[flang-commits] [flang] [mlir] [mlir][OpenMP] - Transform target offloading directives for easier translation to LLVMIR (PR #83966)

[Kareem Ergawy via flang-commits]

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@@ -0,0 +1,120 @@
+//===- OpenMPTaskBasedTarget.cpp - Implementation of OpenMPTaskBasedTargetPass
+//---===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements a pass that transforms certain omp.target.
+// Specifically, an omp.target op that has the depend clause on it is
+// transformed into an omp.task clause with the same depend clause on it.
+// The original omp.target loses its depend clause and is contained in
+// the new task region.
+//
+// omp.target depend(..) {
+//  omp.terminator
+//
+// }
+//
+// =>
+//
+// omp.task depend(..) {
+//   omp.target {
+//     omp.terminator
+//   }
+//   omp.terminator
+// }
+//
+//
+//===----------------------------------------------------------------------===//
+
+#include "mlir/Dialect/OpenMP/Passes.h"
+
+#include "mlir/Dialect/Func/IR/FuncOps.h"
+#include "mlir/Dialect/OpenMP/OpenMPDialect.h"
+#include "mlir/Transforms/GreedyPatternRewriteDriver.h"
+#include "llvm/Support/Debug.h"
+
+namespace mlir {
+#define GEN_PASS_DEF_OPENMPTASKBASEDTARGET
+#include "mlir/Dialect/OpenMP/Passes.h.inc"
+} // namespace mlir
+
+using namespace mlir;
+using namespace mlir::omp;
+
+#define DEBUG_TYPE "openmp-task-based-target"
+
+namespace {
+
+struct OpenMPTaskBasedTargetPass
+    : public impl::OpenMPTaskBasedTargetBase<OpenMPTaskBasedTargetPass> {
+
+  void runOnOperation() override;
+};
+template <typename OpTy>
+class OmpTaskBasedTargetRewritePattern : public OpRewritePattern<OpTy> {
+public:
+  using OpRewritePattern<OpTy>::OpRewritePattern;
+  LogicalResult matchAndRewrite(OpTy op,
+                                PatternRewriter &rewriter) const override {
+
+    // Only match a target op with a  'depend' clause on it.
+    if (op.getDependVars().empty()) {
+      return rewriter.notifyMatchFailure(op, "depend clause not found on op");
----------------
ergawy wrote:

Why not use a `ConversionTarget` and setup it with legality information instead? https://github.com/llvm/llvm-project/blob/main/mlir/docs/DialectConversion.md#conversion-target

https://github.com/llvm/llvm-project/pull/83966