gold/common.cc

   1 // common.cc -- handle common symbols for gold
   2
   3 // Copyright 2006, 2007 Free Software Foundation, Inc.
   4 // Written by Ian Lance Taylor <iant@google.com>.
   5
   6 // This file is part of gold.
   7
   8 // This program is free software; you can redistribute it and/or modify
   9 // it under the terms of the GNU General Public License as published by
  10 // the Free Software Foundation; either version 3 of the License, or
  11 // (at your option) any later version.
  12
  13 // This program is distributed in the hope that it will be useful,
  14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 // GNU General Public License for more details.
  17
  18 // You should have received a copy of the GNU General Public License
  19 // along with this program; if not, write to the Free Software
  20 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
  21 // MA 02110-1301, USA.
  22
  23 #include "gold.h"
  24
  25 #include <algorithm>
  26
  27 #include "workqueue.h"
  28 #include "layout.h"
  29 #include "output.h"
  30 #include "symtab.h"
  31 #include "common.h"
  32
  33 namespace gold
  34 {
  35
  36 // Allocate_commons_task methods.
  37
  38 // This task allocates the common symbols.  We need a lock on the
  39 // symbol table.
  40
  41 Task_token*
  42 Allocate_commons_task::is_runnable()
  43 {
  44   if (!this->symtab_lock_->is_writable())
  45     return this->symtab_lock_;
  46   return NULL;
  47 }
  48
  49 // Return the locks we hold: one on the symbol table, and one blocker.
  50
  51 void
  52 Allocate_commons_task::locks(Task_locker* tl)
  53 {
  54   tl->add(this, this->blocker_);
  55   tl->add(this, this->symtab_lock_);
  56 }
  57
  58 // Allocate the common symbols.
  59
  60 void
  61 Allocate_commons_task::run(Workqueue*)
  62 {
  63   this->symtab_->allocate_commons(this->options_, this->layout_);
  64 }
  65
  66 // This class is used to sort the common symbol by size.  We put the
  67 // larger common symbols first.
  68
  69 template<int size>
  70 class Sort_commons
  71 {
  72  public:
  73   Sort_commons(const Symbol_table* symtab)
  74     : symtab_(symtab)
  75   { }
  76
  77   bool operator()(const Symbol* a, const Symbol* b) const;
  78
  79  private:
  80   const Symbol_table* symtab_;
  81 };
  82
  83 template<int size>
  84 bool
  85 Sort_commons<size>::operator()(const Symbol* pa, const Symbol* pb) const
  86 {
  87   if (pa == NULL)
  88     return false;
  89   if (pb == NULL)
  90     return true;
  91
  92   const Symbol_table* symtab = this->symtab_;
  93   const Sized_symbol<size>* psa;
  94   psa = symtab->get_sized_symbol SELECT_SIZE_NAME(size) (pa
  95                                                          SELECT_SIZE(size));
  96   const Sized_symbol<size>* psb;
  97   psb = symtab->get_sized_symbol SELECT_SIZE_NAME(size) (pb
  98                                                          SELECT_SIZE(size));
  99
 100   typename Sized_symbol<size>::Size_type sa = psa->symsize();
 101   typename Sized_symbol<size>::Size_type sb = psb->symsize();
 102   if (sa < sb)
 103     return false;
 104   else if (sb > sa)
 105     return true;
 106
 107   // When the symbols are the same size, we sort them by alignment.
 108   typename Sized_symbol<size>::Value_type va = psa->value();
 109   typename Sized_symbol<size>::Value_type vb = psb->value();
 110   if (va < vb)
 111     return false;
 112   else if (vb > va)
 113     return true;
 114
 115   // Otherwise we stabilize the sort by sorting by name.
 116   return strcmp(psa->name(), psb->name()) < 0;
 117 }
 118
 119 // Allocate the common symbols.
 120
 121 void
 122 Symbol_table::allocate_commons(const General_options& options, Layout* layout)
 123 {
 124   if (parameters->get_size() == 32)
 125     {
 126 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
 127       this->do_allocate_commons<32>(options, layout);
 128 #else
 129       gold_unreachable();
 130 #endif
 131     }
 132   else if (parameters->get_size() == 64)
 133     {
 134 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
 135       this->do_allocate_commons<64>(options, layout);
 136 #else
 137       gold_unreachable();
 138 #endif
 139     }
 140   else
 141     gold_unreachable();
 142 }
 143
 144 // Allocated the common symbols, sized version.
 145
 146 template<int size>
 147 void
 148 Symbol_table::do_allocate_commons(const General_options&,
 149                                   Layout* layout)
 150 {
 151   typedef typename Sized_symbol<size>::Value_type Value_type;
 152   typedef typename Sized_symbol<size>::Size_type Size_type;
 153
 154   // We've kept a list of all the common symbols.  But the symbol may
 155   // have been resolved to a defined symbol by now.  And it may be a
 156   // forwarder.  First remove all non-common symbols.
 157   bool any = false;
 158   uint64_t addralign = 0;
 159   for (Commons_type::iterator p = this->commons_.begin();
 160        p != this->commons_.end();
 161        ++p)
 162     {
 163       Symbol* sym = *p;
 164       if (sym->is_forwarder())
 165         {
 166           sym = this->resolve_forwards(sym);
 167           *p = sym;
 168         }
 169       if (!sym->is_common())
 170         *p = NULL;
 171       else
 172         {
 173           any = true;
 174           Sized_symbol<size>* ssym;
 175           ssym = this->get_sized_symbol SELECT_SIZE_NAME(size) (
 176               sym
 177               SELECT_SIZE(size));
 178           if (ssym->value() > addralign)
 179             addralign = ssym->value();
 180         }
 181     }
 182   if (!any)
 183     return;
 184
 185   // Sort the common symbols by size, so that they pack better into
 186   // memory.
 187   std::sort(this->commons_.begin(), this->commons_.end(),
 188             Sort_commons<size>(this));
 189
 190   // Place them in a newly allocated .bss section.
 191
 192   Output_data_space *poc = new Output_data_space(addralign);
 193
 194   layout->add_output_section_data(".bss", elfcpp::SHT_NOBITS,
 195                                   elfcpp::SHF_WRITE | elfcpp::SHF_ALLOC,
 196                                   poc);
 197
 198   // Allocate them all.
 199
 200   off_t off = 0;
 201   for (Commons_type::iterator p = this->commons_.begin();
 202        p != this->commons_.end();
 203        ++p)
 204     {
 205       Symbol* sym = *p;
 206       if (sym == NULL)
 207         break;
 208
 209       Sized_symbol<size>* ssym;
 210       ssym = this->get_sized_symbol SELECT_SIZE_NAME(size) (sym
 211                                                             SELECT_SIZE(size));
 212
 213       off = align_address(off, ssym->value());
 214
 215       ssym->allocate_common(poc, off);
 216
 217       off += ssym->symsize();
 218     }
 219
 220   poc->set_current_data_size(off);
 221
 222   this->commons_.clear();
 223 }
 224
 225 } // End namespace gold.