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// Copyright (c) 2018 Google LLC.
//
// 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 SOURCE_OPT_LOOP_FISSION_H_
#define SOURCE_OPT_LOOP_FISSION_H_
#include <algorithm>
#include <cstdint>
#include <map>
#include <utility>
#include <vector>
#include "source/opt/cfg.h"
#include "source/opt/loop_dependence.h"
#include "source/opt/loop_utils.h"
#include "source/opt/module.h"
#include "source/opt/pass.h"
#include "source/opt/tree_iterator.h"
namespace spvtools {
namespace opt {
class LoopFissionPass : public Pass {
public:
// Function used to determine if a given loop should be split. Takes register
// pressure region for that loop as a parameter and returns true if the loop
// should be split.
using FissionCriteriaFunction =
std::function<bool(const RegisterLiveness::RegionRegisterLiveness&)>;
// Pass built with this constructor will split all loops regardless of
// register pressure. Will not split loops more than once.
LoopFissionPass();
// Split the loop if the number of registers used in the loop exceeds
// |register_threshold_to_split|. |split_multiple_times| flag determines
// whether or not the pass should split loops after already splitting them
// once.
LoopFissionPass(size_t register_threshold_to_split,
bool split_multiple_times = true);
// Split loops whose register pressure meets the criteria of |functor|.
LoopFissionPass(FissionCriteriaFunction functor,
bool split_multiple_times = true)
: split_criteria_(functor), split_multiple_times_(split_multiple_times) {}
const char* name() const override { return "loop-fission"; }
Pass::Status Process() override;
// Checks if |loop| meets the register pressure criteria to be split.
bool ShouldSplitLoop(const Loop& loop, IRContext* context);
private:
// Functor to run in ShouldSplitLoop to determine if the register pressure
// criteria is met for splitting the loop.
FissionCriteriaFunction split_criteria_;
// Flag designating whether or not we should also split the result of
// previously split loops if they meet the register presure criteria.
bool split_multiple_times_;
};
} // namespace opt
} // namespace spvtools
#endif // SOURCE_OPT_LOOP_FISSION_H_
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