recog.c

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/* Subroutines used by or related to instruction recognition.
   Copyright (C) 1987, 88, 91, 92, 93, 1994 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.  */


#include "config.h"
#include "rtl.h"
#include <stdio.h>
#include "insn-config.h"
#include "insn-attr.h"
#include "insn-flags.h"
#include "insn-codes.h"
#include "recog.h"
#include "regs.h"
#include "hard-reg-set.h"
#include "flags.h"
#include "real.h"

#ifndef STACK_PUSH_CODE
#ifdef STACK_GROWS_DOWNWARD
#define STACK_PUSH_CODE PRE_DEC
#else
#define STACK_PUSH_CODE PRE_INC
#endif
#endif

/* Import from final.c: */
extern rtx alter_subreg ();

int strict_memory_address_p ();
int memory_address_p ();

/* Nonzero means allow operands to be volatile.
   This should be 0 if you are generating rtl, such as if you are calling
   the functions in optabs.c and expmed.c (most of the time).
   This should be 1 if all valid insns need to be recognized,
   such as in regclass.c and final.c and reload.c.

   init_recog and init_recog_no_volatile are responsible for setting this.  */

int volatile_ok;

/* On return from `constrain_operands', indicate which alternative
   was satisfied.  */

int which_alternative;

/* Nonzero after end of reload pass.
   Set to 1 or 0 by toplev.c.
   Controls the significance of (SUBREG (MEM)).  */

int reload_completed;

/* Initialize data used by the function `recog'.
   This must be called once in the compilation of a function
   before any insn recognition may be done in the function.  */

void
init_recog_no_volatile ()
{
  volatile_ok = 0;
}

void
init_recog ()
{
  volatile_ok = 1;
}

/* Try recognizing the instruction INSN,
   and return the code number that results.
   Remember the code so that repeated calls do not
   need to spend the time for actual rerecognition.

   This function is the normal interface to instruction recognition.
   The automatically-generated function `recog' is normally called
   through this one.  (The only exception is in combine.c.)  */

int
recog_memoized (insn)
     rtx insn;
{
  if (INSN_CODE (insn) < 0)
    INSN_CODE (insn) = recog (PATTERN (insn), insn, NULL_PTR);
  return INSN_CODE (insn);
}

/* Check that X is an insn-body for an `asm' with operands
   and that the operands mentioned in it are legitimate.  */

int
check_asm_operands (x)
     rtx x;
{
  int noperands = asm_noperands (x);
  rtx *operands;
  int i;

  if (noperands < 0)
    return 0;
  if (noperands == 0)
    return 1;

  operands = (rtx *) alloca (noperands * sizeof (rtx));
  decode_asm_operands (x, operands, NULL_PTR, NULL_PTR, NULL_PTR);

  for (i = 0; i < noperands; i++)
    if (!general_operand (operands[i], VOIDmode))
      return 0;

  return 1;
}

/* Static data for the next two routines.

   The maximum number of changes supported is defined as the maximum
   number of operands times 5.  This allows for repeated substitutions
   inside complex indexed address, or, alternatively, changes in up
   to 5 insns.  */

#define MAX_CHANGE_LOCS	(MAX_RECOG_OPERANDS * 5)

static rtx change_objects[MAX_CHANGE_LOCS];
static int change_old_codes[MAX_CHANGE_LOCS];
static rtx *change_locs[MAX_CHANGE_LOCS];
static rtx change_olds[MAX_CHANGE_LOCS];

static int num_changes = 0;

/* Validate a proposed change to OBJECT.  LOC is the location in the rtl for
   at which NEW will be placed.  If OBJECT is zero, no validation is done,
   the change is simply made.

   Two types of objects are supported:  If OBJECT is a MEM, memory_address_p
   will be called with the address and mode as parameters.  If OBJECT is
   an INSN, CALL_INSN, or JUMP_INSN, the insn will be re-recognized with
   the change in place.

   IN_GROUP is non-zero if this is part of a group of changes that must be
   performed as a group.  In that case, the changes will be stored.  The
   function `apply_change_group' will validate and apply the changes.

   If IN_GROUP is zero, this is a single change.  Try to recognize the insn
   or validate the memory reference with the change applied.  If the result
   is not valid for the machine, suppress the change and return zero.
   Otherwise, perform the change and return 1.  */

int
validate_change (object, loc, new, in_group)
    rtx object;
    rtx *loc;
    rtx new;
    int in_group;
{
  rtx old = *loc;

  if (old == new || rtx_equal_p (old, new))
    return 1;

  if (num_changes >= MAX_CHANGE_LOCS
      || (in_group == 0 && num_changes != 0))
    abort ();

  *loc = new;

  /* Save the information describing this change.  */
  change_objects[num_changes] = object;
  change_locs[num_changes] = loc;
  change_olds[num_changes] = old;

  if (object && GET_CODE (object) != MEM)
    {
      /* Set INSN_CODE to force rerecognition of insn.  Save old code in
	 case invalid.  */
      change_old_codes[num_changes] = INSN_CODE (object);
      INSN_CODE (object) = -1;
    }

  num_changes++;

  /* If we are making a group of changes, return 1.  Otherwise, validate the
     change group we made.  */

  if (in_group)
    return 1;
  else
    return apply_change_group ();
}

/* Apply a group of changes previously issued with `validate_change'.
   Return 1 if all changes are valid, zero otherwise.  */

int
apply_change_group ()
{
  int i;

  /* The changes have been applied and all INSN_CODEs have been reset to force
     rerecognition.

     The changes are valid if we aren't given an object, or if we are
     given a MEM and it still is a valid address, or if this is in insn
     and it is recognized.  In the latter case, if reload has completed,
     we also require that the operands meet the constraints for
     the insn.  We do not allow modifying an ASM_OPERANDS after reload
     has completed because verifying the constraints is too difficult.  */

  for (i = 0; i < num_changes; i++)
    {
      rtx object = change_objects[i];

      if (object == 0)
	continue;

      if (GET_CODE (object) == MEM)
	{
	  if (! memory_address_p (GET_MODE (object), XEXP (object, 0)))
	    break;
	}
      else if ((recog_memoized (object) < 0
		&& (asm_noperands (PATTERN (object)) < 0
		    || ! check_asm_operands (PATTERN (object))
		    || reload_completed))
	       || (reload_completed
		   && (insn_extract (object),
		       ! constrain_operands (INSN_CODE (object), 1))))
	{
	  rtx pat = PATTERN (object);

	  /* Perhaps we couldn't recognize the insn because there were
	     extra CLOBBERs at the end.  If so, try to re-recognize
	     without the last CLOBBER (later iterations will cause each of
	     them to be eliminated, in turn).  But don't do this if we
	     have an ASM_OPERAND.  */
	  if (GET_CODE (pat) == PARALLEL
	      && GET_CODE (XVECEXP (pat, 0, XVECLEN (pat, 0) - 1)) == CLOBBER
	      && asm_noperands (PATTERN (object)) < 0)
	    {
	       rtx newpat;

	       if (XVECLEN (pat, 0) == 2)
		 newpat = XVECEXP (pat, 0, 0);
	       else
		 {
		   int j;

		   newpat = gen_rtx (PARALLEL, VOIDmode, 
				     gen_rtvec (XVECLEN (pat, 0) - 1));
		   for (j = 0; j < XVECLEN (newpat, 0); j++)
		     XVECEXP (newpat, 0, j) = XVECEXP (pat, 0, j);
		 }

	       /* Add a new change to this group to replace the pattern
		  with this new pattern.  Then consider this change
		  as having succeeded.  The change we added will
		  cause the entire call to fail if things remain invalid.

		  Note that this can lose if a later change than the one
		  we are processing specified &XVECEXP (PATTERN (object), 0, X)
		  but this shouldn't occur.  */

	       validate_change (object, &PATTERN (object), newpat, 1);
	     }
	  else if (GET_CODE (pat) == USE || GET_CODE (pat) == CLOBBER)
	    /* If this insn is a CLOBBER or USE, it is always valid, but is
	       never recognized.  */
	    continue;
	  else
	    break;
	}
    }

  if (i == num_changes)
    {
      num_changes = 0;
      return 1;
    }
  else
    {
      cancel_changes (0);
      return 0;
    }
}

/* Return the number of changes so far in the current group.   */

int
num_validated_changes ()
{
  return num_changes;
}

/* Retract the changes numbered NUM and up.  */

void
cancel_changes (num)
     int num;
{
  int i;

  /* Back out all the changes.  Do this in the opposite order in which
     they were made.  */
  for (i = num_changes - 1; i >= num; i--)
    {
      *change_locs[i] = change_olds[i];
      if (change_objects[i] && GET_CODE (change_objects[i]) != MEM)
	INSN_CODE (change_objects[i]) = change_old_codes[i];
    }
  num_changes = num;
}

/* Replace every occurrence of FROM in X with TO.  Mark each change with
   validate_change passing OBJECT.  */

static void
validate_replace_rtx_1 (loc, from, to, object)
     rtx *loc;
     rtx from, to, object;
{
  register int i, j;
  register char *fmt;
  register rtx x = *loc;
  enum rtx_code code = GET_CODE (x);

  /* X matches FROM if it is the same rtx or they are both referring to the
     same register in the same mode.  Avoid calling rtx_equal_p unless the
     operands look similar.  */

  if (x == from
      || (GET_CODE (x) == REG && GET_CODE (from) == REG
	  && GET_MODE (x) == GET_MODE (from)
	  && REGNO (x) == REGNO (from))
      || (GET_CODE (x) == GET_CODE (from) && GET_MODE (x) == GET_MODE (from)
	  && rtx_equal_p (x, from)))
    {
      validate_change (object, loc, to, 1);
      return;
    }

  /* For commutative or comparison operations, try replacing each argument
     separately and seeing if we made any changes.  If so, put a constant
     argument last.*/
  if (GET_RTX_CLASS (code) == '<' || GET_RTX_CLASS (code) == 'c')
    {
      int prev_changes = num_changes;

      validate_replace_rtx_1 (&XEXP (x, 0), from, to, object);
      validate_replace_rtx_1 (&XEXP (x, 1), from, to, object);
      if (prev_changes != num_changes && CONSTANT_P (XEXP (x, 0)))
	{
	  validate_change (object, loc,
			   gen_rtx (GET_RTX_CLASS (code) == 'c' ? code
				    : swap_condition (code),
				    GET_MODE (x), XEXP (x, 1), XEXP (x, 0)),
			   1);
	  x = *loc;
	  code = GET_CODE (x);
	}
    }

  switch (code)
    {
    case PLUS:
      /* If we have have a PLUS whose second operand is now a CONST_INT, use
	 plus_constant to try to simplify it.  */
      if (GET_CODE (XEXP (x, 1)) == CONST_INT && XEXP (x, 1) == to)
	validate_change (object, loc, 
			 plus_constant (XEXP (x, 0), INTVAL (XEXP (x, 1))), 1);
      return;
      
    case ZERO_EXTEND:
    case SIGN_EXTEND:
      /* In these cases, the operation to be performed depends on the mode
	 of the operand.  If we are replacing the operand with a VOIDmode
	 constant, we lose the information.  So try to simplify the operation
	 in that case.  If it fails, substitute in something that we know
	 won't be recognized.  */
      if (GET_MODE (to) == VOIDmode
	  && (XEXP (x, 0) == from
	      || (GET_CODE (XEXP (x, 0)) == REG && GET_CODE (from) == REG
		  && GET_MODE (XEXP (x, 0)) == GET_MODE (from)
		  && REGNO (XEXP (x, 0)) == REGNO (from))))
	{
	  rtx new = simplify_unary_operation (code, GET_MODE (x), to,
					      GET_MODE (from));
	  if (new == 0)
	    new = gen_rtx (CLOBBER, GET_MODE (x), const0_rtx);

	  validate_change (object, loc, new, 1);
	  return;
	}
      break;
	
    case SUBREG:
      /* If we have a SUBREG of a register that we are replacing and we are
	 replacing it with a MEM, make a new MEM and try replacing the
	 SUBREG with it.  Don't do this if the MEM has a mode-dependent address
	 or if we would be widening it.  */

      if (SUBREG_REG (x) == from
	  && GET_CODE (from) == REG
	  && GET_CODE (to) == MEM
	  && ! mode_dependent_address_p (XEXP (to, 0))
	  && ! MEM_VOLATILE_P (to)
	  && GET_MODE_SIZE (GET_MODE (x)) <= GET_MODE_SIZE (GET_MODE (to)))
	{
	  int offset = SUBREG_WORD (x) * UNITS_PER_WORD;
	  enum machine_mode mode = GET_MODE (x);
	  rtx new;

	  if (BYTES_BIG_ENDIAN)
	    offset += (MIN (UNITS_PER_WORD,
			    GET_MODE_SIZE (GET_MODE (SUBREG_REG (x))))
		       - MIN (UNITS_PER_WORD, GET_MODE_SIZE (mode)));

	  new = gen_rtx (MEM, mode, plus_constant (XEXP (to, 0), offset));
	  MEM_VOLATILE_P (new) = MEM_VOLATILE_P (to);
	  RTX_UNCHANGING_P (new) = RTX_UNCHANGING_P (to);
	  MEM_IN_STRUCT_P (new) = MEM_IN_STRUCT_P (to);
	  validate_change (object, loc, new, 1);
	  return;
	}
      break;

    case ZERO_EXTRACT:
    case SIGN_EXTRACT:
      /* If we are replacing a register with memory, try to change the memory
	 to be the mode required for memory in extract operations (this isn't
	 likely to be an insertion operation; if it was, nothing bad will
	 happen, we might just fail in some cases).  */

      if (XEXP (x, 0) == from && GET_CODE (from) == REG && GET_CODE (to) == MEM
	  && GET_CODE (XEXP (x, 1)) == CONST_INT
	  && GET_CODE (XEXP (x, 2)) == CONST_INT
	  && ! mode_dependent_address_p (XEXP (to, 0))
	  && ! MEM_VOLATILE_P (to))
	{
	  enum machine_mode wanted_mode = VOIDmode;
	  enum machine_mode is_mode = GET_MODE (to);
	  int width = INTVAL (XEXP (x, 1));
	  int pos = INTVAL (XEXP (x, 2));

#ifdef HAVE_extzv
	  if (code == ZERO_EXTRACT)
	    wanted_mode = insn_operand_mode[(int) CODE_FOR_extzv][1];
#endif
#ifdef HAVE_extv
	  if (code == SIGN_EXTRACT)
	    wanted_mode = insn_operand_mode[(int) CODE_FOR_extv][1];
#endif

	  /* If we have a narrower mode, we can do something.  */
	  if (wanted_mode != VOIDmode
	      && GET_MODE_SIZE (wanted_mode) < GET_MODE_SIZE (is_mode))
	    {
	      int offset = pos / BITS_PER_UNIT;
	      rtx newmem;

		  /* If the bytes and bits are counted differently, we
		     must adjust the offset.  */
	      if (BYTES_BIG_ENDIAN != BITS_BIG_ENDIAN)
		offset = (GET_MODE_SIZE (is_mode) - GET_MODE_SIZE (wanted_mode)
			  - offset);

	      pos %= GET_MODE_BITSIZE (wanted_mode);

	      newmem = gen_rtx (MEM, wanted_mode,
				plus_constant (XEXP (to, 0), offset));
	      RTX_UNCHANGING_P (newmem) = RTX_UNCHANGING_P (to);
	      MEM_VOLATILE_P (newmem) = MEM_VOLATILE_P (to);
	      MEM_IN_STRUCT_P (newmem) = MEM_IN_STRUCT_P (to);

	      validate_change (object, &XEXP (x, 2), GEN_INT (pos), 1);
	      validate_change (object, &XEXP (x, 0), newmem, 1);
	    }
	}

      break;
    }