/*

  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/>.

*/

// SPDX-License-Identifier: GPL-3.0

/**

 * Module providing metrics for the optimizer.

 */

#pragma once

#include <libyul/optimiser/ASTWalker.h>

#include <liblangutil/EVMVersion.h>

namespace solidity::yul

{

struct Dialect;

struct EVMDialect;

/**

 * Weights to be assigned to specific yul statements and expressions by a metric.

 *

 * The default values are meant to reflect specifically the number of AST nodes.

 *

 * The following AST elements have a default cost of zero (because the cleanup phase would

 * remove them anyway or they are just wrappers around something else that will be counted instead):

 *  - 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)

 *  - literal zeros (we optimistically assume they can be copied from somewhere else)

 *

 * 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.

*/

struct CodeWeights

{

  // Statements

  size_t expressionStatementCost = 0;

  size_t assignmentCost = 0;

  size_t variableDeclarationCost = 0;

  size_t functionDefinitionCost = 1;

  size_t ifCost = 2;

  size_t switchCost = 1;

  size_t caseCost = 2;

  size_t forLoopCost = 3;

  size_t breakCost = 2;

  size_t continueCost = 2;

  size_t leaveCost = 2;

  size_t blockCost = 0;

  // Expressions

  size_t functionCallCost = 1;

  size_t identifierCost = 0;

  size_t literalCost = 1;

  size_t literalZeroCost = 0;

  size_t costOf(Statement const& _statement) const;

  size_t costOf(Expression const& _expression) const;

};

/**

 * Metric for the size of code.

 * 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.

 *

 * The cost of each statement and expression type is configurable via CodeWeights.

 */

class CodeSize: public ASTWalker

{

public:

  static size_t codeSize(Statement const& _statement, CodeWeights const& _weights = {});

  static size_t codeSize(Expression const& _expression, CodeWeights const& _weights = {});

  static size_t codeSize(Block const& _block, CodeWeights const& _weights = {});

  static size_t codeSizeIncludingFunctions(Block const& _block, CodeWeights const& _weights = {});

private:

  CodeSize(bool _ignoreFunctions = true, CodeWeights const& _weights = {}):

    m_ignoreFunctions(_ignoreFunctions),

    m_weights(_weights) {}

  void visit(Statement const& _statement) override;

  void visit(Expression const& _expression) override;

private:

  bool m_ignoreFunctions;

  size_t m_size = 0;

  CodeWeights m_weights;

};

/**

 * 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(evmasm::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;

};

}