b02479494a
HloLivenessAnalysis marks all live instruction outputs (i.e. tuple elements) for all instructions in an HloModule, propagating live values across computation boundaries. HloModuleDCE sweeps through each instructions dead tuple elements, eliminating dead code (currently removes dead tuple elements from while loops, but could be extended to do the same for call instructions). PiperOrigin-RevId: 197003043
67 lines
2.4 KiB
C++
67 lines
2.4 KiB
C++
/* Copyright 2018 The TensorFlow Authors. All Rights Reserved.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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==============================================================================*/
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#ifndef TENSORFLOW_COMPILER_XLA_SERVICE_HLO_LIVENESS_ANALYSIS_H_
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#define TENSORFLOW_COMPILER_XLA_SERVICE_HLO_LIVENESS_ANALYSIS_H_
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#include <unordered_map>
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#include "tensorflow/compiler/xla/service/call_graph.h"
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#include "tensorflow/compiler/xla/service/hlo_instruction.h"
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#include "tensorflow/compiler/xla/service/hlo_module.h"
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#include "tensorflow/compiler/xla/service/hlo_value.h"
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#include "tensorflow/compiler/xla/shape_tree.h"
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#include "tensorflow/compiler/xla/shape_util.h"
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#include "tensorflow/compiler/xla/status.h"
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#include "tensorflow/compiler/xla/statusor.h"
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namespace xla {
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// Analysis which identifies all live {HloInstruction, ShapeIndex} pairs in
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// an HLO module.
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//
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// HloLivenessAnalysis marks the shape index of each live output of each
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// instruction in the module, by propagating live shape index information
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// from an instruction to its called computations and operands.
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class HloLivenessAnalysis {
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public:
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// Maps from an HloInstruction to its live/dead output shape indices.
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using HloIndexMap =
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std::unordered_map<const HloInstruction*, ShapeTree<bool>>;
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// Runs liveness analysis on 'module'. Returns HloLivenessAnalysis object
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// which exports liveness for each {HloInstruction, ShapeIndex} in 'module'.
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static StatusOr<std::unique_ptr<HloLivenessAnalysis>> Run(
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const HloModule& module);
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// Returns true if output of 'instruction' at 'shape_index' is live.
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// Returns false otherwise.
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bool IsLive(const HloInstruction* instruction,
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const ShapeIndex& shape_index) const;
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private:
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HloLivenessAnalysis(const HloModule& module);
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void RunAnalysis();
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const HloModule& module_;
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std::unique_ptr<CallGraph> call_graph_;
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HloIndexMap live_index_map_;
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};
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} // namespace xla
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#endif // TENSORFLOW_COMPILER_XLA_SERVICE_HLO_LIVENESS_ANALYSIS_H_
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