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

[Sergio Afonso]

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@@ -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>()));
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skatrak wrote:

So, is the problem that nested `scan` are not supported? If so, rather than checking for an `omp.wsloop` parent the right check would be to go through all parents and make sure none of them have a `reduction_mod` attribute or, if they do, it doesn't have the `inscan` modifier.

Otherwise, we'd be disallowing cases like what I shared previously in this thread, which only has a single `scan`.

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