[PATCH] D79972: [OpenMP5.0] map item can be non-contiguous for target update

[Alexey Bataev via Phabricator via cfe-commits]

ABataev added a comment.

In D79972#2069366 <https://reviews.llvm.org/D79972#2069366>, @cchen wrote:

> In D79972#2069358 <https://reviews.llvm.org/D79972#2069358>, @ABataev wrote:
>
> > In D79972#2069322 <https://reviews.llvm.org/D79972#2069322>, @cchen wrote:
> >
> > > In D79972#2068976 <https://reviews.llvm.org/D79972#2068976>, @ABataev wrote:
> > >
> > > > Still: Did you think about implementing it in the compiler instead of the runtime?
> > >
> > >
> > > I'm not sure I understand your question, which part of code are you asking?
> > >  The main work compiler needs to do is to send the {offset, count, stride} struct to runtime.
> >
> >
> > I mean did you think about calling `__tgt_target_data_update` function in a loop in the compiler-generated code instead of putting it into the runtime?
>
>
> Oh, I would prefer to call `tgt_target_data_update` once in the compiler and I'm also doing it now.


I was not quite correct. What I mean, is to generate the array with the array section as VLA in the compiler, and fill it in the loop generated by the compiler for non-contiguous sections but not in the runtime?
Say, we have the code:

  int arr[3][3]
  ...
   #pragma omp update to(arr[1:2][1:2]

In this case, we're going to transfer the next elements:

  000
  0xx
  0xx

In the compiler-generated code we emit something like this:

  void *bptr[<n>];
  void *ptr[<n>];
  int64 sizes[<n>];
  int64 maptypes[<n>];
  for (int i = 0; i < <n>; ++i) {
    bptr[i] = &arr[1+i][1];
    ptr[i] = &arr[1+i][1];
    sizes[i] = ...;'
    maptypes[i] = ...;
  }
  call void @__tgt_target_data_update(i64 -1, i32 <n>, bptr, ptr, sizes, maptypes);

With this solution, you won't need to modify the runtime and add a new mapping flag.


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