source: src/InitTweak/GenInit.cpp @ 9d5eacb

//
// Cforall Version 1.0.0 Copyright (C) 2015 University of Waterloo
//
// The contents of this file are covered under the licence agreement in the
// file "LICENCE" distributed with Cforall.
//
// GenInit.cpp -- Generate initializers, and other stuff.
//
// Author           : Rob Schluntz
// Created On       : Mon May 18 07:44:20 2015
// Last Modified By : Andrew Beach
// Last Modified On : Mon Oct 25 13:53:00 2021
// Update Count     : 186
//
#include "GenInit.hpp"

#include <stddef.h>                    // for NULL
#include <algorithm>                   // for any_of
#include <cassert>                     // for assert, strict_dynamic_cast, assertf
#include <deque>
#include <iterator>                    // for back_inserter, inserter, back_inse...
#include <list>                        // for _List_iterator, list

#include "AST/Decl.hpp"
#include "AST/Init.hpp"
#include "AST/Pass.hpp"
#include "AST/Node.hpp"
#include "AST/Stmt.hpp"
#include "CompilationState.hpp"
#include "CodeGen/OperatorTable.hpp"
#include "Common/SemanticError.hpp"    // for SemanticError
#include "Common/ToString.hpp"         // for toCString
#include "Common/UniqueName.hpp"       // for UniqueName
#include "GenPoly/GenPoly.hpp"         // for getFunctionType, isPolyType
#include "GenPoly/ScopedSet.hpp"       // for ScopedSet, ScopedSet<>::const_iter...
#include "InitTweak.hpp"               // for isConstExpr, InitExpander, checkIn...
#include "ResolvExpr/Resolver.hpp"
#include "SymTab/GenImplicitCall.hpp"  // for genImplicitCall
#include "SymTab/Mangler.hpp"          // for Mangler
#include "Tuples/Tuples.hpp"           // for maybeImpure

namespace InitTweak {

namespace {

        // Outer pass finds declarations, for their type could wrap a type that needs hoisting
        struct HoistArrayDimension_NoResolve final :
                        public ast::WithDeclsToAdd<>, public ast::WithShortCircuiting,
                        public ast::WithGuards, public ast::WithConstTranslationUnit,
                        public ast::WithVisitorRef<HoistArrayDimension_NoResolve>,
                        public ast::WithSymbolTableX<ast::SymbolTable::ErrorDetection::IgnoreErrors> {

                // Inner pass looks within a type, for a part that depends on an expression
                struct HoistDimsFromTypes final :
                                public ast::WithShortCircuiting, public ast::WithGuards {

                        HoistArrayDimension_NoResolve * outer;
                        HoistDimsFromTypes( HoistArrayDimension_NoResolve * outer ) : outer(outer) {}

                        // Only intended for visiting through types.
                        // Tolerate, and short-circuit at, the dimension expression of an array type.
                        //    (We'll operate on the dimension expression of an array type directly
                        //    from the parent type, not by visiting through it)
                        // Look inside type exprs.
                        void previsit( const ast::Node * ) {
                                assert( false && "unsupported node type" );
                        };
                        const ast::Expr * allowedExpr = nullptr;
                        void previsit( const ast::Type * ) {
                                GuardValue( allowedExpr ) = nullptr;
                        }
                        void previsit( const ast::ArrayType * t ) {
                                GuardValue( allowedExpr ) = t->dimension.get();
                        }
                        void previsit( const ast::PointerType * t ) {
                                GuardValue( allowedExpr ) = t->dimension.get();
                        }
                        void previsit( const ast::TypeofType * t ) {
                                GuardValue( allowedExpr ) = t->expr.get();
                        }
                        void previsit( const ast::Expr * e ) {
                                assert( e == allowedExpr &&
                                    "only expecting to visit exprs that are dimension exprs or typeof(-) inner exprs" );

                                // Skip the tolerated expressions
                                visit_children = false;
                        }
                        void previsit( const ast::TypeExpr * ) {}

                        const ast::Type * postvisit(
                                        const ast::ArrayType * arrayType ) {
                                static UniqueName dimensionName( "_array_dim" );

                                if ( nullptr == arrayType->dimension ) {  // if no dimension is given, don't presume to invent one
                                        return arrayType;
                                }

                                // find size_t; use it as the type for a dim expr
                                ast::ptr<ast::Type> dimType = outer->transUnit().global.sizeType;
                                assert( dimType );
                                add_qualifiers( dimType, ast::CV::Qualifiers( ast::CV::Const ) );

                                // Special-case handling: leave the user's dimension expression alone
                                // - requires the user to have followed a careful convention
                                // - may apply to extremely simple applications, but only as windfall
                                // - users of advanced applications will be following the convention on purpose
                                // - CFA maintainers must protect the criteria against leaving too much alone

                                // Actual leave-alone cases following are conservative approximations of "cannot vary"

                                // Leave alone: literals and enum constants
                                if ( dynamic_cast< const ast::ConstantExpr * >( arrayType->dimension.get() ) ) {
                                        return arrayType;
                                }

                                // Leave alone: direct use of an object declared to be const
                                const ast::NameExpr * dimn = dynamic_cast< const ast::NameExpr * >( arrayType->dimension.get() );
                                if ( dimn ) {
                                        std::vector<ast::SymbolTable::IdData> dimnDefs = outer->symtab.lookupId( dimn->name );
                                        if ( dimnDefs.size() == 1 ) {
                                                const ast::DeclWithType * dimnDef = dimnDefs[0].id.get();
                                                assert( dimnDef && "symbol table binds a name to nothing" );
                                                const ast::ObjectDecl * dimOb = dynamic_cast< const ast::ObjectDecl * >( dimnDef );
                                                if( dimOb ) {
                                                        const ast::Type * dimTy = dimOb->type.get();
                                                        assert( dimTy && "object declaration bearing no type" );
                                                        // must not hoist some: size_t
                                                        // must hoist all: pointers and references
                                                        // the analysis is conservative; BasicType is a simple approximation
                                                        if ( dynamic_cast< const ast::BasicType * >( dimTy ) ||
                                                             dynamic_cast< const ast::SueInstType<ast::EnumDecl> * >( dimTy ) ) {
                                                                if ( dimTy->is_const() ) {
                                                                        // The dimension is certainly re-evaluable, giving the same answer each time.
                                                                        // Our user might be hoping to write the array type in multiple places, having them unify.
                                                                        // Leave the type alone.

                                                                        // We believe the new criterion leaves less alone than the old criterion.
                                                                        // Thus, the old criterion should have left the current case alone.
                                                                        // Catch cases that weren't thought through.
                                                                        assert( !Tuples::maybeImpure( arrayType->dimension ) );

                                                                        return arrayType;
                                                                }
                                                        };
                                                }
                                        }
                                }

                                // Leave alone: any sizeof expression (answer cannot vary during current lexical scope)
                                const ast::SizeofExpr * sz = dynamic_cast< const ast::SizeofExpr * >( arrayType->dimension.get() );
                                if ( sz ) {
                                        return arrayType;
                                }

                                // General-case handling: change the array-type's dim expr (hoist the user-given content out of the type)
                                // - always safe
                                // - user-unnoticeable in common applications (benign noise in -CFA output)
                                // - may annoy a responsible user of advanced applications (but they can work around)
                                // - protects against misusing advanced features
                                //
                                // The hoist, by example, is:
                                // FROM USER:  float a[ rand() ];
                                // TO GCC:     const size_t __len_of_a = rand(); float a[ __len_of_a ];

                                ast::ObjectDecl * arrayDimension = new ast::ObjectDecl(
                                        arrayType->dimension->location,
                                        dimensionName.newName(),
                                        dimType,
                                        new ast::SingleInit(
                                                arrayType->dimension->location,
                                                arrayType->dimension
                                        )
                                );

                                ast::ArrayType * mutType = ast::mutate( arrayType );
                                mutType->dimension = new ast::VariableExpr(
                                                arrayDimension->location, arrayDimension );
                                outer->declsToAddBefore.push_back( arrayDimension );

                                return mutType;
                        }  // postvisit( const ast::ArrayType * )
                }; // struct HoistDimsFromTypes

                ast::Storage::Classes storageClasses;
                void previsit(
                                const ast::ObjectDecl * decl ) {
                        GuardValue( storageClasses ) = decl->storage;
                }

                const ast::DeclWithType * postvisit(
                                const ast::ObjectDecl * objectDecl ) {

                        if ( !isInFunction() || storageClasses.is_static ) {
                                return objectDecl;
                        }

                        const ast::Type * mid = objectDecl->type;

                        ast::Pass<HoistDimsFromTypes> hoist{this};
                        const ast::Type * result = mid->accept( hoist );

                        return mutate_field( objectDecl, &ast::ObjectDecl::type, result );
                }
        };

        struct ReturnFixer final :
                        public ast::WithStmtsToAdd<>, ast::WithGuards, ast::WithShortCircuiting {
                void previsit( const ast::FunctionDecl * decl );
                const ast::ReturnStmt * previsit( const ast::ReturnStmt * stmt );
        private:
                const ast::FunctionDecl * funcDecl = nullptr;
        };

        void ReturnFixer::previsit( const ast::FunctionDecl * decl ) {
                if (decl->linkage == ast::Linkage::Intrinsic) visit_children = false;
                GuardValue( funcDecl ) = decl;
        }

        const ast::ReturnStmt * ReturnFixer::previsit(
                        const ast::ReturnStmt * stmt ) {
                auto & returns = funcDecl->returns;
                assert( returns.size() < 2 );
                // Hands off if the function returns a reference.
                // Don't allocate a temporary if the address is returned.
                if ( stmt->expr && 1 == returns.size() ) {
                        ast::ptr<ast::DeclWithType> retDecl = returns.front();
                        if ( isConstructable( retDecl->get_type() ) ) {
                                // Explicitly construct the return value using the return
                                // expression and the retVal object.
                                assertf( "" != retDecl->name,
                                        "Function %s has unnamed return value.\n",
                                        funcDecl->name.c_str() );

                                auto retVal = retDecl.strict_as<ast::ObjectDecl>();
                                if ( auto varExpr = stmt->expr.as<ast::VariableExpr>() ) {
                                        // Check if the return statement is already set up.
                                        if ( varExpr->var == retVal ) return stmt;
                                }
                                const ast::Stmt * ctorStmt = genCtorDtor(
                                        retVal->location, "?{}", retVal, stmt->expr );
                                assertf( ctorStmt,
                                        "ReturnFixer: genCtorDtor returned nullptr: %s / %s",
                                        toString( retVal ).c_str(),
                                        toString( stmt->expr ).c_str() );
                                stmtsToAddBefore.push_back( ctorStmt );

                                // Return the retVal object.
                                ast::ReturnStmt * mutStmt = ast::mutate( stmt );
                                mutStmt->expr = new ast::VariableExpr(
                                        stmt->location, retDecl );
                                return mutStmt;
                        }
                }
                return stmt;
        }

} // namespace

void genInit( ast::TranslationUnit & transUnit ) {
        ast::Pass<HoistArrayDimension_NoResolve>::run( transUnit );
        ast::Pass<ReturnFixer>::run( transUnit );
}

void fixReturnStatements( ast::TranslationUnit & transUnit ) {
        ast::Pass<ReturnFixer>::run( transUnit );
}

bool ManagedTypes::isManaged( const ast::Type * type ) const {
        // references are never constructed
        if ( dynamic_cast< const ast::ReferenceType * >( type ) ) return false;
        if ( auto tupleType = dynamic_cast< const ast::TupleType * > ( type ) ) {
                // tuple is also managed if any of its components are managed
                for (auto & component : tupleType->types) {
                        if (isManaged(component)) return true;
                }
        }
        // need to clear and reset qualifiers when determining if a type is managed
        auto tmp = shallowCopy(type);
        tmp->qualifiers = {};
        // delete tmp at return
        ast::ptr<ast::Type> guard = tmp;
        // a type is managed if it appears in the map of known managed types, or if it contains any polymorphism (is a type variable or generic type containing a type variable)
        return managedTypes.find( Mangle::mangle( tmp, {Mangle::NoOverrideable | Mangle::NoGenericParams | Mangle::Type} ) ) != managedTypes.end() || GenPoly::isPolyType( tmp );
}

bool ManagedTypes::isManaged( const ast::ObjectDecl * objDecl ) const {
        const ast::Type * type = objDecl->type;
        while ( auto at = dynamic_cast< const ast::ArrayType * >( type ) ) {
                // must always construct VLAs with an initializer, since this is an error in C
                if ( at->isVarLen && objDecl->init ) return true;
                type = at->base;
        }
        return isManaged( type );
}

void ManagedTypes::handleDWT( const ast::DeclWithType * dwt ) {
        // if this function is a user-defined constructor or destructor, mark down the type as "managed"
        if ( ! dwt->linkage.is_overrideable && CodeGen::isCtorDtor( dwt->name ) ) {
                auto & params = GenPoly::getFunctionType( dwt->get_type())->params;
                assert( ! params.empty() );
                // Type * type = InitTweak::getPointerBase( params.front() );
                // assert( type );
                managedTypes.insert( Mangle::mangle( params.front(), {Mangle::NoOverrideable | Mangle::NoGenericParams | Mangle::Type} ) );
        }
}

void ManagedTypes::handleStruct( const ast::StructDecl * aggregateDecl ) {
        // don't construct members, but need to take note if there is a managed member,
        // because that means that this type is also managed
        for ( auto & member : aggregateDecl->members ) {
                if ( auto field = member.as<ast::ObjectDecl>() ) {
                        if ( isManaged( field ) ) {
                                // generic parameters should not play a role in determining whether a generic type is constructed - construct all generic types, so that
                                // polymorphic constructors make generic types managed types
                                ast::StructInstType inst( aggregateDecl );
                                managedTypes.insert( Mangle::mangle( &inst, {Mangle::NoOverrideable | Mangle::NoGenericParams | Mangle::Type} ) );
                                break;
                        }
                }
        }
}

void ManagedTypes::beginScope() { managedTypes.beginScope(); }
void ManagedTypes::endScope() { managedTypes.endScope(); }

const ast::Stmt * genCtorDtor( const CodeLocation & loc, const std::string & fname, const ast::ObjectDecl * objDecl, const ast::Expr * arg ) {
        assertf(objDecl, "genCtorDtor passed null objDecl");
        InitExpander srcParam(arg);
        return SymTab::genImplicitCall(srcParam, new ast::VariableExpr(loc, objDecl), loc, fname, objDecl);
}

ast::ConstructorInit * genCtorInit( const CodeLocation & loc, const ast::ObjectDecl * objDecl ) {
        // Call genImplicitCall to generate calls to ctor/dtor for each constructable object.
        InitExpander srcParam{ objDecl->init }, nullParam{ (const ast::Init *)nullptr };
        ast::ptr< ast::Expr > dstParam = new ast::VariableExpr(loc, objDecl);

        ast::ptr< ast::Stmt > ctor = SymTab::genImplicitCall(
                srcParam, dstParam, loc, "?{}", objDecl );
        ast::ptr< ast::Stmt > dtor = SymTab::genImplicitCall(
                nullParam, dstParam, loc, "^?{}", objDecl,
                SymTab::LoopBackward );

        // check that either both ctor and dtor are present, or neither
        assert( (bool)ctor == (bool)dtor );

        if ( ctor ) {
                // need to remember init expression, in case no ctors exist. If ctor does exist, want to
                // use ctor expression instead of init.
                ctor.strict_as< ast::ImplicitCtorDtorStmt >();
                dtor.strict_as< ast::ImplicitCtorDtorStmt >();

                return new ast::ConstructorInit{ loc, ctor, dtor, objDecl->init };
        }

        return nullptr;
}

} // namespace InitTweak

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