source: src/Concurrency/Keywords.cpp @ d3b33d5

//
// 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.cpp -- Implement concurrency constructs from their keywords.
//
// Author           : Andrew Beach
// Created On       : Tue Nov 16  9:53:00 2021
// Last Modified By : Peter A. Buhr
// Last Modified On : Thu Dec 14 18:02:25 2023
// Update Count     : 6
//

#include "Concurrency/Keywords.hpp"

#include <iostream>

#include "AST/Copy.hpp"
#include "AST/Decl.hpp"
#include "AST/Expr.hpp"
#include "AST/Inspect.hpp"
#include "AST/Pass.hpp"
#include "AST/Stmt.hpp"
#include "AST/DeclReplacer.hpp"
#include "AST/TranslationUnit.hpp"
#include "CodeGen/OperatorTable.hpp"
#include "Common/Examine.hpp"
#include "Common/Utility.hpp"
#include "Common/UniqueName.hpp"
#include "ControlStruct/LabelGenerator.hpp"
#include "InitTweak/InitTweak.hpp"
#include "Virtual/Tables.hpp"

namespace Concurrency {

namespace {

// --------------------------------------------------------------------------
// Loose Helper Functions:

/// Detect threads constructed with the keyword thread.
bool isThread( const ast::DeclWithType * decl ) {
        auto baseType = decl->get_type()->stripDeclarator();
        auto instType = dynamic_cast<const ast::StructInstType *>( baseType );
        if ( nullptr == instType ) { return false; }
        return instType->base->is_thread();
}

/// Get the virtual type id if given a type name.
std::string typeIdType( std::string const & exception_name ) {
        return exception_name.empty() ? std::string()
                : Virtual::typeIdType( exception_name );
}

/// Get the vtable type name if given a type name.
std::string vtableTypeName( std::string const & exception_name ) {
        return exception_name.empty() ? std::string()
                : Virtual::vtableTypeName( exception_name );
}

static ast::Type * mutate_under_references( ast::ptr<ast::Type>& type ) {
        ast::Type * mutType = type.get_and_mutate();
        for ( ast::ReferenceType * mutRef
                ; (mutRef = dynamic_cast<ast::ReferenceType *>( mutType ))
                ; mutType = mutRef->base.get_and_mutate() );
        return mutType;
}

// Describe that it adds the generic parameters and the uses of the generic
// parameters on the function and first "this" argument.
ast::FunctionDecl * fixupGenerics(
                const ast::FunctionDecl * func, const ast::StructDecl * decl ) {
        const CodeLocation & location = decl->location;
        // We have to update both the declaration
        auto mutFunc = ast::mutate( func );
        auto mutType = mutFunc->type.get_and_mutate();

        if ( decl->params.empty() ) {
                return mutFunc;
        }

        assert( 0 != mutFunc->params.size() );
        assert( 0 != mutType->params.size() );

        // Add the "forall" clause information.
        for ( const ast::ptr<ast::TypeDecl> & typeParam : decl->params ) {
                auto typeDecl = ast::deepCopy( typeParam );
                mutFunc->type_params.push_back( typeDecl );
                mutType->forall.push_back( new ast::TypeInstType( typeDecl ) );
                for ( auto & assertion : typeDecl->assertions ) {
                        mutFunc->assertions.push_back( assertion );
                        mutType->assertions.emplace_back(
                                new ast::VariableExpr( location, assertion ) );
                }
                typeDecl->assertions.clear();
        }

        // Even chain_mutate is not powerful enough for this:
        ast::ptr<ast::Type>& paramType = strict_dynamic_cast<ast::ObjectDecl *>(
                mutFunc->params[0].get_and_mutate() )->type;
        auto paramTypeInst = strict_dynamic_cast<ast::StructInstType *>(
                mutate_under_references( paramType ) );
        auto typeParamInst = strict_dynamic_cast<ast::StructInstType *>(
                mutate_under_references( mutType->params[0] ) );

        for ( const ast::ptr<ast::TypeDecl> & typeDecl : mutFunc->type_params ) {
                paramTypeInst->params.push_back(
                        new ast::TypeExpr( location, new ast::TypeInstType( typeDecl ) ) );
                typeParamInst->params.push_back(
                        new ast::TypeExpr( location, new ast::TypeInstType( typeDecl ) ) );
        }

        return mutFunc;
}

// --------------------------------------------------------------------------
struct ConcurrentSueKeyword : public ast::WithDeclsToAdd<> {
        ConcurrentSueKeyword(
                std::string&& type_name, std::string&& field_name,
                std::string&& getter_name, std::string&& context_error,
                std::string&& exception_name,
                bool needs_main, ast::AggregateDecl::Aggregate cast_target
        ) :
                type_name( type_name ), field_name( field_name ),
                getter_name( getter_name ), context_error( context_error ),
                exception_name( exception_name ),
                typeid_name( typeIdType( exception_name ) ),
                vtable_name( vtableTypeName( exception_name ) ),
                needs_main( needs_main ), cast_target( cast_target )
        {}

        virtual ~ConcurrentSueKeyword() {}

        const ast::Decl * postvisit( const ast::StructDecl * decl );
        const ast::DeclWithType * postvisit( const ast::FunctionDecl * decl );
        const ast::Expr * postvisit( const ast::KeywordCastExpr * expr );

        struct StructAndField {
                const ast::StructDecl * decl;
                const ast::ObjectDecl * field;
        };

        const ast::StructDecl * handleStruct( const ast::StructDecl * );
        void handleMain( const ast::FunctionDecl *, const ast::StructInstType * );
        void addTypeId( const ast::StructDecl * );
        void addVtableForward( const ast::StructDecl * );
        const ast::FunctionDecl * forwardDeclare( const ast::StructDecl * );
        StructAndField addField( const ast::StructDecl * );
        void addGetRoutines( const ast::ObjectDecl *, const ast::FunctionDecl * );
        void addLockUnlockRoutines( const ast::StructDecl * );

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 typeid_name;
        const std::string vtable_name;
        const bool needs_main;
        const ast::AggregateDecl::Aggregate cast_target;

        const ast::StructDecl   * type_decl = nullptr;
        const ast::FunctionDecl * dtor_decl = nullptr;
        const ast::StructDecl * except_decl = nullptr;
        const ast::StructDecl * typeid_decl = nullptr;
        const ast::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; }
//
struct ThreadKeyword final : public ConcurrentSueKeyword {
        ThreadKeyword() : ConcurrentSueKeyword(
                "thread$",
                "__thrd",
                "get_thread",
                "thread keyword requires threads to be in scope, add #include <thread.hfa>\n",
                "ThreadCancelled",
                true,
                ast::AggregateDecl::Thread )
        {}

        virtual ~ThreadKeyword() {}
};

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

        virtual ~CoroutineKeyword() {}
};

// 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;
//                                           }
//                                           void lock(MyMonitor & this) {
//                                               lock(get_monitor(this));
//                                           }
//                                           void unlock(MyMonitor & this) {
//                                               unlock(get_monitor(this));
//                                           }
//
struct MonitorKeyword final : public ConcurrentSueKeyword {
        MonitorKeyword() : ConcurrentSueKeyword(
                "monitor$",
                "__mon",
                "get_monitor",
                "monitor keyword requires monitors to be in scope, add #include <monitor.hfa>\n",
                "",
                false,
                ast::AggregateDecl::Monitor )
        {}

        virtual ~MonitorKeyword() {}
};

// Handles generator type declarations:
//
// generator MyGenerator {                   struct MyGenerator {
//  int data;                                  int data;
//  a_struct_t more_data;                      a_struct_t more_data;
//                                =>             int __generator_state;
// };                                        };
//
struct GeneratorKeyword final : public ConcurrentSueKeyword {
        GeneratorKeyword() : ConcurrentSueKeyword(
                "generator$",
                "__generator_state",
                "get_generator",
                "Unable to find builtin type generator$\n",
                "",
                true,
                ast::AggregateDecl::Generator )
        {}

        virtual ~GeneratorKeyword() {}
};

const ast::Decl * ConcurrentSueKeyword::postvisit(
                const ast::StructDecl * decl ) {
        if ( !decl->body ) {
                return decl;
        } else if ( cast_target == decl->kind ) {
                return handleStruct( decl );
        } else if ( type_name == decl->name ) {
                assert( !type_decl );
                type_decl = decl;
        } else if ( exception_name == decl->name ) {
                assert( !except_decl );
                except_decl = decl;
        } else if ( typeid_name == decl->name ) {
                assert( !typeid_decl );
                typeid_decl = decl;
        } else if ( vtable_name == decl->name ) {
                assert( !vtable_decl );
                vtable_decl = decl;
        }
        return decl;
}

// Try to get the full definition, but raise an error on conflicts.
const ast::FunctionDecl * getDefinition(
                const ast::FunctionDecl * old_decl,
                const ast::FunctionDecl * new_decl ) {
        if ( !new_decl->stmts ) {
                return old_decl;
        } else if ( !old_decl->stmts ) {
                return new_decl;
        } else {
                assert( !old_decl->stmts || !new_decl->stmts );
                return nullptr;
        }
}

const ast::DeclWithType * ConcurrentSueKeyword::postvisit(
                const ast::FunctionDecl * decl ) {
        if ( type_decl && isDestructorFor( decl, type_decl ) ) {
                // Check for forward declarations, try to get the full definition.
                dtor_decl = (dtor_decl) ? getDefinition( dtor_decl, decl ) : decl;
        } else if ( !vtable_name.empty() && decl->has_body() ) {
                if (const ast::DeclWithType * param = isMainFor( decl, cast_target )) {
                        if ( !vtable_decl ) {
                                SemanticError( decl, context_error );
                        }
                        // Should be safe because of isMainFor.
                        const ast::StructInstType * struct_type =
                                static_cast<const ast::StructInstType *>(
                                        static_cast<const ast::ReferenceType *>(
                                                param->get_type() )->base.get() );

                        handleMain( decl, struct_type );
                }
        }
        return decl;
}

const ast::Expr * ConcurrentSueKeyword::postvisit(
                const ast::KeywordCastExpr * expr ) {
        if ( cast_target == expr->target ) {
                // Convert `(thread &)ex` to `(thread$ &)*get_thread(ex)`, etc.
                if ( !type_decl || !dtor_decl ) {
                        SemanticError( expr, context_error );
                }
                assert( nullptr == expr->result );
                auto cast = ast::mutate( expr );
                cast->result = new ast::ReferenceType( new ast::StructInstType( type_decl ) );
                cast->concrete_target.field  = field_name;
                cast->concrete_target.getter = getter_name;
                return cast;
        }
        return expr;
}

const ast::StructDecl * ConcurrentSueKeyword::handleStruct(
                const ast::StructDecl * decl ) {
        assert( decl->body );

        if ( !type_decl || !dtor_decl ) {
                SemanticError( decl, context_error );
        }

        if ( !exception_name.empty() ) {
                if( !typeid_decl || !vtable_decl ) {
                        SemanticError( decl, context_error );
                }
                addTypeId( decl );
                addVtableForward( decl );
        }

        const ast::FunctionDecl * func = forwardDeclare( decl );
        StructAndField addFieldRet = addField( decl );
        decl = addFieldRet.decl;
        const ast::ObjectDecl * field = addFieldRet.field;

        addGetRoutines( field, func );
        // Add routines to monitors for use by mutex stmt.
        if ( ast::AggregateDecl::Monitor == cast_target ) {
                addLockUnlockRoutines( decl );
        }

        return decl;
}

void ConcurrentSueKeyword::handleMain(
                const ast::FunctionDecl * decl, const ast::StructInstType * type ) {
        assert( vtable_decl );
        assert( except_decl );

        const CodeLocation & location = decl->location;

        std::vector<ast::ptr<ast::Expr>> poly_args = {
                new ast::TypeExpr( location, type ),
        };
        ast::ObjectDecl * vtable_object = Virtual::makeVtableInstance(
                location,
                "_default_vtable_object_declaration",
                new ast::StructInstType( vtable_decl, copy( poly_args ) ),
                type,
                nullptr
        );
        declsToAddAfter.push_back( vtable_object );
        declsToAddAfter.push_back(
                new ast::ObjectDecl(
                        location,
                        Virtual::concurrentDefaultVTableName(),
                        new ast::ReferenceType( vtable_object->type, ast::CV::Const ),
                        new ast::SingleInit( location,
                                new ast::VariableExpr( location, vtable_object ) )
                )
        );
        declsToAddAfter.push_back( Virtual::makeGetExceptionFunction(
                location,
                vtable_object,
                new ast::StructInstType( except_decl, copy( poly_args ) )
        ) );
}

void ConcurrentSueKeyword::addTypeId( const ast::StructDecl * decl ) {
        assert( typeid_decl );
        const CodeLocation & location = decl->location;

        ast::StructInstType * typeid_type =
                new ast::StructInstType( typeid_decl, ast::CV::Const );
        typeid_type->params.push_back(
                new ast::TypeExpr( location, new ast::StructInstType( decl ) ) );
        declsToAddBefore.push_back(
                Virtual::makeTypeIdInstance( location, typeid_type ) );
        // If the typeid_type is going to be kept, the other reference will have
        // been made by now, but we also get to avoid extra mutates.
        ast::ptr<ast::StructInstType> typeid_cleanup = typeid_type;
}

void ConcurrentSueKeyword::addVtableForward( const ast::StructDecl * decl ) {
        assert( vtable_decl );
        const CodeLocation& location = decl->location;

        std::vector<ast::ptr<ast::Expr>> poly_args = {
                new ast::TypeExpr( location, new ast::StructInstType( decl ) ),
        };
        declsToAddBefore.push_back( Virtual::makeGetExceptionForward(
                location,
                new ast::StructInstType( vtable_decl, copy( poly_args ) ),
                new ast::StructInstType( except_decl, copy( poly_args ) )
        ) );
        ast::ObjectDecl * vtable_object = Virtual::makeVtableForward(
                location,
                "_default_vtable_object_declaration",
                new ast::StructInstType( vtable_decl, std::move( poly_args ) )
        );
        declsToAddBefore.push_back( vtable_object );
        declsToAddBefore.push_back(
                new ast::ObjectDecl(
                        location,
                        Virtual::concurrentDefaultVTableName(),
                        new ast::ReferenceType( vtable_object->type, ast::CV::Const ),
                        nullptr,
                        ast::Storage::Extern,
                        ast::Linkage::Cforall
                )
        );
}

const ast::FunctionDecl * ConcurrentSueKeyword::forwardDeclare(
                const ast::StructDecl * decl ) {
        const CodeLocation & location = decl->location;

        ast::StructDecl * forward = ast::deepCopy( decl );
        {
                // If removing members makes ref-count go to zero, do not free.
                ast::ptr<ast::StructDecl> forward_ptr = forward;
                forward->body = false;
                forward->members.clear();
                forward_ptr.release();
        }

        ast::ObjectDecl * this_decl = new ast::ObjectDecl(
                location,
                "this",
                new ast::ReferenceType( new ast::StructInstType( decl ) )
        );

        ast::ObjectDecl * ret_decl = new ast::ObjectDecl(
                location,
                "ret",
                new ast::PointerType( new ast::StructInstType( type_decl ) )
        );

        ast::FunctionDecl * get_decl = new ast::FunctionDecl(
                location,
                getter_name,
                { this_decl }, // params
                { ret_decl }, // returns
                nullptr, // stmts
                ast::Storage::Static,
                ast::Linkage::Cforall,
                { new ast::Attribute( "const" ) },
                ast::Function::Inline
        );
        get_decl = fixupGenerics( get_decl, decl );

        ast::FunctionDecl * main_decl = nullptr;
        if ( needs_main ) {
                // `this_decl` is copied here because the original was used above.
                main_decl = new ast::FunctionDecl(
                        location,
                        "main",
                        { ast::deepCopy( this_decl ) },
                        {},
                        nullptr,
                        ast::Storage::Classes(),
                        ast::Linkage::Cforall
                );
                main_decl = fixupGenerics( main_decl, decl );
        }

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

        return get_decl;
}

ConcurrentSueKeyword::StructAndField ConcurrentSueKeyword::addField(
                const ast::StructDecl * decl ) {
        const CodeLocation & location = decl->location;

        ast::ObjectDecl * field = new ast::ObjectDecl(
                location,
                field_name,
                new ast::StructInstType( type_decl )
        );

        auto mutDecl = ast::mutate( decl );
        mutDecl->members.push_back( field );

        return {mutDecl, field};
}

void ConcurrentSueKeyword::addGetRoutines(
                const ast::ObjectDecl * field, const ast::FunctionDecl * forward ) {
        // Clone the signature and then build the body.
        ast::FunctionDecl * decl = ast::deepCopy( forward );

        // Say it is generated at the "same" places as the forward declaration.
        const CodeLocation & location = decl->location;

        const ast::DeclWithType * param = decl->params.front();
        ast::Stmt * stmt = new ast::ReturnStmt( location,
                new ast::AddressExpr( location,
                        new ast::MemberExpr( location,
                                field,
                                new ast::CastExpr( location,
                                        new ast::VariableExpr( location, param ),
                                        ast::deepCopy( param->get_type()->stripReferences() ),
                                        ast::ExplicitCast
                                )
                        )
                )
        );

        decl->stmts = new ast::CompoundStmt( location, { stmt } );
        declsToAddAfter.push_back( decl );
}

void ConcurrentSueKeyword::addLockUnlockRoutines(
                const ast::StructDecl * decl ) {
        // This should only be used on monitors.
        assert( ast::AggregateDecl::Monitor == cast_target );

        const CodeLocation & location = decl->location;

        // The parameter for both routines.
        ast::ObjectDecl * this_decl = new ast::ObjectDecl(
                location,
                "this",
                new ast::ReferenceType( new ast::StructInstType( decl ) )
        );

        ast::FunctionDecl * lock_decl = new ast::FunctionDecl(
                location,
                "lock",
                {
                        // Copy the declaration of this.
                        ast::deepCopy( this_decl ),
                },
                { /* returns */ },
                nullptr,
                ast::Storage::Static,
                ast::Linkage::Cforall,
                { /* attributes */ },
                ast::Function::Inline
        );
        lock_decl = fixupGenerics( lock_decl, decl );

        lock_decl->stmts = new ast::CompoundStmt( location, {
                new ast::ExprStmt( location,
                        new ast::UntypedExpr( location,
                                new ast::NameExpr( location, "lock" ),
                                {
                                        new ast::UntypedExpr( location,
                                                new ast::NameExpr( location, "get_monitor" ),
                                                { new ast::VariableExpr( location,
                                                        InitTweak::getParamThis( lock_decl ) ) }
                                        )
                                }
                        )
                )
        } );

        ast::FunctionDecl * unlock_decl = new ast::FunctionDecl(
                location,
                "unlock",
                {
                        // Last use, consume the declaration of this.
                        this_decl,
                },
                { /* returns */ },
                nullptr,
                ast::Storage::Static,
                ast::Linkage::Cforall,
                { /* attributes */ },
                ast::Function::Inline
        );
        unlock_decl = fixupGenerics( unlock_decl, decl );

        unlock_decl->stmts = new ast::CompoundStmt( location, {
                new ast::ExprStmt( location,
                        new ast::UntypedExpr( location,
                                new ast::NameExpr( location, "unlock" ),
                                {
                                        new ast::UntypedExpr( location,
                                                new ast::NameExpr( location, "get_monitor" ),
                                                { new ast::VariableExpr( location,
                                                        InitTweak::getParamThis( unlock_decl ) ) }
                                        )
                                }
                        )
                )
        } );

        declsToAddAfter.push_back( lock_decl );
        declsToAddAfter.push_back( unlock_decl );
}


// --------------------------------------------------------------------------
struct SuspendKeyword final :
                public ast::WithStmtsToAdd<>, public ast::WithGuards {
        SuspendKeyword() = default;
        virtual ~SuspendKeyword() = default;

        void previsit( const ast::FunctionDecl * );
        const ast::DeclWithType * postvisit( const ast::FunctionDecl * );
        const ast::Stmt * postvisit( const ast::SuspendStmt * );

private:
        bool is_real_suspend( const ast::FunctionDecl * );

        const ast::Stmt * make_generator_suspend( const ast::SuspendStmt * );
        const ast::Stmt * make_coroutine_suspend( const ast::SuspendStmt * );

        struct LabelPair {
                ast::Label obj;
                int idx;
        };

        LabelPair make_label(const ast::Stmt * stmt ) {
                labels.push_back( ControlStruct::newLabel( "generator", stmt ) );
                return { labels.back(), int(labels.size()) };
        }

        const ast::DeclWithType * in_generator = nullptr;
        const ast::FunctionDecl * decl_suspend = nullptr;
        std::vector<ast::Label> labels;
};

void SuspendKeyword::previsit( const ast::FunctionDecl * decl ) {
        GuardValue( in_generator ); in_generator = nullptr;

        // If it is the real suspend, grab it if we don't have one already.
        if ( is_real_suspend( decl ) ) {
                decl_suspend = decl_suspend ? decl_suspend : decl;
                return;
        }

        // Otherwise check if this is a generator main and, if so, handle it.
        auto param = isMainFor( decl, ast::AggregateDecl::Generator );
        if ( !param ) return;

        if ( 0 != decl->returns.size() ) {
                SemanticError( decl->location, "Generator main must return void." );
        }

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

const ast::DeclWithType * SuspendKeyword::postvisit(
                const ast::FunctionDecl * decl ) {
        // Only modify a full definition of a generator with states.
        if ( !decl->stmts || !in_generator || labels.empty() ) return decl;

        const CodeLocation & location = decl->location;

        // Create a new function body:
        // static void * __generator_labels[] = {&&s0, &&s1, ...};
        // void * __generator_label = __generator_labels[GEN.__generator_state];
        // goto * __generator_label;
        // s0: ;
        // OLD_BODY

        // This is the null statement inserted right before the body.
        ast::NullStmt * noop = new ast::NullStmt( location );
        noop->labels.push_back( ControlStruct::newLabel( "generator", noop ) );
        const ast::Label & first_label = noop->labels.back();

        // Add each label to the init, starting with the first label.
        std::vector<ast::ptr<ast::Init>> inits = {
                new ast::SingleInit( location,
                        new ast::LabelAddressExpr( location, copy( first_label ) ) ) };
        // Then go through all the stored labels, and clear the store.
        for ( auto && label : labels ) {
                inits.push_back( new ast::SingleInit( label.location,
                        new ast::LabelAddressExpr( label.location, std::move( label )
                        ) ) );
        }
        labels.clear();
        // Then construct the initializer itself.
        auto init = new ast::ListInit( location, std::move( inits ) );

        ast::ObjectDecl * generatorLabels = new ast::ObjectDecl(
                location,
                "__generator_labels",
                new ast::ArrayType(
                        new ast::PointerType( new ast::VoidType() ),
                        nullptr,
                        ast::FixedLen,
                        ast::DynamicDim
                ),
                init,
                ast::Storage::Classes(),
                ast::Linkage::AutoGen
        );

        ast::ObjectDecl * generatorLabel = new ast::ObjectDecl(
                location,
                "__generator_label",
                new ast::PointerType( new ast::VoidType() ),
                new ast::SingleInit( location,
                        new ast::UntypedExpr( location,
                                new ast::NameExpr( location, "?[?]" ),
                                {
                                        // TODO: Could be a variable expr.
                                        new ast::NameExpr( location, "__generator_labels" ),
                                        new ast::UntypedMemberExpr( location,
                                                new ast::NameExpr( location, "__generator_state" ),
                                                new ast::VariableExpr( location, in_generator )
                                        )
                                }
                        )
                ),
                ast::Storage::Classes(),
                ast::Linkage::AutoGen
        );

        ast::BranchStmt * theGoTo = new ast::BranchStmt(
                location, new ast::VariableExpr( location, generatorLabel )
        );

        // The noop goes here in order.

        ast::CompoundStmt * body = new ast::CompoundStmt( location, {
                { new ast::DeclStmt( location, generatorLabels ) },
                { new ast::DeclStmt( location, generatorLabel ) },
                { theGoTo },
                { noop },
                { decl->stmts },
        } );

        auto mutDecl = ast::mutate( decl );
        mutDecl->stmts = body;
        return mutDecl;
}

const ast::Stmt * SuspendKeyword::postvisit( const ast::SuspendStmt * stmt ) {
        switch ( stmt->kind ) {
        case ast::SuspendStmt::None:
                // Use the context to determain the implicit target.
                if ( in_generator ) {
                        return make_generator_suspend( stmt );
                } else {
                        return make_coroutine_suspend( stmt );
                }
        case ast::SuspendStmt::Coroutine:
                return make_coroutine_suspend( stmt );
        case ast::SuspendStmt::Generator:
                // Generator suspends must be directly in a generator.
                if ( !in_generator ) SemanticError( stmt->location, "\"suspend generator\" must be used inside main of generator type." );
                return make_generator_suspend( stmt );
        }
        assert( false );
        return stmt;
}

/// Find the real/official suspend declaration.
bool SuspendKeyword::is_real_suspend( const ast::FunctionDecl * decl ) {
        return ( !decl->linkage.is_mangled
                && 0 == decl->params.size()
                && 0 == decl->returns.size()
                && "__cfactx_suspend" == decl->name );
}

const ast::Stmt * SuspendKeyword::make_generator_suspend(
                const ast::SuspendStmt * stmt ) {
        assert( in_generator );
        // Target code is:
        //   GEN.__generator_state = X;
        //   THEN
        //   return;
        //   __gen_X:;

        const CodeLocation & location = stmt->location;

        LabelPair label = make_label( stmt );

        // This is the context saving statement.
        stmtsToAddBefore.push_back( new ast::ExprStmt( location,
                new ast::UntypedExpr( location,
                        new ast::NameExpr( location, "?=?" ),
                        {
                                new ast::UntypedMemberExpr( location,
                                        new ast::NameExpr( location, "__generator_state" ),
                                        new ast::VariableExpr( location, in_generator )
                                ),
                                ast::ConstantExpr::from_int( location, label.idx ),
                        }
                )
        ) );

        // The THEN component is conditional (return is not).
        if ( stmt->then ) {
                stmtsToAddBefore.push_back( stmt->then.get() );
        }
        stmtsToAddBefore.push_back( new ast::ReturnStmt( location, nullptr ) );

        // The null statement replaces the old suspend statement.
        return new ast::NullStmt( location, { label.obj } );
}

const ast::Stmt * SuspendKeyword::make_coroutine_suspend(
                const ast::SuspendStmt * stmt ) {
        // The only thing we need from the old statement is the location.
        const CodeLocation & location = stmt->location;

        if ( !decl_suspend ) {
                SemanticError( location, "suspend keyword applied to coroutines requires coroutines to be in scope, add #include <coroutine.hfa>." );
        }
        if ( stmt->then ) {
                SemanticError( location, "Compound statement following coroutines is not implemented." );
        }

        return new ast::ExprStmt( location,
                new ast::UntypedExpr( location,
                        ast::VariableExpr::functionPointer( location, decl_suspend ) )
        );
}

// --------------------------------------------------------------------------
struct MutexKeyword final : public ast::WithDeclsToAdd<> {
        const ast::FunctionDecl * postvisit( const ast::FunctionDecl * decl );
        void postvisit( const ast::StructDecl * decl );
        const ast::Stmt * postvisit( const ast::MutexStmt * stmt );

        static std::vector<const ast::DeclWithType *> findMutexArgs(
                        const ast::FunctionDecl * decl, bool & first );
        static void validate( const ast::DeclWithType * decl );

        ast::CompoundStmt * addDtorStatements( const ast::FunctionDecl* func, const ast::CompoundStmt *, const std::vector<const ast::DeclWithType *> &);
        ast::CompoundStmt * addStatements( const ast::FunctionDecl* func, const ast::CompoundStmt *, const std::vector<const ast::DeclWithType *> &);
        ast::CompoundStmt * addStatements( const ast::CompoundStmt * body, const std::vector<ast::ptr<ast::Expr>> & args );
        ast::CompoundStmt * addThreadDtorStatements( const ast::FunctionDecl* func, const ast::CompoundStmt * body, const std::vector<const ast::DeclWithType *> & args );
        ast::ExprStmt * genVirtLockUnlockExpr( const std::string & fnName, ast::ptr<ast::Expr> expr, const CodeLocation & location, ast::Expr * param);
        ast::IfStmt * genTypeDiscrimLockUnlock( const std::string & fnName, const std::vector<ast::ptr<ast::Expr>> & args, const CodeLocation & location, ast::UntypedExpr * thisParam );
private:
        const ast::StructDecl * monitor_decl = nullptr;
        const ast::StructDecl * guard_decl = nullptr;
        const ast::StructDecl * dtor_guard_decl = nullptr;
        const ast::StructDecl * thread_guard_decl = nullptr;
        const ast::StructDecl * lock_guard_decl = nullptr;

        static ast::ptr<ast::Type> generic_func;

        UniqueName mutex_func_namer = UniqueName("__lock_unlock_curr");
};

const ast::FunctionDecl * MutexKeyword::postvisit(
                const ast::FunctionDecl * decl ) {
        bool is_first_argument_mutex = false;
        const std::vector<const ast::DeclWithType *> mutexArgs =
                findMutexArgs( decl, is_first_argument_mutex );
        bool const isDtor = CodeGen::isDestructor( decl->name );

        // Does this function have any mutex arguments that connect to monitors?
        if ( mutexArgs.empty() ) {
                // If this is the destructor for a monitor it must be mutex.
                if ( isDtor ) {
                        // This reflects MutexKeyword::validate, but no error messages.
                        const ast::Type * type = decl->type->params.front();

                        // If it's a copy, it's not a mutex.
                        const ast::ReferenceType * refType = dynamic_cast<const ast::ReferenceType *>( type );
                        if ( nullptr == refType ) {
                                return decl;
                        }

                        // If it is not pointing directly to a type, it's not a mutex.
                        auto base = refType->base;
                        if ( base.as<ast::ReferenceType>() ) return decl;
                        if ( base.as<ast::PointerType>() ) return decl;

                        // If it is not a struct, it's not a mutex.
                        auto baseStruct = base.as<ast::StructInstType>();
                        if ( nullptr == baseStruct ) return decl;

                        // If it is a monitor, then it is a monitor.
                        if( baseStruct->base->is_monitor() || baseStruct->base->is_thread() ) {
                                SemanticError( decl, "destructors for structures declared as \"monitor\" must use mutex parameters " );
                        }
                }
                return decl;
        }

        // Monitors can't be constructed with mutual exclusion.
        if ( CodeGen::isConstructor( decl->name ) && is_first_argument_mutex ) {
                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 to see if the body needs to be instrument the body.
        const ast::CompoundStmt * body = decl->stmts;
        if ( !body ) return decl;

        // Check to if the required headers have been seen.
        if ( !monitor_decl || !guard_decl || !dtor_guard_decl ) {
                SemanticError( decl, "mutex keyword requires monitors to be in scope, add #include <monitor.hfa>." );
        }

        // Instrument the body.
        ast::CompoundStmt * newBody = nullptr;
        if ( isDtor && isThread( mutexArgs.front() ) ) {
                if ( !thread_guard_decl ) {
                        SemanticError( decl, "thread destructor requires threads to be in scope, add #include <thread.hfa>." );
                }
                newBody = addThreadDtorStatements( decl, body, mutexArgs );
        } else if ( isDtor ) {
                newBody = addDtorStatements( decl, body, mutexArgs );
        } else {
                newBody = addStatements( decl, body, mutexArgs );
        }
        assert( newBody );
        return ast::mutate_field( decl, &ast::FunctionDecl::stmts, newBody );
}

void MutexKeyword::postvisit( const ast::StructDecl * decl ) {
        if ( !decl->body ) {
                return;
        } else if ( decl->name == "monitor$" ) {
                assert( !monitor_decl );
                monitor_decl = decl;
        } else if ( decl->name == "monitor_guard_t" ) {
                assert( !guard_decl );
                guard_decl = decl;
        } else if ( decl->name == "monitor_dtor_guard_t" ) {
                assert( !dtor_guard_decl );
                dtor_guard_decl = decl;
        } else if ( decl->name == "thread_dtor_guard_t" ) {
                assert( !thread_guard_decl );
                thread_guard_decl = decl;
        } else if ( decl->name == "__mutex_stmt_lock_guard" ) {
                assert( !lock_guard_decl );
                lock_guard_decl = decl;
        }
}

const ast::Stmt * MutexKeyword::postvisit( const ast::MutexStmt * stmt ) {
        if ( !lock_guard_decl ) {
                SemanticError( stmt->location, "mutex stmt requires a header, add #include <mutex_stmt.hfa>." );
        }
        ast::CompoundStmt * body =
                        new ast::CompoundStmt( stmt->location, { stmt->stmt } );

        return addStatements( body, stmt->mutexObjs );;
}

std::vector<const ast::DeclWithType *> MutexKeyword::findMutexArgs(
                const ast::FunctionDecl * decl, bool & first ) {
        std::vector<const ast::DeclWithType *> mutexArgs;

        bool once = true;
        for ( auto arg : decl->params ) {
                const ast::Type * type = arg->get_type();
                if ( type->is_mutex() ) {
                        if ( once ) first = true;
                        mutexArgs.push_back( arg.get() );
                }
                once = false;
        }
        return mutexArgs;
}

void MutexKeyword::validate( const ast::DeclWithType * decl ) {
        const ast::Type * type = decl->get_type();

        // If it's a copy, it's not a mutex.
        const ast::ReferenceType * refType = dynamic_cast<const ast::ReferenceType *>( type );
        if ( nullptr == refType ) {
                SemanticError( decl, "Mutex argument must be of reference type " );
        }

        // If it is not pointing directly to a type, it's not a mutex.
        auto base = refType->base;
        if ( base.as<ast::ReferenceType>() || base.as<ast::PointerType>() ) {
                SemanticError( decl, "Mutex argument have exactly one level of indirection " );
        }

        // If it is not a struct, it's not a mutex.
        auto baseStruct = base.as<ast::StructInstType>();
        if ( nullptr == baseStruct ) return;

        // Make sure that only the outer reference is mutex.
        if( baseStruct->is_mutex() ) {
                SemanticError( decl, "mutex keyword may only appear once per argument " );
        }
}

ast::CompoundStmt * MutexKeyword::addDtorStatements(
                const ast::FunctionDecl* func, const ast::CompoundStmt * body,
                const std::vector<const ast::DeclWithType *> & args ) {
        ast::Type * argType = ast::shallowCopy( args.front()->get_type() );
        argType->set_mutex( false );

        ast::CompoundStmt * mutBody = ast::mutate( body );

        // Generated code goes near the beginning of body:
        const CodeLocation & location = mutBody->location;

        const ast::ObjectDecl * monitor = new ast::ObjectDecl(
                location,
                "__monitor",
                new ast::PointerType( new ast::StructInstType( monitor_decl ) ),
                new ast::SingleInit(
                        location,
                        new ast::UntypedExpr(
                                location,
                                new ast::NameExpr( location, "get_monitor" ),
                                { new ast::CastExpr(
                                        location,
                                        new ast::VariableExpr( location, args.front() ),
                                        argType, ast::ExplicitCast
                                ) }
                        )
                )
        );

        assert( generic_func );

        // In reverse order:
        // monitor_dtor_guard_t __guard = { __monitor, func, false };
        mutBody->push_front(
                new ast::DeclStmt( location, new ast::ObjectDecl(
                        location,
                        "__guard",
                        new ast::StructInstType( dtor_guard_decl ),
                        new ast::ListInit(
                                location,
                                {
                                        new ast::SingleInit( location,
                                                new ast::AddressExpr( location,
                                                        new ast::VariableExpr( location, monitor ) ) ),
                                        new ast::SingleInit( location,
                                                new ast::CastExpr( location,
                                                        new ast::VariableExpr( location, func ),
                                                        generic_func,
                                                        ast::ExplicitCast ) ),
                                        new ast::SingleInit( location,
                                                ast::ConstantExpr::from_bool( location, false ) ),
                                },
                                {},
                                ast::MaybeConstruct
                        )
                ))
        );

        // monitor$ * __monitor = get_monitor(a);
        mutBody->push_front( new ast::DeclStmt( location, monitor ) );

        return mutBody;
}

ast::CompoundStmt * MutexKeyword::addStatements(
                const ast::FunctionDecl* func, const ast::CompoundStmt * body,
                const std::vector<const ast::DeclWithType * > & args ) {
        ast::CompoundStmt * mutBody = ast::mutate( body );

        // Code is generated near the beginning of the compound statement.
        const CodeLocation & location = mutBody->location;

        // Make pointer to the monitors.
        ast::ObjectDecl * monitors = new ast::ObjectDecl(
                location,
                "__monitors",
                new ast::ArrayType(
                        new ast::PointerType(
                                new ast::StructInstType( monitor_decl )
                        ),
                        ast::ConstantExpr::from_ulong( location, args.size() ),
                        ast::FixedLen,
                        ast::DynamicDim
                ),
                new ast::ListInit(
                        location,
                        map_range<std::vector<ast::ptr<ast::Init>>>(
                                args,
                                []( const ast::DeclWithType * decl ) {
                                        return new ast::SingleInit(
                                                decl->location,
                                                new ast::UntypedExpr(
                                                        decl->location,
                                                        new ast::NameExpr( decl->location, "get_monitor" ),
                                                        {
                                                                new ast::CastExpr(
                                                                        decl->location,
                                                                        new ast::VariableExpr( decl->location, decl ),
                                                                        decl->get_type(),
                                                                        ast::ExplicitCast
                                                                )
                                                        }
                                                )
                                        );
                                }
                        )
                )
        );

        assert( generic_func );

        // In Reverse Order:
        mutBody->push_front(
                new ast::DeclStmt( location, new ast::ObjectDecl(
                        location,
                        "__guard",
                        new ast::StructInstType( guard_decl ),
                        new ast::ListInit(
                                location,
                                {
                                        new ast::SingleInit( location,
                                                new ast::VariableExpr( location, monitors ) ),
                                        new ast::SingleInit( location,
                                                ast::ConstantExpr::from_ulong( location, args.size() ) ),
                                        new ast::SingleInit( location, new ast::CastExpr(
                                                location,
                                                new ast::VariableExpr( location, func ),
                                                generic_func,
                                                ast::ExplicitCast
                                        ) ),
                                },
                                {},
                                ast::MaybeConstruct
                        )
                ))
        );

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

        return mutBody;
}

// generates a cast to the void ptr to the appropriate lock type and dereferences it before calling lock or unlock on it
// used to undo the type erasure done by storing all the lock pointers as void
ast::ExprStmt * MutexKeyword::genVirtLockUnlockExpr( const std::string & fnName, ast::ptr<ast::Expr> expr, const CodeLocation & location, ast::Expr * param ) {
        return new ast::ExprStmt( location,
                new ast::UntypedExpr( location,
                        new ast::NameExpr( location, fnName ), {
                                ast::UntypedExpr::createDeref(
                                        location,
                                        new ast::CastExpr( location,
                                                param,
                                                new ast::PointerType( new ast::TypeofType( new ast::UntypedExpr(
                                                        expr->location,
                                                        new ast::NameExpr( expr->location, "__get_mutexstmt_lock_type" ),
                                                        { expr }
                                                ) ) ),
                                                ast::GeneratedFlag::ExplicitCast
                                        )
                                )
                        }
                )
        );
}

ast::IfStmt * MutexKeyword::genTypeDiscrimLockUnlock( const std::string & fnName, const std::vector<ast::ptr<ast::Expr>> & args, const CodeLocation & location, ast::UntypedExpr * thisParam ) {
        ast::IfStmt * outerLockIf = nullptr;
        ast::IfStmt * lastLockIf = nullptr;

        //adds an if/elif clause for each lock to assign type from void ptr based on ptr address
        for ( long unsigned int i = 0; i < args.size(); i++ ) {

                ast::UntypedExpr * ifCond = new ast::UntypedExpr( location,
                        new ast::NameExpr( location, "?==?" ), {
                                ast::deepCopy( thisParam ),
                                new ast::CastExpr( location, new ast::AddressExpr( location, args.at(i) ), new ast::PointerType( new ast::VoidType() ))
                        }
                );

                ast::IfStmt * currLockIf = new ast::IfStmt(
                        location,
                        ifCond,
                        genVirtLockUnlockExpr( fnName, args.at(i), location, ast::deepCopy( thisParam ) )
                );

                if ( i == 0 ) {
                        outerLockIf = currLockIf;
                } else {
                        // add ifstmt to else of previous stmt
                        lastLockIf->else_ = currLockIf;
                }

                lastLockIf = currLockIf;
        }
        return outerLockIf;
}

void flattenTuple( const ast::UntypedTupleExpr * tuple, std::vector<ast::ptr<ast::Expr>> & output ) {
        for ( auto & expr : tuple->exprs ) {
                const ast::UntypedTupleExpr * innerTuple = dynamic_cast<const ast::UntypedTupleExpr *>(expr.get());
                if ( innerTuple ) flattenTuple( innerTuple, output );
                else output.emplace_back( ast::deepCopy( expr ));
        }
}

ast::CompoundStmt * MutexKeyword::addStatements(
                const ast::CompoundStmt * body,
                const std::vector<ast::ptr<ast::Expr>> & args ) {

        // Code is generated near the beginning of the compound statement.
        const CodeLocation & location = body->location;

                // final body to return
        ast::CompoundStmt * newBody = new ast::CompoundStmt( location );

        // std::string lockFnName = mutex_func_namer.newName();
        // std::string unlockFnName = mutex_func_namer.newName();

        // If any arguments to the mutex stmt are tuples, flatten them
        std::vector<ast::ptr<ast::Expr>> flattenedArgs;
        for ( auto & arg : args ) {
                const ast::UntypedTupleExpr * tuple = dynamic_cast<const ast::UntypedTupleExpr *>(args.at(0).get());
                if ( tuple ) flattenTuple( tuple, flattenedArgs );
                else flattenedArgs.emplace_back( ast::deepCopy( arg ));
        }

        // Make pointer to the monitors.
        ast::ObjectDecl * monitors = new ast::ObjectDecl(
                location,
                "__monitors",
                new ast::ArrayType(
                        new ast::PointerType(
                                new ast::VoidType()
                        ),
                        ast::ConstantExpr::from_ulong( location, flattenedArgs.size() ),
                        ast::FixedLen,
                        ast::DynamicDim
                ),
                new ast::ListInit(
                        location,
                        map_range<std::vector<ast::ptr<ast::Init>>>(
                                flattenedArgs, [](const ast::Expr * expr) {
                                        return new ast::SingleInit(
                                                expr->location,
                                                new ast::UntypedExpr(
                                                        expr->location,
                                                        new ast::NameExpr( expr->location, "__get_mutexstmt_lock_ptr" ),
                                                        { expr }
                                                )
                                        );
                                }
                        )
                )
        );

        ast::StructInstType * lock_guard_struct =
                        new ast::StructInstType( lock_guard_decl );

        // use try stmts to lock and finally to unlock
        ast::TryStmt * outerTry = nullptr;
        ast::TryStmt * currentTry;
        ast::CompoundStmt * lastBody = nullptr;

        // adds a nested try stmt for each lock we are locking
        for ( long unsigned int i = 0; i < flattenedArgs.size(); i++ ) {
                ast::UntypedExpr * innerAccess = new ast::UntypedExpr(
                        location,
                        new ast::NameExpr( location,"?[?]" ), {
                                new ast::NameExpr( location, "__monitors" ),
                                ast::ConstantExpr::from_int( location, i )
                        }
                );

                // make the try body
                ast::CompoundStmt * currTryBody = new ast::CompoundStmt( location );
                ast::IfStmt * lockCall = genTypeDiscrimLockUnlock( "lock", flattenedArgs, location, innerAccess );
                currTryBody->push_back( lockCall );

                // make the finally stmt
                ast::CompoundStmt * currFinallyBody = new ast::CompoundStmt( location );
                ast::IfStmt * unlockCall = genTypeDiscrimLockUnlock( "unlock", flattenedArgs, location, innerAccess );
                currFinallyBody->push_back( unlockCall );

                // construct the current try
                currentTry = new ast::TryStmt(
                        location,
                        currTryBody,
                        {},
                        new ast::FinallyClause( location, currFinallyBody )
                );
                if ( i == 0 ) outerTry = currentTry;
                else {
                        // pushback try into the body of the outer try
                        lastBody->push_back( currentTry );
                }
                lastBody = currTryBody;
        }

        // push body into innermost try body
        if ( lastBody != nullptr ) {
                lastBody->push_back( body );
                newBody->push_front( outerTry );
        }

        // monitor_guard_t __guard = { __monitors, # };
        newBody->push_front(
                new ast::DeclStmt(
                        location,
                        new ast::ObjectDecl(
                                location,
                                "__guard",
                                lock_guard_struct,
                                new ast::ListInit(
                                        location,
                                        {
                                                new ast::SingleInit(
                                                        location,
                                                        new ast::VariableExpr( location, monitors ) ),
                                                new ast::SingleInit(
                                                        location,
                                                        ast::ConstantExpr::from_ulong( location, flattenedArgs.size() ) ),
                                        },
                                        {},
                                        ast::MaybeConstruct
                                )
                        )
                )
        );

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

        // // The parameter for both __lock_curr/__unlock_curr routines.
        // ast::ObjectDecl * this_decl = new ast::ObjectDecl(
        //      location,
        //      "this",
        //      new ast::PointerType( new ast::VoidType() ),
        //      nullptr,
        //      {},
        //      ast::Linkage::Cforall
        // );

        // ast::FunctionDecl * lock_decl = new ast::FunctionDecl(
        //      location,
        //      lockFnName,
        //      { /* forall */ },
        //      {
        //              // Copy the declaration of this.
        //              this_decl,
        //      },
        //      { /* returns */ },
        //      nullptr,
        //      0,
        //      ast::Linkage::Cforall,
        //      { /* attributes */ },
        //      ast::Function::Inline
        // );

        // ast::FunctionDecl * unlock_decl = new ast::FunctionDecl(
        //      location,
        //      unlockFnName,
        //      { /* forall */ },
        //      {
        //              // Copy the declaration of this.
        //              ast::deepCopy( this_decl ),
        //      },
        //      { /* returns */ },
        //      nullptr,
        //      0,
        //      ast::Linkage::Cforall,
        //      { /* attributes */ },
        //      ast::Function::Inline
        // );

        // ast::IfStmt * outerLockIf = nullptr;
        // ast::IfStmt * outerUnlockIf = nullptr;
        // ast::IfStmt * lastLockIf = nullptr;
        // ast::IfStmt * lastUnlockIf = nullptr;

        // //adds an if/elif clause for each lock to assign type from void ptr based on ptr address
        // for ( long unsigned int i = 0; i < args.size(); i++ ) {
        //      ast::VariableExpr * thisParam = new ast::VariableExpr( location, InitTweak::getParamThis( lock_decl ) );
        //      ast::UntypedExpr * ifCond = new ast::UntypedExpr( location,
        //              new ast::NameExpr( location, "?==?" ), {
        //                      thisParam,
        //                      new ast::CastExpr( location, new ast::AddressExpr( location, args.at(i) ), new ast::PointerType( new ast::VoidType() ))
        //              }
        //      );

        //      ast::IfStmt * currLockIf = new ast::IfStmt(
        //              location,
        //              ast::deepCopy( ifCond ),
        //              genVirtLockUnlockExpr( "lock", args.at(i), location, ast::deepCopy( thisParam ) )
        //      );

        //      ast::IfStmt * currUnlockIf = new ast::IfStmt(
        //              location,
        //              ifCond,
        //              genVirtLockUnlockExpr( "unlock", args.at(i), location, ast::deepCopy( thisParam ) )
        //      );

        //      if ( i == 0 ) {
        //              outerLockIf = currLockIf;
        //              outerUnlockIf = currUnlockIf;
        //      } else {
        //              // add ifstmt to else of previous stmt
        //              lastLockIf->else_ = currLockIf;
        //              lastUnlockIf->else_ = currUnlockIf;
        //      }

        //      lastLockIf = currLockIf;
        //      lastUnlockIf = currUnlockIf;
        // }

        // // add pointer typing if/elifs to body of routines
        // lock_decl->stmts = new ast::CompoundStmt( location, { outerLockIf } );
        // unlock_decl->stmts = new ast::CompoundStmt( location, { outerUnlockIf } );

        // // add routines to scope
        // declsToAddBefore.push_back( lock_decl );
        // declsToAddBefore.push_back( unlock_decl );

        // newBody->push_front(new ast::DeclStmt( location, lock_decl ));
        // newBody->push_front(new ast::DeclStmt( location, unlock_decl ));

        return newBody;
}

ast::CompoundStmt * MutexKeyword::addThreadDtorStatements(
                const ast::FunctionDecl*, const ast::CompoundStmt * body,
                const std::vector<const ast::DeclWithType * > & args ) {
        assert( args.size() == 1 );
        const ast::DeclWithType * arg = args.front();
        const ast::Type * argType = arg->get_type();
        assert( argType->is_mutex() );

        ast::CompoundStmt * mutBody = ast::mutate( body );

        // The code is generated near the front of the body.
        const CodeLocation & location = mutBody->location;

        // thread_dtor_guard_t __guard = { this, intptr( 0 ) };
        mutBody->push_front( new ast::DeclStmt(
                location,
                new ast::ObjectDecl(
                        location,
                        "__guard",
                        new ast::StructInstType( thread_guard_decl ),
                        new ast::ListInit(
                                location,
                                {
                                        new ast::SingleInit( location,
                                                new ast::CastExpr( location,
                                                        new ast::VariableExpr( location, arg ), argType ) ),
                                        new ast::SingleInit(
                                                location,
                                                new ast::UntypedExpr(
                                                        location,
                                                        new ast::NameExpr( location, "intptr" ), {
                                                                ast::ConstantExpr::from_int( location, 0 ),
                                                        }
                                                ) ),
                                },
                                {},
                                ast::MaybeConstruct
                        )
                )
        ));

        return mutBody;
}

ast::ptr<ast::Type> MutexKeyword::generic_func =
        new ast::FunctionType( ast::FixedArgs );

// --------------------------------------------------------------------------
struct ThreadStarter final {
        void previsit( const ast::StructDecl * decl );
        const ast::FunctionDecl * postvisit( const ast::FunctionDecl * decl );

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

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

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

        // Seach for the thread constructor.
        // (Are the "prefixes" of these to blocks the same?)
        const ast::Type * typeof_this = InitTweak::getTypeofThis( decl->type );
        auto ctored_type = dynamic_cast<const ast::StructInstType *>( typeof_this );
        if ( ctored_type && ctored_type->base == thread_decl ) {
                thread_ctor_seen = true;
        }

        // Modify this declaration, the extra checks to see if we will are first.
        const ast::ptr<ast::DeclWithType> & param = decl->params.front();
        auto type = dynamic_cast<const ast::StructInstType *>(
                ast::getPointerBase( param->get_type() ) );
        if ( nullptr == type ) return decl;
        if ( !type->base->is_thread() ) return decl;
        if ( !thread_decl || !thread_ctor_seen ) {
                SemanticError( type->base->location, "thread keyword requires threads to be in scope, add #include <thread.hfa>." );
        }
        const ast::CompoundStmt * stmt = decl->stmts;
        if ( nullptr == stmt ) return decl;

        // Now do the actual modification:
        ast::CompoundStmt * mutStmt = ast::mutate( stmt );
        const CodeLocation & location = mutStmt->location;
        mutStmt->push_back(
                new ast::ExprStmt(
                        location,
                        new ast::UntypedExpr(
                                location,
                                new ast::NameExpr( location, "__thrd_start" ),
                                {
                                        new ast::VariableExpr( location, param ),
                                        new ast::NameExpr( location, "main" ),
                                }
                        )
                )
        );

        return ast::mutate_field( decl, &ast::FunctionDecl::stmts, mutStmt );
}

} // namespace

// --------------------------------------------------------------------------
// Interface Functions:

void implementKeywords( ast::TranslationUnit & translationUnit ) {
        ast::Pass<ThreadKeyword>::run( translationUnit );
        ast::Pass<CoroutineKeyword>::run( translationUnit );
        ast::Pass<MonitorKeyword>::run( translationUnit );
        ast::Pass<GeneratorKeyword>::run( translationUnit );
        ast::Pass<SuspendKeyword>::run( translationUnit );
}

void implementMutex( ast::TranslationUnit & translationUnit ) {
        ast::Pass<MutexKeyword>::run( translationUnit );
}

void implementThreadStarter( ast::TranslationUnit & translationUnit ) {
        ast::Pass<ThreadStarter>::run( translationUnit );
}

}

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