gold/common.cc

   1 // common.cc -- handle common symbols for gold
   2
   3 // Copyright 2006, 2007, 2008 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 = symtab->get_sized_symbol<size>(pa);
  94   const Sized_symbol<size>* psb = symtab->get_sized_symbol<size>(pb);
  95
  96   typename Sized_symbol<size>::Size_type sa = psa->symsize();
  97   typename Sized_symbol<size>::Size_type sb = psb->symsize();
  98   if (sa < sb)
  99     return false;
 100   else if (sb > sa)
 101     return true;
 102
 103   // When the symbols are the same size, we sort them by alignment.
 104   typename Sized_symbol<size>::Value_type va = psa->value();
 105   typename Sized_symbol<size>::Value_type vb = psb->value();
 106   if (va < vb)
 107     return false;
 108   else if (vb > va)
 109     return true;
 110
 111   // Otherwise we stabilize the sort by sorting by name.
 112   return strcmp(psa->name(), psb->name()) < 0;
 113 }
 114
 115 // Allocate the common symbols.
 116
 117 void
 118 Symbol_table::allocate_commons(const General_options& options, Layout* layout)
 119 {
 120   if (parameters->target().get_size() == 32)
 121     {
 122 #if defined(HAVE_TARGET_32_LITTLE) || defined(HAVE_TARGET_32_BIG)
 123       this->do_allocate_commons<32>(options, layout);
 124 #else
 125       gold_unreachable();
 126 #endif
 127     }
 128   else if (parameters->target().get_size() == 64)
 129     {
 130 #if defined(HAVE_TARGET_64_LITTLE) || defined(HAVE_TARGET_64_BIG)
 131       this->do_allocate_commons<64>(options, layout);
 132 #else
 133       gold_unreachable();
 134 #endif
 135     }
 136   else
 137     gold_unreachable();
 138 }
 139
 140 // Allocated the common symbols, sized version.
 141
 142 template<int size>
 143 void
 144 Symbol_table::do_allocate_commons(const General_options&,
 145                                   Layout* layout)
 146 {
 147   typedef typename Sized_symbol<size>::Value_type Value_type;
 148   typedef typename Sized_symbol<size>::Size_type Size_type;
 149
 150   // We've kept a list of all the common symbols.  But the symbol may
 151   // have been resolved to a defined symbol by now.  And it may be a
 152   // forwarder.  First remove all non-common symbols.
 153   bool any = false;
 154   uint64_t addralign = 0;
 155   for (Commons_type::iterator p = this->commons_.begin();
 156        p != this->commons_.end();
 157        ++p)
 158     {
 159       Symbol* sym = *p;
 160       if (sym->is_forwarder())
 161         {
 162           sym = this->resolve_forwards(sym);
 163           *p = sym;
 164         }
 165       if (!sym->is_common())
 166         *p = NULL;
 167       else
 168         {
 169           any = true;
 170           Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym);
 171           if (ssym->value() > addralign)
 172             addralign = ssym->value();
 173         }
 174     }
 175   if (!any)
 176     return;
 177
 178   // Sort the common symbols by size, so that they pack better into
 179   // memory.
 180   std::sort(this->commons_.begin(), this->commons_.end(),
 181             Sort_commons<size>(this));
 182
 183   // Place them in a newly allocated .bss section.
 184
 185   Output_data_space *poc = new Output_data_space(addralign);
 186
 187   layout->add_output_section_data(".bss", elfcpp::SHT_NOBITS,
 188                                   elfcpp::SHF_WRITE | elfcpp::SHF_ALLOC,
 189                                   poc);
 190
 191   // Allocate them all.
 192
 193   off_t off = 0;
 194   for (Commons_type::iterator p = this->commons_.begin();
 195        p != this->commons_.end();
 196        ++p)
 197     {
 198       Symbol* sym = *p;
 199       if (sym == NULL)
 200         break;
 201       Sized_symbol<size>* ssym = this->get_sized_symbol<size>(sym);
 202       off = align_address(off, ssym->value());
 203       ssym->allocate_common(poc, off);
 204       off += ssym->symsize();
 205     }
 206
 207   poc->set_current_data_size(off);
 208
 209   this->commons_.clear();
 210 }
 211
 212 } // End namespace gold.