solidity/libyul/optimiser/BlockHasher.h

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/*
This file is part of solidity.
solidity is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
solidity is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with solidity. If not, see <http://www.gnu.org/licenses/>.
*/
/**
* Optimiser component that calculates hash values for blocks.
*/
#pragma once
#include <libyul/optimiser/ASTWalker.h>
#include <libyul/AsmDataForward.h>
#include <libyul/YulString.h>
#include <libyul/AsmData.h>
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namespace solidity::yul
{
/**
* Optimiser component that calculates hash values for blocks.
* Syntactically equal blocks will have identical hashes and
* blocks with equal hashes will likely be syntactically equal.
*
* The names of internally declared variables are replaced by
* a simple counter, so differing names are not taken into account,
* but only the order of references to declared variables.
*
* Similarly, the names of referenced external variables are not considered,
* but replaced by a (distinct) counter as well.
*
* Prerequisite: Disambiguator, ForLoopInitRewriter
*/
class BlockHasher: public ASTWalker
{
public:
using ASTWalker::operator();
void operator()(Literal const&) override;
void operator()(Identifier const&) override;
void operator()(FunctionCall const& _funCall) override;
void operator()(ExpressionStatement const& _statement) override;
void operator()(Assignment const& _assignment) override;
void operator()(VariableDeclaration const& _varDecl) override;
void operator()(If const& _if) override;
void operator()(Switch const& _switch) override;
void operator()(FunctionDefinition const&) override;
void operator()(ForLoop const&) override;
void operator()(Break const&) override;
void operator()(Continue const&) override;
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void operator()(Leave const&) override;
void operator()(Block const& _block) override;
static std::map<Block const*, uint64_t> run(Block const& _block);
static constexpr uint64_t fnvPrime = 1099511628211u;
static constexpr uint64_t fnvEmptyHash = 14695981039346656037u;
private:
BlockHasher(std::map<Block const*, uint64_t>& _blockHashes): m_blockHashes(_blockHashes) {}
void hash8(uint8_t _value)
{
m_hash *= fnvPrime;
m_hash ^= _value;
}
void hash16(uint16_t _value)
{
hash8(static_cast<uint8_t>(_value & 0xFF));
hash8(static_cast<uint8_t>(_value >> 8));
}
void hash32(uint32_t _value)
{
hash16(static_cast<uint16_t>(_value & 0xFFFF));
hash16(static_cast<uint16_t>(_value >> 16));
}
void hash64(uint64_t _value)
{
hash32(static_cast<uint32_t>(_value & 0xFFFFFFFF));
hash32(static_cast<uint32_t>(_value >> 32));
}
std::map<Block const*, uint64_t>& m_blockHashes;
uint64_t m_hash = fnvEmptyHash;
struct VariableReference
{
size_t id = 0;
bool isExternal = false;
};
std::map<YulString, VariableReference> m_variableReferences;
std::vector<YulString> m_externalReferences;
size_t m_externalIdentifierCount = 0;
size_t m_internalIdentifierCount = 0;
};
}