source: src/Tuples/Explode.cc @ 42cd451e

//
// 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.
//
// Explode.cc --
//
// Author           : Rob Schluntz
// Created On       : Wed Nov 9 13:12:24 2016
// Last Modified By : Andrew Beach
// Last Modified On : Wed Jun 12 16:40:00 2016
// Update Count     : 3
//

#include "Explode.h"
#include <list>                  // for list

#include "SynTree/Mutator.h"     // for Mutator
#include "Common/PassVisitor.h"  // for PassVisitor

namespace Tuples {
        namespace {
                // remove one level of reference from a reference type -- may be useful elsewhere.
                Type * getReferenceBase( Type * t ) {
                        if ( ReferenceType * refType = dynamic_cast<ReferenceType *>( t ) ) {
                                return refType->get_base();
                        } else {
                                // for the moment, I want to know immediately if a non-reference type is ever passed in here.
                                assertf( false, "getReferenceBase for non-ref: %s", toString( refType ).c_str() );
                                return nullptr;
                        }
                }

                struct CastExploder {
                        bool castAdded = false;
                        bool foundUniqueExpr = false;
                        Expression * applyCast( Expression * expr, bool first = true ) {
                                if ( TupleExpr * tupleExpr = dynamic_cast< TupleExpr * >( expr ) ){
                                        foundUniqueExpr = true;
                                        std::list< Expression * > exprs;
                                        for ( Expression *& expr : tupleExpr->get_exprs() ) {
                                                // move cast into tuple exprs
                                                exprs.push_back( applyCast( expr, false ) );
                                        }
                                        // want the top-level expression to be cast to reference type, but not nested
                                        // tuple expressions
                                        if ( first ) {
                                                castAdded = true;
                                                Expression * tupleExpr = new TupleExpr( exprs );
                                                return new CastExpr( tupleExpr, new ReferenceType( Type::Qualifiers(), tupleExpr->result->clone() ) );
                                        } else {
                                                return new TupleExpr( exprs );
                                        }
                                }
                                if ( dynamic_cast<ReferenceType*>( expr->result ) ) {
                                        // don't need to cast reference type to another reference type
                                        return expr->clone();
                                } else {
                                        // anything else should be cast to reference as normal
                                        castAdded = true;
                                        return new CastExpr( expr->clone(), new ReferenceType( Type::Qualifiers(), expr->result->clone() ) );
                                }
                        }

                        Expression * postmutate( UniqueExpr * uniqueExpr ) {
                                // move cast into unique expr so that the unique expr has type T& rather than
                                // type T. In particular, this transformation helps with generating the
                                // correct code for reference-cast member tuple expressions, since the result
                                // should now be a tuple of references rather than a reference to a tuple.
                                // Still, this code is a bit awkward, and could use some improvement.
                                UniqueExpr * newUniqueExpr = new UniqueExpr( applyCast( uniqueExpr->get_expr() ), uniqueExpr->get_id() );
                                delete uniqueExpr;
                                if ( castAdded ) {
                                        // if a cast was added by applyCast, then unique expr now has one more layer of reference
                                        // than it had coming into this function. To ensure types still match correctly, need to cast
                                        //  to reference base so that outer expressions are still correct.
                                        castAdded = false;
                                        Type * toType = getReferenceBase( newUniqueExpr->result );
                                        return new CastExpr( newUniqueExpr, toType->clone() );
                                }
                                return newUniqueExpr;
                        }


                        Expression * postmutate( TupleIndexExpr * tupleExpr ) {
                                // tuple index expr needs to be rebuilt to ensure that the type of the
                                // field is consistent with the type of the tuple expr, since the field
                                // may have changed from type T to T&.
                                Expression * expr = tupleExpr->get_tuple();
                                tupleExpr->set_tuple( nullptr );
                                TupleIndexExpr * ret = new TupleIndexExpr( expr, tupleExpr->get_index() );
                                delete tupleExpr;
                                return ret;
                        }
                };
        } // namespace

        Expression * distributeReference( Expression * expr ) {
                PassVisitor<CastExploder> exploder;
                expr = expr->acceptMutator( exploder );
                if ( ! exploder.pass.foundUniqueExpr ) {
                        // if a UniqueExpr was found, then the cast has already been added inside the UniqueExpr as appropriate
                        expr = new CastExpr( expr, new ReferenceType( Type::Qualifiers(), expr->result->clone() ) );
                }
                return expr;
        }

namespace {

// Remove one level of reference from a reference type.
const ast::Type * getReferenceBase( const ast::Type * t ) {
        if ( const ast::ReferenceType * ref = dynamic_cast< const ast::ReferenceType * >( t ) ) {
                return ref->base;
        } else {
                assertf( false, "getReferenceBase for non-ref: %s", toString( t ).c_str() );
                return nullptr;
        }
}

struct CastExploderCore {
        bool castAdded = false;
        bool foundUniqueExpr = false;
        const ast::Expr * applyCast( const ast::Expr * expr, bool first = true ) {
                // On tuple push the cast down.
                if ( const ast::TupleExpr * tupleExpr = dynamic_cast< const ast::TupleExpr * >( expr ) ) {
                        foundUniqueExpr = true;
                        std::vector< ast::ptr< ast::Expr > > exprs;
                        for ( const ast::Expr * expr : tupleExpr->exprs ) {
                                exprs.emplace_back( applyCast( expr, false ) );
                                //exprs.emplace_back( ast::ptr< ast::Expr >( applyCast( expr, false ) ) );
                        }
                        if ( first ) {
                                castAdded = true;
                                const ast::Expr * tuple = new ast::TupleExpr{
                                        tupleExpr->location, std::move( exprs ) };
                                return new ast::CastExpr{ tuple, new ast::ReferenceType{ tuple->result } };
                        } else {
                                return new ast::TupleExpr( tupleExpr->location, std::move( exprs ) );
                        }
                }
                if ( dynamic_cast< const ast::ReferenceType * >( expr->result.get() ) ) {
                        return expr;
                } else {
                        castAdded = true;
                        return new ast::CastExpr{ expr, new ast::ReferenceType{ expr->result } };
                }
        }

        const ast::Expr * postmutate( const ast::UniqueExpr * node ) {
                // move cast into unique expr so that the unique expr has type T& rather than
                // type T. In particular, this transformation helps with generating the
                // correct code for reference-cast member tuple expressions, since the result
                // should now be a tuple of references rather than a reference to a tuple.
                // Still, this code is a bit awkward, and could use some improvement.
                const ast::UniqueExpr * newNode = new ast::UniqueExpr( node->location,
                                applyCast( node->expr ), node->id );
                if ( castAdded ) {
                        // if a cast was added by applyCast, then unique expr now has one more layer of reference
                        // than it had coming into this function. To ensure types still match correctly, need to cast
                        //  to reference base so that outer expressions are still correct.
                        castAdded = false;
                        const ast::Type * newType = getReferenceBase( newNode->result );
                        return new ast::CastExpr{ newNode->location, node, newType };
                }
                return newNode;
        }

        const ast::Expr * postmutate( const ast::TupleIndexExpr * tupleExpr ) {
                // tuple index expr needs to be rebuilt to ensure that the type of the
                // field is consistent with the type of the tuple expr, since the field
                // may have changed from type T to T&.
                return new ast::TupleIndexExpr( tupleExpr->location, tupleExpr->tuple, tupleExpr->index );
        }
};

} // namespace

const ast::Expr * distributeReference( const ast::Expr * expr ) {
        ast::Pass<CastExploderCore> exploder;
        expr = expr->accept( exploder );
        if ( ! exploder.pass.foundUniqueExpr ) {
                expr = new ast::CastExpr{ expr, new ast::ReferenceType{ expr->result } };
        }
        return expr;
}

} // namespace Tuples

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