source: src/ControlStruct/ExceptTranslate.cc @ fa5e1aa5

//
// 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.
//
// ExceptTranslate.cc -- Conversion of exception control flow structures.
//
// Author           : Andrew Beach
// Created On       : Wed Jun 14 16:49:00 2017
// Last Modified By : Henry Xue
// Last Modified On : Tue Aug 03 10:05:51 2021
// Update Count     : 18
//

#include "ExceptTranslate.h"

#include <stddef.h>                   // for NULL
#include <cassert>                    // for assert, assertf
#include <iterator>                   // for back_inserter, inserter
#include <string>                     // for string, operator==

#include "Common/PassVisitor.h"       // for PassVisitor, WithGuards
#include "Common/SemanticError.h"     // for SemanticError
#include "Common/utility.h"           // for CodeLocation
#include "SynTree/LinkageSpec.h"      // for Cforall
#include "SynTree/Attribute.h"        // for Attribute
#include "SynTree/Constant.h"         // for Constant
#include "SynTree/Declaration.h"      // for ObjectDecl, FunctionDecl, Struc...
#include "SynTree/Expression.h"       // for UntypedExpr, ConstantExpr, Name...
#include "SynTree/Initializer.h"      // for SingleInit, ListInit
#include "SynTree/Label.h"            // for Label
#include "SynTree/Mutator.h"          // for mutateAll
#include "SynTree/Statement.h"        // for CompoundStmt, CatchStmt, ThrowStmt
#include "SynTree/Type.h"             // for FunctionType, Type, noQualifiers
#include "SynTree/DeclReplacer.h"     // for DeclReplacer
#include "SynTree/Visitor.h"          // for acceptAll

namespace ControlStruct {

        // Buricratic Helpers (Not having to do with the paritular operation.)

        typedef std::list<CatchStmt*> CatchList;

        void split( CatchList& allHandlers, CatchList& terHandlers,
                                CatchList& resHandlers ) {
                while ( !allHandlers.empty() ) {
                        CatchStmt * stmt = allHandlers.front();
                        allHandlers.pop_front();
                        if (CatchStmt::Terminate == stmt->get_kind()) {
                                terHandlers.push_back(stmt);
                        } else {
                                resHandlers.push_back(stmt);
                        }
                }
        }

        void appendDeclStmt( CompoundStmt * block, Declaration * item ) {
                block->push_back(new DeclStmt(item));
        }

        Expression * nameOf( DeclarationWithType * decl ) {
                return new VariableExpr( decl );
        }

        class ThrowMutatorCore : public WithGuards {
                ObjectDecl * terminate_handler_except;
                enum Context { NoHandler, TerHandler, ResHandler } cur_context;

                // The helper functions for code/syntree generation.
                Statement * create_either_throw(
                        ThrowStmt * throwStmt, const char * throwFunc );
                Statement * create_terminate_rethrow( ThrowStmt * throwStmt );

        public:
                ThrowMutatorCore() :
                        terminate_handler_except( nullptr ),
                        cur_context( NoHandler )
                {}

                void premutate( CatchStmt *catchStmt );
                Statement * postmutate( ThrowStmt *throwStmt );
        };

        // ThrowStmt Mutation Helpers

        Statement * ThrowMutatorCore::create_either_throw(
                        ThrowStmt * throwStmt, const char * throwFunc ) {
                // `throwFunc`( `throwStmt->get_name()` );
                UntypedExpr * call = new UntypedExpr( new NameExpr( throwFunc ) );
                call->get_args().push_back( throwStmt->get_expr() );
                throwStmt->set_expr( nullptr );
                delete throwStmt;
                return new ExprStmt( call );
        }

        Statement * ThrowMutatorCore::create_terminate_rethrow(
                        ThrowStmt *throwStmt ) {
                // { `terminate_handler_except` = 0p; __rethrow_terminate(); }
                assert( nullptr == throwStmt->get_expr() );
                assert( terminate_handler_except );

                CompoundStmt * result = new CompoundStmt();
                result->labels =  throwStmt->labels;
                result->push_back( new ExprStmt( UntypedExpr::createAssign(
                        nameOf( terminate_handler_except ),
                        new ConstantExpr( Constant::null(
                                terminate_handler_except->get_type()->clone()
                                ) )
                        ) ) );
                result->push_back( new ExprStmt(
                        new UntypedExpr( new NameExpr( "__cfaehm_rethrow_terminate" ) )
                        ) );
                delete throwStmt;
                return result;
        }

        // Visiting/Mutating Functions

        void ThrowMutatorCore::premutate( CatchStmt *catchStmt ) {
                // Validate the statement's form.
                ObjectDecl * decl = dynamic_cast<ObjectDecl *>( catchStmt->get_decl() );
                // Also checking the type would be nice.
                if ( !decl || !dynamic_cast<PointerType *>( decl->type ) ) {
                        std::string kind = (CatchStmt::Terminate == catchStmt->kind) ? "catch" : "catchResume";
                        SemanticError( catchStmt->location, kind + " must have pointer to an exception type" );
                }

                // Track the handler context.
                GuardValue( cur_context );
                if ( CatchStmt::Terminate == catchStmt->get_kind() ) {
                        cur_context = TerHandler;

                        GuardValue( terminate_handler_except );
                        terminate_handler_except = decl;
                } else {
                        cur_context = ResHandler;
                }
        }

        Statement * ThrowMutatorCore::postmutate( ThrowStmt *throwStmt ) {
                // Ignoring throwStmt->get_target() for now.
                if ( ThrowStmt::Terminate == throwStmt->get_kind() ) {
                        if ( throwStmt->get_expr() ) {
                                return create_either_throw( throwStmt, "$throw" );
                        } else if ( TerHandler == cur_context ) {
                                return create_terminate_rethrow( throwStmt );
                        } else {
                                abort("Invalid throw in %s at %i\n",
                                        throwStmt->location.filename.c_str(),
                                        throwStmt->location.first_line);
                        }
                } else {
                        if ( throwStmt->get_expr() ) {
                                return create_either_throw( throwStmt, "$throwResume" );
                        } else if ( ResHandler == cur_context ) {
                                // This has to be handled later.
                                return throwStmt;
                        } else {
                                abort("Invalid throwResume in %s at %i\n",
                                        throwStmt->location.filename.c_str(),
                                        throwStmt->location.first_line);
                        }
                }
        }

        class TryMutatorCore {
                // The built in types used in translation.
                StructDecl * except_decl;
                StructDecl * node_decl;
                StructDecl * hook_decl;

                // The many helper functions for code/syntree generation.
                CompoundStmt * take_try_block( TryStmt * tryStmt );
                FunctionDecl * create_try_wrapper( CompoundStmt * body );
                FunctionDecl * create_terminate_catch( CatchList &handlers );
                CompoundStmt * create_single_matcher(
                        DeclarationWithType * except_obj, CatchStmt * modded_handler );
                FunctionDecl * create_terminate_match( CatchList &handlers );
                CompoundStmt * create_terminate_caller( FunctionDecl * try_wrapper,
                        FunctionDecl * terminate_catch, FunctionDecl * terminate_match );
                FunctionDecl * create_resume_handler( CatchList &handlers );
                CompoundStmt * create_resume_wrapper(
                        Statement * wraps, FunctionDecl * resume_handler );
                FunctionDecl * create_finally_wrapper( TryStmt * tryStmt );
                ObjectDecl * create_finally_hook( FunctionDecl * finally_wrapper );
                Statement * create_resume_rethrow( ThrowStmt * throwStmt );

                // Types used in translation, make sure to use clone.
                // void (*function)();
                FunctionType try_func_t;
                // void (*function)(int, exception);
                FunctionType catch_func_t;
                // int (*function)(exception);
                FunctionType match_func_t;
                // bool (*function)(exception);
                FunctionType handle_func_t;
                // void (*function)(__attribute__((unused)) void *);
                FunctionType finally_func_t;

                StructInstType * create_except_type() {
                        assert( except_decl );
                        return new StructInstType( noQualifiers, except_decl );
                }
                void init_func_types();

        public:
                TryMutatorCore() :
                        except_decl( nullptr ), node_decl( nullptr ), hook_decl( nullptr ),
                        try_func_t( noQualifiers, false ),
                        catch_func_t( noQualifiers, false ),
                        match_func_t( noQualifiers, false ),
                        handle_func_t( noQualifiers, false ),
                        finally_func_t( noQualifiers, false )
                {}

                void premutate( StructDecl *structDecl );
                Statement * postmutate( TryStmt *tryStmt );
                Statement * postmutate( ThrowStmt *throwStmt );
        };

        void TryMutatorCore::init_func_types() {
                assert( except_decl );

                ObjectDecl index_obj(
                        "__handler_index",
                        Type::StorageClasses(),
                        LinkageSpec::Cforall,
                        /*bitfieldWidth*/ NULL,
                        new BasicType( noQualifiers, BasicType::SignedInt ),
                        /*init*/ NULL
                        );
                ObjectDecl exception_obj(
                        "__exception_inst",
                        Type::StorageClasses(),
                        LinkageSpec::Cforall,
                        /*bitfieldWidth*/ NULL,
                        new PointerType(
                                noQualifiers,
                                new StructInstType( noQualifiers, except_decl )
                                ),
                        /*init*/ NULL
                        );
                ObjectDecl bool_obj(
                        "__ret_bool",
                        Type::StorageClasses(),
                        LinkageSpec::Cforall,
                        /*bitfieldWidth*/ NULL,
                        new BasicType( noQualifiers, BasicType::Bool ),
                        /*init*/ NULL,
                        std::list<Attribute *>{ new Attribute( "unused" ) }
                        );
                ObjectDecl voidptr_obj(
                        "__hook",
                        Type::StorageClasses(),
                        LinkageSpec::Cforall,
                        NULL,
                        new PointerType(
                                noQualifiers,
                                new VoidType(
                                        noQualifiers
                                        ),
                                std::list<Attribute *>{ new Attribute( "unused" ) }
                                ),
                        NULL
                        );

                ObjectDecl * unused_index_obj = index_obj.clone();
                unused_index_obj->attributes.push_back( new Attribute( "unused" ) );

                catch_func_t.get_parameters().push_back( index_obj.clone() );
                catch_func_t.get_parameters().push_back( exception_obj.clone() );
                match_func_t.get_returnVals().push_back( unused_index_obj );
                match_func_t.get_parameters().push_back( exception_obj.clone() );
                handle_func_t.get_returnVals().push_back( bool_obj.clone() );
                handle_func_t.get_parameters().push_back( exception_obj.clone() );
                finally_func_t.get_parameters().push_back( voidptr_obj.clone() );
        }

        // TryStmt Mutation Helpers

        CompoundStmt * TryMutatorCore::take_try_block( TryStmt *tryStmt ) {
                CompoundStmt * block = tryStmt->get_block();
                tryStmt->set_block( nullptr );
                return block;
        }

        FunctionDecl * TryMutatorCore::create_try_wrapper(
                        CompoundStmt *body ) {

                return new FunctionDecl( "try", Type::StorageClasses(),
                        LinkageSpec::Cforall, try_func_t.clone(), body );
        }

        FunctionDecl * TryMutatorCore::create_terminate_catch(
                        CatchList &handlers ) {
                std::list<CaseStmt *> handler_wrappers;

                FunctionType *func_type = catch_func_t.clone();
                DeclarationWithType * index_obj = func_type->get_parameters().front();
                DeclarationWithType * except_obj = func_type->get_parameters().back();

                // Index 1..{number of handlers}
                int index = 0;
                CatchList::iterator it = handlers.begin();
                for ( ; it != handlers.end() ; ++it ) {
                        ++index;
                        CatchStmt * handler = *it;

                        // case `index`:
                        // {
                        //     `handler.decl` = { (virtual `decl.type`)`except` };
                        //     `handler.body`;
                        // }
                        // return;
                        CompoundStmt * block = new CompoundStmt();

                        // Just copy the exception value. (Post Validation)
                        ObjectDecl * handler_decl =
                                static_cast<ObjectDecl *>( handler->get_decl() );
                        ObjectDecl * local_except = handler_decl->clone();
                        VirtualCastExpr * vcex = new VirtualCastExpr(
                                nameOf( except_obj ),
                                local_except->get_type()
                                );
                        vcex->location = handler->location;
                        local_except->set_init( new ListInit({ new SingleInit( vcex ) }) );
                        block->push_back( new DeclStmt( local_except ) );

                        // Add the cleanup attribute.
                        local_except->get_attributes().push_back( new Attribute(
                                "cleanup",
                                { new NameExpr( "__cfaehm_cleanup_terminate" ) }
                                ) );

                        // Update variables in the body to point to this local copy.
                        {
                                DeclReplacer::DeclMap mapping;
                                mapping[ handler_decl ] = local_except;
                                DeclReplacer::replace( handler->body, mapping );
                        }

                        block->push_back( handler->body );
                        handler->body = nullptr;

                        std::list<Statement *> caseBody
                                        { block, new ReturnStmt( nullptr ) };
                        handler_wrappers.push_back( new CaseStmt(
                                new ConstantExpr( Constant::from_int( index ) ),
                                caseBody
                                ) );
                }
                // TODO: Some sort of meaningful error on default perhaps?

                std::list<Statement*> stmt_handlers;
                while ( !handler_wrappers.empty() ) {
                        stmt_handlers.push_back( handler_wrappers.front() );
                        handler_wrappers.pop_front();
                }

                SwitchStmt * handler_lookup = new SwitchStmt(
                        nameOf( index_obj ),
                        stmt_handlers
                        );
                CompoundStmt * body = new CompoundStmt();
                body->push_back( handler_lookup );

                return new FunctionDecl("catch", Type::StorageClasses(),
                        LinkageSpec::Cforall, func_type, body);
        }

        // Create a single check from a moddified handler.
        // except_obj is referenced, modded_handler will be freed.
        CompoundStmt * TryMutatorCore::create_single_matcher(
                        DeclarationWithType * except_obj, CatchStmt * modded_handler ) {
                // {
                //     `modded_handler.decl`
                //     if ( `decl.name = (virtual `decl.type`)`except`
                //             [&& `modded_handler.cond`] ) {
                //         `modded_handler.body`
                //     }
                // }

                CompoundStmt * block = new CompoundStmt();

                // Local Declaration
                ObjectDecl * local_except =
                        dynamic_cast<ObjectDecl *>( modded_handler->get_decl() );
                assert( local_except );
                block->push_back( new DeclStmt( local_except ) );

                // Check for type match.
                VirtualCastExpr * vcex = new VirtualCastExpr(
                        nameOf( except_obj ),
                        local_except->get_type()->clone()
                        );
                vcex->location = modded_handler->location;
                Expression * cond = UntypedExpr::createAssign(
                        nameOf( local_except ), vcex );

                // Add the check on the conditional if it is provided.
                if ( modded_handler->get_cond() ) {
                        cond = new LogicalExpr( cond, modded_handler->get_cond() );
                }
                // Construct the match condition.
                block->push_back( new IfStmt(
                        cond, modded_handler->get_body(), nullptr ) );

                modded_handler->set_decl( nullptr );
                modded_handler->set_cond( nullptr );
                modded_handler->set_body( nullptr );
                delete modded_handler;
                return block;
        }

        FunctionDecl * TryMutatorCore::create_terminate_match(
                        CatchList &handlers ) {
                // int match(exception * except) {
                //     HANDLER WRAPPERS { return `index`; }
                // }

                CompoundStmt * body = new CompoundStmt();

                FunctionType * func_type = match_func_t.clone();
                DeclarationWithType * except_obj = func_type->get_parameters().back();

                // Index 1..{number of handlers}
                int index = 0;
                CatchList::iterator it;
                for ( it = handlers.begin() ; it != handlers.end() ; ++it ) {
                        ++index;
                        CatchStmt * handler = *it;

                        // Body should have been taken by create_terminate_catch.
                        assert( nullptr == handler->get_body() );

                        // Create new body.
                        handler->set_body( new ReturnStmt(
                                new ConstantExpr( Constant::from_int( index ) ) ) );

                        // Create the handler.
                        body->push_back( create_single_matcher( except_obj, handler ) );
                        *it = nullptr;
                }

                body->push_back( new ReturnStmt(
                        new ConstantExpr( Constant::from_int( 0 ) ) ) );

                return new FunctionDecl("match", Type::StorageClasses(),
                        LinkageSpec::Cforall, func_type, body);
        }

        CompoundStmt * TryMutatorCore::create_terminate_caller(
                        FunctionDecl * try_wrapper,
                        FunctionDecl * terminate_catch,
                        FunctionDecl * terminate_match ) {
                // { __cfaehm_try_terminate(`try`, `catch`, `match`); }

                UntypedExpr * caller = new UntypedExpr( new NameExpr(
                        "__cfaehm_try_terminate" ) );
                std::list<Expression *>& args = caller->get_args();
                args.push_back( nameOf( try_wrapper ) );
                args.push_back( nameOf( terminate_catch ) );
                args.push_back( nameOf( terminate_match ) );

                CompoundStmt * callStmt = new CompoundStmt();
                callStmt->push_back( new ExprStmt( caller ) );
                return callStmt;
        }

        FunctionDecl * TryMutatorCore::create_resume_handler(
                        CatchList &handlers ) {
                // bool handle(exception * except) {
                //     HANDLER WRAPPERS { `hander->body`; return true; }
                // }
                CompoundStmt * body = new CompoundStmt();

                FunctionType * func_type = handle_func_t.clone();
                DeclarationWithType * except_obj = func_type->get_parameters().back();

                CatchList::iterator it;
                for ( it = handlers.begin() ; it != handlers.end() ; ++it ) {
                        CatchStmt * handler = *it;

                        // Modifiy body.
                        CompoundStmt * handling_code =
                                dynamic_cast<CompoundStmt*>( handler->get_body() );
                        if ( ! handling_code ) {
                                handling_code = new CompoundStmt();
                                handling_code->push_back( handler->get_body() );
                        }
                        handling_code->push_back( new ReturnStmt(
                                new ConstantExpr( Constant::from_bool( true ) ) ) );
                        handler->set_body( handling_code );

                        // Create the handler.
                        body->push_back( create_single_matcher( except_obj, handler ) );
                        *it = nullptr;
                }

                body->push_back( new ReturnStmt(
                        new ConstantExpr( Constant::from_bool( false ) ) ) );

                return new FunctionDecl("handle", Type::StorageClasses(),
                        LinkageSpec::Cforall, func_type, body);
        }

        CompoundStmt * TryMutatorCore::create_resume_wrapper(
                        Statement * wraps,
                        FunctionDecl * resume_handler ) {
                CompoundStmt * body = new CompoundStmt();

                // struct __try_resume_node __resume_node
                //      __attribute__((cleanup( __cfaehm_try_resume_cleanup )));
                // ** unwinding of the stack here could cause problems **
                // ** however I don't think that can happen currently **
                // __cfaehm_try_resume_setup( &__resume_node, resume_handler );

                std::list< Attribute * > attributes;
                {
                        std::list< Expression * > attr_params;
                        attr_params.push_back( new NameExpr(
                                "__cfaehm_try_resume_cleanup" ) );
                        attributes.push_back( new Attribute( "cleanup", attr_params ) );
                }

                ObjectDecl * obj = new ObjectDecl(
                        "__resume_node",
                        Type::StorageClasses(),
                        LinkageSpec::Cforall,
                        nullptr,
                        new StructInstType(
                                Type::Qualifiers(),
                                node_decl
                                ),
                        nullptr,
                        attributes
                        );
                appendDeclStmt( body, obj );

                UntypedExpr *setup = new UntypedExpr( new NameExpr(
                        "__cfaehm_try_resume_setup" ) );
                setup->get_args().push_back( new AddressExpr( nameOf( obj ) ) );
                setup->get_args().push_back( nameOf( resume_handler ) );

                body->push_back( new ExprStmt( setup ) );

                body->push_back( wraps );
                return body;
        }

        FunctionDecl * TryMutatorCore::create_finally_wrapper(
                        TryStmt * tryStmt ) {
                // void finally() { `finally->block` }
                FinallyStmt * finally = tryStmt->get_finally();
                CompoundStmt * body = finally->get_block();
                finally->set_block( nullptr );
                delete finally;
                tryStmt->set_finally( nullptr );

                return new FunctionDecl("finally", Type::StorageClasses(),
                        LinkageSpec::Cforall, finally_func_t.clone(), body);
        }

        ObjectDecl * TryMutatorCore::create_finally_hook(
                        FunctionDecl * finally_wrapper ) {
                // struct __cfaehm_cleanup_hook __finally_hook
                //      __attribute__((cleanup( `finally_wrapper` )));

                // Make Cleanup Attribute.
                std::list< Attribute * > attributes;
                {
                        std::list< Expression * > attr_params;
                        attr_params.push_back( nameOf( finally_wrapper ) );
                        attributes.push_back( new Attribute( "cleanup", attr_params ) );
                }

                return new ObjectDecl(
                        "__finally_hook",
                        Type::StorageClasses(),
                        LinkageSpec::Cforall,
                        nullptr,
                        new StructInstType(
                                noQualifiers,
                                hook_decl
                                ),
                        nullptr,
                        attributes
                        );
        }

        Statement * TryMutatorCore::create_resume_rethrow( ThrowStmt *throwStmt ) {
                // return false;
                Statement * result = new ReturnStmt(
                        new ConstantExpr( Constant::from_bool( false ) )
                        );
                result->labels = throwStmt->labels;
                delete throwStmt;
                return result;
        }

        // Visiting/Mutating Functions
        void TryMutatorCore::premutate( StructDecl *structDecl ) {
                if ( !structDecl->has_body() ) {
                        // Skip children?
                        return;
                } else if ( structDecl->get_name() == "__cfaehm_base_exception_t" ) {
                        assert( nullptr == except_decl );
                        except_decl = structDecl;
                        init_func_types();
                } else if ( structDecl->get_name() == "__cfaehm_try_resume_node" ) {
                        assert( nullptr == node_decl );
                        node_decl = structDecl;
                } else if ( structDecl->get_name() == "__cfaehm_cleanup_hook" ) {
                        assert( nullptr == hook_decl );
                        hook_decl = structDecl;
                }
        }

        Statement * TryMutatorCore::postmutate( TryStmt *tryStmt ) {
                assert( except_decl );
                assert( node_decl );
                assert( hook_decl );

                // Generate a prefix for the function names?

                CompoundStmt * block = new CompoundStmt();
                CompoundStmt * inner = take_try_block( tryStmt );

                if ( tryStmt->get_finally() ) {
                        // Define the helper function.
                        FunctionDecl * finally_block =
                                create_finally_wrapper( tryStmt );
                        appendDeclStmt( block, finally_block );
                        // Create and add the finally cleanup hook.
                        appendDeclStmt( block, create_finally_hook( finally_block ) );
                }

                CatchList termination_handlers;
                CatchList resumption_handlers;
                split( tryStmt->get_catchers(),
                           termination_handlers, resumption_handlers );

                if ( resumption_handlers.size() ) {
                        // Define the helper function.
                        FunctionDecl * resume_handler =
                                create_resume_handler( resumption_handlers );
                        appendDeclStmt( block, resume_handler );
                        // Prepare hooks
                        inner = create_resume_wrapper( inner, resume_handler );
                }

                if ( termination_handlers.size() ) {
                        // Define the three helper functions.
                        FunctionDecl * try_wrapper = create_try_wrapper( inner );
                        appendDeclStmt( block, try_wrapper );
                        FunctionDecl * terminate_catch =
                                create_terminate_catch( termination_handlers );
                        appendDeclStmt( block, terminate_catch );
                        FunctionDecl * terminate_match =
                                create_terminate_match( termination_handlers );
                        appendDeclStmt( block, terminate_match );
                        // Build the call to the try wrapper.
                        inner = create_terminate_caller(
                                try_wrapper, terminate_catch, terminate_match );
                }

                // Embed the try block.
                block->push_back( inner );

                return block;
        }

        Statement * TryMutatorCore::postmutate( ThrowStmt *throwStmt ) {
                // Only valid `throwResume;` statements should remain. (2/3 checks)
                assert( ThrowStmt::Resume == throwStmt->kind && ! throwStmt->expr );
                return create_resume_rethrow( throwStmt );
        }

        void translateThrows( std::list< Declaration *> & translationUnit ) {
                PassVisitor<ThrowMutatorCore> translator;
                mutateAll( translationUnit, translator );
        }

        void translateTries( std::list< Declaration *> & translationUnit ) {
                PassVisitor<TryMutatorCore> translator;
                mutateAll( translationUnit, translator );
        }
}