| /* Copyright 2018 The TensorFlow Authors. All Rights Reserved. |
| |
| Licensed under the Apache License, Version 2.0 (the "License"); |
| you may not use this file except in compliance with the License. |
| You may obtain a copy of the License at |
| |
| http://www.apache.org/licenses/LICENSE-2.0 |
| |
| Unless required by applicable law or agreed to in writing, software |
| distributed under the License is distributed on an "AS IS" BASIS, |
| WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| See the License for the specific language governing permissions and |
| limitations under the License. |
| ==============================================================================*/ |
| |
| #ifndef TENSORFLOW_COMPILER_XLA_SERVICE_WHILE_LOOP_INVARIANT_CODE_MOTION_H_ |
| #define TENSORFLOW_COMPILER_XLA_SERVICE_WHILE_LOOP_INVARIANT_CODE_MOTION_H_ |
| |
| #include "tensorflow/compiler/xla/service/hlo_module.h" |
| #include "tensorflow/compiler/xla/service/hlo_pass_interface.h" |
| #include "tensorflow/compiler/xla/statusor.h" |
| |
| namespace xla { |
| |
| // HLO pass that rewrites while loops to hoist loop invariant instructions in |
| // the while body into the computation that contains the while instruction. |
| |
| class WhileLoopInvariantCodeMotion : public HloModulePass { |
| public: |
| // If `hoist_constants` is true then constants are always hoisted out of while |
| // loop bodies. Otherwise they are only hoisted out if they enable other |
| // non-trivial computations to be hoisted out. |
| // |
| // Setting `hoist_constants` to false can be help if LICM is run in the mid |
| // level HLO pipeline because hoisting constants out of while loop bodies can |
| // break optimizations like constant folding. |
| explicit WhileLoopInvariantCodeMotion(bool hoist_constants = false) |
| : hoist_constants_(hoist_constants) {} |
| ~WhileLoopInvariantCodeMotion() override = default; |
| |
| absl::string_view name() const override { |
| return "while-loop-invariant-code-motion"; |
| } |
| StatusOr<bool> Run(HloModule* module) override; |
| |
| private: |
| bool NotWorthHoistingIndividually(const HloInstruction& instruction); |
| StatusOr<bool> TryHoistingInvariantInstructionsFromWhileBody( |
| HloInstruction* while_instr); |
| |
| bool hoist_constants_; |
| }; |
| } // namespace xla |
| |
| #endif // TENSORFLOW_COMPILER_XLA_SERVICE_WHILE_LOOP_INVARIANT_CODE_MOTION_H_ |