source: src/GenPoly/Lvalue.cc @ 9a34b5a

//
// 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.
//
// Lvalue.cc --
//
// Author           : Richard C. Bilson
// Created On       : Mon May 18 07:44:20 2015
// Last Modified By : Peter A. Buhr
// Last Modified On : Fri Mar 17 09:11:18 2017
// Update Count     : 5
//

#include <cassert>

#include "Lvalue.h"

#include "GenPoly.h"

#include "SynTree/Declaration.h"
#include "SynTree/Type.h"
#include "SynTree/Expression.h"
#include "SynTree/Statement.h"
#include "SynTree/Visitor.h"
#include "SynTree/Mutator.h"
#include "SymTab/Indexer.h"
#include "SymTab/Autogen.h"
#include "ResolvExpr/Resolver.h"
#include "ResolvExpr/typeops.h"

#include "Common/UniqueName.h"
#include "Common/utility.h"
#include "InitTweak/InitTweak.h"

#include "Common/PassVisitor.h"

// need to be careful about polymorphic references... e.g. in *? (___operator_deref__A0_1_0_0__Fd0_Pd0_intrinsic___1)
// the variable is automatically dereferenced and this causes errors dereferencing void*.

namespace GenPoly {
        namespace {
                // TODO: fold this into the general createDeref function??
                Expression * mkDeref( Expression * arg ) {
                        if ( SymTab::dereferenceOperator ) {
                                VariableExpr * deref = new VariableExpr( SymTab::dereferenceOperator );
                                deref->set_result( new PointerType( Type::Qualifiers(), deref->get_result() ) );
                                Type * base = InitTweak::getPointerBase( arg->get_result() );
                                assertf( base, "expected pointer type in dereference (type was %s)", toString( arg->get_result() ).c_str() );
                                ApplicationExpr * ret = new ApplicationExpr( deref, { arg } );
                                delete ret->get_result();
                                ret->set_result( new ReferenceType( Type::Qualifiers(), base->clone() ) );
                                return ret;
                        } else {
                                return UntypedExpr::createDeref( arg );
                        }
                }

                struct ReferenceConversions final {
                        Expression * postmutate( CastExpr * castExpr );
                };

                /// Intrinsic functions that take reference parameters don't REALLY take reference parameters -- their reference arguments must always be implicitly dereferenced.
                struct FixIntrinsicArgs final {
                        Expression * postmutate( ApplicationExpr *appExpr );
                };


                /// Replace reference types with pointer types
                struct ReferenceTypeElimination final {
                        Type * postmutate( ReferenceType * refType );
                };

                /// GCC-like Generalized Lvalues (which have since been removed from GCC)
                /// https://gcc.gnu.org/onlinedocs/gcc-3.4.6/gcc/Lvalues.html#Lvalues
                /// Replaces &(a,b) with (a, &b), &(a ? b : c) with (a ? &b : &c)
                struct GeneralizedLvalue final {
                        Expression * postmutate( AddressExpr * addressExpr );
                };
        } // namespace

        void convertLvalue( std::list< Declaration* >& translationUnit ) {
                std::cerr << "convertLvalue" << std::endl;
                PassVisitor<ReferenceConversions> refCvt;
                PassVisitor<ReferenceTypeElimination> elim;
                PassVisitor<GeneralizedLvalue> genLval;
                PassVisitor<FixIntrinsicArgs> fixer;
                mutateAll( translationUnit, refCvt );
                mutateAll( translationUnit, fixer );
                mutateAll( translationUnit, elim );
                mutateAll( translationUnit, genLval );
        }

        namespace {
                Type* isLvalueRet( FunctionType *function ) {
                        if ( function->get_returnVals().empty() ) return 0;
                        Type *ty = function->get_returnVals().front()->get_type();
                        return dynamic_cast< ReferenceType * >( ty ) ;
                }

                bool isIntrinsicApp( ApplicationExpr *appExpr ) {
                        if ( VariableExpr *varExpr = dynamic_cast< VariableExpr* >( appExpr->get_function() ) ) {
                                return varExpr->get_var()->get_linkage() == LinkageSpec::Intrinsic;
                        } else {
                                return false;
                        } // if
                }

                bool isDeref( Expression * expr ) {
                        if ( UntypedExpr * untyped = dynamic_cast< UntypedExpr * >( expr ) ) {
                                return InitTweak::getFunctionName( untyped ) == "*?";
                        } else if ( ApplicationExpr * appExpr = dynamic_cast< ApplicationExpr * > ( expr ) ) {
                                if ( DeclarationWithType * func = InitTweak::getFunction( appExpr ) ) {
                                        return func->get_linkage() == LinkageSpec::Intrinsic && InitTweak::getFunctionName( appExpr ) == "*?";
                                }
                        }
                        return false;
                }

                bool isIntrinsicReference( Expression * expr ) {
                        if ( isDeref( expr ) ) return true;
                        else if ( UntypedExpr * untyped = dynamic_cast< UntypedExpr * >( expr ) ) {
                                return InitTweak::getFunctionName( untyped ) == "?[?]";
                        } else if ( ApplicationExpr * appExpr = dynamic_cast< ApplicationExpr * > ( expr ) ) {
                                if ( DeclarationWithType * func = InitTweak::getFunction( appExpr ) ) {
                                        return func->get_linkage() == LinkageSpec::Intrinsic && InitTweak::getFunctionName( appExpr ) == "?[?]";
                                }
                        }
                        return false;
                }

                void fixArg( Expression *& arg, Type * formal ) {
                        if ( dynamic_cast<ReferenceType*>( formal ) ) {
                                // if the parameter is a reference, add a dereference to the reference-typed argument.
                                Type * baseType = InitTweak::getPointerBase( arg->get_result() );
                                assertf( baseType, "parameter is reference, arg must be pointer or reference: %s", toString( arg->get_result() ) );
                                PointerType * ptrType = new PointerType( Type::Qualifiers(), baseType->clone() );
                                delete arg->get_result();
                                arg->set_result( ptrType );
                                arg = mkDeref( new CastExpr( arg, arg->get_result()->clone() ) );
                        }
                }

                Expression * FixIntrinsicArgs::postmutate( ApplicationExpr * appExpr ) {
                        // intrinsic functions don't really take reference-typed parameters, so they require an implicit dereference on their arguments.
                        if ( DeclarationWithType * function = InitTweak::getFunction( appExpr ) ) {
                                if ( function->get_linkage() == LinkageSpec::Intrinsic ) {
                                        FunctionType * ftype = GenPoly::getFunctionType( function->get_type() );
                                        assertf( ftype, "Function declaration does not have function type." );
                                        for ( auto p : group_iterate( appExpr->get_args(), ftype->get_parameters() ) ) {
                                                Expression *& arg = std::get<0>( p );
                                                DeclarationWithType * formal = std::get<1>( p );
                                                std::cerr << "pair<0>: " << arg << std::endl;
                                                std::cerr << "pair<1>: " << formal->get_type() << std::endl;
                                                if ( isIntrinsicReference( arg ) ) { // intrinsic functions that turn pointers into references
                                                        // if argument is dereference or array subscript, the result isn't REALLY a reference, so it's not necessary to fix the argument
                                                        std::cerr << "skipping intrinsic reference" << std::endl;
                                                        continue;
                                                } else {
                                                        fixArg( arg, formal->get_type() );
                                                }
                                        }
                                }
                        }
                        return appExpr;
                }

                Expression * ReferenceConversions::postmutate( CastExpr * castExpr ) {
                        // xxx - is it possible to convert directly between reference types with a different base? E.g.,
                        //   int x;
                        //   (double&)x;
                        // At the moment, I am working off of the assumption that this is illegal, thus the cast becomes redundant
                        // after this pass, so trash the cast altogether. If that changes, care must be taken to insert the correct
                        // pointer casts in the right places.

                        // conversion to reference type
                        if ( ReferenceType * refType = dynamic_cast< ReferenceType * >( castExpr->get_result() ) ) {
                                (void)refType;
                                if ( ReferenceType * otherRef = dynamic_cast< ReferenceType * >( castExpr->get_arg()->get_result() ) ) {
                                        // nothing to do if casting from reference to reference.
                                        (void)otherRef;
                                        std::cerr << "convert reference to reference -- nop" << std::endl;
                                        if ( isIntrinsicReference( castExpr->get_arg() ) ) {
                                                Expression * callExpr = castExpr->get_arg();
                                                std::cerr << "but arg is deref -- &" << std::endl;
                                                std::cerr << callExpr << std::endl;
                                                // move environment out to new top-level
                                                callExpr->set_env( castExpr->get_env() );
                                                castExpr->set_arg( nullptr );
                                                castExpr->set_env( nullptr );
                                                delete castExpr;
                                                return callExpr;
                                        }
                                        assertf( false, "non-intrinsic reference with cast of reference to reference not yet supported: ", toString( castExpr ) );
                                        std::cerr << castExpr << std::endl;
                                        return castExpr;
                                } else if ( castExpr->get_arg()->get_result()->get_lvalue() ) {
                                        // conversion from lvalue to reference
                                        // xxx - keep cast, but turn into pointer cast??
                                        // xxx - memory
                                        std::cerr << "convert lvalue to reference -- &" << std::endl;
                                        std::cerr << castExpr->get_arg() << std::endl;
                                        Expression * ret = new AddressExpr( castExpr->get_arg() );
                                        ret->set_env( castExpr->get_env() );
                                        castExpr->set_env( nullptr );
                                        castExpr->set_arg( nullptr );
                                        delete castExpr;
                                        return ret;
                                } else {
                                        // rvalue to reference conversion -- introduce temporary
                                }
                                assertf( false, "Only conversions to reference from lvalue are currently supported: %s", toString( castExpr ).c_str() );
                        } else if ( ReferenceType * refType = dynamic_cast< ReferenceType * >( castExpr->get_arg()->get_result() ) ) {
                                // conversion from reference to rvalue
                                // should be easy, just need to move deref code up here?
                                std::cerr << "convert reference to rvalue -- *" << std::endl;
                                if ( isIntrinsicReference( castExpr->get_arg() ) ) {
                                        std::cerr << "but arg is intrinsic reference -- nop" << std::endl;
                                        return castExpr;
                                }
                                std::cerr << "was = " << castExpr << std::endl;

                                Expression * deref = mkDeref( castExpr->get_arg() );
                                deref->set_env( castExpr->get_env() );
                                castExpr->set_arg( nullptr );
                                castExpr->set_env( nullptr );
                                delete castExpr;
                                std::cerr << "now: " << deref << std::endl;
                                return deref;
                        }
                        return castExpr;
                }

                Type * ReferenceTypeElimination::postmutate( ReferenceType * refType ) {
                        Type * base = refType->get_base();
                        refType->set_base( nullptr );
                        delete refType;
                        return new PointerType( Type::Qualifiers(), base );
                }

                Expression * GeneralizedLvalue::postmutate( AddressExpr * addrExpr ) {
                        if ( CommaExpr * commaExpr = dynamic_cast< CommaExpr * >( addrExpr->get_arg() ) ) {
                                Expression * arg1 = commaExpr->get_arg1()->clone();
                                Expression * arg2 = commaExpr->get_arg2()->clone();
                                delete addrExpr;
                                return new CommaExpr( arg1, new AddressExpr( arg2 ) );
                        } else if ( ConditionalExpr * condExpr = dynamic_cast< ConditionalExpr * >( addrExpr->get_arg() ) ) {
                                Expression * arg1 = condExpr->get_arg1()->clone();
                                Expression * arg2 = condExpr->get_arg2()->clone();
                                Expression * arg3 = condExpr->get_arg3()->clone();
                                delete addrExpr;
                                return new ConditionalExpr( arg1, new AddressExpr( arg2 ), new AddressExpr( arg3 ) );
                        }
                        return addrExpr;
                }
        } // namespace
} // namespace GenPoly

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