source: src/InitTweak/RemoveInit.cc @ a5a71d0

//
// 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.
//
// RemoveInit.cc --
//
// Author           : Rob Schluntz
// Created On       : Mon May 18 07:44:20 2015
// Last Modified By : Rob Schluntz
// Last Modified On : Mon Apr 04 17:18:03 2016
// Update Count     : 166
//

#include <stack>
#include <list>
#include "RemoveInit.h"
#include "SynTree/Declaration.h"
#include "SynTree/Type.h"
#include "SynTree/Expression.h"
#include "SynTree/Statement.h"
#include "SynTree/Initializer.h"
#include "SynTree/Mutator.h"
#include "SymTab/Autogen.h"
#include "GenPoly/PolyMutator.h"

namespace InitTweak {
        namespace {
                const std::list<Label> noLabels;
                const std::list<Expression *> noDesignators;
        }

        class RemoveInit : public GenPoly::PolyMutator {
          public:
                /// removes and replaces initialization for polymorphic value objects
                /// with assignment (TODO: constructor) statements.
                /// also consistently allocates a temporary variable for the return value
                /// of a function so that anything which the resolver decides can be assigned
                /// into the return type of a function can be returned.
                static void removeInitializers( std::list< Declaration * > &translationUnit );

                RemoveInit();
                virtual ObjectDecl * mutate( ObjectDecl *objDecl );
                virtual DeclarationWithType * mutate( FunctionDecl *functionDecl );

                virtual Statement * mutate( ReturnStmt * returnStmt );

          protected:
                std::list<DeclarationWithType*> returnVals;
                UniqueName tempNamer;
                std::string funcName;
        };

        class CtorDtor : public GenPoly::PolyMutator {
          public:
                /// create constructor and destructor statements for object declarations.
                /// Destructors are inserted directly into the code, whereas constructors
                /// will be added in after the resolver has run so that the initializer expression
                /// is only removed if a constructor is found
                static void generateCtorDtor( std::list< Declaration * > &translationUnit );

                CtorDtor() : inFunction( false ) {}

                virtual ObjectDecl * mutate( ObjectDecl * );
                virtual DeclarationWithType * mutate( FunctionDecl *functionDecl );
                virtual Declaration* mutate( StructDecl *aggregateDecl );
                virtual Declaration* mutate( UnionDecl *aggregateDecl );
                virtual Declaration* mutate( EnumDecl *aggregateDecl );
                virtual Declaration* mutate( TraitDecl *aggregateDecl );
                virtual TypeDecl* mutate( TypeDecl *typeDecl );
                virtual Declaration* mutate( TypedefDecl *typeDecl );

          protected:
                bool inFunction;
        };

        void tweak( std::list< Declaration * > & translationUnit ) {
                RemoveInit::removeInitializers( translationUnit );
                CtorDtor::generateCtorDtor( translationUnit );
        }

        void RemoveInit::removeInitializers( std::list< Declaration * > & translationUnit ) {
                RemoveInit remover;
                mutateAll( translationUnit, remover );
        }

        RemoveInit::RemoveInit() : tempNamer( "_retVal" ) {}

        // in the case where an object has an initializer and a polymorphic type, insert an assignment immediately after the
        // declaration. This will (seemingly) cause the later phases to do the right thing with the assignment
        ObjectDecl *RemoveInit::mutate( ObjectDecl *objDecl ) {
                if (objDecl->get_init() && dynamic_cast<TypeInstType*>(objDecl->get_type())) {
                        if (SingleInit * single = dynamic_cast<SingleInit*>(objDecl->get_init())) {
                                // xxx this can be more complicated - consider ListInit
                                UntypedExpr *assign = new UntypedExpr( new NameExpr( "?{}" ) );
                                assign->get_args().push_back( new AddressExpr (new NameExpr( objDecl->get_name() ) ) );
                                assign->get_args().push_back( single->get_value()->clone() );
                                stmtsToAddAfter.push_back(new ExprStmt(noLabels, assign));
                        } // if
                } // if
                return objDecl;
        }

        Statement *RemoveInit::mutate( ReturnStmt *returnStmt ) {
                // update for multiple return values
                assert( returnVals.size() == 0 || returnVals.size() == 1 );
                // hands off if the function returns an lvalue - we don't want to allocate a temporary if a variable's address
                // is being returned
                if ( returnStmt->get_expr() && returnVals.size() == 1 && funcName != "?=?" && ! returnVals.front()->get_type()->get_isLvalue()  ) {
                        // ensure return value is not destructed by explicitly creating
                        // an empty SingleInit node wherein maybeConstruct is false
                        ObjectDecl *newObj = new ObjectDecl( tempNamer.newName(), DeclarationNode::NoStorageClass, LinkageSpec::C, 0, returnVals.front()->get_type()->clone(), new ListInit( std::list<Initializer*>(), noDesignators, false ) );
                        stmtsToAdd.push_back( new DeclStmt( noLabels, newObj ) );

                        // and explicitly create the constructor expression separately
                        UntypedExpr *construct = new UntypedExpr( new NameExpr( "?{}" ) );
                        construct->get_args().push_back( new AddressExpr (new NameExpr( newObj->get_name() ) ) );
                        construct->get_args().push_back( returnStmt->get_expr() );
                        stmtsToAdd.push_back(new ExprStmt(noLabels, construct));

                        returnStmt->set_expr( new VariableExpr( newObj ) );
                } // if
                return returnStmt;
        }

        DeclarationWithType* RemoveInit::mutate( FunctionDecl *functionDecl ) {
                std::list<DeclarationWithType*> oldReturnVals = returnVals;
                std::string oldFuncName = funcName;

                FunctionType * type = functionDecl->get_functionType();
                returnVals = type->get_returnVals();
                funcName = functionDecl->get_name();
                DeclarationWithType * decl = Mutator::mutate( functionDecl );
                returnVals = oldReturnVals;
                funcName = oldFuncName;
                return decl;
        }


        void CtorDtor::generateCtorDtor( std::list< Declaration * > & translationUnit ) {
                CtorDtor ctordtor;
                mutateAll( translationUnit, ctordtor );
        }

        namespace {
                bool tryConstruct( ObjectDecl * objDecl ) {
                        // xxx - handle designations
                        return ! LinkageSpec::isBuiltin( objDecl->get_linkage() ) &&
                                (objDecl->get_init() == NULL ||
                                ( objDecl->get_init() != NULL && objDecl->get_init()->get_maybeConstructed() ));
                }

                Expression * makeCtorDtorExpr( std::string name, ObjectDecl * objDecl, std::list< Expression * > args ) {
                        UntypedExpr * expr = new UntypedExpr( new NameExpr( name ) );
                        expr->get_args().push_back( new AddressExpr( new VariableExpr( objDecl ) ) );
                        expr->get_args().splice( expr->get_args().end(), args );
                        return expr;
                }

                class InitExpander : public Visitor {
                  public:
                  InitExpander() {}
                  // ~InitExpander() {}
                        virtual void visit( SingleInit * singleInit );
                        virtual void visit( ListInit * listInit );
                        std::list< Expression * > argList;
                };

                void InitExpander::visit( SingleInit * singleInit ) {
                        argList.push_back( singleInit->get_value()->clone() );
                }

                void InitExpander::visit( ListInit * listInit ) {
                        // xxx - for now, assume no nested list inits
                        std::list<Initializer*>::iterator it = listInit->begin_initializers();
                        for ( ; it != listInit->end_initializers(); ++it ) {
                                (*it)->accept( *this );
                        }
                }

                std::list< Expression * > makeInitList( Initializer * init ) {
                        InitExpander expander;
                        maybeAccept( init, expander );
                        return expander.argList;
                }
        }

        ObjectDecl * CtorDtor::mutate( ObjectDecl * objDecl ) {
                // hands off if designated or if @=
                if ( tryConstruct( objDecl ) ) {
                        if ( inFunction ) {
                                if ( ArrayType * at = dynamic_cast< ArrayType * >( objDecl->get_type() ) ) {
                                        // call into makeArrayFunction from validate.cc to generate calls to ctor/dtor for each element of array
                                        // TODO: walk initializer and generate appropriate copy ctor if element has initializer
                                        std::list< Statement * > ctor;
                                        std::list< Statement * > dtor;

                                        SymTab::makeArrayFunction( NULL, new VariableExpr( objDecl ), at, "?{}", back_inserter( ctor ) );
                                        SymTab::makeArrayFunction( NULL, new VariableExpr( objDecl ), at, "^?{}", front_inserter( dtor ), false );

                                        // Currently makeArrayFunction produces a single Statement - a CompoundStmt
                                        // which  wraps everything that needs to happen. As such, it's technically
                                        // possible to use a Statement ** in the above calls, but this is inherently
                                        // unsafe, so instead we take the slightly less efficient route, but will be
                                        // immediately informed if somehow the above assumption is broken. In this case,
                                        // we could always wrap the list of statements at this point with a CompoundStmt,
                                        // but it seems reasonable at the moment for this to be done by makeArrayFunction
                                        // itself
                                        assert( ctor.size() == 1 );
                                        assert( dtor.size() == 1 );

                                        objDecl->set_init( new ConstructorInit( ctor.front(), dtor.front(), objDecl->get_init() ) );
                                } else {
                                        // it's sufficient to attempt to call the ctor/dtor for the given object and its initializer
                                        Expression * ctor = makeCtorDtorExpr( "?{}", objDecl, makeInitList( objDecl->get_init() ) );
                                        Expression * dtor = makeCtorDtorExpr( "^?{}", objDecl, std::list< Expression * >() );

                                        // need to remember init expression, in case no ctors exist
                                        // if ctor does exist, want to use ctor expression instead of init
                                        // push this decision to the resolver
                                        ExprStmt * ctorStmt = new ExprStmt( noLabels, ctor );
                                        ExprStmt * dtorStmt = new ExprStmt( noLabels, dtor );
                                        objDecl->set_init( new ConstructorInit( ctorStmt, dtorStmt, objDecl->get_init() ) );
                                }
                        } else {
                                // xxx - find a way to construct/destruct globals
                                // hack: implicit "static" initialization routine for each struct type? or something similar?
                                // --ties into module system
                                // this can be done by mangling main and replacing it with our own main which calls each
                                // module initialization routine in some decided order (order given in link command?)
                                // and finally calls mangled main
                        }
                }
                return objDecl;
        }

        DeclarationWithType * CtorDtor::mutate( FunctionDecl *functionDecl ) {
                // parameters should not be constructed and destructed, so don't mutate FunctionType
                bool oldInFunc = inFunction;
                mutateAll( functionDecl->get_oldDecls(), *this );
                inFunction = true;
                functionDecl->set_statements( maybeMutate( functionDecl->get_statements(), *this ) );
                inFunction = oldInFunc;
                return functionDecl;
        }

        // should not traverse into any of these declarations to find objects
        // that need to be constructed or destructed
        Declaration* CtorDtor::mutate( StructDecl *aggregateDecl ) { return aggregateDecl; }
        Declaration* CtorDtor::mutate( UnionDecl *aggregateDecl ) { return aggregateDecl; }
        Declaration* CtorDtor::mutate( EnumDecl *aggregateDecl ) { return aggregateDecl; }
        Declaration* CtorDtor::mutate( TraitDecl *aggregateDecl ) { return aggregateDecl; }
        TypeDecl* CtorDtor::mutate( TypeDecl *typeDecl ) { return typeDecl; }
        Declaration* CtorDtor::mutate( TypedefDecl *typeDecl ) { return typeDecl; }

} // namespace InitTweak

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