source: src/ResolvExpr/SpecCost.cpp @ 4db0140

//
// 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.
//
// SpecCost.cpp --
//
// Author           : Aaron B. Moss
// Created On       : Tue Oct 02 15:50:00 2018
// Last Modified By : Andrew Beach
// Last Modified On : Wed Jul  3 11:07:00 2019
// Update Count     : 3
//

#include <cassert>
#include <limits>
#include <type_traits>

#include "AST/Pass.hpp"
#include "AST/Type.hpp"

namespace ResolvExpr {

namespace {

const ast::Type * expr_result( const ast::ptr< ast::Expr > & expr ) {
        return expr->result.get();
}

const ast::Type * type_deref( const ast::ptr< ast::Type > & type ) {
        return type.get();
}

/// The specialization counter inner class.
class SpecCounter : public ast::WithShortCircuiting, public ast::WithVisitorRef<SpecCounter> {
        int count = -1;  ///< specialization count (-1 for none)

        // Converts the max value to -1 (none), otherwise increments the value.
        static int toNoneOrInc( int value ) {
                assert( 0 <= value );
                return value < std::numeric_limits<int>::max() ? value + 1 : -1;
        }

        template<typename T> using MapperT =
                typename std::add_pointer<ast::Type const *(typename T::value_type const &)>::type;

        // Update the minimum to the new lowest non-none value.
        template<typename T>
        void updateMinimumPresent( int & minimum, const T & list, MapperT<T> mapper ) {
                for ( const auto & node : list ) {
                        count = -1;

                        if ( ast::Type const * type = mapper( node ) ) {
                                ast::Type const * newType = type->accept( *visitor );
                                assert( newType == nullptr || newType == type );
                        }

                        if ( count != -1 && count < minimum ) minimum = count;
                }
        }

        // Returns minimum non-negative count + 1 over type parameters (-1 if none such).
        template<typename T>
        int minimumPresent( const T & list, MapperT<T> mapper ) {
                int minCount = std::numeric_limits<int>::max();
                updateMinimumPresent( minCount, list, mapper );
                return toNoneOrInc( minCount );
        }

public:
        int result() const { return 0 <= count ? count : 0; }

        // Mark specialization of base type.
        void postvisit( const ast::PointerType * ) { if ( 0 <= count ) ++count; }
        void postvisit( const ast::ArrayType * ) { if ( 0 <= count ) ++count; }
        void postvisit( const ast::ReferenceType * ) { if ( 0 <= count ) ++count; }

        void postvisit( const ast::StructInstType * ) { if ( 0 <= count ) ++count; }
        void postvisit( const ast::UnionInstType * ) { if ( 0 <= count ) ++count; }

        // Use the minimal specialization value over returns and params.
        void previsit( const ast::FunctionType * fty ) {
                int minCount = std::numeric_limits<int>::max();
                updateMinimumPresent( minCount, fty->params, type_deref );
                updateMinimumPresent( minCount, fty->returns, type_deref );
                // Add another level to minCount if set.
                count = toNoneOrInc( minCount );
                // We have already visited children.
                visit_children = false;
        }

        // Look for polymorphic parameters.
        void previsit( const ast::StructInstType * sty ) {
                count = minimumPresent( sty->params, expr_result );
        }

        // Look for polymorphic parameters.
        void previsit( const ast::UnionInstType * uty ) {
                count = minimumPresent( uty->params, expr_result );
        }

        // Note polymorphic type (which may be specialized).
        // xxx - maybe account for open/closed type variables
        void postvisit( const ast::TypeInstType * ) { count = 0; }

        // Use the minimal specialization over elements.
        // xxx - maybe don't increment, tuple flattening doesn't necessarily specialize
        void previsit( const ast::TupleType * tty ) {
                count = minimumPresent( tty->types, type_deref );
                visit_children = false;
        }
};

} // namespace

int specCost( const ast::Type * type ) {
        return ( nullptr == type ) ? 0 : ast::Pass<SpecCounter>::read( type );
}

} // namespace ResolvExpr

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