source: src/Tuples/TupleAssignment.cc @ 5c6afcd

//
// 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.
//
// TupleAssignment.cc --
//
// Author           : Rodolfo G. Esteves
// Created On       : Mon May 18 07:44:20 2015
// Last Modified By : Rob Schluntz
// Last Modified On : Wed Nov 9 13:48:42 2016
// Update Count     : 2
//

#include "ResolvExpr/AlternativeFinder.h"
#include "ResolvExpr/Alternative.h"
#include "ResolvExpr/typeops.h"
#include "SynTree/Expression.h"
#include "SynTree/Initializer.h"
#include "Tuples.h"
#include "Explode.h"
#include "Common/SemanticError.h"
#include "InitTweak/InitTweak.h"

#include <functional>
#include <algorithm>
#include <iterator>
#include <iostream>
#include <cassert>
#include <set>
#include <unordered_set>

namespace Tuples {
        class TupleAssignSpotter {
          public:
                // dispatcher for Tuple (multiple and mass) assignment operations
                TupleAssignSpotter( ResolvExpr::AlternativeFinder & );
                void spot( UntypedExpr * expr, const std::list<ResolvExpr::AltList> &possibilities );

          private:
                void match();

                struct Matcher {
                  public:
                        Matcher( TupleAssignSpotter &spotter, const ResolvExpr::AltList & alts );
                        virtual ~Matcher() {}
                        virtual void match( std::list< Expression * > &out ) = 0;
                        ResolvExpr::AltList lhs, rhs;
                        TupleAssignSpotter &spotter;
                        std::list< ObjectDecl * > tmpDecls;
                };

                struct MassAssignMatcher : public Matcher {
                  public:
                        MassAssignMatcher( TupleAssignSpotter &spotter, const ResolvExpr::AltList & alts );
                        virtual void match( std::list< Expression * > &out );
                };

                struct MultipleAssignMatcher : public Matcher {
                  public:
                        MultipleAssignMatcher( TupleAssignSpotter &spot, const ResolvExpr::AltList & alts );
                        virtual void match( std::list< Expression * > &out );
                };

                ResolvExpr::AlternativeFinder &currentFinder;
                std::string fname;
                std::unique_ptr< Matcher > matcher;
        };

        /// true if expr is an expression of tuple type, i.e. a tuple expression, tuple variable, or MRV (multiple-return-value) function
        bool isTuple( Expression *expr ) {
                if ( ! expr ) return false;
                assert( expr->has_result() );
                return dynamic_cast<TupleExpr *>(expr) || expr->get_result()->size() > 1;
        }

        template< typename AltIter >
        bool isMultAssign( AltIter begin, AltIter end ) {
                // multiple assignment if more than one alternative in the range or if
                // the alternative is a tuple
                if ( begin == end ) return false;
                if ( isTuple( begin->expr ) ) return true;
                return ++begin != end;
        }

        bool pointsToTuple( Expression *expr ) {
                // also check for function returning tuple of reference types
                if ( CastExpr * castExpr = dynamic_cast< CastExpr * >( expr ) ) {
                        return pointsToTuple( castExpr->get_arg() );
                } else if ( AddressExpr *addr = dynamic_cast< AddressExpr * >( expr) ) {
                        return isTuple( addr->get_arg() );
                }
                return false;
        }

        void handleTupleAssignment( ResolvExpr::AlternativeFinder & currentFinder, UntypedExpr * expr, const std::list<ResolvExpr::AltList> &possibilities ) {
                TupleAssignSpotter spotter( currentFinder );
                spotter.spot( expr, possibilities );
        }

        TupleAssignSpotter::TupleAssignSpotter( ResolvExpr::AlternativeFinder &f )
                : currentFinder(f) {}

        void TupleAssignSpotter::spot( UntypedExpr * expr, const std::list<ResolvExpr::AltList> &possibilities ) {
                if (  NameExpr *op = dynamic_cast< NameExpr * >(expr->get_function()) ) {
                        if ( InitTweak::isCtorDtorAssign( op->get_name() ) ) {
                                fname = op->get_name();
                                for ( std::list<ResolvExpr::AltList>::const_iterator ali = possibilities.begin(); ali != possibilities.end(); ++ali ) {
                                        if ( ali->size() == 0 ) continue; // AlternativeFinder will natrually handle this case, if it's legal
                                        if ( ali->size() <= 1 && InitTweak::isAssignment( op->get_name() ) ) {
                                                // what does it mean if an assignment takes 1 argument? maybe someone defined such a function, in which case AlternativeFinder will naturally handle it
                                                continue;
                                        }

                                        assert( ! ali->empty() );
                                        // grab args 2-N and group into a TupleExpr
                                        const ResolvExpr::Alternative & alt1 = ali->front();
                                        auto begin = std::next(ali->begin(), 1), end = ali->end();
                                        if ( pointsToTuple(alt1.expr) ) {
                                                if ( isMultAssign( begin, end ) ) {
                                                        matcher.reset( new MultipleAssignMatcher( *this, *ali ) );
                                                } else {
                                                        // mass assignment
                                                        matcher.reset( new MassAssignMatcher( *this,  *ali ) );
                                                }
                                                match();
                                        }
                                }
                        }
                }
        }

        void TupleAssignSpotter::match() {
                assert ( matcher != 0 );

                std::list< Expression * > new_assigns;
                matcher->match( new_assigns );

                if ( new_assigns.empty() ) return;
                ResolvExpr::AltList current;
                // now resolve new assignments
                for ( std::list< Expression * >::iterator i = new_assigns.begin(); i != new_assigns.end(); ++i ) {
                        ResolvExpr::AlternativeFinder finder( currentFinder.get_indexer(), currentFinder.get_environ() );
                        try {
                                finder.findWithAdjustment(*i);
                        } catch (...) {
                                return; // xxx - no match should not mean failure, it just means this particular tuple assignment isn't valid
                        }
                        // prune expressions that don't coincide with
                        ResolvExpr::AltList alts = finder.get_alternatives();
                        assert( alts.size() == 1 );
                        assert( alts.front().expr != 0 );
                        current.push_back( alts.front() );
                }

                // extract expressions from the assignment alternatives to produce a list of assignments that
                // together form a single alternative
                std::list< Expression *> solved_assigns;
                for ( ResolvExpr::Alternative & alt : current ) {
                        solved_assigns.push_back( alt.expr->clone() );
                }
                // xxx - need to do this??
                ResolvExpr::TypeEnvironment compositeEnv;
                simpleCombineEnvironments( current.begin(), current.end(), compositeEnv );
                currentFinder.get_alternatives().push_front( ResolvExpr::Alternative(new TupleAssignExpr(solved_assigns, matcher->tmpDecls), compositeEnv, ResolvExpr::sumCost( current ) ) );
        }

        TupleAssignSpotter::Matcher::Matcher( TupleAssignSpotter &spotter, const ResolvExpr::AltList &alts ) : spotter(spotter) {
                assert( ! alts.empty() );
                ResolvExpr::Alternative lhsAlt = alts.front();
                // peel off the cast that exists on ctor/dtor expressions
                bool isCast = false;
                if ( CastExpr * castExpr = dynamic_cast< CastExpr * >( lhsAlt.expr ) ) {
                        lhsAlt.expr = castExpr->get_arg();
                        castExpr->set_arg( nullptr );
                        delete castExpr;
                        isCast = true;
                }

                // explode the lhs so that each field of the tuple-valued-expr is assigned.
                explode( lhsAlt, spotter.currentFinder.get_indexer(), back_inserter(lhs) );

                // and finally, re-add the cast to each lhs expr, so that qualified tuple fields can be constructed
                if ( isCast ) {
                        for ( ResolvExpr::Alternative & alt : lhs ) {
                                Expression *& expr = alt.expr;
                                Type * castType = expr->get_result()->clone();
                                Type * type = InitTweak::getPointerBase( castType );
                                assert( type );
                                type->get_qualifiers() -= Type::Qualifiers(true, true, true, false, true, true);
                                type->set_isLvalue( true ); // xxx - might not need this
                                expr = new CastExpr( expr, castType );
                        }
                }
        }

        TupleAssignSpotter::MassAssignMatcher::MassAssignMatcher( TupleAssignSpotter &spotter, const ResolvExpr::AltList & alts ) : Matcher( spotter, alts ) {
                assert( alts.size() == 1 || alts.size() == 2 );
                if ( alts.size() == 2 ) {
                        rhs.push_back( alts.back() );
                }
        }

        TupleAssignSpotter::MultipleAssignMatcher::MultipleAssignMatcher( TupleAssignSpotter &spotter, const ResolvExpr::AltList & alts ) : Matcher( spotter, alts ) {
                // explode the rhs so that each field of the tuple-valued-expr is assigned.
                explode( std::next(alts.begin(), 1), alts.end(), spotter.currentFinder.get_indexer(), back_inserter(rhs) );
        }

        UntypedExpr * createFunc( const std::string &fname, ObjectDecl *left, ObjectDecl *right ) {
                assert( left );
                std::list< Expression * > args;
                args.push_back( new AddressExpr( UntypedExpr::createDeref( new VariableExpr( left ) ) ) );
                // args.push_back( new AddressExpr( new VariableExpr( left ) ) );
                if ( right ) args.push_back( new VariableExpr( right ) );
                return new UntypedExpr( new NameExpr( fname ), args );
        }

        ObjectDecl * newObject( UniqueName & namer, Expression * expr ) {
                assert( expr->has_result() && ! expr->get_result()->isVoid() );
                return new ObjectDecl( namer.newName(), DeclarationNode::NoStorageClass, LinkageSpec::Cforall, nullptr, expr->get_result()->clone(), new SingleInit( expr->clone() ) );
        }

        void TupleAssignSpotter::MassAssignMatcher::match( std::list< Expression * > &out ) {
                static UniqueName lhsNamer( "__massassign_L" );
                static UniqueName rhsNamer( "__massassign_R" );
                assert ( ! lhs.empty() && rhs.size() <= 1);

                ObjectDecl * rtmp = rhs.size() == 1 ? newObject( rhsNamer, rhs.front().expr ) : nullptr;
                for ( ResolvExpr::Alternative & lhsAlt : lhs ) {
                        ObjectDecl * ltmp = newObject( lhsNamer, lhsAlt.expr );
                        out.push_back( createFunc( spotter.fname, ltmp, rtmp ) );
                        tmpDecls.push_back( ltmp );
                }
                if ( rtmp ) tmpDecls.push_back( rtmp );
        }

        void TupleAssignSpotter::MultipleAssignMatcher::match( std::list< Expression * > &out ) {
                static UniqueName lhsNamer( "__multassign_L" );
                static UniqueName rhsNamer( "__multassign_R" );

                // xxx - need more complicated matching?
                if ( lhs.size() == rhs.size() ) {
                        std::list< ObjectDecl * > ltmp;
                        std::list< ObjectDecl * > rtmp;
                        std::transform( lhs.begin(), lhs.end(), back_inserter( ltmp ), []( ResolvExpr::Alternative & alt ){
                                return newObject( lhsNamer, alt.expr );
                        });
                        std::transform( rhs.begin(), rhs.end(), back_inserter( rtmp ), []( ResolvExpr::Alternative & alt ){
                                return newObject( rhsNamer, alt.expr );
                        });
                        zipWith( ltmp.begin(), ltmp.end(), rtmp.begin(), rtmp.end(), back_inserter(out), [&](ObjectDecl * obj1, ObjectDecl * obj2 ) { return createFunc(spotter.fname, obj1, obj2); } );
                        tmpDecls.splice( tmpDecls.end(), ltmp );
                        tmpDecls.splice( tmpDecls.end(), rtmp );
                }
        }
} // namespace Tuples

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