source: src/ResolvExpr/TypeEnvironment.cc @ eff03a94

//
// 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.cc --
//
// Author           : Aaron B. Moss
// Created On       : Sun May 17 12:19:47 2015
// Last Modified By : Aaron B. Moss
// Last Modified On : Fri Jun 29 15:51:00 2018
// Update Count     : 5
//

#include <cassert>                     // for assert
#include <algorithm>                   // for copy, set_intersection
#include <iterator>                    // for ostream_iterator, insert_iterator
#include <utility>                     // for pair, move

#include "Common/InternedString.h"     // for interned_string
#include "Common/PassVisitor.h"        // for PassVisitor<GcTracer>
#include "Common/option.h"             // for option<T>
#include "Common/utility.h"            // for maybeClone
#include "SymTab/Indexer.h"            // for Indexer
#include "SynTree/GcTracer.h"          // for PassVisitor<GcTracer>
#include "SynTree/Type.h"              // for Type, FunctionType, Type::Fora...
#include "SynTree/TypeSubstitution.h"  // for TypeSubstitution
#include "Tuples/Tuples.h"             // for isTtype
#include "TypeEnvironment.h"
#include "typeops.h"                   // for occurs
#include "Unify.h"                     // for unifyInexact

namespace ResolvExpr {
        #if 0
        #define PRE_POST_VALIDATE auto dbg = ValidateGuard{this, __func__};
        #define PRE_POST_VALIDATE_NOM auto dbg = ValidateGuard{this};
        struct ValidateGuard {
                const TypeEnvironment* env;
                const TypeEnvironment::Classes* old_classes;
                const TypeEnvironment::Bindings* old_bindings;
                const char* last_fn;

                void validate_classes( const TypeEnvironment::Classes* c ) {
                        typedef TypeEnvironment::Classes C;

                        assertf( c != nullptr, "classes non-null" );
                        
                        C::Mode cmode = c->get_mode();
                        if ( cmode == C::BASE ) {
                                // xxx - consistency checks
                        } else {
                                assertf( cmode == C::ADD || cmode == C::REM || cmode == C::ADDTO || cmode == C::REMFROM, "valid classes mode" );
                                validate_classes( c->get_base() );
                        }
                }

                void validate_bindings( const TypeEnvironment::Bindings* b ) {
                        typedef TypeEnvironment::Bindings B;

                        assertf( b != nullptr, "bindings non-null" );

                        B::Mode bmode = b->get_mode();
                        if ( bmode == B::BASE ) {
                                // xxx - consistency checks
                        } else {
                                assertf( bmode == B::REM || bmode == B::INS || bmode == B::UPD, "valid bindings mode" );
                                validate_bindings( b->get_base() );
                        }
                }

                void validate_env() {
                        validate_classes( env->classes );
                        validate_bindings( env->bindings );
                        
                        // xxx - joint validation
                }

                ValidateGuard(const TypeEnvironment* e)
                        : env{e}, old_classes{e->classes}, old_bindings{e->bindings}, last_fn{e->last_fn}
                        { validate_env(); }
                ValidateGuard(const TypeEnvironment* e, const char* fn)
                        : env{e}, old_classes{e->classes}, old_bindings{e->bindings}, last_fn{fn} 
                        { validate_env(); }
                ~ValidateGuard() {
                        validate_env();
                        if ( env->classes != old_classes ) validate_classes( old_classes );
                        if ( env->bindings != old_bindings ) validate_bindings( old_bindings );
                        const_cast<TypeEnvironment*>(env)->last_fn = last_fn;
                }
        };
        #else
        #define PRE_POST_VALIDATE
        #define PRE_POST_VALIDATE_NOM
        #endif

        void printAssertionSet( const AssertionSet &assertions, std::ostream &os, int indent ) {
                for ( AssertionSet::const_iterator i = assertions.begin(); i != assertions.end(); ++i ) {
                        i->first->print( os, indent );
                        if ( i->second.isUsed ) {
                                os << "(used)";
                        } else {
                                os << "(not used)";
                        } // if
                } // for
        }

        void printOpenVarSet( const OpenVarSet &openVars, std::ostream &os, int indent ) {
                os << std::string( indent, ' ' );
                for ( OpenVarSet::const_iterator i = openVars.begin(); i != openVars.end(); ++i ) {
                        os << i->first << "(" << i->second << ") ";
                } // for
        }

        std::pair<interned_string, interned_string> TypeEnvironment::mergeClasses( 
                        interned_string root1, interned_string root2 ) {
                PRE_POST_VALIDATE
                // merge classes
                Classes* newClasses = classes->merge( root1, root2 );

                // determine new root
                assertf(classes->get_mode() == Classes::REMFROM, "classes updated to REMFROM by merge");
                auto ret = std::make_pair( classes->get_root(), classes->get_child() );
                
                // finalize classes
                classes = newClasses;
                return ret;
        }

        ClassRef TypeEnvironment::lookup( interned_string var ) const {
                interned_string root = classes->find_or_default( var, nullptr );
                if ( root ) return { this, root };
                else return { nullptr, var };
        }

        bool isFtype( Type *type ) {
                if ( dynamic_cast< FunctionType* >( type ) ) {
                        return true;
                } else if ( TypeInstType *typeInst = dynamic_cast< TypeInstType* >( type ) ) {
                        return typeInst->get_isFtype();
                } // if
                return false;
        }

        bool tyVarCompatible( const TypeDecl::Data & data, Type *type ) {
                switch ( data.kind ) {
                  case TypeDecl::Dtype:
                        // to bind to an object type variable, the type must not be a function type.
                        // if the type variable is specified to be a complete type then the incoming
                        // type must also be complete
                        // xxx - should this also check that type is not a tuple type and that it's not a ttype?
                        return ! isFtype( type ) && (! data.isComplete || type->isComplete() );
                  case TypeDecl::Ftype:
                        return isFtype( type );
                  case TypeDecl::Ttype:
                        // ttype unifies with any tuple type
                        return dynamic_cast< TupleType * >( type ) || Tuples::isTtype( type );
                } // switch
                return false;
        }

        bool TypeEnvironment::bindVar( TypeInstType* typeInst, Type* bindTo, 
                        const TypeDecl::Data& data, AssertionSet& need, AssertionSet& have, 
                        const OpenVarSet& openVars, WidenMode widenMode, const SymTab::Indexer& indexer ) {
                PRE_POST_VALIDATE
                // remove references from other, so that type variables can only bind to value types
                bindTo = bindTo->stripReferences();
                
                auto tyVar = openVars.find( typeInst->get_name() );
                assert( tyVar != openVars.end() );
                if ( ! tyVarCompatible( tyVar->second, bindTo ) ) return false;

                if ( occurs( bindTo, typeInst->get_name(), *this ) ) return false;

                if ( ClassRef curClass = lookup( typeInst->get_name() ) ) {
                        BoundType curData = curClass.get_bound();
                        if ( curData.type ) {
                                Type* common = nullptr;
                                // attempt to unify equivalence class type (which needs its qualifiers restored) 
                                // with the target type
                                Type* newType = curData.type->clone();
                                newType->get_qualifiers() = typeInst->get_qualifiers();
                                if ( unifyInexact( newType, bindTo, *this, need, have, openVars, 
                                                widenMode & WidenMode{ curData.allowWidening, true }, indexer, common ) ) {
                                        if ( common ) {
                                                // update bound type to common type
                                                common->get_qualifiers() = Type::Qualifiers{};
                                                curData.type = common;
                                                bindings = bindings->set( curClass.update_root(), curData );
                                        }
                                        return true;
                                } else return false;
                        } else {
                                // update bound type to other type
                                curData.type = bindTo->clone();
                                curData.type->get_qualifiers() = Type::Qualifiers{};
                                curData.allowWidening = widenMode.widenFirst && widenMode.widenSecond;
                                bindings = bindings->set( curClass.get_root(), curData );
                        }
                } else {
                        // make new class consisting entirely of this variable
                        BoundType curData{ 
                                bindTo->clone(), widenMode.widenFirst && widenMode.widenSecond, data };
                        curData.type->get_qualifiers() = Type::Qualifiers{};
                        classes = classes->add( curClass.get_root() );
                        bindings = bindings->set( curClass.get_root(), curData );
                }
                return true;
        }
        
        bool TypeEnvironment::bindVarToVar( TypeInstType* var1, TypeInstType* var2, 
                        const TypeDecl::Data& data, AssertionSet& need, AssertionSet& have, 
                        const OpenVarSet& openVars, WidenMode widenMode, const SymTab::Indexer& indexer ) {
                PRE_POST_VALIDATE
                ClassRef class1 = lookup( var1->get_name() );
                ClassRef class2 = lookup( var2->get_name() );
                
                // exit early if variables already bound together
                if ( class1 && class2 && class1 == class2 ) {
                        BoundType data1 = class1.get_bound();
                        // narrow the binding if needed
                        if ( data1.allowWidening && widenMode.widenFirst != widenMode.widenSecond ) {
                                data1.allowWidening = false;
                                bindings = bindings->set( class1.get_root(), data1 );
                        }
                        return true;
                }

                BoundType data1 = class1 ? class1.get_bound() : BoundType{};
                BoundType data2 = class2 ? class2.get_bound() : BoundType{};

                bool widen1 = data1.allowWidening && widenMode.widenFirst;
                bool widen2 = data2.allowWidening && widenMode.widenSecond;

                if ( data1.type && data2.type ) {
                        // attempt to unify bound classes
                        Type* common = nullptr;
                        if ( unifyInexact( data1.type->clone(), data2.type->clone(), *this, need, have, 
                                        openVars, WidenMode{ widen1, widen2 }, indexer, common ) ) {
                                // merge type variables
                                interned_string root = 
                                        mergeClasses( class1.update_root(), class2.update_root() ).first;
                                // update bindings
                                data1.allowWidening = widen1 && widen2;
                                if ( common ) {
                                        common->get_qualifiers() = Type::Qualifiers{};
                                        data1.type = common;
                                }
                                bindings = bindings->set( root, data1 );
                        } else return false;
                } else if ( class1 && class2 ) {
                        // both classes exist, only one bound -- merge type variables
                        auto merged = mergeClasses( class1.get_root(), class2.get_root() );
                        // remove subordinate binding
                        bindings = bindings->erase( merged.second );
                        // update root binding (narrow widening as needed, or set new binding for changed root)
                        if ( data1.type ) {
                                if ( data1.allowWidening != widen1 ) {
                                        data1.allowWidening = widen1;
                                        bindings = bindings->set( merged.first, data1 );
                                } else if ( merged.first == class2.get_root() ) {
                                        bindings = bindings->set( merged.first, data1 );
                                }
                        } else /* if ( data2.type ) */ {
                                if ( data2.allowWidening != widen2 ) {
                                        data2.allowWidening = widen2;
                                        bindings = bindings->set( merged.first, data2 );
                                } else if ( merged.first == class1.get_root() ) {
                                        bindings = bindings->set( merged.first, data2 );
                                }
                        }
                } else if ( class1 ) {
                        // add unbound var2 to class1
                        classes = classes->add( class2.get_root() );
                        auto merged = mergeClasses( class1.get_root(), class2.get_root() );
                        // update bindings (narrow as needed, or switch binding to root)
                        if ( merged.first == class2.get_root() ) {
                                data1.allowWidening = widen1;
                                bindings = bindings->erase( merged.second )->set( merged.first, data1 );
                        } else if ( data1.allowWidening != widen1 ) {
                                bindings = bindings->set( merged.first, data1 );
                        }
                } else if ( class2 ) {
                        // add unbound var1 to class1
                        classes = classes->add( class1.get_root() );
                        auto merged = mergeClasses( class1.get_root(), class2.get_root() );
                        // update bindings (narrow as needed, or switch binding to root)
                        if ( merged.first == class1.get_root() ) {
                                data2.allowWidening = widen2;
                                bindings = bindings->erase( merged.second )->set( merged.first, data2 );
                        } else if ( data2.allowWidening != widen2 ) {
                                bindings = bindings->set( merged.first, data2 );
                        }
                } else {
                        // make new class with pair of unbound vars
                        classes = classes->add( class1.get_root() )->add( class2.get_root() );
                        auto merged = mergeClasses( class1.get_root(), class2.get_root() );
                        bindings = bindings->set( merged.first, BoundType{ nullptr, widen1 && widen2, data } );
                }
                return true;
        }

        void TypeEnvironment::add( const Type::ForallList &tyDecls ) {
                PRE_POST_VALIDATE
                for ( Type::ForallList::const_iterator i = tyDecls.begin(); i != tyDecls.end(); ++i ) {
                        interned_string name = (*i)->get_name();
                        classes = classes->add( name );
                        bindings = bindings->set( name, *i );
                } // for
        }

        void TypeEnvironment::add( const TypeSubstitution & sub ) {
                PRE_POST_VALIDATE
                interned_string not_found{nullptr};

                for ( auto p : sub ) {
                        interned_string var = p.first;
                        
                        // filter overlapping classes out of existing environment
                        // xxx - this is a very shady assumption, but has worked for a long time...
                        interned_string root = classes->find_or_default( var, not_found );
                        if ( root != not_found ) {
                                classes = classes->remove_class( root );
                                bindings = bindings->erase( root );
                        }

                        // Minimal assumptions. Not technically correct, but might be good enough, and
                        // is the best we can do at the moment since information is lost in the
                        // transition to TypeSubstitution
                        TypeDecl::Data data{ TypeDecl::Dtype, false };

                        // add variable to class and bindings
                        classes = classes->add( var );
                        bindings = bindings->set( var, BoundType{ p.second->clone(), false, data } );
                }
        }

        void TypeEnvironment::makeSubstitution( TypeSubstitution &sub ) const {
                PRE_POST_VALIDATE_NOM
                bindings->for_each([&]( interned_string root, const BoundType& bound ){
                        classes->for_class(root, [&]( interned_string var ) {
                                if ( bound.type ) {
                                        sub.add( var, bound.type );
                                } else if ( var != root ) {
                                        sub.add( var, new TypeInstType{ 
                                                Type::Qualifiers{}, root, bound.data.kind == TypeDecl::Ftype } );
                                }
                        });
                });

                sub.normalize();
        }

        void TypeEnvironment::print( std::ostream &os, Indenter indent ) const {
                bindings->for_each([&]( interned_string root, const BoundType& bound ) {
                        os << "( ";
                        classes->for_class( root, [&os]( interned_string var ) { os << var << " "; } );
                        os << ")";
                        if ( bound.type ) {
                                os << " -> ";
                                bound.type->print( os, indent+1 );
                        }
                        if ( ! bound.allowWidening ) {
                                os << " (no widening)";
                        }
                        os << std::endl;
                });
        }

        namespace {
                // temporary representation of an equivalence class
                struct EqvClass {
                        std::vector<interned_string> vars;
                        BoundType bound;

                        EqvClass() = default;
                        EqvClass(const BoundType& b) : bound{b} {}
                };
        }

        void TypeEnvironment::simpleCombine( const TypeEnvironment &o ) {
                PRE_POST_VALIDATE
                // check for same environment
                if ( classes == o.classes && bindings == o.bindings ) return;

                // read out equivalence classes (avoids conflicting reroots)
                std::vector<EqvClass> ecs;
                o.bindings->for_each( [&]( interned_string root, const BoundType& bound ) {
                        ecs.emplace_back(bound);
                        o.classes->for_class( root, [&]( interned_string var ) {
                                ecs.back().vars.push_back( var );
                        } );
                } );

                // read equivalence classes into self
                for ( EqvClass& ec : ecs ) {
                        // merge vars
                        interned_string new_root{nullptr};
                        for ( interned_string var : ec.vars ) {
                                Classes* new_classes = classes->add( var );
                                if ( new_classes == classes ) { var = classes->find( var ); }
                                else { classes = new_classes; }
                                new_root = new_root ? mergeClasses( new_root, var ).first : var;
                        }
                        // set binding
                        bindings = bindings->set( new_root, ec.bound );
                }
        }

        void TypeEnvironment::extractOpenVars( OpenVarSet &openVars ) const {
                bindings->for_each( [&]( interned_string root, const BoundType& bound ) {
                        classes->for_class( root, [&openVars,&bound]( interned_string var ) {
                                openVars[ var ] = bound.data;
                        } );
                } );
        }

        void TypeEnvironment::addActual( const TypeEnvironment& actualEnv, OpenVarSet& openVars ) {
                PRE_POST_VALIDATE
                if ( classes == actualEnv.classes && bindings == actualEnv.bindings ) {
                        // actualEnv already the same, just need to update openVars
                        extractOpenVars( openVars );
                        return;
                } else assertf(classes != actualEnv.classes && bindings != actualEnv.bindings, "classes & bindings updated together");

                // read out equivalence classes (avoids conflicting reroots)
                std::vector<EqvClass> ecs;
                actualEnv.bindings->for_each( [&]( interned_string root, const BoundType& bound ) {
                        ecs.emplace_back(bound);
                        actualEnv.classes->for_class( root, [&]( interned_string var ) {
                                ecs.back().vars.push_back( var );
                        } );
                } );

                // add members of new class, setting openVars concurrently
                for ( EqvClass& ec : ecs ) {
                        // merge vars
                        interned_string new_root{nullptr};
                        for ( interned_string var : ec.vars ) {
                                openVars[ var ] = ec.bound.data;
                                Classes* new_classes = classes->add( var );
                                if ( new_classes == classes ) {
                                        // xxx - this case is a bit sketchy, but has been working
                                        // xxx - merging the classes is a departure from previous behaviour
                                        var = classes->find( var );
                                } else { classes = new_classes; }
                                new_root = new_root ? mergeClasses( new_root, var ).first : var;
                        }
                        // set binding without widening
                        bindings = bindings->set( new_root, 
                                BoundType{ maybeClone(ec.bound.type), false, ec.bound.data } );
                }
        }

        void TypeEnvironment::forbidWidening() {
                PRE_POST_VALIDATE
                bindings = bindings->mutate_each([]( const interned_string&, BoundType& c ) {
                        if ( c.allowWidening ) {
                                option<BoundType> ret = c;
                                c.allowWidening = false;
                                return ret;
                        } else return option<BoundType>{};
                });
        }

        std::ostream & operator<<( std::ostream & out, const TypeEnvironment & env ) {
                env.print( out );
                return out;
        }

        PassVisitor<GcTracer> & operator<<( PassVisitor<GcTracer> & gc, const TypeEnvironment & env ) {
                gc.pass.visit( env );
                // for ( ClassRef c : env ) {
                //      maybeAccept( c.get_bound().type, gc );
                // }
                return gc;
        }
} // namespace ResolvExpr

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