source: src/AST/Pass.proto.hpp @ 21baa40

//
// Cforall Version 1.0.0 Copyright (C) 2019 University of Waterloo
//
// The contents of this file are covered under the licence agreement in the
// file "LICENCE" distributed with Cforall.
//
// Pass.impl.hpp --
//
// Author           : Thierry Delisle
// Created On       : Thu May 09 15::37::05 2019
// Last Modified By :
// Last Modified On :
// Update Count     :
//

#pragma once
// IWYU pragma: private, include "Pass.hpp"

namespace ast {
template<typename pass_type>
class Pass;

namespace __pass {
        typedef std::function<void( void * )> cleanup_func_t;
        typedef std::function<void( cleanup_func_t, void * )> at_cleanup_t;


        // boolean reference that may be null
        // either refers to a boolean value or is null and returns true
        class bool_ref {
        public:
                bool_ref() = default;
                ~bool_ref() = default;

                operator bool() { return m_ref ? *m_ref : true; }
                bool operator=( bool val ) { assert(m_ref); return *m_ref = val; }

        private:

                friend class visit_children_guard;

                bool * set( bool * val ) {
                        bool * prev = m_ref;
                        m_ref = val;
                        return prev;
                }

                bool * m_ref = nullptr;
        };

        // Implementation of the guard value
        // Created inside the visit scope
        class guard_value {
        public:
                /// Push onto the cleanup
                guard_value( at_cleanup_t * at_cleanup ) {
                        if( at_cleanup ) {
                                *at_cleanup = [this]( cleanup_func_t && func, void* val ) {
                                        push( std::move( func ), val );
                                };
                        }
                }

                ~guard_value() {
                        while( !cleanups.empty() ) {
                                auto& cleanup = cleanups.top();
                                cleanup.func( cleanup.val );
                                cleanups.pop();
                        }
                }

                void push( cleanup_func_t && func, void* val ) {
                        cleanups.emplace( std::move(func), val );
                }

        private:
                struct cleanup_t {
                        cleanup_func_t func;
                        void * val;

                        cleanup_t( cleanup_func_t&& func, void * val ) : func(func), val(val) {}
                };

                std::stack< cleanup_t > cleanups;
        };

        // Guard structure implementation for whether or not children should be visited
        class visit_children_guard {
        public:

                visit_children_guard( bool_ref * ref )
                        : m_val ( true )
                        , m_prev( ref ? ref->set( &m_val ) : nullptr )
                        , m_ref ( ref )
                {}

                ~visit_children_guard() {
                        if( m_ref ) {
                                m_ref->set( m_prev );
                        }
                }

                operator bool() { return m_val; }

        private:
                bool       m_val;
                bool     * m_prev;
                bool_ref * m_ref;
        };

        /// "Short hand" to check if this is a valid previsit function
        /// Mostly used to make the static_assert look (and print) prettier
        template<typename pass_t, typename node_t>
        struct is_valid_previsit {
                using ret_t = decltype( ((pass_t*)nullptr)->previsit( (const node_t *)nullptr ) );

                static constexpr bool value = std::is_void< ret_t >::value ||
                        std::is_base_of<const node_t, typename std::remove_pointer<ret_t>::type >::value;
        };

        /// Used by previsit implementation
        /// We need to reassign the result to 'node', unless the function
        /// returns void, then we just leave 'node' unchanged
        template<bool is_void>
        struct __assign;

        template<>
        struct __assign<true> {
                template<typename pass_t, typename node_t>
                static inline void result( pass_t & pass, const node_t * & node ) {
                        pass.previsit( node );
                }
        };

        template<>
        struct __assign<false> {
                template<typename pass_t, typename node_t>
                static inline void result( pass_t & pass, const node_t * & node ) {
                        node = pass.previsit( node );
                        assertf(node, "Previsit must not return NULL");
                }
        };

        /// Used by postvisit implementation
        /// We need to return the result unless the function
        /// returns void, then we just return the original node
        template<bool is_void>
        struct __return;

        template<>
        struct __return<true> {
                template<typename pass_t, typename node_t>
                static inline const node_t * result( pass_t & pass, const node_t * & node ) {
                        pass.postvisit( node );
                        return node;
                }
        };

        template<>
        struct __return<false> {
                template<typename pass_t, typename node_t>
                static inline auto result( pass_t & pass, const node_t * & node ) {
                        return pass.postvisit( node );
                }
        };

        //-------------------------------------------------------------------------------------------------------------------------------------------------------------------------
        // Deep magic (a.k.a template meta programming) to make the templated visitor work
        // Basically the goal is to make 2 previsit
        // 1 - Use when a pass implements a valid previsit. This uses overloading which means the any overload of
        //     'pass.previsit( node )' that compiles will be used for that node for that type
        //     This requires that this option only compile for passes that actually define an appropriate visit.
        //     SFINAE will make sure the compilation errors in this function don't halt the build.
        //     See http://en.cppreference.com/w/cpp/language/sfinae for details on SFINAE
        // 2 - Since the first implementation might not be specilizable, the second implementation exists and does nothing.
        //     This is needed only to eliminate the need for passes to specify any kind of handlers.
        //     The second implementation only works because it has a lower priority. This is due to the bogus last parameter.
        //     The second implementation takes a long while the first takes an int. Since the caller always passes an literal 0
        //     the first implementation takes priority in regards to overloading.
        //-------------------------------------------------------------------------------------------------------------------------------------------------------------------------
        // PreVisit : may mutate the pointer passed in if the node is mutated in the previsit call
        template<typename pass_t, typename node_t>
        static inline auto previsit( pass_t & pass, const node_t * & node, int ) -> decltype( pass.previsit( node ), void() ) {
                static_assert(
                        is_valid_previsit<pass_t, node_t>::value,
                        "Previsit may not change the type of the node. It must return its paremeter or void."
                );

                __assign<
                        std::is_void<
                                decltype( pass.previsit( node ) )
                        >::value
                >::result( pass, node );
        }

        template<typename pass_t, typename node_t>
        static inline auto previsit( pass_t &, const node_t *, long ) {}

        // PostVisit : never mutates the passed pointer but may return a different node
        template<typename pass_t, typename node_t>
        static inline auto postvisit( pass_t & pass, const node_t * node, int ) ->
                decltype( pass.postvisit( node ), node->accept( *(Visitor*)nullptr ) )
        {
                return __return<
                        std::is_void<
                                decltype( pass.postvisit( node ) )
                        >::value
                >::result( pass, node );
        }

        template<typename pass_t, typename node_t>
        static inline const node_t * postvisit( pass_t &, const node_t * node, long ) { return node; }

        //-------------------------------------------------------------------------------------------------------------------------------------------------------------------------
        // Deep magic (a.k.a template meta programming) continued
        // To make the templated visitor be more expressive, we allow 'accessories' : classes/structs the implementation can inherit
        // from in order to get extra functionallity for example
        // class ErrorChecker : WithShortCircuiting { ... };
        // Pass<ErrorChecker> checker;
        // this would define a pass that uses the templated visitor with the additionnal feature that it has short circuiting
        // Note that in all cases the accessories are not required but guarantee the requirements of the feature is matched
        //-------------------------------------------------------------------------------------------------------------------------------------------------------------------------
        // For several accessories, the feature is enabled by detecting that a specific field is present
        // Use a macro the encapsulate the logic of detecting a particular field
        // The type is not strictly enforced but does match the accessory
        #define FIELD_PTR( name, default_type ) \
        template< typename pass_t > \
        static inline auto name( pass_t & pass, int ) -> decltype( &pass.name ) { return &pass.name; } \
        \
        template< typename pass_t > \
        static inline default_type * name( pass_t &, long ) { return nullptr; }

        // List of fields and their expected types
        FIELD_PTR( env, const ast::TypeSubstitution * )
        FIELD_PTR( stmtsToAddBefore, std::list< ast::ptr< ast::Stmt > > )
        FIELD_PTR( stmtsToAddAfter , std::list< ast::ptr< ast::Stmt > > )
        FIELD_PTR( declsToAddBefore, std::list< ast::ptr< ast::Decl > > )
        FIELD_PTR( declsToAddAfter , std::list< ast::ptr< ast::Decl > > )
        FIELD_PTR( visit_children, __pass::bool_ref )
        FIELD_PTR( at_cleanup, __pass::at_cleanup_t )
        FIELD_PTR( visitor, ast::Pass<pass_t> * const )

        // Remove the macro to make sure we don't clash
        #undef FIELD_PTR

        // Another feature of the templated visitor is that it calls beginScope()/endScope() for compound statement.
        // All passes which have such functions are assumed desire this behaviour
        // detect it using the same strategy
        namespace scope {
                template<typename pass_t>
                static inline auto enter( pass_t & pass, int ) -> decltype( pass.beginScope(), void() ) {
                        pass.beginScope();
                }

                template<typename pass_t>
                static inline void enter( pass_t &, long ) {}

                template<typename pass_t>
                static inline auto leave( pass_t & pass, int ) -> decltype( pass.endScope(), void() ) {
                        pass.endScope();
                }

                template<typename pass_t>
                static inline void leave( pass_t &, long ) {}
        };

        // Finally certain pass desire an up to date symbol table automatically
        // detect the presence of a member name `symtab` and call all the members appropriately
        namespace symtab {
                // Some simple scoping rules
                template<typename pass_t>
                static inline auto enter( pass_t & pass, int ) -> decltype( pass.symtab.enterScope(), void() ) {
                        pass.symtab.enterScope();
                }

                template<typename pass_t>
                static inline auto enter( pass_t &, long ) {}

                template<typename pass_t>
                static inline auto leave( pass_t & pass, int ) -> decltype( pass.symtab.leaveScope(), void() ) {
                        pass.symtab.leaveScope();
                }

                template<typename pass_t>
                static inline auto leave( pass_t &, long ) {}

                // The symbol table has 2 kind of functions mostly, 1 argument and 2 arguments
                // Create macro to condense these common patterns
                #define SYMTAB_FUNC1( func, type ) \
                template<typename pass_t> \
                static inline auto func( pass_t & pass, int, type arg ) -> decltype( pass.symtab.func( arg ), void() ) {\
                        pass.symtab.func( arg ); \
                } \
                \
                template<typename pass_t> \
                static inline void func( pass_t &, long, type ) {}

                #define SYMTAB_FUNC2( func, type1, type2 ) \
                template<typename pass_t> \
                static inline auto func( pass_t & pass, int, type1 arg1, type2 arg2 ) -> decltype( pass.symtab.func( arg1, arg2 ), void () ) {\
                        pass.symtab.func( arg1, arg2 ); \
                } \
                        \
                template<typename pass_t> \
                static inline void func( pass_t &, long, type1, type2 ) {}

                SYMTAB_FUNC1( addId     , const DeclWithType *  );
                SYMTAB_FUNC1( addType   , const NamedTypeDecl * );
                SYMTAB_FUNC1( addStruct , const StructDecl *    );
                SYMTAB_FUNC1( addEnum   , const EnumDecl *      );
                SYMTAB_FUNC1( addUnion  , const UnionDecl *     );
                SYMTAB_FUNC1( addTrait  , const TraitDecl *     );
                SYMTAB_FUNC2( addWith   , const std::vector< ptr<Expr> > &, const Node * );

                // A few extra functions have more complicated behaviour, they are hand written
                template<typename pass_t>
                static inline auto addStructFwd( pass_t & pass, int, const ast::StructDecl * decl ) -> decltype( pass.symtab.addStruct( decl ), void() ) {
                        ast::StructDecl * fwd = new ast::StructDecl( decl->location, decl->name );
                        fwd->params = decl->params;
                        pass.symtab.addStruct( fwd );
                }

                template<typename pass_t>
                static inline void addStructFwd( pass_t &, long, const ast::StructDecl * ) {}

                template<typename pass_t>
                static inline auto addUnionFwd( pass_t & pass, int, const ast::UnionDecl * decl ) -> decltype( pass.symtab.addUnion( decl ), void() ) {
                        UnionDecl * fwd = new UnionDecl( decl->location, decl->name );
                        fwd->params = decl->params;
                        pass.symtab.addUnion( fwd );
                }

                template<typename pass_t>
                static inline void addUnionFwd( pass_t &, long, const ast::UnionDecl * ) {}

                template<typename pass_t>
                static inline auto addStruct( pass_t & pass, int, const std::string & str ) -> decltype( pass.symtab.addStruct( str ), void() ) {
                        if ( ! pass.symtab.lookupStruct( str ) ) {
                                pass.symtab.addStruct( str );
                        }
                }

                template<typename pass_t>
                static inline void addStruct( pass_t &, long, const std::string & ) {}

                template<typename pass_t>
                static inline auto addUnion( pass_t & pass, int, const std::string & str ) -> decltype( pass.symtab.addUnion( str ), void() ) {
                        if ( ! pass.symtab.lookupUnion( str ) ) {
                                pass.symtab.addUnion( str );
                        }
                }

                template<typename pass_t>
                static inline void addUnion( pass_t &, long, const std::string & ) {}

                #undef SYMTAB_FUNC1
                #undef SYMTAB_FUNC2
        };
};
};