source: src/Tuples/TupleAssignment.cc @ 1132b62

//
// 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 : Peter A. Buhr
// Last Modified On : Mon May 18 15:02:53 2015
// 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 "Common/SemanticError.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, std::list<ResolvExpr::AltList> &possibilities );

          private:
                void match();

                struct Matcher {
                  public:
                        Matcher( TupleAssignSpotter &spotter, ResolvExpr::Alternative & lhs, ResolvExpr::Alternative & rhs );
                        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, ResolvExpr::Alternative & lhs, ResolvExpr::Alternative & rhs );
                        virtual void match( std::list< Expression * > &out );
                };

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

                ResolvExpr::AlternativeFinder &currentFinder;
                // Expression *rhs, *lhs;
                Matcher *matcher = nullptr;
        };

        /// 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;
        }

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

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

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

        void TupleAssignSpotter::spot( UntypedExpr * expr, std::list<ResolvExpr::AltList> &possibilities ) {
                if (  NameExpr *assgnop = dynamic_cast< NameExpr * >(expr->get_function()) ) {
                        if ( assgnop->get_name() == "?=?" ) {
                                for ( std::list<ResolvExpr::AltList>::iterator ali = possibilities.begin(); ali != possibilities.end(); ++ali ) {
                                        if ( ali->size() != 2 ) continue; // what does it mean if an assignment takes >2 arguments? grab args 2-N and group into a TupleExpr, then proceed?
                                        ResolvExpr::Alternative & alt1 = ali->front(), & alt2 = ali->back();

                                        if ( pointsToTuple(alt1.expr) ) {
                                                MultipleAssignMatcher multiMatcher( *this, alt1, alt2 );
                                                MassAssignMatcher massMatcher( *this,  alt1, alt2 );
                                                if ( isTuple( alt2.expr ) ) {
                                                        matcher = &multiMatcher;
                                                } else {
                                                        // mass assignment
                                                        matcher = &massMatcher;
                                                }
                                                match();
                                        } else if ( isTuple( alt2.expr ) ) {
                                                throw SemanticError("Cannot assign a tuple value into a non-tuple lvalue.", expr);
                                        }
                                }
                        }
                }
        }

        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() );
                        finder.findWithAdjustment(*i);
                        // 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??
                // TypeEnvironment compositeEnv;
                // simpleCombineEnvironments( i->begin(), i->end(), compositeEnv );
                currentFinder.get_alternatives().push_front( ResolvExpr::Alternative(new TupleAssignExpr(solved_assigns, matcher->tmpDecls), currentFinder.get_environ(), ResolvExpr::sumCost( current ) ) );
        }

        TupleAssignSpotter::Matcher::Matcher( TupleAssignSpotter &spotter, ResolvExpr::Alternative & lhs, ResolvExpr::Alternative & rhs ) : spotter(spotter) {
                if (AddressExpr *addr = dynamic_cast<AddressExpr *>(lhs.expr) ) {
                        // xxx - not every assignment NEEDS to have the first argument as address-taken, e.g. a manual call to assignment. What to do in this case? skip it as a possibility for TupleAssignment, since the type will always be T*, where T can never be a tuple? Is this true?

                        // explode the lhs so that each field of the tuple-valued-expr is assigned.
                        ResolvExpr::Alternative lhsAlt( addr->get_arg()->clone(), lhs.env, lhs.cost, lhs.cvtCost );
                        explode( lhsAlt, back_inserter(this->lhs) );
                }
        }

        TupleAssignSpotter::MassAssignMatcher::MassAssignMatcher( TupleAssignSpotter &spotter, ResolvExpr::Alternative & lhs, ResolvExpr::Alternative & rhs ) : Matcher( spotter, lhs, rhs ) {
                this->rhs.push_back( rhs );
        }

        TupleAssignSpotter::MultipleAssignMatcher::MultipleAssignMatcher( TupleAssignSpotter &spotter, ResolvExpr::Alternative & lhs, ResolvExpr::Alternative & rhs ) : Matcher( spotter, lhs, rhs ) {

                // explode the rhs so that each field of the tuple-valued-expr is assigned.
                explode( rhs, back_inserter(this->rhs) );
        }

        UntypedExpr * createAssgn( ObjectDecl *left, ObjectDecl *right ) {
                assert( left && right );
                std::list< Expression * > args;
                args.push_back( new AddressExpr( new UntypedExpr( new NameExpr("*?"), std::list< Expression * >{ new VariableExpr( left ) } ) ) );
                args.push_back( new VariableExpr( right ) );
                return new UntypedExpr( new NameExpr( "?=?" ), 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 = newObject( rhsNamer, rhs.front().expr );
                for ( ResolvExpr::Alternative & lhsAlt : lhs ) {
                        ObjectDecl * ltmp = newObject( lhsNamer, new AddressExpr( lhsAlt.expr ) );
                        out.push_back( createAssgn( ltmp, rtmp ) );
                        tmpDecls.push_back( ltmp );
                }
                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, new AddressExpr( 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), createAssgn );
                        tmpDecls.splice( tmpDecls.end(), ltmp );
                        tmpDecls.splice( tmpDecls.end(), rtmp );
                }
        }
} // namespace Tuples

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// mode: c++ //
// compile-command: "make install" //
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