File: cgen-dis.c

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/* CGEN generic disassembler support code.
   Copyright (C) 1996-2018 Free Software Foundation, Inc.

   This file is part of libopcodes.

   This library 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.

   It 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 this program; if not, write to the Free Software Foundation, Inc.,
   51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, USA.  */

#include "sysdep.h"
#include <stdio.h>
#include "ansidecl.h"
#include "libiberty.h"
#include "bfd.h"
#include "symcat.h"
#include "opcode/cgen.h"

static CGEN_INSN_LIST *  hash_insn_array        (CGEN_CPU_DESC, const CGEN_INSN *, int, int, CGEN_INSN_LIST **, CGEN_INSN_LIST *);
static CGEN_INSN_LIST *  hash_insn_list         (CGEN_CPU_DESC, const CGEN_INSN_LIST *, CGEN_INSN_LIST **, CGEN_INSN_LIST *);
static void              build_dis_hash_table   (CGEN_CPU_DESC);
static int		 count_decodable_bits   (const CGEN_INSN *);
static void		 add_insn_to_hash_chain (CGEN_INSN_LIST *,
						 const CGEN_INSN *,
						 CGEN_INSN_LIST **,
						 unsigned int);

/* Return the number of decodable bits in this insn.  */
static int
count_decodable_bits (const CGEN_INSN *insn)
{
  unsigned mask = CGEN_INSN_BASE_MASK (insn);
  int bits = 0;
  unsigned m;

  for (m = 1; m != 0; m <<= 1)
    {
      if (mask & m)
	++bits;
    }
  return bits;
}

/* Add an instruction to the hash chain.  */
static void
add_insn_to_hash_chain (CGEN_INSN_LIST *hentbuf,
			const CGEN_INSN *insn,
			CGEN_INSN_LIST **htable,
			unsigned int hash)
{
  CGEN_INSN_LIST *current_buf;
  CGEN_INSN_LIST *previous_buf;
  int insn_decodable_bits;

  /* Add insns sorted by the number of decodable bits, in decreasing order.
     This ensures that any insn which is a special case of another will be
     checked first.  */
  insn_decodable_bits = count_decodable_bits (insn);
  previous_buf = NULL;
  for (current_buf = htable[hash]; current_buf != NULL;
       current_buf = current_buf->next)
    {
      int current_decodable_bits = count_decodable_bits (current_buf->insn);
      if (insn_decodable_bits >= current_decodable_bits)
	break;
      previous_buf = current_buf;
    }

  /* Now insert the new insn.  */
  hentbuf->insn = insn;
  hentbuf->next = current_buf;
  if (previous_buf == NULL)
    htable[hash] = hentbuf;
  else
    previous_buf->next = hentbuf;
}

/* Subroutine of build_dis_hash_table to add INSNS to the hash table.

   COUNT is the number of elements in INSNS.
   ENTSIZE is sizeof (CGEN_IBASE) for the target.
   ??? No longer used but leave in for now.
   HTABLE points to the hash table.
   HENTBUF is a pointer to sufficiently large buffer of hash entries.
   The result is a pointer to the next entry to use.

   The table is scanned backwards as additions are made to the front of the
   list and we want earlier ones to be prefered.  */

static CGEN_INSN_LIST *
hash_insn_array (CGEN_CPU_DESC cd,
		 const CGEN_INSN * insns,
		 int count,
		 int entsize ATTRIBUTE_UNUSED,
		 CGEN_INSN_LIST ** htable,
		 CGEN_INSN_LIST * hentbuf)
{
  int big_p = CGEN_CPU_INSN_ENDIAN (cd) == CGEN_ENDIAN_BIG;
  int i;

  for (i = count - 1; i >= 0; --i, ++hentbuf)
    {
      unsigned int hash;
      char buf [4];
      unsigned long value;
      const CGEN_INSN *insn = &insns[i];

      if (! (* cd->dis_hash_p) (insn))
	continue;

      /* We don't know whether the target uses the buffer or the base insn
	 to hash on, so set both up.  */

      value = CGEN_INSN_BASE_VALUE (insn);
      bfd_put_bits ((bfd_vma) value,
		    buf,
		    CGEN_INSN_MASK_BITSIZE (insn),
		    big_p);
      hash = (* cd->dis_hash) (buf, value);
      add_insn_to_hash_chain (hentbuf, insn, htable, hash);
    }

  return hentbuf;
}

/* Subroutine of build_dis_hash_table to add INSNS to the hash table.
   This function is identical to hash_insn_array except the insns are
   in a list.  */

static CGEN_INSN_LIST *
hash_insn_list (CGEN_CPU_DESC cd,
		const CGEN_INSN_LIST *insns,
		CGEN_INSN_LIST **htable,
		CGEN_INSN_LIST *hentbuf)
{
  int big_p = CGEN_CPU_INSN_ENDIAN (cd) == CGEN_ENDIAN_BIG;
  const CGEN_INSN_LIST *ilist;

  for (ilist = insns; ilist != NULL; ilist = ilist->next, ++ hentbuf)
    {
      unsigned int hash;
      char buf[4];
      unsigned long value;

      if (! (* cd->dis_hash_p) (ilist->insn))
	continue;

      /* We don't know whether the target uses the buffer or the base insn
	 to hash on, so set both up.  */

      value = CGEN_INSN_BASE_VALUE (ilist->insn);
      bfd_put_bits((bfd_vma) value,
		   buf,
		   CGEN_INSN_MASK_BITSIZE (ilist->insn),
		   big_p);
      hash = (* cd->dis_hash) (buf, value);
      add_insn_to_hash_chain (hentbuf, ilist->insn, htable, hash);
    }

  return hentbuf;
}

/* Build the disassembler instruction hash table.  */

static void
build_dis_hash_table (CGEN_CPU_DESC cd)
{
  int count = cgen_insn_count (cd) + cgen_macro_insn_count (cd);
  CGEN_INSN_TABLE *insn_table = & cd->insn_table;
  CGEN_INSN_TABLE *macro_insn_table = & cd->macro_insn_table;
  unsigned int hash_size = cd->dis_hash_size;
  CGEN_INSN_LIST *hash_entry_buf;
  CGEN_INSN_LIST **dis_hash_table;
  CGEN_INSN_LIST *dis_hash_table_entries;

  /* The space allocated for the hash table consists of two parts:
     the hash table and the hash lists.  */

  dis_hash_table = (CGEN_INSN_LIST **)
    xmalloc (hash_size * sizeof (CGEN_INSN_LIST *));
  memset (dis_hash_table, 0, hash_size * sizeof (CGEN_INSN_LIST *));
  dis_hash_table_entries = hash_entry_buf = (CGEN_INSN_LIST *)
    xmalloc (count * sizeof (CGEN_INSN_LIST));

  /* Add compiled in insns.
     Don't include the first one as it is a reserved entry.  */
  /* ??? It was the end of all hash chains, and also the special
     "invalid insn" marker.  May be able to do it differently now.  */

  hash_entry_buf = hash_insn_array (cd,
				    insn_table->init_entries + 1,
				    insn_table->num_init_entries - 1,
				    insn_table->entry_size,
				    dis_hash_table, hash_entry_buf);

  /* Add compiled in macro-insns.  */

  hash_entry_buf = hash_insn_array (cd, macro_insn_table->init_entries,
				    macro_insn_table->num_init_entries,
				    macro_insn_table->entry_size,
				    dis_hash_table, hash_entry_buf);

  /* Add runtime added insns.
     Later added insns will be prefered over earlier ones.  */

  hash_entry_buf = hash_insn_list (cd, insn_table->new_entries,
				   dis_hash_table, hash_entry_buf);

  /* Add runtime added macro-insns.  */

  hash_insn_list (cd, macro_insn_table->new_entries,
		  dis_hash_table, hash_entry_buf);

  cd->dis_hash_table = dis_hash_table;
  cd->dis_hash_table_entries = dis_hash_table_entries;
}

/* Return the first entry in the hash list for INSN.  */

CGEN_INSN_LIST *
cgen_dis_lookup_insn (CGEN_CPU_DESC cd, const char * buf, CGEN_INSN_INT value)
{
  unsigned int hash;

  if (cd->dis_hash_table == NULL)
    build_dis_hash_table (cd);

  hash = (* cd->dis_hash) (buf, value);

  return cd->dis_hash_table[hash];
}