1/* Copyright 2022 The TensorFlow Authors. All Rights Reserved.
2
3Licensed under the Apache License, Version 2.0 (the "License");
4you may not use this file except in compliance with the License.
5You may obtain a copy of the License at
6
7 http://www.apache.org/licenses/LICENSE-2.0
8
9Unless required by applicable law or agreed to in writing, software
10distributed under the License is distributed on an "AS IS" BASIS,
11WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12See the License for the specific language governing permissions and
13limitations under the License.
14==============================================================================*/
15
16#include <algorithm>
17#include <memory>
18
19#include "mlir/Dialect/Func/IR/FuncOps.h" // from @llvm-project
20#include "mlir/IR/Builders.h" // from @llvm-project
21#include "mlir/IR/Operation.h" // from @llvm-project
22#include "mlir/Pass/Pass.h" // from @llvm-project
23#include "tensorflow/dtensor/cc/tensor_layout.h"
24#include "tensorflow/dtensor/mlir/ir/tf_dtensor.h"
25
26namespace tensorflow {
27namespace dtensor {
28
29namespace {
30#define GEN_PASS_DEF_DTENSORUNDOMERGECONSTACROSSMESH
31#include "tensorflow/dtensor/mlir/dtensor_passes.h.inc"
32
33// MLIR pass that undoes unintended const merging across different meshes within
34// the same Block by canonicalization passes.
35struct DTensorUndoMergeConstAcrossMesh
36 : public impl::DTensorUndoMergeConstAcrossMeshBase<
37 DTensorUndoMergeConstAcrossMesh> {
38 void runOnOperation() override {
39 mlir::MLIRContext& context = getContext();
40 mlir::OpBuilder builder(&context);
41 getOperation().walk([&builder](mlir::TF::ConstOp const_op) {
42 llvm::SmallVector<Mesh> known_meshes;
43 llvm::SmallVector<mlir::TF::DTensorLayout> unique_layout_ops;
44 for (mlir::Operation* consumer : const_op->getUsers()) {
45 mlir::TF::DTensorLayout layout_op =
46 mlir::dyn_cast<mlir::TF::DTensorLayout>(consumer);
47 if (!layout_op) continue;
48
49 const Layout layout = layout_op.layout(); // keep-alive for mesh.
50 const Mesh& mesh = layout.mesh();
51 if (std::find(known_meshes.begin(), known_meshes.end(), mesh) ==
52 known_meshes.end()) {
53 if (!known_meshes.empty()) {
54 // We skip the first layout_op to preserve its original ConstOp.
55 unique_layout_ops.push_back(layout_op);
56 }
57 known_meshes.emplace_back(mesh);
58 }
59 }
60 for (auto& layout_op : unique_layout_ops) {
61 builder.setInsertionPoint(layout_op);
62 layout_op->replaceUsesOfWith(const_op,
63 builder.cloneWithoutRegions(const_op));
64 }
65 });
66 }
67};
68
69} // namespace
70
71std::unique_ptr<mlir::OperationPass<mlir::func::FuncOp>>
72CreateDTensorUndoMergeConstAcrossMesh() {
73 return std::make_unique<DTensorUndoMergeConstAcrossMesh>();
74}
75} // namespace dtensor
76} // namespace tensorflow
77