[gomp4 06/14] omp-low: copy omp_data_o to shared memory on NVPTX

[Bernd Schmidt]

On 10/21/2015 11:07 AM, Alexander Monakov wrote:

> In PTX, stack storage is in .local address space -- and that memory is
> thread-private.  A thread can make a pointer to its own stack memory and
> successfully dereference it, but dereferencing that pointer from other threads
> does not work (I observed it returning garbage values).
>
> The reason for .local addresses being private like that, I think, is that
> references to .local memory undergo address translation to make simultaneous
> accesses to stack slots from threads in a warp form a coalesced memory
> transaction.  So .local memory looking consecutive from an individual thread's
> point of view are actually strided in physical memory.

This sounds a little odd. You can convert a .local pointer to a generic 
one and dereference the latter. Do you think there is such 
behind-the-scenes magic going on for accesses through generic pointers?


Bernd