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0
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1 /* Callgraph handling code.
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2 Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008
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3 Free Software Foundation, Inc.
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4 Contributed by Jan Hubicka
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5
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6 This file is part of GCC.
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7
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8 GCC is free software; you can redistribute it and/or modify it under
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9 the terms of the GNU General Public License as published by the Free
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10 Software Foundation; either version 3, or (at your option) any later
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11 version.
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12
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13 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
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15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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16 for more details.
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17
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18 You should have received a copy of the GNU General Public License
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19 along with GCC; see the file COPYING3. If not see
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20 <http://www.gnu.org/licenses/>. */
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21
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22 #include "config.h"
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23 #include "system.h"
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24 #include "coretypes.h"
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25 #include "tm.h"
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26 #include "tree.h"
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27 #include "cgraph.h"
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28 #include "langhooks.h"
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29 #include "diagnostic.h"
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30 #include "hashtab.h"
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31 #include "ggc.h"
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32 #include "timevar.h"
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33 #include "debug.h"
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34 #include "target.h"
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35 #include "output.h"
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36 #include "gimple.h"
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37 #include "tree-flow.h"
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38
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39 /* This file contains basic routines manipulating variable pool.
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40
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41 Varpool acts as interface in between the front-end and middle-end
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42 and drives the decision process on what variables and when are
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43 going to be compiled.
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44
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45 The varpool nodes are allocated lazily for declarations
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46 either by frontend or at callgraph construction time.
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47 All variables supposed to be output into final file needs to be
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48 explicitly marked by frontend via VARPOOL_FINALIZE_DECL function. */
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49
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50 /* Hash table used to convert declarations into nodes. */
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51 static GTY((param_is (struct varpool_node))) htab_t varpool_hash;
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52
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53 /* The linked list of cgraph varpool nodes.
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54 Linked via node->next pointer. */
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55 struct varpool_node *varpool_nodes;
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56
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57 /* Queue of cgraph nodes scheduled to be lowered and output.
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58 The queue is maintained via mark_needed_node, linked via node->next_needed
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59 pointer.
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60
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61 LAST_NEEDED_NODE points to the end of queue, so it can be
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62 maintained in forward order. GTY is needed to make it friendly to
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63 PCH.
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64
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65 During compilation we construct the queue of needed variables
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66 twice: first time it is during cgraph construction, second time it is at the
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67 end of compilation in VARPOOL_REMOVE_UNREFERENCED_DECLS so we can avoid
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68 optimized out variables being output.
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69
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70 Each variable is thus first analyzed and then later possibly output.
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71 FIRST_UNANALYZED_NODE points to first node in queue that was not analyzed
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72 yet and is moved via VARPOOL_ANALYZE_PENDING_DECLS. */
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73
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74 struct varpool_node *varpool_nodes_queue;
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75 static GTY(()) struct varpool_node *varpool_last_needed_node;
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76 static GTY(()) struct varpool_node *varpool_first_unanalyzed_node;
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77
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78 /* Lists all assembled variables to be sent to debugger output later on. */
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79 static GTY(()) struct varpool_node *varpool_assembled_nodes_queue;
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80
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81 /* Return name of the node used in debug output. */
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82 static const char *
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83 varpool_node_name (struct varpool_node *node)
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84 {
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85 return lang_hooks.decl_printable_name (node->decl, 2);
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86 }
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87
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88 /* Returns a hash code for P. */
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89 static hashval_t
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90 hash_varpool_node (const void *p)
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91 {
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92 const struct varpool_node *n = (const struct varpool_node *) p;
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93 return (hashval_t) DECL_UID (n->decl);
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94 }
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95
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96 /* Returns nonzero if P1 and P2 are equal. */
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97 static int
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98 eq_varpool_node (const void *p1, const void *p2)
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99 {
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100 const struct varpool_node *n1 =
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101 (const struct varpool_node *) p1;
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102 const struct varpool_node *n2 =
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103 (const struct varpool_node *) p2;
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104 return DECL_UID (n1->decl) == DECL_UID (n2->decl);
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105 }
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106
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107 /* Return varpool node assigned to DECL. Create new one when needed. */
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108 struct varpool_node *
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109 varpool_node (tree decl)
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110 {
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111 struct varpool_node key, *node, **slot;
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112
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113 gcc_assert (DECL_P (decl) && TREE_CODE (decl) != FUNCTION_DECL);
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114
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115 if (!varpool_hash)
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116 varpool_hash = htab_create_ggc (10, hash_varpool_node,
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117 eq_varpool_node, NULL);
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118 key.decl = decl;
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119 slot = (struct varpool_node **)
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120 htab_find_slot (varpool_hash, &key, INSERT);
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121 if (*slot)
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122 return *slot;
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123 node = GGC_CNEW (struct varpool_node);
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124 node->decl = decl;
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125 node->order = cgraph_order++;
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126 node->next = varpool_nodes;
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127 varpool_nodes = node;
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128 *slot = node;
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129 return node;
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130 }
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131
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132 /* Dump given cgraph node. */
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133 void
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134 dump_varpool_node (FILE *f, struct varpool_node *node)
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135 {
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136 fprintf (f, "%s:", varpool_node_name (node));
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137 fprintf (f, " availability:%s",
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138 cgraph_function_flags_ready
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139 ? cgraph_availability_names[cgraph_variable_initializer_availability (node)]
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140 : "not-ready");
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141 if (DECL_INITIAL (node->decl))
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142 fprintf (f, " initialized");
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143 if (node->needed)
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144 fprintf (f, " needed");
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145 if (node->analyzed)
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146 fprintf (f, " analyzed");
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147 if (node->finalized)
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148 fprintf (f, " finalized");
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149 if (node->output)
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150 fprintf (f, " output");
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151 if (node->externally_visible)
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152 fprintf (f, " externally_visible");
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153 fprintf (f, "\n");
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154 }
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155
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156 /* Dump the variable pool. */
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157 void
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158 dump_varpool (FILE *f)
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159 {
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160 struct varpool_node *node;
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161
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162 fprintf (f, "variable pool:\n\n");
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163 for (node = varpool_nodes; node; node = node->next)
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164 dump_varpool_node (f, node);
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165 }
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166
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167 /* Given an assembler name, lookup node. */
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168 struct varpool_node *
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169 varpool_node_for_asm (tree asmname)
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170 {
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171 struct varpool_node *node;
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172
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173 for (node = varpool_nodes; node ; node = node->next)
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174 if (decl_assembler_name_equal (node->decl, asmname))
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175 return node;
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176
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177 return NULL;
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178 }
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179
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180 /* Helper function for finalization code - add node into lists so it will
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181 be analyzed and compiled. */
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182 static void
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183 varpool_enqueue_needed_node (struct varpool_node *node)
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184 {
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185 if (varpool_last_needed_node)
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186 varpool_last_needed_node->next_needed = node;
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187 varpool_last_needed_node = node;
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188 node->next_needed = NULL;
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189 if (!varpool_nodes_queue)
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190 varpool_nodes_queue = node;
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191 if (!varpool_first_unanalyzed_node)
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192 varpool_first_unanalyzed_node = node;
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193 notice_global_symbol (node->decl);
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194 }
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195
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196 /* Notify finalize_compilation_unit that given node is reachable
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197 or needed. */
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198 void
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199 varpool_mark_needed_node (struct varpool_node *node)
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200 {
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201 if (!node->needed && node->finalized
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202 && !TREE_ASM_WRITTEN (node->decl))
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203 varpool_enqueue_needed_node (node);
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204 node->needed = 1;
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205 }
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206
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207 /* Reset the queue of needed nodes. */
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208 static void
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209 varpool_reset_queue (void)
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210 {
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211 varpool_last_needed_node = NULL;
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212 varpool_nodes_queue = NULL;
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213 varpool_first_unanalyzed_node = NULL;
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214 }
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215
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216 /* Determine if variable DECL is needed. That is, visible to something
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217 either outside this translation unit, something magic in the system
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218 configury */
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219 bool
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220 decide_is_variable_needed (struct varpool_node *node, tree decl)
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221 {
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222 /* If the user told us it is used, then it must be so. */
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223 if (node->externally_visible || node->force_output)
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224 return true;
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225
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226 /* ??? If the assembler name is set by hand, it is possible to assemble
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227 the name later after finalizing the function and the fact is noticed
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228 in assemble_name then. This is arguably a bug. */
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229 if (DECL_ASSEMBLER_NAME_SET_P (decl)
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230 && TREE_SYMBOL_REFERENCED (DECL_ASSEMBLER_NAME (decl)))
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231 return true;
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232
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233 /* If we decided it was needed before, but at the time we didn't have
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234 the definition available, then it's still needed. */
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235 if (node->needed)
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236 return true;
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237
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238 /* Externally visible variables must be output. The exception is
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239 COMDAT variables that must be output only when they are needed. */
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240 if (TREE_PUBLIC (decl) && !flag_whole_program && !DECL_COMDAT (decl)
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241 && !DECL_EXTERNAL (decl))
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242 return true;
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243
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244 /* When emulating tls, we actually see references to the control
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245 variable, rather than the user-level variable. */
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246 if (!targetm.have_tls
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247 && TREE_CODE (decl) == VAR_DECL
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248 && DECL_THREAD_LOCAL_P (decl))
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249 {
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250 tree control = emutls_decl (decl);
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251 if (decide_is_variable_needed (varpool_node (control), control))
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252 return true;
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253 }
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254
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255 /* When not reordering top level variables, we have to assume that
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256 we are going to keep everything. */
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257 if (flag_toplevel_reorder)
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258 return false;
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259
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260 /* We want to emit COMDAT variables only when absolutely necessary. */
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261 if (DECL_COMDAT (decl))
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262 return false;
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263 return true;
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264 }
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265
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266 /* Mark DECL as finalized. By finalizing the declaration, frontend instruct the
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267 middle end to output the variable to asm file, if needed or externally
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268 visible. */
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269 void
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270 varpool_finalize_decl (tree decl)
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271 {
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272 struct varpool_node *node = varpool_node (decl);
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273
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274 /* The first declaration of a variable that comes through this function
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275 decides whether it is global (in C, has external linkage)
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276 or local (in C, has internal linkage). So do nothing more
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277 if this function has already run. */
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278 if (node->finalized)
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279 {
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280 if (cgraph_global_info_ready)
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281 varpool_assemble_pending_decls ();
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282 return;
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283 }
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284 if (node->needed)
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285 varpool_enqueue_needed_node (node);
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286 node->finalized = true;
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287
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288 if (decide_is_variable_needed (node, decl))
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289 varpool_mark_needed_node (node);
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290 /* Since we reclaim unreachable nodes at the end of every language
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291 level unit, we need to be conservative about possible entry points
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292 there. */
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293 else if (TREE_PUBLIC (decl) && !DECL_COMDAT (decl) && !DECL_EXTERNAL (decl))
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294 varpool_mark_needed_node (node);
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295 if (cgraph_global_info_ready)
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296 varpool_assemble_pending_decls ();
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297 }
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298
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299 /* Return variable availability. See cgraph.h for description of individual
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300 return values. */
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301 enum availability
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302 cgraph_variable_initializer_availability (struct varpool_node *node)
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303 {
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304 gcc_assert (cgraph_function_flags_ready);
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305 if (!node->finalized)
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306 return AVAIL_NOT_AVAILABLE;
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307 if (!TREE_PUBLIC (node->decl))
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308 return AVAIL_AVAILABLE;
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309 /* If the variable can be overwritten, return OVERWRITABLE. Takes
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310 care of at least two notable extensions - the COMDAT variables
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311 used to share template instantiations in C++. */
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312 if (!(*targetm.binds_local_p) (node->decl) && !DECL_COMDAT (node->decl))
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313 return AVAIL_OVERWRITABLE;
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314 return AVAIL_AVAILABLE;
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315 }
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316
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317 /* Walk the decls we marked as necessary and see if they reference new
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318 variables or functions and add them into the worklists. */
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319 bool
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320 varpool_analyze_pending_decls (void)
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321 {
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322 bool changed = false;
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323 timevar_push (TV_CGRAPH);
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324
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325 while (varpool_first_unanalyzed_node)
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326 {
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327 tree decl = varpool_first_unanalyzed_node->decl;
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328
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329 varpool_first_unanalyzed_node->analyzed = true;
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330
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331 varpool_first_unanalyzed_node = varpool_first_unanalyzed_node->next_needed;
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332
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333 /* Compute the alignment early so function body expanders are
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334 already informed about increased alignment. */
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335 align_variable (decl, 0);
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336
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337 if (DECL_INITIAL (decl))
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338 record_references_in_initializer (decl);
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339 changed = true;
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340 }
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341 timevar_pop (TV_CGRAPH);
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342 return changed;
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343 }
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344
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345 /* Output one variable, if necessary. Return whether we output it. */
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346 bool
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347 varpool_assemble_decl (struct varpool_node *node)
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348 {
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349 tree decl = node->decl;
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350
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351 if (!TREE_ASM_WRITTEN (decl)
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352 && !node->alias
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353 && !DECL_EXTERNAL (decl)
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354 && (TREE_CODE (decl) != VAR_DECL || !DECL_HAS_VALUE_EXPR_P (decl)))
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355 {
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356 assemble_variable (decl, 0, 1, 0);
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357 if (TREE_ASM_WRITTEN (decl))
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358 {
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359 node->next_needed = varpool_assembled_nodes_queue;
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360 varpool_assembled_nodes_queue = node;
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361 node->finalized = 1;
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362 return true;
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363 }
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364 }
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365
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366 return false;
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367 }
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368
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369 /* Optimization of function bodies might've rendered some variables as
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370 unnecessary so we want to avoid these from being compiled.
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371
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372 This is done by pruning the queue and keeping only the variables that
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373 really appear needed (ie they are either externally visible or referenced
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374 by compiled function). Re-doing the reachability analysis on variables
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375 brings back the remaining variables referenced by these. */
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376 void
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377 varpool_remove_unreferenced_decls (void)
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378 {
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379 struct varpool_node *next, *node = varpool_nodes_queue;
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380
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381 varpool_reset_queue ();
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382
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383 if (errorcount || sorrycount)
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384 return;
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385
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386 while (node)
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387 {
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388 tree decl = node->decl;
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389 next = node->next_needed;
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390 node->needed = 0;
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391
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392 if (node->finalized
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393 && (decide_is_variable_needed (node, decl)
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394 /* ??? Cgraph does not yet rule the world with an iron hand,
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395 and does not control the emission of debug information.
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396 After a variable has its DECL_RTL set, we must assume that
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397 it may be referenced by the debug information, and we can
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398 no longer elide it. */
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399 || DECL_RTL_SET_P (decl)))
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400 varpool_mark_needed_node (node);
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401
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402 node = next;
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403 }
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404 /* Make sure we mark alias targets as used targets. */
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405 finish_aliases_1 ();
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406 varpool_analyze_pending_decls ();
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407 }
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408
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409 /* Output all variables enqueued to be assembled. */
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410 bool
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411 varpool_assemble_pending_decls (void)
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412 {
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413 bool changed = false;
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414
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415 if (errorcount || sorrycount)
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416 return false;
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417
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418 /* EH might mark decls as needed during expansion. This should be safe since
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419 we don't create references to new function, but it should not be used
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420 elsewhere. */
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421 varpool_analyze_pending_decls ();
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422
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423 while (varpool_nodes_queue)
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424 {
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425 struct varpool_node *node = varpool_nodes_queue;
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426
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427 varpool_nodes_queue = varpool_nodes_queue->next_needed;
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428 if (varpool_assemble_decl (node))
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429 changed = true;
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430 else
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431 node->next_needed = NULL;
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432 }
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433 /* varpool_nodes_queue is now empty, clear the pointer to the last element
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434 in the queue. */
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435 varpool_last_needed_node = NULL;
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436 return changed;
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|
437 }
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438
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|
439 /* Remove all elements from the queue so we can re-use it for debug output. */
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440 void
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441 varpool_empty_needed_queue (void)
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442 {
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443 /* EH might mark decls as needed during expansion. This should be safe since
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|
444 we don't create references to new function, but it should not be used
|
|
|
445 elsewhere. */
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|
446 varpool_analyze_pending_decls ();
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447
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|
448 while (varpool_nodes_queue)
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|
449 {
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|
450 struct varpool_node *node = varpool_nodes_queue;
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451 varpool_nodes_queue = varpool_nodes_queue->next_needed;
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|
452 node->next_needed = NULL;
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|
453 }
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|
|
454 /* varpool_nodes_queue is now empty, clear the pointer to the last element
|
|
|
455 in the queue. */
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|
|
456 varpool_last_needed_node = NULL;
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|
457 }
|
|
|
458
|
|
|
459 /* Create a new global variable of type TYPE. */
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|
|
460 tree
|
|
|
461 add_new_static_var (tree type)
|
|
|
462 {
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|
|
463 tree new_decl;
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|
|
464 struct varpool_node *new_node;
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465
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|
466 new_decl = create_tmp_var (type, NULL);
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|
467 DECL_NAME (new_decl) = create_tmp_var_name (NULL);
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|
|
468 TREE_READONLY (new_decl) = 0;
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|
|
469 TREE_STATIC (new_decl) = 1;
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|
|
470 TREE_USED (new_decl) = 1;
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|
|
471 DECL_CONTEXT (new_decl) = NULL_TREE;
|
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|
472 DECL_ABSTRACT (new_decl) = 0;
|
|
|
473 lang_hooks.dup_lang_specific_decl (new_decl);
|
|
|
474 create_var_ann (new_decl);
|
|
|
475 new_node = varpool_node (new_decl);
|
|
|
476 varpool_mark_needed_node (new_node);
|
|
|
477 add_referenced_var (new_decl);
|
|
|
478 varpool_finalize_decl (new_decl);
|
|
|
479
|
|
|
480 return new_node->decl;
|
|
|
481 }
|
|
|
482
|
|
|
483 #include "gt-varpool.h"
|
