mirror of
https://github.com/ethereum/solidity
synced 2023-10-03 13:03:40 +00:00
92 lines
3.3 KiB
C++
92 lines
3.3 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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/**
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* Replace every u256 variable with four u64 variables.
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*/
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#pragma once
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#include <libyul/optimiser/ASTWalker.h>
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#include <libyul/optimiser/NameDispenser.h>
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#include <array>
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#include <vector>
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namespace yul
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{
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/**
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* A stage that replace every u256 variable with four u64 variables.
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* This transformation stage is required because values in EVM are 256 bits,
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* but wasm only supports values up to 64 bits, so we use four u64 values to simulate
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* one u256 value.
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*
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* For FunctionalInstruction that accepts or returns u256 values, they accepts or returns
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* four times the number of values after this transformation, with the order of significance,
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* from the most significant to the least significant.
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*
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* For example, the FunctionalInstruction MUL supplied by code generator
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* should take 8 arguments and return 4 values (instead of 2 and 1) after this transformation.
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*
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* mul(a1, a2, a3, a4, b1, b2, b3, b4) -> c1, c2, c3, c4
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*
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* the value of c4 should be
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* ((a1*(2^192) + a2*(2^128) + a3(2^64) + a4) * (b1*(2^192) + b2*(2^128) + b3(2^64) + b4)) & ((1<<64)-1)
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*
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* The resulting code still uses the EVM builtin functions but assumes that they
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* take four times the parameters and each of type u64.
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* In addition, it uses a single other builtin function called `or_bool` that
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* takes four u64 parameters and is supposed to return the logical disjunction
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* of them as a u64 value. If this name is already used somewhere, it is renamed.
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*
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* Prerequisite: Disambiguator, ExpressionSplitter
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*/
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class WordSizeTransform: public ASTModifier
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{
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public:
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void operator()(FunctionDefinition&) override;
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void operator()(FunctionalInstruction&) override;
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void operator()(FunctionCall&) override;
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void operator()(If&) override;
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void operator()(Switch&) override;
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void operator()(ForLoop&) override;
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void operator()(Block& _block) override;
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static void run(Dialect const& _inputDialect, Block& _ast, NameDispenser& _nameDispenser);
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private:
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explicit WordSizeTransform(Dialect const& _inputDialect, NameDispenser& _nameDispenser):
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m_inputDialect(_inputDialect),
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m_nameDispenser(_nameDispenser)
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{ }
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void rewriteVarDeclList(std::vector<TypedName>&);
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void rewriteIdentifierList(std::vector<Identifier>&);
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void rewriteFunctionCallArguments(std::vector<Expression>&);
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std::array<YulString, 4> generateU64IdentifierNames(YulString const& _s);
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std::array<std::unique_ptr<Expression>, 4> expandValue(Expression const& _e);
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std::vector<Expression> expandValueToVector(Expression const& _e);
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Dialect const& m_inputDialect;
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NameDispenser& m_nameDispenser;
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/// maps original u256 variable's name to corresponding u64 variables' names
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std::map<YulString, std::array<YulString, 4>> m_variableMapping;
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};
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}
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