[llvm-branch-commits] [Flang][OpenMP][MLIR] Extend derived (record) type map support in Flang OpenMP by adding some initial support for explicit member mapping (PR #81511)

[via llvm-branch-commits]

https://github.com/agozillon created https://github.com/llvm/llvm-project/pull/81511

This patch is one in a series of four patches that seeks to refactor
slightly and extend the current record type map support that was
put in place for Fortran's descriptor types to handle explicit
member mapping for record types at a single level of depth.

For example, the below case where two members of a Fortran
derived type are mapped explicitly:

''''
  type :: scalar_and_array
    real(4) :: real
    integer(4) :: array(10)
    integer(4) :: int
  end type scalar_and_array
  type(scalar_and_array) :: scalar_arr

  !$omp target map(tofrom: scalar_arr%int, scalar_arr%real)
''''

Current cases of derived type mapping left for future work are:
  > explicit member mapping of nested members (e.g. two layers of
     record types where we explicitly map a member from the internal
     record type)
  > Fortran's automagical mapping of all elements and nested elements
     of a derived type
  > explicit member mapping of a derived type and then constituient members
     (redundant in Fortran due to former case but still legal as far as I am aware)
  > explicit member mapping of a record type (may be handled reasonably, just
     not fully tested in this iteration)
  > explicit member mapping for Fortran allocatable types (a variation of nested
     record types)

This patch seeks to support this by extending the Flang-new OpenMP lowering to
support generation of this newly required information, creating the neccessary
parent <-to-> member map_info links, calculating the member indices and
setting if it's a partial map.

The OMPDescriptorMapInfoGen pass has also been generalized into a map
finalization phase, now named OMPMapInfoFinalization. This pass was extended
to support the insertion of member maps into the BlockArg and MapOperands of
relevant map carrying operations. Similar to the method in which descriptor types
are expanded and constituient members inserted.