[mlir][gpu][transforms] Add support for mapping to lanes (#146912)

This revision adds a new attribute for mapping `scf.forall` to linear
lane ids.

Example:
```
    // %arg2 and %arg3 map to lanes [0, 6) and are turned into epxressions
    // involving threadIdx.x/y by the map_nested_forall_to_threads
    // transformation. This results in a if (linear_thread_id < 6) conditional.
    scf.forall (%arg2, %arg3) in (2, 3) {
       ...
    } {mapping = [#gpu.lane<linear_dim_0>, #gpu.lane<linear_dim_1>]}
 ```

---------

Co-authored-by: Oleksandr "Alex" Zinenko <git@ozinenko.com>

0 files changed, 0 insertions, 0 deletions