Given any
> > query(q,v),
> > you have to  traverse all Tq to find the highest nodes. When the Tq
> is
> > large, it maybe will cost a lot. To conquer this problem, you first
> > order
> > nodes according to dominance, and then the "highest node"
will be
> > the first
> > node. However, when many nodes are not dominated by each other, you
> > have to
> > traverse them.
> > In fact, I think the highest node proposed in your new slice is very
> > similar
> > to the entry of SCC if the node is a loop entry. So, maybe I could
> > use this
> > information to improve this algorithm, even though I don't know
> > clearly how
> > to improve it now.
> > Thanks again, I will try to implement it in LLVM, and further more,
> > try my
> > best to improve it.
> >
> > Best wishes,
> > Star.
> >
> > -----Original Message-----
> > From: Benoit Boissinot [mailto:bboissin at gmail.com]
> > Sent: Wednesday, October 29, 2008 10:06 PM
> > To: LLVM Developers Mailing List
> > Cc: 谭明星
> > Subject: Re: [LLVMdev] A new project proposal for LLVM and calling
> > help from
> > a chinese student
> >
> > Hello,
> >
> >> On Oct 28, 2008, at 10:10 AM, 谭明星 wrote:
> >>>
> >>> PS: The following are links about this paper:
> >>> http://portal.acm.org/citation.cfm?id=1356064
> >>>
> >
> http://www.if.insa-lyon.fr/chercheurs/jpbabau/emsoc/presentations/
> EmSoC07_Bo
> > issinot.pdf
> >>>
> >
> > I've put the slides from CGO online:
> >
> http://perso.ens-lyon.fr/benoit.boissinot/upload/bboissin-liveness
> -cgo-slide
> > s.pdf
> > They should be much better than the one from my presentation at EmSoC.
> >
> > regards,
> >
> > Benoit
> >
> >
> > _______________________________________________
> > LLVM Developers mailing list
> > LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> 
>