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// Copyright (c) 2021 Alastair F. Donaldson
//
// 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_STRUCTURED_CONSTRUCT_TO_BLOCK_REDUCTION_OPPORTUNITY_FINDER_H
#define SOURCE_REDUCE_STRUCTURED_CONSTRUCT_TO_BLOCK_REDUCTION_OPPORTUNITY_FINDER_H
#include "source/reduce/reduction_opportunity_finder.h"
namespace spvtools {
namespace reduce {
// A finder for opportunities to replace a skeletal structured control flow
// construct - that is, a construct that does not define anything that's used
// outside the construct - into its header block.
class StructuredConstructToBlockReductionOpportunityFinder
: public ReductionOpportunityFinder {
public:
StructuredConstructToBlockReductionOpportunityFinder() = default;
~StructuredConstructToBlockReductionOpportunityFinder() override = default;
std::string GetName() const final;
std::vector<std::unique_ptr<ReductionOpportunity>> GetAvailableOpportunities(
opt::IRContext* context, uint32_t target_function) const final;
private:
// Returns true if and only if all instructions defined in |region| are used
// only inside |region|, with the exception that they may be used by the merge
// or terminator instruction of |header|, which must be the header block for
// the region.
static bool DefinitionsRestrictedToRegion(
const opt::BasicBlock& header,
const std::unordered_set<opt::BasicBlock*>& region,
opt::IRContext* context);
// Returns true if and only if |block| has at least one predecessor that is
// unreachable in the control flow graph of its function.
static bool HasUnreachablePredecessor(const opt::BasicBlock& block,
opt::IRContext* context);
};
} // namespace reduce
} // namespace spvtools
#endif // SOURCE_REDUCE_STRUCTURED_CONSTRUCT_TO_BLOCK_REDUCTION_OPPORTUNITY_FINDER_H
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