path: root/gcc/gensupport.c

/* Support routines for the various generation passes.
   Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,
   2010, Free Software Foundation, Inc.

   This file is part of GCC.

   GCC 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 3, or (at your option)
   any later version.

   GCC 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 GCC; see the file COPYING3.  If not see
   <http://www.gnu.org/licenses/>.  */

#include "bconfig.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "rtl.h"
#include "obstack.h"
#include "errors.h"
#include "hashtab.h"
#include "read-md.h"
#include "gensupport.h"


/* In case some macros used by files we include need it, define this here.  */
int target_flags;

int insn_elision = 1;

static struct obstack obstack;
struct obstack *rtl_obstack = &obstack;

static int sequence_num;

static int predicable_default;
static const char *predicable_true;
static const char *predicable_false;

static htab_t condition_table;

/* We initially queue all patterns, process the define_insn and
   define_cond_exec patterns, then return them one at a time.  */

struct queue_elem
{
  rtx data;
  const char *filename;
  int lineno;
  struct queue_elem *next;
  /* In a DEFINE_INSN that came from a DEFINE_INSN_AND_SPLIT, SPLIT
     points to the generated DEFINE_SPLIT.  */
  struct queue_elem *split;
};

#define MNEMONIC_ATTR_NAME "mnemonic"
#define MNEMONIC_HTAB_SIZE 1024

static struct queue_elem *define_attr_queue;
static struct queue_elem **define_attr_tail = &define_attr_queue;
static struct queue_elem *define_pred_queue;
static struct queue_elem **define_pred_tail = &define_pred_queue;
static struct queue_elem *define_insn_queue;
static struct queue_elem **define_insn_tail = &define_insn_queue;
static struct queue_elem *define_cond_exec_queue;
static struct queue_elem **define_cond_exec_tail = &define_cond_exec_queue;
static struct queue_elem *other_queue;
static struct queue_elem **other_tail = &other_queue;

static struct queue_elem *queue_pattern (rtx, struct queue_elem ***,
					 const char *, int);

static void remove_constraints (rtx);
static void process_rtx (rtx, int);

static int is_predicable (struct queue_elem *);
static void identify_predicable_attribute (void);
static int n_alternatives (const char *);
static void collect_insn_data (rtx, int *, int *);
static rtx alter_predicate_for_insn (rtx, int, int, int);
static const char *alter_test_for_insn (struct queue_elem *,
					struct queue_elem *);
static char *shift_output_template (char *, const char *, int);
static const char *alter_output_for_insn (struct queue_elem *,
					  struct queue_elem *,
					  int, int);
static void process_one_cond_exec (struct queue_elem *);
static void process_define_cond_exec (void);
static void init_predicate_table (void);
static void record_insn_name (int, const char *);

/* Make a version of gen_rtx_CONST_INT so that GEN_INT can be used in
   the gensupport programs.  */

rtx
gen_rtx_CONST_INT (enum machine_mode ARG_UNUSED (mode),
		   HOST_WIDE_INT arg)
{
  rtx rt = rtx_alloc (CONST_INT);

  XWINT (rt, 0) = arg;
  return rt;
}

/* Queue PATTERN on LIST_TAIL.  Return the address of the new queue
   element.  */

static struct queue_elem *
queue_pattern (rtx pattern, struct queue_elem ***list_tail,
	       const char *filename, int lineno)
{
  struct queue_elem *e = XNEW(struct queue_elem);
  e->data = pattern;
  e->filename = filename;
  e->lineno = lineno;
  e->next = NULL;
  e->split = NULL;
  **list_tail = e;
  *list_tail = &e->next;
  return e;
}

/* Recursively remove constraints from an rtx.  */

static void
remove_constraints (rtx part)
{
  int i, j;
  const char *format_ptr;

  if (part == 0)
    return;

  if (GET_CODE (part) == MATCH_OPERAND)
    XSTR (part, 2) = "";
  else if (GET_CODE (part) == MATCH_SCRATCH)
    XSTR (part, 1) = "";

  format_ptr = GET_RTX_FORMAT (GET_CODE (part));

  for (i = 0; i < GET_RTX_LENGTH (GET_CODE (part)); i++)
    switch (*format_ptr++)
      {
      case 'e':
      case 'u':
	remove_constraints (XEXP (part, i));
	break;
      case 'E':
	if (XVEC (part, i) != NULL)
	  for (j = 0; j < XVECLEN (part, i); j++)
	    remove_constraints (XVECEXP (part, i, j));
	break;
      }
}

/* Process a top level rtx in some way, queuing as appropriate.  */

static void
process_rtx (rtx desc, int lineno)
{
  switch (GET_CODE (desc))
    {
    case DEFINE_INSN:
      queue_pattern (desc, &define_insn_tail, read_md_filename, lineno);
      break;

    case DEFINE_COND_EXEC:
      queue_pattern (desc, &define_cond_exec_tail, read_md_filename, lineno);
      break;

    case DEFINE_ATTR:
    case DEFINE_ENUM_ATTR:
      queue_pattern (desc, &define_attr_tail, read_md_filename, lineno);
      break;

    case DEFINE_PREDICATE:
    case DEFINE_SPECIAL_PREDICATE:
    case DEFINE_CONSTRAINT:
    case DEFINE_REGISTER_CONSTRAINT:
    case DEFINE_MEMORY_CONSTRAINT:
    case DEFINE_ADDRESS_CONSTRAINT:
      queue_pattern (desc, &define_pred_tail, read_md_filename, lineno);
      break;

    case DEFINE_INSN_AND_SPLIT:
      {
	const char *split_cond;
	rtx split;
	rtvec attr;
	int i;
	struct queue_elem *insn_elem;
	struct queue_elem *split_elem;

	/* Create a split with values from the insn_and_split.  */
	split = rtx_alloc (DEFINE_SPLIT);

	i = XVECLEN (desc, 1);
	XVEC (split, 0) = rtvec_alloc (i);
	while (--i >= 0)
	  {
	    XVECEXP (split, 0, i) = copy_rtx (XVECEXP (desc, 1, i));
	    remove_constraints (XVECEXP (split, 0, i));
	  }

	/* If the split condition starts with "&&", append it to the
	   insn condition to create the new split condition.  */
	split_cond = XSTR (desc, 4);
	if (split_cond[0] == '&' && split_cond[1] == '&')
	  {
	    copy_md_ptr_loc (split_cond + 2, split_cond);
	    split_cond = join_c_conditions (XSTR (desc, 2), split_cond + 2);
	  }
	XSTR (split, 1) = split_cond;
	XVEC (split, 2) = XVEC (desc, 5);
	XSTR (split, 3) = XSTR (desc, 6);

	/* Fix up the DEFINE_INSN.  */
	attr = XVEC (desc, 7);
	PUT_CODE (desc, DEFINE_INSN);
	XVEC (desc, 4) = attr;

	/* Queue them.  */
	insn_elem
	  = queue_pattern (desc, &define_insn_tail, read_md_filename,
			   lineno);
	split_elem
	  = queue_pattern (split, &other_tail, read_md_filename, lineno);
	insn_elem->split = split_elem;
	break;
      }

    default:
      queue_pattern (desc, &other_tail, read_md_filename, lineno);
      break;
    }
}

/* Return true if attribute PREDICABLE is true for ELEM, which holds
   a DEFINE_INSN.  */

static int
is_predicable (struct queue_elem *elem)
{
  rtvec vec = XVEC (elem->data, 4);
  const char *value;
  int i;

  if (! vec)
    return predicable_default;

  for (i = GET_NUM_ELEM (vec) - 1; i >= 0; --i)
    {
      rtx sub = RTVEC_ELT (vec, i);
      switch (GET_CODE (sub))
	{
	case SET_ATTR:
	  if (strcmp (XSTR (sub, 0), "predicable") == 0)
	    {
	      value = XSTR (sub, 1);
	      goto found;
	    }
	  break;

	case SET_ATTR_ALTERNATIVE:
	  if (strcmp (XSTR (sub, 0), "predicable") == 0)
	    {
	      error_with_line (elem->lineno,
			       "multiple alternatives for `predicable'");
	      return 0;
	    }
	  break;

	case SET:
	  if (GET_CODE (SET_DEST (sub)) != ATTR
	      || strcmp (XSTR (SET_DEST (sub), 0), "predicable") != 0)
	    break;
	  sub = SET_SRC (sub);
	  if (GET_CODE (sub) == CONST_STRING)
	    {
	      value = XSTR (sub, 0);
	      goto found;
	    }

	  /* ??? It would be possible to handle this if we really tried.
	     It's not easy though, and I'm not going to bother until it
	     really proves necessary.  */
	  error_with_line (elem->lineno,
			   "non-constant value for `predicable'");
	  return 0;

	default:
	  gcc_unreachable ();
	}
    }

  return predicable_default;

 found:
  /* Verify that predicability does not vary on the alternative.  */
  /* ??? It should be possible to handle this by simply eliminating
     the non-predicable alternatives from the insn.  FRV would like
     to do this.  Delay this until we've got the basics solid.  */
  if (strchr (value, ',') != NULL)
    {
      error_with_line (elem->lineno, "multiple alternatives for `predicable'");
      return 0;
    }

  /* Find out which value we're looking at.  */
  if (strcmp (value, predicable_true) == 0)
    return 1;
  if (strcmp (value, predicable_false) == 0)
    return 0;

  error_with_line (elem->lineno,
		   "unknown value `%s' for `predicable' attribute", value);
  return 0;
}

/* Examine the attribute "predicable"; discover its boolean values
   and its default.  */

static void
identify_predicable_attribute (void)
{
  struct queue_elem *elem;
  char *p_true, *p_false;
  const char *value;

  /* Look for the DEFINE_ATTR for `predicable', which must exist.  */
  for (elem = define_attr_queue; elem ; elem = elem->next)
    if (strcmp (XSTR (elem->data, 0), "predicable") == 0)
      goto found;

  error_with_line (define_cond_exec_queue->lineno,
		   "attribute `predicable' not defined");
  return;

 found:
  value = XSTR (elem->data, 1);
  p_false = xstrdup (value);
  p_true = strchr (p_false, ',');
  if (p_true == NULL || strchr (++p_true, ',') != NULL)
    {
      error_with_line (elem->lineno, "attribute `predicable' is not a boolean");
      if (p_false)
        free (p_false);
      return;
    }
  p_true[-1] = '\0';

  predicable_true = p_true;
  predicable_false = p_false;

  switch (GET_CODE (XEXP (elem->data, 2)))
    {
    case CONST_STRING:
      value = XSTR (XEXP (elem->data, 2), 0);
      break;

    case CONST:
      error_with_line (elem->lineno, "attribute `predicable' cannot be const");
      if (p_false)
	free (p_false);
      return;

    default:
      error_with_line (elem->lineno,
		       "attribute `predicable' must have a constant default");
      if (p_false)
	free (p_false);
      return;
    }

  if (strcmp (value, p_true) == 0)
    predicable_default = 1;
  else if (strcmp (value, p_false) == 0)
    predicable_default = 0;
  else
    {
      error_with_line (elem->lineno,
		       "unknown value `%s' for `predicable' attribute", value);
      if (p_false)
	free (p_false);
    }
}

/* Return the number of alternatives in constraint S.  */

static int
n_alternatives (const char *s)
{
  int n = 1;

  if (s)
    while (*s)
      n += (*s++ == ',');

  return n;
}

/* Determine how many alternatives there are in INSN, and how many
   operands.  */

static void
collect_insn_data (rtx pattern, int *palt, int *pmax)
{
  const char *fmt;
  enum rtx_code code;
  int i, j, len;

  code = GET_CODE (pattern);
  switch (code)
    {
    case MATCH_OPERAND:
      i = n_alternatives (XSTR (pattern, 2));
      *palt = (i > *palt ? i : *palt);
      /* Fall through.  */

    case MATCH_OPERATOR:
    case MATCH_SCRATCH:
    case MATCH_PARALLEL:
      i = XINT (pattern, 0);
      if (i > *pmax)
	*pmax = i;
      break;

    default:
      break;
    }

  fmt = GET_RTX_FORMAT (code);
  len = GET_RTX_LENGTH (code);
  for (i = 0; i < len; i++)
    {
      switch (fmt[i])
	{
	case 'e': case 'u':
	  collect_insn_data (XEXP (pattern, i), palt, pmax);
	  break;

	case 'V':
	  if (XVEC (pattern, i) == NULL)
	    break;
	  /* Fall through.  */
	case 'E':
	  for (j = XVECLEN (pattern, i) - 1; j >= 0; --j)
	    collect_insn_data (XVECEXP (pattern, i, j), palt, pmax);
	  break;

	case 'i': case 'w': case '0': case 's': case 'S': case 'T':
	  break;

	default:
	  gcc_unreachable ();
	}
    }
}

static rtx
alter_predicate_for_insn (rtx pattern, int alt, int max_op, int lineno)
{
  const char *fmt;
  enum rtx_code code;
  int i, j, len;

  code = GET_CODE (pattern);
  switch (code)
    {
    case MATCH_OPERAND:
      {
	const char *c = XSTR (pattern, 2);

	if (n_alternatives (c) != 1)
	  {
	    error_with_line (lineno, "too many alternatives for operand %d",
			     XINT (pattern, 0));
	    return NULL;
	  }

	/* Replicate C as needed to fill out ALT alternatives.  */
	if (c && *c && alt > 1)
	  {
	    size_t c_len = strlen (c);
	    size_t len = alt * (c_len + 1);
	    char *new_c = XNEWVEC(char, len);

	    memcpy (new_c, c, c_len);
	    for (i = 1; i < alt; ++i)
	      {
		new_c[i * (c_len + 1) - 1] = ',';
		memcpy (&new_c[i * (c_len + 1)], c, c_len);
	      }
	    new_c[len - 1] = '\0';
	    XSTR (pattern, 2) = new_c;
	  }
      }
      /* Fall through.  */

    case MATCH_OPERATOR:
    case MATCH_SCRATCH:
    case MATCH_PARALLEL:
      XINT (pattern, 0) += max_op;
      break;

    default:
      break;
    }

  fmt = GET_RTX_FORMAT (code);
  len = GET_RTX_LENGTH (code);
  for (i = 0; i < len; i++)
    {
      rtx r;

      switch (fmt[i])
	{
	case 'e': case 'u':
	  r = alter_predicate_for_insn (XEXP (pattern, i), alt,
					max_op, lineno);
	  if (r == NULL)
	    return r;
	  break;

	case 'E':
	  for (j = XVECLEN (pattern, i) - 1; j >= 0; --j)
	    {
	      r = alter_predicate_for_insn (XVECEXP (pattern, i, j),
					    alt, max_op, lineno);
	      if (r == NULL)
		return r;
	    }
	  break;

	case 'i': case 'w': case '0': case 's':
	  break;

	default:
	  gcc_unreachable ();
	}
    }

  return pattern;
}

static const char *
alter_test_for_insn (struct queue_elem *ce_elem,
		     struct queue_elem *insn_elem)
{
  return join_c_conditions (XSTR (ce_elem->data, 1),
			    XSTR (insn_elem->data, 2));
}

/* Adjust all of the operand numbers in SRC to match the shift they'll
   get from an operand displacement of DISP.  Return a pointer after the
   adjusted string.  */

static char *
shift_output_template (char *dest, const char *src, int disp)
{
  while (*src)
    {
      char c = *src++;
      *dest++ = c;
      if (c == '%')
	{
	  c = *src++;
	  if (ISDIGIT ((unsigned char) c))
	    c += disp;
	  else if (ISALPHA (c))
	    {
	      *dest++ = c;
	      c = *src++ + disp;
	    }
	  *dest++ = c;
	}
    }

  return dest;
}

static const char *
alter_output_for_insn (struct queue_elem *ce_elem,
		       struct queue_elem *insn_elem,
		       int alt, int max_op)
{
  const char *ce_out, *insn_out;
  char *result, *p;
  size_t len, ce_len, insn_len;

  /* ??? Could coordinate with genoutput to not duplicate code here.  */

  ce_out = XSTR (ce_elem->data, 2);
  insn_out = XTMPL (insn_elem->data, 3);
  if (!ce_out || *ce_out == '\0')
    return insn_out;

  ce_len = strlen (ce_out);
  insn_len = strlen (insn_out);

  if (*insn_out == '*')
    /* You must take care of the predicate yourself.  */
    return insn_out;

  if (*insn_out == '@')
    {
      len = (ce_len + 1) * alt + insn_len + 1;
      p = result = XNEWVEC(char, len);

      do
	{
	  do
	    *p++ = *insn_out++;
	  while (ISSPACE ((unsigned char) *insn_out));

	  if (*insn_out != '#')
	    {
	      p = shift_output_template (p, ce_out, max_op);
	      *p++ = ' ';
	    }

	  do
	    *p++ = *insn_out++;
	  while (*insn_out && *insn_out != '\n');
	}
      while (*insn_out);
      *p = '\0';
    }
  else
    {
      len = ce_len + 1 + insn_len + 1;
      result = XNEWVEC (char, len);

      p = shift_output_template (result, ce_out, max_op);
      *p++ = ' ';
      memcpy (p, insn_out, insn_len + 1);
    }

  return result;
}

/* Replicate insns as appropriate for the given DEFINE_COND_EXEC.  */

static void
process_one_cond_exec (struct queue_elem *ce_elem)
{
  struct queue_elem *insn_elem;
  for (insn_elem = define_insn_queue; insn_elem ; insn_elem = insn_elem->next)
    {
      int alternatives, max_operand;
      rtx pred, insn, pattern, split;
      char *new_name;
      int i;

      if (! is_predicable (insn_elem))
	continue;

      alternatives = 1;
      max_operand = -1;
      collect_insn_data (insn_elem->data, &alternatives, &max_operand);
      max_operand += 1;

      if (XVECLEN (ce_elem->data, 0) != 1)
	{
	  error_with_line (ce_elem->lineno, "too many patterns in predicate");
	  return;
	}

      pred = copy_rtx (XVECEXP (ce_elem->data, 0, 0));
      pred = alter_predicate_for_insn (pred, alternatives, max_operand,
				       ce_elem->lineno);
      if (pred == NULL)
	return;

      /* Construct a new pattern for the new insn.  */
      insn = copy_rtx (insn_elem->data);
      new_name = XNEWVAR (char, strlen XSTR (insn_elem->data, 0) + 4);
      sprintf (new_name, "*p %s", XSTR (insn_elem->data, 0));
      XSTR (insn, 0) = new_name;
      pattern = rtx_alloc (COND_EXEC);
      XEXP (pattern, 0) = pred;
      if (XVECLEN (insn, 1) == 1)
	{
	  XEXP (pattern, 1) = XVECEXP (insn, 1, 0);
	  XVECEXP (insn, 1, 0) = pattern;
	  PUT_NUM_ELEM (XVEC (insn, 1), 1);
	}
      else
	{
	  XEXP (pattern, 1) = rtx_alloc (PARALLEL);
	  XVEC (XEXP (pattern, 1), 0) = XVEC (insn, 1);
	  XVEC (insn, 1) = rtvec_alloc (1);
	  XVECEXP (insn, 1, 0) = pattern;
	}

      XSTR (insn, 2) = alter_test_for_insn (ce_elem, insn_elem);
      XTMPL (insn, 3) = alter_output_for_insn (ce_elem, insn_elem,
					      alternatives, max_operand);

      /* ??? Set `predicable' to false.  Not crucial since it's really
         only used here, and we won't reprocess this new pattern.  */

      /* Put the new pattern on the `other' list so that it
	 (a) is not reprocessed by other define_cond_exec patterns
	 (b) appears after all normal define_insn patterns.

	 ??? B is debatable.  If one has normal insns that match
	 cond_exec patterns, they will be preferred over these
	 generated patterns.  Whether this matters in practice, or if
	 it's a good thing, or whether we should thread these new
	 patterns into the define_insn chain just after their generator
	 is something we'll have to experiment with.  */

      queue_pattern (insn, &other_tail, insn_elem->filename,
		     insn_elem->lineno);

      if (!insn_elem->split)
	continue;

      /* If the original insn came from a define_insn_and_split,
	 generate a new split to handle the predicated insn.  */
      split = copy_rtx (insn_elem->split->data);
      /* Predicate the pattern matched by the split.  */
      pattern = rtx_alloc (COND_EXEC);
      XEXP (pattern, 0) = pred;
      if (XVECLEN (split, 0) == 1)
	{
	  XEXP (pattern, 1) = XVECEXP (split, 0, 0);
	  XVECEXP (split, 0, 0) = pattern;
	  PUT_NUM_ELEM (XVEC (split, 0), 1);
	}
      else
	{
	  XEXP (pattern, 1) = rtx_alloc (PARALLEL);
	  XVEC (XEXP (pattern, 1), 0) = XVEC (split, 0);
	  XVEC (split, 0) = rtvec_alloc (1);
	  XVECEXP (split, 0, 0) = pattern;
	}
      /* Predicate all of the insns generated by the split.  */
      for (i = 0; i < XVECLEN (split, 2); i++)
	{
	  pattern = rtx_alloc (COND_EXEC);
	  XEXP (pattern, 0) = pred;
	  XEXP (pattern, 1) = XVECEXP (split, 2, i);
	  XVECEXP (split, 2, i) = pattern;
	}
      /* Add the new split to the queue.  */
      queue_pattern (split, &other_tail, read_md_filename,
		     insn_elem->split->lineno);
    }
}

/* If we have any DEFINE_COND_EXEC patterns, expand the DEFINE_INSN
   patterns appropriately.  */

static void
process_define_cond_exec (void)
{
  struct queue_elem *elem;

  identify_predicable_attribute ();
  if (have_error)
    return;

  for (elem = define_cond_exec_queue; elem ; elem = elem->next)
    process_one_cond_exec (elem);
}

/* A read_md_files callback for reading an rtx.  */

static void
rtx_handle_directive (int lineno, const char *rtx_name)
{
  rtx queue, x;

  if (read_rtx (rtx_name, &queue))
    for (x = queue; x; x = XEXP (x, 1))
      process_rtx (XEXP (x, 0), lineno);
}

/* Comparison function for the mnemonic hash table.  */

static int
htab_eq_string (const void *s1, const void *s2)
{
  return strcmp ((const char*)s1, (const char*)s2) == 0;
}

/* Add mnemonic STR with length LEN to the mnemonic hash table
   MNEMONIC_HTAB.  A trailing zero end character is appendend to STR
   and a permanent heap copy of STR is created.  */

static void
add_mnemonic_string (htab_t mnemonic_htab, const char *str, int len)
{
  char *new_str;
  void **slot;
  char *str_zero = (char*)alloca (len + 1);

  memcpy (str_zero, str, len);
  str_zero[len] = '\0';

  slot = htab_find_slot (mnemonic_htab, str_zero, INSERT);

  if (*slot)
    return;

  /* Not found; create a permanent copy and add it to the hash table.  */
  new_str = XNEWVAR (char, len + 1);
  memcpy (new_str, str_zero, len + 1);
  *slot = new_str;
}

/* Scan INSN for mnemonic strings and add them to the mnemonic hash
   table in MNEMONIC_HTAB.

   The mnemonics cannot be found if they are emitted using C code.

   If a mnemonic string contains ';' or a newline the string assumed
   to consist of more than a single instruction.  The attribute value
   will then be set to the user defined default value.  */

static void
gen_mnemonic_setattr (htab_t mnemonic_htab, rtx insn)
{
  const char *template_code, *cp;
  int i;
  int vec_len;
  rtx set_attr;
  char *attr_name;
  rtvec new_vec;

  template_code = XTMPL (insn, 3);

  /* Skip patterns which use C code to emit the template.  */
  if (template_code[0] == '*')
    return;

  if (template_code[0] == '@')
    cp = &template_code[1];
  else
    cp = &template_code[0];

  for (i = 0; *cp; )
    {
      const char *ep, *sp;
      int size = 0;

      while (ISSPACE (*cp))
	cp++;

      for (ep = sp = cp; !IS_VSPACE (*ep) && *ep != '\0'; ++ep)
	if (!ISSPACE (*ep))
	  sp = ep + 1;

      if (i > 0)
	obstack_1grow (&string_obstack, ',');

      while (cp < sp && ((*cp >= '0' && *cp <= '9')
			 || (*cp >= 'a' && *cp <= 'z')))

	{
	  obstack_1grow (&string_obstack, *cp);
	  cp++;
	  size++;
	}

      while (cp < sp)
	{
	  if (*cp == ';' || (*cp == '\\' && cp[1] == 'n'))
	    {
	      /* Don't set a value if there are more than one
		 instruction in the string.  */
	      obstack_next_free (&string_obstack) =
		obstack_next_free (&string_obstack) - size;
	      size = 0;

	      cp = sp;
	      break;
	    }
	  cp++;
	}
      if (size == 0)
	obstack_1grow (&string_obstack, '*');
      else
	add_mnemonic_string (mnemonic_htab,
			     obstack_next_free (&string_obstack) - size,
			     size);
      i++;
    }

  /* An insn definition might emit an empty string.  */
  if (obstack_object_size (&string_obstack) == 0)
    return;

  obstack_1grow (&string_obstack, '\0');

  set_attr = rtx_alloc (SET_ATTR);
  XSTR (set_attr, 1) = XOBFINISH (&string_obstack, char *);
  attr_name = XNEWVAR (char, strlen (MNEMONIC_ATTR_NAME) + 1);
  strcpy (attr_name, MNEMONIC_ATTR_NAME);
  XSTR (set_attr, 0) = attr_name;

  if (!XVEC (insn, 4))
    vec_len = 0;
  else
    vec_len = XVECLEN (insn, 4);

  new_vec = rtvec_alloc (vec_len + 1);
  for (i = 0; i < vec_len; i++)
    RTVEC_ELT (new_vec, i) = XVECEXP (insn, 4, i);
  RTVEC_ELT (new_vec, vec_len) = set_attr;
  XVEC (insn, 4) = new_vec;
}

/* This function is called for the elements in the mnemonic hashtable
   and generates a comma separated list of the mnemonics.  */

static int
mnemonic_htab_callback (void **slot, void *info ATTRIBUTE_UNUSED)
{
  obstack_grow (&string_obstack, (char*)*slot, strlen ((char*)*slot));
  obstack_1grow (&string_obstack, ',');
  return 1;
}

/* Generate (set_attr "mnemonic" "..") RTXs and append them to every
   insn definition in case the back end requests it by defining the
   mnemonic attribute.  The values for the attribute will be extracted
   from the output patterns of the insn definitions as far as
   possible.  */

static void
gen_mnemonic_attr (void)
{
  struct queue_elem *elem;
  rtx mnemonic_attr = NULL;
  htab_t mnemonic_htab;
  const char *str, *p;
  int i;

  if (have_error)
    return;

  /* Look for the DEFINE_ATTR for `mnemonic'.  */
  for (elem = define_attr_queue; elem != *define_attr_tail; elem = elem->next)
    if (GET_CODE (elem->data) == DEFINE_ATTR
	&& strcmp (XSTR (elem->data, 0), MNEMONIC_ATTR_NAME) == 0)
      {
	mnemonic_attr = elem->data;
	break;
      }

  /* A (define_attr "mnemonic" "...") indicates that the back-end
     wants a mnemonic attribute to be generated.  */
  if (!mnemonic_attr)
    return;

  mnemonic_htab = htab_create_alloc (MNEMONIC_HTAB_SIZE, htab_hash_string,
				     htab_eq_string, 0, xcalloc, free);

  for (elem = define_insn_queue; elem; elem = elem->next)
    {
      rtx insn = elem->data;
      bool found = false;

      /* Check if the insn definition already has
	 (set_attr "mnemonic" ...).  */
      if (XVEC (insn, 4))
 	for (i = 0; i < XVECLEN (insn, 4); i++)
	  if (strcmp (XSTR (XVECEXP (insn, 4, i), 0), MNEMONIC_ATTR_NAME) == 0)
	    {
	      found = true;
	      break;
	    }

      if (!found)
	gen_mnemonic_setattr (mnemonic_htab, insn);
    }

  /* Add the user defined values to the hash table.  */
  str = XSTR (mnemonic_attr, 1);
  while ((p = scan_comma_elt (&str)) != NULL)
    add_mnemonic_string (mnemonic_htab, p, str - p);

  htab_traverse (mnemonic_htab, mnemonic_htab_callback, NULL);

  /* Replace the last ',' with the zero end character.  */
  *((char *)obstack_next_free (&string_obstack) - 1) = '\0';
  XSTR (mnemonic_attr, 1) = XOBFINISH (&string_obstack, char *);
}

/* The entry point for initializing the reader.  */

bool
init_rtx_reader_args_cb (int argc, char **argv,
			 bool (*parse_opt) (const char *))
{
  /* Prepare to read input.  */
  condition_table = htab_create (500, hash_c_test, cmp_c_test, NULL);
  init_predicate_table ();
  obstack_init (rtl_obstack);
  sequence_num = 0;

  read_md_files (argc, argv, parse_opt, rtx_handle_directive);

  /* Process define_cond_exec patterns.  */
  if (define_cond_exec_queue != NULL)
    process_define_cond_exec ();

  if (define_attr_queue != NULL)
    gen_mnemonic_attr ();

  return !have_error;
}

/* Programs that don't have their own options can use this entry point
   instead.  */
bool
init_rtx_reader_args (int argc, char **argv)
{
  return init_rtx_reader_args_cb (argc, argv, 0);
}

/* The entry point for reading a single rtx from an md file.  */

rtx
read_md_rtx (int *lineno, int *seqnr)
{
  struct queue_elem **queue, *elem;
  rtx desc;

 discard:

  /* Read all patterns from a given queue before moving on to the next.  */
  if (define_attr_queue != NULL)
    queue = &define_attr_queue;
  else if (define_pred_queue != NULL)
    queue = &define_pred_queue;
  else if (define_insn_queue != NULL)
    queue = &define_insn_queue;
  else if (other_queue != NULL)
    queue = &other_queue;
  else
    return NULL_RTX;

  elem = *queue;
  *queue = elem->next;
  desc = elem->data;
  read_md_filename = elem->filename;
  *lineno = elem->lineno;
  *seqnr = sequence_num;

  free (elem);

  /* Discard insn patterns which we know can never match (because
     their C test is provably always false).  If insn_elision is
     false, our caller needs to see all the patterns.  Note that the
     elided patterns are never counted by the sequence numbering; it
     it is the caller's responsibility, when insn_elision is false, not
     to use elided pattern numbers for anything.  */
  switch (GET_CODE (desc))
    {
    case DEFINE_INSN:
    case DEFINE_EXPAND:
      if (maybe_eval_c_test (XSTR (desc, 2)) != 0)
	sequence_num++;
      else if (insn_elision)
	goto discard;

      /* *seqnr is used here so the name table will match caller's
	 idea of insn numbering, whether or not elision is active.  */
      record_insn_name (*seqnr, XSTR (desc, 0));
      break;

    case DEFINE_SPLIT:
    case DEFINE_PEEPHOLE:
    case DEFINE_PEEPHOLE2:
      if (maybe_eval_c_test (XSTR (desc, 1)) != 0)
	sequence_num++;
      else if (insn_elision)
	    goto discard;
      break;

    default:
      break;
    }

  return desc;
}

/* Helper functions for insn elision.  */

/* Compute a hash function of a c_test structure, which is keyed
   by its ->expr field.  */
hashval_t
hash_c_test (const void *x)
{
  const struct c_test *a = (const struct c_test *) x;
  const unsigned char *base, *s = (const unsigned char *) a->expr;
  hashval_t hash;
  unsigned char c;
  unsigned int len;

  base = s;
  hash = 0;

  while ((c = *s++) != '\0')
    {
      hash += c + (c << 17);
      hash ^= hash >> 2;
    }

  len = s - base;
  hash += len + (len << 17);
  hash ^= hash >> 2;

  return hash;
}

/* Compare two c_test expression structures.  */
int
cmp_c_test (const void *x, const void *y)
{
  const struct c_test *a = (const struct c_test *) x;
  const struct c_test *b = (const struct c_test *) y;

  return !strcmp (a->expr, b->expr);
}

/* Given a string representing a C test expression, look it up in the
   condition_table and report whether or not its value is known
   at compile time.  Returns a tristate: 1 for known true, 0 for
   known false, -1 for unknown.  */
int
maybe_eval_c_test (const char *expr)
{
  const struct c_test *test;
  struct c_test dummy;

  if (expr[0] == 0)
    return 1;

  dummy.expr = expr;
  test = (const struct c_test *)htab_find (condition_table, &dummy);
  if (!test)
    return -1;
  return test->value;
}

/* Record the C test expression EXPR in the condition_table, with
   value VAL.  Duplicates clobber previous entries.  */

void
add_c_test (const char *expr, int value)
{
  struct c_test *test;

  if (expr[0] == 0)
    return;

  test = XNEW (struct c_test);
  test->expr = expr;
  test->value = value;

  *(htab_find_slot (condition_table, test, INSERT)) = test;
}

/* For every C test, call CALLBACK with two arguments: a pointer to
   the condition structure and INFO.  Stops when CALLBACK returns zero.  */
void
traverse_c_tests (htab_trav callback, void *info)
{
  if (condition_table)
    htab_traverse (condition_table, callback, info);
}

/* Helper functions for define_predicate and define_special_predicate
   processing.  Shared between genrecog.c and genpreds.c.  */

static htab_t predicate_table;
struct pred_data *first_predicate;
static struct pred_data **last_predicate = &first_predicate;

static hashval_t
hash_struct_pred_data (const void *ptr)
{
  return htab_hash_string (((const struct pred_data *)ptr)->name);
}

static int
eq_struct_pred_data (const void *a, const void *b)
{
  return !strcmp (((const struct pred_data *)a)->name,
		  ((const struct pred_data *)b)->name);
}

struct pred_data *
lookup_predicate (const char *name)
{
  struct pred_data key;
  key.name = name;
  return (struct pred_data *) htab_find (predicate_table, &key);
}

/* Record that predicate PRED can accept CODE.  */

void
add_predicate_code (struct pred_data *pred, enum rtx_code code)
{
  if (!pred->codes[code])
    {
      pred->num_codes++;
      pred->codes[code] = true;

      if (GET_RTX_CLASS (code) != RTX_CONST_OBJ)
	pred->allows_non_const = true;

      if (code != REG
	  && code != SUBREG
	  && code != MEM
	  && code != CONCAT
	  && code != PARALLEL
	  && code != STRICT_LOW_PART)
	pred->allows_non_lvalue = true;

      if (pred->num_codes == 1)
	pred->singleton = code;
      else if (pred->num_codes == 2)
	pred->singleton = UNKNOWN;
    }
}

void
add_predicate (struct pred_data *pred)
{
  void **slot = htab_find_slot (predicate_table, pred, INSERT);
  if (*slot)
    {
      error ("duplicate predicate definition for '%s'", pred->name);
      return;
    }
  *slot = pred;
  *last_predicate = pred;
  last_predicate = &pred->next;
}

/* This array gives the initial content of the predicate table.  It
   has entries for all predicates defined in recog.c.  */

struct std_pred_table
{
  const char *name;
  bool special;
  bool allows_const_p;
  RTX_CODE codes[NUM_RTX_CODE];
};

static const struct std_pred_table std_preds[] = {
  {"general_operand", false, true, {SUBREG, REG, MEM}},
  {"address_operand", true, true, {SUBREG, REG, MEM, PLUS, MINUS, MULT}},
  {"register_operand", false, false, {SUBREG, REG}},
  {"pmode_register_operand", true, false, {SUBREG, REG}},
  {"scratch_operand", false, false, {SCRATCH, REG}},
  {"immediate_operand", false, true, {UNKNOWN}},
  {"const_int_operand", false, false, {CONST_INT}},
  {"const_double_operand", false, false, {CONST_INT, CONST_DOUBLE}},
  {"nonimmediate_operand", false, false, {SUBREG, REG, MEM}},
  {"nonmemory_operand", false, true, {SUBREG, REG}},
  {"push_operand", false, false, {MEM}},
  {"pop_operand", false, false, {MEM}},
  {"memory_operand", false, false, {SUBREG, MEM}},
  {"indirect_operand", false, false, {SUBREG, MEM}},
  {"ordered_comparison_operator", false, false, {EQ, NE,
						 LE, LT, GE, GT,
						 LEU, LTU, GEU, GTU}},
  {"comparison_operator", false, false, {EQ, NE,
					 LE, LT, GE, GT,
					 LEU, LTU, GEU, GTU,
					 UNORDERED, ORDERED,
					 UNEQ, UNGE, UNGT,
					 UNLE, UNLT, LTGT}}
};
#define NUM_KNOWN_STD_PREDS ARRAY_SIZE (std_preds)

/* Initialize the table of predicate definitions, starting with
   the information we have on generic predicates.  */

static void
init_predicate_table (void)
{
  size_t i, j;
  struct pred_data *pred;

  predicate_table = htab_create_alloc (37, hash_struct_pred_data,
				       eq_struct_pred_data, 0,
				       xcalloc, free);

  for (i = 0; i < NUM_KNOWN_STD_PREDS; i++)
    {
      pred = XCNEW (struct pred_data);
      pred->name = std_preds[i].name;
      pred->special = std_preds[i].special;

      for (j = 0; std_preds[i].codes[j] != 0; j++)
	add_predicate_code (pred, std_preds[i].codes[j]);

      if (std_preds[i].allows_const_p)
	for (j = 0; j < NUM_RTX_CODE; j++)
	  if (GET_RTX_CLASS (j) == RTX_CONST_OBJ)
	    add_predicate_code (pred, (enum rtx_code) j);

      add_predicate (pred);
    }
}

/* These functions allow linkage with print-rtl.c.  Also, some generators
   like to annotate their output with insn names.  */

/* Holds an array of names indexed by insn_code_number.  */
static char **insn_name_ptr = 0;
static int insn_name_ptr_size = 0;

const char *
get_insn_name (int code)
{
  if (code < insn_name_ptr_size)
    return insn_name_ptr[code];
  else
    return NULL;
}

static void
record_insn_name (int code, const char *name)
{
  static const char *last_real_name = "insn";
  static int last_real_code = 0;
  char *new_name;

  if (insn_name_ptr_size <= code)
    {
      int new_size;
      new_size = (insn_name_ptr_size ? insn_name_ptr_size * 2 : 512);
      insn_name_ptr = XRESIZEVEC (char *, insn_name_ptr, new_size);
      memset (insn_name_ptr + insn_name_ptr_size, 0,
	      sizeof(char *) * (new_size - insn_name_ptr_size));
      insn_name_ptr_size = new_size;
    }

  if (!name || name[0] == '\0')
    {
      new_name = XNEWVAR (char, strlen (last_real_name) + 10);
      sprintf (new_name, "%s+%d", last_real_name, code - last_real_code);
    }
  else
    {
      last_real_name = new_name = xstrdup (name);
      last_real_code = code;
    }

  insn_name_ptr[code] = new_name;
}