source: src/ResolvExpr/SpecCost.cc @ 91fb850

//
// 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.cc --
//
// 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 <list>
#include <type_traits>

#include "AST/Pass.hpp"
#include "AST/Type.hpp"
#include "Common/PassVisitor.h"
#include "SynTree/Declaration.h"
#include "SynTree/Expression.h"
#include "SynTree/Type.h"

namespace ResolvExpr {

        /// Counts specializations in a type
        class CountSpecs : public WithShortCircuiting, public WithVisitorRef<CountSpecs> {
                int count = -1;  ///< specialization count (-1 for none)

        public:
                int get_count() const { return count >= 0 ? count : 0; }

                // mark specialization of base type
                void postvisit(PointerType*) { if ( count >= 0 ) ++count; }

                // mark specialization of base type
                void postvisit(ArrayType*) { if ( count >= 0 ) ++count; }

                // mark specialization of base type
                void postvisit(ReferenceType*) { if ( count >= 0 ) ++count; }

        private:
                // takes minimum non-negative count over parameter/return list
                void takeminover( int& mincount, std::list<DeclarationWithType*>& dwts ) {
                        for ( DeclarationWithType* dwt : dwts ) {
                                count = -1;
                                maybeAccept( dwt->get_type(), *visitor );
                                if ( count != -1 && count < mincount ) mincount = count;
                        }
                }

        public:
                // take minimal specialization value over ->returnVals and ->parameters
                void previsit(FunctionType* fty) {
                        int mincount = std::numeric_limits<int>::max();
                        takeminover( mincount, fty->parameters );
                        takeminover( mincount, fty->returnVals );
                        // add another level to mincount if set
                        count = mincount < std::numeric_limits<int>::max() ? mincount + 1 : -1;
                        // already visited children
                        visit_children = false;
                }

        private:
                // returns minimum non-negative count + 1 over type parameters (-1 if none such)
                int minover( std::list<Expression*>& parms ) {
                        int mincount = std::numeric_limits<int>::max();
                        for ( Expression* parm : parms ) {
                                count = -1;
                                maybeAccept( parm->result, *visitor );
                                if ( count != -1 && count < mincount ) mincount = count;
                        }
                        return mincount < std::numeric_limits<int>::max() ? mincount + 1 : -1;
                }

        public:
                // look for polymorphic parameters
                void previsit(StructInstType* sty) {
                        count = minover( sty->parameters );
                        visit_children = false;
                }

                // look for polymorphic parameters
                void previsit(UnionInstType* uty) {
                        count = minover( uty->parameters );
                        visit_children = false;
                }

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

                // take minimal specialization over elements
                // xxx - maybe don't increment, tuple flattening doesn't necessarily specialize
                void previsit(TupleType* tty) {
                        int mincount = std::numeric_limits<int>::max();
                        for ( Type* ty : tty->types ) {
                                count = -1;
                                maybeAccept( ty, *visitor );
                                if ( count != -1 && count < mincount ) mincount = count;
                        }
                        count = mincount < std::numeric_limits<int>::max() ? mincount + 1 : -1;
                        visit_children = false;
                }
        };

        /// Returns the (negated) specialization cost for a given type
        int specCost( Type* ty ) {
                PassVisitor<CountSpecs> counter;
                maybeAccept( ty, *counter.pass.visitor );
                return counter.pass.get_count();
        }

namespace {
        /// 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;

                #warning Should use a standard maybe_accept
                void maybe_accept( ast::Type const * type ) {
                        if ( type ) {
                                auto node = type->accept( *visitor );
                                assert( node == nullptr || node == 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;
                                maybe_accept( mapper( node ) );
                                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 );
                }

                // The three mappers:
                static const ast::Type * decl_type( const ast::ptr< ast::DeclWithType > & decl ) {
                        return decl->get_type();
                }
                static const ast::Type * expr_result( const ast::ptr< ast::Expr > & expr ) {
                        return expr->result;
                }
                static const ast::Type * type_deref( const ast::ptr< ast::Type > & type ) {
                        return type.get();
                }

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

                // Mark specialization of base type.
                void postvisit( const ast::PointerType * ) { if ( count >= 0 ) ++count; }
                void postvisit( const ast::ArrayType * ) { if ( count >= 0 ) ++count; }
                void postvisit( const ast::ReferenceType * ) { if ( count >= 0 ) ++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, decl_type );
                        updateMinimumPresent( minCount, fty->returns, decl_type );
                        // 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 );
                        visit_children = false;
                }

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

                // 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 ) {
        if ( nullptr == type ) {
                return 0;
        }
        ast::Pass<SpecCounter> counter;
        type->accept( counter );
        return counter.core.get_count();
}

} // namespace ResolvExpr

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