final.c

这是完整的gcc源代码

/* Convert RTL to assembler code and output it, for GNU compiler.
   Copyright (C) 1987, 1988, 1989 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 1, 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, 675 Mass Ave, Cambridge, MA 02139, USA.  */


/* This is the final pass of the compiler.
   It looks at the rtl code for a function and outputs assembler code.

   Call `final_start_function' to output the assembler code for function entry,
   `final' to output assembler code for some RTL code,
   `final_end_function' to output assembler code for function exit.
   If a function is compiled in several pieces, each piece is
   output separately with `final'.

   Some optimizations are also done at this level.
   Move instructions that were made unnecessary by good register allocation
   are detected and omitted from the output.  (Though most of these
   are removed by the last jump pass.)

   Instructions to set the condition codes are omitted when it can be
   seen that the condition codes already had the desired values.

   In some cases it is sufficient if the inherited condition codes
   have related values, but this may require the following insn
   (the one that tests the condition codes) to be modified.

   The code for the function prologue and epilogue are generated
   directly as assembler code by the macros FUNCTION_PROLOGUE and
   FUNCTION_EPILOGUE.  Those instructions never exist as rtl.  */

#include <stdio.h>
#include "config.h"
#include "rtl.h"
#include "regs.h"
#include "insn-config.h"
#include "recog.h"
#include "conditions.h"
#include "gdbfiles.h"
#include "flags.h"
#include "real.h"
#include "output.h"

/* Get N_SLINE and N_SOL from stab.h if we can expect the file to exist.  */
#ifdef DBX_DEBUGGING_INFO
#ifdef USG
#include "gstab.h"  /* If doing DBX on sysV, use our own stab.h.  */
#else
#include <stab.h>  /* On BSD, use the system's stab.h.  */
#endif /* not USG */
#endif /* DBX_DEBUGGING_INFO */

/* .stabd code for line number.  */
#ifndef N_SLINE
#define	N_SLINE	0x44
#endif

/* .stabs code for included file name.  */
#ifndef N_SOL
#define	N_SOL 0x84
#endif

#define min(A,B) ((A) < (B) ? (A) : (B))

rtx peephole ();
void output_asm_insn ();
rtx alter_subreg ();
static int alter_cond ();
void output_asm_label ();
static void output_operand ();
void output_address ();
void output_addr_const ();
static void output_source_line ();
rtx final_scan_insn ();

/* the sdb debugger needs the line given as an offset from the beginning
   of the current function -wfs*/

extern int sdb_begin_function_line;

/* Line number of last NOTE.  */
static int last_linenum;

/* Number of basic blocks seen so far;
   used if profile_block_flag is set.  */
static int count_basic_blocks;

/* Nonzero while outputting an `asm' with operands.
   This means that inconsistencies are the user's fault, so don't abort.
   The precise value is the insn being output, to pass to error_for_asm.  */
static rtx this_is_asm_operands;

/* Number of operands of this insn, for an `asm' with operands.  */
static int insn_noperands;

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

extern FILE *asm_out_file;

/* Compare optimization flag. */

static rtx last_ignored_compare = 0;

/* Flag indicating this insn is the start of a new basic block. */

static int new_block = 1;

/* All the symbol-blocks (levels of scoping) in the compilation
   are assigned sequence numbers in order of appearance of the
   beginnings of the symbol-blocks.  Both final and dbxout do this,
   and assume that they will both give the same number to each block.
   Final uses these sequence numbers to generate assembler label names
   LBBnnn and LBEnnn for the beginning and end of the symbol-block.
   Dbxout uses the sequence nunbers to generate references to the same labels
   from the dbx debugging information.

   Sdb records this level at the beginning
   of each function, so that when it recurses down the declarations, it may
   find the current level, since it outputs the block beginning and endings
   at the point in the asm file, where the blocks would begin and end.  */

int next_block_index;

/* Chain of all `struct gdbfile's.  */

struct gdbfile *gdbfiles;

/* `struct gdbfile' for the last file we wrote a line number for.  */

static struct gdbfile *current_gdbfile;

/* Filenum to assign to the next distinct source file encountered.  */

static int next_gdb_filenum;

/* This variable contains machine-dependent flags (defined in tm-...h)
   set and examined by output routines
   that describe how to interpret the condition codes properly.  */

CC_STATUS cc_status;

/* During output of an insn, this contains a copy of cc_status
   from before the insn.  */

CC_STATUS cc_prev_status;

/* Last source file name mentioned in a NOTE insn.  */

static char *lastfile;

/* Indexed by hardware reg number, is 1 if that register is ever
   used in the current function.

   In life_analysis, or in stupid_life_analysis, this is set
   up to record the hard regs used explicitly.  Reload adds
   in the hard regs used for holding pseudo regs.  Final uses
   it to generate the code in the function prologue and epilogue
   to save and restore registers as needed.  */

char regs_ever_live[FIRST_PSEUDO_REGISTER];

/* Nonzero means current function must be given a frame pointer.
   Set in stmt.c if anything is allocated on the stack there.
   Set in reload1.c if anything is allocated on the stack there.  */

int frame_pointer_needed;

/* Assign unique numbers to labels generated for profiling.  */

int profile_label_no;

/* Length so far allocated in PENDING_BLOCKS.  */

static int max_block_depth;

/* Stack of sequence numbers of symbol-blocks of which we have seen the
   beginning but not yet the end.  Sequence numbers are assigned at
   the beginning; this stack allows us to find the sequence number
   of a block that is ending.  */

static int *pending_blocks;

/* Number of elements currently in use in PENDING_BLOCKS.  */

static int block_depth;

/* Nonzero if have enabled APP processing of our assembler output.  */

static int app_on;

/* If we are outputting an insn sequence, this contains the sequence rtx.
   Zero otherwise.  */

rtx final_sequence;

/* Initialize data in final at the beginning of a compilation.  */

void
init_final (filename)
     char *filename;
{
  next_block_index = 2;
  lastfile = filename;
  app_on = 0;
  max_block_depth = 20;
  pending_blocks = (int *) xmalloc (20 * sizeof *pending_blocks);
  gdbfiles = 0;
  next_gdb_filenum = 0;
  final_sequence = 0;
}

/* Called at end of source file,
   to output the block-profiling table for this entire compilation.  */

void
end_final (filename)
     char *filename;
{
  int i;

  if (profile_block_flag)
    {
      char name[12];

      data_section ();

      /* Output the main header, of 6 words:
	 0:  1 if this file's initialized, else 0.
	 1:  address of file name.
	 2:  address of table of counts.
	 4:  number of counts in the table.
	 5:  always 0, for compatibility with Sun.
	 6:  extra word added by GNU: address of address table
	      which contains addresses of basic blocks,
	      in parallel with the table of counts.  */
      ASM_OUTPUT_ALIGN (asm_out_file,
			exact_log2 (min (UNITS_PER_WORD,
					 BIGGEST_ALIGNMENT / BITS_PER_UNIT)));

      ASM_OUTPUT_INTERNAL_LABEL (asm_out_file, "LPBX", 0);
      assemble_integer_zero ();

      ASM_GENERATE_INTERNAL_LABEL (name, "LPBX", 1);
      ASM_OUTPUT_INT (asm_out_file, gen_rtx (SYMBOL_REF, Pmode, name));
      ASM_GENERATE_INTERNAL_LABEL (name, "LPBX", 2);
      ASM_OUTPUT_INT (asm_out_file, gen_rtx (SYMBOL_REF, Pmode, name));
      ASM_OUTPUT_INT (asm_out_file, gen_rtx (CONST_INT, VOIDmode,
					     count_basic_blocks));
      assemble_integer_zero ();
      ASM_GENERATE_INTERNAL_LABEL (name, "LPBX", 3);
      ASM_OUTPUT_INT (asm_out_file, gen_rtx (SYMBOL_REF, Pmode, name));

      /* Output the file name.  */
      ASM_OUTPUT_INTERNAL_LABEL (asm_out_file, "LPBX", 1);
      {
	int len = strlen (filename);
	char *data_file = (char *) alloca (len + 3);
	strcpy (data_file, filename);
	if (len > 2 && ! strcmp (".c", data_file + len - 2))
	  data_file[len - 2] = 0;
	else if (len > 2 && ! strcmp (".i", data_file + len - 2))
	  data_file[len - 2] = 0;
	else if (len > 3 && ! strcmp (".co", data_file + len - 3))
	  data_file[len - 3] = 0;
	strcat (data_file, ".d");
	assemble_string (data_file, strlen (data_file) + 1);
      }

      /* Realign data section.  */
      ASM_OUTPUT_ALIGN (asm_out_file,
			exact_log2 (min (UNITS_PER_WORD,
					 BIGGEST_ALIGNMENT / BITS_PER_UNIT)));

      /* Make space for the table of counts.  */
      ASM_OUTPUT_INTERNAL_LABEL (asm_out_file, "LPBX", 2);
      ASM_OUTPUT_SKIP (asm_out_file, UNITS_PER_WORD * count_basic_blocks);

      /* Output the table of addresses.  */
      text_section ();
      ASM_OUTPUT_INTERNAL_LABEL (asm_out_file, "LPBX", 3);
      for (i = 0; i < count_basic_blocks; i++)
	{
	  char name[12];
	  ASM_GENERATE_INTERNAL_LABEL (name, "LPB", i);
	  ASM_OUTPUT_INT (asm_out_file, gen_rtx (SYMBOL_REF, Pmode, name));
	}

      /* End with the address of the table of addresses,
	 so we can find it easily, as the last word in the file's text.  */
      ASM_GENERATE_INTERNAL_LABEL (name, "LPBX", 3);
      ASM_OUTPUT_INT (asm_out_file, gen_rtx (SYMBOL_REF, Pmode, name));
    }
}

/* Enable APP processing of subsequent output.
   Used before the output from an `asm' statement.  */

void
app_enable ()
{
  if (! app_on)
    {
      fprintf (asm_out_file, ASM_APP_ON);
      app_on = 1;
    }
}

/* Enable APP processing of subsequent output.
   Called from varasm.c before most kinds of output.  */

void
app_disable ()
{
  if (app_on)
    {
      fprintf (asm_out_file, ASM_APP_OFF);
      app_on = 0;
    }
}

/* Return the number of slots filled in the current 
   delayed branch sequence. */

#ifdef HAVE_DELAYED_BRANCH
int
dbr_sequence_length ()
{
  int i;
  int slots = 0;
  /* It's zero if we are not scheduling or not in a sequence. 
     (We never count the first insn.)                  */
  if (flag_delayed_branch && final_sequence != 0)
    {
      for (i = 1; i < XVECLEN (final_sequence, 0); i++)
	slots += DBR_INSN_SLOTS (XVECEXP (final_sequence, 0, i));
    }
  return slots;
}
#endif

/* Output assembler code for the start of a function,
   and initialize some of the variables in this file
   for the new function.  The label for the function and associated
   assembler pseudo-ops have already been output in `assemble_function'.

   FIRST is the first insn of the rtl for the function being compiled.
   FILE is the file to write assembler code to.
   WRITE_SYMBOLS says which kind of debugging info to write (or none).
   OPTIMIZE is nonzero if we should eliminate redundant
     test and compare insns.  */

void
final_start_function (first, file, write_symbols, optimize)
     rtx first;
     FILE *file;
     enum debugger write_symbols;
     int optimize;
{
  block_depth = 0;

  this_is_asm_operands = 0;

  /* Record beginning of the symbol-block that's the entire function.  */

  if (write_symbols == GDB_DEBUG)
    {
      pending_blocks[block_depth++] = next_block_index;
      fprintf (file, "\t.gdbbeg %d\n", next_block_index++);
    }

  /* Initial line number is supposed to be output
     before the function's prologue and label
     so that the function's address will not appear to be
     in the last statement of the preceding function.  */
  if (NOTE_LINE_NUMBER (first) != NOTE_INSN_DELETED)
    {
      if (write_symbols == SDB_DEBUG)
	/* For sdb, let's not, but say we did.
	   We need to set last_linenum for sdbout_function_begin,
	   but we can't have an actual line number before the .bf symbol.
	   (sdb_begin_function_line is not set,
	   and other compilers don't do it.)  */
	last_linenum = NOTE_LINE_NUMBER (first);
      else
	output_source_line (file, first, write_symbols);
    }

  /* The Sun386i and perhaps other machines don't work right
     if the profiling code comes after the prologue.  */
#ifdef PROFILE_BEFORE_PROLOGUE
  if (profile_flag)
    profile_function (file);
#endif /* PROFILE_BEFORE_PROLOGUE */

#ifdef FUNCTION_PROLOGUE
  /* First output the function prologue: code to set up the stack frame.  */
  FUNCTION_PROLOGUE (file, get_frame_size ());
#endif

#ifdef SDB_DEBUGGING_INFO
  next_block_index = 1;
#endif

#ifdef FUNCTION_BLOCK_PROFILER
  if (profile_block_flag)
    {
      FUNCTION_BLOCK_PROFILER (file, profile_label_no);
    }
#endif /* FUNCTION_BLOCK_PROFILER */

#ifndef PROFILE_BEFORE_PROLOGUE
  if (profile_flag)
    profile_function (file);
#endif /* not PROFILE_BEFORE_PROLOGUE */

  profile_label_no++;
}

profile_function (file)
     FILE *file;
{
  int align = min (BIGGEST_ALIGNMENT, BITS_PER_WORD);
  extern int current_function_returns_struct;
  extern int current_function_needs_context;
  int sval = current_function_returns_struct;
  int cxt = current_function_needs_context;

  data_section ();
  ASM_OUTPUT_ALIGN (file, floor_log2 (align / BITS_PER_UNIT));
  ASM_OUTPUT_INTERNAL_LABEL (file, "LP", profile_label_no);
  assemble_integer_zero ();

  text_section ();

#ifdef STRUCT_VALUE_INCOMING_REGNUM
  if (sval)
    ASM_OUTPUT_REG_PUSH (file, STRUCT_VALUE_INCOMING_REGNUM);
#else
#ifdef STRUCT_VALUE_REGNUM
  if (sval)
    ASM_OUTPUT_REG_PUSH (file, STRUCT_VALUE_REGNUM);
#endif
#endif

#if 0
#ifdef STATIC_CHAIN_INCOMING_REGNUM
  if (cxt)
    ASM_OUTPUT_REG_PUSH (file, STATIC_CHAIN_INCOMING_REGNUM);
#else
#ifdef STATIC_CHAIN_REGNUM
  if (cxt)
    ASM_OUTPUT_REG_PUSH (file, STATIC_CHAIN_REGNUM);
#endif
#endif
#endif /* 0 */

  FUNCTION_PROFILER (file, profile_label_no);

#if 0
#ifdef STATIC_CHAIN_INCOMING_REGNUM
  if (cxt)
    ASM_OUTPUT_REG_POP (file, STATIC_CHAIN_INCOMING_REGNUM);
#else
#ifdef STATIC_CHAIN_REGNUM
  if (cxt)
    ASM_OUTPUT_REG_POP (file, STATIC_CHAIN_REGNUM);
#endif
#endif
#endif /* 0 */

#ifdef STRUCT_VALUE_INCOMING_REGNUM
  if (sval)
    ASM_OUTPUT_REG_POP (file, STRUCT_VALUE_INCOMING_REGNUM);
#else
#ifdef STRUCT_VALUE_REGNUM
  if (sval)
    ASM_OUTPUT_REG_POP (file, STRUCT_VALUE_REGNUM);
#endif
#endif
}

/* Output assembler code for the end of a function.
   For clarity, args are same as those of `final_start_function'
   even though not all of them are needed.  */

void
final_end_function (first, file, write_symbols, optimize)
     rtx first;
     FILE *file;
     enum debugger write_symbols;
     int optimize;
{
  if (app_on)
    {
      fprintf (file, ASM_APP_OFF);
      app_on = 0;
    }

  if (write_symbols == GDB_DEBUG)
    fprintf (file, "\t.gdbend %d\n", pending_blocks[0]);

#ifdef SDB_DEBUGGING_INFO
  if (write_symbols == SDB_DEBUG)
    sdbout_end_function (last_linenum);
#endif

#ifdef FUNCTION_EPILOGUE
  /* Finally, output the function epilogue:
     code to restore the stack frame and return to the caller.  */
  FUNCTION_EPILOGUE (file, get_frame_size ());
#endif

#ifdef SDB_DEBUGGING_INFO
  if (write_symbols == SDB_DEBUG)
    sdbout_end_epilogue ();
#endif

  /* If FUNCTION_EPILOGUE is not defined, then the function body
     itself contains return instructions wherever needed.  */
}

/* Output assembler code for some insns: all or part of a function.
   For description of args, see `final_start_function', above.

   PRESCAN is 1 if we are not really outputting,
     just scanning as if we were outputting.
   Prescanning deletes and rearranges insns just like ordinary output.
   PRESCAN is -2 if we are outputting after having prescanned.
   In this case, don't try to delete or rearrange insns
   because that has already been done.
   Prescanning is done only on certain machines.  */

void
final (first, file, write_symbols, optimize, prescan)
     rtx first;
     FILE *file;
     enum debugger write_symbols;