source: src/Concurrency/Keywords.cc @ 751e2eb

//
// Cforall Version 1.0.0 Copyright (C) 2016 University of Waterloo
//
// The contents of this file are covered under the licence agreement in the
// file "LICENCE" distributed with Cforall.
//
// Keywords.cc --
//
// Author           : Thierry Delisle
// Created On       : Mon Mar 13 12:41:22 2017
// Last Modified By :
// Last Modified On :
// Update Count     : 10
//

#include "Concurrency/Keywords.h"

#include <cassert>                        // for assert
#include <string>                         // for string, operator==

#include <iostream>

#include "Common/Examine.h"               // for isMainFor
#include "Common/PassVisitor.h"           // for PassVisitor
#include "Common/SemanticError.h"         // for SemanticError
#include "Common/utility.h"               // for deleteAll, map_range
#include "CodeGen/OperatorTable.h"        // for isConstructor
#include "ControlStruct/LabelGenerator.h" // for LebelGenerator
#include "InitTweak/InitTweak.h"          // for getPointerBase
#include "SynTree/LinkageSpec.h"          // for Cforall
#include "SynTree/Constant.h"             // for Constant
#include "SynTree/Declaration.h"          // for StructDecl, FunctionDecl, ObjectDecl
#include "SynTree/Expression.h"           // for VariableExpr, ConstantExpr, Untype...
#include "SynTree/Initializer.h"          // for SingleInit, ListInit, Initializer ...
#include "SynTree/Label.h"                // for Label
#include "SynTree/Statement.h"            // for CompoundStmt, DeclStmt, ExprStmt
#include "SynTree/Type.h"                 // for StructInstType, Type, PointerType
#include "SynTree/Visitor.h"              // for Visitor, acceptAll
#include "Virtual/Tables.h"

class Attribute;

namespace Concurrency {
        inline static std::string getVTableName( std::string const & exception_name ) {
                return exception_name.empty() ? std::string() : Virtual::vtableTypeName(exception_name);
        }

        // Only detects threads constructed with the keyword thread.
        inline static bool isThread( DeclarationWithType * decl ) {
                Type * baseType = decl->get_type()->stripDeclarator();
                StructInstType * instType = dynamic_cast<StructInstType *>( baseType );
                if ( nullptr == instType ) { return false; }
                return instType->baseStruct->is_thread();
        }

        //=============================================================================================
        // Pass declarations
        //=============================================================================================

        //-----------------------------------------------------------------------------
        //Handles sue type declarations :
        // sue MyType {                             struct MyType {
        //      int data;                                  int data;
        //      a_struct_t more_data;                      a_struct_t more_data;
        //                                =>             NewField_t newField;
        // };                                        };
        //                                           static inline NewField_t * getter_name( MyType * this ) { return &this->newField; }
        //
        class ConcurrentSueKeyword : public WithDeclsToAdd {
          public:

                ConcurrentSueKeyword( std::string&& type_name, std::string&& field_name,
                        std::string&& getter_name, std::string&& context_error, std::string&& exception_name,
                        bool needs_main, AggregateDecl::Aggregate cast_target ) :
                  type_name( type_name ), field_name( field_name ), getter_name( getter_name ),
                  context_error( context_error ), exception_name( exception_name ),
                  vtable_name( getVTableName( exception_name ) ),
                  needs_main( needs_main ), cast_target( cast_target ) {}

                virtual ~ConcurrentSueKeyword() {}

                Declaration * postmutate( StructDecl * decl );
                DeclarationWithType * postmutate( FunctionDecl * decl );

                void handle( StructDecl * );
                void addVtableForward( StructDecl * );
                FunctionDecl * forwardDeclare( StructDecl * );
                ObjectDecl * addField( StructDecl * );
                void addRoutines( ObjectDecl *, FunctionDecl * );

                virtual bool is_target( StructDecl * decl ) = 0;

                Expression * postmutate( KeywordCastExpr * cast );

          private:
                const std::string type_name;
                const std::string field_name;
                const std::string getter_name;
                const std::string context_error;
                const std::string exception_name;
                const std::string vtable_name;
                bool needs_main;
                AggregateDecl::Aggregate cast_target;

                StructDecl   * type_decl = nullptr;
                FunctionDecl * dtor_decl = nullptr;
                StructDecl * except_decl = nullptr;
                StructDecl * vtable_decl = nullptr;
        };


        //-----------------------------------------------------------------------------
        //Handles thread type declarations :
        // thread Mythread {                         struct MyThread {
        //      int data;                                  int data;
        //      a_struct_t more_data;                      a_struct_t more_data;
        //                                =>             $thread __thrd_d;
        // };                                        };
        //                                           static inline $thread * get_thread( MyThread * this ) { return &this->__thrd_d; }
        //
        class ThreadKeyword final : public ConcurrentSueKeyword {
          public:

                ThreadKeyword() : ConcurrentSueKeyword(
                        "$thread",
                        "__thrd",
                        "get_thread",
                        "thread keyword requires threads to be in scope, add #include <thread.hfa>\n",
                        "ThreadCancelled",
                        true,
                        AggregateDecl::Thread
                )
                {}

                virtual ~ThreadKeyword() {}

                virtual bool is_target( StructDecl * decl ) override final { return decl->is_thread(); }

                static void implement( std::list< Declaration * > & translationUnit ) {
                        PassVisitor< ThreadKeyword > impl;
                        mutateAll( translationUnit, impl );
                }
        };

        //-----------------------------------------------------------------------------
        //Handles coroutine type declarations :
        // coroutine MyCoroutine {                   struct MyCoroutine {
        //      int data;                                  int data;
        //      a_struct_t more_data;                      a_struct_t more_data;
        //                                =>             $coroutine __cor_d;
        // };                                        };
        //                                           static inline $coroutine * get_coroutine( MyCoroutine * this ) { return &this->__cor_d; }
        //
        class CoroutineKeyword final : public ConcurrentSueKeyword {
          public:

                CoroutineKeyword() : ConcurrentSueKeyword(
                        "$coroutine",
                        "__cor",
                        "get_coroutine",
                        "coroutine keyword requires coroutines to be in scope, add #include <coroutine.hfa>\n",
                        "CoroutineCancelled",
                        true,
                        AggregateDecl::Coroutine
                )
                {}

                virtual ~CoroutineKeyword() {}

                virtual bool is_target( StructDecl * decl ) override final { return decl->is_coroutine(); }

                static void implement( std::list< Declaration * > & translationUnit ) {
                        PassVisitor< CoroutineKeyword > impl;
                        mutateAll( translationUnit, impl );
                }
        };



        //-----------------------------------------------------------------------------
        //Handles monitor type declarations :
        // monitor MyMonitor {                       struct MyMonitor {
        //      int data;                                  int data;
        //      a_struct_t more_data;                      a_struct_t more_data;
        //                                =>             $monitor __mon_d;
        // };                                        };
        //                                           static inline $monitor * get_coroutine( MyMonitor * this ) { return &this->__cor_d; }
        //
        class MonitorKeyword final : public ConcurrentSueKeyword {
          public:

                MonitorKeyword() : ConcurrentSueKeyword(
                        "$monitor",
                        "__mon",
                        "get_monitor",
                        "monitor keyword requires monitors to be in scope, add #include <monitor.hfa>\n",
                        "",
                        false,
                        AggregateDecl::Monitor
                )
                {}

                virtual ~MonitorKeyword() {}

                virtual bool is_target( StructDecl * decl ) override final { return decl->is_monitor(); }

                static void implement( std::list< Declaration * > & translationUnit ) {
                        PassVisitor< MonitorKeyword > impl;
                        mutateAll( translationUnit, impl );
                }
        };

        //-----------------------------------------------------------------------------
        //Handles generator type declarations :
        // generator MyGenerator {                   struct MyGenerator {
        //      int data;                                  int data;
        //      a_struct_t more_data;                      a_struct_t more_data;
        //                                =>             int __gen_next;
        // };                                        };
        //
        class GeneratorKeyword final : public ConcurrentSueKeyword {
          public:

                GeneratorKeyword() : ConcurrentSueKeyword(
                        "$generator",
                        "__generator_state",
                        "get_generator",
                        "Unable to find builtin type $generator\n",
                        "",
                        true,
                        AggregateDecl::Generator
                )
                {}

                virtual ~GeneratorKeyword() {}

                virtual bool is_target( StructDecl * decl ) override final { return decl->is_generator(); }

                static void implement( std::list< Declaration * > & translationUnit ) {
                        PassVisitor< GeneratorKeyword > impl;
                        mutateAll( translationUnit, impl );
                }
        };


        //-----------------------------------------------------------------------------
        class SuspendKeyword final : public WithStmtsToAdd, public WithGuards {
        public:
                SuspendKeyword() = default;
                virtual ~SuspendKeyword() = default;

                void  premutate( FunctionDecl * );
                DeclarationWithType * postmutate( FunctionDecl * );

                Statement * postmutate( SuspendStmt * );

                static void implement( std::list< Declaration * > & translationUnit ) {
                        PassVisitor< SuspendKeyword > impl;
                        mutateAll( translationUnit, impl );
                }

        private:
                bool is_real_suspend( FunctionDecl * );

                Statement * make_generator_suspend( SuspendStmt * );
                Statement * make_coroutine_suspend( SuspendStmt * );

                struct LabelPair {
                        Label obj;
                        int   idx;
                };

                LabelPair make_label() {
                        labels.push_back( gen.newLabel("generator") );
                        return { labels.back(), int(labels.size()) };
                }

                DeclarationWithType * in_generator = nullptr;
                FunctionDecl * decl_suspend = nullptr;
                std::vector<Label> labels;
                ControlStruct::LabelGenerator & gen = *ControlStruct::LabelGenerator::getGenerator();
        };

        //-----------------------------------------------------------------------------
        //Handles mutex routines definitions :
        // void foo( A * mutex a, B * mutex b,  int i ) {                  void foo( A * a, B * b,  int i ) {
        //                                                                       $monitor * __monitors[] = { get_monitor(a), get_monitor(b) };
        //                                                                       monitor_guard_t __guard = { __monitors, 2 };
        //    /*Some code*/                                       =>           /*Some code*/
        // }                                                               }
        //
        class MutexKeyword final {
          public:

                void postvisit( FunctionDecl * decl );
                void postvisit(   StructDecl * decl );

                std::list<DeclarationWithType*> findMutexArgs( FunctionDecl*, bool & first );
                void validate( DeclarationWithType * );
                void addDtorStatements( FunctionDecl* func, CompoundStmt *, const std::list<DeclarationWithType * > &);
                void addStatements( FunctionDecl* func, CompoundStmt *, const std::list<DeclarationWithType * > &);
                void addThreadDtorStatements( FunctionDecl* func, CompoundStmt * body, const std::list<DeclarationWithType * > & args );

                static void implement( std::list< Declaration * > & translationUnit ) {
                        PassVisitor< MutexKeyword > impl;
                        acceptAll( translationUnit, impl );
                }

          private:
                StructDecl* monitor_decl = nullptr;
                StructDecl* guard_decl = nullptr;
                StructDecl* dtor_guard_decl = nullptr;
                StructDecl* thread_guard_decl = nullptr;

                static std::unique_ptr< Type > generic_func;
        };

        std::unique_ptr< Type > MutexKeyword::generic_func = std::unique_ptr< Type >(
                new FunctionType(
                        noQualifiers,
                        true
                )
        );

        //-----------------------------------------------------------------------------
        //Handles mutex routines definitions :
        // void foo( A * mutex a, B * mutex b,  int i ) {                  void foo( A * a, B * b,  int i ) {
        //                                                                       $monitor * __monitors[] = { get_monitor(a), get_monitor(b) };
        //                                                                       monitor_guard_t __guard = { __monitors, 2 };
        //    /*Some code*/                                       =>           /*Some code*/
        // }                                                               }
        //
        class ThreadStarter final {
          public:

                void postvisit( FunctionDecl * decl );
                void previsit ( StructDecl   * decl );

                void addStartStatement( FunctionDecl * decl, DeclarationWithType * param );

                static void implement( std::list< Declaration * > & translationUnit ) {
                        PassVisitor< ThreadStarter > impl;
                        acceptAll( translationUnit, impl );
                }

          private :
                bool thread_ctor_seen = false;
                StructDecl * thread_decl = nullptr;
        };

        //=============================================================================================
        // General entry routine
        //=============================================================================================
        void applyKeywords( std::list< Declaration * > & translationUnit ) {
                ThreadKeyword   ::implement( translationUnit );
                CoroutineKeyword        ::implement( translationUnit );
                MonitorKeyword  ::implement( translationUnit );
                GeneratorKeyword  ::implement( translationUnit );
                SuspendKeyword    ::implement( translationUnit );
        }

        void implementMutexFuncs( std::list< Declaration * > & translationUnit ) {
                MutexKeyword    ::implement( translationUnit );
        }

        void implementThreadStarter( std::list< Declaration * > & translationUnit ) {
                ThreadStarter   ::implement( translationUnit );
        }

        //=============================================================================================
        // Generic keyword implementation
        //=============================================================================================
        void fixupGenerics(FunctionType * func, StructDecl * decl) {
                cloneAll(decl->parameters, func->forall);
                for ( TypeDecl * td : func->forall ) {
                        strict_dynamic_cast<StructInstType*>(
                                func->parameters.front()->get_type()->stripReferences()
                        )->parameters.push_back(
                                new TypeExpr( new TypeInstType( noQualifiers, td->name, td ) )
                        );
                }
        }

        Declaration * ConcurrentSueKeyword::postmutate(StructDecl * decl) {
                if( decl->name == type_name && decl->body ) {
                        assert( !type_decl );
                        type_decl = decl;
                }
                else if ( is_target(decl) ) {
                        handle( decl );
                }
                else if ( !except_decl && exception_name == decl->name && decl->body ) {
                        except_decl = decl;
                }
                else if ( !vtable_decl && vtable_name == decl->name && decl->body ) {
                        vtable_decl = decl;
                }
                // Might be able to get ride of is target.
                assert( is_target(decl) == (cast_target == decl->kind) );
                return decl;
        }

        DeclarationWithType * ConcurrentSueKeyword::postmutate( FunctionDecl * decl ) {
                if ( type_decl && isDestructorFor( decl, type_decl ) )
                        dtor_decl = decl;
                else if ( vtable_name.empty() )
                        ;
                else if( !decl->has_body() )
                        ;
                else if ( auto param = isMainFor( decl, cast_target ) ) {
                        // This should never trigger.
                        assert( vtable_decl );
                        // Should be safe because of isMainFor.
                        StructInstType * struct_type = static_cast<StructInstType *>(
                                static_cast<ReferenceType *>( param->get_type() )->base );
                        assert( struct_type );

                        std::list< Expression * > poly_args = { new TypeExpr( struct_type->clone() ) };
                        ObjectDecl * vtable_object = Virtual::makeVtableInstance(
                                vtable_decl->makeInst( poly_args ), struct_type, nullptr );
                        declsToAddAfter.push_back( vtable_object );
                        declsToAddAfter.push_back( Virtual::makeGetExceptionFunction(
                                vtable_object, except_decl->makeInst( std::move( poly_args ) )
                        ) );
                }

                return decl;
        }

        Expression * ConcurrentSueKeyword::postmutate( KeywordCastExpr * cast ) {
                if ( cast_target == cast->target ) {
                        // convert (thread &)t to ($thread &)*get_thread(t), etc.
                        if( !type_decl ) SemanticError( cast, context_error );
                        if( !dtor_decl ) SemanticError( cast, context_error );
                        assert( cast->result == nullptr );
                        cast->set_result( new ReferenceType( noQualifiers, new StructInstType( noQualifiers, type_decl ) ) );
                        cast->concrete_target.field  = field_name;
                        cast->concrete_target.getter = getter_name;
                }
                return cast;
        }


        void ConcurrentSueKeyword::handle( StructDecl * decl ) {
                if( ! decl->body ) return;

                if( !type_decl ) SemanticError( decl, context_error );
                if( !dtor_decl ) SemanticError( decl, context_error );

                addVtableForward( decl );
                FunctionDecl * func = forwardDeclare( decl );
                ObjectDecl * field = addField( decl );
                addRoutines( field, func );
        }

        void ConcurrentSueKeyword::addVtableForward( StructDecl * decl ) {
                if ( vtable_decl ) {
                        std::list< Expression * > poly_args = {
                                new TypeExpr( new StructInstType( noQualifiers, decl ) ),
                        };
                        declsToAddBefore.push_back( Virtual::makeGetExceptionForward(
                                vtable_decl->makeInst( poly_args ),
                                except_decl->makeInst( poly_args )
                        ) );
                        declsToAddBefore.push_back( Virtual::makeVtableForward(
                                vtable_decl->makeInst( move( poly_args ) ) ) );
                // Its only an error if we want a vtable and don't have one.
                } else if ( ! vtable_name.empty() ) {
                        SemanticError( decl, context_error );
                }
        }

        FunctionDecl * ConcurrentSueKeyword::forwardDeclare( StructDecl * decl ) {

                StructDecl * forward = decl->clone();
                forward->set_body( false );
                deleteAll( forward->get_members() );
                forward->get_members().clear();

                FunctionType * get_type = new FunctionType( noQualifiers, false );
                ObjectDecl * this_decl = new ObjectDecl(
                        "this",
                        noStorageClasses,
                        LinkageSpec::Cforall,
                        nullptr,
                        new ReferenceType(
                                noQualifiers,
                                new StructInstType(
                                        noQualifiers,
                                        decl
                                )
                        ),
                        nullptr
                );

                get_type->get_parameters().push_back( this_decl->clone() );
                get_type->get_returnVals().push_back(
                        new ObjectDecl(
                                "ret",
                                noStorageClasses,
                                LinkageSpec::Cforall,
                                nullptr,
                                new PointerType(
                                        noQualifiers,
                                        new StructInstType(
                                                noQualifiers,
                                                type_decl
                                        )
                                ),
                                nullptr
                        )
                );
                fixupGenerics(get_type, decl);

                FunctionDecl * get_decl = new FunctionDecl(
                        getter_name,
                        Type::Static,
                        LinkageSpec::Cforall,
                        get_type,
                        nullptr,
                        { new Attribute("const") },
                        Type::Inline
                );

                FunctionDecl * main_decl = nullptr;

                if( needs_main ) {
                        FunctionType * main_type = new FunctionType( noQualifiers, false );

                        main_type->get_parameters().push_back( this_decl->clone() );

                        main_decl = new FunctionDecl(
                                "main",
                                noStorageClasses,
                                LinkageSpec::Cforall,
                                main_type,
                                nullptr
                        );
                        fixupGenerics(main_type, decl);
                }

                delete this_decl;

                declsToAddBefore.push_back( forward );
                if( needs_main ) declsToAddBefore.push_back( main_decl );
                declsToAddBefore.push_back( get_decl );

                return get_decl;
        }

        ObjectDecl * ConcurrentSueKeyword::addField( StructDecl * decl ) {
                ObjectDecl * field = new ObjectDecl(
                        field_name,
                        noStorageClasses,
                        LinkageSpec::Cforall,
                        nullptr,
                        new StructInstType(
                                noQualifiers,
                                type_decl
                        ),
                        nullptr
                );

                decl->get_members().push_back( field );

                return field;
        }

        void ConcurrentSueKeyword::addRoutines( ObjectDecl * field, FunctionDecl * func ) {
                CompoundStmt * statement = new CompoundStmt();
                statement->push_back(
                        new ReturnStmt(
                                new AddressExpr(
                                        new MemberExpr(
                                                field,
                                                new CastExpr(
                                                        new VariableExpr( func->get_functionType()->get_parameters().front() ),
                                                        func->get_functionType()->get_parameters().front()->get_type()->stripReferences()->clone(),
                                                        false
                                                )
                                        )
                                )
                        )
                );

                FunctionDecl * get_decl = func->clone();

                get_decl->set_statements( statement );

                declsToAddAfter.push_back( get_decl );
        }

        //=============================================================================================
        // Suspend keyword implementation
        //=============================================================================================
        bool SuspendKeyword::is_real_suspend( FunctionDecl * func ) {
                if(isMangled(func->linkage)) return false; // the real suspend isn't mangled
                if(func->name != "__cfactx_suspend") return false; // the real suspend has a specific name
                if(func->type->parameters.size() != 0) return false; // Too many parameters
                if(func->type->returnVals.size() != 0) return false; // Too many return values

                return true;
        }

        void SuspendKeyword::premutate( FunctionDecl * func ) {
                GuardValue(in_generator);
                in_generator = nullptr;

                // Is this the real suspend?
                if(is_real_suspend(func)) {
                        decl_suspend = decl_suspend ? decl_suspend : func;
                        return;
                }

                // Is this the main of a generator?
                auto param = isMainFor( func, AggregateDecl::Aggregate::Generator );
                if(!param) return;

                if(func->type->returnVals.size() != 0) SemanticError(func->location, "Generator main must return void");

                in_generator = param;
                GuardValue(labels);
                labels.clear();
        }

        DeclarationWithType * SuspendKeyword::postmutate( FunctionDecl * func ) {
                if( !func->statements ) return func; // Not the actual definition, don't do anything
                if( !in_generator     ) return func; // Not in a generator, don't do anything
                if( labels.empty()    ) return func; // Generator has no states, nothing to do, could throw a warning

                // This is a generator main, we need to add the following code to the top
                // static void * __generator_labels[] = {&&s0, &&s1, ...};
                // goto * __generator_labels[gen.__generator_state];
                const auto & loc = func->location;

                const auto first_label = gen.newLabel("generator");

                // for each label add to declaration
                std::list<Initializer*> inits = { new SingleInit( new LabelAddressExpr( first_label ) ) };
                for(const auto & label : labels) {
                        inits.push_back(
                                new SingleInit(
                                        new LabelAddressExpr( label )
                                )
                        );
                }
                auto init = new ListInit(std::move(inits), noDesignators, true);
                labels.clear();

                // create decl
                auto decl = new ObjectDecl(
                        "__generator_labels",
                        Type::StorageClasses( Type::Static ),
                        LinkageSpec::AutoGen,
                        nullptr,
                        new ArrayType(
                                Type::Qualifiers(),
                                new PointerType(
                                        Type::Qualifiers(),
                                        new VoidType( Type::Qualifiers() )
                                ),
                                nullptr,
                                false, false
                        ),
                        init
                );

                // create the goto
                assert(in_generator);

                auto go_decl = new ObjectDecl(
                        "__generator_label",
                        noStorageClasses,
                        LinkageSpec::AutoGen,
                        nullptr,
                        new PointerType(
                                Type::Qualifiers(),
                                new VoidType( Type::Qualifiers() )
                        ),
                        new SingleInit(
                                new UntypedExpr(
                                        new NameExpr("?[?]"),
                                        {
                                                new NameExpr("__generator_labels"),
                                                new UntypedMemberExpr(
                                                        new NameExpr("__generator_state"),
                                                        new VariableExpr( in_generator )
                                                )
                                        }
                                )
                        )
                );
                go_decl->location = loc;

                auto go = new BranchStmt(
                        new VariableExpr( go_decl ),
                        BranchStmt::Goto
                );
                go->location = loc;
                go->computedTarget->location = loc;

                auto noop = new NullStmt({ first_label });
                noop->location = loc;

                // wrap everything in a nice compound
                auto body = new CompoundStmt({
                        new DeclStmt( decl ),
                        new DeclStmt( go_decl ),
                        go,
                        noop,
                        func->statements
                });
                body->location   = loc;
                func->statements = body;

                return func;
        }

        Statement * SuspendKeyword::postmutate( SuspendStmt * stmt ) {
                SuspendStmt::Type type = stmt->type;
                if(type == SuspendStmt::None) {
                        // This suspend has a implicit target, find it
                        type = in_generator ? SuspendStmt::Generator : SuspendStmt::Coroutine;
                }

                // Check that the target makes sense
                if(!in_generator && type == SuspendStmt::Generator) SemanticError( stmt->location, "'suspend generator' must be used inside main of generator type.");

                // Act appropriately
                switch(type) {
                        case SuspendStmt::Generator: return make_generator_suspend(stmt);
                        case SuspendStmt::Coroutine: return make_coroutine_suspend(stmt);
                        default: abort();
                }
        }

        Statement * SuspendKeyword::make_generator_suspend( SuspendStmt * stmt ) {
                assert(in_generator);
                // Target code is :
                //   gen.__generator_state = X;
                //   { THEN }
                //   return;
                //   __gen_X:;

                // Save the location and delete the old statement, we only need the location from this point on
                auto loc = stmt->location;

                // Build the label and get its index
                auto label = make_label();

                // Create the context saving statement
                auto save = new ExprStmt( new UntypedExpr(
                        new NameExpr( "?=?" ),
                        {
                                new UntypedMemberExpr(
                                        new NameExpr("__generator_state"),
                                        new VariableExpr( in_generator )
                                ),
                                new ConstantExpr(
                                        Constant::from_int( label.idx )
                                )
                        }
                ));
                assert(save->expr);
                save->location = loc;
                stmtsToAddBefore.push_back( save );

                // if we have a then add it here
                auto then = stmt->then;
                stmt->then = nullptr;
                delete stmt;
                if(then) stmtsToAddBefore.push_back( then );

                // Create the return statement
                auto ret = new ReturnStmt( nullptr );
                ret->location = loc;
                stmtsToAddBefore.push_back( ret );

                // Create the null statement with the created label
                auto noop = new NullStmt({ label.obj });
                noop->location = loc;

                // Return the null statement to take the place of the previous statement
                return noop;
        }

        Statement * SuspendKeyword::make_coroutine_suspend( SuspendStmt * stmt ) {
                if(stmt->then) SemanticError( stmt->location, "Compound statement following coroutines is not implemented.");

                // Save the location and delete the old statement, we only need the location from this point on
                auto loc = stmt->location;
                delete stmt;

                // Create the call expression
                if(!decl_suspend) SemanticError( loc, "suspend keyword applied to coroutines requires coroutines to be in scope, add #include <coroutine.hfa>\n");
                auto expr = new UntypedExpr( VariableExpr::functionPointer( decl_suspend ) );
                expr->location = loc;

                // Change this statement into a regular expr
                assert(expr);
                auto nstmt = new ExprStmt( expr );
                nstmt->location = loc;
                return nstmt;
        }


        //=============================================================================================
        // Mutex keyword implementation
        //=============================================================================================

        void MutexKeyword::postvisit(FunctionDecl* decl) {

                bool first = false;
                std::list<DeclarationWithType*> mutexArgs = findMutexArgs( decl, first );
                bool const isDtor = CodeGen::isDestructor( decl->name );

                // Is this function relevant to monitors
                if( mutexArgs.empty() ) {
                        // If this is the destructor for a monitor it must be mutex
                        if(isDtor) {
                                Type* ty = decl->get_functionType()->get_parameters().front()->get_type();

                                // If it's a copy, it's not a mutex
                                ReferenceType* rty = dynamic_cast< ReferenceType * >( ty );
                                if( ! rty ) return;

                                // If we are not pointing directly to a type, it's not a mutex
                                Type* base = rty->get_base();
                                if( dynamic_cast< ReferenceType * >( base ) ) return;
                                if( dynamic_cast< PointerType * >( base ) ) return;

                                // Check if its a struct
                                StructInstType * baseStruct = dynamic_cast< StructInstType * >( base );
                                if( !baseStruct ) return;

                                // Check if its a monitor
                                if(baseStruct->baseStruct->is_monitor() || baseStruct->baseStruct->is_thread())
                                        SemanticError( decl, "destructors for structures declared as \"monitor\" must use mutex parameters\n" );
                        }
                        return;
                }

                // Monitors can't be constructed with mutual exclusion
                if( CodeGen::isConstructor(decl->name) && !first ) SemanticError( decl, "constructors cannot have mutex parameters" );

                // It makes no sense to have multiple mutex parameters for the destructor
                if( isDtor && mutexArgs.size() != 1 ) SemanticError( decl, "destructors can only have 1 mutex argument" );

                // Make sure all the mutex arguments are monitors
                for(auto arg : mutexArgs) {
                        validate( arg );
                }

                // Check if we need to instrument the body
                CompoundStmt* body = decl->get_statements();
                if( ! body ) return;

                // Do we have the required headers
                if( !monitor_decl || !guard_decl || !dtor_guard_decl )
                        SemanticError( decl, "mutex keyword requires monitors to be in scope, add #include <monitor.hfa>\n" );

                // Instrument the body
                if ( isDtor && isThread( mutexArgs.front() ) ) {
                        if( !thread_guard_decl ) {
                                SemanticError( decl, "thread destructor requires threads to be in scope, add #include <thread.hfa>\n" );
                        }
                        addThreadDtorStatements( decl, body, mutexArgs );
                }
                else if ( isDtor ) {
                        addDtorStatements( decl, body, mutexArgs );
                }
                else {
                        addStatements( decl, body, mutexArgs );
                }
        }

        void MutexKeyword::postvisit(StructDecl* decl) {

                if( decl->name == "$monitor" && decl->body ) {
                        assert( !monitor_decl );
                        monitor_decl = decl;
                }
                else if( decl->name == "monitor_guard_t" && decl->body ) {
                        assert( !guard_decl );
                        guard_decl = decl;
                }
                else if( decl->name == "monitor_dtor_guard_t" && decl->body ) {
                        assert( !dtor_guard_decl );
                        dtor_guard_decl = decl;
                }
                else if( decl->name == "thread_dtor_guard_t" && decl->body ) {
                        assert( !thread_guard_decl );
                        thread_guard_decl = decl;
                }
        }

        std::list<DeclarationWithType*> MutexKeyword::findMutexArgs( FunctionDecl* decl, bool & first ) {
                std::list<DeclarationWithType*> mutexArgs;

                bool once = true;
                for( auto arg : decl->get_functionType()->get_parameters()) {
                        //Find mutex arguments
                        Type* ty = arg->get_type();
                        if( ! ty->get_mutex() ) continue;

                        if(once) {first = true;}
                        once = false;

                        //Append it to the list
                        mutexArgs.push_back( arg );
                }

                return mutexArgs;
        }

        void MutexKeyword::validate( DeclarationWithType * arg ) {
                Type* ty = arg->get_type();

                //Makes sure it's not a copy
                ReferenceType* rty = dynamic_cast< ReferenceType * >( ty );
                if( ! rty ) SemanticError( arg, "Mutex argument must be of reference type " );

                //Make sure the we are pointing directly to a type
                Type* base = rty->get_base();
                if( dynamic_cast< ReferenceType * >( base ) ) SemanticError( arg, "Mutex argument have exactly one level of indirection " );
                if( dynamic_cast< PointerType * >( base ) ) SemanticError( arg, "Mutex argument have exactly one level of indirection " );

                //Make sure that typed isn't mutex
                if( base->get_mutex() ) SemanticError( arg, "mutex keyword may only appear once per argument " );
        }

        void MutexKeyword::addDtorStatements( FunctionDecl* func, CompoundStmt * body, const std::list<DeclarationWithType * > & args ) {
                Type * arg_type = args.front()->get_type()->clone();
                arg_type->set_mutex( false );

                ObjectDecl * monitors = new ObjectDecl(
                        "__monitor",
                        noStorageClasses,
                        LinkageSpec::Cforall,
                        nullptr,
                        new PointerType(
                                noQualifiers,
                                new StructInstType(
                                        noQualifiers,
                                        monitor_decl
                                )
                        ),
                        new SingleInit( new UntypedExpr(
                                new NameExpr( "get_monitor" ),
                                {  new CastExpr( new VariableExpr( args.front() ), arg_type, false ) }
                        ))
                );

                assert(generic_func);

                //in reverse order :
                // monitor_dtor_guard_t __guard = { __monitors, func };
                body->push_front(
                        new DeclStmt( new ObjectDecl(
                                "__guard",
                                noStorageClasses,
                                LinkageSpec::Cforall,
                                nullptr,
                                new StructInstType(
                                        noQualifiers,
                                        dtor_guard_decl
                                ),
                                new ListInit(
                                        {
                                                new SingleInit( new AddressExpr( new VariableExpr( monitors ) ) ),
                                                new SingleInit( new CastExpr( new VariableExpr( func ), generic_func->clone(), false ) ),
                                                new SingleInit( new ConstantExpr( Constant::from_bool( false ) ) )
                                        },
                                        noDesignators,
                                        true
                                )
                        ))
                );

                //$monitor * __monitors[] = { get_monitor(a), get_monitor(b) };
                body->push_front( new DeclStmt( monitors ) );
        }

        void MutexKeyword::addThreadDtorStatements(
                        FunctionDecl*, CompoundStmt * body,
                        const std::list<DeclarationWithType * > & args ) {
                assert( args.size() == 1 );
                DeclarationWithType * arg = args.front();
                Type * arg_type = arg->get_type()->clone();
                assert( arg_type->get_mutex() );
                arg_type->set_mutex( false );

                // thread_dtor_guard_t __guard = { this, intptr( 0 ) };
                body->push_front(
                        new DeclStmt( new ObjectDecl(
                                "__guard",
                                noStorageClasses,
                                LinkageSpec::Cforall,
                                nullptr,
                                new StructInstType(
                                        noQualifiers,
                                        thread_guard_decl
                                ),
                                new ListInit(
                                        {
                                                new SingleInit( new CastExpr( new VariableExpr( arg ), arg_type ) ),
                                                new SingleInit( new UntypedExpr(
                                                        new NameExpr( "intptr" ), {
                                                                new ConstantExpr( Constant::from_int( 0 ) ),
                                                        }
                                                ) ),
                                        },
                                        noDesignators,
                                        true
                                )
                        ))
                );
        }

        void MutexKeyword::addStatements( FunctionDecl* func, CompoundStmt * body, const std::list<DeclarationWithType * > & args ) {
                ObjectDecl * monitors = new ObjectDecl(
                        "__monitors",
                        noStorageClasses,
                        LinkageSpec::Cforall,
                        nullptr,
                        new ArrayType(
                                noQualifiers,
                                new PointerType(
                                        noQualifiers,
                                        new StructInstType(
                                                noQualifiers,
                                                monitor_decl
                                        )
                                ),
                                new ConstantExpr( Constant::from_ulong( args.size() ) ),
                                false,
                                false
                        ),
                        new ListInit(
                                map_range < std::list<Initializer*> > ( args, [](DeclarationWithType * var ){
                                        Type * type = var->get_type()->clone();
                                        type->set_mutex( false );
                                        return new SingleInit( new UntypedExpr(
                                                new NameExpr( "get_monitor" ),
                                                {  new CastExpr( new VariableExpr( var ), type, false ) }
                                        ) );
                                })
                        )
                );

                assert(generic_func);

                // in reverse order :
                // monitor_guard_t __guard = { __monitors, #, func };
                body->push_front(
                        new DeclStmt( new ObjectDecl(
                                "__guard",
                                noStorageClasses,
                                LinkageSpec::Cforall,
                                nullptr,
                                new StructInstType(
                                        noQualifiers,
                                        guard_decl
                                ),
                                new ListInit(
                                        {
                                                new SingleInit( new VariableExpr( monitors ) ),
                                                new SingleInit( new ConstantExpr( Constant::from_ulong( args.size() ) ) ),
                                                new SingleInit( new CastExpr( new VariableExpr( func ), generic_func->clone(), false ) )
                                        },
                                        noDesignators,
                                        true
                                )
                        ))
                );

                //$monitor * __monitors[] = { get_monitor(a), get_monitor(b) };
                body->push_front( new DeclStmt( monitors) );
        }

        //=============================================================================================
        // General entry routine
        //=============================================================================================
        void ThreadStarter::previsit( StructDecl * decl ) {
                if( decl->name == "$thread" && decl->body ) {
                        assert( !thread_decl );
                        thread_decl = decl;
                }
        }

        void ThreadStarter::postvisit(FunctionDecl * decl) {
                if( ! CodeGen::isConstructor(decl->name) ) return;

                Type * typeof_this = InitTweak::getTypeofThis(decl->type);
                StructInstType * ctored_type = dynamic_cast< StructInstType * >( typeof_this );
                if( ctored_type && ctored_type->baseStruct == thread_decl ) {
                        thread_ctor_seen = true;
                }

                DeclarationWithType * param = decl->get_functionType()->get_parameters().front();
                auto type  = dynamic_cast< StructInstType * >( InitTweak::getPointerBase( param->get_type() ) );
                if( type && type->get_baseStruct()->is_thread() ) {
                        if( !thread_decl || !thread_ctor_seen ) {
                                SemanticError( type->get_baseStruct()->location, "thread keyword requires threads to be in scope, add #include <thread.hfa>");
                        }

                        addStartStatement( decl, param );
                }
        }

        void ThreadStarter::addStartStatement( FunctionDecl * decl, DeclarationWithType * param ) {
                CompoundStmt * stmt = decl->get_statements();

                if( ! stmt ) return;

                stmt->push_back(
                        new ExprStmt(
                                new UntypedExpr(
                                        new NameExpr( "__thrd_start" ),
                                        { new VariableExpr( param ), new NameExpr("main") }
                                )
                        )
                );
        }
};

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