[Mlir-commits] [flang] [mlir] [openmp] [MLIR][OpenMP] Add scan reduction lowering to llvm (PR #167031)

[Anchu Rajendran S]

================
@@ -2320,12 +2326,52 @@ genParallelOp(lower::AbstractConverter &converter, lower::SymMap &symTable,
 
 static mlir::omp::ScanOp
 genScanOp(lower::AbstractConverter &converter, lower::SymMap &symTable,
-          semantics::SemanticsContext &semaCtx, mlir::Location loc,
-          const ConstructQueue &queue, ConstructQueue::const_iterator item) {
+          semantics::SemanticsContext &semaCtx, lower::pft::Evaluation &eval,
+          mlir::Location loc, const ConstructQueue &queue,
+          ConstructQueue::const_iterator item) {
   mlir::omp::ScanOperands clauseOps;
   genScanClauses(converter, semaCtx, item->clauses, loc, clauseOps);
-  return mlir::omp::ScanOp::create(converter.getFirOpBuilder(),
-                                   converter.getCurrentLocation(), clauseOps);
+  mlir::omp::ScanOp scanOp = mlir::omp::ScanOp::create(
+      converter.getFirOpBuilder(), converter.getCurrentLocation(), clauseOps);
+
+  /// Scan redution is not implemented with nested workshare loops, linear
+  /// clause, tiling
+  mlir::omp::LoopNestOp loopNestOp =
+      scanOp->getParentOfType<mlir::omp::LoopNestOp>();
+  mlir::omp::WsloopOp wsLoopOp = scanOp->getParentOfType<mlir::omp::WsloopOp>();
+  bool isNested =
+      (loopNestOp.getNumLoops() > 1) ||
+      (wsLoopOp && (wsLoopOp->getParentOfType<mlir::omp::WsloopOp>()));
----------------
anchuraj wrote:

The outer workshare loop can also have scan directive specified. [The example specified](https://github.com/llvm/llvm-project/pull/167031/files#diff-d9d828a444234a47c2a1a1596cc8653925b4f9e7e0c51ad6117b2270ebe78f11) does not compute right results. Thats why I have mentioned it as a TODO. Possibly something is going wrong with the temporary buffer allocation. Need to dig deeper into it 

https://github.com/llvm/llvm-project/pull/167031