gcc/genoutput.cc

/* Generate code from to output assembler insns as recognized from rtl.
   Copyright (C) 1987-2025 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/>.  */


/* This program reads the machine description for the compiler target machine
   and produces a file containing these things:

   1. An array of `struct insn_data_d', which is indexed by insn code number,
   which contains:

     a. `name' is the name for that pattern.  Nameless patterns are
     given a name.

     b. `output' hold either the output template, an array of output
     templates, or an output function.

     c. `genfun' is the function to generate a body for that pattern,
     given operands as arguments.

     d. `n_operands' is the number of distinct operands in the pattern
     for that insn,

     e. `n_dups' is the number of match_dup's that appear in the insn's
     pattern.  This says how many elements of `recog_data.dup_loc' are
     significant after an insn has been recognized.

     f. `n_alternatives' is the number of alternatives in the constraints
     of each pattern.

     g. `output_format' tells what type of thing `output' is.

     h. `operand' is the base of an array of operand data for the insn.

   2. An array of `struct insn_operand data', used by `operand' above.

     a. `predicate', an int-valued function, is the match_operand predicate
     for this operand.

     b. `constraint' is the constraint for this operand.

     c. `address_p' indicates that the operand appears within ADDRESS
     rtx's.

     d. `mode' is the machine mode that that operand is supposed to have.

     e. `strict_low', is nonzero for operands contained in a STRICT_LOW_PART.

     f. `eliminable', is nonzero for operands that are matched normally by
     MATCH_OPERAND; it is zero for operands that should not be changed during
     register elimination such as MATCH_OPERATORs.

     g. `allows_mem', is true for operands that accept MEM rtxes.

  The code number of an insn is simply its position in the machine
  description; code numbers are assigned sequentially to entries in
  the description, starting with code number 0.

  Thus, the following entry in the machine description

    (define_insn "clrdf"
      [(set (match_operand:DF 0 "general_operand" "")
	    (const_int 0))]
      ""
      "clrd %0")

  assuming it is the 25th entry present, would cause
  insn_data[24].template to be "clrd %0", and
  insn_data[24].n_operands to be 1.  */

#include "bconfig.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "rtl.h"
#include "errors.h"
#include "read-md.h"
#include "gensupport.h"
#include "hash-table.h"

/* No instruction can have more operands than this.  Sorry for this
   arbitrary limit, but what machine will have an instruction with
   this many operands?  */

#define MAX_MAX_OPERANDS 40

static char general_mem[] = { TARGET_MEM_CONSTRAINT, 0 };

static int n_occurrences		(int, const char *);
static const char *strip_whitespace	(const char *);

/* This counts all operands used in the md file.  The first is null.  */

static int next_operand_number = 1;

/* Record in this chain all information about the operands we will output.  */

struct operand_data
{
  struct operand_data *next;
  /* Point to the next member with the same hash value in the hash table.  */
  struct operand_data *eq_next;
  int index;
  const char *predicate;
  const char *constraint;
  machine_mode mode;
  unsigned char n_alternatives;
  char address_p;
  char strict_low;
  char eliminable;
  char seen;
};

/* Begin with a null operand at index 0.  */

static struct operand_data null_operand =
{
  0, 0, 0, "", "", E_VOIDmode, 0, 0, 0, 0, 0
};

static struct operand_data *odata = &null_operand;
static struct operand_data **odata_end = &null_operand.next;

/* Must match the constants in recog.h.  */

#define INSN_OUTPUT_FORMAT_NONE         0       /* abort */
#define INSN_OUTPUT_FORMAT_SINGLE       1       /* const char * */
#define INSN_OUTPUT_FORMAT_MULTI        2       /* const char * const * */
#define INSN_OUTPUT_FORMAT_FUNCTION     3       /* const char * (*)(...) */

/* Record in this chain all information that we will output,
   associated with the code number of the insn.  */

class data
{
public:
  class data *next;
  const char *name;
  const char *template_code;
  file_location loc;
  int code_number;
  int n_generator_args;		/* Number of arguments passed to generator */
  int n_operands;		/* Number of operands this insn recognizes */
  int n_dups;			/* Number times match_dup appears in pattern */
  int n_alternatives;		/* Number of alternatives in each constraint */
  int operand_number;		/* Operand index in the big array.  */
  int output_format;		/* INSN_OUTPUT_FORMAT_*.  */
  bool compact_syntax_p;
  struct operand_data operand[MAX_MAX_OPERANDS];
};

/* This variable points to the first link in the insn chain.  */
static class data *idata;

/* This variable points to the end of the insn chain.  This is where
   everything relevant from the machien description is appended to.  */
static class data **idata_end;


static void output_prologue (void);
static void output_operand_data (void);
static void output_insn_data (void);
static void output_get_insn_name (void);
static void scan_operands (class data *, rtx, int, int);
static int compare_operands (const struct operand_data *,
			     const struct operand_data *);
static void place_operands (class data *);
static void process_template (class data *, const char *);
static void validate_insn_alternatives (class data *);
static void validate_insn_operands (class data *);

class constraint_data
{
public:
  class constraint_data *next_this_letter;
  file_location loc;
  unsigned int namelen;
  char name[1];
};

/* All machine-independent constraint characters (except digits) that
   are handled outside the define*_constraint mechanism.  */
static const char indep_constraints[] = ",=+%*?!^$#&g";

static class constraint_data *
constraints_by_letter_table[1 << CHAR_BIT];

static hash_set<free_string_hash> used_reg_names;

static int mdep_constraint_len (const char *, file_location, int);
static void note_constraint (md_rtx_info *);

static void
output_prologue (void)
{
  printf ("/* Generated automatically by the program `genoutput'\n\
   from the machine description file `md'.  */\n\n");

  printf ("#define IN_TARGET_CODE 1\n");
  printf ("#include \"config.h\"\n");
  printf ("#include \"system.h\"\n");
  printf ("#include \"coretypes.h\"\n");
  printf ("#include \"backend.h\"\n");
  printf ("#include \"predict.h\"\n");
  printf ("#include \"tree.h\"\n");
  printf ("#include \"rtl.h\"\n");
  printf ("#include \"flags.h\"\n");
  printf ("#include \"alias.h\"\n");
  printf ("#include \"varasm.h\"\n");
  printf ("#include \"stor-layout.h\"\n");
  printf ("#include \"calls.h\"\n");
  printf ("#include \"insn-config.h\"\n");
  printf ("#include \"expmed.h\"\n");
  printf ("#include \"dojump.h\"\n");
  printf ("#include \"explow.h\"\n");
  printf ("#include \"memmodel.h\"\n");
  printf ("#include \"emit-rtl.h\"\n");
  printf ("#include \"stmt.h\"\n");
  printf ("#include \"expr.h\"\n");
  printf ("#include \"insn-codes.h\"\n");
  printf ("#include \"tm_p.h\"\n");
  printf ("#include \"regs.h\"\n");
  printf ("#include \"conditions.h\"\n");
  printf ("#include \"insn-attr.h\"\n\n");
  printf ("#include \"recog.h\"\n\n");
  printf ("#include \"diagnostic-core.h\"\n");
  printf ("#include \"output.h\"\n");
  printf ("#include \"target.h\"\n");
  printf ("#include \"tm-constrs.h\"\n");
}

static void
output_operand_data (void)
{
  struct operand_data *d;

  printf ("\nstatic const struct insn_operand_data operand_data[] = \n{\n");

  for (d = odata; d; d = d->next)
    {
      struct pred_data *pred;

      printf ("  {\n");

      printf ("    %s,\n",
	      d->predicate && d->predicate[0] ? d->predicate : "0");

      printf ("    \"%s\",\n", d->constraint ? d->constraint : "");

      printf ("    E_%smode,\n", GET_MODE_NAME (d->mode));

      printf ("    %d,\n", d->strict_low);

      printf ("    %d,\n", d->constraint == NULL ? 1 : 0);

      printf ("    %d,\n", d->eliminable);

      pred = NULL;
      if (d->predicate)
	pred = lookup_predicate (d->predicate);
      printf ("    %d\n", pred && pred->codes[MEM]);

      printf ("  },\n");
    }
  printf ("};\n\n\n");
}

static void
output_insn_data (void)
{
  class data *d;
  int name_offset = 0;
  int next_name_offset;
  const char * last_name = 0;
  const char * next_name = 0;
  class data *n;

  for (n = idata, next_name_offset = 1; n; n = n->next, next_name_offset++)
    if (n->name)
      {
	next_name = n->name;
	break;
      }

  printf ("#if GCC_VERSION >= 2007\n__extension__\n#endif\n");
  printf ("\nconst struct insn_data_d insn_data[] = \n{\n");

  for (d = idata; d; d = d->next)
    {
      printf ("  /* %s:%d */\n", d->loc.filename, d->loc.lineno);
      printf ("  {\n");

      if (d->name)
	{
	  printf ("    \"%s\",\n", d->name);
	  name_offset = 0;
	  last_name = d->name;
	  next_name = 0;
	  for (n = d->next, next_name_offset = 1; n;
	       n = n->next, next_name_offset++)
	    {
	      if (n->name)
		{
		  next_name = n->name;
		  break;
		}
	    }
	}
      else
	{
	  name_offset++;
	  if (next_name && (last_name == 0
			    || name_offset > next_name_offset / 2))
	    printf ("    \"%s-%d\",\n", next_name,
		    next_name_offset - name_offset);
	  else
	    printf ("    \"%s+%d\",\n", last_name, name_offset);
	}

      switch (d->output_format)
	{
	case INSN_OUTPUT_FORMAT_NONE:
	  printf ("#if HAVE_DESIGNATED_UNION_INITIALIZERS\n");
	  printf ("    { 0 },\n");
	  printf ("#else\n");
	  printf ("    { 0, 0, 0 },\n");
	  printf ("#endif\n");
	  break;
	case INSN_OUTPUT_FORMAT_SINGLE:
	  {
	    const char *p = d->template_code;
	    char prev = 0;

	    printf ("#if HAVE_DESIGNATED_UNION_INITIALIZERS\n");
	    printf ("    { .single =\n");
	    printf ("#else\n");
	    printf ("    {\n");
	    printf ("#endif\n");
	    printf ("    \"");
	    while (*p)
	      {
		if (IS_VSPACE (*p) && prev != '\\')
		  {
		    /* Preserve two consecutive \n's or \r's, but treat \r\n
		       as a single newline.  */
		    if (*p == '\n' && prev != '\r')
		      printf ("\\n\\\n");
		  }
		else
		  putchar (*p);
		prev = *p;
		++p;
	      }
	    printf ("\",\n");
	    printf ("#if HAVE_DESIGNATED_UNION_INITIALIZERS\n");
	    printf ("    },\n");
	    printf ("#else\n");
	    printf ("    0, 0 },\n");
	    printf ("#endif\n");
	  }
	  break;
	case INSN_OUTPUT_FORMAT_MULTI:
	  printf ("#if HAVE_DESIGNATED_UNION_INITIALIZERS\n");
	  printf ("    { .multi = output_%d },\n", d->code_number);
	  printf ("#else\n");
	  printf ("    { 0, output_%d, 0 },\n", d->code_number);
	  printf ("#endif\n");
	  break;
	case INSN_OUTPUT_FORMAT_FUNCTION:
	  printf ("#if HAVE_DESIGNATED_UNION_INITIALIZERS\n");
	  printf ("    { .function = output_%d },\n", d->code_number);
	  printf ("#else\n");
	  printf ("    { 0, 0, output_%d },\n", d->code_number);
	  printf ("#endif\n");
	  break;
	default:
	  gcc_unreachable ();
	}

      if (d->name && d->name[0] != '*')
	printf ("    { (insn_gen_fn::stored_funcptr) gen_%s },\n", d->name);
      else
	printf ("    { 0 },\n");

      printf ("    &operand_data[%d],\n", d->operand_number);
      printf ("    %d,\n", d->n_generator_args);
      printf ("    %d,\n", d->n_operands);
      printf ("    %d,\n", d->n_dups);
      printf ("    %d,\n", d->n_alternatives);
      printf ("    %d\n", d->output_format);

      printf ("  },\n");
    }
  printf ("};\n\n\n");
}

static void
output_get_insn_name (void)
{
  printf ("const char *\n");
  printf ("get_insn_name (int code)\n");
  printf ("{\n");
  printf ("  if (code == NOOP_MOVE_INSN_CODE)\n");
  printf ("    return \"NOOP_MOVE\";\n");
  printf ("  else\n");
  printf ("    return insn_data[code].name;\n");
  printf ("}\n");
}


/* Stores the operand data into `d->operand[i]'.

   THIS_ADDRESS_P is nonzero if the containing rtx was an ADDRESS.
   THIS_STRICT_LOW is nonzero if the containing rtx was a STRICT_LOW_PART.  */

static void
scan_operands (class data *d, rtx part, int this_address_p,
	       int this_strict_low)
{
  int i, j;
  const char *format_ptr;
  int opno;

  if (part == 0)
    return;

  switch (GET_CODE (part))
    {
    case MATCH_OPERAND:
      opno = XINT (part, 0);
      if (opno >= MAX_MAX_OPERANDS)
	{
	  error_at (d->loc, "maximum number of operands exceeded");
	  return;
	}
      if (d->operand[opno].seen)
	error_at (d->loc, "repeated operand number %d\n", opno);

      d->operand[opno].seen = 1;
      d->operand[opno].mode = GET_MODE (part);
      d->operand[opno].strict_low = this_strict_low;
      d->operand[opno].predicate = XSTR (part, 1);
      d->operand[opno].constraint = strip_whitespace (XSTR (part, 2));
      d->operand[opno].n_alternatives
	= n_occurrences (',', d->operand[opno].constraint) + 1;
      d->operand[opno].address_p = this_address_p;
      d->operand[opno].eliminable = 1;
      return;

    case MATCH_SCRATCH:
      opno = XINT (part, 0);
      if (opno >= MAX_MAX_OPERANDS)
	{
	  error_at (d->loc, "maximum number of operands exceeded");
	  return;
	}
      if (d->operand[opno].seen)
	error_at (d->loc, "repeated operand number %d\n", opno);

      d->operand[opno].seen = 1;
      d->operand[opno].mode = GET_MODE (part);
      d->operand[opno].strict_low = 0;
      d->operand[opno].predicate = "scratch_operand";
      d->operand[opno].constraint = strip_whitespace (XSTR (part, 1));
      d->operand[opno].n_alternatives
	= n_occurrences (',', d->operand[opno].constraint) + 1;
      d->operand[opno].address_p = 0;
      d->operand[opno].eliminable = 1;
      return;

    case MATCH_OPERATOR:
    case MATCH_PARALLEL:
      opno = XINT (part, 0);
      if (opno >= MAX_MAX_OPERANDS)
	{
	  error_at (d->loc, "maximum number of operands exceeded");
	  return;
	}
      if (d->operand[opno].seen)
	error_at (d->loc, "repeated operand number %d\n", opno);

      d->operand[opno].seen = 1;
      d->operand[opno].mode = GET_MODE (part);
      d->operand[opno].strict_low = 0;
      d->operand[opno].predicate = XSTR (part, 1);
      d->operand[opno].constraint = 0;
      d->operand[opno].address_p = 0;
      d->operand[opno].eliminable = 0;
      for (i = 0; i < XVECLEN (part, 2); i++)
	scan_operands (d, XVECEXP (part, 2, i), 0, 0);
      return;

    case STRICT_LOW_PART:
      scan_operands (d, XEXP (part, 0), 0, 1);
      return;

    default:
      break;
    }

  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':
	scan_operands (d, XEXP (part, i), 0, 0);
	break;
      case 'E':
	if (XVEC (part, i) != NULL)
	  for (j = 0; j < XVECLEN (part, i); j++)
	    scan_operands (d, XVECEXP (part, i, j), 0, 0);
	break;
      }
}

/* Compare two operands for content equality.  */

static int
compare_operands (const struct operand_data *d0,
		  const struct operand_data *d1)
{
  const char *p0, *p1;

  /* On one hand, comparing strings for predicate and constraint
     is time-consuming, and on the other hand, the probability of
     different modes is relatively high. Therefore, checking the mode
     first can speed up the execution of the program.  */
  if (d0->mode != d1->mode)
    return 0;

  p0 = d0->predicate;
  if (!p0)
    p0 = "";
  p1 = d1->predicate;
  if (!p1)
    p1 = "";
  if (strcmp (p0, p1) != 0)
    return 0;

  p0 = d0->constraint;
  if (!p0)
    p0 = "";
  p1 = d1->constraint;
  if (!p1)
    p1 = "";
  if (strcmp (p0, p1) != 0)
    return 0;

  if (d0->strict_low != d1->strict_low)
    return 0;

  if (d0->eliminable != d1->eliminable)
    return 0;

  return 1;
}

/* This is a class that takes into account the necessary elements for
   comparing the equality of two operands in its hash value.  */
struct operand_data_hasher : nofree_ptr_hash <operand_data>
{
  static inline hashval_t hash (const operand_data *);
  static inline bool equal (const operand_data *, const operand_data *);
};

hashval_t
operand_data_hasher::hash (const operand_data * op_info)
{
  inchash::hash h;
  const char *pred, *cons;

  pred = op_info->predicate;
  if (!pred)
    pred = "";
  h.add (pred, strlen (pred) + 1);

  cons = op_info->constraint;
  if (!cons)
    cons = "";
  h.add (cons, strlen (cons) + 1);

  h.add_object (op_info->mode);
  h.add_object (op_info->strict_low);
  h.add_object (op_info->eliminable);
  return h.end ();
}

bool
operand_data_hasher::equal (const operand_data * op_info1,
			    const operand_data * op_info2)
{
  return compare_operands (op_info1, op_info2);
}

/* Hashtable of konwn pattern operands.  */
static hash_table<operand_data_hasher> *operand_datas;

/* Scan the list of operands we've already committed to output and either
   find a subsequence that is the same, or allocate a new one at the end.  */

static void
place_operands (class data *d)
{
  struct operand_data *od, *od2;
  struct operand_data **slot;
  int i;

  if (d->n_operands == 0)
    {
      d->operand_number = 0;
      return;
    }

  od = operand_datas->find (&d->operand[0]);
  /* Brute force substring search.  */
  for (; od; od = od->eq_next)
    {
      od2 = od->next;
      i = 1;
      while (1)
	{
	  if (i == d->n_operands)
	    goto full_match;
	  if (od2 == NULL)
	    goto partial_match;
	  if (! compare_operands (od2, &d->operand[i]))
	    break;
	  ++i, od2 = od2->next;
	}
    }
  i = 0;

  /* Either partial match at the end of the list, or no match.  In either
     case, we tack on what operands are remaining to the end of the list.  */
 partial_match:
  d->operand_number = next_operand_number - i;
  for (; i < d->n_operands; ++i)
    {
      od2 = &d->operand[i];
      *odata_end = od2;
      odata_end = &od2->next;
      od2->index = next_operand_number++;
      /* Insert the operand_data variable OD2 into the hash table.
	 If a variable with the same hash value already exists in
	 the hash table, insert the element at the end of the
	 linked list connected through the eq_next member.  */
      slot = operand_datas->find_slot (od2, INSERT);
      if (*slot)
	{
	  struct operand_data *last = (struct operand_data *) *slot;
	  while (last->eq_next)
	    last = last->eq_next;
	  last->eq_next = od2;
	}
      else
	*slot = od2;
    }
  *odata_end = NULL;
  return;

 full_match:
  d->operand_number = od->index;
  return;
}


/* Process an assembler template from a define_insn or a define_peephole.
   It is either the assembler code template, a list of assembler code
   templates, or C code to generate the assembler code template.  */

static void
process_template (class data *d, const char *template_code)
{
  const char *cp;
  int i;

  /* Templates starting with * contain straight code to be run.  */
  if (template_code[0] == '*')
    {
      d->template_code = 0;
      d->output_format = INSN_OUTPUT_FORMAT_FUNCTION;

      puts ("\nstatic const char *");
      printf ("output_%d (rtx *operands ATTRIBUTE_UNUSED, rtx_insn *insn ATTRIBUTE_UNUSED)\n",
	      d->code_number);
      puts ("{");
      rtx_reader_ptr->print_md_ptr_loc (template_code);
      puts (template_code + 1);
      puts ("}");
    }

  /* If the assembler code template starts with a @ it is a newline-separated
     list of assembler code templates, one for each alternative.  */
  else if (template_code[0] == '@')
    {
      int found_star = 0;

      for (cp = &template_code[1]; *cp; )
	{
	  while (ISSPACE (*cp))
	    cp++;
	  if (*cp == '*')
	    found_star = 1;
	  while (!IS_VSPACE (*cp) && *cp != '\0')
	    ++cp;
	}
      d->template_code = 0;
      if (found_star)
	{
	  d->output_format = INSN_OUTPUT_FORMAT_FUNCTION;
	  puts ("\nstatic const char *");
	  printf ("output_%d (rtx *operands ATTRIBUTE_UNUSED, "
		  "rtx_insn *insn ATTRIBUTE_UNUSED)\n", d->code_number);
	  puts ("{");
	  puts ("  switch (which_alternative)\n    {");
	}
      else
	{
	  d->output_format = INSN_OUTPUT_FORMAT_MULTI;
	  printf ("\nstatic const char * const output_%d[] = {\n",
		  d->code_number);
	}

      for (i = 0, cp = &template_code[1]; *cp; )
	{
	  const char *ep, *sp, *bp;

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

	  bp = cp;
	  if (found_star)
	    {
	      printf ("    case %d:", i);
	      if (*cp == '*')
		{
		  printf ("\n      ");
		  cp++;
		}
	      else
		printf (" return \"");
	    }
	  else
	    printf ("  \"");

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

	  if (sp != ep)
	    message_at (d->loc, "trailing whitespace in output template");

	  /* Check for any unexpanded iterators.  */
	  if (bp[0] != '*' && d->compact_syntax_p)
	    {
	      const char *p = cp;
	      const char *last_bracket = nullptr;
	      while (p < sp)
		{
		  if (*p == '\\' && p + 1 < sp)
		    {
		      putchar (*p);
		      putchar (*(p+1));
		      p += 2;
		      continue;
		    }

		  if (*p == '>' && last_bracket && *last_bracket == '<')
		    {
		      int len = p - last_bracket;
		      fatal_at (d->loc, "unresolved iterator '%.*s' in '%s'",
				len - 1, last_bracket + 1, cp);
		    }
		  else if (*p == '<' || *p == '>')
		    last_bracket = p;

		  putchar (*p);
		  p += 1;
		}

	      if (last_bracket)
		{
		  char *nl = strchr (const_cast<char*> (cp), '\n');
		  if (nl)
		    *nl = '\0';
		  fatal_at (d->loc, "unmatched angle brackets, likely an "
			    "error in iterator syntax in %s", cp);
		}
	    }
	  else
	    {
	      while (cp < sp)
		putchar (*(cp++));
	    }

	  cp = sp;

	  if (!found_star)
	    puts ("\",");
	  else if (*bp != '*')
	    puts ("\";");
	  else
	    {
	      /* The usual action will end with a return.
		 If there is neither break or return at the end, this is
		 assumed to be intentional; this allows to have multiple
		 consecutive alternatives share some code.  */
	      puts ("");
	    }
	  i++;
	}
      if (i == 1)
	message_at (d->loc, "'@' is redundant for output template with"
		    " single alternative");
      if (i != d->n_alternatives)
	error_at (d->loc, "wrong number of alternatives in the output"
		  " template");

      if (found_star)
	puts ("      default: gcc_unreachable ();\n    }\n}");
      else
	printf ("};\n");
    }
  else
    {
      d->template_code = template_code;
      d->output_format = INSN_OUTPUT_FORMAT_SINGLE;
    }
}

/* Check insn D for consistency in number of constraint alternatives.  */

static void
validate_insn_alternatives (class data *d)
{
  int n = 0, start;

  /* Make sure all the operands have the same number of alternatives
     in their constraints.  Let N be that number.  */
  for (start = 0; start < d->n_operands; start++)
    if (d->operand[start].n_alternatives > 0)
      {
	int len, i;
	const char *p;
	char c;
	int which_alternative = 0;
	int alternative_count_unsure = 0;
	bool seen_write = false;
	bool alt_mismatch = false;

	for (p = d->operand[start].constraint; (c = *p); p += len)
	  {
	    if ((c == '%' || c == '=' || c == '+')
		&& p != d->operand[start].constraint)
	      error_at (d->loc, "character '%c' can only be used at the"
			" beginning of a constraint string", c);

	    if (c == '=' || c == '+')
	      seen_write = true;

	    /* Earlyclobber operands must always be marked write-only
	       or read/write.  */
	    if (!seen_write && c == '&')
	      error_at (d->loc, "earlyclobber operands may not be"
			" read-only in alternative %d", which_alternative);

	    if (ISSPACE (c) || strchr (indep_constraints, c))
	      len = 1;
	    else if (ISDIGIT (c))
	      {
		const char *q = p;
		do
		  q++;
		while (ISDIGIT (*q));
		len = q - p;
	      }
	    else
	      len = mdep_constraint_len (p, d->loc, start);

	    if (c == ',')
	      {
	        which_alternative++;
		continue;
	      }

	    for (i = 1; i < len; i++)
	      if (p[i] == '\0')
		{
		  error_at (d->loc, "NUL in alternative %d of operand %d",
			    which_alternative, start);
		  alternative_count_unsure = 1;
		  break;
		}
	      else if (strchr (",#*", p[i]))
		{
		  error_at (d->loc, "'%c' in alternative %d of operand %d",
			    p[i], which_alternative, start);
		  alternative_count_unsure = 1;
		}
	  }
	if (!alternative_count_unsure)
	  {
	    if (n == 0)
	      n = d->operand[start].n_alternatives;
	    else if (n != d->operand[start].n_alternatives)
	      {
		if (!alt_mismatch)
		  {
		    alt_mismatch = true;
		    error_at (d->loc,
			      "alternative number mismatch: "
			      "operand %d has %d, operand %d has %d",
			      0, n, start, d->operand[start].n_alternatives);
		  }
		else
		  error_at (d->loc, "operand %d has %d alternatives",
		    start, d->operand[start].n_alternatives);
	      }
	  }
      }

  /* Record the insn's overall number of alternatives.  */
  d->n_alternatives = n;
}

/* Verify that there are no gaps in operand numbers for INSNs.  */

static void
validate_insn_operands (class data *d)
{
  int i;

  for (i = 0; i < d->n_operands; ++i)
    if (d->operand[i].seen == 0)
      error_at (d->loc, "missing operand %d", i);
}

static void
validate_optab_operands (class data *d)
{
  if (!d->name || d->name[0] == '\0' || d->name[0] == '*')
    return;

  /* Miscellaneous tests.  */
  if (startswith (d->name, "cstore")
      && d->name[strlen (d->name) - 1] == '4'
      && d->operand[0].mode == VOIDmode)
    {
      message_at (d->loc, "missing mode for operand 0 of cstore");
      have_error = 1;
    }
}

/* Look at a define_insn just read.  Assign its code number.  Record
   on idata the template and the number of arguments.  If the insn has
   a hairy output action, output a function for now.  */

static void
gen_insn (md_rtx_info *info)
{
  struct pattern_stats stats;
  rtx insn = info->def;
  data *d = new data;
  int i;

  d->code_number = info->index;
  d->loc = info->loc;
  if (XSTR (insn, 0)[0])
    d->name = XSTR (insn, 0);
  else
    d->name = 0;

  d->compact_syntax_p = compact_syntax.contains (insn);

  /* Build up the list in the same order as the insns are seen
     in the machine description.  */
  d->next = 0;
  *idata_end = d;
  idata_end = &d->next;

  memset (d->operand, 0, sizeof (d->operand));

  for (i = 0; i < XVECLEN (insn, 1); i++)
    scan_operands (d, XVECEXP (insn, 1, i), 0, 0);

  get_pattern_stats (&stats, XVEC (insn, 1));
  d->n_generator_args = stats.num_generator_args;
  d->n_operands = stats.num_insn_operands;
  d->n_dups = stats.num_dups;

  validate_insn_operands (d);
  validate_insn_alternatives (d);
  validate_optab_operands (d);
  place_operands (d);
  process_template (d, XTMPL (insn, 3));
}

/* Look at a define_peephole just read.  Assign its code number.
   Record on idata the template and the number of arguments.
   If the insn has a hairy output action, output it now.  */

static void
gen_peephole (md_rtx_info *info)
{
  struct pattern_stats stats;
  data *d = new data;
  int i;

  d->code_number = info->index;
  d->loc = info->loc;
  d->name = 0;

  /* Build up the list in the same order as the insns are seen
     in the machine description.  */
  d->next = 0;
  *idata_end = d;
  idata_end = &d->next;

  memset (d->operand, 0, sizeof (d->operand));

  /* Get the number of operands by scanning all the patterns of the
     peephole optimizer.  But ignore all the rest of the information
     thus obtained.  */
  rtx peep = info->def;
  for (i = 0; i < XVECLEN (peep, 0); i++)
    scan_operands (d, XVECEXP (peep, 0, i), 0, 0);

  get_pattern_stats (&stats, XVEC (peep, 0));
  d->n_generator_args = 0;
  d->n_operands = stats.num_insn_operands;
  d->n_dups = 0;

  validate_insn_alternatives (d);
  place_operands (d);
  process_template (d, XTMPL (peep, 2));
}

/* Process a define_expand just read.  Assign its code number,
   only for the purposes of `insn_gen_function'.  */

static void
gen_expand (md_rtx_info *info)
{
  struct pattern_stats stats;
  rtx insn = info->def;
  data *d = new data;
  int i;

  d->code_number = info->index;
  d->loc = info->loc;
  if (XSTR (insn, 0)[0])
    d->name = XSTR (insn, 0);
  else
    d->name = 0;

  /* Build up the list in the same order as the insns are seen
     in the machine description.  */
  d->next = 0;
  *idata_end = d;
  idata_end = &d->next;

  memset (d->operand, 0, sizeof (d->operand));

  /* Scan the operands to get the specified predicates and modes,
     since expand_binop needs to know them.  */

  if (XVEC (insn, 1))
    for (i = 0; i < XVECLEN (insn, 1); i++)
      scan_operands (d, XVECEXP (insn, 1, i), 0, 0);

  get_pattern_stats (&stats, XVEC (insn, 1));
  d->n_generator_args = stats.num_generator_args;
  d->n_operands = stats.num_insn_operands;
  d->n_dups = stats.num_dups;
  d->template_code = 0;
  d->output_format = INSN_OUTPUT_FORMAT_NONE;

  validate_insn_alternatives (d);
  validate_optab_operands (d);
  place_operands (d);
}

static void
init_insn_for_nothing (void)
{
  idata = XCNEW (class data);
  new (idata) data ();
  idata->name = "*placeholder_for_nothing";
  idata->loc = file_location ("<internal>", 0, 0);
  idata_end = &idata->next;
}

extern int main (int, const char **);

int
main (int argc, const char **argv)
{
  progname = "genoutput";

  init_insn_for_nothing ();
  operand_datas = new hash_table<operand_data_hasher> (1024);

  if (!init_rtx_reader_args (argc, argv))
    return (FATAL_EXIT_CODE);

  output_prologue ();

  /* Read the machine description.  */

  md_rtx_info info;
  while (read_md_rtx (&info))
    switch (GET_CODE (info.def))
      {
      case DEFINE_INSN:
	gen_insn (&info);
	break;

      case DEFINE_PEEPHOLE:
	gen_peephole (&info);
	break;

      case DEFINE_EXPAND:
	gen_expand (&info);
	break;

      case DEFINE_CONSTRAINT:
      case DEFINE_REGISTER_CONSTRAINT:
      case DEFINE_ADDRESS_CONSTRAINT:
      case DEFINE_MEMORY_CONSTRAINT:
      case DEFINE_SPECIAL_MEMORY_CONSTRAINT:
      case DEFINE_RELAXED_MEMORY_CONSTRAINT:
	note_constraint (&info);
	break;

      default:
	break;
      }

  printf ("\n\n");
  output_operand_data ();
  output_insn_data ();
  output_get_insn_name ();

  /* Since genoutput has no information about hard register names we cannot
     statically verify hard register names in constraints of the machine
     description.  Therefore, we have to do it at runtime.  Although
     verification shouldn't be too expensive, restrict it to checking builds.
   */
  printf ("\n\n#if CHECKING_P\n");
  if (used_reg_names.is_empty ())
    printf ("void verify_reg_names_in_constraints () { }\n");
  else
    {
      size_t max_len = 0;
      for (auto it = used_reg_names.begin (); it != used_reg_names.end (); ++it)
	{
	  size_t len = strlen (*it);
	  if (len > max_len)
	    max_len = len;
	}
      printf ("void\nverify_reg_names_in_constraints ()\n{\n");
      printf ("  static const char hregnames[%zu][%zu] = {\n",
	      used_reg_names.elements (), max_len + 1);
      auto it = used_reg_names.begin ();
      while (it != used_reg_names.end ())
	{
	  printf ("    \"%s\"", *it);
	  ++it;
	  if (it != used_reg_names.end ())
	    printf (",");
	  printf ("\n");
	}
      printf ("  };\n");
      printf ("  for (size_t i = 0; i < %zu; ++i)\n",
	      used_reg_names.elements ());
      printf ("    if (decode_reg_name (hregnames[i]) < 0)\n");
      printf ("      internal_error (\"invalid register %%qs used in "
	      "constraint of machine description\", hregnames[i]);\n");
      printf ("}\n");
    }
  printf ("#endif\n");

  fflush (stdout);
  return (ferror (stdout) != 0 || have_error
	? FATAL_EXIT_CODE : SUCCESS_EXIT_CODE);
}

/* Return the number of occurrences of character C in string S or
   -1 if S is the null string.  */

static int
n_occurrences (int c, const char *s)
{
  int n = 0;

  if (s == 0 || *s == '\0')
    return -1;

  while (*s)
    n += (*s++ == c);

  return n;
}

/* Remove whitespace in `s' by moving up characters until the end.
   Return a new string.  */

static const char *
strip_whitespace (const char *s)
{
  char *p, *q;
  char ch;

  if (s == 0)
    return 0;

  p = q = XNEWVEC (char, strlen (s) + 1);
  while ((ch = *s++) != '\0')
    if (! ISSPACE (ch))
      *p++ = ch;

  *p = '\0';
  return q;
}

/* Record just enough information about the constraint in *INFO to allow
   checking of operand constraint strings above, in validate_insn_alternatives.
   Does not validate most properties of the constraint itself; does enforce
   no duplicate names, no overlap with MI constraints, and no prefixes.  */
static void
note_constraint (md_rtx_info *info)
{
  rtx exp = info->def;
  const char *name = XSTR (exp, 0);
  class constraint_data **iter, **slot, *new_cdata;

  if (strcmp (name, "TARGET_MEM_CONSTRAINT") == 0)
    name = general_mem;
  unsigned int namelen = strlen (name);

  if (strchr (indep_constraints, name[0]))
    {
      if (name[1] == '\0')
	error_at (info->loc, "constraint letter '%s' cannot be "
		  "redefined by the machine description", name);
      else
	error_at (info->loc, "constraint name '%s' cannot be defined by "
		  "the machine description, as it begins with '%c'",
		  name, name[0]);
      return;
    }

  slot = &constraints_by_letter_table[(unsigned int)name[0]];
  for (iter = slot; *iter; iter = &(*iter)->next_this_letter)
    {
      /* This causes slot to end up pointing to the
	 next_this_letter field of the last constraint with a name
	 of equal or greater length than the new constraint; hence
	 the new constraint will be inserted after all previous
	 constraints with names of the same length.  */
      if ((*iter)->namelen >= namelen)
	slot = iter;

      if (!strcmp ((*iter)->name, name))
	{
	  error_at (info->loc, "redefinition of constraint '%s'", name);
	  message_at ((*iter)->loc, "previous definition is here");
	  return;
	}
      else if (!strncmp ((*iter)->name, name, (*iter)->namelen))
	{
	  error_at (info->loc, "defining constraint '%s' here", name);
	  message_at ((*iter)->loc, "renders constraint '%s' "
		      "(defined here) a prefix", (*iter)->name);
	  return;
	}
      else if (!strncmp ((*iter)->name, name, namelen))
	{
	  error_at (info->loc, "constraint '%s' is a prefix", name);
	  message_at ((*iter)->loc, "of constraint '%s' "
		      "(defined here)", (*iter)->name);
	  return;
	}
    }
  new_cdata = XNEWVAR (class constraint_data,
		       sizeof (class constraint_data) + namelen);
  new (new_cdata) constraint_data ();
  strcpy (CONST_CAST (char *, new_cdata->name), name);
  new_cdata->namelen = namelen;
  new_cdata->loc = info->loc;
  new_cdata->next_this_letter = *slot;
  *slot = new_cdata;
}

/* Return the length of the constraint name beginning at position S
   of an operand constraint string, or issue an error message if there
   is no such constraint.  Does not expect to be called for generic
   constraints.  */
static int
mdep_constraint_len (const char *s, file_location loc, int opno)
{
  class constraint_data *p;

  p = constraints_by_letter_table[(unsigned int)s[0]];

  if (p)
    for (; p; p = p->next_this_letter)
      if (!strncmp (s, p->name, p->namelen))
	return p->namelen;

  if (*s == '{')
    {
      const char *end = s + 1;
      while (*end != '}' && *end != '"' && *end != '\0')
	++end;
      /* Similarly as in decode_hreg_constraint(), consider any hard register
	 name longer than a few characters as an error.  */
      ptrdiff_t len = end - s;
      if (*end == '}' && len > 1 && len < 31)
	{
	  char *regname = new char[len];
	  memcpy (regname, s + 1, len - 1);
	  regname[len - 1] = '\0';
	  if (used_reg_names.add (regname))
	    delete[] regname;
	  return len + 1;
	}
    }

  error_at (loc, "error: undefined machine-specific constraint "
	    "at this point: \"%s\"", s);
  message_at (loc, "note:  in operand %d", opno);
  return 1; /* safe */
}