ALLOCATE/DEALLOCATE statements for module allocatable variable with the
pinned attribute can be lowered to the standard runtime call and do not
need further action since these variables will have a unique descriptor
that is on the host.
In device context managed memory is not available so it makes no sense
to allocate the descriptor using it. Fall back to fir.alloca as it is
handled well in device code.
cuf.free is just dropped.
This patch adds entry point in the runtime to be able to allocate
descriptors in managed memory. These entry points currently only call
`CUFAllocManaged` and `CUFFreeManaged` but could be more complicated in
the future.
`cuf.alloc` and `cuf.free` related to local descriptors are converted
into runtime calls.
Allocator can be specified in the descriptor. For simple local
allocatable, we can simply convert `cuf.allocate`/`cuf.deallocate` to
their corresponding runtime calls in the standard flang runtime. More
specific cases will require dedicated entry points. Global descriptor
will require sync between host and device copy.
This patch adds a pass to perform this conversion.
