[flang-commits] [flang] [flang][OpenMP] Add TODOs for target [teams|parallel] private (PR #143706)

[Kareem Ergawy via flang-commits]

ergawy wrote:

Not the best solution but there is a precedent for using a global to handle cross-construct communication:

```diff
diff --git a/flang/lib/Lower/OpenMP/OpenMP.cpp b/flang/lib/Lower/OpenMP/OpenMP.cpp
index c13fa471978d..d14464f0e854 100644
--- a/flang/lib/Lower/OpenMP/OpenMP.cpp
+++ b/flang/lib/Lower/OpenMP/OpenMP.cpp
@@ -201,6 +201,8 @@ private:
 /// structures, but it will probably still require some further work to support
 /// reverse offloading.
 static llvm::SmallVector<HostEvalInfo, 0> hostEvalInfo;
+static llvm::SmallVector<const parser::OpenMPSectionsConstruct *, 0>
+    sectionsStack;
 
 /// Bind symbols to their corresponding entry block arguments.
 ///
@@ -2220,8 +2222,12 @@ static mlir::omp::SectionsOp
 genSectionsOp(lower::AbstractConverter &converter, lower::SymMap &symTable,
               semantics::SemanticsContext &semaCtx,
               lower::pft::Evaluation &eval, mlir::Location loc,
-              const ConstructQueue &queue, ConstructQueue::const_iterator item,
-              const parser::OmpSectionBlocks &sectionBlocks) {
+              const ConstructQueue &queue,
+              ConstructQueue::const_iterator item) {
+  assert(!sectionsStack.empty());
+  const auto &sectionBlocks =
+      std::get<parser::OmpSectionBlocks>(sectionsStack.back()->t);
+  sectionsStack.pop_back();
   mlir::omp::SectionsOperands clauseOps;
   llvm::SmallVector<const semantics::Symbol *> reductionSyms;
   genSectionsClauses(converter, semaCtx, item->clauses, loc, clauseOps,
@@ -2668,6 +2674,7 @@ genTeamsOp(lower::AbstractConverter &converter, lower::SymMap &symTable,
            semantics::SemanticsContext &semaCtx, lower::pft::Evaluation &eval,
            mlir::Location loc, const ConstructQueue &queue,
            ConstructQueue::const_iterator item) {
+  lower::SymMapScope scope(symTable);
   mlir::omp::TeamsOperands clauseOps;
   llvm::SmallVector<const semantics::Symbol *> reductionSyms;
   genTeamsClauses(converter, semaCtx, stmtCtx, item->clauses, loc, clauseOps,
@@ -2975,6 +2982,7 @@ static mlir::omp::ParallelOp genStandaloneParallel(
     lower::StatementContext &stmtCtx, semantics::SemanticsContext &semaCtx,
     lower::pft::Evaluation &eval, mlir::Location loc,
     const ConstructQueue &queue, ConstructQueue::const_iterator item) {
+  lower::SymMapScope scope(symTable);
   mlir::omp::ParallelOperands parallelClauseOps;
   llvm::SmallVector<const semantics::Symbol *> parallelReductionSyms;
   genParallelClauses(converter, semaCtx, stmtCtx, item->clauses, loc,
@@ -3462,6 +3470,7 @@ static void genOMPDispatch(lower::AbstractConverter &converter,
     // has a different prototype.
     // This code path is still taken when iterating through the construct queue
     // in genBodyOfOp
+    genSectionsOp(converter, symTable, semaCtx, eval, loc, queue, item);
     break;
   case llvm::omp::Directive::OMPD_simd:
     newOp =
@@ -4143,22 +4152,9 @@ static void genOMP(lower::AbstractConverter &converter, lower::SymMap &symTable,
   ConstructQueue queue{
       buildConstructQueue(converter.getFirOpBuilder().getModule(), semaCtx,
                           eval, source, directive, clauses)};
-  ConstructQueue::iterator next = queue.begin();
-  // Generate constructs that come first e.g. Parallel
-  while (next != queue.end() &&
-         next->id != llvm::omp::Directive::OMPD_sections) {
-    genOMPDispatch(converter, symTable, semaCtx, eval, currentLocation, queue,
-                   next);
-    next = std::next(next);
-  }
-
-  // call genSectionsOp directly (not via genOMPDispatch) so that we can add the
-  // sectionBlocks argument
-  assert(next != queue.end());
-  assert(next->id == llvm::omp::Directive::OMPD_sections);
-  genSectionsOp(converter, symTable, semaCtx, eval, currentLocation, queue,
-                next, sectionBlocks);
-  assert(std::next(next) == queue.end());
+  sectionsStack.push_back(&sectionsConstruct);
+  genOMPDispatch(converter, symTable, semaCtx, eval, currentLocation, queue,
+                 queue.begin());
 }
 
 static void genOMP(lower::AbstractConverter &converter, lower::SymMap &symTable,
```

This passes all lit tests and also handles the `target [parallel|teams] private(...)` cases.

https://github.com/llvm/llvm-project/pull/143706