[ReplicaGroupV3][JAX+stablehlo][6/n] Emit RGV3 from JAX in shard_map

shardy/dialect/sdy/transforms/import/lift_inlined_meshes.cc

@@ -114,6 +114,7 @@ struct LiftInlinedMeshesPass
     : public impl::LiftInlinedMeshesPassBase<LiftInlinedMeshesPass> {
   using LiftInlinedMeshesPassBase::LiftInlinedMeshesPassBase;
 
+ protected:
   void runOnOperation() final {
     ModuleOp moduleOp = getOperation();
     SymbolTable symbolTable(moduleOp);
@@ -196,6 +197,36 @@ struct LiftInlinedMeshesPass
     moduleOp.walk([&](stablehlo::CollectiveBroadcastOp op) {
       processMeshInReplicaGroups(op);
     });
+
+    // Attach discardable `stablehlo.mesh` attributes to all named meshes.
+    // Downgrading to older StableHLO versions before
+    // `MeshAxesReplicaGroups` was added requires the
+    // `StablehloCompatibilityExpander` pass to resolve symbol references to
+    // named meshes and extract a `stablehlo::MeshAttr` from them. Because
+    // Shardy's `sdy::MeshOp` stores its configuration as an `sdy::MeshAttr`
+    // and core StableHLO cannot depend on Shardy, attaching this discardable
+    // attribute ensures compatibility without violating dialect layering.
+    for (auto meshOp : llvm::make_early_inc_range(moduleOp.getOps<MeshOp>())) {
+      if (meshOp->hasAttr("stablehlo.mesh")) {
+        continue;
+      }
+      MeshAttr sdyMeshAttr = meshOp.getMesh();
+      SmallVector<mlir::stablehlo::MeshAxisAttr> shloAxes;
+      for (auto axisAttr : sdyMeshAttr.getAxes()) {
+        shloAxes.push_back(mlir::stablehlo::MeshAxisAttr::get(
+            meshOp.getContext(), axisAttr.getName(), axisAttr.getSize()));
+      }
+      DenseIntElementsAttr deviceIds;
+      if (!sdyMeshAttr.getDeviceIds().empty()) {
+        auto type = RankedTensorType::get(
+            {static_cast<int64_t>(sdyMeshAttr.getDeviceIds().size())},
+            builder.getI64Type());
+        deviceIds = DenseIntElementsAttr::get(type, sdyMeshAttr.getDeviceIds());
+      }
+      auto shloMeshAttr = mlir::stablehlo::MeshAttr::get(meshOp.getContext(),
+                                                         shloAxes, deviceIds);
+      meshOp->setAttr("stablehlo.mesh", shloMeshAttr);
+    }
   }
 };
 

shardy/dialect/sdy/transforms/import/test/lift_inlined_meshes.mlir

@@ -256,3 +256,18 @@ func.func private @foo(%arg0: tensor<8x8xf32> {sdy.sharding = #sdy.sharding<@mes
   %0 = stablehlo.negate %arg0 {sdy.sharding = #sdy.sharding_per_value<[<@mesh, [{"x"}, {}]>]>} : tensor<8x8xf32>
   return %0 : tensor<8x8xf32>
 }
+
+// -----
+
+// CHECK: sdy.mesh @mesh = <["a"=4]> {stablehlo.mesh = #stablehlo.mesh<axes=[<name = "a", size = 4>]>}
+sdy.mesh @mesh = <["a"=4]>
+
+// CHECK: sdy.mesh @mesh_0 = <["b"=2]> {stablehlo.mesh = #stablehlo.mesh<axes=[<name = "b", size = 2>]>}
+
+// CHECK-LABEL: func @tagged_stablehlo_mesh_attribute
+func.func @tagged_stablehlo_mesh_attribute(%arg0: tensor<4x4xf32> {sdy.sharding = #sdy.sharding<@mesh, [{"a"}, {}]>}, %arg1: tensor<4x4xf32>) -> tensor<4x4xf32> {
+  // CHECK-NEXT: stablehlo.add %arg0, %arg1 {sdy.sharding = #sdy.sharding_per_value<[<@mesh_0, [{"b"}, {}]>]>}
+  %0 = stablehlo.add %arg0, %arg1 {sdy.sharding = #sdy.sharding_per_value<[<mesh<["b"=2]>, [{"b"}, {}]>]>} : tensor<4x4xf32>
+  return %0 : tensor<4x4xf32>
+}
+

shardy/dialect/sdy/transforms/propagation/test/propagation_pipeline.mlir

@@ -1,4 +1,4 @@
-// RUN: sdy_opt %s -split-input-file -sdy-propagation-pipeline 2>&1 | FileCheck %s
+// RUN: sdy_opt %s -split-input-file -sdy-propagation-pipeline | FileCheck %s
 
 sdy.mesh @mesh = <["a"=2, "b"=2, "c"=2]>