gcc:

[pf3gnuchains/gcc-fork.git] / gcc / config / darwin.c

/* Functions for generic Darwin as target machine for GNU C compiler.
   Copyright (C) 1989, 1990, 1991, 1992, 1993, 2000, 2001, 2002, 2003, 2004,
   2005, 2006, 2007, 2008, 2009, 2010
   Free Software Foundation, Inc.
   Contributed by Apple Computer Inc.

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3, or (at your option)
any later version.

GCC is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "rtl.h"
#include "regs.h"
#include "hard-reg-set.h"
#include "insn-config.h"
#include "conditions.h"
#include "insn-flags.h"
#include "output.h"
#include "insn-attr.h"
#include "flags.h"
#include "tree.h"
#include "expr.h"
#include "reload.h"
#include "function.h"
#include "ggc.h"
#include "langhooks.h"
#include "target.h"
#include "tm_p.h"
#include "diagnostic-core.h"
#include "toplev.h"
#include "hashtab.h"
#include "df.h"
#include "debug.h"
#include "obstack.h"
#include "lto-streamer.h"

/* Darwin supports a feature called fix-and-continue, which is used
   for rapid turn around debugging.  When code is compiled with the
   -mfix-and-continue flag, two changes are made to the generated code
   that allow the system to do things that it would normally not be
   able to do easily.  These changes allow gdb to load in
   recompilation of a translation unit that has been changed into a
   running program and replace existing functions and methods of that
   translation unit with versions of those functions and methods
   from the newly compiled translation unit.  The new functions access
   the existing static symbols from the old translation unit, if the
   symbol existed in the unit to be replaced, and from the new
   translation unit, otherwise.

   The changes are to insert 5 nops at the beginning of all functions
   and to use indirection to get at static symbols.  The 5 nops
   are required by consumers of the generated code.  Currently, gdb
   uses this to patch in a jump to the overriding function, this
   allows all uses of the old name to forward to the replacement,
   including existing function pointers and virtual methods.  See
   rs6000_emit_prologue for the code that handles the nop insertions.

   The added indirection allows gdb to redirect accesses to static
   symbols from the newly loaded translation unit to the existing
   symbol, if any.  @code{static} symbols are special and are handled by
   setting the second word in the .non_lazy_symbol_pointer data
   structure to symbol.  See indirect_data for the code that handles
   the extra indirection, and machopic_output_indirection and its use
   of MACHO_SYMBOL_STATIC for the code that handles @code{static}
   symbol indirection.  */

/* For darwin >= 9  (OSX 10.5) the linker is capable of making the necessary
   branch islands and we no longer need to emit darwin stubs.
   However, if we are generating code for earlier systems (or for use in the 
   kernel) the stubs might still be required, and this will be set true.  */
int darwin_emit_branch_islands = false;

/* A flag to determine whether we are running c++ or obj-c++.  This has to be
   settable from non-c-family contexts too (i.e. we can't use the c_dialect_
   functions).  */
int darwin_running_cxx;

/* Section names.  */
section * darwin_sections[NUM_DARWIN_SECTIONS];

/* While we transition to using in-tests instead of ifdef'd code.  */
#ifndef HAVE_lo_sum
#define HAVE_lo_sum 0
#define gen_macho_high(a,b) (a)
#define gen_macho_low(a,b,c) (a)
#endif

/* True if we're setting __attribute__ ((ms_struct)).  */
int darwin_ms_struct = false;

/* Earlier versions of Darwin as do not recognize an alignment field in 
   .comm directives, this should be set for versions that allow it.  */
int emit_aligned_common = false;

/* A get_unnamed_section callback used to switch to an ObjC section.
   DIRECTIVE is as for output_section_asm_op.  */

static void
output_objc_section_asm_op (const void *directive)
{
  static bool been_here = false;

  /* The NeXT ObjC Runtime requires these sections to be present and in 
     order in the object.  The code below implements this by emitting 
     a section header for each ObjC section the first time that an ObjC
     section is requested.  */
  if (! been_here)
    {
      section *saved_in_section = in_section;
      static const enum darwin_section_enum tomark[] =
        {
          /* written, cold -> hot */
          objc_cat_cls_meth_section,
          objc_cat_inst_meth_section,
          objc_string_object_section,
          objc_constant_string_object_section,
          objc_selector_refs_section,
          objc_selector_fixup_section,
          objc_cls_refs_section,
          objc_class_section,
          objc_meta_class_section,
          /* shared, hot -> cold */
          objc_cls_meth_section,
          objc_inst_meth_section,
          objc_protocol_section,
          objc_class_names_section,
          objc_meth_var_types_section,
          objc_meth_var_names_section,
          objc_category_section,
          objc_class_vars_section,
          objc_instance_vars_section,
          objc_module_info_section,
          objc_symbols_section
        };
      size_t i;

      been_here = true;
      for (i = 0; i < ARRAY_SIZE (tomark); i++)
        switch_to_section (darwin_sections[tomark[i]]);
      switch_to_section (saved_in_section);
    }
  output_section_asm_op (directive);
}

/* Implement TARGET_ASM_INIT_SECTIONS.  */

void
darwin_init_sections (void)
{
#define DEF_SECTION(NAME, FLAGS, DIRECTIVE, OBJC)               \
  darwin_sections[NAME] =                                       \
    get_unnamed_section (FLAGS, (OBJC                           \
                                 ? output_objc_section_asm_op   \
                                 : output_section_asm_op),      \
                         "\t" DIRECTIVE);
#include "config/darwin-sections.def"
#undef DEF_SECTION

  readonly_data_section = darwin_sections[const_section];
  exception_section = darwin_sections[darwin_exception_section];
  eh_frame_section = darwin_sections[darwin_eh_frame_section];

  /* Make sure that there is no conflict between the 'no anchor' section
     flag declared in darwin.h and the section flags declared in output.h.  */
  gcc_assert (SECTION_NO_ANCHOR > SECTION_MACH_DEP);
}

int
name_needs_quotes (const char *name)
{
  int c;
  while ((c = *name++) != '\0')
    if (! ISIDNUM (c) 
          && c != '.' && c != '$' && c != '_' )
      return 1;
  return 0;
}

/* Return true if SYM_REF can be used without an indirection.  */
int
machopic_symbol_defined_p (rtx sym_ref)
{
  if (SYMBOL_REF_FLAGS (sym_ref) & MACHO_SYMBOL_FLAG_DEFINED)
    return true;

  /* If a symbol references local and is not an extern to this
     file, then the symbol might be able to declared as defined.  */
  if (SYMBOL_REF_LOCAL_P (sym_ref) && ! SYMBOL_REF_EXTERNAL_P (sym_ref))
    {
      /* If the symbol references a variable and the variable is a
         common symbol, then this symbol is not defined.  */
      if (SYMBOL_REF_FLAGS (sym_ref) & MACHO_SYMBOL_FLAG_VARIABLE)
        {
          tree decl = SYMBOL_REF_DECL (sym_ref);
          if (!decl)
            return true;
          if (DECL_COMMON (decl))
            return false;
        }
      return true;
    }
  return false;
}

/* This module assumes that (const (symbol_ref "foo")) is a legal pic
   reference, which will not be changed.  */

enum machopic_addr_class
machopic_classify_symbol (rtx sym_ref)
{
  bool function_p;

  function_p = SYMBOL_REF_FUNCTION_P (sym_ref);
  if (machopic_symbol_defined_p (sym_ref))
    return (function_p
            ? MACHOPIC_DEFINED_FUNCTION : MACHOPIC_DEFINED_DATA);
  else
    return (function_p
            ? MACHOPIC_UNDEFINED_FUNCTION : MACHOPIC_UNDEFINED_DATA);
}

#ifndef TARGET_FIX_AND_CONTINUE
#define TARGET_FIX_AND_CONTINUE 0
#endif

/* Indicate when fix-and-continue style code generation is being used
   and when a reference to data should be indirected so that it can be
   rebound in a new translation unit to reference the original instance
   of that data.  Symbol names that are for code generation local to
   the translation unit are bound to the new translation unit;
   currently this means symbols that begin with L or _OBJC_;
   otherwise, we indicate that an indirect reference should be made to
   permit the runtime to rebind new instances of the translation unit
   to the original instance of the data.  */

static int
indirect_data (rtx sym_ref)
{
  int lprefix;
  const char *name;

  /* If we aren't generating fix-and-continue code, don't do anything
     special.  */
  if (TARGET_FIX_AND_CONTINUE == 0)
    return 0;

  /* Otherwise, all symbol except symbols that begin with L or _OBJC_
     are indirected.  Symbols that begin with L and _OBJC_ are always
     bound to the current translation unit as they are used for
     generated local data of the translation unit.  */

  name = XSTR (sym_ref, 0);

  lprefix = (((name[0] == '*' || name[0] == '&')
              && (name[1] == 'L' || (name[1] == '"' && name[2] == 'L')))
             || (strncmp (name, "_OBJC_", 6) == 0));

  return ! lprefix;
}


static int
machopic_data_defined_p (rtx sym_ref)
{
  if (indirect_data (sym_ref))
    return 0;

  switch (machopic_classify_symbol (sym_ref))
    {
    case MACHOPIC_DEFINED_DATA:
    case MACHOPIC_DEFINED_FUNCTION:
      return 1;
    default:
      return 0;
    }
}

void
machopic_define_symbol (rtx mem)
{
  rtx sym_ref;

  gcc_assert (GET_CODE (mem) == MEM);
  sym_ref = XEXP (mem, 0);
  SYMBOL_REF_FLAGS (sym_ref) |= MACHO_SYMBOL_FLAG_DEFINED;
}

/* Return either ORIG or:

     (const:P (unspec:P [ORIG] UNSPEC_MACHOPIC_OFFSET))

   depending on MACHO_DYNAMIC_NO_PIC_P.  */
rtx
machopic_gen_offset (rtx orig)
{
  if (MACHO_DYNAMIC_NO_PIC_P)
    return orig;
  else
    {
      /* Play games to avoid marking the function as needing pic if we
         are being called as part of the cost-estimation process.  */
      if (current_ir_type () != IR_GIMPLE || currently_expanding_to_rtl)
        crtl->uses_pic_offset_table = 1;
      orig = gen_rtx_UNSPEC (Pmode, gen_rtvec (1, orig),
                             UNSPEC_MACHOPIC_OFFSET);
      return gen_rtx_CONST (Pmode, orig);
    }
}

static GTY(()) const char * function_base_func_name;
static GTY(()) int current_pic_label_num;

void
machopic_output_function_base_name (FILE *file)
{
  const char *current_name;

  /* If dynamic-no-pic is on, we should not get here.  */
  gcc_assert (!MACHO_DYNAMIC_NO_PIC_P);
  /* When we are generating _get_pc thunks within stubs, there is no current
     function.  */
  if (current_function_decl)
    {
      current_name =
        IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (current_function_decl));
      if (function_base_func_name != current_name)
        {
          ++current_pic_label_num;
          function_base_func_name = current_name;
        }
    }
  else
    {
      ++current_pic_label_num;
      function_base_func_name = "L_machopic_stub_dummy";
    }
  fprintf (file, "L%011d$pb", current_pic_label_num);
}

/* The suffix attached to non-lazy pointer symbols.  */
#define NON_LAZY_POINTER_SUFFIX "$non_lazy_ptr"
/* The suffix attached to stub symbols.  */
#define STUB_SUFFIX "$stub"

typedef struct GTY (()) machopic_indirection
{
  /* The SYMBOL_REF for the entity referenced.  */
  rtx symbol;
  /* The name of the stub or non-lazy pointer.  */
  const char * ptr_name;
  /* True iff this entry is for a stub (as opposed to a non-lazy
     pointer).  */
  bool stub_p;
  /* True iff this stub or pointer pointer has been referenced.  */
  bool used;
} machopic_indirection;

/* A table mapping stub names and non-lazy pointer names to
   SYMBOL_REFs for the stubbed-to and pointed-to entities.  */

static GTY ((param_is (struct machopic_indirection))) htab_t
  machopic_indirections;

/* Return a hash value for a SLOT in the indirections hash table.  */

static hashval_t
machopic_indirection_hash (const void *slot)
{
  const machopic_indirection *p = (const machopic_indirection *) slot;
  return htab_hash_string (p->ptr_name);
}

/* Returns true if the KEY is the same as that associated with
   SLOT.  */

static int
machopic_indirection_eq (const void *slot, const void *key)
{
  return strcmp (((const machopic_indirection *) slot)->ptr_name,
                 (const char *) key) == 0;
}

/* Return the name of the non-lazy pointer (if STUB_P is false) or
   stub (if STUB_B is true) corresponding to the given name.  */

const char *
machopic_indirection_name (rtx sym_ref, bool stub_p)
{
  char *buffer;
  const char *name = XSTR (sym_ref, 0);
  size_t namelen = strlen (name);
  machopic_indirection *p;
  void ** slot;
  bool needs_quotes;
  const char *suffix;
  const char *prefix = user_label_prefix;
  const char *quote = "";
  tree id;

  id = maybe_get_identifier (name);
  if (id)
    {
      tree id_orig = id;

      while (IDENTIFIER_TRANSPARENT_ALIAS (id))
        id = TREE_CHAIN (id);
      if (id != id_orig)
        {
          name = IDENTIFIER_POINTER (id);
          namelen = strlen (name);
        }
    }

  if (name[0] == '*')
    {
      prefix = "";
      ++name;
      --namelen;
    }

  needs_quotes = name_needs_quotes (name);
  if (needs_quotes)
    {
      quote = "\"";
    }

  if (stub_p)
    suffix = STUB_SUFFIX;
  else
    suffix = NON_LAZY_POINTER_SUFFIX;

  buffer = XALLOCAVEC (char, strlen ("&L")
                   + strlen (prefix)
                   + namelen
                   + strlen (suffix)
                   + 2 * strlen (quote)
                   + 1 /* '\0' */);

  /* Construct the name of the non-lazy pointer or stub.  */
  sprintf (buffer, "&%sL%s%s%s%s", quote, prefix, name, suffix, quote);

  if (!machopic_indirections)
    machopic_indirections = htab_create_ggc (37,
                                             machopic_indirection_hash,
                                             machopic_indirection_eq,
                                             /*htab_del=*/NULL);

  slot = htab_find_slot_with_hash (machopic_indirections, buffer,
                                   htab_hash_string (buffer), INSERT);
  if (*slot)
    {
      p = (machopic_indirection *) *slot;
    }
  else
    {
      p = ggc_alloc_machopic_indirection ();
      p->symbol = sym_ref;
      p->ptr_name = xstrdup (buffer);
      p->stub_p = stub_p;
      p->used = false;
      *slot = p;
    }

  return p->ptr_name;
}

/* Return the name of the stub for the mcount function.  */

const char*
machopic_mcount_stub_name (void)
{
  rtx symbol = gen_rtx_SYMBOL_REF (Pmode, "*mcount");
  return machopic_indirection_name (symbol, /*stub_p=*/true);
}

/* If NAME is the name of a stub or a non-lazy pointer , mark the stub
   or non-lazy pointer as used -- and mark the object to which the
   pointer/stub refers as used as well, since the pointer/stub will
   emit a reference to it.  */

void
machopic_validate_stub_or_non_lazy_ptr (const char *name)
{
  machopic_indirection *p;

  p = ((machopic_indirection *)
       (htab_find_with_hash (machopic_indirections, name,
                             htab_hash_string (name))));
  if (p && ! p->used)
    {
      const char *real_name;
      tree id;

      p->used = true;

      /* Do what output_addr_const will do when we actually call it.  */
      if (SYMBOL_REF_DECL (p->symbol))
        mark_decl_referenced (SYMBOL_REF_DECL (p->symbol));

      real_name = targetm.strip_name_encoding (XSTR (p->symbol, 0));

      id = maybe_get_identifier (real_name);
      if (id)
        mark_referenced (id);
    }
}

/* Transform ORIG, which may be any data source, to the corresponding
   source using indirections.  */

rtx
machopic_indirect_data_reference (rtx orig, rtx reg)
{
  rtx ptr_ref = orig;

  if (! MACHOPIC_INDIRECT)
    return orig;

  if (GET_CODE (orig) == SYMBOL_REF)
    {
      int defined = machopic_data_defined_p (orig);

      if (defined && MACHO_DYNAMIC_NO_PIC_P)
        {
          if (DARWIN_PPC)
            {
          /* Create a new register for CSE opportunities.  */
          rtx hi_reg = (!can_create_pseudo_p () ? reg : gen_reg_rtx (Pmode));
          emit_insn (gen_macho_high (hi_reg, orig));
          emit_insn (gen_macho_low (reg, hi_reg, orig));
              return reg;
            }
          else if (DARWIN_X86)
            return orig;
          else
           /* some other cpu -- writeme!  */
           gcc_unreachable ();
        }
      else if (defined)
        {
          rtx offset = NULL;
          if (DARWIN_PPC || HAVE_lo_sum)
            offset = machopic_gen_offset (orig);

          if (DARWIN_PPC)
            {
          rtx hi_sum_reg = (!can_create_pseudo_p ()
                            ? reg
                            : gen_reg_rtx (Pmode));

          gcc_assert (reg);

          emit_insn (gen_rtx_SET (Pmode, hi_sum_reg,
                              gen_rtx_PLUS (Pmode, pic_offset_table_rtx,
                                       gen_rtx_HIGH (Pmode, offset))));
          emit_insn (gen_rtx_SET (Pmode, reg,
                                  gen_rtx_LO_SUM (Pmode, hi_sum_reg,
                                                  copy_rtx (offset))));

          orig = reg;
            }
          else if (HAVE_lo_sum)
            {
          gcc_assert (reg);

          emit_insn (gen_rtx_SET (VOIDmode, reg,
                                  gen_rtx_HIGH (Pmode, offset)));
          emit_insn (gen_rtx_SET (VOIDmode, reg,
                                  gen_rtx_LO_SUM (Pmode, reg,
                                                  copy_rtx (offset))));
          emit_use (pic_offset_table_rtx);

          orig = gen_rtx_PLUS (Pmode, pic_offset_table_rtx, reg);
            }
          return orig;
        }

      ptr_ref = (gen_rtx_SYMBOL_REF
                 (Pmode,
                  machopic_indirection_name (orig, /*stub_p=*/false)));

      SYMBOL_REF_DATA (ptr_ref) = SYMBOL_REF_DATA (orig);

      ptr_ref = gen_const_mem (Pmode, ptr_ref);
      machopic_define_symbol (ptr_ref);

      if (DARWIN_X86 
          && reg 
          && MACHO_DYNAMIC_NO_PIC_P)
        {
            emit_insn (gen_rtx_SET (Pmode, reg, ptr_ref));
            ptr_ref = reg;
        }

      return ptr_ref;
    }
  else if (GET_CODE (orig) == CONST)
    {
      /* If "(const (plus ...", walk the PLUS and return that result.
         PLUS processing (below) will restore the "(const ..." if
         appropriate.  */
      if (GET_CODE (XEXP (orig, 0)) == PLUS)
        return machopic_indirect_data_reference (XEXP (orig, 0), reg);
      else 
        return orig;
    }
  else if (GET_CODE (orig) == MEM)
    {
      XEXP (ptr_ref, 0) = 
                machopic_indirect_data_reference (XEXP (orig, 0), reg);
      return ptr_ref;
    }
  else if (GET_CODE (orig) == PLUS)
    {
      rtx base, result;
      /* When the target is i386, this code prevents crashes due to the
        compiler's ignorance on how to move the PIC base register to
        other registers.  (The reload phase sometimes introduces such
        insns.)  */
      if (GET_CODE (XEXP (orig, 0)) == REG
           && REGNO (XEXP (orig, 0)) == PIC_OFFSET_TABLE_REGNUM
           /* Prevent the same register from being erroneously used
              as both the base and index registers.  */
           && (DARWIN_X86 && (GET_CODE (XEXP (orig, 1)) == CONST))
           && reg)
        {
          emit_move_insn (reg, XEXP (orig, 0));
          XEXP (ptr_ref, 0) = reg;
          return ptr_ref;
        }

      /* Legitimize both operands of the PLUS.  */
      base = machopic_indirect_data_reference (XEXP (orig, 0), reg);
      orig = machopic_indirect_data_reference (XEXP (orig, 1),
                                               (base == reg ? 0 : reg));
      if (MACHOPIC_INDIRECT && (GET_CODE (orig) == CONST_INT))
        result = plus_constant (base, INTVAL (orig));
      else
        result = gen_rtx_PLUS (Pmode, base, orig);

      if (MACHOPIC_JUST_INDIRECT && GET_CODE (base) == MEM)
        {
          if (reg)
            {
              emit_move_insn (reg, result);
              result = reg;
            }
          else
            {
              result = force_reg (GET_MODE (result), result);
            }
        }

      return result;
    }
  return ptr_ref;
}

/* Transform TARGET (a MEM), which is a function call target, to the
   corresponding symbol_stub if necessary.  Return a new MEM.  */

rtx
machopic_indirect_call_target (rtx target)
{
  if (! darwin_emit_branch_islands)
    return target;

  if (GET_CODE (target) != MEM)
    return target;

  if (MACHOPIC_INDIRECT
      && GET_CODE (XEXP (target, 0)) == SYMBOL_REF
      && !(SYMBOL_REF_FLAGS (XEXP (target, 0))
           & MACHO_SYMBOL_FLAG_DEFINED))
    {
      rtx sym_ref = XEXP (target, 0);
      const char *stub_name = machopic_indirection_name (sym_ref,
                                                         /*stub_p=*/true);
      enum machine_mode mode = GET_MODE (sym_ref);

      XEXP (target, 0) = gen_rtx_SYMBOL_REF (mode, stub_name);
      SYMBOL_REF_DATA (XEXP (target, 0)) = SYMBOL_REF_DATA (sym_ref);
      MEM_READONLY_P (target) = 1;
      MEM_NOTRAP_P (target) = 1;
    }

  return target;
}

rtx
machopic_legitimize_pic_address (rtx orig, enum machine_mode mode, rtx reg)
{
  rtx pic_ref = orig;

  if (! MACHOPIC_INDIRECT)
    return orig;

  /* First handle a simple SYMBOL_REF or LABEL_REF */
  if (GET_CODE (orig) == LABEL_REF
      || (GET_CODE (orig) == SYMBOL_REF
          ))
    {
      /* addr(foo) = &func+(foo-func) */
      orig = machopic_indirect_data_reference (orig, reg);

      if (GET_CODE (orig) == PLUS
          && GET_CODE (XEXP (orig, 0)) == REG)
        {
          if (reg == 0)
            return force_reg (mode, orig);

          emit_move_insn (reg, orig);
          return reg;
        }

      if (GET_CODE (orig) == MEM)
        {
          if (reg == 0)
            {
              gcc_assert (!reload_in_progress);
              reg = gen_reg_rtx (Pmode);
            }

#if HAVE_lo_sum
          if (MACHO_DYNAMIC_NO_PIC_P
              && (GET_CODE (XEXP (orig, 0)) == SYMBOL_REF
                  || GET_CODE (XEXP (orig, 0)) == LABEL_REF))
            {
#if defined (TARGET_TOC)        /* ppc  */
              rtx temp_reg = (!can_create_pseudo_p ()
                              ? reg :
                              gen_reg_rtx (Pmode));
              rtx asym = XEXP (orig, 0);
              rtx mem;

              emit_insn (gen_macho_high (temp_reg, asym));
              mem = gen_const_mem (GET_MODE (orig),
                                   gen_rtx_LO_SUM (Pmode, temp_reg,
                                                   copy_rtx (asym)));
              emit_insn (gen_rtx_SET (VOIDmode, reg, mem));
#else
              /* Some other CPU -- WriteMe! but right now there are no other
                 platforms that can use dynamic-no-pic  */
              gcc_unreachable ();
#endif
              pic_ref = reg;
            }
          else
          if (GET_CODE (XEXP (orig, 0)) == SYMBOL_REF
              || GET_CODE (XEXP (orig, 0)) == LABEL_REF)
            {
              rtx offset = machopic_gen_offset (XEXP (orig, 0));
#if defined (TARGET_TOC) /* i.e., PowerPC */
              /* Generating a new reg may expose opportunities for
                 common subexpression elimination.  */
              rtx hi_sum_reg = (!can_create_pseudo_p ()
                                ? reg
                                : gen_reg_rtx (Pmode));
              rtx mem;
              rtx insn;
              rtx sum;

              sum = gen_rtx_HIGH (Pmode, offset);
              if (! MACHO_DYNAMIC_NO_PIC_P)
                sum = gen_rtx_PLUS (Pmode, pic_offset_table_rtx, sum);

              emit_insn (gen_rtx_SET (Pmode, hi_sum_reg, sum));

              mem = gen_const_mem (GET_MODE (orig),
                                  gen_rtx_LO_SUM (Pmode,
                                                  hi_sum_reg,
                                                  copy_rtx (offset)));
              insn = emit_insn (gen_rtx_SET (VOIDmode, reg, mem));
              set_unique_reg_note (insn, REG_EQUAL, pic_ref);

              pic_ref = reg;
#else
              emit_use (gen_rtx_REG (Pmode, PIC_OFFSET_TABLE_REGNUM));

              emit_insn (gen_rtx_SET (VOIDmode, reg,
                                      gen_rtx_HIGH (Pmode,
                                                    gen_rtx_CONST (Pmode,
                                                                   offset))));
              emit_insn (gen_rtx_SET (VOIDmode, reg,
                                  gen_rtx_LO_SUM (Pmode, reg,
                                           gen_rtx_CONST (Pmode,
                                                          copy_rtx (offset)))));
              pic_ref = gen_rtx_PLUS (Pmode,
                                      pic_offset_table_rtx, reg);
#endif
            }
          else
#endif  /* HAVE_lo_sum */
            {
              rtx pic = pic_offset_table_rtx;
              if (GET_CODE (pic) != REG)
                {
                  emit_move_insn (reg, pic);
                  pic = reg;
                }
#if 0
              emit_use (gen_rtx_REG (Pmode, PIC_OFFSET_TABLE_REGNUM));
#endif

              if (reload_in_progress)
                df_set_regs_ever_live (REGNO (pic), true);
              pic_ref = gen_rtx_PLUS (Pmode, pic,
                                      machopic_gen_offset (XEXP (orig, 0)));
            }

#if !defined (TARGET_TOC)
          emit_move_insn (reg, pic_ref);
          pic_ref = gen_const_mem (GET_MODE (orig), reg);
#endif
        }
      else
        {

#if HAVE_lo_sum
          if (GET_CODE (orig) == SYMBOL_REF
              || GET_CODE (orig) == LABEL_REF)
            {
              rtx offset = machopic_gen_offset (orig);
#if defined (TARGET_TOC) /* i.e., PowerPC */
              rtx hi_sum_reg;

              if (reg == 0)
                {
                  gcc_assert (!reload_in_progress);
                  reg = gen_reg_rtx (Pmode);
                }

              hi_sum_reg = reg;

              emit_insn (gen_rtx_SET (Pmode, hi_sum_reg,
                                      (MACHO_DYNAMIC_NO_PIC_P)
                                      ? gen_rtx_HIGH (Pmode, offset)
                                      : gen_rtx_PLUS (Pmode,
                                                      pic_offset_table_rtx,
                                                      gen_rtx_HIGH (Pmode,
                                                                    offset))));
              emit_insn (gen_rtx_SET (VOIDmode, reg,
                                      gen_rtx_LO_SUM (Pmode,
                                                      hi_sum_reg,
                                                      copy_rtx (offset))));
              pic_ref = reg;
#else
              emit_insn (gen_rtx_SET (VOIDmode, reg,
                                      gen_rtx_HIGH (Pmode, offset)));
              emit_insn (gen_rtx_SET (VOIDmode, reg,
                                      gen_rtx_LO_SUM (Pmode, reg,
                                                      copy_rtx (offset))));
              pic_ref = gen_rtx_PLUS (Pmode,
                                      pic_offset_table_rtx, reg);
#endif
            }
          else
#endif  /*  HAVE_lo_sum  */
            {
              if (REG_P (orig)
                  || GET_CODE (orig) == SUBREG)
                {
                  return orig;
                }
              else
                {
                  rtx pic = pic_offset_table_rtx;
                  if (GET_CODE (pic) != REG)
                    {
                      emit_move_insn (reg, pic);
                      pic = reg;
                    }
#if 0
                  emit_use (pic_offset_table_rtx);
#endif
                  if (reload_in_progress)
                    df_set_regs_ever_live (REGNO (pic), true);
                  pic_ref = gen_rtx_PLUS (Pmode,
                                          pic,
                                          machopic_gen_offset (orig));
                }
            }
        }

      if (GET_CODE (pic_ref) != REG)
        {
          if (reg != 0)
            {
              emit_move_insn (reg, pic_ref);
              return reg;
            }
          else
            {
              return force_reg (mode, pic_ref);
            }
        }
      else
        {
          return pic_ref;
        }
    }

  else if (GET_CODE (orig) == SYMBOL_REF)
    return orig;

  else if (GET_CODE (orig) == PLUS
           && (GET_CODE (XEXP (orig, 0)) == MEM
               || GET_CODE (XEXP (orig, 0)) == SYMBOL_REF
               || GET_CODE (XEXP (orig, 0)) == LABEL_REF)
           && XEXP (orig, 0) != pic_offset_table_rtx
           && GET_CODE (XEXP (orig, 1)) != REG)

    {
      rtx base;
      int is_complex = (GET_CODE (XEXP (orig, 0)) == MEM);

      base = machopic_legitimize_pic_address (XEXP (orig, 0), Pmode, reg);
      orig = machopic_legitimize_pic_address (XEXP (orig, 1),
                                              Pmode, (base == reg ? 0 : reg));
      if (GET_CODE (orig) == CONST_INT)
        {
          pic_ref = plus_constant (base, INTVAL (orig));
          is_complex = 1;
        }
      else
        pic_ref = gen_rtx_PLUS (Pmode, base, orig);

      if (reg && is_complex)
        {
          emit_move_insn (reg, pic_ref);
          pic_ref = reg;
        }
      /* Likewise, should we set special REG_NOTEs here?  */
    }

  else if (GET_CODE (orig) == CONST)
    {
      return machopic_legitimize_pic_address (XEXP (orig, 0), Pmode, reg);
    }

  else if (GET_CODE (orig) == MEM
           && GET_CODE (XEXP (orig, 0)) == SYMBOL_REF)
    {
      rtx addr = machopic_legitimize_pic_address (XEXP (orig, 0), Pmode, reg);
      addr = replace_equiv_address (orig, addr);
      emit_move_insn (reg, addr);
      pic_ref = reg;
    }

  return pic_ref;
}

/* Output the stub or non-lazy pointer in *SLOT, if it has been used.
   DATA is the FILE* for assembly output.  Called from
   htab_traverse.  */

static int
machopic_output_indirection (void **slot, void *data)
{
  machopic_indirection *p = *((machopic_indirection **) slot);
  FILE *asm_out_file = (FILE *) data;
  rtx symbol;
  const char *sym_name;
  const char *ptr_name;

  if (!p->used)
    return 1;

  symbol = p->symbol;
  sym_name = XSTR (symbol, 0);
  ptr_name = p->ptr_name;

  if (p->stub_p)
    {
      char *sym;
      char *stub;
      tree id;

      id = maybe_get_identifier (sym_name);
      if (id)
        {
          tree id_orig = id;

          while (IDENTIFIER_TRANSPARENT_ALIAS (id))
            id = TREE_CHAIN (id);
          if (id != id_orig)
            sym_name = IDENTIFIER_POINTER (id);
        }

      sym = XALLOCAVEC (char, strlen (sym_name) + 2);
      if (sym_name[0] == '*' || sym_name[0] == '&')
        strcpy (sym, sym_name + 1);
      else if (sym_name[0] == '-' || sym_name[0] == '+')
        strcpy (sym, sym_name);
      else
        sprintf (sym, "%s%s", user_label_prefix, sym_name);

      stub = XALLOCAVEC (char, strlen (ptr_name) + 2);
      if (ptr_name[0] == '*' || ptr_name[0] == '&')
        strcpy (stub, ptr_name + 1);
      else
        sprintf (stub, "%s%s", user_label_prefix, ptr_name);

      machopic_output_stub (asm_out_file, sym, stub);
    }
  else if (! indirect_data (symbol)
           && (machopic_symbol_defined_p (symbol)
               || SYMBOL_REF_LOCAL_P (symbol)))
    {
      switch_to_section (data_section);
      assemble_align (GET_MODE_ALIGNMENT (Pmode));
      assemble_label (asm_out_file, ptr_name);
      assemble_integer (gen_rtx_SYMBOL_REF (Pmode, sym_name),
                        GET_MODE_SIZE (Pmode),
                        GET_MODE_ALIGNMENT (Pmode), 1);
    }
  else
    {
      rtx init = const0_rtx;

      switch_to_section (darwin_sections[machopic_nl_symbol_ptr_section]);

      /* Mach-O symbols are passed around in code through indirect
         references and the original symbol_ref hasn't passed through
         the generic handling and reference-catching in
         output_operand, so we need to manually mark weak references
         as such.  */
      if (SYMBOL_REF_WEAK (symbol))
        {
          tree decl = SYMBOL_REF_DECL (symbol);
          gcc_assert (DECL_P (decl));

          if (decl != NULL_TREE
              && DECL_EXTERNAL (decl) && TREE_PUBLIC (decl)
              /* Handle only actual external-only definitions, not
                 e.g. extern inline code or variables for which
                 storage has been allocated.  */
              && !TREE_STATIC (decl))
            {
              fputs ("\t.weak_reference ", asm_out_file);
              assemble_name (asm_out_file, sym_name);
              fputc ('\n', asm_out_file);
            }
        }

      assemble_name (asm_out_file, ptr_name);
      fprintf (asm_out_file, ":\n");

      fprintf (asm_out_file, "\t.indirect_symbol ");
      assemble_name (asm_out_file, sym_name);
      fprintf (asm_out_file, "\n");

      /* Variables that are marked with MACHO_SYMBOL_STATIC need to
         have their symbol name instead of 0 in the second entry of
         the non-lazy symbol pointer data structure when they are
         defined.  This allows the runtime to rebind newer instances
         of the translation unit with the original instance of the
         symbol.  */

      if ((SYMBOL_REF_FLAGS (symbol) & MACHO_SYMBOL_STATIC)
          && machopic_symbol_defined_p (symbol))
        init = gen_rtx_SYMBOL_REF (Pmode, sym_name);

      assemble_integer (init, GET_MODE_SIZE (Pmode),
                        GET_MODE_ALIGNMENT (Pmode), 1);
    }

  return 1;
}

void
machopic_finish (FILE *asm_out_file)
{
  if (machopic_indirections)
    htab_traverse_noresize (machopic_indirections,
                            machopic_output_indirection,
                            asm_out_file);
}

int
machopic_operand_p (rtx op)
{
  if (MACHOPIC_JUST_INDIRECT)
    return (GET_CODE (op) == SYMBOL_REF
            && machopic_symbol_defined_p (op));
  else
    return (GET_CODE (op) == CONST
            && GET_CODE (XEXP (op, 0)) == UNSPEC
            && XINT (XEXP (op, 0), 1) == UNSPEC_MACHOPIC_OFFSET);
}

/* This function records whether a given name corresponds to a defined
   or undefined function or variable, for machopic_classify_ident to
   use later.  */

void
darwin_encode_section_info (tree decl, rtx rtl, int first ATTRIBUTE_UNUSED)
{
  rtx sym_ref;

  /* Do the standard encoding things first.  */
  default_encode_section_info (decl, rtl, first);

  if (TREE_CODE (decl) != FUNCTION_DECL && TREE_CODE (decl) != VAR_DECL)
    return;

  sym_ref = XEXP (rtl, 0);
  if (TREE_CODE (decl) == VAR_DECL)
    SYMBOL_REF_FLAGS (sym_ref) |= MACHO_SYMBOL_FLAG_VARIABLE;

  if (!DECL_EXTERNAL (decl)
      && (!TREE_PUBLIC (decl) || !DECL_WEAK (decl))
      && ! lookup_attribute ("weakref", DECL_ATTRIBUTES (decl))
      && ((TREE_STATIC (decl)
           && (!DECL_COMMON (decl) || !TREE_PUBLIC (decl)))
          || (!DECL_COMMON (decl) && DECL_INITIAL (decl)
              && DECL_INITIAL (decl) != error_mark_node)))
    SYMBOL_REF_FLAGS (sym_ref) |= MACHO_SYMBOL_FLAG_DEFINED;

  if (! TREE_PUBLIC (decl))
    SYMBOL_REF_FLAGS (sym_ref) |= MACHO_SYMBOL_STATIC;
}

void
darwin_mark_decl_preserved (const char *name)
{
  fprintf (asm_out_file, "\t.no_dead_strip ");
  assemble_name (asm_out_file, name);
  fputc ('\n', asm_out_file);
}

static section *
darwin_text_section (int reloc, int weak)
{
  if (reloc)
    return (weak
            ? darwin_sections[text_unlikely_coal_section]
            : unlikely_text_section ());
  else
    return (weak
            ? darwin_sections[text_coal_section]
            : text_section);
}

static section *
darwin_rodata_section (int weak, bool zsize)
{
  return (weak
          ? darwin_sections[const_coal_section]
          : (zsize ? darwin_sections[zobj_const_section]
                   : darwin_sections[const_section]));
}

static section *
darwin_mergeable_string_section (tree exp,
                                 unsigned HOST_WIDE_INT align)
{
  if (flag_merge_constants
      && TREE_CODE (exp) == STRING_CST
      && TREE_CODE (TREE_TYPE (exp)) == ARRAY_TYPE
      && align <= 256
      && (int_size_in_bytes (TREE_TYPE (exp))
          == TREE_STRING_LENGTH (exp))
      && ((size_t) TREE_STRING_LENGTH (exp)
          == strlen (TREE_STRING_POINTER (exp)) + 1))
    return darwin_sections[cstring_section];

  if (DARWIN_SECTION_ANCHORS && flag_section_anchors
      && TREE_CODE (exp) == STRING_CST
      && TREE_STRING_LENGTH (exp) == 0)
    return darwin_sections[zobj_const_section];

  return readonly_data_section;
}

#ifndef HAVE_GAS_LITERAL16
#define HAVE_GAS_LITERAL16 0
#endif

static section *
darwin_mergeable_constant_section (tree exp,
                                   unsigned HOST_WIDE_INT align,
                                   bool zsize)
{
  enum machine_mode mode = DECL_MODE (exp);
  unsigned int modesize = GET_MODE_BITSIZE (mode);

  if (DARWIN_SECTION_ANCHORS 
      && flag_section_anchors 
      && zsize)
    return darwin_sections[zobj_const_section];

  if (flag_merge_constants
      && mode != VOIDmode
      && mode != BLKmode
      && modesize <= align
      && align >= 8
      && align <= 256
      && (align & (align -1)) == 0)
    {
      tree size = TYPE_SIZE_UNIT (TREE_TYPE (exp));

      if (TREE_CODE (size) == INTEGER_CST
          && TREE_INT_CST_LOW (size) == 4
          && TREE_INT_CST_HIGH (size) == 0)
        return darwin_sections[literal4_section];
      else if (TREE_CODE (size) == INTEGER_CST
               && TREE_INT_CST_LOW (size) == 8
               && TREE_INT_CST_HIGH (size) == 0)
        return darwin_sections[literal8_section];
      else if (HAVE_GAS_LITERAL16
               && TARGET_64BIT
               && TREE_CODE (size) == INTEGER_CST
               && TREE_INT_CST_LOW (size) == 16
               && TREE_INT_CST_HIGH (size) == 0)
        return darwin_sections[literal16_section];
      else
        return readonly_data_section;
    }

  return readonly_data_section;
}

int
machopic_reloc_rw_mask (void)
{
  return MACHOPIC_INDIRECT ? 3 : 0;
}

section *
machopic_select_section (tree decl,
                         int reloc,
                         unsigned HOST_WIDE_INT align)
{
  bool zsize, one, weak, ro;
  section *base_section = NULL;

  weak = (DECL_P (decl)
          && DECL_WEAK (decl)
          && !lookup_attribute ("weak_import", DECL_ATTRIBUTES (decl)));

  zsize = (DECL_P (decl) 
           && (TREE_CODE (decl) == VAR_DECL || TREE_CODE (decl) == CONST_DECL) 
           && tree_low_cst (DECL_SIZE_UNIT (decl), 1) == 0);

  one = DECL_P (decl) 
        && TREE_CODE (decl) == VAR_DECL 
        && DECL_ONE_ONLY (decl);

  ro = TREE_READONLY (decl) || TREE_CONSTANT (decl) ;

  switch (categorize_decl_for_section (decl, reloc))
    {
    case SECCAT_TEXT:
      {
        struct cgraph_node *node;
        if (decl && TREE_CODE (decl) == FUNCTION_DECL
            && (node = cgraph_get_node (decl)) != NULL)
          base_section = darwin_function_section (decl,
                                                  node->frequency,
                                                  node->only_called_at_startup,
                                                  node->only_called_at_exit);
        if (!base_section)
          base_section = darwin_text_section (reloc, weak);
      }
      break;

    case SECCAT_RODATA:
    case SECCAT_SRODATA:
      base_section = darwin_rodata_section (weak, zsize);
      break;

    case SECCAT_RODATA_MERGE_STR:
      base_section = darwin_mergeable_string_section (decl, align);
      break;

    case SECCAT_RODATA_MERGE_STR_INIT:
      base_section = darwin_mergeable_string_section (DECL_INITIAL (decl), align);
      break;

    case SECCAT_RODATA_MERGE_CONST:
      base_section =  darwin_mergeable_constant_section (decl, align, zsize);
      break;

    case SECCAT_DATA:
    case SECCAT_DATA_REL:
    case SECCAT_DATA_REL_LOCAL:
    case SECCAT_DATA_REL_RO:
    case SECCAT_DATA_REL_RO_LOCAL:
    case SECCAT_SDATA:
    case SECCAT_TDATA:
      if (weak || one)
        {
          if (ro)
            base_section = darwin_sections[const_data_coal_section];
          else 
            base_section = darwin_sections[data_coal_section];
        }
      else if (DARWIN_SECTION_ANCHORS 
               && flag_section_anchors
               && zsize)
        {
          /* If we're doing section anchors, then punt zero-sized objects into
             their own sections so that they don't interfere with offset
             computation for the remaining vars.  This does not need to be done
             for stuff in mergeable sections, since these are ineligible for 
             anchors.  */
          if (ro)
            base_section = darwin_sections[zobj_const_data_section];
          else
            base_section = darwin_sections[zobj_data_section];
        }
      else if (ro)
        base_section = darwin_sections[const_data_section];
      else
        base_section = data_section;
      break;
    case SECCAT_BSS:
    case SECCAT_SBSS:
    case SECCAT_TBSS:
      if (weak || one) 
        base_section = darwin_sections[data_coal_section];
      else
        {
          if (!TREE_PUBLIC (decl))
            base_section = lcomm_section;
          else if (bss_noswitch_section)
            base_section = bss_noswitch_section;
          else
            base_section = data_section;
        }
      break;

    default:
      gcc_unreachable ();
    }

  /* Darwin weird special cases.  */
  if (TREE_CODE (decl) == CONSTRUCTOR
      && TREE_TYPE (decl)
      && TREE_CODE (TREE_TYPE (decl)) == RECORD_TYPE
      && TYPE_NAME (TREE_TYPE (decl)))
    {
      tree name = TYPE_NAME (TREE_TYPE (decl));
      if (TREE_CODE (name) == TYPE_DECL)
        name = DECL_NAME (name);

      if (!strcmp (IDENTIFIER_POINTER (name), "__builtin_ObjCString"))
        {
          if (flag_next_runtime)
            return darwin_sections[objc_constant_string_object_section];
          else
            return darwin_sections[objc_string_object_section];
        }
      else if (!strcmp (IDENTIFIER_POINTER (name), "__builtin_CFString"))
        return darwin_sections[cfstring_constant_object_section];
      else
        return base_section;
    }
  else if (TREE_CODE (decl) == VAR_DECL
           && DECL_NAME (decl)
           && TREE_CODE (DECL_NAME (decl)) == IDENTIFIER_NODE
           && IDENTIFIER_POINTER (DECL_NAME (decl))
           && !strncmp (IDENTIFIER_POINTER (DECL_NAME (decl)), "_OBJC_", 6))
    {
      const char *name = IDENTIFIER_POINTER (DECL_NAME (decl));

      /* We shall assert that zero-sized objects are an error in ObjC 
         meta-data.  */
      gcc_assert (tree_low_cst (DECL_SIZE_UNIT (decl), 1) != 0);
      if (!strncmp (name, "_OBJC_CLASS_METHODS_", 20))
        return darwin_sections[objc_cls_meth_section];
      else if (!strncmp (name, "_OBJC_INSTANCE_METHODS_", 23))
        return darwin_sections[objc_inst_meth_section];
      else if (!strncmp (name, "_OBJC_CATEGORY_CLASS_METHODS_", 29))
        return darwin_sections[objc_cat_cls_meth_section];
      else if (!strncmp (name, "_OBJC_CATEGORY_INSTANCE_METHODS_", 32))
        return darwin_sections[objc_cat_inst_meth_section];
      else if (!strncmp (name, "_OBJC_CLASS_VARIABLES_", 22))
        return darwin_sections[objc_class_vars_section];
      else if (!strncmp (name, "_OBJC_INSTANCE_VARIABLES_", 25))
        return darwin_sections[objc_instance_vars_section];
      else if (!strncmp (name, "_OBJC_CLASS_PROTOCOLS_", 22))
        return darwin_sections[objc_cat_cls_meth_section];
      else if (!strncmp (name, "_OBJC_CLASS_NAME_", 17))
        return darwin_sections[objc_class_names_section];
      else if (!strncmp (name, "_OBJC_METH_VAR_NAME_", 20))
        return darwin_sections[objc_meth_var_names_section];
      else if (!strncmp (name, "_OBJC_METH_VAR_TYPE_", 20))
        return darwin_sections[objc_meth_var_types_section];
      else if (!strncmp (name, "_OBJC_CLASS_REFERENCES", 22))
        return darwin_sections[objc_cls_refs_section];
      else if (!strncmp (name, "_OBJC_CLASS_", 12))
        return darwin_sections[objc_class_section];
      else if (!strncmp (name, "_OBJC_METACLASS_", 16))
        return darwin_sections[objc_meta_class_section];
      else if (!strncmp (name, "_OBJC_CATEGORY_", 15))
        return darwin_sections[objc_category_section];
      else if (!strncmp (name, "_OBJC_SELECTOR_REFERENCES", 25))
        return darwin_sections[objc_selector_refs_section];
      else if (!strncmp (name, "_OBJC_SELECTOR_FIXUP", 20))
        return darwin_sections[objc_selector_fixup_section];
      else if (!strncmp (name, "_OBJC_SYMBOLS", 13))
        return darwin_sections[objc_symbols_section];
      else if (!strncmp (name, "_OBJC_MODULES", 13))
        return darwin_sections[objc_module_info_section];
      else if (!strncmp (name, "_OBJC_IMAGE_INFO", 16))
        return darwin_sections[objc_image_info_section];
      else if (!strncmp (name, "_OBJC_PROTOCOL_INSTANCE_METHODS_", 32))
        return darwin_sections[objc_cat_inst_meth_section];
      else if (!strncmp (name, "_OBJC_PROTOCOL_CLASS_METHODS_", 29))
        return darwin_sections[objc_cat_cls_meth_section];
      else if (!strncmp (name, "_OBJC_PROTOCOL_REFS_", 20))
        return darwin_sections[objc_cat_cls_meth_section];
      else if (!strncmp (name, "_OBJC_PROTOCOL_", 15))
        return darwin_sections[objc_protocol_section];
      else
        return base_section;
    }

  return base_section;
}

/* This can be called with address expressions as "rtx".
   They must go in "const".  */

section *
machopic_select_rtx_section (enum machine_mode mode, rtx x,
                             unsigned HOST_WIDE_INT align ATTRIBUTE_UNUSED)
{
  if (GET_MODE_SIZE (mode) == 8
      && (GET_CODE (x) == CONST_INT
          || GET_CODE (x) == CONST_DOUBLE))
    return darwin_sections[literal8_section];
  else if (GET_MODE_SIZE (mode) == 4
           && (GET_CODE (x) == CONST_INT
               || GET_CODE (x) == CONST_DOUBLE))
    return darwin_sections[literal4_section];
  else if (HAVE_GAS_LITERAL16
           && TARGET_64BIT
           && GET_MODE_SIZE (mode) == 16
           && (GET_CODE (x) == CONST_INT
               || GET_CODE (x) == CONST_DOUBLE
               || GET_CODE (x) == CONST_VECTOR))
    return darwin_sections[literal16_section];
  else if (MACHOPIC_INDIRECT
           && (GET_CODE (x) == SYMBOL_REF
               || GET_CODE (x) == CONST
               || GET_CODE (x) == LABEL_REF))
    return darwin_sections[const_data_section];
  else
    return darwin_sections[const_section];
}

void
machopic_asm_out_constructor (rtx symbol, int priority ATTRIBUTE_UNUSED)
{
  if (MACHOPIC_INDIRECT)
    switch_to_section (darwin_sections[mod_init_section]);
  else
    switch_to_section (darwin_sections[constructor_section]);
  assemble_align (POINTER_SIZE);
  assemble_integer (symbol, POINTER_SIZE / BITS_PER_UNIT, POINTER_SIZE, 1);

  if (! MACHOPIC_INDIRECT)
    fprintf (asm_out_file, ".reference .constructors_used\n");
}

void
machopic_asm_out_destructor (rtx symbol, int priority ATTRIBUTE_UNUSED)
{
  if (MACHOPIC_INDIRECT)
    switch_to_section (darwin_sections[mod_term_section]);
  else
    switch_to_section (darwin_sections[destructor_section]);
  assemble_align (POINTER_SIZE);
  assemble_integer (symbol, POINTER_SIZE / BITS_PER_UNIT, POINTER_SIZE, 1);

  if (! MACHOPIC_INDIRECT)
    fprintf (asm_out_file, ".reference .destructors_used\n");
}

void
darwin_globalize_label (FILE *stream, const char *name)
{
  if (!!strncmp (name, "_OBJC_", 6))
    default_globalize_label (stream, name);
}

/* This routine returns non-zero if 'name' starts with the special objective-c 
   anonymous file-scope static name.  It accommodates c++'s mangling of such 
   symbols (in this case the symbols will have form _ZL{d}*_OBJC_* d=digit).  */
   
int 
darwin_label_is_anonymous_local_objc_name (const char *name)
{
  const unsigned char *p = (const unsigned char *) name;
  if (*p != '_')
    return 0;
  if (p[1] == 'Z' && p[2] == 'L')
  {
    p += 3;
    while (*p >= '0' && *p <= '9')
      p++;
  }
  return (!strncmp ((const char *)p, "_OBJC_", 6));
}

/* LTO support for Mach-O.  */

/* Section names for LTO sections.  */
static unsigned int lto_section_names_offset = 0;

/* This is the obstack which we use to allocate the many strings.  */
static struct obstack lto_section_names_obstack;

/* Segment name for LTO sections.  */
#define LTO_SEGMENT_NAME "__GNU_LTO"

/* Section name for LTO section names section.  */
#define LTO_NAMES_SECTION "__section_names"

/* File to temporarily store LTO data.  This is appended to asm_out_file
   in darwin_end_file.  */
static FILE *lto_asm_out_file, *saved_asm_out_file;
static char *lto_asm_out_name;

/* Prepare asm_out_file for LTO output.  For darwin, this means hiding
   asm_out_file and switching to an alternative output file.  */
void
darwin_asm_lto_start (void)
{
  gcc_assert (! saved_asm_out_file);
  saved_asm_out_file = asm_out_file;
  if (! lto_asm_out_name)
    lto_asm_out_name = make_temp_file (".lto.s");
  lto_asm_out_file = fopen (lto_asm_out_name, "a");
  if (lto_asm_out_file == NULL)
    fatal_error ("failed to open temporary file %s for LTO output",
                 lto_asm_out_name);
  asm_out_file = lto_asm_out_file;
}

/* Restore asm_out_file.  */
void
darwin_asm_lto_end (void)
{
  gcc_assert (saved_asm_out_file);
  fclose (lto_asm_out_file);
  asm_out_file = saved_asm_out_file;
  saved_asm_out_file = NULL;
}

static void
darwin_asm_dwarf_section (const char *name, unsigned int flags, tree decl);

/*  Called for the TARGET_ASM_NAMED_SECTION hook.  */

void
darwin_asm_named_section (const char *name,
                          unsigned int flags,
                          tree decl ATTRIBUTE_UNUSED)
{
  /* LTO sections go in a special segment __GNU_LTO.  We want to replace the
     section name with something we can use to represent arbitrary-length
     names (section names in Mach-O are at most 16 characters long).  */
  if (strncmp (name, LTO_SECTION_NAME_PREFIX,
               strlen (LTO_SECTION_NAME_PREFIX)) == 0)
    {
      /* We expect certain flags to be set...  */
      gcc_assert ((flags & (SECTION_DEBUG | SECTION_NAMED))
                  == (SECTION_DEBUG | SECTION_NAMED));

      /* Add the section name to the things to output when we end the
         current assembler output file.
         This is all not very efficient, but that doesn't matter -- this
         shouldn't be a hot path in the compiler...  */
      obstack_1grow (&lto_section_names_obstack, '\t');
      obstack_grow (&lto_section_names_obstack, ".ascii ", 7);
      obstack_1grow (&lto_section_names_obstack, '"');
      obstack_grow (&lto_section_names_obstack, name, strlen (name));
      obstack_grow (&lto_section_names_obstack, "\\0\"\n", 4);

      /* Output the dummy section name.  */
      fprintf (asm_out_file, "\t# %s\n", name);
      fprintf (asm_out_file, "\t.section %s,__%08X,regular,debug\n",
               LTO_SEGMENT_NAME, lto_section_names_offset);

      /* Update the offset for the next section name.  Make sure we stay
         within reasonable length.  */  
      lto_section_names_offset += strlen (name) + 1;
      gcc_assert (lto_section_names_offset > 0
                  && lto_section_names_offset < ((unsigned) 1 << 31));
    }
  else if (strncmp (name, "__DWARF,", 8) == 0)
    darwin_asm_dwarf_section (name, flags, decl);
  else
    fprintf (asm_out_file, "\t.section %s\n", name);
}

void
darwin_unique_section (tree decl ATTRIBUTE_UNUSED, int reloc ATTRIBUTE_UNUSED)
{
  /* Darwin does not use unique sections.  */
}

/* Handle __attribute__ ((apple_kext_compatibility)).
   This only applies to darwin kexts for 2.95 compatibility -- it shrinks the
   vtable for classes with this attribute (and their descendants) by not
   outputting the new 3.0 nondeleting destructor.  This means that such
   objects CANNOT be allocated on the stack or as globals UNLESS they have
   a completely empty `operator delete'.
   Luckily, this fits in with the Darwin kext model.

   This attribute also disables gcc3's potential overlaying of derived
   class data members on the padding at the end of the base class.  */

tree
darwin_handle_kext_attribute (tree *node, tree name,
                              tree args ATTRIBUTE_UNUSED,
                              int flags ATTRIBUTE_UNUSED,
                              bool *no_add_attrs)
{
  /* APPLE KEXT stuff -- only applies with pure static C++ code.  */
  if (! TARGET_KEXTABI)
    {
      warning (0, "%qE 2.95 vtable-compatibility attribute applies "
               "only when compiling a kext", name);

      *no_add_attrs = true;
    }
  else if (TREE_CODE (*node) != RECORD_TYPE)
    {
      warning (0, "%qE 2.95 vtable-compatibility attribute applies "
               "only to C++ classes", name);

      *no_add_attrs = true;
    }

  return NULL_TREE;
}

/* Handle a "weak_import" attribute; arguments as in
   struct attribute_spec.handler.  */

tree
darwin_handle_weak_import_attribute (tree *node, tree name,
                                     tree ARG_UNUSED (args),
                                     int ARG_UNUSED (flags),
                                     bool * no_add_attrs)
{
  if (TREE_CODE (*node) != FUNCTION_DECL && TREE_CODE (*node) != VAR_DECL)
    {
      warning (OPT_Wattributes, "%qE attribute ignored",
               name);
      *no_add_attrs = true;
    }
  else
    declare_weak (*node);

  return NULL_TREE;
}

/* Emit a label for an FDE, making it global and/or weak if appropriate.
   The third parameter is nonzero if this is for exception handling.
   The fourth parameter is nonzero if this is just a placeholder for an
   FDE that we are omitting. */

void
darwin_emit_unwind_label (FILE *file, tree decl, int for_eh, int empty)
{
  char *lab;

  if (! for_eh)
    return;

  lab = concat (IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (decl)), ".eh", NULL);

  if (TREE_PUBLIC (decl))
    {
      targetm.asm_out.globalize_label (file, lab);
      if (DECL_VISIBILITY (decl) == VISIBILITY_HIDDEN)
        {
          fputs ("\t.private_extern ", file);
          assemble_name (file, lab);
          fputc ('\n', file);
        }
    }

  if (DECL_WEAK (decl))
    {
      fputs ("\t.weak_definition ", file);
      assemble_name (file, lab);
      fputc ('\n', file);
    }

  assemble_name (file, lab);
  if (empty)
    {
      fputs (" = 0\n", file);

      /* Mark the absolute .eh and .eh1 style labels as needed to
         ensure that we don't dead code strip them and keep such
         labels from another instantiation point until we can fix this
         properly with group comdat support.  */
      darwin_mark_decl_preserved (lab);
    }
  else
    fputs (":\n", file);

  free (lab);
}

static GTY(()) unsigned long except_table_label_num;

void
darwin_emit_except_table_label (FILE *file)
{
  char section_start_label[30];

  ASM_GENERATE_INTERNAL_LABEL (section_start_label, "GCC_except_table",
                               except_table_label_num++);
  ASM_OUTPUT_LABEL (file, section_start_label);
}
/* Generate a PC-relative reference to a Mach-O non-lazy-symbol.  */

void
darwin_non_lazy_pcrel (FILE *file, rtx addr)
{
  const char *nlp_name;

  gcc_assert (GET_CODE (addr) == SYMBOL_REF);

  nlp_name = machopic_indirection_name (addr, /*stub_p=*/false);
  fputs ("\t.long\t", file);
  ASM_OUTPUT_LABELREF (file, nlp_name);
  fputs ("-.", file);
}

/* If this is uncommented, details of each allocation will be printed
   in the asm right before the actual code.  WARNING - this will cause some
   test-suite fails (since the printout will contain items that some tests
   are not expecting) -- so don't leave it on by default (it bloats the
   asm too).  */
/*#define DEBUG_DARWIN_MEM_ALLOCATORS*/

/* The first two of these routines are ostensibly just intended to put
   names into the asm.  However, they are both hijacked in order to ensure
   that zero-sized items do not make their way into the output.  Consequently,
   we also need to make these participate in provisions for dealing with
   such items in section anchors.  */

/* The implementation of ASM_DECLARE_OBJECT_NAME.  */
/* The RTTI data (e.g., __ti4name) is common and public (and static),
   but it does need to be referenced via indirect PIC data pointers.
   The machopic_define_symbol calls are telling the machopic subsystem
   that the name *is* defined in this module, so it doesn't need to
   make them indirect.  */
void 
darwin_asm_declare_object_name (FILE *file, 
                                const char *nam, tree decl)
{
  const char *xname = nam;
  unsigned HOST_WIDE_INT size;
  bool local_def, weak;

  weak = (DECL_P (decl)
          && DECL_WEAK (decl)
          && !lookup_attribute ("weak_import", 
                                 DECL_ATTRIBUTES (decl)));

  local_def = DECL_INITIAL (decl) || (TREE_STATIC (decl) 
                                      && (!DECL_COMMON (decl) 
                                          || !TREE_PUBLIC (decl)));

  if (GET_CODE (XEXP (DECL_RTL (decl), 0)) != SYMBOL_REF)
    xname = IDENTIFIER_POINTER (DECL_NAME (decl));

  if (local_def)
    {
      (* targetm.encode_section_info) (decl, DECL_RTL (decl), false);
      if (!weak)
        machopic_define_symbol (DECL_RTL (decl));
    }

  size = tree_low_cst (DECL_SIZE_UNIT (decl), 1);

#ifdef DEBUG_DARWIN_MEM_ALLOCATORS
fprintf (file, "# dadon: %s %s (%llu, %u) local %d weak %d"
               " stat %d com %d pub %d t-const %d t-ro %d init %lx\n",
        xname, (TREE_CODE (decl) == VAR_DECL?"var":"const"), 
        (unsigned long long)size, DECL_ALIGN (decl), local_def, 
        DECL_WEAK (decl), TREE_STATIC (decl), DECL_COMMON (decl),
        TREE_PUBLIC (decl), TREE_CONSTANT (decl), TREE_READONLY (decl),
        (unsigned long)DECL_INITIAL (decl)); 
#endif

  /* Darwin needs help to support local zero-sized objects. 
     They must be made at least one byte, and the section containing must be
     marked as unsuitable for section-anchors (see storage allocators below).
     
     For non-zero objects this output is handled by varasm.c.
  */
  if (!size)
    {
      unsigned int l2align = 0;

      /* The align must be honored, even for zero-sized.  */
      if (DECL_ALIGN (decl))
        {
          l2align = floor_log2 (DECL_ALIGN (decl) / BITS_PER_UNIT);
          fprintf (file, "\t.align\t%u\n", l2align);
        }

      ASM_OUTPUT_LABEL (file, xname);
      size = 1;
      fprintf (file, "\t.space\t"HOST_WIDE_INT_PRINT_UNSIGNED"\n", size);

      /* Check that we've correctly picked up the zero-sized item and placed it
         properly.  */
      gcc_assert ((!DARWIN_SECTION_ANCHORS || !flag_section_anchors)
                  || (in_section 
                      && (in_section->common.flags & SECTION_NO_ANCHOR)));
    }
  else
    ASM_OUTPUT_LABEL (file, xname);
}

/* The implementation of ASM_DECLARE_CONSTANT_NAME.  */
void
darwin_asm_declare_constant_name (FILE *file, const char *name,
                                  const_tree exp ATTRIBUTE_UNUSED,
                                  HOST_WIDE_INT size)
{
  assemble_label (file, name);
  /* As for other items, we need at least one byte.  */
  if (!size)
    {
      fputs ("\t.space\t1\n", file);
      /* Check that we've correctly picked up the zero-sized item and placed it
         properly.  */
      gcc_assert ((!DARWIN_SECTION_ANCHORS || !flag_section_anchors)
                  || (in_section 
                      && (in_section->common.flags & SECTION_NO_ANCHOR)));
    }
}

/* Darwin storage allocators.

   Zerofill sections are desirable for large blank data since, otherwise, these
   data bloat objects (PR33210).

   However, section anchors don't work in .zerofill sections (one cannot switch
   to a zerofill section).  Ergo, for Darwin targets using section anchors we need
   to put (at least some) data into 'normal' switchable sections.

   Here we set a relatively arbitrary value for the size of an object to trigger
   zerofill when section anchors are enabled (anything bigger than a page for
   current Darwin implementations).  FIXME: there ought to be some objective way
   to make this choice.

   When section anchor are off this is ignored anyway.  */

#define BYTES_ZFILL 4096

/* Emit a chunk of data for items coalesced by the linker.  */
static void
darwin_emit_weak_or_comdat (FILE *fp, tree decl, const char *name,
                                  unsigned HOST_WIDE_INT size, 
                                  unsigned int align)
{
  /* Since the sections used here are coalesed, they will not be eligible
     for section anchors, and therefore we don't need to break that out.  */
 if (TREE_READONLY (decl) || TREE_CONSTANT (decl))
    switch_to_section (darwin_sections[const_data_coal_section]);
  else
    switch_to_section (darwin_sections[data_coal_section]);

  /* To be consistent, we'll allow darwin_asm_declare_object_name to assemble
     the align info for zero-sized items... but do it here otherwise.  */
  if (size && align)
    fprintf (fp, "\t.align\t%d\n", floor_log2 (align / BITS_PER_UNIT));

  if (TREE_PUBLIC (decl))
    darwin_globalize_label (fp, name);

  /* ... and we let it deal with outputting one byte of zero for them too.  */ 
  darwin_asm_declare_object_name (fp, name, decl);
  if (size)
    assemble_zeros (size);
}

/* This routine emits 'local' storage:

   When Section Anchors are off this routine emits .zerofill commands in 
   sections named for their alignment.

   When Section Anchors are on, smaller (non-zero-sized) items are placed in
   the .static_data section so that the section anchoring system can see them.
   Larger items are still placed in .zerofill sections, addressing PR33210.
   The routine has no checking - it is all assumed to be done by the caller.
*/
static void
darwin_emit_local_bss (FILE *fp, tree decl, const char *name, 
                        unsigned HOST_WIDE_INT size, 
                        unsigned int l2align)
{
   /* FIXME: We have a fudge to make this work with Java even when the target does
   not use sections anchors -- Java seems to need at least one small item in a
   non-zerofill segment.   */
   if ((DARWIN_SECTION_ANCHORS && flag_section_anchors && size < BYTES_ZFILL)
       || (size && size <= 2))
    {
      /* Put smaller objects in _static_data, where the section anchors system
         can get them.
         However, if they are zero-sized punt them to yet a different section
         (that is not allowed to participate in anchoring).  */
      if (!size)
        {
          fputs ("\t.section\t__DATA,__zobj_bss\n", fp);
          in_section = darwin_sections[zobj_bss_section];
          size = 1;
        }
      else
        {
          fputs ("\t.static_data\n", fp);
          in_section = darwin_sections[static_data_section];
        }

      if (l2align)
        fprintf (fp, "\t.align\t%u\n", l2align);

      assemble_name (fp, name);        
      fprintf (fp, ":\n\t.space\t"HOST_WIDE_INT_PRINT_UNSIGNED"\n", size);
    }
  else 
    {
      /* When we are on a non-section anchor target, we can get zero-sized
         items here.  However, all we need to do is to bump them to one byte
         and the section alignment will take care of the rest.  */
      char secnam[64];
      unsigned int flags ;
      snprintf (secnam, 64, "__DATA,__%sbss%u", ((size)?"":"zo_"), 
                                                (unsigned) l2align);
      /* We can't anchor (yet, if ever) in zerofill sections, because we can't
         switch to them and emit a label.  */
      flags = SECTION_BSS|SECTION_WRITE|SECTION_NO_ANCHOR;
      in_section = get_section (secnam, flags, NULL);
      fprintf (fp, "\t.zerofill %s,", secnam);
      assemble_name (fp, name);
      if (!size)
        size = 1;

      if (l2align)
        fprintf (fp, ","HOST_WIDE_INT_PRINT_UNSIGNED",%u\n",
                 size, (unsigned) l2align);
      else
        fprintf (fp, ","HOST_WIDE_INT_PRINT_UNSIGNED"\n", size);
    }

  (*targetm.encode_section_info) (decl, DECL_RTL (decl), false);
  /* This is defined as a file-scope var, so we know to notify machopic.  */
  machopic_define_symbol (DECL_RTL (decl));
}

/* Emit a chunk of common.  */
static void
darwin_emit_common (FILE *fp, const char *name,
                    unsigned HOST_WIDE_INT size, unsigned int align) 
{
  unsigned HOST_WIDE_INT rounded;
  unsigned int l2align;

  /* Earlier systems complain if the alignment exceeds the page size. 
     The magic number is 4096 * 8 - hard-coded for legacy systems.  */
  if (!emit_aligned_common && (align > 32768UL))
    align = 4096UL; /* In units.  */
  else
    align /= BITS_PER_UNIT;

  /* Make sure we have a meaningful align.  */
  if (!align)
    align = 1;

  /* For earlier toolchains, we need to emit the var as a rounded size to 
     tell ld the alignment.  */
  if (size < align) 
    rounded = align;
  else
    rounded = (size + (align-1)) & ~(align-1);

  l2align = floor_log2 (align);
  gcc_assert (l2align <= L2_MAX_OFILE_ALIGNMENT);

  in_section = comm_section;
  /* We mustn't allow multiple public symbols to share an address when using
     the normal OSX toolchain.  */
  if (!size)
    {
      /* Put at least one byte.  */
      size = 1;
      /* This section can no longer participate in section anchoring.  */
      comm_section->common.flags |= SECTION_NO_ANCHOR;
    }

  fputs ("\t.comm\t", fp);
  assemble_name (fp, name);
  fprintf (fp, "," HOST_WIDE_INT_PRINT_UNSIGNED, 
           emit_aligned_common?size:rounded);
  if (l2align && emit_aligned_common)
    fprintf (fp, ",%u", l2align);
  fputs ("\n", fp);
}

/* Output a var which is all zero - into aligned BSS sections, common, lcomm
   or coalescable data sections (for weak or comdat) as appropriate.  */

void
darwin_output_aligned_bss (FILE *fp, tree decl, const char *name,
                          unsigned HOST_WIDE_INT size, unsigned int align)
{
  unsigned int l2align;
  bool one, pub, weak;

  pub = TREE_PUBLIC (decl);
  one = DECL_ONE_ONLY (decl);
  weak = (DECL_P (decl)
          && DECL_WEAK (decl)
          && !lookup_attribute ("weak_import", 
                                 DECL_ATTRIBUTES (decl)));

#ifdef DEBUG_DARWIN_MEM_ALLOCATORS
fprintf (fp, "# albss: %s (%lld,%d) ro %d cst %d stat %d com %d"
             " pub %d weak %d one %d init %lx\n",
        name, (long long)size, (int)align, TREE_READONLY (decl), 
        TREE_CONSTANT (decl), TREE_STATIC (decl), DECL_COMMON (decl),
        pub, weak, one, (unsigned long)DECL_INITIAL (decl)); 
#endif

  /* Check that any initializer is valid.  */
  gcc_assert ((DECL_INITIAL (decl) == NULL) 
               || (DECL_INITIAL (decl) == error_mark_node) 
               || initializer_zerop (DECL_INITIAL (decl)));

  gcc_assert (DECL_SECTION_NAME (decl) == NULL);
  gcc_assert (!DECL_COMMON (decl));

  /*  Pick up the correct alignment.  */
  if (!size || !align)
    align = DECL_ALIGN (decl);

  l2align = floor_log2 (align / BITS_PER_UNIT);
  gcc_assert (l2align <= L2_MAX_OFILE_ALIGNMENT);
  
  last_assemble_variable_decl = decl;

  /* We would rather not have to check this here - but it seems that we might
     be passed a decl that should be in coalesced space.  */
  if (one || weak)
    {
      /* Weak or COMDAT objects are put in mergeable sections.  */
      darwin_emit_weak_or_comdat (fp, decl, name, size, 
                                        DECL_ALIGN (decl));
      return;
    } 

  /* If this is not public, then emit according to local rules.  */
  if (!pub)
    {
      darwin_emit_local_bss (fp, decl, name, size, l2align);    
      return;
    }

  /* So we have a public symbol (small item fudge for Java, see above).  */
  if ((DARWIN_SECTION_ANCHORS && flag_section_anchors && size < BYTES_ZFILL) 
       || (size && size <= 2))
    {
      /* Put smaller objects in data, where the section anchors system can get
         them.  However, if they are zero-sized punt them to yet a different 
         section (that is not allowed to participate in anchoring).  */
      if (!size)
        {
          fputs ("\t.section\t__DATA,__zobj_data\n", fp);
          in_section = darwin_sections[zobj_data_section];
          size = 1;
        }
      else
        {
          fputs ("\t.data\n", fp);
          in_section = data_section;
        }

      if (l2align)
        fprintf (fp, "\t.align\t%u\n", l2align);

      assemble_name (fp, name);
      fprintf (fp, ":\n\t.space\t"HOST_WIDE_INT_PRINT_UNSIGNED"\n", size);
    }
  else 
    {
      char secnam[64];
      unsigned int flags ;
      /* When we are on a non-section anchor target, we can get zero-sized
         items here.  However, all we need to do is to bump them to one byte
         and the section alignment will take care of the rest.  */
      snprintf (secnam, 64, "__DATA,__%spu_bss%u", ((size)?"":"zo_"), l2align);

      /* We can't anchor in zerofill sections, because we can't switch
         to them and emit a label.  */
      flags = SECTION_BSS|SECTION_WRITE|SECTION_NO_ANCHOR;
      in_section = get_section (secnam, flags, NULL);
      fprintf (fp, "\t.zerofill %s,", secnam);
      assemble_name (fp, name);
      if (!size)
        size = 1;

      if (l2align)
        fprintf (fp, ","HOST_WIDE_INT_PRINT_UNSIGNED",%u\n", size, l2align);
      else
        fprintf (fp, ","HOST_WIDE_INT_PRINT_UNSIGNED"\n", size);
    }
  (* targetm.encode_section_info) (decl, DECL_RTL (decl), false);
}

/* Output a chunk of common, with alignment specified (where the target
   supports this).  */
void
darwin_asm_output_aligned_decl_common (FILE *fp, tree decl, const char *name,
                                       unsigned HOST_WIDE_INT size, 
                                       unsigned int align)
{
  unsigned int l2align;
  bool one, weak;
  /* No corresponding var.  */
  if (decl==NULL)
    {
#ifdef DEBUG_DARWIN_MEM_ALLOCATORS
fprintf (fp, "# adcom: %s (%d,%d) decl=0x0\n", name, (int)size, (int)align); 
#endif
      darwin_emit_common (fp, name, size, align);
      return;
    }

  one = DECL_ONE_ONLY (decl);
  weak = (DECL_P (decl)
          && DECL_WEAK (decl)
          && !lookup_attribute ("weak_import", 
                                 DECL_ATTRIBUTES (decl)));

#ifdef DEBUG_DARWIN_MEM_ALLOCATORS
fprintf (fp, "# adcom: %s (%lld,%d) ro %d cst %d stat %d com %d pub %d"
             " weak %d one %d init %lx\n",
        name,  (long long)size, (int)align, TREE_READONLY (decl), 
        TREE_CONSTANT (decl), TREE_STATIC (decl), DECL_COMMON (decl),
        TREE_PUBLIC (decl), weak, one, (unsigned long)DECL_INITIAL (decl)); 
#endif

  /* We shouldn't be messing with this if the decl has a section name.  */
  gcc_assert (DECL_SECTION_NAME (decl) == NULL);

  /* We would rather not have to check this here - but it seems that we might
     be passed a decl that should be in coalesced space.  */
  if (one || weak)
    {
      /* Weak or COMDAT objects are put in mergable sections.  */
      darwin_emit_weak_or_comdat (fp, decl, name, size, 
                                        DECL_ALIGN (decl));
      return;
    } 

  /* We should only get here for DECL_COMMON, with a zero init (and, in 
     principle, only for public symbols too - although we deal with local
     ones below).  */

  /* Check the initializer is OK.  */
  gcc_assert (DECL_COMMON (decl) 
              && ((DECL_INITIAL (decl) == NULL) 
               || (DECL_INITIAL (decl) == error_mark_node) 
               || initializer_zerop (DECL_INITIAL (decl))));

  last_assemble_variable_decl = decl;

  if (!size || !align) 
    align = DECL_ALIGN (decl);

  l2align = floor_log2 (align / BITS_PER_UNIT);
  /* Check we aren't asking for more aligment than the platform allows.  */
  gcc_assert (l2align <= L2_MAX_OFILE_ALIGNMENT);

  if (TREE_PUBLIC (decl) != 0)
    darwin_emit_common (fp, name, size, align);
  else
    darwin_emit_local_bss (fp, decl, name, size, l2align);      
}

/* Output a chunk of BSS with alignment specfied.  */
void
darwin_asm_output_aligned_decl_local (FILE *fp, tree decl, const char *name, 
                                      unsigned HOST_WIDE_INT size, 
                                      unsigned int align)
{
  unsigned long l2align;
  bool one, weak;

  one = DECL_ONE_ONLY (decl);
  weak = (DECL_P (decl)
          && DECL_WEAK (decl)
          && !lookup_attribute ("weak_import", 
                                 DECL_ATTRIBUTES (decl)));

#ifdef DEBUG_DARWIN_MEM_ALLOCATORS
fprintf (fp, "# adloc: %s (%lld,%d) ro %d cst %d stat %d one %d pub %d"
             " weak %d init %lx\n",
        name, (long long)size, (int)align, TREE_READONLY (decl), 
        TREE_CONSTANT (decl), TREE_STATIC (decl), one, TREE_PUBLIC (decl),
        weak , (unsigned long)DECL_INITIAL (decl)); 
#endif

  /* We shouldn't be messing with this if the decl has a section name.  */
  gcc_assert (DECL_SECTION_NAME (decl) == NULL);

  /* We would rather not have to check this here - but it seems that we might
     be passed a decl that should be in coalesced space.  */
  if (one || weak)
    {
      /* Weak or COMDAT objects are put in mergable sections.  */
      darwin_emit_weak_or_comdat (fp, decl, name, size, 
                                        DECL_ALIGN (decl));
      return;
    } 

  /* .. and it should be suitable for placement in local mem.  */
  gcc_assert(!TREE_PUBLIC (decl) && !DECL_COMMON (decl));
  /* .. and any initializer must be all-zero.  */
  gcc_assert ((DECL_INITIAL (decl) == NULL) 
               || (DECL_INITIAL (decl) == error_mark_node) 
               || initializer_zerop (DECL_INITIAL (decl)));

  last_assemble_variable_decl = decl;

  if (!size || !align)
    align = DECL_ALIGN (decl);

  l2align = floor_log2 (align / BITS_PER_UNIT);
  gcc_assert (l2align <= L2_MAX_OFILE_ALIGNMENT);

  darwin_emit_local_bss (fp, decl, name, size, l2align);
}

/* Emit an assembler directive to set visibility for a symbol.  The
   only supported visibilities are VISIBILITY_DEFAULT and
   VISIBILITY_HIDDEN; the latter corresponds to Darwin's "private
   extern".  There is no MACH-O equivalent of ELF's
   VISIBILITY_INTERNAL or VISIBILITY_PROTECTED. */

void
darwin_assemble_visibility (tree decl, int vis)
{
  if (vis == VISIBILITY_DEFAULT)
    ;
  else if (vis == VISIBILITY_HIDDEN)
    {
      fputs ("\t.private_extern ", asm_out_file);
      assemble_name (asm_out_file,
                     (IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (decl))));
      fputs ("\n", asm_out_file);
    }
  else
    warning (OPT_Wattributes, "internal and protected visibility attributes "
             "not supported in this configuration; ignored");
}

/* VEC Used by darwin_asm_dwarf_section.
   Maybe a hash tab would be better here - but the intention is that this is
   a very short list (fewer than 16 items) and each entry should (ideally, 
   eventually) only be presented once.

   A structure to hold a dwarf debug section used entry.  */

typedef struct GTY(()) dwarf_sect_used_entry {
  const char *name;
  unsigned count;
}
dwarf_sect_used_entry;

DEF_VEC_O(dwarf_sect_used_entry);
DEF_VEC_ALLOC_O(dwarf_sect_used_entry, gc);

/* A list of used __DWARF sections.  */
static GTY (()) VEC (dwarf_sect_used_entry, gc) * dwarf_sect_names_table;

/* This is called when we are asked to assemble a named section and the 
   name begins with __DWARF,.  We keep a list of the section names (without
   the __DWARF, prefix) and use this to emit our required start label on the
   first switch to each section.  */

static void
darwin_asm_dwarf_section (const char *name, unsigned int flags,
                          tree ARG_UNUSED (decl))
{
  unsigned i;
  int namelen;
  const char * sname;
  dwarf_sect_used_entry *ref;
  bool found = false;
  gcc_assert ((flags & (SECTION_DEBUG | SECTION_NAMED))
                    == (SECTION_DEBUG | SECTION_NAMED));
  /* We know that the name starts with __DWARF,  */
  sname = name + 8;
  namelen = strchr (sname, ',') - sname;
  gcc_assert (namelen);
  if (dwarf_sect_names_table == NULL)
    dwarf_sect_names_table = VEC_alloc (dwarf_sect_used_entry, gc, 16);
  else
    for (i = 0; 
         VEC_iterate (dwarf_sect_used_entry, dwarf_sect_names_table, i, ref);
         i++)
      {
        if (!ref)
          break;
        if (!strcmp (ref->name, sname))
          {
            found = true;
            ref->count++;
            break;
          }
      }

  fprintf (asm_out_file, "\t.section %s\n", name);
  if (!found)
    {
      dwarf_sect_used_entry e;
      fprintf (asm_out_file, "Lsection%.*s:\n", namelen, sname);
      e.count = 1;
      e.name = xstrdup (sname);
      VEC_safe_push (dwarf_sect_used_entry, gc, dwarf_sect_names_table, &e);
    }
}

/* Output a difference of two labels that will be an assembly time
   constant if the two labels are local.  (.long lab1-lab2 will be
   very different if lab1 is at the boundary between two sections; it
   will be relocated according to the second section, not the first,
   so one ends up with a difference between labels in different
   sections, which is bad in the dwarf2 eh context for instance.)  */

static int darwin_dwarf_label_counter;

void
darwin_asm_output_dwarf_delta (FILE *file, int size,
                               const char *lab1, const char *lab2)
{
  int islocaldiff = (lab1[0] == '*' && lab1[1] == 'L'
                     && lab2[0] == '*' && lab2[1] == 'L');
  const char *directive = (size == 8 ? ".quad" : ".long");

  if (islocaldiff)
    fprintf (file, "\t.set L$set$%d,", darwin_dwarf_label_counter);
  else
    fprintf (file, "\t%s\t", directive);

  assemble_name_raw (file, lab1);
  fprintf (file, "-");
  assemble_name_raw (file, lab2);
  if (islocaldiff)
    fprintf (file, "\n\t%s L$set$%d", directive, darwin_dwarf_label_counter++);
}

/* Output an offset in a DWARF section on Darwin.  On Darwin, DWARF section
   offsets are not represented using relocs in .o files; either the
   section never leaves the .o file, or the linker or other tool is
   responsible for parsing the DWARF and updating the offsets.  */

void
darwin_asm_output_dwarf_offset (FILE *file, int size, const char * lab,
                                section *base)
{
  char sname[64];
  int namelen;

  gcc_assert (base->common.flags & SECTION_NAMED);
  gcc_assert (strncmp (base->named.name, "__DWARF,", 8) == 0);
  gcc_assert (strchr (base->named.name + 8, ','));

  namelen = strchr (base->named.name + 8, ',') - (base->named.name + 8);
  sprintf (sname, "*Lsection%.*s", namelen, base->named.name + 8);
  darwin_asm_output_dwarf_delta (file, size, lab, sname);
}

/* Called from the within the TARGET_ASM_FILE_START for each target. 
  Initialize the stuff we need for LTO long section names support.  */

void
darwin_file_start (void)
{
  /* We fill this obstack with the complete section text for the lto section
     names to write in darwin_file_end.  */
  obstack_init (&lto_section_names_obstack);
  lto_section_names_offset = 0;
}

/* Called for the TARGET_ASM_FILE_END hook.
   Emit the mach-o pic indirection data, the lto data and, finally a flag
   to tell the linker that it can break the file object into sections and
   move those around for efficiency.  */

void
darwin_file_end (void)
{
  const char *lto_section_names;

  machopic_finish (asm_out_file);
  if (strcmp (lang_hooks.name, "GNU C++") == 0)
    {
      switch_to_section (darwin_sections[constructor_section]);
      switch_to_section (darwin_sections[destructor_section]);
      ASM_OUTPUT_ALIGN (asm_out_file, 1);
    }

  /* If there was LTO assembler output, append it to asm_out_file.  */
  if (lto_asm_out_name)
    {
      int n;
      char *buf, *lto_asm_txt;

      /* Shouldn't be here if we failed to switch back.  */
      gcc_assert (! saved_asm_out_file);

      lto_asm_out_file = fopen (lto_asm_out_name, "r");
      if (lto_asm_out_file == NULL)
        fatal_error ("failed to open temporary file %s with LTO output",
                     lto_asm_out_name);
      fseek (lto_asm_out_file, 0, SEEK_END);
      n = ftell (lto_asm_out_file);
      if (n > 0)
        {
          fseek (lto_asm_out_file, 0, SEEK_SET);
          lto_asm_txt = buf = (char *) xmalloc (n + 1);
          while (fgets (lto_asm_txt, n, lto_asm_out_file))
            fputs (lto_asm_txt, asm_out_file);
        }

      /* Remove the temporary file.  */
      fclose (lto_asm_out_file);
      unlink_if_ordinary (lto_asm_out_name);
      free (lto_asm_out_name);
    }

  /* Finish the LTO section names obstack.  Don't output anything if
     there are no recorded section names.  */
  obstack_1grow (&lto_section_names_obstack, '\0');
  lto_section_names = XOBFINISH (&lto_section_names_obstack, const char *);
  if (strlen (lto_section_names) > 0)
    {
      fprintf (asm_out_file,
               "\t.section %s,%s,regular,debug\n",
               LTO_SEGMENT_NAME, LTO_NAMES_SECTION);
      fprintf (asm_out_file,
               "\t# Section names in %s are offsets into this table\n",
               LTO_SEGMENT_NAME);
      fprintf (asm_out_file, "%s\n", lto_section_names);
    }
  obstack_free (&lto_section_names_obstack, NULL);

  /* If we have section anchors, then we must prevent the linker from
     re-arranging data.  */
  if (!DARWIN_SECTION_ANCHORS || !flag_section_anchors)
    fprintf (asm_out_file, "\t.subsections_via_symbols\n");
}

/* TODO: Add a language hook for identifying if a decl is a vtable.  */
#define DARWIN_VTABLE_P(DECL) 0

/* Cross-module name binding.  Darwin does not support overriding
   functions at dynamic-link time, except for vtables in kexts.  */

bool
darwin_binds_local_p (const_tree decl)
{
  return default_binds_local_p_1 (decl,
                                  TARGET_KEXTABI && DARWIN_VTABLE_P (decl));
}

/* The Darwin's implementation of TARGET_ASM_OUTPUT_ANCHOR.  Define the
   anchor relative to ".", the current section position.  We cannot use
   the default one because ASM_OUTPUT_DEF is wrong for Darwin.  */
void
darwin_asm_output_anchor (rtx symbol)
{
  fprintf (asm_out_file, "\t.set\t");
  assemble_name (asm_out_file, XSTR (symbol, 0));
  fprintf (asm_out_file, ", . + " HOST_WIDE_INT_PRINT_DEC "\n",
           SYMBOL_REF_BLOCK_OFFSET (symbol));
}

/* Disable section anchoring on any section containing a zero-sized 
   object.  */
bool
darwin_use_anchors_for_symbol_p (const_rtx symbol)
{
  if (DARWIN_SECTION_ANCHORS && flag_section_anchors) 
    {
      section *sect;
      /* If the section contains a zero-sized object it's ineligible.  */
      sect = SYMBOL_REF_BLOCK (symbol)->sect;
      /* This should have the effect of disabling anchors for vars that follow
         any zero-sized one, in a given section.  */     
      if (sect->common.flags & SECTION_NO_ANCHOR)
        return false;

        /* Also check the normal reasons for suppressing.  */
        return default_use_anchors_for_symbol_p (symbol);
    }
  else
    return false;
}

/* Set the darwin specific attributes on TYPE.  */
void
darwin_set_default_type_attributes (tree type)
{
  if (darwin_ms_struct
      && TREE_CODE (type) == RECORD_TYPE)
    TYPE_ATTRIBUTES (type) = tree_cons (get_identifier ("ms_struct"),
                                        NULL_TREE,
                                        TYPE_ATTRIBUTES (type));
}

/* True, iff we're generating code for loadable kernel extensions.  */

bool
darwin_kextabi_p (void) {
  return flag_apple_kext;
}

void
darwin_override_options (void)
{
  bool darwin9plus = (darwin_macosx_version_min
                      && strverscmp (darwin_macosx_version_min, "10.5") >= 0);

  /* Don't emit DWARF3/4 unless specifically selected.  This is a 
     workaround for tool bugs.  */
  if (!global_options_set.x_dwarf_strict) 
    dwarf_strict = 1;

  /* Disable -freorder-blocks-and-partition for darwin_emit_unwind_label.  */
  if (flag_reorder_blocks_and_partition 
      && (targetm.asm_out.emit_unwind_label == darwin_emit_unwind_label))
    {
      inform (input_location,
              "-freorder-blocks-and-partition does not work with exceptions "
              "on this architecture");
      flag_reorder_blocks_and_partition = 0;
      flag_reorder_blocks = 1;
    }

  if (flag_mkernel || flag_apple_kext)
    {
      /* -mkernel implies -fapple-kext for C++ */
      if (strcmp (lang_hooks.name, "GNU C++") == 0)
        flag_apple_kext = 1;

      flag_no_common = 1;

      /* No EH in kexts.  */
      flag_exceptions = 0;
      /* No -fnon-call-exceptions data in kexts.  */
      flag_non_call_exceptions = 0;
      /* so no tables either.. */
      flag_unwind_tables = 0;
      flag_asynchronous_unwind_tables = 0;
      /* We still need to emit branch islands for kernel context.  */
      darwin_emit_branch_islands = true;
    }

  if (flag_var_tracking
      && darwin9plus
      && debug_info_level >= DINFO_LEVEL_NORMAL
      && debug_hooks->var_location != do_nothing_debug_hooks.var_location)
    flag_var_tracking_uninit = 1;

  if (MACHO_DYNAMIC_NO_PIC_P)
    {
      if (flag_pic)
        warning (0, "-mdynamic-no-pic overrides -fpic or -fPIC");
      flag_pic = 0;
    }
  else if (flag_pic == 1)
    {
      /* Darwin's -fpic is -fPIC.  */
      flag_pic = 2;
    }

  /* It is assumed that branch island stubs are needed for earlier systems.  */
  if (!darwin9plus)
    darwin_emit_branch_islands = true;
  else
    emit_aligned_common = true; /* Later systems can support aligned common.  */

  /* The c_dialect...() macros are not available to us here.  */
  darwin_running_cxx = (strstr (lang_hooks.name, "C++") != 0);
}

/* Add $LDBL128 suffix to long double builtins.  */

static void
darwin_patch_builtin (int fncode)
{
  tree fn = built_in_decls[fncode];
  tree sym;
  char *newname;

  if (!fn)
    return;

  sym = DECL_ASSEMBLER_NAME (fn);
  newname = ACONCAT (("_", IDENTIFIER_POINTER (sym), "$LDBL128", NULL));

  set_user_assembler_name (fn, newname);

  fn = implicit_built_in_decls[fncode];
  if (fn)
    set_user_assembler_name (fn, newname);
}

void
darwin_patch_builtins (void)
{
  if (LONG_DOUBLE_TYPE_SIZE != 128)
    return;

#define PATCH_BUILTIN(fncode) darwin_patch_builtin (fncode);
#define PATCH_BUILTIN_NO64(fncode)              \
  if (!TARGET_64BIT)                            \
    darwin_patch_builtin (fncode);
#define PATCH_BUILTIN_VARIADIC(fncode)                            \
  if (!TARGET_64BIT                                               \
      && (strverscmp (darwin_macosx_version_min, "10.3.9") >= 0)) \
    darwin_patch_builtin (fncode);
#include "darwin-ppc-ldouble-patch.def"
#undef PATCH_BUILTIN
#undef PATCH_BUILTIN_NO64
#undef PATCH_BUILTIN_VARIADIC
}

/*  CFStrings implementation.  */
static GTY(()) tree cfstring_class_reference = NULL_TREE;
static GTY(()) tree cfstring_type_node = NULL_TREE;
static GTY(()) tree ccfstring_type_node = NULL_TREE;
static GTY(()) tree pccfstring_type_node = NULL_TREE;
static GTY(()) tree pcint_type_node = NULL_TREE;
static GTY(()) tree pcchar_type_node = NULL_TREE;

static enum built_in_function DARWIN_BUILTIN_CFSTRINGMAKECONSTANTSTRING;

/* Store all constructed constant CFStrings in a hash table so that
   they get uniqued properly.  */

typedef struct GTY (()) cfstring_descriptor {
  /* The string literal.  */
  tree literal;
  /* The resulting constant CFString.  */
  tree constructor;
} cfstring_descriptor;

static GTY ((param_is (struct cfstring_descriptor))) htab_t cfstring_htab;

static hashval_t cfstring_hash (const void *);
static int cfstring_eq (const void *, const void *);

static tree
add_builtin_field_decl (tree type, const char *name, tree **chain)
{
  tree field = build_decl (BUILTINS_LOCATION, FIELD_DECL, 
                            get_identifier (name), type);

  if (*chain != NULL)
    **chain = field;
  *chain = &DECL_CHAIN (field);

  return field;
}

void
darwin_init_cfstring_builtins (unsigned first_avail)
{
  tree cfsfun, fields, pccfstring_ftype_pcchar;
  tree *chain = NULL;

  DARWIN_BUILTIN_CFSTRINGMAKECONSTANTSTRING = 
                        (enum built_in_function) first_avail;
  
  /* struct __builtin_CFString {
       const int *isa;          (will point at
       int flags;                __CFConstantStringClassReference)
       const char *str;
       long length;
     };  */

  pcint_type_node = build_pointer_type 
                   (build_qualified_type (integer_type_node, TYPE_QUAL_CONST));

  pcchar_type_node = build_pointer_type 
                   (build_qualified_type (char_type_node, TYPE_QUAL_CONST));

  cfstring_type_node = (*lang_hooks.types.make_type) (RECORD_TYPE);

  /* Have to build backwards for finish struct.  */
  fields = add_builtin_field_decl (long_integer_type_node, "length", &chain);
  add_builtin_field_decl (pcchar_type_node, "str", &chain);
  add_builtin_field_decl (integer_type_node, "flags", &chain);
  add_builtin_field_decl (pcint_type_node, "isa", &chain);
  finish_builtin_struct (cfstring_type_node, "__builtin_CFString",
                         fields, NULL_TREE);

  /* const struct __builtin_CFstring *
     __builtin___CFStringMakeConstantString (const char *); */

  ccfstring_type_node = build_qualified_type 
                        (cfstring_type_node, TYPE_QUAL_CONST);
  pccfstring_type_node = build_pointer_type (ccfstring_type_node);
  pccfstring_ftype_pcchar = build_function_type_list 
                        (pccfstring_type_node, pcchar_type_node, NULL_TREE);

  cfsfun  = build_decl (BUILTINS_LOCATION, FUNCTION_DECL, 
                        get_identifier ("__builtin___CFStringMakeConstantString"),
                        pccfstring_ftype_pcchar);

  TREE_PUBLIC (cfsfun) = 1;
  DECL_EXTERNAL (cfsfun) = 1;
  DECL_ARTIFICIAL (cfsfun) = 1;
  /* Make a lang-specific section - dup_lang_specific_decl makes a new node
     in place of the existing, which may be NULL.  */
  DECL_LANG_SPECIFIC (cfsfun) = NULL;
  (*lang_hooks.dup_lang_specific_decl) (cfsfun);
  DECL_BUILT_IN_CLASS (cfsfun) = BUILT_IN_MD;
  DECL_FUNCTION_CODE (cfsfun) = DARWIN_BUILTIN_CFSTRINGMAKECONSTANTSTRING;
  lang_hooks.builtin_function (cfsfun);

  /* extern int __CFConstantStringClassReference[];  */
  cfstring_class_reference = build_decl (BUILTINS_LOCATION, VAR_DECL,
                 get_identifier ("__CFConstantStringClassReference"),
                 build_array_type (integer_type_node, NULL_TREE));

  TREE_PUBLIC (cfstring_class_reference) = 1;
  DECL_ARTIFICIAL (cfstring_class_reference) = 1;
  (*lang_hooks.decls.pushdecl) (cfstring_class_reference);
  DECL_EXTERNAL (cfstring_class_reference) = 1;
  rest_of_decl_compilation (cfstring_class_reference, 0, 0);
  
  /* Initialize the hash table used to hold the constant CFString objects.  */
  cfstring_htab = htab_create_ggc (31, cfstring_hash, cfstring_eq, NULL);
}

tree
darwin_fold_builtin (tree fndecl, int n_args, tree *argp, 
                     bool ARG_UNUSED (ignore))
{
  unsigned int fcode = DECL_FUNCTION_CODE (fndecl);
  
  if (fcode == DARWIN_BUILTIN_CFSTRINGMAKECONSTANTSTRING)
    {
      if (!darwin_constant_cfstrings)
        {
          error ("built-in function %qD requires the" 
                 " %<-mconstant-cfstrings%> flag", fndecl);
          return error_mark_node;
        }

      if (n_args != 1)
        {
          error ("built-in function %qD takes one argument only", fndecl);
          return error_mark_node;
        }

      return darwin_build_constant_cfstring (*argp);
    }

  return NULL_TREE;
}

static hashval_t
cfstring_hash (const void *ptr)
{
  tree str = ((const struct cfstring_descriptor *)ptr)->literal;
  const unsigned char *p = (const unsigned char *) TREE_STRING_POINTER (str);
  int i, len = TREE_STRING_LENGTH (str);
  hashval_t h = len;

  for (i = 0; i < len; i++)
    h = ((h * 613) + p[i]);

  return h;
}

static int
cfstring_eq (const void *ptr1, const void *ptr2)
{
  tree str1 = ((const struct cfstring_descriptor *)ptr1)->literal;
  tree str2 = ((const struct cfstring_descriptor *)ptr2)->literal;
  int len1 = TREE_STRING_LENGTH (str1);

  return (len1 == TREE_STRING_LENGTH (str2)
          && !memcmp (TREE_STRING_POINTER (str1), TREE_STRING_POINTER (str2),
                      len1));
}

tree
darwin_build_constant_cfstring (tree str)
{
  struct cfstring_descriptor *desc, key;
  void **loc;
  tree addr;

  if (!str)
    {
      error ("CFString literal is missing");
      return error_mark_node;
    }

  STRIP_NOPS (str);

  if (TREE_CODE (str) == ADDR_EXPR)
    str = TREE_OPERAND (str, 0);

  if (TREE_CODE (str) != STRING_CST)
    {
      error ("CFString literal expression is not a string constant");
      return error_mark_node;
    }

  /* Perhaps we already constructed a constant CFString just like this one? */
  key.literal = str;
  loc = htab_find_slot (cfstring_htab, &key, INSERT);
  desc = (struct cfstring_descriptor *) *loc;

  if (!desc)
    {
      tree var, constructor, field;
      VEC(constructor_elt,gc) *v = NULL;
      int length = TREE_STRING_LENGTH (str) - 1;

      if (darwin_warn_nonportable_cfstrings)
        {
          const char *s = TREE_STRING_POINTER (str);
          int l = 0;

          for (l = 0; l < length; l++)
            if (!s[l] || !isascii (s[l]))
              {
                warning (darwin_warn_nonportable_cfstrings, "%s in CFString literal",
                         s[l] ? "non-ASCII character" : "embedded NUL");
                break;
              }
        }

      *loc = desc = ggc_alloc_cleared_cfstring_descriptor ();
      desc->literal = str;

      /* isa *. */
      field = TYPE_FIELDS (ccfstring_type_node);
      CONSTRUCTOR_APPEND_ELT(v, NULL_TREE, 
                             build1 (ADDR_EXPR,  TREE_TYPE (field),  
                                     cfstring_class_reference));
      /* flags */
      field = DECL_CHAIN (field);
      CONSTRUCTOR_APPEND_ELT(v, NULL_TREE, 
                             build_int_cst (TREE_TYPE (field), 0x000007c8));
      /* string *. */
      field = DECL_CHAIN (field);
      CONSTRUCTOR_APPEND_ELT(v, NULL_TREE,
                             build1 (ADDR_EXPR, TREE_TYPE (field), str));
      /* length */
      field = DECL_CHAIN (field);
      CONSTRUCTOR_APPEND_ELT(v, NULL_TREE,
                             build_int_cst (TREE_TYPE (field), length));

      constructor = build_constructor (ccfstring_type_node, v);
      TREE_READONLY (constructor) = 1;
      TREE_CONSTANT (constructor) = 1;
      TREE_STATIC (constructor) = 1;

      /* Fromage: The C++ flavor of 'build_unary_op' expects constructor nodes
         to have the TREE_HAS_CONSTRUCTOR (...) bit set.  However, this file is
         being built without any knowledge of C++ tree accessors; hence, we shall
         use the generic accessor that TREE_HAS_CONSTRUCTOR actually maps to!  */
      if (darwin_running_cxx)
        TREE_LANG_FLAG_4 (constructor) = 1;  /* TREE_HAS_CONSTRUCTOR  */

      /* Create an anonymous global variable for this CFString.  */
      var = build_decl (input_location, CONST_DECL, 
                        NULL, TREE_TYPE (constructor));
      DECL_ARTIFICIAL (var) = 1;
      TREE_STATIC (var) = 1;
      DECL_INITIAL (var) = constructor;
      /* FIXME: This should use a translation_unit_decl to indicate file scope.  */
      DECL_CONTEXT (var) = NULL_TREE;
      desc->constructor = var;
    }

  addr = build1 (ADDR_EXPR, pccfstring_type_node, desc->constructor);
  TREE_CONSTANT (addr) = 1;

  return addr;
}

bool
darwin_cfstring_p (tree str)
{
  struct cfstring_descriptor key;
  void **loc;

  if (!str)
    return false;

  STRIP_NOPS (str);

  if (TREE_CODE (str) == ADDR_EXPR)
    str = TREE_OPERAND (str, 0);

  if (TREE_CODE (str) != STRING_CST)
    return false;

  key.literal = str;
  loc = htab_find_slot (cfstring_htab, &key, NO_INSERT);
  
  if (loc)
    return true;

  return false;
}

void
darwin_enter_string_into_cfstring_table (tree str)
{
  struct cfstring_descriptor key;
  void **loc;

  key.literal = str;
  loc = htab_find_slot (cfstring_htab, &key, INSERT);

  if (!*loc)
    {
      *loc = ggc_alloc_cleared_cfstring_descriptor ();
      ((struct cfstring_descriptor *)*loc)->literal = str;
    }
}

/* Choose named function section based on its frequency.  */

section *
darwin_function_section (tree decl, enum node_frequency freq,
                          bool startup, bool exit)
{
  /* Startup code should go to startup subsection unless it is
     unlikely executed (this happens especially with function splitting
     where we can split away unnecesary parts of static constructors.  */
  if (startup && freq != NODE_FREQUENCY_UNLIKELY_EXECUTED)
    return get_named_text_section
             (decl, "__TEXT,__startup,regular,pure_instructions", "_startup");

  /* Similarly for exit.  */
  if (exit && freq != NODE_FREQUENCY_UNLIKELY_EXECUTED)
    return get_named_text_section (decl,
                                   "__TEXT,__exit,regular,pure_instructions",
                                   "_exit");

  /* Group cold functions together, similarly for hot code.  */
  switch (freq)
    {
      case NODE_FREQUENCY_UNLIKELY_EXECUTED:
        return get_named_text_section
                 (decl,
                  "__TEXT,__unlikely,regular,pure_instructions", "_unlikely");
      case NODE_FREQUENCY_HOT:
        return get_named_text_section
                 (decl, "__TEXT,__hot,regular,pure_instructions", "_hot");
      default:
        return NULL;
    }
}

#include "gt-darwin.h"