varasm.c

gcc库的原代码,对编程有很大帮助.

/* Output variables, constants and external declarations, for GNU compiler.
   Copyright (C) 1987, 88, 89, 92, 93, 94, 1995 Free Software Foundation, Inc.

This file is part of GNU CC.

GNU CC 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 2, or (at your option)
any later version.

GNU CC 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 GNU CC; see the file COPYING.  If not, write to
the Free Software Foundation, 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */


/* This file handles generation of all the assembler code
   *except* the instructions of a function.
   This includes declarations of variables and their initial values.

   We also output the assembler code for constants stored in memory
   and are responsible for combining constants with the same value.  */

#include <stdio.h>
#include <setjmp.h>
/* #include <stab.h> */
#include "config.h"
#include "rtl.h"
#include "tree.h"
#include "flags.h"
#include "function.h"
#include "expr.h"
#include "output.h"
#include "hard-reg-set.h"
#include "regs.h"
#include "defaults.h"
#include "real.h"
#include "bytecode.h"

#include "obstack.h"
#include "c-pragma.h"

#ifdef XCOFF_DEBUGGING_INFO
#include "xcoffout.h"
#endif

#include <ctype.h>

#ifndef ASM_STABS_OP
#define ASM_STABS_OP ".stabs"
#endif

/* This macro gets just the user-specified name
   out of the string in a SYMBOL_REF.  On most machines,
   we discard the * if any and that's all.  */
#ifndef STRIP_NAME_ENCODING
#define STRIP_NAME_ENCODING(VAR,SYMBOL_NAME) \
  (VAR) = ((SYMBOL_NAME) + ((SYMBOL_NAME)[0] == '*'))
#endif

/* File in which assembler code is being written.  */

extern FILE *asm_out_file;

/* The (assembler) name of the first globally-visible object output.  */
char *first_global_object_name;

extern struct obstack *current_obstack;
extern struct obstack *saveable_obstack;
extern struct obstack *rtl_obstack;
extern struct obstack permanent_obstack;
#define obstack_chunk_alloc xmalloc

/* Number for making the label on the next
   constant that is stored in memory.  */

int const_labelno;

/* Number for making the label on the next
   static variable internal to a function.  */

int var_labelno;

/* Carry information from ASM_DECLARE_OBJECT_NAME
   to ASM_FINISH_DECLARE_OBJECT.  */

int size_directive_output;

/* The last decl for which assemble_variable was called,
   if it did ASM_DECLARE_OBJECT_NAME.
   If the last call to assemble_variable didn't do that,
   this holds 0.  */

tree last_assemble_variable_decl;


#ifdef HANDLE_PRAGMA_WEAK
/* Any weak symbol declarations waiting to be emitted.  */

struct weak_syms
{
  struct weak_syms *next;
  char *name;
  char *value;
};

static struct weak_syms *weak_decls;
#endif

/* Nonzero if at least one function definition has been seen.  */

static int function_defined;

struct addr_const;
struct constant_descriptor;
struct rtx_const;
struct pool_constant;

static void bc_make_decl_rtl		PROTO((tree, char *, int));
static char *strip_reg_name		PROTO((char *));
static void bc_output_ascii		PROTO((FILE *, char *, int));
static int contains_pointers_p		PROTO((tree));
static void decode_addr_const		PROTO((tree, struct addr_const *));
static int const_hash			PROTO((tree));
static int compare_constant		PROTO((tree,
					       struct constant_descriptor *));
static char *compare_constant_1		PROTO((tree, char *));
static struct constant_descriptor *record_constant PROTO((tree));
static void record_constant_1		PROTO((tree));
static tree copy_constant		PROTO((tree));
static void output_constant_def_contents  PROTO((tree, int, int));
static void decode_rtx_const		PROTO((enum machine_mode, rtx,
					       struct rtx_const *));
static int const_hash_rtx		PROTO((enum machine_mode, rtx));
static int compare_constant_rtx		PROTO((enum machine_mode, rtx,
					       struct constant_descriptor *));
static struct constant_descriptor *record_constant_rtx PROTO((enum machine_mode,
							      rtx));
static struct pool_constant *find_pool_constant PROTO((rtx));
static int output_addressed_constants	PROTO((tree));
static void bc_assemble_integer		PROTO((tree, int));
static void output_constructor		PROTO((tree, int));

#ifdef EXTRA_SECTIONS
static enum in_section {no_section, in_text, in_data, in_named, EXTRA_SECTIONS} in_section
  = no_section;
#else
static enum in_section {no_section, in_text, in_data, in_named} in_section
  = no_section;
#endif

/* Return a non-zero value if DECL has a section attribute.  */
#define IN_NAMED_SECTION(DECL) \
  ((TREE_CODE (DECL) == FUNCTION_DECL || TREE_CODE (DECL) == VAR_DECL) \
   && DECL_SECTION_NAME (DECL) != NULL_TREE)

/* Text of section name when in_section == in_named.  */
static char *in_named_name;

/* Define functions like text_section for any extra sections.  */
#ifdef EXTRA_SECTION_FUNCTIONS
EXTRA_SECTION_FUNCTIONS
#endif

/* Tell assembler to switch to text section.  */

void
text_section ()
{
  if (in_section != in_text)
    {
      if (output_bytecode)
	bc_text ();
      else
	fprintf (asm_out_file, "%s\n", TEXT_SECTION_ASM_OP);

      in_section = in_text;
    }
}

/* Tell assembler to switch to data section.  */

void
data_section ()
{
  if (in_section != in_data)
    {
      if (output_bytecode)
	bc_data ();
      else
	{
	  if (flag_shared_data)
	    {
#ifdef SHARED_SECTION_ASM_OP
	      fprintf (asm_out_file, "%s\n", SHARED_SECTION_ASM_OP);
#else
	      fprintf (asm_out_file, "%s\n", DATA_SECTION_ASM_OP);
#endif
	    }
	  else
	    fprintf (asm_out_file, "%s\n", DATA_SECTION_ASM_OP);
	}

      in_section = in_data;
    }
}

/* Tell assembler to switch to read-only data section.  This is normally
   the text section.  */

void
readonly_data_section ()
{
#ifdef READONLY_DATA_SECTION
  READONLY_DATA_SECTION ();  /* Note this can call data_section.  */
#else
  text_section ();
#endif
}

/* Determine if we're in the text section. */

int
in_text_section ()
{
  return in_section == in_text;
}

/* Tell assembler to change to section NAME for DECL.
   If DECL is NULL, just switch to section NAME.
   If NAME is NULL, get the name from DECL.  */

void
named_section (decl, name)
     tree decl;
     char *name;
{
  if (decl != NULL_TREE
      && (TREE_CODE (decl) != FUNCTION_DECL && TREE_CODE (decl) != VAR_DECL))
    abort ();
  if (name == NULL)
    name = TREE_STRING_POINTER (DECL_SECTION_NAME (decl));

  if (in_section != in_named || strcmp (name, in_named_name))
    {
      in_named_name = name;
      in_section = in_named;
    
#ifdef ASM_OUTPUT_SECTION_NAME
      ASM_OUTPUT_SECTION_NAME (asm_out_file, decl, name);
#else
      /* Section attributes are not supported if this macro isn't provided -
	 some host formats don't support them at all.  The front-end should
	 already have flagged this as an error.  */
      abort ();
#endif
    }
}

/* Switch to the section for function DECL.

   If DECL is NULL_TREE, switch to the text section.
   ??? It's not clear that we will ever be passed NULL_TREE, but it's
   safer to handle it.  */

void
function_section (decl)
     tree decl;
{
  if (decl != NULL_TREE
      && DECL_SECTION_NAME (decl) != NULL_TREE)
    named_section (decl, (char *) 0);
 else
   text_section ();
}

/* Create the rtl to represent a function, for a function definition.
   DECL is a FUNCTION_DECL node which describes which function.
   The rtl is stored into DECL.  */

void
make_function_rtl (decl)
     tree decl;
{
  char *name = IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (decl));

  if (output_bytecode)
    {
      if (DECL_RTL (decl) == 0)
	DECL_RTL (decl) = bc_gen_rtx (name, 0, (struct bc_label *) 0);
      
      /* Record that at least one function has been defined.  */
      function_defined = 1;
      return;
    }

  /* Rename a nested function to avoid conflicts.  */
  if (decl_function_context (decl) != 0
      && DECL_INITIAL (decl) != 0
      && DECL_RTL (decl) == 0)
    {
      char *label;

      name = IDENTIFIER_POINTER (DECL_NAME (decl));
      ASM_FORMAT_PRIVATE_NAME (label, name, var_labelno);
      name = obstack_copy0 (saveable_obstack, label, strlen (label));
      var_labelno++;
    }

  if (DECL_RTL (decl) == 0)
    {
      DECL_RTL (decl)
	= gen_rtx (MEM, DECL_MODE (decl),
		   gen_rtx (SYMBOL_REF, Pmode, name));

      /* Optionally set flags or add text to the name to record information
	 such as that it is a function name.  If the name is changed, the macro
	 ASM_OUTPUT_LABELREF will have to know how to strip this information.  */
#ifdef ENCODE_SECTION_INFO
      ENCODE_SECTION_INFO (decl);
#endif
    }

  /* Record at least one function has been defined.  */
  function_defined = 1;
}

/* Create the DECL_RTL for a declaration for a static or external
   variable or static or external function.
   ASMSPEC, if not 0, is the string which the user specified
   as the assembler symbol name.
   TOP_LEVEL is nonzero if this is a file-scope variable.
   This is never called for PARM_DECLs.  */

static void
bc_make_decl_rtl (decl, asmspec, top_level)
     tree decl;
     char *asmspec;
     int top_level;
{
  register char *name = TREE_STRING_POINTER (DECL_ASSEMBLER_NAME (decl));

  if (DECL_RTL (decl) == 0)
    {
      /* Print an error message for register variables.  */
      if (DECL_REGISTER (decl) && TREE_CODE (decl) == FUNCTION_DECL)
	error ("function declared `register'");
      else if (DECL_REGISTER (decl))
	error ("global register variables not supported in the interpreter");

      /* Handle ordinary static variables and functions.  */
      if (DECL_RTL (decl) == 0)
	{
	  /* Can't use just the variable's own name for a variable
	     whose scope is less than the whole file.
	     Concatenate a distinguishing number.  */
	  if (!top_level && !DECL_EXTERNAL (decl) && asmspec == 0)
	    {
	      char *label;

	      ASM_FORMAT_PRIVATE_NAME (label, name, var_labelno);
	      name = obstack_copy0 (saveable_obstack, label, strlen (label));
	      var_labelno++;
	    }

	  DECL_RTL (decl) = bc_gen_rtx (name, 0, (struct bc_label *) 0);
	}
    }
}

/* Given NAME, a putative register name, discard any customary prefixes.  */

static char *
strip_reg_name (name)
     char *name;
{
#ifdef REGISTER_PREFIX
  if (!strncmp (name, REGISTER_PREFIX, strlen (REGISTER_PREFIX)))
    name += strlen (REGISTER_PREFIX);
#endif
  if (name[0] == '%' || name[0] == '#')
    name++;
  return name;
}

/* Decode an `asm' spec for a declaration as a register name.
   Return the register number, or -1 if nothing specified,
   or -2 if the ASMSPEC is not `cc' or `memory' and is not recognized,
   or -3 if ASMSPEC is `cc' and is not recognized,
   or -4 if ASMSPEC is `memory' and is not recognized.
   Accept an exact spelling or a decimal number.
   Prefixes such as % are optional.  */

int
decode_reg_name (asmspec)
     char *asmspec;
{
  if (asmspec != 0)
    {
      int i;

      /* Get rid of confusing prefixes.  */
      asmspec = strip_reg_name (asmspec);
	
      /* Allow a decimal number as a "register name".  */
      for (i = strlen (asmspec) - 1; i >= 0; i--)
	if (! (asmspec[i] >= '0' && asmspec[i] <= '9'))
	  break;
      if (asmspec[0] != 0 && i < 0)
	{
	  i = atoi (asmspec);
	  if (i < FIRST_PSEUDO_REGISTER && i >= 0)
	    return i;
	  else
	    return -2;
	}

      for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
	if (reg_names[i][0]
	    && ! strcmp (asmspec, strip_reg_name (reg_names[i])))
	  return i;

#ifdef ADDITIONAL_REGISTER_NAMES
      {
	static struct { char *name; int number; } table[]
	  = ADDITIONAL_REGISTER_NAMES;

	for (i = 0; i < sizeof (table) / sizeof (table[0]); i++)
	  if (! strcmp (asmspec, table[i].name))
	    return table[i].number;
      }
#endif /* ADDITIONAL_REGISTER_NAMES */

      if (!strcmp (asmspec, "memory"))
	return -4;

      if (!strcmp (asmspec, "cc"))
	return -3;

      return -2;
    }

  return -1;
}

/* Create the DECL_RTL for a declaration for a static or external variable
   or static or external function.
   ASMSPEC, if not 0, is the string which the user specified
   as the assembler symbol name.
   TOP_LEVEL is nonzero if this is a file-scope variable.

   This is never called for PARM_DECL nodes.  */

void
make_decl_rtl (decl, asmspec, top_level)
     tree decl;
     char *asmspec;
     int top_level;
{
  register char *name = 0;
  int reg_number;

  if (output_bytecode)