C++ DECL_COMDAT函数代码示例

void
symtab_node::fixup_same_cpp_alias_visibility (symtab_node *target)
{
  if (is_a <cgraph_node *> (this))
    {
      DECL_DECLARED_INLINE_P (decl)
	 = DECL_DECLARED_INLINE_P (target->decl);
      DECL_DISREGARD_INLINE_LIMITS (decl)
	 = DECL_DISREGARD_INLINE_LIMITS (target->decl);
    }
  /* FIXME: It is not really clear why those flags should not be copied for
     functions, too.  */
  else
    {
      DECL_WEAK (decl) = DECL_WEAK (target->decl);
      DECL_EXTERNAL (decl) = DECL_EXTERNAL (target->decl);
      DECL_VISIBILITY (decl) = DECL_VISIBILITY (target->decl);
    }
  DECL_VIRTUAL_P (decl) = DECL_VIRTUAL_P (target->decl);
  if (TREE_PUBLIC (decl))
    {
      tree group;

      DECL_EXTERNAL (decl) = DECL_EXTERNAL (target->decl);
      DECL_COMDAT (decl) = DECL_COMDAT (target->decl);
      group = target->get_comdat_group ();
      set_comdat_group (group);
      if (group && !same_comdat_group)
	add_to_same_comdat_group (target);
    }
  externally_visible = target->externally_visible;
}

void
fixup_same_cpp_alias_visibility (symtab_node node, symtab_node target)
{
  if (is_a <cgraph_node> (node))
    {
      DECL_DECLARED_INLINE_P (node->symbol.decl)
	 = DECL_DECLARED_INLINE_P (target->symbol.decl);
      DECL_DISREGARD_INLINE_LIMITS (node->symbol.decl)
	 = DECL_DISREGARD_INLINE_LIMITS (target->symbol.decl);
    }
  /* FIXME: It is not really clear why those flags should not be copied for
     functions, too.  */
  else
    {
      DECL_WEAK (node->symbol.decl) = DECL_WEAK (target->symbol.decl);
      DECL_EXTERNAL (node->symbol.decl) = DECL_EXTERNAL (target->symbol.decl);
      DECL_VISIBILITY (node->symbol.decl) = DECL_VISIBILITY (target->symbol.decl);
    }
  DECL_VIRTUAL_P (node->symbol.decl) = DECL_VIRTUAL_P (target->symbol.decl);
  if (TREE_PUBLIC (node->symbol.decl))
    {
      DECL_EXTERNAL (node->symbol.decl) = DECL_EXTERNAL (target->symbol.decl);
      DECL_COMDAT (node->symbol.decl) = DECL_COMDAT (target->symbol.decl);
      DECL_COMDAT_GROUP (node->symbol.decl)
	 = DECL_COMDAT_GROUP (target->symbol.decl);
      if (DECL_ONE_ONLY (target->symbol.decl)
	  && !node->symbol.same_comdat_group)
	symtab_add_to_same_comdat_group ((symtab_node)node, (symtab_node)target);
    }
  node->symbol.externally_visible = target->symbol.externally_visible;
}

static unsigned int
function_and_variable_visibility (void)
{
  struct cgraph_node *node;
  struct varpool_node *vnode;

  for (node = cgraph_nodes; node; node = node->next)
    {
      if (node->reachable
	  && (DECL_COMDAT (node->decl)
	      || (!flag_whole_program
		  && TREE_PUBLIC (node->decl) && !DECL_EXTERNAL (node->decl))))
	node->local.externally_visible = true;
      if (!node->local.externally_visible && node->analyzed
	  && !DECL_EXTERNAL (node->decl))
	{
	  gcc_assert (flag_whole_program || !TREE_PUBLIC (node->decl));
	  TREE_PUBLIC (node->decl) = 0;
	}
      node->local.local = (!node->needed
			   && node->analyzed
			   && !DECL_EXTERNAL (node->decl)
			   && !node->local.externally_visible);
    }
  for (vnode = varpool_nodes_queue; vnode; vnode = vnode->next_needed)
    {
      if (vnode->needed
	  && !flag_whole_program
	  && (DECL_COMDAT (vnode->decl) || TREE_PUBLIC (vnode->decl)))
	vnode->externally_visible = 1;
      if (!vnode->externally_visible)
	{
	  gcc_assert (flag_whole_program || !TREE_PUBLIC (vnode->decl));
	  TREE_PUBLIC (vnode->decl) = 0;
	}
      /* Static variables defined in auxiliary modules are externalized to
         allow cross module inlining.  */
      gcc_assert (TREE_STATIC (vnode->decl)
                  || varpool_is_auxiliary (vnode));
    }

  if (dump_file)
    {
      fprintf (dump_file, "\nMarking local functions:");
      for (node = cgraph_nodes; node; node = node->next)
	if (node->local.local)
	  fprintf (dump_file, " %s", cgraph_node_name (node));
      fprintf (dump_file, "\n\n");
      fprintf (dump_file, "\nMarking externally visible functions:");
      for (node = cgraph_nodes; node; node = node->next)
	if (node->local.externally_visible)
	  fprintf (dump_file, " %s", cgraph_node_name (node));
      fprintf (dump_file, "\n\n");
    }
  cgraph_function_flags_ready = true;
  return 0;
}

/* Make DECL local.  FIXME: We shouldn't need to mess with rtl this early,
   but other code such as notice_global_symbol generates rtl.  */
void
symtab_make_decl_local (tree decl)
{
  rtx rtl, symbol;

  if (TREE_CODE (decl) == VAR_DECL)
    DECL_COMMON (decl) = 0;
  else gcc_assert (TREE_CODE (decl) == FUNCTION_DECL);

  if (DECL_ONE_ONLY (decl) || DECL_COMDAT (decl))
    {
      /* It is possible that we are linking against library defining same COMDAT
	 function.  To avoid conflict we need to rename our local name of the
	 function just in the case WHOPR partitioning decide to make it hidden
	 to avoid cross partition references.  */
      if (flag_wpa)
	{
	  const char *old_name;
          symtab_node node = symtab_get_node (decl);
	  old_name  = IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (decl));
	  change_decl_assembler_name (decl,
				      clone_function_name (decl, "local"));
	  if (node->symbol.lto_file_data)
	    lto_record_renamed_decl (node->symbol.lto_file_data,
				     old_name,
				     IDENTIFIER_POINTER
				       (DECL_ASSEMBLER_NAME (decl)));
	}
      DECL_SECTION_NAME (decl) = 0;
      DECL_COMDAT (decl) = 0;
    }
  DECL_COMDAT_GROUP (decl) = 0;
  DECL_WEAK (decl) = 0;
  DECL_EXTERNAL (decl) = 0;
  TREE_PUBLIC (decl) = 0;
  if (!DECL_RTL_SET_P (decl))
    return;

  /* Update rtl flags.  */
  make_decl_rtl (decl);

  rtl = DECL_RTL (decl);
  if (!MEM_P (rtl))
    return;

  symbol = XEXP (rtl, 0);
  if (GET_CODE (symbol) != SYMBOL_REF)
    return;

  SYMBOL_REF_WEAK (symbol) = DECL_WEAK (decl);
}

static void
pack_ts_decl_with_vis_value_fields (struct bitpack_d *bp, tree expr)
{
  bp_pack_value (bp, DECL_COMMON (expr), 1);
  bp_pack_value (bp, DECL_DLLIMPORT_P (expr), 1);
  bp_pack_value (bp, DECL_WEAK (expr), 1);
  bp_pack_value (bp, DECL_SEEN_IN_BIND_EXPR_P (expr),  1);
  bp_pack_value (bp, DECL_COMDAT (expr),  1);
  bp_pack_value (bp, DECL_VISIBILITY (expr),  2);
  bp_pack_value (bp, DECL_VISIBILITY_SPECIFIED (expr),  1);

  if (TREE_CODE (expr) == VAR_DECL)
    {
      bp_pack_value (bp, DECL_HARD_REGISTER (expr), 1);
      /* DECL_IN_TEXT_SECTION is set during final asm output only. */
      bp_pack_value (bp, DECL_IN_CONSTANT_POOL (expr), 1);
    }

  if (TREE_CODE (expr) == FUNCTION_DECL)
    {
      bp_pack_value (bp, DECL_FINAL_P (expr), 1);
      bp_pack_value (bp, DECL_CXX_CONSTRUCTOR_P (expr), 1);
      bp_pack_value (bp, DECL_CXX_DESTRUCTOR_P (expr), 1);
    }
}

static void
unpack_ts_decl_with_vis_value_fields (struct bitpack_d *bp, tree expr)
{
  DECL_DEFER_OUTPUT (expr) = (unsigned) bp_unpack_value (bp, 1);
  DECL_COMMON (expr) = (unsigned) bp_unpack_value (bp, 1);
  DECL_DLLIMPORT_P (expr) = (unsigned) bp_unpack_value (bp, 1);
  DECL_WEAK (expr) = (unsigned) bp_unpack_value (bp, 1);
  DECL_SEEN_IN_BIND_EXPR_P (expr) = (unsigned) bp_unpack_value (bp,  1);
  DECL_COMDAT (expr) = (unsigned) bp_unpack_value (bp,  1);
  DECL_VISIBILITY (expr) = (enum symbol_visibility) bp_unpack_value (bp,  2);
  DECL_VISIBILITY_SPECIFIED (expr) = (unsigned) bp_unpack_value (bp,  1);

  if (TREE_CODE (expr) == VAR_DECL)
    {
      DECL_HARD_REGISTER (expr) = (unsigned) bp_unpack_value (bp, 1);
      DECL_IN_TEXT_SECTION (expr) = (unsigned) bp_unpack_value (bp, 1);
      DECL_IN_CONSTANT_POOL (expr) = (unsigned) bp_unpack_value (bp, 1);
      DECL_TLS_MODEL (expr) = (enum tls_model) bp_unpack_value (bp,  3);
    }

  if (VAR_OR_FUNCTION_DECL_P (expr))
    {
      priority_type p;
      p = (priority_type) bp_unpack_var_len_unsigned (bp);
      SET_DECL_INIT_PRIORITY (expr, p);
    }
}

void
symtab_node::make_decl_local (void)
{
  rtx rtl, symbol;

  /* Avoid clearing comdat_groups on comdat-local decls.  */
  if (TREE_PUBLIC (decl) == 0)
    return;

  if (TREE_CODE (decl) == VAR_DECL)
    DECL_COMMON (decl) = 0;
  else gcc_assert (TREE_CODE (decl) == FUNCTION_DECL);

  DECL_COMDAT (decl) = 0;
  DECL_WEAK (decl) = 0;
  DECL_EXTERNAL (decl) = 0;
  DECL_VISIBILITY_SPECIFIED (decl) = 0;
  DECL_VISIBILITY (decl) = VISIBILITY_DEFAULT;
  TREE_PUBLIC (decl) = 0;
  if (!DECL_RTL_SET_P (decl))
    return;

  /* Update rtl flags.  */
  make_decl_rtl (decl);

  rtl = DECL_RTL (decl);
  if (!MEM_P (rtl))
    return;

  symbol = XEXP (rtl, 0);
  if (GET_CODE (symbol) != SYMBOL_REF)
    return;

  SYMBOL_REF_WEAK (symbol) = DECL_WEAK (decl);
}

/* Determine if variable DECL is needed.  That is, visible to something
   either outside this translation unit, something magic in the system
   configury */
bool
decide_is_variable_needed (struct varpool_node *node, tree decl)
{
  /* If the user told us it is used, then it must be so.  */
  if ((node->externally_visible && !DECL_COMDAT (decl))
      || node->force_output)
    return true;

  /* ??? If the assembler name is set by hand, it is possible to assemble
     the name later after finalizing the function and the fact is noticed
     in assemble_name then.  This is arguably a bug.  */
  if (DECL_ASSEMBLER_NAME_SET_P (decl)
      && TREE_SYMBOL_REFERENCED (DECL_ASSEMBLER_NAME (decl)))
    return true;

  /* Externally visible variables must be output.  The exception is
     COMDAT variables that must be output only when they are needed.  */
  if (TREE_PUBLIC (decl)
      && !flag_whole_program
      && !flag_lto
      && !flag_whopr
      && !DECL_COMDAT (decl)
      && !DECL_EXTERNAL (decl))
    return true;

  /* When emulating tls, we actually see references to the control
     variable, rather than the user-level variable.  */
  if (!targetm.have_tls
      && TREE_CODE (decl) == VAR_DECL
      && DECL_THREAD_LOCAL_P (decl))
    {
      tree control = emutls_decl (decl);
      if (decide_is_variable_needed (varpool_node (control), control))
	return true;
    }

  /* When not reordering top level variables, we have to assume that
     we are going to keep everything.  */
  if (flag_toplevel_reorder)
    return false;

  /* We want to emit COMDAT variables only when absolutely necessary.  */
  if (DECL_COMDAT (decl))
    return false;
  return true;
}

static bool
decide_is_function_needed (struct cgraph_node *node, tree decl)
{
  if (MAIN_NAME_P (DECL_NAME (decl))
      && TREE_PUBLIC (decl))
    {
      node->local.externally_visible = true;
      return true;
    }

  /* If the user told us it is used, then it must be so.  */
  if (node->local.externally_visible)
    return true;

  /* ??? If the assembler name is set by hand, it is possible to assemble
     the name later after finalizing the function and the fact is noticed
     in assemble_name then.  This is arguably a bug.  */
  if (DECL_ASSEMBLER_NAME_SET_P (decl)
      && TREE_SYMBOL_REFERENCED (DECL_ASSEMBLER_NAME (decl)))
    return true;

  /* With -fkeep-inline-functions we are keeping all inline functions except
     for extern inline ones.  */
  if (flag_keep_inline_functions
      && DECL_DECLARED_INLINE_P (decl)
      && !DECL_EXTERNAL (decl)
      && !lookup_attribute ("always_inline", DECL_ATTRIBUTES (decl)))
     return true;

  /* If we decided it was needed before, but at the time we didn't have
     the body of the function available, then it's still needed.  We have
     to go back and re-check its dependencies now.  */
  if (node->needed)
    return true;

  /* Externally visible functions must be output.  The exception is
     COMDAT functions that must be output only when they are needed.

     When not optimizing, also output the static functions. (see
     PR24561), but don't do so for always_inline functions, functions
     declared inline and nested functions.  These was optimized out
     in the original implementation and it is unclear whether we want
     to change the behavior here.  */
  if (((TREE_PUBLIC (decl)
	|| (!optimize && !node->local.disregard_inline_limits
	    && !DECL_DECLARED_INLINE_P (decl)
	    && !node->origin))
      && !flag_whole_program)
      && !DECL_COMDAT (decl) && !DECL_EXTERNAL (decl))
    return true;

  /* Constructors and destructors are reachable from the runtime by
     some mechanism.  */
  if (DECL_STATIC_CONSTRUCTOR (decl) || DECL_STATIC_DESTRUCTOR (decl))
    return true;

  return false;
}

void
symtab_make_decl_local (tree decl)
{
  rtx rtl, symbol;

  /* Avoid clearing DECL_COMDAT_GROUP on comdat-local decls.  */
  if (TREE_PUBLIC (decl) == 0)
    return;

  if (TREE_CODE (decl) == VAR_DECL)
    DECL_COMMON (decl) = 0;
  else gcc_assert (TREE_CODE (decl) == FUNCTION_DECL);

  if (DECL_ONE_ONLY (decl) || DECL_COMDAT (decl))
    {
      DECL_SECTION_NAME (decl) = 0;
      DECL_COMDAT (decl) = 0;
    }
  DECL_COMDAT_GROUP (decl) = 0;
  DECL_WEAK (decl) = 0;
  DECL_EXTERNAL (decl) = 0;
  DECL_VISIBILITY_SPECIFIED (decl) = 0;
  DECL_VISIBILITY (decl) = VISIBILITY_DEFAULT;
  TREE_PUBLIC (decl) = 0;
  DECL_DLLIMPORT_P (decl) = 0;
  if (!DECL_RTL_SET_P (decl))
    return;

  /* Update rtl flags.  */
  make_decl_rtl (decl);

  rtl = DECL_RTL (decl);
  if (!MEM_P (rtl))
    return;

  symbol = XEXP (rtl, 0);
  if (GET_CODE (symbol) != SYMBOL_REF)
    return;

  SYMBOL_REF_WEAK (symbol) = DECL_WEAK (decl);
}

symtab_node *
symtab_nonoverwritable_alias (symtab_node *node)
{
  tree new_decl;
  symtab_node *new_node = NULL;

  /* First try to look up existing alias or base object
     (if that is already non-overwritable).  */
  node = symtab_alias_ultimate_target (node, NULL);
  gcc_assert (!node->alias && !node->weakref);
  symtab_for_node_and_aliases (node, symtab_nonoverwritable_alias_1,
		               (void *)&new_node, true);
  if (new_node)
    return new_node;
#ifndef ASM_OUTPUT_DEF
  /* If aliases aren't supported by the assembler, fail.  */
  return NULL;
#endif

  /* Otherwise create a new one.  */
  new_decl = copy_node (node->decl);
  DECL_DLLIMPORT_P (new_decl) = 0;
  DECL_NAME (new_decl) = clone_function_name (node->decl, "localalias");
  if (TREE_CODE (new_decl) == FUNCTION_DECL)
    DECL_STRUCT_FUNCTION (new_decl) = NULL;
  DECL_INITIAL (new_decl) = NULL;
  SET_DECL_ASSEMBLER_NAME (new_decl, DECL_NAME (new_decl));
  SET_DECL_RTL (new_decl, NULL);

  /* Update the properties.  */
  DECL_EXTERNAL (new_decl) = 0;
  if (DECL_ONE_ONLY (node->decl))
    DECL_SECTION_NAME (new_decl) = NULL;
  DECL_COMDAT_GROUP (new_decl) = 0;
  TREE_PUBLIC (new_decl) = 0;
  DECL_COMDAT (new_decl) = 0;
  DECL_WEAK (new_decl) = 0;
  DECL_VIRTUAL_P (new_decl) = 0;
  if (TREE_CODE (new_decl) == FUNCTION_DECL)
    {
      DECL_STATIC_CONSTRUCTOR (new_decl) = 0;
      DECL_STATIC_DESTRUCTOR (new_decl) = 0;
      new_node = cgraph_create_function_alias
				 (new_decl, node->decl);
    }
  else
    new_node = varpool_create_variable_alias (new_decl,
							    node->decl);
  symtab_resolve_alias (new_node, node);  
  gcc_assert (decl_binds_to_current_def_p (new_decl));
  return new_node;
}

static bool
lto_symtab_resolve_replaceable_p (symtab_node e)
{
  if (DECL_EXTERNAL (e->symbol.decl)
      || DECL_COMDAT (e->symbol.decl)
      || DECL_ONE_ONLY (e->symbol.decl)
      || DECL_WEAK (e->symbol.decl))
    return true;

  if (TREE_CODE (e->symbol.decl) == VAR_DECL)
    return (DECL_COMMON (e->symbol.decl)
	    || (!flag_no_common && !DECL_INITIAL (e->symbol.decl)));

  return false;
}

/* Return variable availability.  See cgraph.h for description of individual
   return values.  */
enum availability
cgraph_variable_initializer_availability (struct varpool_node *node)
{
  gcc_assert (cgraph_function_flags_ready);
  if (!node->finalized)
    return AVAIL_NOT_AVAILABLE;
  if (!TREE_PUBLIC (node->decl))
    return AVAIL_AVAILABLE;
  /* If the variable can be overwritten, return OVERWRITABLE.  Takes
     care of at least two notable extensions - the COMDAT variables
     used to share template instantiations in C++.  */
  if (!(*targetm.binds_local_p) (node->decl) && !DECL_COMDAT (node->decl))
    return AVAIL_OVERWRITABLE;
  return AVAIL_AVAILABLE;
}

enum symbol_class
get_symbol_class (symtab_node *node)
{
  /* Inline clones are always duplicated.
     This include external delcarations.   */
  cgraph_node *cnode = dyn_cast <cgraph_node> (node);

  if (DECL_ABSTRACT (node->decl))
    return SYMBOL_EXTERNAL;

  if (cnode && cnode->global.inlined_to)
    return SYMBOL_DUPLICATE;

  /* Weakref aliases are always duplicated.  */
  if (node->weakref)
    return SYMBOL_DUPLICATE;

  /* External declarations are external.  */
  if (DECL_EXTERNAL (node->decl))
    return SYMBOL_EXTERNAL;

  if (varpool_node *vnode = dyn_cast <varpool_node> (node))
    {
      /* Constant pool references use local symbol names that can not
         be promoted global.  We should never put into a constant pool
         objects that can not be duplicated across partitions.  */
      if (DECL_IN_CONSTANT_POOL (node->decl))
	return SYMBOL_DUPLICATE;
      gcc_checking_assert (vnode->definition);
    }
  /* Functions that are cloned may stay in callgraph even if they are unused.
     Handle them as external; compute_ltrans_boundary take care to make
     proper things to happen (i.e. to make them appear in the boundary but
     with body streamed, so clone can me materialized).  */
  else if (!cgraph (node)->definition)
    return SYMBOL_EXTERNAL;

  /* Comdats are duplicated to every use unless they are keyed.
     Those do not need duplication.  */
  if (DECL_COMDAT (node->decl)
      && !node->force_output
      && !symtab_used_from_object_file_p (node))
    return SYMBOL_DUPLICATE;

  return SYMBOL_PARTITION;
}

/* Mark DECL as finalized.  By finalizing the declaration, frontend instruct the
   middle end to output the variable to asm file, if needed or externally
   visible.  */
void
varpool_finalize_decl (tree decl)
{
  struct varpool_node *node = varpool_node (decl);

  /* FIXME: We don't really stream varpool datastructure and instead rebuild it
     by varpool_finalize_decl.  This is not quite correct since this way we can't
     attach any info to varpool.  Eventually we will want to stream varpool nodes
     and the flags.

     For the moment just prevent analysis of varpool nodes to happen again, so
     we will re-try to compute "address_taken" flag of varpool that breaks
     in presence of clones.  */
  if (in_lto_p)
    node->analyzed = true;

  /* The first declaration of a variable that comes through this function
     decides whether it is global (in C, has external linkage)
     or local (in C, has internal linkage).  So do nothing more
     if this function has already run.  */
  if (node->finalized)
    {
      if (cgraph_global_info_ready)
	varpool_assemble_pending_decls ();
      return;
    }
  if (node->needed)
    varpool_enqueue_needed_node (node);
  node->finalized = true;

  if (decide_is_variable_needed (node, decl))
    varpool_mark_needed_node (node);
  /* Since we reclaim unreachable nodes at the end of every language
     level unit, we need to be conservative about possible entry points
     there.  */
  else if (TREE_PUBLIC (decl) && !DECL_COMDAT (decl) && !DECL_EXTERNAL (decl))
    varpool_mark_needed_node (node);
  if (cgraph_global_info_ready)
    varpool_assemble_pending_decls ();
}