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// Copyright (c) 2017 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_OPT_DEAD_VARIABLE_ELIMINATION_H_
#define SOURCE_OPT_DEAD_VARIABLE_ELIMINATION_H_
#include <climits>
#include <unordered_map>
#include "source/opt/decoration_manager.h"
#include "source/opt/mem_pass.h"
namespace spvtools {
namespace opt {
class DeadVariableElimination : public MemPass {
public:
const char* name() const override { return "eliminate-dead-variables"; }
Status Process() override;
IRContext::Analysis GetPreservedAnalyses() override {
return IRContext::kAnalysisDefUse | IRContext::kAnalysisConstants |
IRContext::kAnalysisTypes;
}
private:
// Deletes the OpVariable instruction who result id is |result_id|.
void DeleteVariable(uint32_t result_id);
// Keeps track of the number of references of an id. Once that value is 0, it
// is safe to remove the corresponding instruction.
//
// Note that the special value kMustKeep is used to indicate that the
// instruction cannot be deleted for reasons other that is being explicitly
// referenced.
std::unordered_map<uint32_t, size_t> reference_count_;
// Special value used to indicate that an id cannot be safely deleted.
enum { kMustKeep = INT_MAX };
};
} // namespace opt
} // namespace spvtools
#endif // SOURCE_OPT_DEAD_VARIABLE_ELIMINATION_H_
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