source: src/ResolvExpr/TypeEnvironment.h @ 59cf83b

//
// 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.
//
// TypeEnvironment.h --
//
// Author           : Richard C. Bilson
// Created On       : Sun May 17 12:24:58 2015
// Last Modified By : Aaron B. Moss
// Last Modified On : Mon Jun 18 11:58:00 2018
// Update Count     : 4
//

#pragma once

#include <iostream>                    // for ostream
#include <list>                        // for list, list<>::iterator, list<>...
#include <map>                         // for map, map<>::value_compare
#include <set>                         // for set
#include <string>                      // for string
#include <utility>                     // for move, swap

#include "WidenMode.h"                 // for WidenMode

#include "SynTree/Declaration.h"       // for TypeDecl::Data, DeclarationWit...
#include "SynTree/SynTree.h"           // for UniqueId
#include "SynTree/Type.h"              // for Type, Type::ForallList
#include "SynTree/TypeSubstitution.h"  // for TypeSubstitution

namespace ResolvExpr {
        // adding this comparison operator significantly improves assertion resolution run time for
        // some cases. The current resolution algorithm's speed partially depends on the order of
        // assertions. Assertions which have fewer possible matches should appear before
        // assertions which have more possible matches. This seems to imply that this could
        // be further improved by providing an indexer as an additional argument and ordering based
        // on the number of matches of the same kind (object, function) for the names of the
        // declarations.
        //
        // I've seen a TU go from 54 minutes to 1 minute 34 seconds with the addition of this 
        // comparator.
        //
        // Note: since this compares pointers for position, minor changes in the source file that affect
        // memory layout can alter compilation time in unpredictable ways. For example, the placement
        // of a line directive can reorder type pointers with respect to each other so that assertions
        // are seen in different orders, causing a potentially different number of unification calls 
        // when resolving assertions. I've seen a TU go from 36 seconds to 27 seconds by reordering 
        // line directives alone, so it would be nice to fix this comparison so that assertions compare 
        // more consistently. I've tried to modify this to compare on mangle name instead of type as 
        // the second comparator, but this causes some assertions to never be recorded. More 
        // investigation is needed.
        struct AssertCompare {
                bool operator()( DeclarationWithType * d1, DeclarationWithType * d2 ) const {
                        int cmp = d1->get_name().compare( d2->get_name() );
                        return cmp < 0 ||
                                ( cmp == 0 && d1->get_type() < d2->get_type() );
                }
        };
        struct AssertionSetValue {
                bool isUsed;
                // chain of Unique IDs of the assertion declarations. The first ID in the chain is the ID 
                // of an assertion on the current type, with each successive ID being the ID of an 
                // assertion pulled in by the previous ID. The last ID in the chain is the ID of the 
                // assertion that pulled in the current assertion.
                std::list< UniqueId > idChain;
        };
        typedef std::map< DeclarationWithType*, AssertionSetValue, AssertCompare > AssertionSet;
        typedef std::map< std::string, TypeDecl::Data > OpenVarSet;

        void printAssertionSet( const AssertionSet &, std::ostream &, int indent = 0 );
        void printOpenVarSet( const OpenVarSet &, std::ostream &, int indent = 0 );

        struct EqvClass {
                std::set< std::string > vars;
                Type *type;
                bool allowWidening;
                TypeDecl::Data data;

                void initialize( const EqvClass &src, EqvClass &dest );
                void initialize( const EqvClass &src, EqvClass &dest, const Type *ty );
                EqvClass();
                EqvClass( const EqvClass &other );
                EqvClass( const EqvClass &other, const Type *ty );
                EqvClass( EqvClass &&other );
                EqvClass &operator=( const EqvClass &other );
                EqvClass &operator=( EqvClass &&other );
                ~EqvClass();
                void print( std::ostream &os, Indenter indent = {} ) const;

                /// Takes ownership of `ty`, freeing old `type`
                void set_type(Type* ty);
        };

        class TypeEnvironment {
                using ClassList = std::list< EqvClass >;
          public:
                const EqvClass* lookup( const std::string &var ) const;
          private:
                void add( EqvClass &&eqvClass  );
          public:
                void add( const Type::ForallList &tyDecls );
                void add( const TypeSubstitution & sub );
                template< typename SynTreeClass > int apply( SynTreeClass *&type ) const;
                template< typename SynTreeClass > int applyFree( SynTreeClass *&type ) const;
                void makeSubstitution( TypeSubstitution &result ) const;
                bool isEmpty() const { return env.empty(); }
                void print( std::ostream &os, Indenter indent = {} ) const;
                
                /// Simply concatenate the second environment onto this one; no safety checks performed
                void simpleCombine( const TypeEnvironment &second );

          private:
                /// Unifies the type bound of to with the type bound of from, returning false if fails
                bool mergeBound( EqvClass& to, const EqvClass& from, OpenVarSet& openVars, const SymTab::Indexer& indexer );

                /// Merges two type classes from local environment, returning false if fails
                bool mergeClasses( ClassList::iterator to, ClassList::iterator from, OpenVarSet& openVars, const SymTab::Indexer& indexer );

          public:
                /// Merges the second environment with this one, checking compatibility.
                /// Returns false if fails, but does NOT roll back partial changes.
                bool combine( const TypeEnvironment& second, OpenVarSet& openVars, const SymTab::Indexer& indexer );
                
                void extractOpenVars( OpenVarSet &openVars ) const;
                TypeEnvironment *clone() const { return new TypeEnvironment( *this ); }

                /// Iteratively adds the environment of a new actual (with allowWidening = false),
                /// and extracts open variables.
                void addActual( const TypeEnvironment& actualEnv, OpenVarSet& openVars );

                /// Binds the type class represented by `typeInst` to the type `bindTo`; will add 
                /// the class if needed. Returns false on failure.
                bool bindVar( TypeInstType *typeInst, Type *bindTo, const TypeDecl::Data & data, AssertionSet &need, AssertionSet &have, const OpenVarSet &openVars, WidenMode widenMode, const SymTab::Indexer &indexer );
                
                /// Binds the type classes represented by `var1` and `var2` together; will add 
                /// one or both classes if needed. Returns false on failure.
                bool bindVarToVar( TypeInstType *var1, TypeInstType *var2, const TypeDecl::Data & data, AssertionSet &need, AssertionSet &have, const OpenVarSet &openVars, WidenMode widenMode, const SymTab::Indexer &indexer );

                /// Disallows widening for all bindings in the environment
                void forbidWidening();

                using iterator = ClassList::const_iterator;
                iterator begin() const { return env.begin(); }
                iterator end() const { return env.end(); }

          private:
                ClassList env;
                
                ClassList::iterator internal_lookup( const std::string &var );
        };

        template< typename SynTreeClass >
        int TypeEnvironment::apply( SynTreeClass *&type ) const {
                TypeSubstitution sub;
                makeSubstitution( sub );
                return sub.apply( type );
        }

        template< typename SynTreeClass >
        int TypeEnvironment::applyFree( SynTreeClass *&type ) const {
                TypeSubstitution sub;
                makeSubstitution( sub );
                return sub.applyFree( type );
        }

        std::ostream & operator<<( std::ostream & out, const TypeEnvironment & env );
} // namespace ResolvExpr

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