solidity/libyul/optimiser/Metrics.h
2019-11-11 16:04:39 +01:00

110 lines
3.3 KiB
C++

/*
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/>.
*/
/**
* Module providing metrics for the optimizer.
*/
#pragma once
#include <libyul/optimiser/ASTWalker.h>
#include <liblangutil/EVMVersion.h>
namespace yul
{
struct Dialect;
struct EVMDialect;
/**
* Metric for the size of code.
* More specifically, the number of AST nodes.
* Ignores function definitions while traversing the AST by default.
* If you want to know the size of a function, you have to invoke this on its body.
*
* As an exception, the following AST elements have a cost of zero:
* - expression statement (only the expression inside has a cost)
* - block (only the statements inside have a cost)
* - variable references
* - variable declarations (only the right hand side has a cost)
* - assignments (only the value has a cost)
*
* As another exception, each statement incurs and additional cost of one
* per jump/branch. This means if, break and continue statements have a cost of 2,
* switch statements have a cost of 1 plus the number of cases times two,
* and for loops cost 3.
*/
class CodeSize: public ASTWalker
{
public:
static size_t codeSize(Statement const& _statement);
static size_t codeSize(Expression const& _expression);
static size_t codeSize(Block const& _block);
static size_t codeSizeIncludingFunctions(Block const& _block);
private:
CodeSize(bool _ignoreFunctions = true): m_ignoreFunctions(_ignoreFunctions) {}
void visit(Statement const& _statement) override;
void visit(Expression const& _expression) override;
private:
bool m_ignoreFunctions;
size_t m_size = 0;
};
/**
* Very rough cost that takes the size and execution cost of code into account.
* The cost per AST element is one, except for literals where it is the byte size.
* Function calls cost 50. Instructions cost 0 for 3 or less gas (same as DUP),
* 2 for up to 10 and 50 otherwise.
*/
class CodeCost: public ASTWalker
{
public:
static size_t codeCost(Dialect const& _dialect, Expression const& _expression);
private:
CodeCost(Dialect const& _dialect): m_dialect(_dialect) {}
void operator()(FunctionCall const& _funCall) override;
void operator()(Literal const& _literal) override;
void visit(Statement const& _statement) override;
void visit(Expression const& _expression) override;
private:
void addInstructionCost(dev::eth::Instruction _instruction);
Dialect const& m_dialect;
size_t m_cost = 0;
};
/**
* Counts the number of assignments to every variable.
* Only works after running the Disambiguator.
*/
class AssignmentCounter: public ASTWalker
{
public:
using ASTWalker::operator();
void operator()(Assignment const& _assignment) override;
std::size_t assignmentCount(YulString _name) const;
private:
std::map<YulString, size_t> m_assignmentCounters;
};
}