source: src/ResolvExpr/CastCost.cpp

//
// 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.
//
// CastCost.cpp --
//
// Author           : Richard C. Bilson
// Created On       : Sun May 17 06:57:43 2015
// Last Modified By : Andrew Beach
// Last Modified On : Tue Oct  4 15:00:00 2019
// Update Count     : 9
//

#include "CastCost.hpp"

#include <cassert>                       // for assert

#include "AST/Print.hpp"
#include "AST/SymbolTable.hpp"
#include "AST/Type.hpp"
#include "AST/TypeEnvironment.hpp"
#include "ConversionCost.hpp"            // for ConversionCost
#include "Cost.hpp"                      // for Cost, Cost::infinity
#include "ResolvExpr/ConversionCost.hpp" // for conversionCost
#include "ResolvExpr/PtrsCastable.hpp"   // for ptrsCastable
#include "ResolvExpr/Unify.hpp"          // for typesCompatibleIgnoreQualifiers

#if 0
#define PRINT(x) x
#else
#define PRINT(x)
#endif

namespace ResolvExpr {

Cost castCost(
        const ast::Type * src, const ast::Type * dst, bool srcIsLvalue,
        const ast::SymbolTable & symtab, const ast::TypeEnvironment & env
);

namespace {
        struct CastCost : public ConversionCost {
                using ConversionCost::previsit;
                using ConversionCost::postvisit;

                CastCost(
                        const ast::Type * dst, bool srcIsLvalue, const ast::SymbolTable & symtab,
                        const ast::TypeEnvironment & env, CostCalculation costFunc )
                : ConversionCost( dst, srcIsLvalue, symtab, env, costFunc ) {}

                void postvisit( const ast::EnumInstType * enumInst ) {
                        cost = conversionCost( enumInst, dst, srcIsLvalue, symtab, env );
                        if ( enumInst->base->isTyped() ) {
                                auto baseConversionCost = 
                                        castCost( enumInst->base->base, dst, srcIsLvalue, symtab, env );
                                cost = baseConversionCost < cost? baseConversionCost: cost;
                        }
                        static ast::ptr<ast::BasicType> integer = { new ast::BasicType( ast::BasicKind::SignedInt ) };
                        Cost intCost = costCalc( integer, dst, srcIsLvalue, symtab, env );
                        intCost.incSafe();
                        cost = intCost < cost? intCost: cost;
                }

                void postvisit( const ast::BasicType * basicType ) {
                        auto ptr = dynamic_cast< const ast::PointerType * >( dst );
                        if ( ptr && basicType->isInteger() ) {
                                // needed for, e.g. unsigned long => void *
                                cost = Cost::unsafe;
                        } else {
                                cost = conversionCost( basicType, dst, srcIsLvalue, symtab, env );
                                if ( Cost::unsafe < cost ) {
                                        if ( dynamic_cast<const ast::EnumInstType *>(dst)) {
                                                cost = Cost::unsafe;
                                        }
                                }
                        }
                }

                void postvisit( const ast::ZeroType * zero ) {
                        cost = conversionCost( zero, dst, srcIsLvalue, symtab, env );
                        if ( Cost::unsafe < cost ) {
                                if ( dynamic_cast<const ast::EnumInstType *>(dst)) {
                                        cost = Cost::unsafe;
                                }
                        }
                }

                void postvisit( const ast::OneType * one ) {
                        cost = conversionCost( one, dst, srcIsLvalue, symtab, env );
                        if ( Cost::unsafe < cost ) {
                                if ( dynamic_cast<const ast::EnumInstType *>(dst)) {
                                        cost = Cost::unsafe;
                                }
                        }
                }

                void postvisit( const ast::PointerType * pointerType ) {
                        if ( auto ptr = dynamic_cast< const ast::PointerType * >( dst ) ) {
                                if (
                                        pointerType->qualifiers <= ptr->qualifiers
                                        && typesCompatibleIgnoreQualifiers( pointerType->base, ptr->base, env )
                                ) {
                                        cost = Cost::safe;
                                } else {
                                        ast::TypeEnvironment newEnv{ env };
                                        if ( auto wParams = pointerType->base.as< ast::FunctionType >() ) {
                                                newEnv.add( wParams->forall );
                                        }
                                        int castResult = ptrsCastable( pointerType->base, ptr->base, symtab, newEnv );
                                        if ( castResult > 0 ) {
                                                cost = Cost::safe;
                                        } else if ( castResult < 0 ) {
                                                cost = Cost::infinity;
                                        }
                                }
                        } else if ( auto basic = dynamic_cast< const ast::BasicType * >( dst ) ) {
                                if ( basic->isInteger() ) {
                                        // necessary for, e.g. void * => unsigned long
                                        cost = Cost::unsafe;
                                }
                        }
                }
        };

} // anonymous namespace

Cost castCost(
        const ast::Type * src, const ast::Type * dst, bool srcIsLvalue,
        const ast::SymbolTable & symtab, const ast::TypeEnvironment & env
) {
        if ( auto typeInst = dynamic_cast< const ast::TypeInstType * >( dst ) ) {
                if ( const ast::EqvClass * eqvClass = env.lookup( *typeInst ) ) {
                        // check cast cost against bound type, if present
                        if ( eqvClass->bound ) {
                                return castCost( src, eqvClass->bound, srcIsLvalue, symtab, env );
                        } else {
                                return Cost::infinity;
                        }
                } else if ( const ast::NamedTypeDecl * named = symtab.lookupType( typeInst->name ) ) {
                        // all typedefs should be gone by now
                        auto type = strict_dynamic_cast< const ast::TypeDecl * >( named );
                        if ( type->base ) {
                                return castCost( src, type->base, srcIsLvalue, symtab, env ) + Cost::safe;
                        }
                }
        }

        PRINT(
                std::cerr << "castCost ::: src is ";
                ast::print( std::cerr, src );
                std::cerr << std::endl << "dest is ";
                ast::print( std::cerr, dst );
                std::cerr << std::endl << "env is" << std::endl;
                ast::print( std::cerr, env, 2 );
        )

        if ( typesCompatibleIgnoreQualifiers( src, dst, env ) ) {
                PRINT( std::cerr << "compatible!" << std::endl; )
                if (dynamic_cast<const ast::ZeroType *>(dst) || dynamic_cast<const ast::OneType *>(dst)) {
                        return Cost::spec;
                }
                return Cost::zero;
        } else if ( dynamic_cast< const ast::VoidType * >( dst ) ) {
                return Cost::safe;
        } else if ( auto refType = dynamic_cast< const ast::ReferenceType * >( dst ) ) {
                PRINT( std::cerr << "conversionCost: dest is reference" << std::endl; )
                return convertToReferenceCost(
                        src, refType, srcIsLvalue, symtab, env, ptrsCastable );
        } else {
                ast::Pass< CastCost > converter(
                        dst, srcIsLvalue, symtab, env, castCost );
                src->accept( converter );
                return converter.core.cost;
        }
}

} // namespace ResolvExpr

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