[Flang][OpenMP][MLIR][Lower] Update lowering to use wrapper ops

This patch introduces the following changes:
  - Complete OpenMP directive sets to include masked and taskloop-related ones.
  - Refactor clause processing to store related operands in structures. These
are combined into construct-specific operand structures using a mixin pattern
and simplify keeping track of operand lists used for creating OpenMP
operations and reduces argument lists.
  - Update the lowering to MLIR of loop constructs to follow the wrapper +
canonical loop approach. This includes some changes to privatization that need
testing.
  - Add lowering for the omp.canonical_loop operation, based on omp.wsloop.
  - Significant refactor of OpenMP construct lowering, separating composite
constructs into their own "gen" functions and handling combined loop constructs
in a more scalable way. Updated genOMP functions to follow the same set of
patterns to make it more understandable. Split clause processing calls from
code generation for operations in preparation for reusing the same code when
dealing with composite constructs.
  - Add basic support for taskloop, for completeness sake.
  - Document missing clauses.
  - Move some code from OpenMP.cpp to ClauseProcessor.cpp and call it there
to simplify calls to certain process methods that were always followed by the
same post-processing.
  - Add and populate "composite" attribute on wrapper operations.
  - Add empty constructors for wrapper operations.
  - Update `LoopWrapperInterface` to avoid compilation problems.
  - Update `Task*` operation's names to follow the same capitalization
convention.
  - Changes to SCF to OpenMP conversion to produce a wrapper omp.wsloop with a
nested omp.canonical_loop rather than an invalid omp.wsloop.
  - Document missing verifier checks on wrapper operations.
  - Make temporary changes to OpenMP to LLVM IR translation to make this
compilable.

All these changes are still WIP, as they haven't been tested.

flang/include/flang/Semantics/openmp-directive-sets.h

@@ -24,68 +24,80 @@ namespace llvm::omp {
 // - all<Directive>Set: All standalone or combined uses of the directive.
 
 static const OmpDirectiveSet topParallelSet{
-    Directive::OMPD_parallel,
-    Directive::OMPD_parallel_do,
     Directive::OMPD_parallel_do_simd,
+    Directive::OMPD_parallel_do,
+    Directive::OMPD_parallel_masked_taskloop_simd,
+    Directive::OMPD_parallel_masked_taskloop,
+    Directive::OMPD_parallel_master_taskloop_simd,
+    Directive::OMPD_parallel_master_taskloop,
     Directive::OMPD_parallel_sections,
     Directive::OMPD_parallel_workshare,
+    Directive::OMPD_parallel,
 };
 
 static const OmpDirectiveSet allParallelSet{
-    Directive::OMPD_distribute_parallel_do,
-    Directive::OMPD_distribute_parallel_do_simd,
-    Directive::OMPD_parallel,
-    Directive::OMPD_parallel_do,
-    Directive::OMPD_parallel_do_simd,
-    Directive::OMPD_parallel_sections,
-    Directive::OMPD_parallel_workshare,
-    Directive::OMPD_target_parallel,
-    Directive::OMPD_target_parallel_do,
-    Directive::OMPD_target_parallel_do_simd,
-    Directive::OMPD_target_teams_distribute_parallel_do,
-    Directive::OMPD_target_teams_distribute_parallel_do_simd,
-    Directive::OMPD_teams_distribute_parallel_do,
-    Directive::OMPD_teams_distribute_parallel_do_simd,
+    OmpDirectiveSet{
+        Directive::OMPD_distribute_parallel_do_simd,
+        Directive::OMPD_distribute_parallel_do,
+        Directive::OMPD_target_parallel_do_simd,
+        Directive::OMPD_target_parallel_do,
+        Directive::OMPD_target_parallel,
+        Directive::OMPD_target_teams_distribute_parallel_do_simd,
+        Directive::OMPD_target_teams_distribute_parallel_do,
+        Directive::OMPD_teams_distribute_parallel_do_simd,
+        Directive::OMPD_teams_distribute_parallel_do,
+    } | topParallelSet,
 };
 
 static const OmpDirectiveSet topDoSet{
-    Directive::OMPD_do,
     Directive::OMPD_do_simd,
+    Directive::OMPD_do,
 };
 
 static const OmpDirectiveSet allDoSet{
-    Directive::OMPD_distribute_parallel_do,
-    Directive::OMPD_distribute_parallel_do_simd,
-    Directive::OMPD_parallel_do,
-    Directive::OMPD_parallel_do_simd,
-    Directive::OMPD_do,
-    Directive::OMPD_do_simd,
-    Directive::OMPD_target_parallel_do,
-    Directive::OMPD_target_parallel_do_simd,
-    Directive::OMPD_target_teams_distribute_parallel_do,
-    Directive::OMPD_target_teams_distribute_parallel_do_simd,
-    Directive::OMPD_teams_distribute_parallel_do,
-    Directive::OMPD_teams_distribute_parallel_do_simd,
+    OmpDirectiveSet{
+        Directive::OMPD_distribute_parallel_do_simd,
+        Directive::OMPD_distribute_parallel_do,
+        Directive::OMPD_parallel_do_simd,
+        Directive::OMPD_parallel_do,
+        Directive::OMPD_target_parallel_do_simd,
+        Directive::OMPD_target_parallel_do,
+        Directive::OMPD_target_teams_distribute_parallel_do_simd,
+        Directive::OMPD_target_teams_distribute_parallel_do,
+        Directive::OMPD_teams_distribute_parallel_do_simd,
+        Directive::OMPD_teams_distribute_parallel_do,
+    } | topDoSet,
 };
 
 static const OmpDirectiveSet topTaskloopSet{
-    Directive::OMPD_taskloop,
     Directive::OMPD_taskloop_simd,
+    Directive::OMPD_taskloop,
 };
 
-static const OmpDirectiveSet allTaskloopSet{topTaskloopSet};
+static const OmpDirectiveSet allTaskloopSet{
+    OmpDirectiveSet{
+        Directive::OMPD_masked_taskloop_simd,
+        Directive::OMPD_masked_taskloop,
+        Directive::OMPD_master_taskloop_simd,
+        Directive::OMPD_master_taskloop,
+        Directive::OMPD_parallel_masked_taskloop_simd,
+        Directive::OMPD_parallel_masked_taskloop,
+        Directive::OMPD_parallel_master_taskloop_simd,
+        Directive::OMPD_parallel_master_taskloop,
+    } | topTaskloopSet,
+};
 
 static const OmpDirectiveSet topTargetSet{
-    Directive::OMPD_target,
-    Directive::OMPD_target_parallel,
-    Directive::OMPD_target_parallel_do,
     Directive::OMPD_target_parallel_do_simd,
+    Directive::OMPD_target_parallel_do,
+    Directive::OMPD_target_parallel,
     Directive::OMPD_target_simd,
-    Directive::OMPD_target_teams,
-    Directive::OMPD_target_teams_distribute,
-    Directive::OMPD_target_teams_distribute_parallel_do,
     Directive::OMPD_target_teams_distribute_parallel_do_simd,
+    Directive::OMPD_target_teams_distribute_parallel_do,
     Directive::OMPD_target_teams_distribute_simd,
+    Directive::OMPD_target_teams_distribute,
+    Directive::OMPD_target_teams,
+    Directive::OMPD_target,
 };
 
 static const OmpDirectiveSet allTargetSet{topTargetSet};
@@ -95,61 +107,61 @@ static const OmpDirectiveSet topSimdSet{
 };
 
 static const OmpDirectiveSet allSimdSet{
-    Directive::OMPD_distribute_parallel_do_simd,
-    Directive::OMPD_distribute_simd,
-    Directive::OMPD_do_simd,
-    Directive::OMPD_parallel_do_simd,
-    Directive::OMPD_simd,
-    Directive::OMPD_target_parallel_do_simd,
-    Directive::OMPD_target_simd,
-    Directive::OMPD_target_teams_distribute_parallel_do_simd,
-    Directive::OMPD_target_teams_distribute_simd,
-    Directive::OMPD_taskloop_simd,
-    Directive::OMPD_teams_distribute_parallel_do_simd,
-    Directive::OMPD_teams_distribute_simd,
+    OmpDirectiveSet{
+        Directive::OMPD_distribute_parallel_do_simd,
+        Directive::OMPD_distribute_simd,
+        Directive::OMPD_do_simd,
+        Directive::OMPD_masked_taskloop_simd,
+        Directive::OMPD_master_taskloop_simd,
+        Directive::OMPD_parallel_do_simd,
+        Directive::OMPD_parallel_masked_taskloop_simd,
+        Directive::OMPD_parallel_master_taskloop_simd,
+        Directive::OMPD_target_parallel_do_simd,
+        Directive::OMPD_target_simd,
+        Directive::OMPD_target_teams_distribute_parallel_do_simd,
+        Directive::OMPD_target_teams_distribute_simd,
+        Directive::OMPD_taskloop_simd,
+        Directive::OMPD_teams_distribute_parallel_do_simd,
+        Directive::OMPD_teams_distribute_simd,
+    } | topSimdSet,
 };
 
 static const OmpDirectiveSet topTeamsSet{
-    Directive::OMPD_teams,
-    Directive::OMPD_teams_distribute,
-    Directive::OMPD_teams_distribute_parallel_do,
     Directive::OMPD_teams_distribute_parallel_do_simd,
+    Directive::OMPD_teams_distribute_parallel_do,
     Directive::OMPD_teams_distribute_simd,
+    Directive::OMPD_teams_distribute,
+    Directive::OMPD_teams,
 };
 
 static const OmpDirectiveSet allTeamsSet{
-    llvm::omp::OMPD_target_teams,
-    llvm::omp::OMPD_target_teams_distribute,
-    llvm::omp::OMPD_target_teams_distribute_parallel_do,
-    llvm::omp::OMPD_target_teams_distribute_parallel_do_simd,
-    llvm::omp::OMPD_target_teams_distribute_simd,
-    llvm::omp::OMPD_teams,
-    llvm::omp::OMPD_teams_distribute,
-    llvm::omp::OMPD_teams_distribute_parallel_do,
-    llvm::omp::OMPD_teams_distribute_parallel_do_simd,
-    llvm::omp::OMPD_teams_distribute_simd,
+    OmpDirectiveSet{
+        llvm::omp::OMPD_target_teams_distribute_parallel_do_simd,
+        llvm::omp::OMPD_target_teams_distribute_parallel_do,
+        llvm::omp::OMPD_target_teams_distribute_simd,
+        llvm::omp::OMPD_target_teams_distribute,
+        llvm::omp::OMPD_target_teams,
+    } | topTeamsSet,
 };
 
 static const OmpDirectiveSet topDistributeSet{
-    Directive::OMPD_distribute,
-    Directive::OMPD_distribute_parallel_do,
     Directive::OMPD_distribute_parallel_do_simd,
+    Directive::OMPD_distribute_parallel_do,
     Directive::OMPD_distribute_simd,
+    Directive::OMPD_distribute,
 };
 
 static const OmpDirectiveSet allDistributeSet{
-    llvm::omp::OMPD_distribute,
-    llvm::omp::OMPD_distribute_parallel_do,
-    llvm::omp::OMPD_distribute_parallel_do_simd,
-    llvm::omp::OMPD_distribute_simd,
-    llvm::omp::OMPD_target_teams_distribute,
-    llvm::omp::OMPD_target_teams_distribute_parallel_do,
-    llvm::omp::OMPD_target_teams_distribute_parallel_do_simd,
-    llvm::omp::OMPD_target_teams_distribute_simd,
-    llvm::omp::OMPD_teams_distribute,
-    llvm::omp::OMPD_teams_distribute_parallel_do,
-    llvm::omp::OMPD_teams_distribute_parallel_do_simd,
-    llvm::omp::OMPD_teams_distribute_simd,
+    OmpDirectiveSet{
+        llvm::omp::OMPD_target_teams_distribute_parallel_do_simd,
+        llvm::omp::OMPD_target_teams_distribute_parallel_do,
+        llvm::omp::OMPD_target_teams_distribute_simd,
+        llvm::omp::OMPD_target_teams_distribute,
+        llvm::omp::OMPD_teams_distribute_parallel_do_simd,
+        llvm::omp::OMPD_teams_distribute_parallel_do,
+        llvm::omp::OMPD_teams_distribute_simd,
+        llvm::omp::OMPD_teams_distribute,
+    } | topDistributeSet,
 };
 
 //===----------------------------------------------------------------------===//
@@ -188,8 +200,16 @@ static const OmpDirectiveSet loopConstructSet{
     Directive::OMPD_distribute,
     Directive::OMPD_do_simd,
     Directive::OMPD_do,
+    Directive::OMPD_masked_taskloop,
+    Directive::OMPD_masked_taskloop_simd,
+    Directive::OMPD_master_taskloop,
+    Directive::OMPD_master_taskloop_simd,
     Directive::OMPD_parallel_do_simd,
     Directive::OMPD_parallel_do,
+    Directive::OMPD_parallel_masked_taskloop,
+    Directive::OMPD_parallel_masked_taskloop_simd,
+    Directive::OMPD_parallel_master_taskloop,
+    Directive::OMPD_parallel_master_taskloop_simd,
     Directive::OMPD_simd,
     Directive::OMPD_target_parallel_do_simd,
     Directive::OMPD_target_parallel_do,