[LLVMdev] memory lifetime and invariance

John McCall rjmccall at apple.com
Wed May 20 12:25:55 CDT 2009


On May 20, 2009, at 9:25 AM, Andrew Lenharth wrote:
> On Mon, May 18, 2009 at 3:02 PM, Chris Lattner <clattner at apple.com>  
> wrote:
>> FYI, I wrote up some thoughts on this here:
>> http://nondot.org/sabre/LLVMNotes/MemoryUseMarkers.txt
>>
>> The intention is to allow front-ends to express things like "I know
>> this memory is a constant in this region" and to allow the optimizer/
>> codegen to perform more aggressive stack slot merging.
>
> It seems no more prone to abuse to reserve an address space for const
> memory.  Within a const region, all pointers to the const data are in
> the const address space.  So rather than starting with a intrinsic,
> you start with a ptrcast.  This would also make checking trivial
> stores to const regions easy in the verifier.

This would also make it very easy for a front-end to handle write-once  
data.

Is there a design document about address spaces?

John.


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