final.c

gcc库的原代码,对编程有很大帮助.

		  if (result == 1)
		    validate_change (insn, &SET_SRC (body), const_true_rtx, 0);
		  else if (result == -1)
		    validate_change (insn, &SET_SRC (body), const0_rtx, 0);
		  else if (result == 2)
		    INSN_CODE (insn) = -1;
		}
	      }
	  }
#endif

	/* Do machine-specific peephole optimizations if desired.  */

	if (optimize && !flag_no_peephole && !nopeepholes)
	  {
	    rtx next = peephole (insn);
	    /* When peepholing, if there were notes within the peephole,
	       emit them before the peephole.  */
	    if (next != 0 && next != NEXT_INSN (insn))
	      {
		rtx prev = PREV_INSN (insn);
		rtx note;

		for (note = NEXT_INSN (insn); note != next;
		     note = NEXT_INSN (note))
		  final_scan_insn (note, file, optimize, prescan, nopeepholes);

		/* In case this is prescan, put the notes
		   in proper position for later rescan.  */
		note = NEXT_INSN (insn);
		PREV_INSN (note) = prev;
		NEXT_INSN (prev) = note;
		NEXT_INSN (PREV_INSN (next)) = insn;
		PREV_INSN (insn) = PREV_INSN (next);
		NEXT_INSN (insn) = next;
		PREV_INSN (next) = insn;
	      }

	    /* PEEPHOLE might have changed this.  */
	    body = PATTERN (insn);
	  }

	/* Try to recognize the instruction.
	   If successful, verify that the operands satisfy the
	   constraints for the instruction.  Crash if they don't,
	   since `reload' should have changed them so that they do.  */

	insn_code_number = recog_memoized (insn);
	insn_extract (insn);
	for (i = 0; i < insn_n_operands[insn_code_number]; i++)
	  {
	    if (GET_CODE (recog_operand[i]) == SUBREG)
	      recog_operand[i] = alter_subreg (recog_operand[i]);
	    else if (GET_CODE (recog_operand[i]) == PLUS
		     || GET_CODE (recog_operand[i]) == MULT)
	      recog_operand[i] = walk_alter_subreg (recog_operand[i]);
	  }

	for (i = 0; i < insn_n_dups[insn_code_number]; i++)
	  {
	    if (GET_CODE (*recog_dup_loc[i]) == SUBREG)
	      *recog_dup_loc[i] = alter_subreg (*recog_dup_loc[i]);
	    else if (GET_CODE (*recog_dup_loc[i]) == PLUS
		     || GET_CODE (*recog_dup_loc[i]) == MULT)
	      *recog_dup_loc[i] = walk_alter_subreg (*recog_dup_loc[i]);
	  }

#ifdef REGISTER_CONSTRAINTS
	if (! constrain_operands (insn_code_number, 1))
	  fatal_insn_not_found (insn);
#endif

	/* Some target machines need to prescan each insn before
	   it is output.  */

#ifdef FINAL_PRESCAN_INSN
	FINAL_PRESCAN_INSN (insn, recog_operand,
			    insn_n_operands[insn_code_number]);
#endif

#ifdef HAVE_cc0
	cc_prev_status = cc_status;

	/* Update `cc_status' for this instruction.
	   The instruction's output routine may change it further.
	   If the output routine for a jump insn needs to depend
	   on the cc status, it should look at cc_prev_status.  */

	NOTICE_UPDATE_CC (body, insn);
#endif

	debug_insn = insn;

	/* If the proper template needs to be chosen by some C code,
	   run that code and get the real template.  */

	template = insn_template[insn_code_number];
	if (template == 0)
	  {
	    template = (*insn_outfun[insn_code_number]) (recog_operand, insn);

	    /* If the C code returns 0, it means that it is a jump insn
	       which follows a deleted test insn, and that test insn
	       needs to be reinserted.  */
	    if (template == 0)
	      {
		if (prev_nonnote_insn (insn) != last_ignored_compare)
		  abort ();
		new_block = 0;
		return prev_nonnote_insn (insn);
	      }
	  }

	/* If the template is the string "#", it means that this insn must
	   be split.  */
	if (template[0] == '#' && template[1] == '\0')
	  {
	    rtx new = try_split (body, insn, 0);

	    /* If we didn't split the insn, go away.  */
	    if (new == insn && PATTERN (new) == body)
	      abort ();
	      
	    new_block = 0;
	    return new;
	  }
	
	if (prescan > 0)
	  break;

	/* Output assembler code from the template.  */

	output_asm_insn (template, recog_operand);

#if 0
	/* It's not at all clear why we did this and doing so interferes
	   with tests we'd like to do to use REG_WAS_0 notes, so let's try
	   with this out.  */

	/* Mark this insn as having been output.  */
	INSN_DELETED_P (insn) = 1;
#endif

	debug_insn = 0;
      }
    }
  return NEXT_INSN (insn);
}

/* Output debugging info to the assembler file FILE
   based on the NOTE-insn INSN, assumed to be a line number.  */

static void
output_source_line (file, insn)
     FILE *file;
     rtx insn;
{
  register char *filename = NOTE_SOURCE_FILE (insn);

  /* Remember filename for basic block profiling.
     Filenames are allocated on the permanent obstack
     or are passed in ARGV, so we don't have to save
     the string.  */

  if (profile_block_flag && last_filename != filename)
    bb_file_label_num = add_bb_string (filename, TRUE);

  last_filename = filename;
  last_linenum = NOTE_LINE_NUMBER (insn);
  high_block_linenum = MAX (last_linenum, high_block_linenum);
  high_function_linenum = MAX (last_linenum, high_function_linenum);

  if (write_symbols != NO_DEBUG)
    {
#ifdef SDB_DEBUGGING_INFO
      if (write_symbols == SDB_DEBUG
#if 0 /* People like having line numbers even in wrong file!  */
	  /* COFF can't handle multiple source files--lose, lose.  */
	  && !strcmp (filename, main_input_filename)
#endif
	  /* COFF relative line numbers must be positive.  */
	  && last_linenum > sdb_begin_function_line)
	{
#ifdef ASM_OUTPUT_SOURCE_LINE
	  ASM_OUTPUT_SOURCE_LINE (file, last_linenum);
#else
	  fprintf (file, "\t.ln\t%d\n",
		   ((sdb_begin_function_line > -1)
		    ? last_linenum - sdb_begin_function_line : 1));
#endif
	}
#endif

#if defined (DBX_DEBUGGING_INFO)
      if (write_symbols == DBX_DEBUG)
	dbxout_source_line (file, filename, NOTE_LINE_NUMBER (insn));
#endif

#if defined (XCOFF_DEBUGGING_INFO)
      if (write_symbols == XCOFF_DEBUG)
	xcoffout_source_line (file, filename, insn);
#endif

#ifdef DWARF_DEBUGGING_INFO
      if (write_symbols == DWARF_DEBUG)
	dwarfout_line (filename, NOTE_LINE_NUMBER (insn));
#endif
    }
}

/* If X is a SUBREG, replace it with a REG or a MEM,
   based on the thing it is a subreg of.  */

rtx
alter_subreg (x)
     register rtx x;
{
  register rtx y = SUBREG_REG (x);
  if (GET_CODE (y) == SUBREG)
    y = alter_subreg (y);

  if (GET_CODE (y) == REG)
    {
      /* If the containing reg really gets a hard reg, so do we.  */
      PUT_CODE (x, REG);
      REGNO (x) = REGNO (y) + SUBREG_WORD (x);
    }
  else if (GET_CODE (y) == MEM)
    {
      register int offset = SUBREG_WORD (x) * UNITS_PER_WORD;
      if (BYTES_BIG_ENDIAN)
	offset -= (MIN (UNITS_PER_WORD, GET_MODE_SIZE (GET_MODE (x)))
		   - MIN (UNITS_PER_WORD, GET_MODE_SIZE (GET_MODE (y))));
      PUT_CODE (x, MEM);
      MEM_VOLATILE_P (x) = MEM_VOLATILE_P (y);
      XEXP (x, 0) = plus_constant (XEXP (y, 0), offset);
    }

  return x;
}

/* Do alter_subreg on all the SUBREGs contained in X.  */

static rtx
walk_alter_subreg (x)
     rtx x;
{
  switch (GET_CODE (x))
    {
    case PLUS:
    case MULT:
      XEXP (x, 0) = walk_alter_subreg (XEXP (x, 0));
      XEXP (x, 1) = walk_alter_subreg (XEXP (x, 1));
      break;

    case MEM:
      XEXP (x, 0) = walk_alter_subreg (XEXP (x, 0));
      break;

    case SUBREG:
      return alter_subreg (x);
    }

  return x;
}

#ifdef HAVE_cc0

/* Given BODY, the body of a jump instruction, alter the jump condition
   as required by the bits that are set in cc_status.flags.
   Not all of the bits there can be handled at this level in all cases.

   The value is normally 0.
   1 means that the condition has become always true.
   -1 means that the condition has become always false.
   2 means that COND has been altered.  */

static int
alter_cond (cond)
     register rtx cond;
{
  int value = 0;

  if (cc_status.flags & CC_REVERSED)
    {
      value = 2;
      PUT_CODE (cond, swap_condition (GET_CODE (cond)));
    }

  if (cc_status.flags & CC_INVERTED)
    {
      value = 2;
      PUT_CODE (cond, reverse_condition (GET_CODE (cond)));
    }

  if (cc_status.flags & CC_NOT_POSITIVE)
    switch (GET_CODE (cond))
      {
      case LE:
      case LEU:
      case GEU:
	/* Jump becomes unconditional.  */
	return 1;

      case GT:
      case GTU:
      case LTU:
	/* Jump becomes no-op.  */
	return -1;

      case GE:
	PUT_CODE (cond, EQ);
	value = 2;
	break;

      case LT:
	PUT_CODE (cond, NE);
	value = 2;
	break;
      }

  if (cc_status.flags & CC_NOT_NEGATIVE)
    switch (GET_CODE (cond))
      {
      case GE:
      case GEU:
	/* Jump becomes unconditional.  */
	return 1;

      case LT:
      case LTU:
	/* Jump becomes no-op.  */
	return -1;

      case LE:
      case LEU:
	PUT_CODE (cond, EQ);
	value = 2;
	break;

      case GT:
      case GTU:
	PUT_CODE (cond, NE);
	value = 2;
	break;
      }

  if (cc_status.flags & CC_NO_OVERFLOW)
    switch (GET_CODE (cond))
      {
      case GEU:
	/* Jump becomes unconditional.  */
	return 1;

      case LEU:
	PUT_CODE (cond, EQ);
	value = 2;
	break;

      case GTU:
	PUT_CODE (cond, NE);
	value = 2;
	break;

      case LTU:
	/* Jump becomes no-op.  */
	return -1;
      }

  if (cc_status.flags & (CC_Z_IN_NOT_N | CC_Z_IN_N))
    switch (GET_CODE (cond))
      {
      case LE:
      case LEU:
      case GE:
      case GEU:
      case LT:
      case LTU:
      case GT:
      case GTU:
	abort ();

      case NE:
	PUT_CODE (cond, cc_status.flags & CC_Z_IN_N ? GE : LT);
	value = 2;
	break;

      case EQ:
	PUT_CODE (cond, cc_status.flags & CC_Z_IN_N ? LT : GE);
	value = 2;
	break;
      }

  if (cc_status.flags & CC_NOT_SIGNED)
    /* The flags are valid if signed condition operators are converted
       to unsigned.  */
    switch (GET_CODE (cond))
      {
      case LE:
	PUT_CODE (cond, LEU);
	value = 2;
	break;

      case LT:
	PUT_CODE (cond, LTU);
	value = 2;
	break;

      case GT:
	PUT_CODE (cond, GTU);
	value = 2;
	break;

      case GE:
	PUT_CODE (cond, GEU);
	value = 2;
	break;
      }

  return value;
}
#endif

/* Report inconsistency between the assembler template and the operands.
   In an `asm', it's the user's fault; otherwise, the compiler's fault.  */

void
output_operand_lossage (str)
     char *str;
{
  if (this_is_asm_operands)
    error_for_asm (this_is_asm_operands, "invalid `asm': %s", str);
  else
    abort ();
}

/* Output of assembler code from a template, and its subroutines.  */

/* Output text from TEMPLATE to the assembler output file,
   obeying %-directions to substitute operands taken from
   the vector OPERANDS.

   %N (for N a digit) means print operand N in usual manner.
   %lN means require operand N to be a CODE_LABEL or LABEL_REF
      and print the label name with no punctuation.
   %cN means require operand N to be a constant
      and print the constant expression with no punctuation.
   %aN means expect operand N to be a memory address
      (not a memory reference!) and print a reference
      to that address.
   %nN means expect operand N to be a constant
      and print a constant expression for minus the value
      of the operand, with no other punctuation.  */

static void
output_asm_name ()
{
  if (flag_print_asm_name)
    {
      /* Annotate the assembly with a comment describing the pattern and
	 alternative used.  */
      if (debug_insn)
	{
	  register int num = INSN_CODE (debug_insn);
	  fprintf (asm_out_file, " %s %d %s", 
		   ASM_COMMENT_START, INSN_UID (debug_insn), insn_name[num]);
	  if (insn_n_a