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//
// W A R N I N G
// -------------
//
// This file is not part of the Qt API. It exists purely as an
// implementation detail. This header file may change from version to
// version without notice, or even be removed.
//
// We mean it.
#ifndef Patternist_OptimizerFramework_H
#define Patternist_OptimizerFramework_H
#include <QSharedData>
#include "qexpression_p.h"
QT_BEGIN_HEADER
QT_BEGIN_NAMESPACE
namespace QPatternist
{
/**
* @short A factory for creating Expression instances.
*
* ExpressionIdentifier is one of the building block of Patternist's
* optimizer framework. An ExpressionIdentifier sub-class has
* the responsibility of creating the Expression that should be
* the result of the optimization.
*
* This class and sub-classes are never used on their own,
* but in cooperation with OptimizationPass.
*
* @author Frans englich <frans.englich@nokia.com>
* @ingroup Patternist_expressions
*/
class ExpressionCreator : public QSharedData
{
public:
typedef QExplicitlySharedDataPointer<ExpressionCreator> Ptr;
/**
* For some reason this constructor cannot be synthesized.
*/
inline ExpressionCreator()
{
}
virtual ~ExpressionCreator();
/**
* Creates an expression that has @p operands as operands.
*
* The Expression that is returned is guaranteed, by the caller,
* to get a treatment identical to if the expression was created
* in an ordinary compilation(via the parser, and so forth). That is,
* Expression::typeCheck() and Expression::compress() stages will be
* carried out on the returned expression.
*
* @returns an Expression::Ptr that never is non @c null, valid pointer
*/
virtual Expression::Ptr create(const Expression::List &operands,
const StaticContext::Ptr &context,
const SourceLocationReflection *const) const = 0;
private:
Q_DISABLE_COPY(ExpressionCreator)
};
/**
* @short Abstract base class for all classes that identify Expressions
* based on some criteria.
*
* ExpressionIdentifier is one of the building block of Patternist's
* optimizer framework. An ExpressionIdentifier sub-class has
* the responsibility of determining whether a particular Expression
* is the one an OptimizationPass should apply for.
*
* This class and sub-classes are never used on their own,
* but in cooperation with OptimizationPass.
*
* @author Frans englich <frans.englich@nokia.com>
* @ingroup Patternist_expressions
*/
class ExpressionIdentifier : public QSharedData
{
public:
typedef QExplicitlySharedDataPointer<ExpressionIdentifier> Ptr;
typedef QList<ExpressionIdentifier::Ptr> List;
/**
* For some reason this constructor cannot be synthesized.
*/
inline ExpressionIdentifier()
{
}
virtual ~ExpressionIdentifier();
/**
* @param expr the Expression to be tested. This is guranteed
* to always be a non @c null, valid pointer.
*
* @returns @c true if @p expr matches as according to this ExpressionIdentifier,
* otherwise @c false.
*/
virtual bool matches(const Expression::Ptr &expr) const = 0;
private:
Q_DISABLE_COPY(ExpressionIdentifier)
};
/**
* @short Describes how a particular optimization pass should be carried out.
*
* OptimizationPass is essentially a declaration, which describes
* how an optimization pass in the form of an AST rewrite should be done,
* by describing what that should be rewritten into what how.
*
* Each OptimizationPass is applied to a "start" Expression. The Expression
* that qualifies as a start Expression for the OptimizationPass in question is
* determined by startIdentifier; if its ExpressionIdentifier::matches() function
* returns @c true, the optimizer continues to apply this OptimizationPass.
*
* After a start Expression has been found, it is verified if the operands matches
* as well by applying the ExpressionIdentifiers in operandIdentifiers to the
* start Expression's operands. Similarly, if the operands matches what
* operandIdentifiers requires, the optimizer continues to apply this OptimizationPass.
*
* At this stage, it has been concluded that the OptimizationPass validly applies, and
* what now remains is to carry out the actual rewrite. The Expression rewritten
* to is the one returned by ExpressionCreator::create(), when invoked via the resultCreator
* variable.
*
* How these components, startIdentifier, operandIdentifiers, sourceExpression,
* and resultCreator interacts with one another is described in more detail
* in the member documentation as well as the classes they are instances of.
*
* @author Frans englich <frans.englich@nokia.com>
* @ingroup Patternist_expressions
*/
class OptimizationPass : public QSharedData
{
public:
typedef QExplicitlySharedDataPointer<OptimizationPass> Ptr;
typedef QList<OptimizationPass::Ptr> List;
enum OperandsMatchMethod
{
/**
* All operands must match in the same order the ExpressionMarkers do.
*/
Sequential = 1,
/**
* Matches if all operands are matched, regardless of their order. This is
* useful when an OptimizationPass is matching an Expression that has two operands
* and that both of them can appear on the left or right hand as long as it is those
* two.
*
* This comparison method only works when two operands
* needs to be matched.
*/
AnyOrder
};
/**
* An ExpressionMarker identifies an operand Expression relatively
* the start Expression by that each integer identifies a step
* in a descending AST walk. For example an ExpressionMarker with
* only one entry that is 0(zero), identifies the first operand of the
* start Expression. An ExpressionMarker containing 1, 2 in that order
* identifies the third operand of the second operand of the start Expression.
*/
typedef QList<qint8> ExpressionMarker;
/**
* Creates an OptimizationPass and sets its public variables
* to the corresponding values passed in this constructor.
*/
OptimizationPass(const ExpressionIdentifier::Ptr &startID,
const ExpressionIdentifier::List &operandIDs,
const ExpressionMarker &sourceExpr,
const ExpressionCreator::Ptr &resultCtor = ExpressionCreator::Ptr(),
const OperandsMatchMethod matchMethod = Sequential);
/**
* The ExpressionIdentifier that must the Expression this OptimizationPass concerns.
*
* If this variable is @c null, it means that the start Expression does
* not have to match any particular ExpressionIdentifier, but is fine as is.
*
* One might wonder what the purpose of this startIdentifier is, considering
* that what start Expression an OptimizationPass can at all apply to is
* naturally determined by what Expression::optimizationPasses() re-implementation that
* returns this OptimizationPass. The reason is that in some cases an OptimizationPass
* nevertheless doesn't apply. For example, optimizations applying to a ValueComparison
* might depend on what operator that is in use.
*
* May be @c null or point to an ExpressionIdentifier.
*/
const ExpressionIdentifier::Ptr startIdentifier;
/**
* In order for an OptimizationPass to apply, the start Expression's
* operands must be matched with this list of ExpressionIdentifier instances.
* The first ExpressionIdentifier is applied to the first operand, the second
* ExpressionIdentifier to the second operand, and so forth until all operands
* have been iterated.
*
* Entries in this list may be @c null, and those signals that the corresponding
* operand is not constrained. For example, if the third ExpressionIdentifier in
* the list is @c null, it signals that the third operand may be anykind of expression.
*
* May be empty or contain an arbitrary amount of objects or @c null pointers.
*/
const ExpressionIdentifier::List operandIdentifiers;
/**
* Identifies the expression that should be part of the new expression
* that this OptimizationPass rewrites to. If this list is empty, it
* means that the result is not derived from the existing tree, and
* that resultCreator will exclusively be used for creating the result
* Expression.
*
* How the ExpressionMarker identifies an Expression is document in
* its documentation.
*
* May be empty.
*/
const ExpressionMarker sourceExpression;
/**
* This is the ExpressionCreator that will be used to create the
* Expression which is the result. ExpressionCreator::create()
* will be passed as operands the Expression that sourceExpression
* specify, if any.
*
* If this variable is @c null, the result Expression will be the one
* sourceExpression identifies.
*/
const ExpressionCreator::Ptr resultCreator;
const OperandsMatchMethod operandsMatchMethod;
private:
Q_DISABLE_COPY(OptimizationPass)
};
}
QT_END_NAMESPACE
QT_END_HEADER
#endif