source: src/ResolvExpr/Cost.h @ b93c544

//
// 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.
//
// Cost.h --
//
// Author           : Peter Buhr and Aaron Moss
// Created On       : Sun May 17 09:39:50 2015
// Last Modified By : Peter A. Buhr
// Last Modified On : Fri Jun 21 11:39:13 2019
// Update Count     : 63
//

#pragma once

#include <iostream>
#include <cassert>
#include <climits>

namespace ResolvExpr {

// To maximize performance and space, the 7 resolution costs are packed into a single 64-bit word. However, the
// specialization cost is a negative value so a correction is needed is a few places.

class Cost {
        union {
                struct {
                #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
                        // Little-endian => first value is low priority and last is high priority.
                        unsigned char padding;                                  ///< unused
                        unsigned char referenceCost;                    ///< reference conversions
                        unsigned char specCost;                                 ///< Polymorphic type specializations (type assertions), negative cost
                        unsigned char varCost;                                  ///< Count of polymorphic type variables
                        unsigned char signCost;                                 ///< Count of safe sign conversions
                        unsigned char safeCost;                                 ///< Safe (widening) conversions
                        unsigned char polyCost;                                 ///< Count of parameters and return values bound to some poly type
                        unsigned char unsafeCost;                               ///< Unsafe (narrowing) conversions
                #else
                        #error Cost BIG_ENDIAN unsupported
                #endif
                } v;
                uint64_t all;
        };
        static const unsigned char correctb = 0xff;             // byte correction for negative spec cost
        static const uint64_t correctw = 0x00'00'00'00'00'ff'00'00; //' word correction for negative spec cost
  public:
        // Compiler adjusts constants for correct endian.
        enum : uint64_t {
                zero      = 0x00'00'00'00'00'ff'00'00,
                infinity  = 0xff'ff'ff'ff'ff'00'ff'ff,
                unsafe    = 0x01'00'00'00'00'ff'00'00,
                poly      = 0x00'01'00'00'00'ff'00'00,
                safe      = 0x00'00'01'00'00'ff'00'00,
                sign      = 0x00'00'00'01'00'ff'00'00,
                var       = 0x00'00'00'00'01'ff'00'00,
                spec      = 0x00'00'00'00'00'fe'00'00,
                reference = 0x00'00'00'00'00'ff'01'00,
        }; //'

        Cost( uint64_t all ) { Cost::all = all; }
        Cost( int unsafeCost, int polyCost, int safeCost, int signCost, int varCost, int specCost, int referenceCost ) {
                // Assume little-endian => first value is low priority and last is high priority.
                v = {
                #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
                        (unsigned char)0,                                               // padding
                        (unsigned char)referenceCost,                   // low priority
                        (unsigned char)(specCost + correctb),   // correct for signedness
                        (unsigned char)varCost,
                        (unsigned char)signCost,
                        (unsigned char)safeCost,
                        (unsigned char)polyCost,
                        (unsigned char)unsafeCost,                              // high priority
                #else
                        #error Cost BIG_ENDIAN unsupported
                #endif
                };
        }

        int get_unsafeCost() const { return v.unsafeCost; }
        int get_polyCost() const { return v.polyCost; }
        int get_safeCost() const { return v.safeCost; }
        int get_signCost() const { return v.signCost; }
        int get_varCost() const { return v.varCost; }
        int get_specCost() const { return -(correctb - v.specCost); }
        int get_referenceCost() const { return v.referenceCost; }

        friend bool operator==( const Cost, const Cost );
        friend bool operator!=( const Cost lhs, const Cost rhs );
        // returns negative for *this < rhs, 0 for *this == rhs, positive for *this > rhs
        int compare( const Cost rhs ) const {
                if ( all == infinity ) return 1;
                if ( rhs.all == infinity ) return -1;
                return all > rhs.all ? 1 : all == rhs.all ? 0 : -1;
        }
        friend bool operator<( const Cost lhs, const Cost rhs );

        friend Cost operator+( const Cost lhs, const Cost rhs );

        Cost operator+=( const Cost rhs ) {
                if ( all == infinity ) return *this;
                if ( rhs.all == infinity ) {
                        all = infinity;
                        return *this;
                }
                all += rhs.all - correctw;                                      // correct for negative spec cost
                return *this;
        }

        Cost incUnsafe( int inc = 1 ) {
                if ( all != infinity ) { assert( v.unsafeCost + inc <= UCHAR_MAX ); v.unsafeCost += inc; }
                return *this;
        }

        Cost incPoly( int inc = 1 ) {
                if ( all != infinity ) { assert( v.polyCost + inc <= UCHAR_MAX ); v.polyCost += inc; }
                return *this;
        }

        Cost incSafe( int inc = 1 ) {
                if ( all != infinity ) { assert( v.safeCost + inc <= UCHAR_MAX ); v.safeCost += inc; }
                return *this;
        }

        Cost incSign( int inc = 1 ) {
                if ( all != infinity ) { assert( v.signCost + inc <= UCHAR_MAX ); v.signCost += inc; }
                return *this;
        }

        Cost incVar( int inc = 1 ) {
                if ( all != infinity ) { assert( v.varCost + inc <= UCHAR_MAX ); v.varCost += inc; }
                return *this;
        }

        Cost decSpec( int dec = 1 ) {
                if ( all != infinity ) { assert( v.specCost - dec >= 0 ); v.specCost -= dec; }
                return *this;
        }

        Cost incReference( int inc = 1 ) {
                if ( all != infinity ) { assert( v.referenceCost + inc <= UCHAR_MAX ); v.referenceCost += inc; }
                return *this;
        }

        friend std::ostream & operator<<( std::ostream & os, const Cost cost );
};

inline bool operator==( const Cost lhs, const Cost rhs ) {
        return lhs.all == rhs.all;
}

inline bool operator!=( const Cost lhs, const Cost rhs ) {
        return !( lhs.all == rhs.all );
}

inline bool operator<( const Cost lhs, const Cost rhs ) {
        if ( lhs.all == Cost::infinity ) return false;
        if ( rhs.all == Cost::infinity ) return true;
        return lhs.all < rhs.all;
}

inline Cost operator+( const Cost lhs, const Cost rhs ) {
        if ( lhs.all == Cost::infinity || rhs.all == Cost::infinity ) return Cost{ Cost::infinity };
        return Cost{ lhs.all + rhs.all - Cost::correctw }; // correct for negative spec cost
}

inline std::ostream & operator<<( std::ostream & os, const Cost cost ) {
        return os << "( " << cost.get_unsafeCost() << ", " << cost.get_polyCost() << ", " << cost.get_safeCost()
                          << ", " << cost.get_signCost() << ", " << cost.get_varCost() << ", " << cost.get_specCost()
                          << ", " << cost.get_referenceCost() << " )";
}

} // namespace ResolvExpr

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