This is a patch in preparation for the support stream ordered memory
allocator in CUDA Fortran.
This patch adds an asynchronous id to the AllocatableAllocate runtime
function and to Descriptor::Allocate so it can be passed down to the
registered allocator. It is up to the allocator to use this value or
not.
A follow up patch will implement that asynchronous allocator for CUDA
Fortran.
This runtime API can be used to lower any flavor of array constructors,
but is mainly intended to be used with:
- array constructors for which the extent or length parameters cannot
be computed without lowering some ac-value or ac-implied-do-control
that cannot be pre-evaluated.
- array constructors of a derived type with allocatable component where
copy is not trivial or PDTS.
Example of use cases:
- `[((i+j,i=1, ifoo()), j=1,n)]` where ifoo() is not pure.
- `[return_allocatable_array(), return_allocatable_array()]`
Differential Revision: https://reviews.llvm.org/D144411
