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1 ------------------------------------------------------------------------------
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2 -- --
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3 -- GNAT COMPILER COMPONENTS --
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4 -- --
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5 -- L I V E --
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6 -- --
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7 -- B o d y --
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8 -- --
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131
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9 -- Copyright (C) 2000-2018, Free Software Foundation, Inc. --
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111
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10 -- --
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11 -- GNAT is free software; you can redistribute it and/or modify it under --
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12 -- terms of the GNU General Public License as published by the Free Soft- --
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13 -- ware Foundation; either version 3, or (at your option) any later ver- --
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14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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16 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
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17 -- for more details. You should have received a copy of the GNU General --
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18 -- Public License distributed with GNAT; see file COPYING3. If not, go to --
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19 -- http://www.gnu.org/licenses for a complete copy of the license. --
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20 -- --
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21 -- GNAT was originally developed by the GNAT team at New York University. --
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22 -- Extensive contributions were provided by Ada Core Technologies Inc. --
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23 -- --
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24 ------------------------------------------------------------------------------
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25
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26 with Atree; use Atree;
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27 with Einfo; use Einfo;
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28 with Lib; use Lib;
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29 with Nlists; use Nlists;
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30 with Sem_Aux; use Sem_Aux;
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31 with Sem_Util; use Sem_Util;
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32 with Sinfo; use Sinfo;
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33 with Types; use Types;
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34
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35 package body Live is
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36
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37 -- Name_Set
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38
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39 -- The Name_Set type is used to store the temporary mark bits used by the
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40 -- garbage collection of entities. Using a separate array prevents using up
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41 -- any valuable per-node space and possibly results in better locality and
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42 -- cache usage.
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43
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44 type Name_Set is array (Node_Id range <>) of Boolean;
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45 pragma Pack (Name_Set);
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46
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47 function Marked (Marks : Name_Set; Name : Node_Id) return Boolean;
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48 pragma Inline (Marked);
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49
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50 procedure Set_Marked
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51 (Marks : in out Name_Set;
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52 Name : Node_Id;
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53 Mark : Boolean := True);
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54 pragma Inline (Set_Marked);
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55
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56 -- Algorithm
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57
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58 -- The problem of finding live entities is solved in two steps:
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59
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60 procedure Mark (Root : Node_Id; Marks : out Name_Set);
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61 -- Mark all live entities in Root as Marked
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62
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63 procedure Sweep (Root : Node_Id; Marks : Name_Set);
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64 -- For all unmarked entities in Root set Is_Eliminated to true
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65
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66 -- The Mark phase is split into two phases:
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67
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68 procedure Init_Marked (Root : Node_Id; Marks : out Name_Set);
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69 -- For all subprograms, reset Is_Public flag if a pragma Eliminate applies
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70 -- to the entity, and set the Marked flag to Is_Public.
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71
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72 procedure Trace_Marked (Root : Node_Id; Marks : in out Name_Set);
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73 -- Traverse the tree skipping any unmarked subprogram bodies. All visited
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74 -- entities are marked, as well as entities denoted by a visited identifier
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75 -- or operator. When an entity is first marked it is traced as well.
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76
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77 -- Local functions
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78
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79 function Body_Of (E : Entity_Id) return Node_Id;
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80 -- Returns subprogram body corresponding to entity E
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81
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82 function Spec_Of (N : Node_Id) return Entity_Id;
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83 -- Given a subprogram body N, return defining identifier of its declaration
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84
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85 -- ??? the body of this package contains no comments at all, this
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86 -- should be fixed.
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87
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88 -------------
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89 -- Body_Of --
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90 -------------
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91
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92 function Body_Of (E : Entity_Id) return Node_Id is
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93 Decl : constant Node_Id := Unit_Declaration_Node (E);
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94 Kind : constant Node_Kind := Nkind (Decl);
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95 Result : Node_Id;
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96
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97 begin
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98 if Kind = N_Subprogram_Body then
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99 Result := Decl;
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100
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101 elsif Kind /= N_Subprogram_Declaration
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102 and Kind /= N_Subprogram_Body_Stub
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103 then
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104 Result := Empty;
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105
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106 else
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107 Result := Corresponding_Body (Decl);
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108
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109 if Result /= Empty then
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110 Result := Unit_Declaration_Node (Result);
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111 end if;
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112 end if;
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113
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114 return Result;
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115 end Body_Of;
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116
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117 ------------------------------
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118 -- Collect_Garbage_Entities --
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119 ------------------------------
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120
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121 procedure Collect_Garbage_Entities is
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122 Root : constant Node_Id := Cunit (Main_Unit);
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123 Marks : Name_Set (0 .. Last_Node_Id);
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124
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125 begin
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126 Mark (Root, Marks);
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127 Sweep (Root, Marks);
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128 end Collect_Garbage_Entities;
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129
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130 -----------------
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131 -- Init_Marked --
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132 -----------------
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133
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134 procedure Init_Marked (Root : Node_Id; Marks : out Name_Set) is
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135
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136 function Process (N : Node_Id) return Traverse_Result;
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137 procedure Traverse is new Traverse_Proc (Process);
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138
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139 -------------
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140 -- Process --
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141 -------------
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142
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143 function Process (N : Node_Id) return Traverse_Result is
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144 begin
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145 case Nkind (N) is
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146 when N_Entity'Range =>
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147 if Is_Eliminated (N) then
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148 Set_Is_Public (N, False);
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149 end if;
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150
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151 Set_Marked (Marks, N, Is_Public (N));
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152
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153 when N_Subprogram_Body =>
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154 Traverse (Spec_Of (N));
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155
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156 when N_Package_Body_Stub =>
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157 if Present (Library_Unit (N)) then
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158 Traverse (Proper_Body (Unit (Library_Unit (N))));
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159 end if;
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160
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161 when N_Package_Body =>
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162 declare
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163 Elmt : Node_Id := First (Declarations (N));
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164 begin
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165 while Present (Elmt) loop
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166 Traverse (Elmt);
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167 Next (Elmt);
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168 end loop;
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169 end;
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170
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171 when others =>
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172 null;
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173 end case;
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174
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175 return OK;
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176 end Process;
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177
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178 -- Start of processing for Init_Marked
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179
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180 begin
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181 Marks := (others => False);
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182 Traverse (Root);
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183 end Init_Marked;
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184
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185 ----------
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186 -- Mark --
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187 ----------
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188
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189 procedure Mark (Root : Node_Id; Marks : out Name_Set) is
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190 begin
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191 Init_Marked (Root, Marks);
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192 Trace_Marked (Root, Marks);
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193 end Mark;
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194
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195 ------------
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196 -- Marked --
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197 ------------
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198
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199 function Marked (Marks : Name_Set; Name : Node_Id) return Boolean is
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200 begin
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201 return Marks (Name);
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202 end Marked;
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203
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204 ----------------
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205 -- Set_Marked --
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206 ----------------
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207
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208 procedure Set_Marked
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209 (Marks : in out Name_Set;
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210 Name : Node_Id;
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211 Mark : Boolean := True)
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212 is
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213 begin
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214 Marks (Name) := Mark;
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215 end Set_Marked;
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216
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217 -------------
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218 -- Spec_Of --
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219 -------------
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220
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221 function Spec_Of (N : Node_Id) return Entity_Id is
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222 begin
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223 if Acts_As_Spec (N) then
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224 return Defining_Entity (N);
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225 else
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226 return Corresponding_Spec (N);
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227 end if;
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228 end Spec_Of;
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229
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230 -----------
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231 -- Sweep --
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232 -----------
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233
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234 procedure Sweep (Root : Node_Id; Marks : Name_Set) is
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235
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236 function Process (N : Node_Id) return Traverse_Result;
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237 procedure Traverse is new Traverse_Proc (Process);
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238
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239 -------------
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240 -- Process --
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241 -------------
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242
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243 function Process (N : Node_Id) return Traverse_Result is
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244 begin
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245 case Nkind (N) is
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246 when N_Entity'Range =>
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247 Set_Is_Eliminated (N, not Marked (Marks, N));
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248
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249 when N_Subprogram_Body =>
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250 Traverse (Spec_Of (N));
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251
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252 when N_Package_Body_Stub =>
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253 if Present (Library_Unit (N)) then
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254 Traverse (Proper_Body (Unit (Library_Unit (N))));
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255 end if;
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256
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257 when N_Package_Body =>
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258 declare
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259 Elmt : Node_Id := First (Declarations (N));
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260 begin
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261 while Present (Elmt) loop
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262 Traverse (Elmt);
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263 Next (Elmt);
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264 end loop;
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265 end;
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266
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267 when others =>
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268 null;
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269 end case;
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270
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271 return OK;
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272 end Process;
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273
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274 -- Start of processing for Sweep
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275
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276 begin
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277 Traverse (Root);
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278 end Sweep;
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279
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280 ------------------
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281 -- Trace_Marked --
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282 ------------------
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283
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284 procedure Trace_Marked (Root : Node_Id; Marks : in out Name_Set) is
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285
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286 function Process (N : Node_Id) return Traverse_Result;
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287 procedure Process (N : Node_Id);
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288 procedure Traverse is new Traverse_Proc (Process);
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289
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290 -------------
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291 -- Process --
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292 -------------
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293
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294 procedure Process (N : Node_Id) is
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295 Result : Traverse_Result;
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296 pragma Warnings (Off, Result);
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297
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298 begin
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299 Result := Process (N);
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300 end Process;
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301
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302 function Process (N : Node_Id) return Traverse_Result is
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303 Result : Traverse_Result := OK;
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304 B : Node_Id;
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305 E : Entity_Id;
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306
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307 begin
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308 case Nkind (N) is
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309 when N_Generic_Declaration'Range
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310 | N_Pragma
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311 | N_Subprogram_Body_Stub
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312 | N_Subprogram_Declaration
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313 =>
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314 Result := Skip;
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315
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316 when N_Subprogram_Body =>
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317 if not Marked (Marks, Spec_Of (N)) then
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318 Result := Skip;
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319 end if;
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320
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321 when N_Package_Body_Stub =>
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322 if Present (Library_Unit (N)) then
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323 Traverse (Proper_Body (Unit (Library_Unit (N))));
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324 end if;
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325
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326 when N_Expanded_Name
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327 | N_Identifier
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328 | N_Operator_Symbol
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329 =>
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330 E := Entity (N);
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331
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332 if E /= Empty and then not Marked (Marks, E) then
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333 Process (E);
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334
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335 if Is_Subprogram (E) then
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336 B := Body_Of (E);
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337
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338 if B /= Empty then
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339 Traverse (B);
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340 end if;
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341 end if;
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342 end if;
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343
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344 when N_Entity'Range =>
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345 if (Ekind (N) = E_Component) and then not Marked (Marks, N) then
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346 if Present (Discriminant_Checking_Func (N)) then
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347 Process (Discriminant_Checking_Func (N));
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348 end if;
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349 end if;
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350
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351 Set_Marked (Marks, N);
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352
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353 when others =>
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354 null;
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355 end case;
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356
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357 return Result;
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358 end Process;
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359
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360 -- Start of processing for Trace_Marked
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361
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362 begin
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363 Traverse (Root);
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364 end Trace_Marked;
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365
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366 end Live;
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