mirror of
https://github.com/ethereum/solidity
synced 2023-10-03 13:03:40 +00:00
98 lines
4.0 KiB
C++
98 lines
4.0 KiB
C++
/*
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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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/**
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* Stack layout generator for Yul to EVM code generation.
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*/
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#pragma once
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#include <libyul/backends/evm/ControlFlowGraph.h>
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#include <map>
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namespace solidity::yul
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{
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struct StackLayout
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{
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struct BlockInfo
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{
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/// Complete stack layout that is required for entering a block.
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Stack entryLayout;
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/// The resulting stack layout after executing the block.
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Stack exitLayout;
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};
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std::map<CFG::BasicBlock const*, BlockInfo> blockInfos;
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/// For each operation the complete stack layout that:
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/// - has the slots required for the operation at the stack top.
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/// - will have the operation result in a layout that makes it easy to achieve the next desired layout.
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std::map<CFG::Operation const*, Stack> operationEntryLayout;
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};
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class StackLayoutGenerator
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{
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public:
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static StackLayout run(CFG const& _cfg);
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private:
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StackLayoutGenerator(StackLayout& _context);
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/// @returns the optimal entry stack layout, s.t. @a _operation can be applied to it and
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/// the result can be transformed to @a _exitStack with minimal stack shuffling.
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/// Simultaneously stores the entry layout required for executing the operation in m_layout.
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Stack propagateStackThroughOperation(Stack _exitStack, CFG::Operation const& _operation);
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/// @returns the desired stack layout at the entry of @a _block, assuming the layout after
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/// executing the block should be @a _exitStack.
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Stack propagateStackThroughBlock(Stack _exitStack, CFG::BasicBlock const& _block);
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/// Main algorithm walking the graph from entry to exit and propagating back the stack layouts to the entries.
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/// Iteratively reruns itself along backwards jumps until the layout is stabilized.
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void processEntryPoint(CFG::BasicBlock const& _entry);
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/// @returns the best known exit layout of @a _block, if all dependencies are already @a _visited.
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/// If not, adds the dependencies to @a _dependencyList and @returns std::nullopt.
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std::optional<Stack> getExitLayoutOrStageDependencies(
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CFG::BasicBlock const& _block,
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std::set<CFG::BasicBlock const*> const& _visited,
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std::list<CFG::BasicBlock const*>& _dependencyList
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) const;
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/// @returns a pair of ``{jumpingBlock, targetBlock}`` for each backwards jump in the graph starting at @a _entry.
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std::list<std::pair<CFG::BasicBlock const*, CFG::BasicBlock const*>> collectBackwardsJumps(CFG::BasicBlock const& _entry) const;
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/// After the main algorithms, layouts at conditional jumps are merely compatible, i.e. the exit layout of the
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/// jumping block is a superset of the entry layout of the target block. This function modifies the entry layouts
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/// of conditional jump targets, s.t. the entry layout of target blocks match the exit layout of the jumping block
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/// exactly, except that slots not required after the jump are marked as `JunkSlot`s.
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void stitchConditionalJumps(CFG::BasicBlock const& _block);
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/// Calculates the ideal stack layout, s.t. both @a _stack1 and @a _stack2 can be achieved with minimal
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/// stack shuffling when starting from the returned layout.
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static Stack combineStack(Stack const& _stack1, Stack const& _stack2);
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/// @returns a copy of @a _stack stripped of all duplicates and slots that can be freely generated.
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/// Attempts to create a layout that requires a minimal amount of operations to reconstruct the original
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/// stack @a _stack.
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static Stack compressStack(Stack _stack);
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StackLayout& m_layout;
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};
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}
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