source: src/SymTab/Autogen.cc @ 8804701

//
// 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.
//
// Autogen.cc --
//
// Author           : Rob Schluntz
// Created On       : Thu Mar 03 15:45:56 2016
// Last Modified By : Peter A. Buhr
// Last Modified On : Tue Jul 12 17:47:17 2016
// Update Count     : 2
//

#include <list>
#include <iterator>
#include "SynTree/Visitor.h"
#include "SynTree/Type.h"
#include "SynTree/Statement.h"
#include "SynTree/TypeSubstitution.h"
#include "Common/utility.h"
#include "AddVisit.h"
#include "MakeLibCfa.h"
#include "Autogen.h"
#include "GenPoly/ScopedSet.h"
#include "Common/ScopedMap.h"
#include "SymTab/Mangler.h"
#include "GenPoly/DeclMutator.h"

namespace SymTab {
        Type * SizeType = 0;
        typedef ScopedMap< std::string, bool > TypeMap;

        /// Data used to generate functions generically. Specifically, the name of the generated function, a function which generates the routine protoype, and a map which contains data to determine whether a function should be generated.
        struct FuncData {
                typedef FunctionType * (*TypeGen)( Type * );
                FuncData( const std::string & fname, const TypeGen & genType, TypeMap & map ) : fname( fname ), genType( genType ), map( map ) {}
                std::string fname;
                TypeGen genType;
                TypeMap & map;
        };

        class AutogenerateRoutines final : public Visitor {
          public:
                std::list< Declaration * > &get_declsToAdd() { return declsToAdd; }

                typedef Visitor Parent;
                using Parent::visit;

                AutogenerateRoutines();

                virtual void visit( EnumDecl *enumDecl );
                virtual void visit( StructDecl *structDecl );
                virtual void visit( UnionDecl *structDecl );
                virtual void visit( TypeDecl *typeDecl );
                virtual void visit( TraitDecl *ctxDecl );
                virtual void visit( FunctionDecl *functionDecl );

                virtual void visit( FunctionType *ftype );
                virtual void visit( PointerType *ftype );

                virtual void visit( CompoundStmt *compoundStmt );
                virtual void visit( SwitchStmt *switchStmt );

          private:
                template< typename StmtClass > void visitStatement( StmtClass *stmt );

                std::list< Declaration * > declsToAdd;
                std::set< std::string > structsDone;
                unsigned int functionNesting = 0;     // current level of nested functions
                /// Note: the following maps could be ScopedSets, but it should be easier to work
                /// deleted functions in if they are maps, since the value false can be inserted
                /// at the current scope without affecting outer scopes or requiring copies.
                TypeMap copyable, assignable, constructable, destructable;
                std::vector< FuncData > data;
        };

        /// generates routines for tuple types.
        /// Doesn't really need to be a mutator, but it's easier to reuse DeclMutator than it is to use AddVisit
        /// or anything we currently have that supports adding new declarations for visitors
        class AutogenTupleRoutines : public GenPoly::DeclMutator {
          public:
                typedef GenPoly::DeclMutator Parent;
                using Parent::mutate;

                virtual DeclarationWithType * mutate( FunctionDecl *functionDecl );

                virtual Type * mutate( TupleType *tupleType );

                virtual CompoundStmt * mutate( CompoundStmt *compoundStmt );

          private:
                unsigned int functionNesting = 0;     // current level of nested functions
                GenPoly::ScopedSet< std::string > seenTuples;
        };

        void autogenerateRoutines( std::list< Declaration * > &translationUnit ) {
                AutogenerateRoutines generator;
                acceptAndAdd( translationUnit, generator, false );

                // needs to be done separately because AutogenerateRoutines skips types that appear as function arguments, etc.
                // AutogenTupleRoutines tupleGenerator;
                // tupleGenerator.mutateDeclarationList( translationUnit );
        }

        bool isUnnamedBitfield( ObjectDecl * obj ) {
                return obj != NULL && obj->get_name() == "" && obj->get_bitfieldWidth() != NULL;
        }

        /// inserts a forward declaration for functionDecl into declsToAdd
        void addForwardDecl( FunctionDecl * functionDecl, std::list< Declaration * > & declsToAdd ) {
                FunctionDecl * decl = functionDecl->clone();
                delete decl->get_statements();
                decl->set_statements( NULL );
                declsToAdd.push_back( decl );
                decl->fixUniqueId();
        }

        /// given type T, generate type of default ctor/dtor, i.e. function type void (*) (T *)
        FunctionType * genDefaultType( Type * paramType ) {
                FunctionType *ftype = new FunctionType( Type::Qualifiers(), false );
                ObjectDecl *dstParam = new ObjectDecl( "_dst", DeclarationNode::NoStorageClass, LinkageSpec::Cforall, nullptr, new PointerType( Type::Qualifiers(), paramType->clone() ), nullptr );
                ftype->get_parameters().push_back( dstParam );

                return ftype;
        }

        /// given type T, generate type of copy ctor, i.e. function type void (*) (T *, T)
        FunctionType * genCopyType( Type * paramType ) {
                FunctionType *ftype = genDefaultType( paramType );
                ObjectDecl *srcParam = new ObjectDecl( "_src", DeclarationNode::NoStorageClass, LinkageSpec::Cforall, nullptr, paramType->clone(), nullptr );
                ftype->get_parameters().push_back( srcParam );
                return ftype;
        }

        /// given type T, generate type of assignment, i.e. function type T (*) (T *, T)
        FunctionType * genAssignType( Type * paramType ) {
                FunctionType *ftype = genCopyType( paramType );
                ObjectDecl *returnVal = new ObjectDecl( "_ret", DeclarationNode::NoStorageClass, LinkageSpec::Cforall, nullptr, paramType->clone(), nullptr );
                ftype->get_returnVals().push_back( returnVal );
                return ftype;
        }

        /// true if the aggregate's layout is dynamic
        template< typename AggrDecl >
        bool hasDynamicLayout( AggrDecl * aggregateDecl ) {
                for ( TypeDecl * param : aggregateDecl->get_parameters() ) {
                        if ( param->get_kind() == TypeDecl::Any ) return true;
                }
                return false;
        }

        /// generate a function decl from a name and type. Nesting depth determines whether
        /// the declaration is static or not; optional paramter determines if declaration is intrinsic
        FunctionDecl * genFunc( const std::string & fname, FunctionType * ftype, unsigned int functionNesting, bool isIntrinsic = false  ) {
                // Routines at global scope marked "static" to prevent multiple definitions in separate translation units
                // because each unit generates copies of the default routines for each aggregate.
                DeclarationNode::StorageClass sc = functionNesting > 0 ? DeclarationNode::NoStorageClass : DeclarationNode::Static;
                LinkageSpec::Spec spec = isIntrinsic ? LinkageSpec::Intrinsic : LinkageSpec::AutoGen;
                FunctionDecl * decl = new FunctionDecl( fname, sc, spec, ftype, new CompoundStmt( noLabels ), true, false );
                decl->fixUniqueId();
                return decl;
        }

        /// inserts base type of first argument into map if pred(funcDecl) is true
        void insert( FunctionDecl *funcDecl, TypeMap & map, FunctionDecl * (*pred)(Declaration *) ) {
                // insert type into constructable, etc. map if appropriate
                if ( pred( funcDecl ) ) {
                        FunctionType * ftype = funcDecl->get_functionType();
                        assert( ! ftype->get_parameters().empty() );
                        Type * t = safe_dynamic_cast< PointerType * >( ftype->get_parameters().front()->get_type() )->get_base();
                        map.insert( Mangler::mangleType( t ), true );
                }
        }

        /// using map and t, determines if is constructable, etc.
        bool lookup( const TypeMap & map, Type * t ) {
                if ( dynamic_cast< PointerType * >( t ) ) {
                        // will need more complicated checking if we want this to work with pointer types, since currently
                        return true;
                } else if ( ArrayType * at = dynamic_cast< ArrayType * >( t ) ) {
                        // an array's constructor, etc. is generated on the fly based on the base type's constructor, etc.
                        return lookup( map, at->get_base() );
                }
                TypeMap::const_iterator it = map.find( Mangler::mangleType( t ) );
                if ( it != map.end() ) return it->second;
                // something that does not appear in the map is by default not constructable, etc.
                return false;
        }

        /// using map and aggr, examines each member to determine if constructor, etc. should be generated
        template<typename AggrDecl>
        bool shouldGenerate( const TypeMap & map, AggrDecl * aggr ) {
                for ( Declaration * dcl : aggr->get_members() ) {
                        if ( DeclarationWithType * dwt = dynamic_cast< DeclarationWithType * >( dcl ) ) {
                                if ( ! lookup( map, dwt->get_type() ) ) return false;
                        }
                }
                return true;
        }

        /// data structure for abstracting the generation of special functions
        template< typename OutputIterator >
        struct FuncGenerator {
                StructDecl *aggregateDecl;
                StructInstType *refType;
                unsigned int functionNesting;
                const std::list< TypeDecl* > & typeParams;
                OutputIterator out;
                FuncGenerator( StructDecl *aggregateDecl, StructInstType *refType, unsigned int functionNesting, const std::list< TypeDecl* > & typeParams, OutputIterator out ) : aggregateDecl( aggregateDecl ), refType( refType ), functionNesting( functionNesting ), typeParams( typeParams ), out( out ) {}

                /// generates a function (?{}, ?=?, ^?{}) based on the data argument and members. If function is generated, inserts the type into the map.
                void gen( const FuncData & data ) {
                        if ( ! shouldGenerate( data.map, aggregateDecl ) ) return;
                        FunctionType * ftype = data.genType( refType );
                        cloneAll( typeParams, ftype->get_forall() );
                        *out++ = genFunc( data.fname, ftype, functionNesting );
                        data.map.insert( Mangler::mangleType( refType ), true );
                }
        };

        template< typename OutputIterator >
        FuncGenerator<OutputIterator> makeFuncGenerator( StructDecl *aggregateDecl, StructInstType *refType, unsigned int functionNesting, const std::list< TypeDecl* > & typeParams, OutputIterator out ) {
                return FuncGenerator<OutputIterator>( aggregateDecl, refType, functionNesting, typeParams, out );
        }

        /// generates a single enumeration assignment expression
        ApplicationExpr * genEnumAssign( FunctionType * ftype, FunctionDecl * assignDecl ) {
                // enum copy construct and assignment is just C-style assignment.
                // this looks like a bad recursive call, but code gen will turn it into
                // a C-style assignment.
                // This happens before function pointer type conversion, so need to do it manually here
                // NOTE: ftype is not necessarily the functionType belonging to assignDecl - ftype is the
                // type of the function that this expression is being generated for (so that the correct
                // parameters) are using in the variable exprs
                assert( ftype->get_parameters().size() == 2 );
                ObjectDecl * dstParam = safe_dynamic_cast< ObjectDecl * >( ftype->get_parameters().front() );
                ObjectDecl * srcParam = safe_dynamic_cast< ObjectDecl * >( ftype->get_parameters().back() );

                VariableExpr * assignVarExpr = new VariableExpr( assignDecl );
                Type * assignVarExprType = assignVarExpr->get_result();
                assignVarExprType = new PointerType( Type::Qualifiers(), assignVarExprType );
                assignVarExpr->set_result( assignVarExprType );
                ApplicationExpr * assignExpr = new ApplicationExpr( assignVarExpr );
                assignExpr->get_args().push_back( new VariableExpr( dstParam ) );
                assignExpr->get_args().push_back( new VariableExpr( srcParam ) );
                return assignExpr;
        }

        // E ?=?(E volatile*, int),
        //   ?=?(E _Atomic volatile*, int);
        void makeEnumFunctions( EnumDecl *enumDecl, EnumInstType *refType, unsigned int functionNesting, std::list< Declaration * > &declsToAdd ) {

                // T ?=?(E *, E);
                FunctionType *assignType = genAssignType( refType );

                // void ?{}(E *); void ^?{}(E *);
                FunctionType * ctorType = genDefaultType( refType->clone() );
                FunctionType * dtorType = genDefaultType( refType->clone() );

                // void ?{}(E *, E);
                FunctionType *copyCtorType = genCopyType( refType->clone() );

                // xxx - should we also generate void ?{}(E *, int) and E ?{}(E *, E)?
                // right now these cases work, but that might change.

                // xxx - Temporary: make these functions intrinsic so they codegen as C assignment.
                // Really they're something of a cross between instrinsic and autogen, so should
                // probably make a new linkage type
                FunctionDecl *assignDecl = genFunc( "?=?", assignType, functionNesting, true );
                FunctionDecl *ctorDecl = genFunc( "?{}", ctorType, functionNesting, true );
                FunctionDecl *copyCtorDecl = genFunc( "?{}", copyCtorType, functionNesting, true );
                FunctionDecl *dtorDecl = genFunc( "^?{}", dtorType, functionNesting, true );

                // body is either return stmt or expr stmt
                assignDecl->get_statements()->get_kids().push_back( new ReturnStmt( noLabels, genEnumAssign( assignType, assignDecl ) ) );
                copyCtorDecl->get_statements()->get_kids().push_back( new ExprStmt( noLabels, genEnumAssign( copyCtorType, assignDecl ) ) );

                declsToAdd.push_back( ctorDecl );
                declsToAdd.push_back( copyCtorDecl );
                declsToAdd.push_back( dtorDecl );
                declsToAdd.push_back( assignDecl ); // assignment should come last since it uses copy constructor in return
        }

        /// generates a single struct member operation (constructor call, destructor call, assignment call)
        void makeStructMemberOp( ObjectDecl * dstParam, Expression * src, DeclarationWithType * field, FunctionDecl * func, bool isDynamicLayout, bool forward = true ) {
                ObjectDecl * returnVal = NULL;
                if ( ! func->get_functionType()->get_returnVals().empty() ) {
                        returnVal = dynamic_cast<ObjectDecl*>( func->get_functionType()->get_returnVals().front() );
                }

                InitTweak::InitExpander srcParam( src );

                // assign to destination (and return value if generic)
                UntypedExpr *derefExpr = UntypedExpr::createDeref( new VariableExpr( dstParam ) );
                Expression *dstselect = new MemberExpr( field, derefExpr );
                genImplicitCall( srcParam, dstselect, func->get_name(), back_inserter( func->get_statements()->get_kids() ), field, forward );

                if ( isDynamicLayout && returnVal ) {
                        // xxx - there used to be a dereference on returnVal, but this seems to have been wrong?
                        Expression *retselect = new MemberExpr( field, new VariableExpr( returnVal ) );
                        genImplicitCall( srcParam, retselect, func->get_name(), back_inserter( func->get_statements()->get_kids() ), field, forward );
                } // if
        }

        /// generates the body of a struct function by iterating the struct members (via parameters) - generates default ctor, copy ctor, assignment, and dtor bodies, but NOT field ctor bodies
        template<typename Iterator>
        void makeStructFunctionBody( Iterator member, Iterator end, FunctionDecl * func, bool isDynamicLayout, bool forward = true ) {
                for ( ; member != end; ++member ) {
                        if ( DeclarationWithType *field = dynamic_cast< DeclarationWithType * >( *member ) ) { // otherwise some form of type declaration, e.g. Aggregate
                                // query the type qualifiers of this field and skip assigning it if it is marked const.
                                // If it is an array type, we need to strip off the array layers to find its qualifiers.
                                Type * type = field->get_type();
                                while ( ArrayType * at = dynamic_cast< ArrayType * >( type ) ) {
                                        type = at->get_base();
                                }

                                if ( type->get_qualifiers().isConst && func->get_name() == "?=?" ) {
                                        // don't assign const members, but do construct/destruct
                                        continue;
                                }

                                if ( field->get_name() == "" ) {
                                        // don't assign to anonymous members
                                        // xxx - this is a temporary fix. Anonymous members tie into
                                        // our inheritance model. I think the correct way to handle this is to
                                        // cast the structure to the type of the member and let the resolver
                                        // figure out whether it's valid and have a pass afterwards that fixes
                                        // the assignment to use pointer arithmetic with the offset of the
                                        // member, much like how generic type members are handled.
                                        continue;
                                }

                                assert( ! func->get_functionType()->get_parameters().empty() );
                                ObjectDecl * dstParam = dynamic_cast<ObjectDecl*>( func->get_functionType()->get_parameters().front() );
                                ObjectDecl * srcParam = NULL;
                                if ( func->get_functionType()->get_parameters().size() == 2 ) {
                                        srcParam = dynamic_cast<ObjectDecl*>( func->get_functionType()->get_parameters().back() );
                                }
                                // srcParam may be NULL, in which case we have default ctor/dtor
                                assert( dstParam );

                                Expression *srcselect = srcParam ? new MemberExpr( field, new VariableExpr( srcParam ) ) : NULL;
                                makeStructMemberOp( dstParam, srcselect, field, func, isDynamicLayout, forward );
                        } // if
                } // for
        } // makeStructFunctionBody

        /// generate the body of a constructor which takes parameters that match fields, e.g.
        /// void ?{}(A *, int) and void?{}(A *, int, int) for a struct A which has two int fields.
        template<typename Iterator>
        void makeStructFieldCtorBody( Iterator member, Iterator end, FunctionDecl * func, bool isDynamicLayout ) {
                FunctionType * ftype = func->get_functionType();
                std::list<DeclarationWithType*> & params = ftype->get_parameters();
                assert( params.size() >= 2 );  // should not call this function for default ctor, etc.

                // skip 'this' parameter
                ObjectDecl * dstParam = dynamic_cast<ObjectDecl*>( params.front() );
                assert( dstParam );
                std::list<DeclarationWithType*>::iterator parameter = params.begin()+1;
                for ( ; member != end; ++member ) {
                        if ( DeclarationWithType * field = dynamic_cast<DeclarationWithType*>( *member ) ) {
                                if ( isUnnamedBitfield( dynamic_cast< ObjectDecl * > ( field ) ) ) {
                                        // don't make a function whose parameter is an unnamed bitfield
                                        continue;
                                } else if ( field->get_name() == "" ) {
                                        // don't assign to anonymous members
                                        // xxx - this is a temporary fix. Anonymous members tie into
                                        // our inheritance model. I think the correct way to handle this is to
                                        // cast the structure to the type of the member and let the resolver
                                        // figure out whether it's valid and have a pass afterwards that fixes
                                        // the assignment to use pointer arithmetic with the offset of the
                                        // member, much like how generic type members are handled.
                                        continue;
                                } else if ( parameter != params.end() ) {
                                        // matching parameter, initialize field with copy ctor
                                        Expression *srcselect = new VariableExpr(*parameter);
                                        makeStructMemberOp( dstParam, srcselect, field, func, isDynamicLayout );
                                        ++parameter;
                                } else {
                                        // no matching parameter, initialize field with default ctor
                                        makeStructMemberOp( dstParam, NULL, field, func, isDynamicLayout );
                                }
                        }
                }
        }

        /// generates struct constructors, destructor, and assignment functions
        void makeStructFunctions( StructDecl *aggregateDecl, StructInstType *refType, unsigned int functionNesting, std::list< Declaration * > & declsToAdd, const std::vector< FuncData > & data ) {
                // Make function polymorphic in same parameters as generic struct, if applicable
                const std::list< TypeDecl* > & typeParams = aggregateDecl->get_parameters(); // List of type variables to be placed on the generated functions
                bool isDynamicLayout = hasDynamicLayout( aggregateDecl );  // NOTE this flag is an incredibly ugly kludge; we should fix the assignment signature instead (ditto for union)

                // generate each of the functions based on the supplied FuncData objects
                std::list< FunctionDecl * > newFuncs;
                auto generator = makeFuncGenerator( aggregateDecl, refType, functionNesting, typeParams, back_inserter( newFuncs ) );
                for ( const FuncData & d : data ) {
                        generator.gen( d );
                }
                // field ctors are only generated if default constructor and copy constructor are both generated
                unsigned numCtors = std::count_if( newFuncs.begin(), newFuncs.end(), [](FunctionDecl * dcl) { return InitTweak::isConstructor( dcl->get_name() ); } );

                if ( functionNesting == 0 ) {
                        // forward declare if top-level struct, so that
                        // type is complete as soon as its body ends
                        // Note: this is necessary if we want structs which contain
                        // generic (otype) structs as members.
                        for ( FunctionDecl * dcl : newFuncs ) {
                                addForwardDecl( dcl, declsToAdd );
                        }
                }

                for ( FunctionDecl * dcl : newFuncs ) {
                        // generate appropriate calls to member ctor, assignment
                        // destructor needs to do everything in reverse, so pass "forward" based on whether the function is a destructor
                        if ( ! InitTweak::isDestructor( dcl->get_name() ) ) {
                                makeStructFunctionBody( aggregateDecl->get_members().begin(), aggregateDecl->get_members().end(), dcl, isDynamicLayout );
                        } else {
                                makeStructFunctionBody( aggregateDecl->get_members().rbegin(), aggregateDecl->get_members().rend(), dcl, isDynamicLayout, false );
                        }
                        if ( InitTweak::isAssignment( dcl->get_name() ) ) {
                                // assignment needs to return a value
                                FunctionType * assignType = dcl->get_functionType();
                                assert( assignType->get_parameters().size() == 2 );
                                ObjectDecl * srcParam = safe_dynamic_cast< ObjectDecl * >( assignType->get_parameters().back() );
                                dcl->get_statements()->get_kids().push_back( new ReturnStmt( noLabels, new VariableExpr( srcParam ) ) );
                        }
                        declsToAdd.push_back( dcl );
                }

                // create constructors which take each member type as a parameter.
                // for example, for struct A { int x, y; }; generate
                //   void ?{}(A *, int) and void ?{}(A *, int, int)
                // Field constructors are only generated if default and copy constructor
                // are generated, since they need access to both
                if ( numCtors == 2 ) {
                        FunctionType * memCtorType = genDefaultType( refType );
                        cloneAll( typeParams, memCtorType->get_forall() );
                        for ( std::list<Declaration *>::iterator i = aggregateDecl->get_members().begin(); i != aggregateDecl->get_members().end(); ++i ) {
                                DeclarationWithType * member = dynamic_cast<DeclarationWithType *>( *i );
                                assert( member );
                                if ( isUnnamedBitfield( dynamic_cast< ObjectDecl * > ( member ) ) ) {
                                        // don't make a function whose parameter is an unnamed bitfield
                                        continue;
                                } else if ( member->get_name() == "" ) {
                                        // don't assign to anonymous members
                                        // xxx - this is a temporary fix. Anonymous members tie into
                                        // our inheritance model. I think the correct way to handle this is to
                                        // cast the structure to the type of the member and let the resolver
                                        // figure out whether it's valid and have a pass afterwards that fixes
                                        // the assignment to use pointer arithmetic with the offset of the
                                        // member, much like how generic type members are handled.
                                        continue;
                                }
                                memCtorType->get_parameters().push_back( new ObjectDecl( member->get_name(), DeclarationNode::NoStorageClass, LinkageSpec::Cforall, 0, member->get_type()->clone(), 0 ) );
                                FunctionDecl * ctor = genFunc( "?{}", memCtorType->clone(), functionNesting );
                                makeStructFieldCtorBody( aggregateDecl->get_members().begin(), aggregateDecl->get_members().end(), ctor, isDynamicLayout );
                                declsToAdd.push_back( ctor );
                        }
                        delete memCtorType;
                }
        }

        /// generate a single union assignment expression (using memcpy)
        template< typename OutputIterator >
        void makeUnionFieldsAssignment( ObjectDecl * srcParam, ObjectDecl * dstParam, OutputIterator out ) {
                UntypedExpr *copy = new UntypedExpr( new NameExpr( "__builtin_memcpy" ) );
                copy->get_args().push_back( new VariableExpr( dstParam ) );
                copy->get_args().push_back( new AddressExpr( new VariableExpr( srcParam ) ) );
                copy->get_args().push_back( new SizeofExpr( srcParam->get_type()->clone() ) );
                *out++ = new ExprStmt( noLabels, copy );
        }

        /// generates the body of a union assignment/copy constructor/field constructor
        void makeUnionAssignBody( FunctionDecl * funcDecl, bool isDynamicLayout ) {
                FunctionType * ftype = funcDecl->get_functionType();
                assert( ftype->get_parameters().size() == 2 );
                ObjectDecl * dstParam = safe_dynamic_cast< ObjectDecl * >( ftype->get_parameters().front() );
                ObjectDecl * srcParam = safe_dynamic_cast< ObjectDecl * >( ftype->get_parameters().back() );
                ObjectDecl * returnVal = nullptr;
                if ( ! ftype->get_returnVals().empty() ) {
                        returnVal = safe_dynamic_cast< ObjectDecl * >( ftype->get_returnVals().front() );
                }

                makeUnionFieldsAssignment( srcParam, dstParam, back_inserter( funcDecl->get_statements()->get_kids() ) );
                if ( returnVal ) {
                        if ( isDynamicLayout ) makeUnionFieldsAssignment( srcParam, returnVal, back_inserter( funcDecl->get_statements()->get_kids() ) );
                        else funcDecl->get_statements()->get_kids().push_back( new ReturnStmt( noLabels, new VariableExpr( srcParam ) ) );
                }
        }

        /// generates union constructors, destructors, and assignment operator
        void makeUnionFunctions( UnionDecl *aggregateDecl, UnionInstType *refType, unsigned int functionNesting, std::list< Declaration * > & declsToAdd ) {
                // Make function polymorphic in same parameters as generic union, if applicable
                const std::list< TypeDecl* > & typeParams = aggregateDecl->get_parameters(); // List of type variables to be placed on the generated functions
                bool isDynamicLayout = hasDynamicLayout( aggregateDecl );  // NOTE this flag is an incredibly ugly kludge; we should fix the assignment signature instead (ditto for struct)

                // default ctor/dtor need only first parameter
                // void ?{}(T *); void ^?{}(T *);
                FunctionType *ctorType = genDefaultType( refType );
                FunctionType *dtorType = genDefaultType( refType );

                // copy ctor needs both parameters
                // void ?{}(T *, T);
                FunctionType *copyCtorType = genCopyType( refType );

                // assignment needs both and return value
                // T ?=?(T *, T);
                FunctionType *assignType = genAssignType( refType );

                cloneAll( typeParams, ctorType->get_forall() );
                cloneAll( typeParams, dtorType->get_forall() );
                cloneAll( typeParams, copyCtorType->get_forall() );
                cloneAll( typeParams, assignType->get_forall() );

                // Routines at global scope marked "static" to prevent multiple definitions is separate translation units
                // because each unit generates copies of the default routines for each aggregate.
                FunctionDecl *assignDecl = genFunc( "?=?", assignType, functionNesting );
                FunctionDecl *ctorDecl = genFunc( "?{}",  ctorType, functionNesting );
                FunctionDecl *copyCtorDecl = genFunc( "?{}", copyCtorType, functionNesting );
                FunctionDecl *dtorDecl = genFunc( "^?{}", dtorType, functionNesting );

                makeUnionAssignBody( assignDecl, isDynamicLayout );

                // body of assignment and copy ctor is the same
                makeUnionAssignBody( copyCtorDecl, isDynamicLayout );

                // create a constructor which takes the first member type as a parameter.
                // for example, for Union A { int x; double y; }; generate
                // void ?{}(A *, int)
                // This is to mimic C's behaviour which initializes the first member of the union.
                std::list<Declaration *> memCtors;
                for ( Declaration * member : aggregateDecl->get_members() ) {
                        if ( DeclarationWithType * field = dynamic_cast< DeclarationWithType * >( member ) ) {
                                ObjectDecl * srcParam = new ObjectDecl( "src", DeclarationNode::NoStorageClass, LinkageSpec::Cforall, 0, field->get_type()->clone(), 0 );

                                FunctionType * memCtorType = ctorType->clone();
                                memCtorType->get_parameters().push_back( srcParam );
                                FunctionDecl * ctor = genFunc( "?{}", memCtorType, functionNesting );

                                makeUnionAssignBody( ctor, isDynamicLayout );
                                memCtors.push_back( ctor );
                                // only generate a ctor for the first field
                                break;
                        }
                }

                declsToAdd.push_back( ctorDecl );
                declsToAdd.push_back( copyCtorDecl );
                declsToAdd.push_back( dtorDecl );
                declsToAdd.push_back( assignDecl ); // assignment should come last since it uses copy constructor in return
                declsToAdd.splice( declsToAdd.end(), memCtors );
        }

        AutogenerateRoutines::AutogenerateRoutines() {
                // the order here determines the order that these functions are generated.
                // assignment should come last since it uses copy constructor in return.
                data.push_back( FuncData( "?{}", genDefaultType, constructable ) );
                data.push_back( FuncData( "?{}", genCopyType, copyable ) );
                data.push_back( FuncData( "^?{}", genDefaultType, destructable ) );
                data.push_back( FuncData( "?=?", genAssignType, assignable ) );
        }

        void AutogenerateRoutines::visit( EnumDecl *enumDecl ) {
                if ( ! enumDecl->get_members().empty() ) {
                        EnumInstType *enumInst = new EnumInstType( Type::Qualifiers(), enumDecl->get_name() );
                        // enumInst->set_baseEnum( enumDecl );
                        // declsToAdd.push_back(
                        makeEnumFunctions( enumDecl, enumInst, functionNesting, declsToAdd );
                }
        }

        void AutogenerateRoutines::visit( StructDecl *structDecl ) {
                if ( structDecl->has_body() && structsDone.find( structDecl->get_name() ) == structsDone.end() ) {
                        StructInstType structInst( Type::Qualifiers(), structDecl->get_name() );
                        for ( TypeDecl * typeDecl : structDecl->get_parameters() ) {
                                // need to visit assertions so that they are added to the appropriate maps
                                acceptAll( typeDecl->get_assertions(), *this );
                                structInst.get_parameters().push_back( new TypeExpr( new TypeInstType( Type::Qualifiers(), typeDecl->get_name(), typeDecl ) ) );
                        }
                        structInst.set_baseStruct( structDecl );
                        makeStructFunctions( structDecl, &structInst, functionNesting, declsToAdd, data );
                        structsDone.insert( structDecl->get_name() );
                } // if
        }

        void AutogenerateRoutines::visit( UnionDecl *unionDecl ) {
                if ( ! unionDecl->get_members().empty() ) {
                        UnionInstType unionInst( Type::Qualifiers(), unionDecl->get_name() );
                        unionInst.set_baseUnion( unionDecl );
                        for ( TypeDecl * typeDecl : unionDecl->get_parameters() ) {
                                unionInst.get_parameters().push_back( new TypeExpr( new TypeInstType( Type::Qualifiers(), typeDecl->get_name(), typeDecl ) ) );
                        }
                        makeUnionFunctions( unionDecl, &unionInst, functionNesting, declsToAdd );
                } // if
        }

        void AutogenerateRoutines::visit( TypeDecl *typeDecl ) {
                TypeInstType *typeInst = new TypeInstType( Type::Qualifiers(), typeDecl->get_name(), false );
                typeInst->set_baseType( typeDecl );
                ObjectDecl *src = new ObjectDecl( "_src", DeclarationNode::NoStorageClass, LinkageSpec::Cforall, nullptr, typeInst->clone(), nullptr );
                ObjectDecl *dst = new ObjectDecl( "_dst", DeclarationNode::NoStorageClass, LinkageSpec::Cforall, nullptr, new PointerType( Type::Qualifiers(), typeInst->clone() ), nullptr );

                std::list< Statement * > stmts;
                if ( typeDecl->get_base() ) {
                        // xxx - generate ctor/dtors for typedecls, e.g.
                        // otype T = int *;
                        UntypedExpr *assign = new UntypedExpr( new NameExpr( "?=?" ) );
                        assign->get_args().push_back( new CastExpr( new VariableExpr( dst ), new PointerType( Type::Qualifiers(), typeDecl->get_base()->clone() ) ) );
                        assign->get_args().push_back( new CastExpr( new VariableExpr( src ), typeDecl->get_base()->clone() ) );
                        stmts.push_back( new ReturnStmt( std::list< Label >(), assign ) );
                } // if
                FunctionType *type = new FunctionType( Type::Qualifiers(), false );
                type->get_returnVals().push_back( new ObjectDecl( "", DeclarationNode::NoStorageClass, LinkageSpec::Cforall, 0, typeInst, 0 ) );
                type->get_parameters().push_back( dst );
                type->get_parameters().push_back( src );
                FunctionDecl *func = genFunc( "?=?", type, functionNesting );
                func->get_statements()->get_kids() = stmts;
                declsToAdd.push_back( func );
        }

        void addDecls( std::list< Declaration * > &declsToAdd, std::list< Statement * > &statements, std::list< Statement * >::iterator i ) {
                for ( std::list< Declaration * >::iterator decl = declsToAdd.begin(); decl != declsToAdd.end(); ++decl ) {
                        statements.insert( i, new DeclStmt( noLabels, *decl ) );
                } // for
                declsToAdd.clear();
        }

        void AutogenerateRoutines::visit( FunctionType *) {
                // ensure that we don't add assignment ops for types defined as part of the function
        }

        void AutogenerateRoutines::visit( PointerType *) {
                // ensure that we don't add assignment ops for types defined as part of the pointer
        }

        void AutogenerateRoutines::visit( TraitDecl *) {
                // ensure that we don't add assignment ops for types defined as part of the trait
        }

        template< typename StmtClass >
        inline void AutogenerateRoutines::visitStatement( StmtClass *stmt ) {
                std::set< std::string > oldStructs = structsDone;
                addVisit( stmt, *this );
                structsDone = oldStructs;
        }

        void AutogenerateRoutines::visit( FunctionDecl *functionDecl ) {
                // record the existence of this function as appropriate
                insert( functionDecl, constructable, InitTweak::isDefaultConstructor );
                insert( functionDecl, assignable, InitTweak::isAssignment );
                insert( functionDecl, copyable, InitTweak::isCopyConstructor );
                insert( functionDecl, destructable, InitTweak::isDestructor );

                maybeAccept( functionDecl->get_functionType(), *this );
                acceptAll( functionDecl->get_oldDecls(), *this );
                functionNesting += 1;
                maybeAccept( functionDecl->get_statements(), *this );
                functionNesting -= 1;
        }

        void AutogenerateRoutines::visit( CompoundStmt *compoundStmt ) {
                constructable.beginScope();
                assignable.beginScope();
                copyable.beginScope();
                destructable.beginScope();
                visitStatement( compoundStmt );
                constructable.endScope();
                assignable.endScope();
                copyable.endScope();
                destructable.endScope();
        }

        void AutogenerateRoutines::visit( SwitchStmt *switchStmt ) {
                visitStatement( switchStmt );
        }

        void makeTupleFunctionBody( FunctionDecl * function ) {
                FunctionType * ftype = function->get_functionType();
                assertf( ftype->get_parameters().size() == 1 || ftype->get_parameters().size() == 2, "too many parameters in generated tuple function" );

                UntypedExpr * untyped = new UntypedExpr( new NameExpr( function->get_name() ) );

                /// xxx - &* is used to make this easier for later passes to handle
                untyped->get_args().push_back( new AddressExpr( UntypedExpr::createDeref( new VariableExpr( ftype->get_parameters().front() ) ) ) );
                if ( ftype->get_parameters().size() == 2 ) {
                        untyped->get_args().push_back( new VariableExpr( ftype->get_parameters().back() ) );
                }
                function->get_statements()->get_kids().push_back( new ExprStmt( noLabels, untyped ) );
                function->get_statements()->get_kids().push_back( new ReturnStmt( noLabels, UntypedExpr::createDeref( new VariableExpr( ftype->get_parameters().front() ) ) ) );
        }

        Type * AutogenTupleRoutines::mutate( TupleType * tupleType ) {
                tupleType = safe_dynamic_cast< TupleType * >( Parent::mutate( tupleType ) );
                std::string mangleName = SymTab::Mangler::mangleType( tupleType );
                if ( seenTuples.find( mangleName ) != seenTuples.end() ) return tupleType;
                seenTuples.insert( mangleName );

                // T ?=?(T *, T);
                FunctionType *assignType = genAssignType( tupleType );

                // void ?{}(T *); void ^?{}(T *);
                FunctionType *ctorType = genDefaultType( tupleType );
                FunctionType *dtorType = genDefaultType( tupleType );

                // void ?{}(T *, T);
                FunctionType *copyCtorType = genCopyType( tupleType );

                std::set< TypeDecl* > done;
                std::list< TypeDecl * > typeParams;
                for ( Type * t : *tupleType ) {
                        if ( TypeInstType * ty = dynamic_cast< TypeInstType * >( t ) ) {
                                if ( ! done.count( ty->get_baseType() ) ) {
                                        TypeDecl * newDecl = new TypeDecl( ty->get_baseType()->get_name(), DeclarationNode::NoStorageClass, nullptr, TypeDecl::Any );
                                        TypeInstType * inst = new TypeInstType( Type::Qualifiers(), newDecl->get_name(), newDecl );
                                        newDecl->get_assertions().push_back( new FunctionDecl( "?=?", DeclarationNode::NoStorageClass, LinkageSpec::Cforall, genAssignType( inst ), nullptr, true, false ) );
                                        newDecl->get_assertions().push_back( new FunctionDecl( "?{}", DeclarationNode::NoStorageClass, LinkageSpec::Cforall, genDefaultType( inst ), nullptr, true, false ) );
                                        newDecl->get_assertions().push_back( new FunctionDecl( "?{}", DeclarationNode::NoStorageClass, LinkageSpec::Cforall, genCopyType( inst ), nullptr, true, false ) );
                                        newDecl->get_assertions().push_back( new FunctionDecl( "^?{}", DeclarationNode::NoStorageClass, LinkageSpec::Cforall, genDefaultType( inst ), nullptr, true, false ) );
                                        typeParams.push_back( newDecl );
                                        done.insert( ty->get_baseType() );
                                }
                        }
                }
                cloneAll( typeParams, ctorType->get_forall() );
                cloneAll( typeParams, dtorType->get_forall() );
                cloneAll( typeParams, copyCtorType->get_forall() );
                cloneAll( typeParams, assignType->get_forall() );

                FunctionDecl *assignDecl = genFunc( "?=?", assignType, functionNesting );
                FunctionDecl *ctorDecl = genFunc( "?{}", ctorType, functionNesting );
                FunctionDecl *copyCtorDecl = genFunc( "?{}", copyCtorType, functionNesting );
                FunctionDecl *dtorDecl = genFunc( "^?{}", dtorType, functionNesting );

                makeTupleFunctionBody( assignDecl );
                makeTupleFunctionBody( ctorDecl );
                makeTupleFunctionBody( copyCtorDecl );
                makeTupleFunctionBody( dtorDecl );

                addDeclaration( ctorDecl );
                addDeclaration( copyCtorDecl );
                addDeclaration( dtorDecl );
                addDeclaration( assignDecl ); // assignment should come last since it uses copy constructor in return

                return tupleType;
        }

        DeclarationWithType * AutogenTupleRoutines::mutate( FunctionDecl *functionDecl ) {
                functionDecl->set_functionType( maybeMutate( functionDecl->get_functionType(), *this ) );
                mutateAll( functionDecl->get_oldDecls(), *this );
                functionNesting += 1;
                functionDecl->set_statements( maybeMutate( functionDecl->get_statements(), *this ) );
                functionNesting -= 1;
                return functionDecl;
        }

        CompoundStmt * AutogenTupleRoutines::mutate( CompoundStmt *compoundStmt ) {
                seenTuples.beginScope();
                compoundStmt = safe_dynamic_cast< CompoundStmt * >( Parent::mutate( compoundStmt ) );
                seenTuples.endScope();
                return compoundStmt;
        }
} // SymTab