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Yul: add label id dispenser
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‎libyul/CMakeLists.txt

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@@ -145,6 +145,8 @@ add_library(yul
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optimiser/InlinableExpressionFunctionFinder.h
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optimiser/KnowledgeBase.cpp
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optimiser/KnowledgeBase.h
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optimiser/LabelIDDispenser.cpp
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optimiser/LabelIDDispenser.h
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optimiser/LoadResolver.cpp
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optimiser/LoadResolver.h
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optimiser/LoopInvariantCodeMotion.cpp

‎libyul/optimiser/LabelIDDispenser.cpp

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/*
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This file is part of solidity.
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solidity is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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solidity is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with solidity. If not, see <http://www.gnu.org/licenses/>.
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*/
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// SPDX-License-Identifier: GPL-3.0
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#include <libyul/optimiser/LabelIDDispenser.h>
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#include <libyul/optimiser/NameCollector.h>
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#include <libyul/optimiser/OptimizerUtilities.h>
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#include <fmt/compile.h>
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#include <range/v3/range/conversion.hpp>
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#include <range/v3/view/iota.hpp>
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using namespace solidity::yul;
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namespace
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{
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bool isInvalidLabel(
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std::string_view const _label,
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std::set<std::string, std::less<>> const& _reservedLabels,
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Dialect const& _dialect
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)
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{
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return isRestrictedIdentifier(_dialect, _label) || _reservedLabels.contains(_label);
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}
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}
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LabelIDDispenser::LabelIDDispenser(ASTLabelRegistry const& _labels, std::set<std::string> const& _reservedLabels):
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m_labels(_labels),
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m_reservedLabels(_reservedLabels.begin(), _reservedLabels.end()),
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m_offset(_labels.maxID() + 1)
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{
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m_reservedLabels += std::set{""};
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}
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LabelIDDispenser::LabelID LabelIDDispenser::newID(LabelID const parent)
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{
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m_idToLabelMapping.push_back(resolveParentLabelID(parent));
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return m_idToLabelMapping.size() - 1 + m_offset;
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}
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LabelIDDispenser::LabelID LabelIDDispenser::newGhost()
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{
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m_idToLabelMapping.push_back(ASTLabelRegistry::ghostLabelIndex());
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return m_idToLabelMapping.size() - 1 + m_offset;
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}
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LabelIDDispenser::LabelID LabelIDDispenser::resolveParentLabelID(LabelID _id) const
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{
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yulAssert(_id < m_idToLabelMapping.size() + m_offset, "ID exceeds bounds.");
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// bigger than offset means, that the input label id that was spawned by this dispenser
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if (_id >= m_offset)
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_id = m_idToLabelMapping[_id - m_offset];
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yulAssert(
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_id < m_offset && !m_labels.unused(_id),
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"We can have at most one level of indirection and the derived-from label cannot be unused."
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);
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return _id;
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}
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bool LabelIDDispenser::ghost(LabelID const _id) const
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{
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yulAssert(_id < m_idToLabelMapping.size() + m_offset, "ID exceeds bounds.");
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if (_id >= m_offset)
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return m_idToLabelMapping[_id - m_offset] == ASTLabelRegistry::ghostLabelIndex();
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return m_labels.ghost(_id);
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}
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ASTLabelRegistry LabelIDDispenser::generateNewLabels(Block const&, Dialect const& _dialect) const
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{
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// this can be replaced by the actually used ids in the provided block once the AST uses ids instead of YulString
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std::set<LabelID> usedIDs = ranges::views::iota(static_cast<size_t>(0), m_idToLabelMapping.size() + m_offset) | ranges::to<std::set<LabelID>>;
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if (usedIDs.empty())
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return {};
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auto const& originalLabels = m_labels.labels();
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std::vector<uint8_t> reusedLabels (originalLabels.size());
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// this means that everything that is derived from empty needs to be generated
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reusedLabels[0] = true;
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// start with the empty label
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std::vector<std::string> labels{""};
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labels.reserve(originalLabels.size()+1);
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// usedIDs contains at least one element at this point
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std::vector<size_t> idToLabelMap(*std::prev(usedIDs.end()) + 1, 0);
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std::set<std::string, std::less<>> alreadyDefinedLabels = m_reservedLabels;
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// we record which labels have to be newly generated, some we can just take over from the existing registry
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std::vector<LabelID> toGenerate;
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for (auto const& id: usedIDs)
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{
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if (ghost(id))
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{
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idToLabelMap[id] = ASTLabelRegistry::ghostLabelIndex();
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continue;
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}
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auto const parentLabelID = resolveParentLabelID(id);
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auto const originalLabelIndex = m_labels.idToLabelIndex(parentLabelID);
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auto const& originalLabel = originalLabels[originalLabelIndex];
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// It is important that the used ids are in ascending order to ensure that ids which occur in the provided AST
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// and have unchanged IDs will have their labels reused first, before anything derived from it gets assigned
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// said label.
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static_assert(std::is_same_v<std::decay_t<decltype(usedIDs)>, std::set<LabelID>>);
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// if we haven't already reused the label, check that either the id didn't change, then we can just
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// take over the old label, otherwise check that it is a valid label and then reuse
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if (!reusedLabels[originalLabelIndex] && (parentLabelID == id || !isInvalidLabel(originalLabel, m_reservedLabels, _dialect)))
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{
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labels.push_back(originalLabel);
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idToLabelMap[id] = labels.size() - 1;
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alreadyDefinedLabels.insert(originalLabel);
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reusedLabels[originalLabelIndex] = true;
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}
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else
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toGenerate.push_back(id);
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}
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for (auto const& id: toGenerate)
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{
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if (ghost(id))
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{
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idToLabelMap[id] = ASTLabelRegistry::ghostLabelIndex();
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continue;
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}
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auto const parentLabelID = resolveParentLabelID(id);
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auto const parentLabelIndex = m_labels.idToLabelIndex(parentLabelID);
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auto const& parentLabel = originalLabels[parentLabelIndex];
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std::string generatedLabel = parentLabel;
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size_t suffix = 1;
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do
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{
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generatedLabel = format(FMT_COMPILE("{}_{}"), parentLabel, suffix++);
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} while (isInvalidLabel(generatedLabel, alreadyDefinedLabels, _dialect));
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labels.push_back(generatedLabel);
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idToLabelMap[id] = labels.size() - 1;
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alreadyDefinedLabels.insert(generatedLabel);
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}
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return ASTLabelRegistry{labels, idToLabelMap};
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}

‎libyul/optimiser/LabelIDDispenser.h

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/*
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This file is part of solidity.
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solidity is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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solidity is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with solidity. If not, see <http://www.gnu.org/licenses/>.
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*/
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// SPDX-License-Identifier: GPL-3.0
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#pragma once
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#include <libyul/ASTLabelRegistry.h>
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#include <functional>
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#include <set>
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namespace solidity::yul
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{
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struct Block;
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class Dialect;
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/// Can spawn new `LabelID`s which depend on `LabelID`s from a parent label registry. Once generation is completed,
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/// a new `ASTLabelRegistry` can be generated based on the used subset of spawned and original IDs.
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class LabelIDDispenser
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{
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public:
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using LabelID = ASTLabelRegistry::LabelID;
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/// A set of reserved labels may be provided, which is excluded when generating new labels. If a reserved label
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/// already appears in the label registry and is used as-is in the AST, it will be reused despite it being
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/// provided here.
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explicit LabelIDDispenser(
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ASTLabelRegistry const& _labels,
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std::set<std::string> const& _reserved = {}
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);
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ASTLabelRegistry const& labels() const { return m_labels; }
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LabelID newID(LabelID parent = 0);
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LabelID newGhost();
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/// Creates a new label registry based on the added labels. Will only contain labels for ids referenced in the
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/// provided AST root and preserve ghost IDs, as these are not referenced in the AST.
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ASTLabelRegistry generateNewLabels(Block const& _root, Dialect const& _dialect) const;
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private:
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/// For newly added label ids, this yields the parent ID which is contained in the provided registry.
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/// For label ids which already are not new, this function is the identity.
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LabelID resolveParentLabelID(LabelID _id) const;
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bool ghost(LabelID _id) const;
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ASTLabelRegistry const& m_labels;
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std::set<std::string, std::less<>> m_reservedLabels;
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/// Offset by which LabelIDs must be shifted to be used in the dispenser's `m_idToLabelMapping`
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size_t m_offset;
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/// Contains references to parent label IDs. Indices are new IDs offset by `m_offset`.
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std::vector<LabelID> m_idToLabelMapping;
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};
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}

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