1 /* Copyright 2020 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 #ifndef TENSORFLOW_COMPILER_XLA_SERVICE_ROOT_INSTRUCTION_SINKER_H_ 17 #define TENSORFLOW_COMPILER_XLA_SERVICE_ROOT_INSTRUCTION_SINKER_H_ 18 19 #include "tensorflow/compiler/xla/service/hlo_module.h" 20 #include "tensorflow/compiler/xla/service/hlo_pass_interface.h" 21 22 namespace xla { 23 24 // Given a scheduled HLO module, this pass sinks the ROOT of the instruction to 25 // the bottom of the non-fusion computations. To avoid dependency violations of 26 // moving the ROOT instruction, it creates a new ROOT instruction that looks 27 // like the following: 28 // - For tuple ROOT type: 29 // new_root = tuple(gte(old_root), gte(old_root), ...) 30 // - For non-tuple ROOT type: 31 // new_root = bitcast(old_root) 32 class RootInstructionSinker : public HloModulePass { 33 public: 34 ~RootInstructionSinker() override = default; name()35 absl::string_view name() const override { return "root-instruction-sinker"; } 36 StatusOr<bool> Run(HloModule* module) override; 37 }; 38 39 } // namespace xla 40 41 #endif // TENSORFLOW_COMPILER_XLA_SERVICE_ROOT_INSTRUCTION_SINKER_H_ 42