1 | // |
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2 | // Cforall Version 1.0.0 Copyright (C) 2015 University of Waterloo |
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3 | // |
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4 | // The contents of this file are covered under the licence agreement in the |
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5 | // file "LICENCE" distributed with Cforall. |
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6 | // |
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7 | // TypeEnvironment.cpp -- |
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8 | // |
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9 | // Author : Aaron B. Moss |
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10 | // Created On : Wed May 29 11:00:00 2019 |
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11 | // Last Modified By : Aaron B. Moss |
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12 | // Last Modified On : Wed May 29 11:00:00 2019 |
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13 | // Update Count : 1 |
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14 | // |
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15 | |
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16 | #include "TypeEnvironment.hpp" |
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17 | |
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18 | #include <algorithm> // for copy |
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19 | #include <cassert> |
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20 | #include <iterator> // for ostream_iterator |
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21 | #include <iostream> |
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22 | #include <string> |
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23 | #include <utility> // for move |
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24 | #include <vector> |
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25 | |
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26 | #include "Decl.hpp" |
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27 | #include "Node.hpp" |
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28 | #include "Pass.hpp" |
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29 | #include "Print.hpp" |
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30 | #include "Type.hpp" |
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31 | #include "Common/Indenter.h" |
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32 | #include "ResolvExpr/typeops.h" // for occurs |
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33 | #include "ResolvExpr/WidenMode.h" |
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34 | #include "ResolvExpr/Unify.h" // for unifyInexact |
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35 | #include "Tuples/Tuples.h" // for isTtype |
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36 | |
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37 | using ResolvExpr::WidenMode; |
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38 | |
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39 | namespace ast { |
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40 | |
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41 | void print( std::ostream & out, const AssertionSet & assns, Indenter indent ) { |
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42 | for ( const auto & i : assns ) { |
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43 | print( out, i.first, indent ); |
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44 | out << ( i.second.isUsed ? " (used)" : " (not used)" ); |
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45 | } |
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46 | } |
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47 | |
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48 | void print( std::ostream & out, const OpenVarSet & open, Indenter indent ) { |
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49 | out << indent; |
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50 | bool first = true; |
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51 | for ( const auto & i : open ) { |
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52 | if ( first ) { first = false; } else { out << ' '; } |
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53 | out << i.first << "(" << i.second << ")"; |
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54 | } |
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55 | } |
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56 | |
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57 | void print( std::ostream & out, const EqvClass & clz, Indenter indent ) { |
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58 | out << "( "; |
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59 | std::copy( clz.vars.begin(), clz.vars.end(), std::ostream_iterator< std::string >( out, " " ) ); |
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60 | out << ")"; |
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61 | |
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62 | if ( clz.bound ) { |
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63 | out << " -> "; |
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64 | print( out, clz.bound, indent+1 ); |
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65 | } |
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66 | |
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67 | if ( ! clz.allowWidening ) { |
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68 | out << " (no widening)"; |
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69 | } |
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70 | |
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71 | out << std::endl; |
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72 | } |
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73 | |
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74 | const EqvClass * TypeEnvironment::lookup( const std::string & var ) const { |
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75 | for ( ClassList::const_iterator i = env.begin(); i != env.end(); ++i ) { |
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76 | if ( i->vars.find( var ) != i->vars.end() ) return &*i; |
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77 | } |
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78 | return nullptr; |
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79 | } |
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80 | |
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81 | namespace { |
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82 | /// Removes any class from env that intersects eqvClass |
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83 | void filterOverlappingClasses( std::list<EqvClass> & env, const EqvClass & eqvClass ) { |
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84 | auto i = env.begin(); |
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85 | while ( i != env.end() ) { |
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86 | auto next = i; ++next; // save next node in case of erasure |
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87 | |
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88 | for ( const auto & v : eqvClass.vars ) { |
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89 | if ( i->vars.count( v ) ) { |
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90 | env.erase( i ); // remove overlapping class |
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91 | break; // done with this class |
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92 | } |
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93 | } |
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94 | |
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95 | i = next; // go to next node even if this removed |
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96 | } |
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97 | } |
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98 | } |
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99 | |
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100 | void TypeEnvironment::add( const ParameterizedType::ForallList & tyDecls ) { |
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101 | for ( const TypeDecl * tyDecl : tyDecls ) { |
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102 | env.emplace_back( tyDecl ); |
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103 | } |
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104 | } |
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105 | |
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106 | void TypeEnvironment::add( const TypeSubstitution & sub ) { |
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107 | for ( const auto p : sub ) { |
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108 | add( EqvClass{ p.first, p.second } ); |
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109 | } |
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110 | } |
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111 | |
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112 | void TypeEnvironment::writeToSubstitution( TypeSubstitution & sub ) const { |
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113 | for ( const auto & clz : env ) { |
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114 | std::string clzRep; |
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115 | for ( const auto & var : clz.vars ) { |
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116 | if ( clz.bound ) { |
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117 | sub.add( var, clz.bound ); |
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118 | } else if ( clzRep.empty() ) { |
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119 | clzRep = var; |
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120 | } else { |
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121 | sub.add( var, new TypeInstType{ clzRep, clz.data.kind } ); |
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122 | } |
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123 | } |
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124 | } |
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125 | sub.normalize(); |
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126 | } |
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127 | |
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128 | void TypeEnvironment::simpleCombine( const TypeEnvironment & o ) { |
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129 | env.insert( env.end(), o.env.begin(), o.env.end() ); |
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130 | } |
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131 | |
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132 | namespace { |
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133 | /// Implements occurs check by traversing type |
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134 | struct Occurs : public ast::WithVisitorRef<Occurs> { |
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135 | bool result; |
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136 | std::set< std::string > vars; |
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137 | const TypeEnvironment & tenv; |
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138 | |
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139 | Occurs( const std::string & var, const TypeEnvironment & env ) |
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140 | : result( false ), vars(), tenv( env ) { |
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141 | if ( const EqvClass * clz = tenv.lookup( var ) ) { |
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142 | vars = clz->vars; |
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143 | } else { |
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144 | vars.emplace( var ); |
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145 | } |
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146 | } |
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147 | |
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148 | void previsit( const TypeInstType * typeInst ) { |
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149 | if ( vars.count( typeInst->name ) ) { |
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150 | result = true; |
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151 | } else if ( const EqvClass * clz = tenv.lookup( typeInst->name ) ) { |
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152 | if ( clz->bound ) { |
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153 | clz->bound->accept( *visitor ); |
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154 | } |
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155 | } |
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156 | } |
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157 | }; |
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158 | |
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159 | /// true if `var` occurs in `ty` under `env` |
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160 | bool occurs( const Type * ty, const std::string & var, const TypeEnvironment & env ) { |
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161 | Pass<Occurs> occur{ var, env }; |
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162 | maybe_accept( ty, occur ); |
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163 | return occur.pass.result; |
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164 | } |
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165 | } |
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166 | |
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167 | bool TypeEnvironment::combine( |
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168 | const TypeEnvironment & o, OpenVarSet & open, const SymbolTable & symtab ) { |
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169 | // short-circuit easy cases |
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170 | if ( o.empty() ) return true; |
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171 | if ( empty() ) { |
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172 | simpleCombine( o ); |
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173 | return true; |
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174 | } |
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175 | |
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176 | // merge classes |
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177 | for ( const EqvClass & c : o.env ) { |
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178 | // index of typeclass in local environment bound to c |
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179 | auto rt = env.end(); |
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180 | |
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181 | // look for first existing bound variable |
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182 | auto vt = c.vars.begin(); |
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183 | for ( ; vt != c.vars.end(); ++vt ) { |
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184 | rt = internal_lookup( *vt ); |
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185 | if ( rt != env.end() ) break; |
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186 | } |
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187 | |
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188 | if ( rt != env.end() ) { // c needs to be merged into *rt |
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189 | EqvClass & r = *rt; |
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190 | // merge bindings |
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191 | if ( ! mergeBound( r, c, open, symtab ) ) return false; |
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192 | // merge previous unbound variables into this class, checking occurs if needed |
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193 | if ( r.bound ) for ( const auto & u : c.vars ) { |
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194 | if ( occurs( r.bound, u, *this ) ) return false; |
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195 | r.vars.emplace( u ); |
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196 | } else { r.vars.insert( c.vars.begin(), vt ); } |
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197 | // merge subsequent variables into this class (skipping *vt, already there) |
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198 | while ( ++vt != c.vars.end() ) { |
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199 | auto st = internal_lookup( *vt ); |
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200 | if ( st == env.end() ) { |
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201 | // unbound, safe to add if occurs |
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202 | if ( r.bound && occurs( r.bound, *vt, *this ) ) return false; |
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203 | r.vars.emplace( *vt ); |
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204 | } else if ( st != rt ) { |
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205 | // bound, but not to the same class |
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206 | if ( ! mergeClasses( rt, st, open, symtab ) ) return false; |
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207 | } // ignore bound into the same class |
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208 | } |
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209 | } else { // no variables in c bound; just copy up |
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210 | env.emplace_back( c ); |
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211 | } |
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212 | } |
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213 | |
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214 | // merged all classes |
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215 | return true; |
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216 | } |
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217 | |
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218 | void TypeEnvironment::extractOpenVars( OpenVarSet & open ) const { |
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219 | for ( const auto & clz : env ) { |
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220 | for ( const auto & var : clz.vars ) { |
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221 | open[ var ] = clz.data; |
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222 | } |
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223 | } |
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224 | } |
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225 | |
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226 | void TypeEnvironment::addActual( const TypeEnvironment & actualEnv, OpenVarSet & open ) { |
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227 | for ( const auto & clz : actualEnv ) { |
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228 | EqvClass c = clz; |
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229 | c.allowWidening = false; |
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230 | for ( const auto & var : c.vars ) { |
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231 | open[ var ] = c.data; |
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232 | } |
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233 | env.emplace_back( std::move(c) ); |
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234 | } |
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235 | } |
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236 | |
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237 | namespace { |
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238 | /// true if a type is a function type |
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239 | bool isFtype( const Type * type ) { |
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240 | if ( dynamic_cast< const FunctionType * >( type ) ) { |
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241 | return true; |
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242 | } else if ( auto typeInst = dynamic_cast< const TypeInstType * >( type ) ) { |
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243 | return typeInst->kind == TypeVar::Ftype; |
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244 | } else return false; |
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245 | } |
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246 | |
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247 | /// true if the given type can be bound to the given type variable |
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248 | bool tyVarCompatible( const TypeDecl::Data & data, const Type * type ) { |
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249 | switch ( data.kind ) { |
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250 | case TypeVar::Dtype: |
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251 | // to bind to an object type variable, the type must not be a function type. |
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252 | // if the type variable is specified to be a complete type then the incoming |
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253 | // type must also be complete |
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254 | // xxx - should this also check that type is not a tuple type and that it's not a ttype? |
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255 | return ! isFtype( type ) && ( ! data.isComplete || type->isComplete() ); |
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256 | case TypeVar::Ftype: |
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257 | return isFtype( type ); |
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258 | case TypeVar::Ttype: |
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259 | // ttype unifies with any tuple type |
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260 | return dynamic_cast< const TupleType * >( type ) || Tuples::isTtype( type ); |
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261 | default: |
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262 | assertf(false, "Unhandled tyvar kind: %d", data.kind); |
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263 | return false; |
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264 | } |
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265 | } |
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266 | } |
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267 | |
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268 | bool TypeEnvironment::bindVar( |
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269 | const TypeInstType * typeInst, const Type * bindTo, const TypeDecl::Data & data, |
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270 | AssertionSet & need, AssertionSet & have, const OpenVarSet & open, WidenMode widen, |
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271 | const SymbolTable & symtab |
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272 | ) { |
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273 | // remove references from bound type, so that type variables can only bind to value types |
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274 | ptr<Type> target = bindTo->stripReferences(); |
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275 | auto tyvar = open.find( typeInst->name ); |
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276 | assert( tyvar != open.end() ); |
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277 | if ( ! tyVarCompatible( tyvar->second, target ) ) return false; |
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278 | if ( occurs( target, typeInst->name, *this ) ) return false; |
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279 | |
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280 | auto it = internal_lookup( typeInst->name ); |
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281 | if ( it != env.end() ) { |
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282 | if ( it->bound ) { |
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283 | // attempt to unify equivalence class type with type to bind to. |
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284 | // equivalence class type has stripped qualifiers which must be restored |
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285 | ptr<Type> common; |
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286 | ptr<Type> newType = it->bound; |
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287 | newType.get_and_mutate()->qualifiers = typeInst->qualifiers; |
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288 | if ( unifyInexact( |
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289 | newType, target, *this, need, have, open, |
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290 | widen & WidenMode{ it->allowWidening, true }, symtab, common ) ) { |
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291 | if ( common ) { |
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292 | it->bound = std::move(common); |
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293 | clear_qualifiers( it->bound ); |
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294 | } |
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295 | } else return false; |
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296 | } else { |
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297 | it->bound = std::move(target); |
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298 | clear_qualifiers( it->bound ); |
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299 | it->allowWidening = widen.first && widen.second; |
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300 | } |
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301 | } else { |
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302 | env.emplace_back( |
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303 | typeInst->name, target, widen.first && widen.second, data ); |
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304 | } |
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305 | return true; |
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306 | } |
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307 | |
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308 | bool TypeEnvironment::bindVarToVar( |
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309 | const TypeInstType * var1, const TypeInstType * var2, TypeDecl::Data && data, |
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310 | AssertionSet & need, AssertionSet & have, const OpenVarSet & open, |
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311 | WidenMode widen, const SymbolTable & symtab |
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312 | ) { |
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313 | auto c1 = internal_lookup( var1->name ); |
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314 | auto c2 = internal_lookup( var2->name ); |
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315 | |
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316 | // exit early if variables already bound together |
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317 | if ( c1 != env.end() && c1 == c2 ) { |
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318 | c1->allowWidening &= widen; |
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319 | return true; |
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320 | } |
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321 | |
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322 | bool widen1 = false, widen2 = false; |
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323 | const Type * type1 = nullptr, * type2 = nullptr; |
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324 | |
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325 | // check for existing bindings, perform occurs check |
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326 | if ( c1 != env.end() ) { |
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327 | if ( c1->bound ) { |
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328 | if ( occurs( c1->bound, var2->name, *this ) ) return false; |
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329 | type1 = c1->bound; |
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330 | } |
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331 | widen1 = widen.first && c1->allowWidening; |
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332 | } |
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333 | if ( c2 != env.end() ) { |
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334 | if ( c2->bound ) { |
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335 | if ( occurs( c2->bound, var1->name, *this ) ) return false; |
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336 | type2 = c2->bound; |
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337 | } |
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338 | widen2 = widen.second && c2->allowWidening; |
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339 | } |
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340 | |
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341 | if ( type1 && type2 ) { |
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342 | // both classes bound, merge if bound types can be unified |
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343 | ptr<Type> newType1{ type1 }, newType2{ type2 }; |
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344 | WidenMode newWidenMode{ widen1, widen2 }; |
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345 | ptr<Type> common; |
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346 | |
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347 | if ( unifyInexact( |
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348 | newType1, newType2, *this, need, have, open, newWidenMode, symtab, common ) ) { |
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349 | c1->vars.insert( c2->vars.begin(), c2->vars.end() ); |
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350 | c1->allowWidening = widen1 && widen2; |
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351 | if ( common ) { |
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352 | c1->bound = std::move(common); |
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353 | clear_qualifiers( c1->bound ); |
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354 | } |
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355 | c1->data.isComplete |= data.isComplete; |
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356 | env.erase( c2 ); |
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357 | } else return false; |
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358 | } else if ( c1 != env.end() && c2 != env.end() ) { |
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359 | // both classes exist, at least one unbound, merge unconditionally |
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360 | if ( type1 ) { |
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361 | c1->vars.insert( c2->vars.begin(), c2->vars.end() ); |
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362 | c1->allowWidening = widen1; |
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363 | c1->data.isComplete |= data.isComplete; |
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364 | env.erase( c2 ); |
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365 | } else { |
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366 | c2->vars.insert( c1->vars.begin(), c1->vars.end() ); |
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367 | c2->allowWidening = widen2; |
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368 | c2->data.isComplete |= data.isComplete; |
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369 | env.erase( c1 ); |
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370 | } |
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371 | } else if ( c1 != env.end() ) { |
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372 | // var2 unbound, add to env[c1] |
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373 | c1->vars.emplace( var2->name ); |
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374 | c1->allowWidening = widen1; |
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375 | c1->data.isComplete |= data.isComplete; |
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376 | } else if ( c2 != env.end() ) { |
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377 | // var1 unbound, add to env[c2] |
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378 | c2->vars.emplace( var1->name ); |
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379 | c2->allowWidening = widen2; |
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380 | c2->data.isComplete |= data.isComplete; |
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381 | } else { |
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382 | // neither var bound, create new class |
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383 | env.emplace_back( var1->name, var2->name, widen1 && widen2, data ); |
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384 | } |
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385 | |
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386 | return true; |
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387 | } |
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388 | |
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389 | void TypeEnvironment::forbidWidening() { |
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390 | for ( EqvClass& c : env ) c.allowWidening = false; |
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391 | } |
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392 | |
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393 | void TypeEnvironment::add( EqvClass && eqvClass ) { |
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394 | filterOverlappingClasses( env, eqvClass ); |
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395 | env.emplace_back( std::move(eqvClass) ); |
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396 | } |
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397 | |
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398 | bool TypeEnvironment::mergeBound( |
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399 | EqvClass & to, const EqvClass & from, OpenVarSet & open, const SymbolTable & symtab ) { |
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400 | if ( from.bound ) { |
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401 | if ( to.bound ) { |
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402 | // attempt to unify bound types |
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403 | ptr<Type> toType{ to.bound }, fromType{ from.bound }; |
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404 | WidenMode widen{ to.allowWidening, from.allowWidening }; |
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405 | ptr<Type> common; |
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406 | AssertionSet need, have; |
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407 | |
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408 | if ( unifyInexact( |
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409 | toType, fromType, *this, need, have, open, widen, symtab, common ) ) { |
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410 | // unifies, set common type if necessary |
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411 | if ( common ) { |
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412 | to.bound = std::move(common); |
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413 | clear_qualifiers( to.bound ); |
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414 | } |
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415 | } else return false; // cannot unify |
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416 | } else { |
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417 | to.bound = from.bound; |
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418 | } |
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419 | } |
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420 | |
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421 | // unify widening if matches |
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422 | to.allowWidening &= from.allowWidening; |
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423 | return true; |
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424 | } |
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425 | |
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426 | bool TypeEnvironment::mergeClasses( |
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427 | ClassList::iterator to, ClassList::iterator from, OpenVarSet & open, const SymbolTable & symtab |
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428 | ) { |
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429 | EqvClass & r = *to, & s = *from; |
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430 | |
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431 | // ensure bounds match |
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432 | if ( ! mergeBound( r, s, open, symtab ) ) return false; |
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433 | |
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434 | // check safely bindable |
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435 | if ( r.bound ) { |
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436 | for ( const auto & v : s.vars ) if ( occurs( r.bound, v, *this ) ) return false; |
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437 | } |
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438 | |
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439 | // merge classes |
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440 | r.vars.insert( s.vars.begin(), s.vars.end() ); |
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441 | r.allowWidening &= s.allowWidening; |
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442 | env.erase( from ); |
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443 | |
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444 | return true; |
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445 | } |
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446 | |
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447 | TypeEnvironment::ClassList::iterator TypeEnvironment::internal_lookup( const std::string & var ) { |
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448 | for ( ClassList::iterator i = env.begin(); i != env.end(); ++i ) { |
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449 | if ( i->vars.count( var ) ) return i; |
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450 | } |
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451 | return env.end(); |
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452 | } |
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453 | |
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454 | void print( std::ostream & out, const TypeEnvironment & env, Indenter indent ) { |
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455 | for ( const auto & clz : env ) { |
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456 | print( out, clz, indent ); |
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457 | } |
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458 | } |
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459 | |
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460 | std::ostream & operator<<( std::ostream & out, const TypeEnvironment & env ) { |
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461 | print( out, env ); |
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462 | return out; |
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463 | } |
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464 | |
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465 | } |
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466 | |
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467 | // Local Variables: // |
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468 | // tab-width: 4 // |
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469 | // mode: c++ // |
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470 | // compile-command: "make install" // |
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471 | // End: // |
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