rtlanal.c

这是完整的gcc源代码

/* Analyze RTL for C-Compiler
   Copyright (C) 1987, 1988 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.  */


#include "config.h"
#include "rtl.h"

extern void note_stores ();
static int reg_set_p ();

/* Return 1 if the value of X is unstable
   (would be different at a different point in the program).
   The frame pointer, arg pointer, etc. are considered stable
   (within one function) and so is anything marked `unchanging'.  */

int
rtx_unstable_p (x)
     rtx x;
{
  register RTX_CODE code = GET_CODE (x);
  register int i;
  register char *fmt;

  if (code == MEM)
    return ! RTX_UNCHANGING_P (x);

  if (code == QUEUED)
    return 1;

  if (code == CONST || code == CONST_INT)
    return 0;

  if (code == REG)
    return ! (REGNO (x) == FRAME_POINTER_REGNUM
	      || REGNO (x) == ARG_POINTER_REGNUM
	      || RTX_UNCHANGING_P (x));

  fmt = GET_RTX_FORMAT (code);
  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
    if (fmt[i] == 'e')
      if (rtx_unstable_p (XEXP (x, i)))
	return 1;
  return 0;
}

/* Return 1 if X has a value that can vary even between two
   executions of the program.  0 means X can be compared reliably
   against certain constants or near-constants.
   The frame pointer and the arg pointer are considered constant.  */

int
rtx_varies_p (x)
     rtx x;
{
  register RTX_CODE code = GET_CODE (x);
  register int i;
  register char *fmt;

  if (code == MEM)
    return 1;

  if (code == QUEUED)
    return 1;

  if (code == CONST || code == CONST_INT)
    return 0;

  if (code == REG)
    return ! (REGNO (x) == FRAME_POINTER_REGNUM
	      || REGNO (x) == ARG_POINTER_REGNUM);

  fmt = GET_RTX_FORMAT (code);
  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
    if (fmt[i] == 'e')
      if (rtx_varies_p (XEXP (x, i)))
	return 1;
  return 0;
}

/* Return 1 if X refers to a memory location whose address 
   cannot be compared reliably with constant addresses,
   or if X refers to a BLKmode memory object.  */

int
rtx_addr_varies_p (x)
     rtx x;
{
  register enum rtx_code code;
  register int i;
  register char *fmt;

  if (x == 0)
    return 0;

  code = GET_CODE (x);
  if (code == MEM)
    return GET_MODE (x) == BLKmode || rtx_varies_p (XEXP (x, 0));

  fmt = GET_RTX_FORMAT (code);
  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
    if (fmt[i] == 'e')
      if (rtx_addr_varies_p (XEXP (x, i)))
	return 1;
  return 0;
}

/* Nonzero if register REG appears somewhere within IN.
   Also works if REG is not a register; in this case it checks
   for a subexpression of IN that is Lisp "equal" to REG.  */

int
reg_mentioned_p (reg, in)
     register rtx reg, in;
{
  register char *fmt;
  register int i;
  register enum rtx_code code;

  if (in == 0)
    return 0;

  if (reg == in)
    return 1;

  code = GET_CODE (in);

  switch (code)
    {
      /* Compare registers by number.  */
    case REG:
      return GET_CODE (reg) == REG && REGNO (in) == REGNO (reg);

      /* These codes have no constituent expressions
	 and are unique.  */
    case CC0:
    case PC:
      return 0;

    case CONST_INT:
      return GET_CODE (reg) == CONST_INT && INTVAL (in) == INTVAL (reg);
    }

  if (GET_CODE (reg) == code && rtx_equal_p (reg, in))
    return 1;

  fmt = GET_RTX_FORMAT (code);

  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
    {
      if (fmt[i] == 'E')
	{
	  register int j;
	  for (j = XVECLEN (in, i) - 1; j >= 0; j--)
	    if (reg_mentioned_p (reg, XVECEXP (in, i, j)))
	      return 1;
	}
      else if (fmt[i] == 'e'
	       && reg_mentioned_p (reg, XEXP (in, i)))
	return 1;
    }
  return 0;
}

/* Nonzero if register REG is used in an insn between
   FROM_INSN and TO_INSN (exclusive of those two).  */

int
reg_used_between_p (reg, from_insn, to_insn)
     rtx reg, from_insn, to_insn;
{
  register rtx insn;
  register RTX_CODE code;
  for (insn = NEXT_INSN (from_insn); insn != to_insn; insn = NEXT_INSN (insn))
    if (((code = GET_CODE (insn)) == INSN
	 || code == JUMP_INSN || code == CALL_INSN)
	&& reg_mentioned_p (reg, PATTERN (insn)))
      return 1;
  return 0;
}

/* Nonzero if register REG is set or clobbered in an insn between
   FROM_INSN and TO_INSN (exclusive of those two).
   Does not notice increments, only SET and CLOBBER.  */

int
reg_set_between_p (reg, from_insn, to_insn)
     rtx reg, from_insn, to_insn;
{
  register rtx insn;
  register RTX_CODE code;
  for (insn = NEXT_INSN (from_insn); insn != to_insn; insn = NEXT_INSN (insn))
    if (((code = GET_CODE (insn)) == INSN
	 || code == JUMP_INSN || code == CALL_INSN)
	&& reg_set_p (reg, PATTERN (insn)))
      return 1;
  return 0;
}

/* Internals of reg_set_between_p.  */

static rtx reg_set_reg;
static int reg_set_flag;

static void
reg_set_p_1 (x)
     rtx x;
{
  if (reg_overlap_mentioned_p (reg_set_reg, x))
    reg_set_flag = 1;
}

static int
reg_set_p (reg, insn)
     rtx reg, insn;
{
  reg_set_reg = reg;
  reg_set_flag = 0;
  note_stores (insn, reg_set_p_1);
  return reg_set_flag;
}

/* Return nonzero if hard register in range [REGNO, ENDREGNO)
   appears either explicitly or implicitly in X
   other than being stored into.

   References contained within the substructure at LOC do not count.
   LOC may be zero, meaning don't ignore anything.  */

int
refers_to_regno_p (regno, endregno, x, loc)
     int regno, endregno;
     rtx x;
     rtx *loc;
{
  register int i;
  register RTX_CODE code;
  register char *fmt;

 repeat:
  code = GET_CODE (x);
  if (code == REG)
    {
      i = REGNO (x);
      return (endregno > i && regno < i + HARD_REGNO_NREGS (i, GET_MODE (x)));
    }

  if (code == SET)
    {
      /* Note setting a SUBREG counts as referring to the REG it is in!  */
      if (GET_CODE (SET_DEST (x)) != REG
	  && refers_to_regno_p (regno, endregno, SET_DEST (x), loc))
	return 1;
      if (loc == &SET_SRC (x))
	return 0;
      x = SET_SRC (x);
      goto repeat;
    }

  if (code == CLOBBER)
    {
      if (GET_CODE (SET_DEST (x)) != REG
	  && refers_to_regno_p (regno, endregno, SET_DEST (x), loc))
	return 1;
      return 0;
    }

  /* X does not match, so try its subexpressions.  */

  fmt = GET_RTX_FORMAT (code);
  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
    {
      if (fmt[i] == 'e' && loc != &XEXP (x, i))
	{
	  if (i == 0)
	    {
	      x = XEXP (x, 0);
	      goto repeat;
	    }
	  else
	    if (refers_to_regno_p (regno, endregno, XEXP (x, i), loc))
	      return 1;
	}
      else if (fmt[i] == 'E')
	{
	  register int j;
	  for (j = XVECLEN (x, i) - 1; j >=0; j--)
	    if (loc != &XVECEXP (x, i, j)
		&& refers_to_regno_p (regno, endregno, XVECEXP (x, i, j), loc))
	      return 1;
	}
    }
  return 0;
}

/* Nonzero if X contains any reg that overlaps hard register REG.  */

int
reg_overlap_mentioned_p (reg, x)
     rtx reg, x;
{
  int regno = REGNO (reg);
  int endregno = regno + HARD_REGNO_NREGS (regno, GET_MODE (reg));
  return refers_to_regno_p (regno, endregno, x, 0);
}

/* This is 1 until after reload pass.  */
int rtx_equal_function_value_matters;

/* Return 1 if X and Y are identical-looking rtx's.
   This is the Lisp function EQUAL for rtx arguments.  */

int
rtx_equal_p (x, y)
     rtx x, y;
{
  register int i;
  register int j;
  register enum rtx_code code;
  register char *fmt;

  if (x == y)
    return 1;
  if (x == 0 || y == 0)
    return 0;

  code = GET_CODE (x);
  /* Rtx's of different codes cannot be equal.  */
  if (code != GET_CODE (y))
    return 0;

  /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
     (REG:SI x) and (REG:HI x) are NOT equivalent.  */

  if (GET_MODE (x) != GET_MODE (y))
    return 0;

  /* These three types of rtx's can be compared nonrecursively.  */
  /* Until the end of reload,
     don't consider the a reference to the return register of the current
     function the same as the return from a called function.  This eases
     the job of function integration.  Once the distinction no longer
     matters, the insn will be deleted.  */
  if (code == REG)
    return (REGNO (x) == REGNO (y)
	    && (! rtx_equal_function_value_matters
		|| REG_FUNCTION_VALUE_P (x) == REG_FUNCTION_VALUE_P (y)));
  if (code == LABEL_REF)
    return XEXP (x, 0) == XEXP (y, 0);
  if (code == SYMBOL_REF)