source: src/Tuples/Tuples.cc @ 594e1db

//
// Cforall Version 1.0.0 Copyright (C) 2015 University of Waterloo
//
// The contents of this file are covered under the licence agreement in the
// file "LICENCE" distributed with Cforall.
//
// Tuples.cc -- A collection of tuple operations.
//
// Author           : Andrew Beach
// Created On       : Mon Jun 17 14:41:00 2019
// Last Modified By : Andrew Beach
// Last Modified On : Mon May 16 16:15:00 2022
// Update Count     : 2
//

#include "Tuples.h"

#include "AST/Pass.hpp"
#include "AST/LinkageSpec.hpp"
#include "Common/PassVisitor.h"
#include "InitTweak/InitTweak.h"

namespace Tuples {

namespace {
        /// Checks if impurity (read: side-effects) may exist in a piece of code.
        /// Currently gives a very crude approximation, wherein any function
        /// call expression means the code may be impure.
        struct ImpurityDetector_old : public WithShortCircuiting {
                bool const ignoreUnique;
                bool maybeImpure;

                ImpurityDetector_old( bool ignoreUnique ) :
                        ignoreUnique( ignoreUnique ), maybeImpure( false )
                {}

                void previsit( const ApplicationExpr * appExpr ) {
                        visit_children = false;
                        if ( const DeclarationWithType * function =
                                        InitTweak::getFunction( appExpr ) ) {
                                if ( function->linkage == LinkageSpec::Intrinsic ) {
                                        if ( function->name == "*?" || function->name == "?[?]" ) {
                                                // intrinsic dereference, subscript are pure,
                                                // but need to recursively look for impurity
                                                visit_children = true;
                                                return;
                                        }
                                }
                        }
                        maybeImpure = true;
                }

                void previsit( const UntypedExpr * ) {
                        maybeImpure = true;
                        visit_children = false;
                }

                void previsit( const UniqueExpr * ) {
                        if ( ignoreUnique ) {
                                // bottom out at unique expression.
                                // The existence of a unique expression doesn't change the purity of an expression.
                                // That is, even if the wrapped expression is impure, the wrapper protects the rest of the expression.
                                visit_children = false;
                                return;
                        }
                }
        };

        bool detectImpurity( const Expression * expr, bool ignoreUnique ) {
                PassVisitor<ImpurityDetector_old> detector( ignoreUnique );
                expr->accept( detector );
                return detector.pass.maybeImpure;
        }

        /// Determines if impurity (read: side-effects) may exist in a piece of code. Currently gives
        /// a very crude approximation, wherein any function call expression means the code may be
        /// impure.
    struct ImpurityDetector : public ast::WithShortCircuiting {
                bool result = false;

                void previsit( ast::ApplicationExpr const * appExpr ) {
                        if ( ast::DeclWithType const * function = InitTweak::getFunction( appExpr ) ) {
                                if ( function->linkage == ast::Linkage::Intrinsic
                                                && ( function->name == "*?" || function->name == "?[?]" ) ) {
                                        return;
                                }
                        }
                        result = true; visit_children = false;
                }
                void previsit( ast::UntypedExpr const * ) {
                        result = true; visit_children = false;
                }
        };

        struct ImpurityDetectorIgnoreUnique : public ImpurityDetector {
                using ImpurityDetector::previsit;
                void previsit( ast::UniqueExpr const * ) {
                        visit_children = false;
                }
        };
} // namespace

bool maybeImpure( const ast::Expr * expr ) {
        return ast::Pass<ImpurityDetector>::read( expr );
}

bool maybeImpureIgnoreUnique( const ast::Expr * expr ) {
        return ast::Pass<ImpurityDetectorIgnoreUnique>::read( expr );
}

bool maybeImpure( const Expression * expr ) {
        return detectImpurity( expr, false );
}

bool maybeImpureIgnoreUnique( const Expression * expr ) {
        return detectImpurity( expr, true );
}

} // namespace Tuples

// Local Variables: //
// tab-width: 4 //
// mode: c++ //
// compile-command: "make install" //
// End: //