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https://github.com/KhronosGroup/SPIRV-Tools
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5d602abd66
Adds a pass that looks for redundant instruction in a function, and removes them. The algorithm is a hash table based value numbering algorithm that traverses the dominator tree. This pass removes completely redundant instructions, not partially redundant ones.
55 lines
2.0 KiB
C++
55 lines
2.0 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 LIBSPIRV_OPT_REDUNDANCY_ELIMINATION_H_
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#define LIBSPIRV_OPT_REDUNDANCY_ELIMINATION_H_
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#include "ir_context.h"
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#include "local_redundancy_elimination.h"
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#include "pass.h"
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#include "value_number_table.h"
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namespace spvtools {
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namespace opt {
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// This pass implements total redundancy elimination. This is the same as
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// local redundancy elimination except it looks across basic block boundaries.
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// An instruction, inst, is totally redundant if there is another instruction
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// that dominates inst, and also computes the same value.
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class RedundancyEliminationPass : public LocalRedundancyEliminationPass {
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public:
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const char* name() const override { return "redundancy-elimination"; }
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Status Process(ir::IRContext*) override;
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protected:
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// Removes for all total redundancies in the function starting at |bb|.
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//
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// |vnTable| must have computed a value number for every result id defined
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// in the function containing |bb|.
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//
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// |value_to_ids| is a map from value number to ids. If {vn, id} is in
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// |value_to_ids| then vn is the value number of id, and the defintion of id
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// dominates |bb|.
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//
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// Returns true if at least one instruction is deleted.
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bool EliminateRedundanciesFrom(DominatorTreeNode* bb,
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const ValueNumberTable& vnTable,
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std::map<uint32_t, uint32_t> value_to_ids);
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};
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} // namespace opt
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} // namespace spvtools
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#endif // LIBSPIRV_OPT_REDUNDANCY_ELIMINATION_H_
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