path: root/libyul/optimiser/FullInliner.h

/*
    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 performs function inlining for arbitrary functions.
 */
#pragma once

#include <libyul/AsmDataForward.h>

#include <libyul/optimiser/ASTCopier.h>
#include <libyul/optimiser/ASTWalker.h>
#include <libyul/optimiser/NameDispenser.h>
#include <libyul/Exceptions.h>

#include <liblangutil/SourceLocation.h>

#include <boost/variant.hpp>
#include <boost/optional.hpp>

#include <set>

namespace yul
{

class NameCollector;


/**
 * Optimiser component that modifies an AST in place, inlining functions.
 * Expressions are expected to be split, i.e. the component will only inline
 * function calls that are at the root of the expression and that only contains
 * variables as arguments. More specifically, it will inline
 *  - let x1, ..., xn := f(a1, ..., am)
 *  - x1, ..., xn := f(a1, ..., am)
 * f(a1, ..., am)
 *
 * The transform changes code of the form
 *
 * function f(a, b) -> c { ... }
 * let z := f(x, y)
 *
 * into
 *
 * function f(a, b) -> c { ... }
 *
 * let f_a := x
 * let f_b := y
 * let f_c
 * code of f, with replacements: a -> f_a, b -> f_b, c -> f_c
 * let z := f_c
 *
 * Prerequisites: Disambiguator, Function Hoister
 * More efficient if run after: Expression Splitter
 */
class FullInliner: public ASTModifier
{
public:
    explicit FullInliner(Block& _ast, NameDispenser& _dispenser);

    void run();

    /// Inlining heuristic.
    /// @param _callSite the name of the function in which the function call is located.
    bool shallInline(FunctionCall const& _funCall, YulString _callSite);

    FunctionDefinition& function(YulString _name) { return *m_functions.at(_name); }

private:
    void updateCodeSize(FunctionDefinition& fun);
    void handleBlock(YulString _currentFunctionName, Block& _block);

    /// The AST to be modified. The root block itself will not be modified, because
    /// we store pointers to functions.
    Block& m_ast;
    std::map<YulString, FunctionDefinition*> m_functions;
    /// Names of functions to always inline.
    std::set<YulString> m_alwaysInline;
    /// Variables that are constants (used for inlining heuristic)
    std::set<YulString> m_constants;
    std::map<YulString, size_t> m_functionSizes;
    NameDispenser& m_nameDispenser;
};

/**
 * Class that walks the AST of a block that does not contain function definitions and perform
 * the actual code modifications.
 */
class InlineModifier: public ASTModifier
{
public:
    InlineModifier(FullInliner& _driver, NameDispenser& _nameDispenser, YulString _functionName):
        m_currentFunction(std::move(_functionName)),
        m_driver(_driver),
        m_nameDispenser(_nameDispenser)
    { }

    void operator()(Block& _block) override;

private:
    boost::optional<std::vector<Statement>> tryInlineStatement(Statement& _statement);
    std::vector<Statement> performInline(Statement& _statement, FunctionCall& _funCall);

    YulString m_currentFunction;
    FullInliner& m_driver;
    NameDispenser& m_nameDispenser;
};

/**
 * Creates a copy of a block that is supposed to be the body of a function.
 * Applies replacements to referenced variables and creates new names for
 * variable declarations.
 */
class BodyCopier: public ASTCopier
{
public:
    BodyCopier(
        NameDispenser& _nameDispenser,
        YulString _varNamePrefix,
        std::map<YulString, YulString> const& _variableReplacements
    ):
        m_nameDispenser(_nameDispenser),
        m_varNamePrefix(_varNamePrefix),
        m_variableReplacements(_variableReplacements)
    {}

    using ASTCopier::operator ();

    Statement operator()(VariableDeclaration const& _varDecl) override;
    Statement operator()(FunctionDefinition const& _funDef) override;

    YulString translateIdentifier(YulString _name) override;

    NameDispenser& m_nameDispenser;
    YulString m_varNamePrefix;
    std::map<YulString, YulString> m_variableReplacements;
};


}