solidity/libyul/optimiser/Semantics.h
2020-04-02 18:00:44 -05:00

205 lines
6.1 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/>.
*/
/**
* Specific AST walkers that collect semantical facts.
*/
#pragma once
#include <libyul/optimiser/ASTWalker.h>
#include <libyul/SideEffects.h>
#include <libyul/optimiser/CallGraphGenerator.h>
#include <libyul/AsmData.h>
#include <set>
namespace solidity::yul
{
struct Dialect;
/**
* Specific AST walker that determines side-effect free-ness and movability of code.
* Enters into function definitions.
*/
class SideEffectsCollector: public ASTWalker
{
public:
explicit SideEffectsCollector(
Dialect const& _dialect,
std::map<YulString, SideEffects> const* _functionSideEffects = nullptr
): m_dialect(_dialect), m_functionSideEffects(_functionSideEffects) {}
SideEffectsCollector(
Dialect const& _dialect,
Expression const& _expression,
std::map<YulString, SideEffects> const* _functionSideEffects = nullptr
);
SideEffectsCollector(Dialect const& _dialect, Statement const& _statement);
SideEffectsCollector(
Dialect const& _dialect,
Block const& _ast,
std::map<YulString, SideEffects> const* _functionSideEffects = nullptr
);
using ASTWalker::operator();
void operator()(FunctionCall const& _functionCall) override;
bool movable() const { return m_sideEffects.movable; }
bool sideEffectFree(bool _allowMSizeModification = false) const
{
if (_allowMSizeModification)
return sideEffectFreeIfNoMSize();
else
return m_sideEffects.sideEffectFree;
}
bool sideEffectFreeIfNoMSize() const { return m_sideEffects.sideEffectFreeIfNoMSize; }
bool invalidatesStorage() const { return m_sideEffects.invalidatesStorage; }
bool invalidatesMemory() const { return m_sideEffects.invalidatesMemory; }
private:
Dialect const& m_dialect;
std::map<YulString, SideEffects> const* m_functionSideEffects = nullptr;
SideEffects m_sideEffects;
};
/**
* This class can be used to determine the side-effects of user-defined functions.
*
* It is given a dialect and a mapping that represents the direct calls from user-defined
* functions to other user-defined functions and built-in functions.
*/
class SideEffectsPropagator
{
public:
static std::map<YulString, SideEffects> sideEffects(
Dialect const& _dialect,
CallGraph const& _directCallGraph
);
};
/**
* Class that can be used to find out if certain code contains the MSize instruction.
*
* Note that this is a purely syntactic property meaning that even if this is false,
* the code can still contain calls to functions that contain the msize instruction.
*
* The only safe way to determine this is by passing the full AST.
*/
class MSizeFinder: public ASTWalker
{
public:
static bool containsMSize(Dialect const& _dialect, Block const& _ast);
using ASTWalker::operator();
void operator()(FunctionCall const& _funCall) override;
private:
MSizeFinder(Dialect const& _dialect): m_dialect(_dialect) {}
Dialect const& m_dialect;
bool m_msizeFound = false;
};
/**
* Class that can be used to find out if the given function contains the ``leave`` statement.
*
* Returns true even in the case where the function definition contains another function definition
* that contains the leave statement.
*/
class LeaveFinder: public ASTWalker
{
public:
static bool containsLeave(FunctionDefinition const& _fun)
{
LeaveFinder f;
f(_fun);
return f.m_leaveFound;
}
using ASTWalker::operator();
void operator()(Leave const&) override { m_leaveFound = true; }
private:
LeaveFinder() = default;
bool m_leaveFound = false;
};
/**
* Specific AST walker that determines whether an expression is movable
* and collects the referenced variables.
* Can only be used on expressions.
*/
class MovableChecker: public SideEffectsCollector
{
public:
explicit MovableChecker(
Dialect const& _dialect,
std::map<YulString, SideEffects> const* _functionSideEffects = nullptr
): SideEffectsCollector(_dialect, _functionSideEffects) {}
MovableChecker(Dialect const& _dialect, Expression const& _expression);
void operator()(Identifier const& _identifier) override;
/// Disallow visiting anything apart from Expressions (this throws).
void visit(Statement const&) override;
using ASTWalker::visit;
std::set<YulString> const& referencedVariables() const { return m_variableReferences; }
private:
/// Which variables the current expression references.
std::set<YulString> m_variableReferences;
};
/**
* Helper class to find "irregular" control flow.
* This includes termination, break and continue.
*/
class TerminationFinder
{
public:
// TODO check all uses of TerminationFinder!
enum class ControlFlow { FlowOut, Break, Continue, Terminate, Leave };
TerminationFinder(Dialect const& _dialect): m_dialect(_dialect) {}
/// @returns the index of the first statement in the provided sequence
/// that is an unconditional ``break``, ``continue``, ``leave`` or a
/// call to a terminating builtin function.
/// If control flow can continue at the end of the list,
/// returns `FlowOut` and ``size_t(-1)``.
/// The function might return ``FlowOut`` even though control
/// flow cannot actually continue.
std::pair<ControlFlow, size_t> firstUnconditionalControlFlowChange(
std::vector<Statement> const& _statements
);
/// @returns the control flow type of the given statement.
/// This function could return FlowOut even if control flow never continues.
ControlFlow controlFlowKind(Statement const& _statement);
/// @returns true if the expression statement is a direct
/// call to a builtin terminating function like
/// ``stop``, ``revert`` or ``return``.
bool isTerminatingBuiltin(ExpressionStatement const& _exprStmnt);
private:
Dialect const& m_dialect;
};
}