llvm dev - Oct 2007 - [LLVMdev] malloc() vs. MallocInst

Hi,

I recently looked quite some time for why poolalloc wouldn't transform calls
to malloc() in my program, until I noticed that it handles calls to malloc() 
(eg, stdlib pass) -- but only transforms MallocInst's.

Is there a general policy on how passes should behave? Should they handle both 
representations, is doing -raiseallocs the preferred way, or do we 
explicitely not want any single policy (ie, are there any hidden problems)?
Perhaps this could also get a FAQ entry or sth. like that.

Torvald

On Sat, 27 Oct 2007, Torvald Riegel wrote:
> I recently looked quite some time for why poolalloc wouldn't transform
calls
> to malloc() in my program, until I noticed that it handles calls to
malloc()
> (eg, stdlib pass) -- but only transforms MallocInst's.
>
> Is there a general policy on how passes should behave? Should they handle
both
> representations, is doing -raiseallocs the preferred way, or do we
> explicitely not want any single policy (ie, are there any hidden problems)?
> Perhaps this could also get a FAQ entry or sth. like that.
Generally passes should assume that they are operating on a canonical form 
of the program if some other pass provides that.  In this case, because 
raiseallocs transforms malloc calls into malloc instructions, it is very 
reasonable for poolalloc to assume everything is using the instruction 
form.

Likewise, DSA and poolalloc will be significantly less precise and useful 
if you run it on a .bc file that has not yet been optimized.

-Chris

-- 
http://nondot.org/sabre/
http://llvm.org/

Torvald,

For what are you interested in poolalloc?  I'm asking because we are  
trying to decide how to prioritize work on it.  Thanks,

--Vikram
http://www.cs.uiuc.edu/~vadve
http://llvm.org


On Oct 27, 2007, at 11:10 AM, Torvald Riegel wrote:
> Hi,
>
> I recently looked quite some time for why poolalloc wouldn't  
> transform calls
> to malloc() in my program, until I noticed that it handles calls to  
> malloc()
> (eg, stdlib pass) -- but only transforms MallocInst's.
>
> Is there a general policy on how passes should behave? Should they  
> handle both
> representations, is doing -raiseallocs the preferred way, or do we
> explicitely not want any single policy (ie, are there any hidden  
> problems)?
> Perhaps this could also get a FAQ entry or sth. like that.
>
> Torvald
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev

Hi Vikram,

I want to use poolalloc as a means for partitioning memory in Software 
Transactional Memory. We will have a paper about tuning parameters in 
word-based STMs in PPoPP 08, but there we use one configuration for the 
complete TM, which obviously has limitations in heterogenous workloads. 

Partitioning with poolalloc should give me (1) hopefully meaningful partitions 
(ie, datastructures) with locality without requiring user annotations, (2) 
spatial locality that can make runtime partition lookup easier (eg, table 
entries per page), and (3) type-information for pools. I already mentioned 
partitioning briefly in one of our previous conversations (and you pointed 
out the usefulness of poolalloc for partitioning :), but I was too busy 
during the summer to really work on this. I was initially aiming for a not 
far away deadline, but I'm behind schedule so I'll have to see how fast
I can
be.

The only issues that poolalloc has for me right now is that (a) passing things 
through pthread_create() doesn't work out of the box and (b) node collapsing
when I enable llvm-ld optimizations. I guess I can do sth. about (a) (I've 
been already talking about this with Andrew), and (b) is not critical either.

I've seen that you too have a PPoPP paper, congratulations. Is it related
(or
could I get a (draft) copy)?
Which kinds of work do you have to prioritize, if I may ask? Perhaps I can 
then give you better input. Eg, (a) could be useful for poolalloc (although 
my solutions could be too TM specific).
If there should be an overlap in research interests and we could collaborate, 
that would be great as well.

Thanks for the support,

Torvald


On Monday 29 October 2007, Vikram S. Adve wrote:
> Torvald,
>
> For what are you interested in poolalloc?  I'm asking because we are
> trying to decide how to prioritize work on it.  Thanks,
>
> --Vikram
> http://www.cs.uiuc.edu/~vadve
> http://llvm.org
>
> On Oct 27, 2007, at 11:10 AM, Torvald Riegel wrote:
> > Hi,
> >
> > I recently looked quite some time for why poolalloc wouldn't
> > transform calls
> > to malloc() in my program, until I noticed that it handles calls to
> > malloc()
> > (eg, stdlib pass) -- but only transforms MallocInst's.
> >
> > Is there a general policy on how passes should behave? Should they
> > handle both
> > representations, is doing -raiseallocs the preferred way, or do we
> > explicitely not want any single policy (ie, are there any hidden
> > problems)?
> > Perhaps this could also get a FAQ entry or sth. like that.
> >
> > Torvald
> > _______________________________________________
> > LLVM Developers mailing list
> > LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev