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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.
#include "source/opt/local_redundancy_elimination.h"
#include "source/opt/value_number_table.h"
namespace spvtools {
namespace opt {
Pass::Status LocalRedundancyEliminationPass::Process() {
bool modified = false;
ValueNumberTable vnTable(context());
for (auto& func : *get_module()) {
for (auto& bb : func) {
// Keeps track of all ids that contain a given value number. We keep
// track of multiple values because they could have the same value, but
// different decorations.
std::map<uint32_t, uint32_t> value_to_ids;
if (EliminateRedundanciesInBB(&bb, vnTable, &value_to_ids))
modified = true;
}
}
return (modified ? Status::SuccessWithChange : Status::SuccessWithoutChange);
}
bool LocalRedundancyEliminationPass::EliminateRedundanciesInBB(
BasicBlock* block, const ValueNumberTable& vnTable,
std::map<uint32_t, uint32_t>* value_to_ids) {
bool modified = false;
auto func = [this, &vnTable, &modified, value_to_ids](Instruction* inst) {
if (inst->result_id() == 0) {
return;
}
uint32_t value = vnTable.GetValueNumber(inst);
if (value == 0) {
return;
}
auto candidate = value_to_ids->insert({value, inst->result_id()});
if (!candidate.second) {
context()->KillNamesAndDecorates(inst);
context()->ReplaceAllUsesWith(inst->result_id(), candidate.first->second);
context()->KillInst(inst);
modified = true;
}
};
block->ForEachInst(func);
return modified;
}
} // namespace opt
} // namespace spvtools
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