1 | /* Copyright 2022 The TensorFlow Authors. All Rights Reserved. |
2 | |
3 | Licensed under the Apache License, Version 2.0 (the "License"); |
4 | you may not use this file except in compliance with the License. |
5 | You may obtain a copy of the License at |
6 | |
7 | http://www.apache.org/licenses/LICENSE-2.0 |
8 | |
9 | Unless required by applicable law or agreed to in writing, software |
10 | distributed under the License is distributed on an "AS IS" BASIS, |
11 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
12 | See the License for the specific language governing permissions and |
13 | limitations under the License. |
14 | ==============================================================================*/ |
15 | |
16 | #include "mlir/Dialect/Func/IR/FuncOps.h" // from @llvm-project |
17 | #include "mlir/IR/Builders.h" // from @llvm-project |
18 | #include "mlir/IR/Operation.h" // from @llvm-project |
19 | #include "mlir/Transforms/FoldUtils.h" // from @llvm-project |
20 | #include "mlir/Transforms/Passes.h" // from @llvm-project |
21 | #include "tensorflow/compiler/mlir/tensorflow/ir/tf_ops.h" |
22 | #include "tensorflow/dtensor/mlir/dtensor_mlir_passes.h" |
23 | |
24 | namespace tensorflow { |
25 | namespace dtensor { |
26 | |
27 | namespace { |
28 | #define GEN_PASS_DEF_DTENSORCONSTANTFOLDING |
29 | #include "tensorflow/dtensor/mlir/dtensor_passes.h.inc" |
30 | |
31 | constexpr int kMaxIteration = 10; |
32 | |
33 | mlir::LogicalResult FoldConstantOp(mlir::OperationFolder& folder, |
34 | mlir::TF::ConstOp op) { |
35 | bool changed = false; |
36 | int i = 0; |
37 | // Iterate until convergence or until maxIterations. Deletion of the op as |
38 | // a result of being dead or folded is convergence. |
39 | do { |
40 | changed = false; |
41 | |
42 | // If the operation is trivially dead - remove it. |
43 | if (isOpTriviallyDead(op)) { |
44 | op->erase(); |
45 | return mlir::success(); |
46 | } |
47 | |
48 | // Try to fold this op. |
49 | bool inPlaceUpdate; |
50 | if (succeeded(folder.tryToFold(op, |
51 | /*processGeneratedConstants=*/nullptr, |
52 | /*preReplaceAction=*/nullptr, |
53 | &inPlaceUpdate))) { |
54 | changed = true; |
55 | if (!inPlaceUpdate) { |
56 | return mlir::success(); |
57 | } |
58 | } |
59 | } while (changed && ++i < kMaxIteration); |
60 | return mlir::success(); |
61 | } |
62 | |
63 | // MLIR pass that folds constants that can be removed or deduplicated away. |
64 | struct DTensorConstantFolding |
65 | : public impl::DTensorConstantFoldingBase<DTensorConstantFolding> { |
66 | void runOnOperation() override { |
67 | mlir::MLIRContext& context = getContext(); |
68 | mlir::OperationFolder helper(&context); |
69 | |
70 | // Collect and fold the operations within the function. |
71 | llvm::SmallVector<mlir::TF::ConstOp, 8> const_ops; |
72 | getOperation().walk([&](mlir::TF::ConstOp op) { const_ops.push_back(op); }); |
73 | |
74 | // Attempt to fold the specified operation, including handling unused or |
75 | // duplicated constants. |
76 | for (mlir::TF::ConstOp op : llvm::reverse(const_ops)) |
77 | if (mlir::failed(FoldConstantOp(helper, op))) return signalPassFailure(); |
78 | } |
79 | }; |
80 | |
81 | } // namespace |
82 | |
83 | std::unique_ptr<mlir::OperationPass<mlir::func::FuncOp>> |
84 | CreateDTensorConstantFolding() { |
85 | return std::make_unique<DTensorConstantFolding>(); |
86 | } |
87 | |
88 | } // namespace dtensor |
89 | } // namespace tensorflow |
90 | |