Markus,
My experience with an architecture like this also is a GPU: the Nvidia CUDA
GPUs. I don't work on nvcc. I'm coming at this from the consumer side. But
what I've observed:
They use DW_AT_address_class with a CUDA-specific enum of address spaces, with
values for things like: global memory, shared memory, const memory, etc. They
don't attach these attributes to subroutines, because all the code on that
architecture is in a single "code" memory. They do attach them to pointer
types, as the DWARF spec describes. They also attach them to variables,
formals, etc. That's a vendor extension (which I'd forgotten until I looked it
up again in the DWARF spec). But an obvious one. We might want to formalize it
at some point.
Anyway, these are the sorts of things we see:
DW_TAG_pointer_type
DW_AT_type : ...
DW_AT_address_class : ptxGenericStorage
DW_TAG_variable
DW_AT_name : myConstant
DW_AT_type : ...
DW_AT_location : ...
DW_AT_address_class : ptxConstStorage
DW_TAG_variable
DW_AT_abstract_origin : ...
DW_AT_location : ...
DW_AT_address_class : ptxLocalStorage
I don't know your architecture, but I'd expect something similar to work for any
GPU with heterogeneous memories.
--
Todd Allen
Concurrent Real-Time
On Mon, Jul 20, 2020 at 08:31:53AM +0000, Dwarf Discussion wrote:
> Hello Michael,
>
> > > What would be the recommended way to model variables that are allocated
> > > to different address spaces?
> >
> > Can you describe the architecture a bit?
>
> It's a GPU. It uses a different address space for shared local memory.
>
>
> > > I found DW_OPT_xderef for dereferencing address-space qualified pointers
> > > but the resulting memory location description wouldn???t have an
> > > address-space qualifier.
> >
> > DW_OPT_xderef translates from an architecturally defined memory
> > reference including an address space into a linear address space
> > (generic type). DWARF doesn't support computations on address-space
> > qualified addresses, although using a typed stack, this could be an
> > extension.
>
> I don't see a need for this, right now. It should suffice to describe that an
> object lives in address-space A so the location expression yields an
> A-address.
>
> In another email you said: "
> CUDA address spaces or a DSP with multiple distinct address spaces are
> what would conventionally be described as segmented memory. I think
> that using the DW_AT_address_space would be reasonable.
> ".
>
> I assume you mean DW_AT_address_class. This should do the trick. I just
> wasn't
> sure if that's the intended use of that attribute.
>
>
> > > I found DW_AT_address_class, which allows attaching an integer, which
> > > could represent the address-space. This sounds pretty close. I???m a bit
> > > thrown off by the example, though.
> >
> > Which example?
>
> Table 2.7 "Example address class codes" on p. 48. It uses DW_AT_address_class
> to describe addressing modes.
>
> Regards,
> Markus.
> Intel Deutschland GmbH
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