[LLVMdev] Address space extension

[Matt Arsenault]

On Aug 8, 2013, at 7:19 , Michele Scandale <michele.scandale at gmail.com> wrote:

> On 08/08/2013 02:52 PM, Micah Villmow wrote:
>> This is something I proposed last year, so you might want to read up on that discussion first.
>> 
>> You can find it here:
>> http://lists.cs.uiuc.edu/pipermail/llvmdev/2012-September/053277.html
> 
> Uhm... I read the discussion, probably I've not understood the problem well: the conclusion (it has been committed?) is that to handle address space conversion that imply a change in the size of pointers must be expressed as a pair ptrtoint/inttoptr. What if the address space conversione logically change also the value of the pointer?

I recently committed patches to reject bitcasts if the address space pointers are different sizes, and accept them if they are the same size as was concluded in the thread. I would like to reject all cross address space bitcasts since it would make some things simpler, but when I tried to do that it broke a good number of optimization tests that would be a lot of work to fix.

I have the auto upgrade for turning bitcasts into inttoptr/ptrtoint implemented, but it isn't necessary with the current rule that same sized pointer bitcasts are allowed. This would be always necessary if all cross address space bitcasts were disallowed.