source: src/Tuples/TupleAssignment.cc @ c6bbcdb

//
// 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 : Fri Mar 17 09:43:03 2017
// Update Count     : 8
//

#include <algorithm>                       // for transform
#include <cassert>                         // for assert
#include <iterator>                        // for back_insert_iterator, back...
#include <list>                            // for _List_const_iterator, _Lis...
#include <memory>                          // for unique_ptr, allocator_trai...
#include <string>                          // for string
#include <vector>

#include "CodeGen/OperatorTable.h"
#include "Common/PassVisitor.h"
#include "Common/UniqueName.h"             // for UniqueName
#include "Common/utility.h"                // for zipWith
#include "Explode.h"                       // for explode
#include "InitTweak/GenInit.h"             // for genCtorInit
#include "InitTweak/InitTweak.h"           // for getPointerBase, isAssignment
#include "Parser/LinkageSpec.h"            // for Cforall
#include "ResolvExpr/Alternative.h"        // for AltList, Alternative
#include "ResolvExpr/AlternativeFinder.h"  // for AlternativeFinder, simpleC...
#include "ResolvExpr/Cost.h"               // for Cost
#include "ResolvExpr/Resolver.h"           // for resolveCtorInit
#include "ResolvExpr/TypeEnvironment.h"    // for TypeEnvironment
#include "ResolvExpr/typeops.h"            // for combos
#include "SynTree/Declaration.h"           // for ObjectDecl
#include "SynTree/Expression.h"            // for Expression, CastExpr, Name...
#include "SynTree/Initializer.h"           // for ConstructorInit, SingleInit
#include "SynTree/Statement.h"             // for ExprStmt
#include "SynTree/Type.h"                  // for Type, Type::Qualifiers
#include "SynTree/TypeSubstitution.h"      // for TypeSubstitution
#include "SynTree/Visitor.h"               // for Visitor

#if 0
#define PRINT(x) x
#else
#define PRINT(x)
#endif

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

          private:
                void match();

                struct Matcher {
                  public:
                        Matcher( TupleAssignSpotter &spotter, const ResolvExpr::AltList& lhs, const
                                ResolvExpr::AltList& rhs );
                        virtual ~Matcher() {}
                        virtual void match( std::list< Expression * > &out ) = 0;
                        ObjectDecl * newObject( UniqueName & namer, Expression * expr );
                        ResolvExpr::AltList lhs, rhs;
                        TupleAssignSpotter &spotter;
                        ResolvExpr::Cost baseCost;
                        std::list< ObjectDecl * > tmpDecls;
                        ResolvExpr::TypeEnvironment compositeEnv;
                };

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

                struct MultipleAssignMatcher : public Matcher {
                  public:
                        MultipleAssignMatcher( TupleAssignSpotter &spotter, const ResolvExpr::AltList& lhs,
                                const ResolvExpr::AltList& rhs ) : Matcher(spotter, lhs, rhs) {}
                        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
        bool isTuple( Expression *expr ) {
                if ( ! expr ) return false;
                assert( expr->result );
                return dynamic_cast< TupleType * >( expr->get_result()->stripReferences() );
        }

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

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

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

        void TupleAssignSpotter::spot( UntypedExpr * expr,
                        std::vector<ResolvExpr::AlternativeFinder> &args ) {
                if (  NameExpr *op = dynamic_cast< NameExpr * >(expr->get_function()) ) {
                        if ( CodeGen::isCtorDtorAssign( op->get_name() ) ) {
                                fname = op->get_name();

                                // AlternativeFinder will naturally handle this case case, if it's legal
                                if ( args.size() == 0 ) return;

                                // if an assignment only takes 1 argument, that's odd, but maybe someone wrote
                                // the function, in which case AlternativeFinder will handle it normally
                                if ( args.size() == 1 && CodeGen::isAssignment( fname ) ) return;

                                // look over all possible left-hand-sides
                                for ( ResolvExpr::Alternative& lhsAlt : args[0] ) {
                                        // skip non-tuple LHS
                                        if ( ! refToTuple(lhsAlt.expr) ) continue;

                                        // explode is aware of casts - ensure every LHS expression is sent into explode
                                        // with a reference cast
                                        // xxx - this seems to change the alternatives before the normal
                                        //  AlternativeFinder flow; maybe this is desired?
                                        if ( ! dynamic_cast<CastExpr*>( lhsAlt.expr ) ) {
                                                lhsAlt.expr = new CastExpr( lhsAlt.expr,
                                                                new ReferenceType( Type::Qualifiers(),
                                                                        lhsAlt.expr->result->clone() ) );
                                        }

                                        // explode the LHS so that each field of a tuple-valued-expr is assigned
                                        ResolvExpr::AltList lhs;
                                        explode( lhsAlt, currentFinder.get_indexer(), back_inserter(lhs), true );
                                        for ( ResolvExpr::Alternative& alt : lhs ) {
                                                // each LHS value must be a reference - some come in with a cast expression,
                                                // if not just cast to reference here
                                                if ( ! dynamic_cast<ReferenceType*>( alt.expr->get_result() ) ) {
                                                        alt.expr = new CastExpr( alt.expr,
                                                                new ReferenceType( Type::Qualifiers(),
                                                                        alt.expr->get_result()->clone() ) );
                                                }
                                        }

                                        if ( args.size() == 1 ) {
                                                // mass default-initialization/destruction
                                                ResolvExpr::AltList rhs{};
                                                matcher.reset( new MassAssignMatcher( *this, lhs, rhs ) );
                                                match();
                                        } else if ( args.size() > 2 ) {
                                                // expand all possible RHS possibilities
                                                // TODO build iterative version of this instead of using combos
                                                std::vector< ResolvExpr::AltList > rhsAlts;
                                                combos( std::next(args.begin(), 1), args.end(),
                                                        std::back_inserter( rhsAlts ) );
                                                for ( const ResolvExpr::AltList& rhsAlt : rhsAlts ) {
                                                        // multiple assignment
                                                        ResolvExpr::AltList rhs;
                                                        explode( rhsAlt, currentFinder.get_indexer(),
                                                                std::back_inserter(rhs), true );
                                                        matcher.reset( new MultipleAssignMatcher( *this, lhs, rhs ) );
                                                        match();
                                                }
                                        } else {
                                                for ( const ResolvExpr::Alternative& rhsAlt : args[1] ) {
                                                        ResolvExpr::AltList rhs;
                                                        if ( isTuple(rhsAlt.expr) ) {
                                                                // multiple assignment
                                                                explode( rhsAlt, currentFinder.get_indexer(),
                                                                        std::back_inserter(rhs), true );
                                                                matcher.reset( new MultipleAssignMatcher( *this, lhs, rhs ) );
                                                        } else {
                                                                // mass assignment
                                                                rhs.push_back( rhsAlt );
                                                                matcher.reset( new MassAssignMatcher( *this, lhs, rhs ) );
                                                        }
                                                        match();
                                                }
                                        }
                                }
                        }
                }
        }

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

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

                if ( ! matcher->lhs.empty() || ! matcher->rhs.empty() ) {
                        // if both lhs and rhs are empty then this is the empty tuple case, wherein it's okay for new_assigns to be empty.
                        // if not the empty tuple case, return early so that no new alternatives are generated.
                        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 ) {
                        PRINT(
                                std::cerr << "== resolving tuple assign ==" << std::endl;
                                std::cerr << *i << std::endl;
                        )

                        ResolvExpr::AlternativeFinder finder{ currentFinder.get_indexer(),
                                matcher->compositeEnv };

                        try {
                                finder.findWithAdjustment(*i);
                        } catch (...) {
                                return; // 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() );
                }
                // combine assignment environments into combined expression environment
                simpleCombineEnvironments( current.begin(), current.end(), matcher->compositeEnv );
                // xxx -- was push_front
                currentFinder.get_alternatives().push_back( ResolvExpr::Alternative(
                        new TupleAssignExpr(solved_assigns, matcher->tmpDecls), matcher->compositeEnv,
                        ResolvExpr::sumCost( current ) + matcher->baseCost ) );
        }

        TupleAssignSpotter::Matcher::Matcher( TupleAssignSpotter &spotter,
                const ResolvExpr::AltList &lhs, const ResolvExpr::AltList &rhs )
        : lhs(lhs), rhs(rhs), spotter(spotter),
          baseCost( ResolvExpr::sumCost( lhs ) + ResolvExpr::sumCost( rhs ) ) {
                simpleCombineEnvironments( lhs.begin(), lhs.end(), compositeEnv );
                simpleCombineEnvironments( rhs.begin(), rhs.end(), compositeEnv );
        }

        UntypedExpr * createFunc( const std::string &fname, ObjectDecl *left, ObjectDecl *right ) {
                assert( left );
                std::list< Expression * > args;
                args.push_back( new VariableExpr( left ) );
                // args.push_back( new AddressExpr( new VariableExpr( left ) ) );
                if ( right ) args.push_back( new VariableExpr( right ) );
                if ( left->type->referenceDepth() > 1 && CodeGen::isConstructor( fname ) ) {
                        args.front() = new AddressExpr( args.front() );
                        if ( right ) args.back() = new AddressExpr( args.back() );
                        return new UntypedExpr( new NameExpr( "?=?" ), args );
                } else {
                        return new UntypedExpr( new NameExpr( fname ), args );
                }
        }

        // removes environments from subexpressions within statement exprs, which could throw off later passes like those in Box which rely on PolyMutator, and adds the bindings to the compositeEnv
        // xxx - maybe this should happen in alternative finder for every StmtExpr?
        struct EnvRemover {
                void previsit( ExprStmt * stmt ) {
                        assert( compositeEnv );
                        if ( stmt->expr->env ) {
                                compositeEnv->add( *stmt->expr->env );
                                delete stmt->expr->env;
                                stmt->expr->env = nullptr;
                        }
                }

                ResolvExpr::TypeEnvironment * compositeEnv = nullptr;
        };

        ObjectDecl * TupleAssignSpotter::Matcher::newObject( UniqueName & namer, Expression * expr ) {
                assert( expr->result && ! expr->get_result()->isVoid() );
                ObjectDecl * ret = new ObjectDecl( namer.newName(), Type::StorageClasses(), LinkageSpec::Cforall, nullptr, expr->result->clone(), new SingleInit( expr->clone() ) );
                // if expression type is a reference, don't need to construct anything, a simple initializer is sufficient.
                if ( ! dynamic_cast< ReferenceType * >( expr->result ) ) {
                        ConstructorInit * ctorInit = InitTweak::genCtorInit( ret );
                        ret->init = ctorInit;
                        ResolvExpr::resolveCtorInit( ctorInit, spotter.currentFinder.get_indexer() ); // resolve ctor/dtors for the new object
                        PassVisitor<EnvRemover> rm; // remove environments from subexpressions of StmtExprs
                        rm.pass.compositeEnv = &compositeEnv;
                        ctorInit->accept( rm );
                }
                PRINT( std::cerr << "new object: " << ret << std::endl; )
                return ret;
        }

        void TupleAssignSpotter::MassAssignMatcher::match( std::list< Expression * > &out ) {
                static UniqueName lhsNamer( "__massassign_L" );
                static UniqueName rhsNamer( "__massassign_R" );
                // empty tuple case falls into this matcher, hence the second part of the assert
                assert( (! lhs.empty() && rhs.size() <= 1) || (lhs.empty() && rhs.empty()) );

                // xxx - may need to split this up into multiple declarations, because potential conversion to references
                //  probably should not reference local variable - see MultipleAssignMatcher::match
                ObjectDecl * rtmp = rhs.size() == 1 ? newObject( rhsNamer, rhs.front().expr ) : nullptr;
                for ( ResolvExpr::Alternative & lhsAlt : lhs ) {
                        // create a temporary object for each value in the lhs and create a call involving the rhs
                        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" );

                if ( lhs.size() == rhs.size() ) {
                        // produce a new temporary object for each value in the lhs and rhs and pairwise create the calls
                        std::list< ObjectDecl * > ltmp;
                        std::list< ObjectDecl * > rtmp;
                        for ( auto p : group_iterate( lhs, rhs ) ) {
                                ResolvExpr::Alternative & lhsAlt = std::get<0>(p);
                                ResolvExpr::Alternative & rhsAlt = std::get<1>(p);
                                // convert RHS to LHS type minus one reference -- important for the case where LHS is && and RHS is lvalue, etc.
                                ReferenceType * lhsType = strict_dynamic_cast<ReferenceType *>( lhsAlt.expr->result );
                                rhsAlt.expr = new CastExpr( rhsAlt.expr, lhsType->base->clone() );
                                ObjectDecl * lobj = newObject( lhsNamer, lhsAlt.expr );
                                ObjectDecl * robj = newObject( rhsNamer, rhsAlt.expr );
                                out.push_back( createFunc(spotter.fname, lobj, robj) );
                                ltmp.push_back( lobj );
                                rtmp.push_back( robj );

                                // resolve the cast expression so that rhsAlt return type is bound by the cast type as needed, and transfer the resulting environment
                                ResolvExpr::AlternativeFinder finder{ spotter.currentFinder.get_indexer(), compositeEnv };
                                finder.findWithAdjustment( rhsAlt.expr );
                                assert( finder.get_alternatives().size() == 1 );
                                compositeEnv = std::move( finder.get_alternatives().front().env );
                        }
                        tmpDecls.splice( tmpDecls.end(), ltmp );
                        tmpDecls.splice( tmpDecls.end(), rtmp );
                }
        }
} // namespace Tuples

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