rtlanal.c

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 /* case TRAP_IF: This isn't clear yet.  */
      return 1;

    case MEM:
    case ASM_OPERANDS:
      if (MEM_VOLATILE_P (x))
	return 1;

    default:
      break;
    }

  /* Recursively scan the operands of this expression.  */

  {
    register char *fmt = GET_RTX_FORMAT (code);
    register int i;
    
    for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
      {
	if (fmt[i] == 'e')
	  {
	    if (volatile_refs_p (XEXP (x, i)))
	      return 1;
	  }
	if (fmt[i] == 'E')
	  {
	    register int j;
	    for (j = 0; j < XVECLEN (x, i); j++)
	      if (volatile_refs_p (XVECEXP (x, i, j)))
		return 1;
	  }
      }
  }
  return 0;
}

/* Similar to above, except that it also rejects register pre- and post-
   incrementing.  */

int
side_effects_p (x)
     rtx x;
{
  register RTX_CODE code;

  code = GET_CODE (x);
  switch (code)
    {
    case LABEL_REF:
    case SYMBOL_REF:
    case CONST_INT:
    case CONST:
    case CONST_DOUBLE:
    case CC0:
    case PC:
    case REG:
    case SCRATCH:
    case ASM_INPUT:
    case ADDR_VEC:
    case ADDR_DIFF_VEC:
      return 0;

    case CLOBBER:
      /* Reject CLOBBER with a non-VOID mode.  These are made by combine.c
	 when some combination can't be done.  If we see one, don't think
	 that we can simplify the expression.  */
      return (GET_MODE (x) != VOIDmode);

    case PRE_INC:
    case PRE_DEC:
    case POST_INC:
    case POST_DEC:
    case CALL:
    case UNSPEC_VOLATILE:
 /* case TRAP_IF: This isn't clear yet.  */
      return 1;

    case MEM:
    case ASM_OPERANDS:
      if (MEM_VOLATILE_P (x))
	return 1;

    default:
      break;
    }

  /* Recursively scan the operands of this expression.  */

  {
    register char *fmt = GET_RTX_FORMAT (code);
    register int i;
    
    for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
      {
	if (fmt[i] == 'e')
	  {
	    if (side_effects_p (XEXP (x, i)))
	      return 1;
	  }
	if (fmt[i] == 'E')
	  {
	    register int j;
	    for (j = 0; j < XVECLEN (x, i); j++)
	      if (side_effects_p (XVECEXP (x, i, j)))
		return 1;
	  }
      }
  }
  return 0;
}

/* Return nonzero if evaluating rtx X might cause a trap.  */

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

  if (x == 0)
    return 0;
  code = GET_CODE (x);
  switch (code)
    {
      /* Handle these cases quickly.  */
    case CONST_INT:
    case CONST_DOUBLE:
    case SYMBOL_REF:
    case LABEL_REF:
    case CONST:
    case PC:
    case CC0:
    case REG:
    case SCRATCH:
      return 0;

      /* Conditional trap can trap!  */
    case UNSPEC_VOLATILE:
    case TRAP_IF:
      return 1;

      /* Memory ref can trap unless it's a static var or a stack slot.  */
    case MEM:
      return rtx_addr_can_trap_p (XEXP (x, 0));

      /* Division by a non-constant might trap.  */
    case DIV:
    case MOD:
    case UDIV:
    case UMOD:
      if (! CONSTANT_P (XEXP (x, 1))
	  || GET_MODE_CLASS (GET_MODE (x)) == MODE_FLOAT)
	return 1;
      /* This was const0_rtx, but by not using that,
	 we can link this file into other programs.  */
      if (GET_CODE (XEXP (x, 1)) == CONST_INT && INTVAL (XEXP (x, 1)) == 0)
	return 1;
      break;

    case EXPR_LIST:
      /* An EXPR_LIST is used to represent a function call.  This
	 certainly may trap.  */
      return 1;

    default:
      /* Any floating arithmetic may trap.  */
      if (GET_MODE_CLASS (GET_MODE (x)) == MODE_FLOAT)
	return 1;
    }

  fmt = GET_RTX_FORMAT (code);
  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
    {
      if (fmt[i] == 'e')
	{
	  if (may_trap_p (XEXP (x, i)))
	    return 1;
	}
      else if (fmt[i] == 'E')
	{
	  register int j;
	  for (j = 0; j < XVECLEN (x, i); j++)
	    if (may_trap_p (XVECEXP (x, i, j)))
	      return 1;
	}
    }
  return 0;
}

/* Return nonzero if X contains a comparison that is not either EQ or NE,
   i.e., an inequality.  */

int
inequality_comparisons_p (x)
     rtx x;
{
  register char *fmt;
  register int len, i;
  register enum rtx_code code = GET_CODE (x);

  switch (code)
    {
    case REG:
    case SCRATCH:
    case PC:
    case CC0:
    case CONST_INT:
    case CONST_DOUBLE:
    case CONST:
    case LABEL_REF:
    case SYMBOL_REF:
      return 0;

    case LT:
    case LTU:
    case GT:
    case GTU:
    case LE:
    case LEU:
    case GE:
    case GEU:
      return 1;
      
    default:
      break;
    }

  len = GET_RTX_LENGTH (code);
  fmt = GET_RTX_FORMAT (code);

  for (i = 0; i < len; i++)
    {
      if (fmt[i] == 'e')
	{
	  if (inequality_comparisons_p (XEXP (x, i)))
	    return 1;
	}
      else if (fmt[i] == 'E')
	{
	  register int j;
	  for (j = XVECLEN (x, i) - 1; j >= 0; j--)
	    if (inequality_comparisons_p (XVECEXP (x, i, j)))
	      return 1;
	}
    }
	    
  return 0;
}

/* Replace any occurrence of FROM in X with TO.

   Note that copying is not done so X must not be shared unless all copies
   are to be modified.  */

rtx
replace_rtx (x, from, to)
     rtx x, from, to;
{
  register int i, j;
  register char *fmt;

  if (x == from)
    return to;

  /* Allow this function to make replacements in EXPR_LISTs.  */
  if (x == 0)
    return 0;

  fmt = GET_RTX_FORMAT (GET_CODE (x));
  for (i = GET_RTX_LENGTH (GET_CODE (x)) - 1; i >= 0; i--)
    {
      if (fmt[i] == 'e')
	XEXP (x, i) = replace_rtx (XEXP (x, i), from, to);
      else if (fmt[i] == 'E')
	for (j = XVECLEN (x, i) - 1; j >= 0; j--)
	  XVECEXP (x, i, j) = replace_rtx (XVECEXP (x, i, j), from, to);
    }

  return x;
}  

/* Throughout the rtx X, replace many registers according to REG_MAP.
   Return the replacement for X (which may be X with altered contents).
   REG_MAP[R] is the replacement for register R, or 0 for don't replace.
   NREGS is the length of REG_MAP; regs >= NREGS are not mapped.  

   We only support REG_MAP entries of REG or SUBREG.  Also, hard registers
   should not be mapped to pseudos or vice versa since validate_change
   is not called.

   If REPLACE_DEST is 1, replacements are also done in destinations;
   otherwise, only sources are replaced.  */

rtx
replace_regs (x, reg_map, nregs, replace_dest)
     rtx x;
     rtx *reg_map;
     int nregs;
     int replace_dest;
{
  register enum rtx_code code;
  register int i;
  register char *fmt;

  if (x == 0)
    return x;

  code = GET_CODE (x);
  switch (code)
    {
    case SCRATCH:
    case PC:
    case CC0:
    case CONST_INT:
    case CONST_DOUBLE:
    case CONST:
    case SYMBOL_REF:
    case LABEL_REF:
      return x;

    case REG:
      /* Verify that the register has an entry before trying to access it.  */
      if (REGNO (x) < nregs && reg_map[REGNO (x)] != 0)
	{
	  /* SUBREGs can't be shared.  Always return a copy to ensure that if
	     this replacement occurs more than once then each instance will
	     get distinct rtx.  */
	  if (GET_CODE (reg_map[REGNO (x)]) == SUBREG)
	    return copy_rtx (reg_map[REGNO (x)]);
	  return reg_map[REGNO (x)];
	}
      return x;

    case SUBREG:
      /* Prevent making nested SUBREGs.  */
      if (GET_CODE (SUBREG_REG (x)) == REG && REGNO (SUBREG_REG (x)) < nregs
	  && reg_map[REGNO (SUBREG_REG (x))] != 0
	  && GET_CODE (reg_map[REGNO (SUBREG_REG (x))]) == SUBREG)
	{
	  rtx map_val = reg_map[REGNO (SUBREG_REG (x))];
	  rtx map_inner = SUBREG_REG (map_val);

	  if (GET_MODE (x) == GET_MODE (map_inner))
	    return map_inner;
	  else
	    {
	      /* We cannot call gen_rtx here since we may be linked with
		 genattrtab.c.  */
	      /* Let's try clobbering the incoming SUBREG and see
		 if this is really safe.  */
	      SUBREG_REG (x) = map_inner;
	      SUBREG_WORD (x) += SUBREG_WORD (map_val);
	      return x;
#if 0
	      rtx new = rtx_alloc (SUBREG);
	      PUT_MODE (new, GET_MODE (x));
	      SUBREG_REG (new) = map_inner;
	      SUBREG_WORD (new) = SUBREG_WORD (x) + SUBREG_WORD (map_val);
#endif
	    }
	}
      break;

    case SET:
      if (replace_dest)
	SET_DEST (x) = replace_regs (SET_DEST (x), reg_map, nregs, 0);

      else if (GET_CODE (SET_DEST (x)) == MEM
	       || GET_CODE (SET_DEST (x)) == STRICT_LOW_PART)
	/* Even if we are not to replace destinations, replace register if it
	   is CONTAINED in destination (destination is memory or
	   STRICT_LOW_PART).  */
	XEXP (SET_DEST (x), 0) = replace_regs (XEXP (SET_DEST (x), 0),
					       reg_map, nregs, 0);
      else if (GET_CODE (SET_DEST (x)) == ZERO_EXTRACT)
	/* Similarly, for ZERO_EXTRACT we replace all operands.  */
	break;

      SET_SRC (x) = replace_regs (SET_SRC (x), reg_map, nregs, 0);
      return x;
      
    default:
      break;
    }

  fmt = GET_RTX_FORMAT (code);
  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
    {
      if (fmt[i] == 'e')
	XEXP (x, i) = replace_regs (XEXP (x, i), reg_map, nregs, replace_dest);
      if (fmt[i] == 'E')
	{
	  register int j;
	  for (j = 0; j < XVECLEN (x, i); j++)
	    XVECEXP (x, i, j) = replace_regs (XVECEXP (x, i, j), reg_map,
					      nregs, replace_dest);
	}
    }
  return x;
}

/* Return 1 if X, the SRC_SRC of  SET of (pc) contain a REG or MEM that is
   not in the constant pool and not in the condition of an IF_THEN_ELSE.  */

static int
jmp_uses_reg_or_mem (x)
     rtx x;
{
  enum rtx_code code = GET_CODE (x);
  int i, j;
  char *fmt;

  switch (code)
    {
    case CONST:
    case LABEL_REF:
    case PC:
      return 0;

    case REG:
      return 1;

    case MEM:
      return ! (GET_CODE (XEXP (x, 0)) == SYMBOL_REF
		&& CONSTANT_POOL_ADDRESS_P (XEXP (x, 0)));

    case IF_THEN_ELSE:
      return (jmp_uses_reg_or_mem (XEXP (x, 1))
	      || jmp_uses_reg_or_mem (XEXP (x, 2)));

    case PLUS:  case MINUS:  case MULT:
      return (jmp_uses_reg_or_mem (XEXP (x, 0))
	      || jmp_uses_reg_or_mem (XEXP (x, 1)));
    }

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

      if (fmt[i] == 'E')
	for (j = 0; j < XVECLEN (x, i); j++)
	  if (jmp_uses_reg_or_mem (XVECEXP (x, i, j)))
	    return 1;
    }

  return 0;
}

/* Return nonzero if INSN is an indirect jump (aka computed jump).

   Tablejumps and casesi insns are not considered indirect jumps;
   we can recognize them by a (use (lael_ref)).  */

int
computed_jump_p (insn)
     rtx insn;
{
  int i;
  if (GET_CODE (insn) == JUMP_INSN)
    {
      rtx pat = PATTERN (insn);
      int computed_jump = 0;

      if (GET_CODE (pat) == PARALLEL)
	{
	  int len = XVECLEN (pat, 0);
	  int has_use_labelref = 0;

	  for (i = len - 1; i >= 0; i--)
	    if (GET_CODE (XVECEXP (pat, 0, i)) == USE
		&& (GET_CODE (XEXP (XVECEXP (pat, 0, i), 0))
		    == LABEL_REF))
	      has_use_labelref = 1;

	  if (! has_use_labelref)
	    for (i = len - 1; i >= 0; i--)
	      if (GET_CODE (XVECEXP (pat, 0, i)) == SET
		  && SET_DEST (XVECEXP (pat, 0, i)) == pc_rtx
		  && jmp_uses_reg_or_mem (SET_SRC (XVECEXP (pat, 0, i))))
		return 1;
	}
      else if (GET_CODE (pat) == SET
	       && SET_DEST (pat) == pc_rtx
	       && jmp_uses_reg_or_mem (SET_SRC (pat)))
	return 1;
    }
  return 0;
}