source: src/GenPoly/Lvalue.cpp @ b6f2e7ab

//
// 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.cpp -- Clean up lvalues and remove references.
//
// Author           : Andrew Beach
// Created On       : Thu Sep 15 14:08:00 2022
// Last Modified By : Andrew Beach
// Last Modified On : Mon Aug 12 18:07:00 2024
// Update Count     : 1
//

#include "Lvalue.hpp"

#include <set>
#include <iostream>

#include "AST/Copy.hpp"                // for deepCopy
#include "AST/Expr.hpp"
#include "AST/Inspect.hpp"
#include "AST/LinkageSpec.hpp"         // for Linkage
#include "AST/Pass.hpp"
#include "Common/SemanticError.hpp"    // for SemanticWarning
#include "Common/ToString.hpp"         // for toCString
#include "Common/UniqueName.hpp"       // for UniqueName
#include "GenPoly/GenPoly.hpp"         // for genFunctionType
#include "ResolvExpr/Typeops.hpp"      // for typesCompatible
#include "ResolvExpr/Unify.hpp"        // for unify

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

namespace GenPoly {

namespace {

/// Intrinsic functions that return references now instead return lvalues.
struct FixIntrinsicResults final : public ast::WithGuards {
        enum {
                NoSkip,
                Skip,
                SkipInProgress,
        } skip = NoSkip;

        void previsit( ast::AsmExpr const * ) {
                GuardValue( skip ) = Skip;
        }
        void previsit( ast::ApplicationExpr const * ) {
                GuardValue( skip ) = (skip == Skip) ? SkipInProgress : NoSkip;
        }

        ast::Expr const * postvisit( ast::ApplicationExpr const * expr );
        void previsit( ast::FunctionDecl const * decl );
        bool inIntrinsic = false;
};

/// Add de-references around address-of operations on reference types.
struct AddressRef final :
                public ast::WithConstTranslationUnit,
                public ast::WithGuards,
                public ast::WithShortCircuiting,
                public ast::WithVisitorRef<AddressRef> {
        void previsit( ast::AddressExpr const * expr );
        ast::Expr const * postvisit( ast::AddressExpr const * expr );
        void previsit( ast::Expr const * expr );
        ast::ApplicationExpr const * previsit( ast::ApplicationExpr const * expr );
        void previsit( ast::SingleInit const * init );

        void handleNonAddr( ast::Expr const * expr );

        bool first = true;
        bool current = false;
        bool addCast = false;
        int refDepth = 0;
};

/// Handles casts between references and pointers,
/// creating temporaries for the conversion.
struct ReferenceConversions final :
                public ast::WithConstTranslationUnit,
                public ast::WithGuards, public ast::WithStmtsToAdd<> {
        ast::Expr const * postvisit( ast::CastExpr const * expr );
        ast::Expr const * postvisit( ast::AddressExpr const * expr );
};

/// Intrinsic functions that take reference parameters don't actually do.
/// Their reference arguments must be implicity dereferenced.
/// TODO Also appears to contain redundent code with AddressRef
struct FixIntrinsicArgs final :
                public ast::WithConstTranslationUnit {
        ast::Expr const * postvisit( ast::ApplicationExpr const * expr );
};

/// Removes redundant &* / *& patterns that may be generated.
struct CollapseAddressDeref final {
        ast::Expr const * postvisit( ast::AddressExpr const * expr );
        ast::Expr const * postvisit( ast::ApplicationExpr const * expr );
};

/// 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 :
                public ast::WithVisitorRef<GeneralizedLvalue> {
        ast::Expr const * postvisit( ast::AddressExpr const * expr );
        ast::Expr const * postvisit( ast::MemberExpr const * expr );

        template<typename Node, typename Func>
        ast::Expr const * applyTransformation(
              Node const * expr, ast::ptr<ast::Expr> Node::*field, Func mkExpr );
};

/// Replace all reference types with pointer types.
struct ReferenceTypeElimination final {
        ast::SizeofExpr const * previsit( ast::SizeofExpr const * expr );
        ast::AlignofExpr const * previsit( ast::AlignofExpr const * expr );
        ast::Type const * postvisit( ast::ReferenceType const * type );
};

/// True for intrinsic function calls that return an lvalue in C.
bool isIntrinsicReference( ast::Expr const * expr ) {
        // The known intrinsic-reference prelude functions.
        static std::set<std::string> const lvalueFunctions = { "*?", "?[?]" };
        if ( auto untyped = dynamic_cast<ast::UntypedExpr const *>( expr ) ) {
                std::string fname = ast::getFunctionName( untyped );
                return lvalueFunctions.count( fname );
        } else if ( auto app = dynamic_cast<ast::ApplicationExpr const *>( expr ) ) {
                if ( auto func = ast::getFunction( app ) ) {
                        return func->linkage == ast::Linkage::Intrinsic
                                && lvalueFunctions.count( func->name );
                }
        }
        return false;
}

// A maybe typed variant of the createDeref function (only UntypedExpr).
ast::Expr * mkDeref(
                ast::TranslationGlobal const & global, ast::Expr const * arg ) {
        if ( global.dereference ) {
                // Note: Reference depth can be arbitrarily deep here,
                // so peel off the outermost pointer/reference, not just
                // pointer because they are effecitvely equivalent in this pass
                ast::VariableExpr * deref = new ast::VariableExpr(
                        arg->location, global.dereference );
                deref->result = new ast::PointerType( deref->result );
                ast::Type const * base = ast::getPointerBase( arg->result );
                assertf( base, "expected pointer type in dereference (type was %s)", toString( arg->result ).c_str() );
                ast::ApplicationExpr * ret =
                        new ast::ApplicationExpr( arg->location, deref, { arg } );
                ret->result = ast::deepCopy( base );
                return ret;
        } else {
                return ast::UntypedExpr::createDeref( arg->location, arg );
        }
}

ast::Expr const * FixIntrinsicResults::postvisit(
                ast::ApplicationExpr const * expr ) {

        if ( skip == SkipInProgress || !isIntrinsicReference( expr ) ) {
                return expr;
        }
        // Eliminate reference types from intrinsic applications
        // now they return lvalues.
        ast::ptr<ast::ReferenceType> result =
                        expr->result.strict_as<ast::ReferenceType>();
        expr = ast::mutate_field( expr, &ast::ApplicationExpr::result,
                        ast::deepCopy( result->base ) );
        if ( inIntrinsic ) {
                return expr;
        }
        // When not in an intrinsic function, add a cast to don't add cast when
        // in an intrinsic function, since they already have the cast.
        auto * ret = new ast::CastExpr( expr->location, expr, result.get() );
        ret->env = expr->env;
        return ret;
}

void FixIntrinsicResults::previsit( ast::FunctionDecl const * decl ) {
        GuardValue( inIntrinsic ) = decl->linkage == ast::Linkage::Intrinsic;
}

void AddressRef::previsit( ast::AddressExpr const * ) {
        // Is this the first address-of in the chain?
        GuardValue( current ) = first;
        // Later references will not be for next address-of to be first in chain.
        GuardValue( first ) = false;
        // If is the outermost address-of in a chain:
        if ( current ) {
                // Set depth to 0 so that postvisit can
                // find the innermost address-of easily.
                GuardValue( refDepth ) = 0;
        }
}

ast::Expr const * AddressRef::postvisit( ast::AddressExpr const * expr ) {
        PRINT( std::cerr << "addr ref at " << expr << std::endl; )
        if ( 0 == refDepth ) {
                PRINT( std::cerr << "depth 0, get new depth..." << std::endl; )
                // Is this the innermost address-of in a chain? record depth D.
                if ( isIntrinsicReference( expr->arg ) ) {
                        assertf( false, "AddrRef : address-of should not have intrinsic reference argument: %s", toCString( expr->arg )  );
                } else {
                        // try to avoid ?[?]
                        // TODO is this condition still necessary? intrinsicReferences
                        // should have a cast around them at this point, so I don't think
                        // this condition ever fires.
                        refDepth = expr->arg->result->referenceDepth();
                        PRINT( std::cerr << "arg not intrinsic reference, new depth is: " << refDepth << std::endl; )
                }
        }
        if ( current ) {
                PRINT( std::cerr << "current, depth is: " << refDepth << std::endl; )
                ast::Expr const * ret = expr;
                while ( refDepth ) {
                        // Add one dereference for each address-of in the chain.
                        ret = mkDeref( transUnit().global, ret );
                        --refDepth;
                }

                // if addrExpr depth is 0, then the result is a pointer because the
                // arg was depth 1 and not lvalue. This means the dereference result
                // is not a reference, is lvalue, and one less pointer depth than the
                // addrExpr. Thus the cast is meaningless.
                // TODO: One thing to double check is whether it is possible for the
                // types to differ outside of the single pointer level (i.e. can the
                // base type of addrExpr differ from the type of addrExpr-arg?). If
                // so then the cast might need to be added, conditional on a more
                // sophisticated check.
                if ( addCast && 0 != expr->result->referenceDepth() ) {
                        PRINT( std::cerr << "adding cast to " << expr->result << std::endl; )
                        return new ast::CastExpr( expr->location,
                                ret, ast::deepCopy( expr->result ) );
                }
                return ret;
        }
        PRINT( std::cerr << "not current..." << std::endl; )
        return expr;
}

void AddressRef::previsit( ast::Expr const * expr ) {
        handleNonAddr( expr );
        GuardValue( addCast ) = false;
}

// So we want to skip traversing to the head?
ast::ApplicationExpr const * AddressRef::previsit(
                ast::ApplicationExpr const * expr ) {
        visit_children = false;
        GuardValue( addCast );
        handleNonAddr( expr );
        auto mutExpr = ast::mutate( expr );
        for ( ast::ptr<ast::Expr> & arg : mutExpr->args ) {
                addCast = true;
                arg = arg->accept( *visitor );
        }
        return mutExpr;
}

void AddressRef::previsit( ast::SingleInit const * ) {
        // Each initialization context with address-of requires a cast.
        GuardValue( addCast ) = true;
}

// idea: &&&E: get outer &, inner &
// at inner &, record depth D of reference type of argument of &.
// at auter &, add D derefs.
void AddressRef::handleNonAddr( ast::Expr const * ) {
        // non-address-of: reset status variables:
        // * current expr is NOT the first address-of expr in an address-of chain.
        // * next seen address-of expr IS the first in the chain.
        GuardValue( current ) = false;
        GuardValue( first ) = true;
}

ast::Expr const * ReferenceConversions::postvisit(
                ast::CastExpr const * expr ) {
        // TODO: Is it possible to convert directly between reference types with
        // a different base. e.g.
        //   int x;
        //   (double&)x;
        // At the moment, I (who?) 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.

        // Note: reference depth difference is the determining factor in what
        // code is run, rather than whether something is reference type or not,
        // since conversion still needs to occur when both types are references
        // that differ in depth.
        ast::Type const * dstType = expr->result.get();
        ast::Type const * srcType = expr->arg->result.get();
        assertf( dstType, "Cast to no type in: %s", toCString( expr ) );
        assertf( srcType, "Cast from no type in: %s", toCString( expr ) );
        int dstDepth = dstType->referenceDepth();
        int srcDepth = srcType->referenceDepth();
        int diff = dstDepth - srcDepth;

        if ( 0 < diff && !expr->arg->get_lvalue() ) {
                // rvalue to reference conversion -- introduce temporary
                // know that reference depth of cast argument is 0
                //   (int &&&)3;
                // becomes
                //   int __ref_tmp_0 = 3;
                //   int & __ref_tmp_1 = &__ref_tmp_0;
                //   int && __ref_tmp_2 = &__ref_tmp_1;
                //   &__ref_tmp_2;
                // The last & comes from the remaining reference conversion code.
                SemanticWarning( expr->arg->location,
                        Warning::RvalueToReferenceConversion, toCString( expr->arg ) );

                static UniqueName tmpNamer( "__ref_tmp_" );
                ast::ObjectDecl * tmp = new ast::ObjectDecl( expr->arg->location,
                        tmpNamer.newName(),
                        ast::deepCopy( expr->arg->result ),
                        new ast::SingleInit( expr->arg->location, expr->arg ) );
                PRINT( std::cerr << "make tmp: " << tmp << std::endl; )
                stmtsToAddBefore.push_back( new ast::DeclStmt( tmp->location, tmp ) );
                for ( int i = 0 ; i < dstDepth - 1 ; ++i ) {
                        ast::ObjectDecl * newTmp = new ast::ObjectDecl( tmp->location,
                                tmpNamer.newName(),
                                new ast::ReferenceType( ast::deepCopy( tmp->type ) ),
                                new ast::SingleInit( tmp->location,
                                        new ast::AddressExpr( tmp->location,
                                                new ast::VariableExpr( tmp->location, tmp ) ) ) );
                        PRINT( std::cerr << "make tmp: " << i << ": " << newTmp << std::endl; )
                        stmtsToAddBefore.push_back(
                                new ast::DeclStmt( newTmp->location, newTmp ) );
                        tmp = newTmp;
                }
                // Update diff so that remaining code works out correctly.
                expr = ast::mutate_field( expr, &ast::CastExpr::arg,
                        new ast::VariableExpr( tmp->location, tmp ) );
                PRINT( std::cerr << "update cast to: " << expr << std::endl; )
                srcType = expr->arg->result;
                srcDepth = srcType->referenceDepth();
                diff = dstDepth - srcDepth;
                assert( 1 == diff );
        }

        // Handle conversion between different depths.
        PRINT(
                if ( dstDepth || srcDepth ) {
                        std::cerr << "dstType: " << dstType << " / srcType: " << srcType << '\n';
                        std::cerr << "depth: " << dstDepth << " / " << srcDepth << std::endl;
                }
        )
        // Conversion to type with more depth/more references.
        // Add address-of for each level of difference.
        if ( 0 < diff ) {
                ast::Expr * ret = ast::mutate( expr->arg.get() );
                for ( int i = 0 ; i < diff ; ++i ) {
                        ret = new ast::AddressExpr( ret->location, ret );
                }
                if ( expr->arg->get_lvalue() &&
                                !ResolvExpr::typesCompatible(
                                        srcType,
                                        strict_dynamic_cast<ast::ReferenceType const *>( dstType )->base ) ) {
                        // Must keep cast if cast-to type is different from the actual type.
                        return ast::mutate_field( expr, &ast::CastExpr::arg, ret );
                }
                ret->env = expr->env;
                ret->result = expr->result;
                return ret;
        // Conversion to type with less depth/fewer references.
        // Add dereferences for each level of difference.
        } else if ( diff < 0 ) {
                ast::Expr * ret = ast::mutate( expr->arg.get() );
                for ( int i = 0 ; i < -diff ; ++i ) {
                        ret = mkDeref( transUnit().global, ret );
                }
                // Must keep cast if types are different.
                if ( !ResolvExpr::typesCompatibleIgnoreQualifiers(
                                dstType->stripReferences(),
                                srcType->stripReferences() ) ) {
                        return ast::mutate_field( expr, &ast::CastExpr::arg, ret );
                }
                ret->env = expr->env;
                ret->result = expr->result;
                // The result must be an lvalue.
                assert( ret->get_lvalue() );
                return ret;
        // Conversion with the same depth.
        } else {
                assert( 0 == diff );
                // Remove useless generated casts.
                if ( expr->isGenerated == ast::GeneratedFlag::GeneratedCast &&
                                ResolvExpr::typesCompatible(
                                        expr->result,
                                        expr->arg->result ) ) {
                        PRINT(
                                std::cerr << "types are compatible, removing cast: " << expr << '\n';
                                std::cerr << "-- " << expr->result << '\n';
                                std::cerr << "-- " << expr->arg->result << std::endl;
                        )
                        auto argAsEnum = expr->arg.as<ast::EnumInstType>();
                        auto resultAsEnum = expr->result.as<ast::EnumInstType>();
                        if (argAsEnum && resultAsEnum) {
                                if (argAsEnum->base->name != resultAsEnum->base->name) {
                                        return expr;
                                }
                        }
                        return ast::mutate_field( expr->arg.get(),
                                        &ast::Expr::env, expr->env.get() );
                }
                return expr;
        }
}

ast::Expr const * ReferenceConversions::postvisit(
                ast::AddressExpr const * expr ) {
        // Inner expression may have been lvalue to reference conversion, which
        // becomes an address expression. In this case, remove the outer address
        // expression and return the argument.
        // TODO: It's possible that this might catch too much and require a more
        // sophisticated check. TODO What check are we talking about here?
        return expr;
}

ast::Expr const * FixIntrinsicArgs::postvisit(
                ast::ApplicationExpr const * expr ) {
        // Intrinsic functions don't really take reference-typed parameters,
        // so they require an implicit dereference on their arguments.
        auto function = ast::getFunction( expr );
        if ( function == nullptr ) {
                return expr;
        }

        ast::FunctionType const * ftype = GenPoly::getFunctionType( function->get_type() );
        assertf( ftype, "Function declaration does not have function type." );
        // Can be of different lengths only when function is variadic.
        assertf( ftype->params.size() == expr->args.size() || ftype->isVarArgs,
                "ApplicationExpr args do not match formal parameter type." );
        assertf( ftype->params.size() <= expr->args.size(),
                "Cannot have more parameters than arguments." );

        unsigned int i = 0;
        unsigned int const end = ftype->params.size();

        // This is used to make sure we get a zip on shortests.
        if ( end == i ) return expr;

        // This mutate could be redundent, but it is simpler this way.
        auto mutExpr = ast::mutate( expr );

        for ( auto pair : unsafe_group_iterate( mutExpr->args, ftype->params ) ) {
                ast::ptr<ast::Expr> & arg = std::get<0>( pair );
                ast::ptr<ast::Type> const & formal = std::get<1>( pair );
                PRINT(
                        std::cerr << "pair<0>: " << arg.get() << std::endl;
                        std::cerr << " -- " << arg->result << std::endl;
                        std::cerr << "pair<1>: " << formal << std::endl;
                )
                //if ( dynamic_cast<ast::ReferenceType const *>( formal.get() ) ) {
                if ( formal.as<ast::ReferenceType>() ) {
                        PRINT( std::cerr << "===formal is reference" << std::endl; )
                        // TODO: It's likely that the second condition should be
                        // `... && ! isIntrinsicReference( arg )`, but this requires
                        // investigation.

                        if ( ast::Linkage::Intrinsic != function->linkage
                                        && isIntrinsicReference( arg ) ) {
                                // Needed for definition of prelude functions, etc.
                                // If argument is dereference or array subscript, the result
                                // isn't REALLY a reference, but non-intrinsic functions
                                // expect a reference: take address

                                // TODO: OK, so this should be cut?!
                                // NODE: Previously, this condition fixed
                                //   void f(int *&);
                                //   int & x = ...;
                                //   f(&x);
                                // But now this is taken care of by a reference cast added by
                                // AddressRef. Need to find a new example or remove this
                                // branch.
                                PRINT(
                                        std::cerr << "===is intrinsic arg in non-intrinsic call - adding address" << std::endl;
                                )
                                arg = new ast::AddressExpr( arg->location, arg );
                        } else if ( ast::Linkage::Intrinsic == function->linkage
                                        && arg->result->referenceDepth() != 0 ) {
                                // Argument is a 'real' reference, but function expects a C
                                // lvalue: Add a dereference to the reference-typed argument.
                                PRINT(
                                        std::cerr << "===is non-intrinsic arg in intrinsic call - adding deref to arg" << std::endl;
                                )
                                ast::Type const * base = ast::getPointerBase( arg->result );
                                assertf( base, "parameter is reference, arg must be pointer or reference: %s", toString( arg->result ).c_str() );
                                ast::PointerType * ptr = new ast::PointerType( ast::deepCopy( base ) );
                                arg = ast::mutate_field( arg.get(),
                                                &ast::ApplicationExpr::result, ptr );
                                arg = mkDeref( transUnit().global, arg );
                        }
                }
                ++i;
                if ( end == i ) break;
        }
        return mutExpr;
}

ast::Expr const * CollapseAddressDeref::postvisit(
                ast::AddressExpr const * expr ) {
        ast::Expr const * arg = expr->arg;
        if ( isIntrinsicReference( arg ) ) {
                std::string fname = ast::getFunctionName( arg );
                if ( fname == "*?" ) {
                        ast::Expr const * arg0 = ast::getCallArg( arg, 0 );
                        ast::Expr * ret = ast::mutate( arg0 );
                        ret->env = expr->env;
                        return ret;
                }
        } else if ( auto cast = dynamic_cast<ast::CastExpr const *>( arg ) ) {
                // Need to move cast to pointer type out a level since address of
                // pointer is not valid C code (can be introduced in prior passes,
                // e.g., InstantiateGeneric)
                if ( ast::getPointerBase( cast->result ) ) {
                        auto mutExpr = ast::mutate( expr );
                        auto mutCast = strict_dynamic_cast<ast::CastExpr *>(
                                        ast::mutate( mutExpr->arg.release() ) );
                        mutExpr->arg = mutCast->arg;
                        mutCast->arg = mutExpr;
                        mutCast->result = new ast::PointerType( mutCast->result );
                        return mutCast;
                }
        }
        return expr;
}

ast::Expr const * CollapseAddressDeref::postvisit(
                ast::ApplicationExpr const * expr ) {
        if ( isIntrinsicReference( expr ) ) {
                std::string fname = ast::getFunctionName( expr );
                if ( fname == "*?" ) {
                        assert( 1 == expr->args.size() );
                        ast::Expr const * arg = ast::getCallArg( expr, 0 );
                        // xxx - this isn't right, because it can remove casts that
                        // should be there...
                        //      while ( auto cast = dynamic_cast< ast::CastExpr const * >( arg ) ) {
                        //              arg = cast->arg;
                        //      }
                        if ( auto addr = dynamic_cast<ast::AddressExpr const *>( arg ) ) {
                                return ast::mutate_field( addr->arg.get(),
                                                &ast::Expr::env, expr->env.get() );
                        }
                }
        }
        return expr;
}

ast::Expr const * GeneralizedLvalue::postvisit(
                ast::AddressExpr const * expr ) {
        return applyTransformation( expr, &ast::AddressExpr::arg,
                []( ast::Expr const * arg ) {
                        return new ast::AddressExpr( arg->location, arg );
                }
        );
}

ast::Expr const * GeneralizedLvalue::postvisit(
                ast::MemberExpr const * expr ) {
        return applyTransformation( expr, &ast::MemberExpr::aggregate,
                [expr]( ast::Expr const * aggr ) {
                        return new ast::MemberExpr( aggr->location, expr->member, aggr );
                }
        );
}

template<typename Node, typename Func>
ast::Expr const * GeneralizedLvalue::applyTransformation(
                Node const * expr, ast::ptr<ast::Expr> Node::*field, Func mkExpr ) {
        ast::ptr<ast::Expr> const & arg = expr->*field;
        if ( auto commaArg = arg.as<ast::CommaExpr>() ) {
                ast::Expr const * arg1 = ast::deepCopy( commaArg->arg1 );
                ast::Expr const * arg2 = ast::deepCopy( commaArg->arg2 );
                ast::Expr const * ret = new ast::CommaExpr(
                        commaArg->location, arg1, mkExpr( arg2 )->accept( *visitor ) );
                return ret;
        } else if ( auto condArg = arg.as<ast::ConditionalExpr>() ) {
                ast::Expr const * arg1 = ast::deepCopy( condArg->arg1 );
                ast::Expr const * arg2 = ast::deepCopy( condArg->arg2 );
                ast::Expr const * arg3 = ast::deepCopy( condArg->arg3 );
                ast::ConditionalExpr * ret = new ast::ConditionalExpr(
                        condArg->location, arg1, mkExpr( arg2 )->accept( *visitor ),
                        mkExpr( arg3 )->accept( *visitor ) );

                // Conditional expr type may not be either of the arguments,
                // so unify to get the result.
                // TODO: Maybe I could create a wrapper for this.
                ast::ptr<ast::Type> common = nullptr;
                ast::TypeEnvironment newEnv;
                ast::AssertionSet needAssertions, haveAssertions;
                ast::OpenVarSet openVars;
                ResolvExpr::unify( ret->arg2->result, ret->arg3->result, newEnv,
                        needAssertions, haveAssertions, openVars, common );
                ret->result = common ? common : ast::deepCopy( ret->arg2->result );
                return ret;
        }
        return expr;
}

ast::SizeofExpr const * ReferenceTypeElimination::previsit(
                ast::SizeofExpr const * expr ) {
        return ast::mutate_field( expr, &ast::SizeofExpr::type,
                expr->type->stripReferences() );
}

ast::AlignofExpr const * ReferenceTypeElimination::previsit(
                ast::AlignofExpr const * expr ) {
        return ast::mutate_field( expr, &ast::AlignofExpr::type,
                expr->type->stripReferences() );
}

ast::Type const * ReferenceTypeElimination::postvisit(
                ast::ReferenceType const * type ) {
        return new ast::PointerType( type->base, type->qualifiers );
}

} // namespace

// Stored elsewhere (Lvalue2, initially false):
extern bool referencesEliminated;

void convertLvalue( ast::TranslationUnit & translationUnit ) {
        ast::Pass<FixIntrinsicResults>::run( translationUnit );
        ast::Pass<AddressRef>::run( translationUnit );
        ast::Pass<ReferenceConversions>::run( translationUnit );
        ast::Pass<FixIntrinsicArgs>::run( translationUnit );
        ast::Pass<CollapseAddressDeref>::run( translationUnit );
        ast::Pass<GeneralizedLvalue>::run( translationUnit );
        // Last because other passes need reference types to work.
        ast::Pass<ReferenceTypeElimination>::run( translationUnit );
        // From this point forward, nothing should create reference types.
        referencesEliminated = true;
}

ast::Expr const * generalizedLvalue( ast::Expr const * expr ) {
        ast::Pass<GeneralizedLvalue> visitor;
        return expr->accept( visitor );
}

} // namespace GenPoly

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