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// Copyright (c) 2018 Google Inc.
//
// 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_REDUCE_OPERAND_TO_DOMINATING_ID_REDUCTION_OPPORTUNITY_FINDER_H_
#define SOURCE_REDUCE_OPERAND_TO_DOMINATING_ID_REDUCTION_OPPORTUNITY_FINDER_H_
#include "source/reduce/reduction_opportunity_finder.h"
namespace spvtools {
namespace reduce {
// A finder that aims to bring to SPIR-V (and generalize) the idea from
// human-readable languages of e.g. finding opportunities to replace an
// expression with one of its arguments, (x + y) -> x, or with a reference to an
// identifier that was assigned to higher up in the program. The generalization
// of this is to replace an id with a different id of the same type defined in
// some dominating instruction.
//
// If id x is defined and then used several times, changing each use of x to
// some dominating definition may eventually allow the statement defining x
// to be eliminated by another pass.
class OperandToDominatingIdReductionOpportunityFinder
: public ReductionOpportunityFinder {
public:
OperandToDominatingIdReductionOpportunityFinder() = default;
~OperandToDominatingIdReductionOpportunityFinder() override = default;
std::string GetName() const final;
std::vector<std::unique_ptr<ReductionOpportunity>> GetAvailableOpportunities(
opt::IRContext* context, uint32_t target_function) const final;
private:
void GetOpportunitiesForDominatingInst(
std::vector<std::unique_ptr<ReductionOpportunity>>* opportunities,
opt::Instruction* dominating_instruction,
opt::Function::iterator candidate_dominator_block,
opt::Function* function, opt::IRContext* context) const;
};
} // namespace reduce
} // namespace spvtools
#endif // SOURCE_REDUCE_OPERAND_TO_DOMINATING_ID_REDUCTION_OPPORTUNITY_FINDER_H_