source: src/Tuples/Explode.cc @ bfc7811

//
// 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 : Rob Schluntz
// Last Modified On : Wed Nov 9 13:20:24 2016
// Update Count     : 2
//

#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() };
                                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&.
                                return new TupleIndexExpr( tupleExpr->get_tuple(), tupleExpr->get_index() );
                        }
                };
        } // 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 Tuples

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