llvm dev - May 2009 - [LLVMdev] How to use the PoolDescriptor in ds-aa alias analysis?

Dear Staff,
     I am reading the paper "Making Context-sensitive Points-to  
Analysis with Heap Cloning Practical For The Real World", and I build  
the poolalloc module, and run the program in Figure 1 in this paper  
with -ds-aa alias analysis. Now I know that X and Y in the program  
would have distinct PoolDescriptors to make them disjoint data  
structures.
     However, how can we use the PoolDescriptor? What is storing in  
it? It seems that the PoolDescriptor in the program is just parsed as  
an argument from top to down, but it is not modified, so I am a little  
confused.

Thanks,
Heming

On Friday 08 May 2009, hc2428 at columbia.edu wrote:
> Dear Staff,
>      I am reading the paper "Making Context-sensitive Points-to
> Analysis with Heap Cloning Practical For The Real World", and I build
> the poolalloc module, and run the program in Figure 1 in this paper
> with -ds-aa alias analysis. Now I know that X and Y in the program
> would have distinct PoolDescriptors to make them disjoint data
> structures.
>      However, how can we use the PoolDescriptor? What is storing in
> it? It seems that the PoolDescriptor in the program is just parsed as
> an argument from top to down, but it is not modified, so I am a little
> confused.
Pool descriptors get allocated before the data in the pool starts to exist. 
After that, pointers to those pool descriptors get passed around. If you are 
the only poolalloc user, then you can use the pools in any way you want. If 
you just want an ID for a pool, it should be safe to not release pools and 
just return unique pointers from the pool allocator.

Torvald

On May 8, 2009, at 7:03 AM, Torvald Riegel wrote:
> On Friday 08 May 2009, hc2428 at columbia.edu wrote:
>> Dear Staff,
>>     I am reading the paper "Making Context-sensitive Points-to
>> Analysis with Heap Cloning Practical For The Real World", and I
build
>> the poolalloc module, and run the program in Figure 1 in this paper
>> with -ds-aa alias analysis. Now I know that X and Y in the program
>> would have distinct PoolDescriptors to make them disjoint data
>> structures.
>>     However, how can we use the PoolDescriptor? What is storing in
>> it? It seems that the PoolDescriptor in the program is just parsed as
>> an argument from top to down, but it is not modified, so I am a  
>> little
>> confused.
>
> Pool descriptors get allocated before the data in the pool starts to  
> exist.
> After that, pointers to those pool descriptors get passed around. If  
> you are
> the only poolalloc user, then you can use the pools in any way you  
> want. If
> you just want an ID for a pool, it should be safe to not release  
> pools and
> just return unique pointers from the pool allocator.

And if you are only interested in the alias analysis client you  
mentioned (-ds-aa), then you don't need to run the pool allocation  
transformation at all.  That's just another client that gives you a  
*run-time* representation of the points-to sets.

>
>
> Torvald
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