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https://github.com/KhronosGroup/SPIRV-Tools
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b35b52f97b
Computing the value numbers on demand, as we do now, can lead to different results depending on the order in which the users asks for the value numbers. To make things more stable, we compute them ahead of time.
90 lines
2.9 KiB
C++
90 lines
2.9 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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#include "local_redundancy_elimination.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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Pass::Status LocalRedundancyEliminationPass::Process(ir::IRContext* c) {
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InitializeProcessing(c);
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bool modified = false;
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ValueNumberTable vnTable(context());
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for (auto& func : *get_module()) {
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for (auto& bb : func) {
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// Keeps track of all ids that contain a given value number. We keep
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// track of multiple values because they could have the same value, but
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// different decorations.
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std::vector<std::vector<uint32_t>> value_to_ids;
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if (EliminateRedundanciesInBB(&bb, &vnTable, &value_to_ids))
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modified = true;
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}
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}
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return (modified ? Status::SuccessWithChange : Status::SuccessWithoutChange);
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}
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bool LocalRedundancyEliminationPass::EliminateRedundanciesInBB(
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ir::BasicBlock* block, ValueNumberTable* vnTable,
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std::vector<std::vector<uint32_t>>* value_to_ids) {
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bool modified = false;
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auto func = [this, vnTable, &modified, value_to_ids](ir::Instruction* inst) {
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if (inst->result_id() == 0) {
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return;
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}
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uint32_t value = vnTable->GetValueNumber(inst);
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if (value == 0) {
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return;
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}
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if (value >= value_to_ids->size()) {
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value_to_ids->resize(value + 1);
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}
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// Now that we have the value number of the instruction, we use
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// |value_to_ids| to get other ids that contain the same value. If we can
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// find an id in that set which has the same decorations, we can replace all
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// uses of the result of |inst| by that id.
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std::vector<uint32_t>& candidate_set = (*value_to_ids)[value];
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bool found_replacement = false;
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for (uint32_t candidate_id : candidate_set) {
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if (get_decoration_mgr()->HaveTheSameDecorations(inst->result_id(),
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candidate_id)) {
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context()->KillNamesAndDecorates(inst);
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context()->ReplaceAllUsesWith(inst->result_id(), candidate_id);
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context()->KillInst(inst);
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modified = true;
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found_replacement = true;
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break;
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}
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}
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// If we did not find a replacement, then add it as a candidate for later
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// instructions.
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if (!found_replacement) {
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candidate_set.push_back(inst->result_id());
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}
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};
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block->ForEachInst(func);
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return modified;
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}
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} // namespace opt
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} // namespace spvtools
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