57 lines
1.8 KiB
C++
57 lines
1.8 KiB
C++
// Copyright (c) 2017 Google Inc.
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//
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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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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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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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#ifndef SOURCE_OPT_DEAD_VARIABLE_ELIMINATION_H_
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#define SOURCE_OPT_DEAD_VARIABLE_ELIMINATION_H_
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#include <climits>
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#include <unordered_map>
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#include "source/opt/decoration_manager.h"
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#include "source/opt/mem_pass.h"
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namespace spvtools {
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namespace opt {
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class DeadVariableElimination : public MemPass {
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public:
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const char* name() const override { return "eliminate-dead-variables"; }
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Status Process() override;
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IRContext::Analysis GetPreservedAnalyses() override {
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return IRContext::kAnalysisDefUse | IRContext::kAnalysisConstants |
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IRContext::kAnalysisTypes;
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}
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private:
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// Deletes the OpVariable instruction who result id is |result_id|.
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void DeleteVariable(uint32_t result_id);
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// Keeps track of the number of references of an id. Once that value is 0, it
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// is safe to remove the corresponding instruction.
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//
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// Note that the special value kMustKeep is used to indicate that the
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// instruction cannot be deleted for reasons other that is being explicitly
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// referenced.
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std::unordered_map<uint32_t, size_t> reference_count_;
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// Special value used to indicate that an id cannot be safely deleted.
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enum { kMustKeep = INT_MAX };
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};
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} // namespace opt
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} // namespace spvtools
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#endif // SOURCE_OPT_DEAD_VARIABLE_ELIMINATION_H_
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