[LLVMdev] 64-bit to 32-bit conversion of pointers

[Vikram S. Adve]

I believe the Intel compiler (icc) has an option to use 32-bit  
pointers on a 64-bit machine like Itanium.  So the programer  
effectively specifies that a 4GB address space is sufficient.

We also have a research paper on this topic but the effectiveness  
depends heavily on the effectiveness of Automatic Pool Allocation and  
the underlying pointer analysis:
	http://llvm.org/pubs/2005-06-12-MSP-PointerComp.html
Andrew Lenharth has a prototype of this but it has lots of limitations.

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



On May 15, 2008, at 8:06 PM, Bill Wendling wrote:

> On Thu, May 15, 2008 at 5:45 PM, Fernando Magno Quintao Pereira
> <fernando at cs.ucla.edu> wrote:
>>
>> Guys, I need advice in how to handle a problem.
>>
>> The problem:
>>    In X86_64, pointers are 64-bit variables, and are stored into 64- 
>> bit
>> registers. However, some pointers are small enough that they can be
>> represented as 32-bit values.
>>    Is there some way, in LLVM, to recognize which pointers can be  
>> stored
>> into 32-bit registers, and so modify their class accordingly? Any  
>> ideas or
>> hints would be appreciated.
>>
> I don't think so. It really depends upon where the OS loads the
> program into memory, the virtual address space, etc. It's not
> something that the compiler itself is aware of. The only thing I can
> think of is forcing the OS to use the lower 32-bit address space for
> loading the program and creating ths stacks and heap space...
>
> -bw
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev