reg-stack.c

早期freebsd实现

  return pat;
}

/* Scan the OPERANDS and OPERAND_CONSTRAINTS of an asm_operands.
   N_OPERANDS is the total number of operands.  Return which alternative
   matched, or -1 is no alternative matches.

   OPERAND_MATCHES is an array which indicates which operand this
   operand matches due to the constraints, or -1 if no match is required.
   If two operands match by coincidence, but are not required to match by
   the constraints, -1 is returned.

   OPERAND_CLASS is an array which indicates the smallest class
   required by the constraints.  If the alternative that matches calls
   for some class `class', and the operand matches a subclass of `class',
   OPERAND_CLASS is set to `class' as required by the constraints, not to
   the subclass. If an alternative allows more than one class,
   OPERAND_CLASS is set to the smallest class that is a union of the
   allowed classes. */

static int
constrain_asm_operands (n_operands, operands, operand_constraints,
			operand_matches, operand_class)
     int n_operands;
     rtx *operands;
     char **operand_constraints;
     int *operand_matches;
     enum reg_class *operand_class;
{
  char **constraints = (char **) alloca (n_operands * sizeof (char *));
  char *q;
  int this_alternative, this_operand;
  int n_alternatives;
  int j;

  for (j = 0; j < n_operands; j++)
    constraints[j] = operand_constraints[j];

  /* Compute the number of alternatives in the operands.  reload has
     already guaranteed that all operands have the same number of
     alternatives.  */

  n_alternatives = 1;
  for (q = constraints[0]; *q; q++)
    n_alternatives += (*q == ',');

  this_alternative = 0;
  while (this_alternative < n_alternatives)
    {
      int lose = 0;
      int i;

      /* No operands match, no narrow class requirements yet.  */
      for (i = 0; i < n_operands; i++)
	{
	  operand_matches[i] = -1;
	  operand_class[i] = NO_REGS;
	}

      for (this_operand = 0; this_operand < n_operands; this_operand++)
	{
	  rtx op = operands[this_operand];
	  enum machine_mode mode = GET_MODE (op);
	  char *p = constraints[this_operand];
	  int offset = 0;
	  int win = 0;
	  int c;

	  if (GET_CODE (op) == SUBREG)
	    {
	      if (GET_CODE (SUBREG_REG (op)) == REG
		  && REGNO (SUBREG_REG (op)) < FIRST_PSEUDO_REGISTER)
		offset = SUBREG_WORD (op);
	      op = SUBREG_REG (op);
	    }

	  /* An empty constraint or empty alternative
	     allows anything which matched the pattern.  */
	  if (*p == 0 || *p == ',')
	    win = 1;

	  while (*p && (c = *p++) != ',')
	    switch (c)
	      {
	      case '=':
	      case '+':
	      case '?':
	      case '&':
	      case '!':
	      case '*':
	      case '%':
		/* Ignore these. */
		break;

	      case '#':
		/* Ignore rest of this alternative. */
		while (*p && *p != ',') p++;
		break;

	      case '0':
	      case '1':
	      case '2':
	      case '3':
	      case '4':
	      case '5':
		/* This operand must be the same as a previous one.
		   This kind of constraint is used for instructions such
		   as add when they take only two operands.

		   Note that the lower-numbered operand is passed first. */

		if (operands_match_p (operands[c - '0'],
				      operands[this_operand]))
		  {
		    operand_matches[this_operand] = c - '0';
		    win = 1;
		  }
		break;

	      case 'p':
		/* p is used for address_operands.  Since this is an asm,
		   just to make sure that the operand is valid for Pmode. */

		if (strict_memory_address_p (Pmode, op))
		  win = 1;
		break;

	      case 'g':
		/* Anything goes unless it is a REG and really has a hard reg
		   but the hard reg is not in the class GENERAL_REGS.  */
		if (GENERAL_REGS == ALL_REGS
		    || GET_CODE (op) != REG
		    || reg_fits_class_p (op, GENERAL_REGS, offset, mode))
		  {
		    if (GET_CODE (op) == REG)
		      operand_class[this_operand]
			= reg_class_subunion[(int) operand_class[this_operand]][(int) GENERAL_REGS];
		    win = 1;
		  }
		break;

	      case 'r':
		if (GET_CODE (op) == REG
		    && (GENERAL_REGS == ALL_REGS
			|| reg_fits_class_p (op, GENERAL_REGS, offset, mode)))
		  {
		    operand_class[this_operand]
		      = reg_class_subunion[(int) operand_class[this_operand]][(int) GENERAL_REGS];
		    win = 1;
		  }
		break;

	      case 'X':
		/* This is used for a MATCH_SCRATCH in the cases when we
		   don't actually need anything.  So anything goes any time. */
		win = 1;
		break;

	      case 'm':
		if (GET_CODE (op) == MEM)
		  win = 1;
		break;

	      case '<':
		if (GET_CODE (op) == MEM
		    && (GET_CODE (XEXP (op, 0)) == PRE_DEC
			|| GET_CODE (XEXP (op, 0)) == POST_DEC))
		  win = 1;
		break;

	      case '>':
		if (GET_CODE (op) == MEM
		    && (GET_CODE (XEXP (op, 0)) == PRE_INC
			|| GET_CODE (XEXP (op, 0)) == POST_INC))
		  win = 1;
		break;

	      case 'E':
		/* Match any CONST_DOUBLE, but only if
		   we can examine the bits of it reliably.  */
		if ((HOST_FLOAT_FORMAT != TARGET_FLOAT_FORMAT
		     || HOST_BITS_PER_WIDE_INT != BITS_PER_WORD)
		    && GET_CODE (op) != VOIDmode && ! flag_pretend_float)
		  break;
		if (GET_CODE (op) == CONST_DOUBLE)
		  win = 1;
		break;

	      case 'F':
		if (GET_CODE (op) == CONST_DOUBLE)
		  win = 1;
		break;

	      case 'G':
	      case 'H':
		if (GET_CODE (op) == CONST_DOUBLE
		    && CONST_DOUBLE_OK_FOR_LETTER_P (op, c))
		  win = 1;
		break;

	      case 's':
		if (GET_CODE (op) == CONST_INT
		    || (GET_CODE (op) == CONST_DOUBLE
			&& GET_MODE (op) == VOIDmode))
		  break;
		/* Fall through */
	      case 'i':
		if (CONSTANT_P (op))
		  win = 1;
		break;

	      case 'n':
		if (GET_CODE (op) == CONST_INT
		    || (GET_CODE (op) == CONST_DOUBLE
			&& GET_MODE (op) == VOIDmode))
		  win = 1;
		break;

	      case 'I':
	      case 'J':
	      case 'K':
	      case 'L':
	      case 'M':
	      case 'N':
	      case 'O':
	      case 'P':
		if (GET_CODE (op) == CONST_INT
		    && CONST_OK_FOR_LETTER_P (INTVAL (op), c))
		  win = 1;
		break;

#ifdef EXTRA_CONSTRAINT
              case 'Q':
              case 'R':
              case 'S':
              case 'T':
              case 'U':
		if (EXTRA_CONSTRAINT (op, c))
		  win = 1;
		break;
#endif

	      case 'V':
		if (GET_CODE (op) == MEM && ! offsettable_memref_p (op))
		  win = 1;
		break;

	      case 'o':
		if (offsettable_memref_p (op))
		  win = 1;
		break;

	      default:
		if (GET_CODE (op) == REG
		    && reg_fits_class_p (op, REG_CLASS_FROM_LETTER (c),
					 offset, mode))
		  {
		    operand_class[this_operand]
		      = reg_class_subunion[(int)operand_class[this_operand]][(int) REG_CLASS_FROM_LETTER (c)];
		    win = 1;
		  }
	      }

	  constraints[this_operand] = p;
	  /* If this operand did not win somehow,
	     this alternative loses.  */
	  if (! win)
	    lose = 1;
	}
      /* This alternative won; the operands are ok.
	 Change whichever operands this alternative says to change.  */
      if (! lose)
	break;

      this_alternative++;
    }

  /* For operands constrained to match another operand, copy the other
     operand's class to this operand's class. */
  for (j = 0; j < n_operands; j++)
    if (operand_matches[j] >= 0)
      operand_class[j] = operand_class[operand_matches[j]];

  return this_alternative == n_alternatives ? -1 : this_alternative;
}

/* Record the life info of each stack reg in INSN, updating REGSTACK.
   N_INPUTS is the number of inputs; N_OUTPUTS the outputs.  CONSTRAINTS
   is an array of the constraint strings used in the asm statement.
   OPERANDS is an array of all operands for the insn, and is assumed to
   contain all output operands, then all inputs operands.

   There are many rules that an asm statement for stack-like regs must
   follow.  Those rules are explained at the top of this file: the rule
   numbers below refer to that explanation. */

static void
record_asm_reg_life (insn, regstack, operands, constraints,
		     n_inputs, n_outputs)
     rtx insn;
     stack regstack;
     rtx *operands;
     char **constraints;
     int n_inputs, n_outputs;
{
  int i;
  int n_operands = n_inputs + n_outputs;
  int first_input = n_outputs;
  int n_clobbers;
  int malformed_asm = 0;
  rtx body = PATTERN (insn);

  int *operand_matches = (int *) alloca (n_operands * sizeof (int *));

  enum reg_class *operand_class 
    = (enum reg_class *) alloca (n_operands * sizeof (enum reg_class *));

  int reg_used_as_output[FIRST_PSEUDO_REGISTER];
  int implicitly_dies[FIRST_PSEUDO_REGISTER];

  rtx *clobber_reg;

  /* Find out what the constraints require.  If no constraint
     alternative matches, that is a compiler bug: we should have caught
     such an insn during reload.  */
  i = constrain_asm_operands (n_operands, operands, constraints,
			      operand_matches, operand_class);
  if (i < 0)
    abort ();

  /* Strip SUBREGs here to make the following code simpler. */
  for (i = 0; i < n_operands; i++)
    if (GET_CODE (operands[i]) == SUBREG
	&& GET_CODE (SUBREG_REG (operands[i])) == REG)
      operands[i] = SUBREG_REG (operands[i]);

  /* Set up CLOBBER_REG.  */

  n_clobbers = 0;

  if (GET_CODE (body) == PARALLEL)
    {
      clobber_reg = (rtx *) alloca (XVECLEN (body, 0) * sizeof (rtx *));

      for (i = 0; i < XVECLEN (body, 0); i++)
	if (GET_CODE (XVECEXP (body, 0, i)) == CLOBBER)
	  {
	    rtx clobber = XVECEXP (body, 0, i);
	    rtx reg = XEXP (clobber, 0);

	    if (GET_CODE (reg) == SUBREG && GET_CODE (SUBREG_REG (reg)) == REG)
	      reg = SUBREG_REG (reg);

	    if (STACK_REG_P (reg))
	      {
		clobber_reg[n_clobbers] = reg;
		n_clobbers++;
	      }
	  }
    }

  /* Enforce rule #4: Output operands must specifically indicate which
     reg an output appears in after an asm.  "=f" is not allowed: the
     operand constraints must select a class with a single reg.

     Also enforce rule #5: Output operands must start at the top of
     the reg-stack: output operands may not "skip" a reg. */

  bzero (reg_used_as_output, sizeof (reg_used_as_output));
  for (i = 0; i < n_outputs; i++)
    if (STACK_REG_P (operands[i]))
      if (reg_class_size[operand_class[i]] != 1)
	{
	  error_for_asm
	    (insn, "Output constraint %d must specify a single register", i);
	  malformed_asm = 1;
	}
      else
	reg_used_as_output[REGNO (operands[i])] = 1;


  /* Search for first non-popped reg.  */
  for (i = FIRST_STACK_REG; i < LAST_STACK_REG + 1; i++)
    if (! reg_used_as_output[i])
      break;

  /* If there are any other popped regs, that's an error.  */
  for (; i < LAST_STACK_REG + 1; i++)
    if (reg_used_as_output[i])
      break;

  if (i != LAST_STACK_REG + 1)
    {
      error_for_asm (insn, "Output regs must be grouped at top of stack");
      malformed_asm = 1;
    }

  /* Enforce rule #2: All implicitly popped input regs must be closer
     to the top of the reg-stack than any input that is not implicitly
     popped. */

  bzero (implicitly_dies, sizeof (implicitly_dies));
  for (i = first_input; i < first_input + n_inputs; i++)
    if (STACK_REG_P (operands[i]))
      {
	/* An input reg is implicitly popped if it is tied to an
	   output, or if there is a CLOBBER for it. */
	int j;

	for (j = 0; j < n_clobbers; j++)
	  if (operands_match_p (clobber_reg[j], operands[i]))
	    break;

	if (j < n_clobbers || operand_matches[i] >= 0)
	  implicitly_dies[REGNO (operands[i])] = 1;
      }

  /* Search for first non-popped reg.  */
  for (i = FIRST_STACK_REG; i < LAST_STACK_REG + 1; i++)
    if (! implicitly_dies[i])
      break;

  /* If there are any other popped regs, that's an error.  */
  for (; i < LAST_STACK_REG + 1; i++)
    if (implicitly_dies[i])
      break;

  if (i != LAST_STACK_REG + 1)
    {
      error_for_asm (insn,
		     "Implicitly popped regs must be grouped at top of stack");
      malformed_asm = 1;
    }

  /* Enfore rule #3: If any input operand uses the "f" constraint, all
     output constraints must use the "&" earlyclobber.

     ???  Detect this more deterministically by having constraint_asm_operands
     record any earlyclobber. */

  for (i = first_input; i < first_input + n_inputs; i++)
    if (operand_matches[i] == -1)
      {
	int j;