Extend the depend clause to support `!omp.iterated<Ty>` handles
alongside plain depend vars, so the IR can represent both forms.
Assisted with copilot
This is part of feature work for
https://github.com/llvm/llvm-project/issues/188061
This PR shifts from using the LLVM OpenMP enumerator bit flags to an
OpenMP dialect specific enumerator. This allows us to better represent
map types that wouldn't be of interest to the LLVM backend and runtime
in the dialect.
Primarily things like
ref_ptr/ref_ptee/ref_ptr_ptee/atach_none/attach_always/attach_auto which
are of interest to the compiler for certrain transformations (primarily
in the FIR transformation passes dealing with mapping), but the runtime
has no need to know about them. It also means if another OpenMP
implementation comes along they won't need to stick to the same bit flag
system LLVM chose/do leg work to address it.
This PR introduces a new pass "lower-workdistribute"
Fortran array statements are lowered to fir as fir.do_loop unordered.
"lower-workdistribute" pass works mainly on identifying "fir.do_loop
unordered" that is nested in target{teams{workdistribute{fir.do_loop
unordered}}} and lowers it to
target{teams{parallel{wsloop{loop_nest}}}}. It hoists all the other ops
outside target region. Relaces heap allocation on target with
omp.target_allocmem and deallocation with omp.target_freemem from host.
Also replaces runtime function "Assign" with omp.target_memcpy from
host.
This pass implements following rewrites and optimisations:
- **FissionWorkdistribute**: finds the parallelizable ops within teams
{workdistribute} region and moves them to their own
teams{workdistribute} region.
- **WorkdistributeRuntimeCallLower**: finds the FortranAAssign calls
nested in teams {workdistribute{}} and lowers it to unordered do loop if
src is scalar and dest is array. Other runtime calls are not handled
currently.
- **WorkdistributeDoLower**: finds the fir.do_loop unoredered nested in
teams {workdistribute{fir.do_loop unoredered}} and lowers it to teams
{parallel { distribute {wsloop {loop_nest}}}}.
- **TeamsWorkdistributeToSingle**: hoists all the ops inside teams
{workdistribute{}} before teams op.
The work in this PR is C-P and updated from @ivanradanov commits from
coexecute implementation:
[flang_workdistribute_iwomp_2024](https://github.com/ivanradanov/llvm-project/commits/flang_workdistribute_iwomp_2024)
Paper related to this work by @ivanradanov ["Automatic Parallelization
and OpenMP Offloadingof Fortran Array
Notation"](https://www.osti.gov/servlets/purl/[2449728](https://www.osti.gov/servlets/purl/2449728))
