/* Execution of byte code produced by bytecomp.el.
   Copyright (C) 1985, 1986, 1987, 1988, 1993 Free Software Foundation, Inc.

This file is part of GNU Emacs.

GNU Emacs 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 2, or (at your option)
any later version.

GNU Emacs 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 GNU Emacs; see the file COPYING.  If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.

hacked on by jwz@lucid.com 17-jun-91
  o  added a compile-time switch to turn on simple sanity checking;
  o  put back the obsolete byte-codes for error-detection;
  o  added a new instruction, unbind_all, which I will use for 
     tail-recursion elimination;
  o  made temp_output_buffer_show be called with the right number
     of args;
  o  made the new bytecodes be called with args in the right order;
  o  added metering support.

by Hallvard:
  o  added relative jump instructions;
  o  all conditionals now only do QUIT if they jump.
 */

#include <config.h>
#include "lisp.h"
#include "buffer.h"
#include "charset.h"
#include "syntax.h"

/*
 * define BYTE_CODE_SAFE to enable some minor sanity checking (useful for 
 * debugging the byte compiler...)
 *
 * define BYTE_CODE_METER to enable generation of a byte-op usage histogram. 
 */
/* #define BYTE_CODE_SAFE */
/* #define BYTE_CODE_METER */


#ifdef BYTE_CODE_METER

Lisp_Object Vbyte_code_meter, Qbyte_code_meter;
int byte_metering_on;

#define METER_2(code1, code2) \
  XFASTINT (XVECTOR (XVECTOR (Vbyte_code_meter)->contents[(code1)]) \
	    ->contents[(code2)])

#define METER_1(code) METER_2 (0, (code))

#define METER_CODE(last_code, this_code)			\
{								\
  if (byte_metering_on)						\
    {								\
      if (METER_1 (this_code) != ((1<<VALBITS)-1))		\
        METER_1 (this_code)++;					\
      if (last_code						\
	  && METER_2 (last_code, this_code) != ((1<<VALBITS)-1))\
        METER_2 (last_code, this_code)++;			\
    }								\
}

#else /* no BYTE_CODE_METER */

#define METER_CODE(last_code, this_code)

#endif /* no BYTE_CODE_METER */


Lisp_Object Qbytecode;

/*  Byte codes: */

#define Bvarref 010
#define Bvarset 020
#define Bvarbind 030
#define Bcall 040
#define Bunbind 050

#define Bnth 070
#define Bsymbolp 071
#define Bconsp 072
#define Bstringp 073
#define Blistp 074
#define Beq 075
#define Bmemq 076
#define Bnot 077
#define Bcar 0100
#define Bcdr 0101
#define Bcons 0102
#define Blist1 0103
#define Blist2 0104
#define Blist3 0105
#define Blist4 0106
#define Blength 0107
#define Baref 0110
#define Baset 0111
#define Bsymbol_value 0112
#define Bsymbol_function 0113
#define Bset 0114
#define Bfset 0115
#define Bget 0116
#define Bsubstring 0117
#define Bconcat2 0120
#define Bconcat3 0121
#define Bconcat4 0122
#define Bsub1 0123
#define Badd1 0124
#define Beqlsign 0125
#define Bgtr 0126
#define Blss 0127
#define Bleq 0130
#define Bgeq 0131
#define Bdiff 0132
#define Bnegate 0133
#define Bplus 0134
#define Bmax 0135
#define Bmin 0136
#define Bmult 0137

#define Bpoint 0140
/* Was Bmark in v17.  */
#define Bsave_current_buffer 0141
#define Bgoto_char 0142
#define Binsert 0143
#define Bpoint_max 0144
#define Bpoint_min 0145
#define Bchar_after 0146
#define Bfollowing_char 0147
#define Bpreceding_char 0150
#define Bcurrent_column 0151
#define Bindent_to 0152
#define Bscan_buffer 0153 /* No longer generated as of v18 */
#define Beolp 0154
#define Beobp 0155
#define Bbolp 0156
#define Bbobp 0157
#define Bcurrent_buffer 0160
#define Bset_buffer 0161
#define Bsave_current_buffer_1 0162 /* Replacing Bsave_current_buffer.  */
#define Bread_char 0162 /* No longer generated as of v19 */
#define Bset_mark 0163 /* this loser is no longer generated as of v18 */
#define Binteractive_p 0164 /* Needed since interactive-p takes unevalled args */

#define Bforward_char 0165
#define Bforward_word 0166
#define Bskip_chars_forward 0167
#define Bskip_chars_backward 0170
#define Bforward_line 0171
#define Bchar_syntax 0172
#define Bbuffer_substring 0173
#define Bdelete_region 0174
#define Bnarrow_to_region 0175
#define Bwiden 0176
#define Bend_of_line 0177

#define Bconstant2 0201
#define Bgoto 0202
#define Bgotoifnil 0203
#define Bgotoifnonnil 0204
#define Bgotoifnilelsepop 0205
#define Bgotoifnonnilelsepop 0206
#define Breturn 0207
#define Bdiscard 0210
#define Bdup 0211

#define Bsave_excursion 0212
#define Bsave_window_excursion 0213
#define Bsave_restriction 0214
#define Bcatch 0215

#define Bunwind_protect 0216
#define Bcondition_case 0217
#define Btemp_output_buffer_setup 0220
#define Btemp_output_buffer_show 0221

#define Bunbind_all 0222

#define Bset_marker 0223
#define Bmatch_beginning 0224
#define Bmatch_end 0225
#define Bupcase 0226
#define Bdowncase 0227

#define Bstringeqlsign 0230
#define Bstringlss 0231
#define Bequal 0232
#define Bnthcdr 0233
#define Belt 0234
#define Bmember 0235
#define Bassq 0236
#define Bnreverse 0237
#define Bsetcar 0240
#define Bsetcdr 0241
#define Bcar_safe 0242
#define Bcdr_safe 0243
#define Bnconc 0244
#define Bquo 0245
#define Brem 0246
#define Bnumberp 0247
#define Bintegerp 0250

#define BRgoto 0252
#define BRgotoifnil 0253
#define BRgotoifnonnil 0254
#define BRgotoifnilelsepop 0255
#define BRgotoifnonnilelsepop 0256

#define BlistN 0257
#define BconcatN 0260
#define BinsertN 0261

#define Bconstant 0300
#define CONSTANTLIM 0100


/* Structure describing a value stack used during byte-code execution
   in Fbyte_code.  */

struct byte_stack
{
  /* Program counter.  This points into the byte_string below
     and is relocated when that string is relocated.  */
  unsigned char *pc;

  /* Top and bottom of stack.  The bottom points to an area of memory
     allocated with alloca in Fbyte_code.  */
  Lisp_Object *top, *bottom;

  /* The string containing the byte-code, and its current address.
     Storing this here protects it from GC because mark_byte_stack
     marks it.  */
  Lisp_Object byte_string;
  unsigned char *byte_string_start;

  /* The vector of constants used during byte-code execution.  Storing
     this here protects it from GC because mark_byte_stack marks it.  */
  Lisp_Object constants;

  /* Next entry in byte_stack_list.  */
  struct byte_stack *next;
};

/* A list of currently active byte-code execution value stacks.
   Fbyte_code adds an entry to the head of this list before it starts
   processing byte-code, and it removed the entry again when it is
   done.  Signalling an error truncates the list analoguous to
   gcprolist.  */

struct byte_stack *byte_stack_list;


/* Mark objects on byte_stack_list.  Called during GC.  */

void
mark_byte_stack ()
{
  struct byte_stack *stack;
  Lisp_Object *obj;

  for (stack = byte_stack_list; stack; stack = stack->next)
    {
      if (!stack->top)
	abort ();
      
      for (obj = stack->bottom; obj <= stack->top; ++obj)
	if (!XMARKBIT (*obj))
	  {
	    mark_object (obj);
	    XMARK (*obj);
	  }

      if (!XMARKBIT (stack->byte_string))
	{
          mark_object (&stack->byte_string);
	  XMARK (stack->byte_string);
	}

      if (!XMARKBIT (stack->constants))
	{
	  mark_object (&stack->constants);
	  XMARK (stack->constants);
	}
    }
}


/* Unmark objects in the stacks on byte_stack_list.  Relocate program
   counters.  Called when GC has completed.  */

void 
unmark_byte_stack ()
{
  struct byte_stack *stack;
  Lisp_Object *obj;

  for (stack = byte_stack_list; stack; stack = stack->next)
    {
      for (obj = stack->bottom; obj <= stack->top; ++obj)
	XUNMARK (*obj);

      XUNMARK (stack->byte_string);
      XUNMARK (stack->constants);

      if (stack->byte_string_start != XSTRING (stack->byte_string)->data)
	{
	  int offset = stack->pc - stack->byte_string_start;
	  stack->byte_string_start = XSTRING (stack->byte_string)->data;
	  stack->pc = stack->byte_string_start + offset;
	}
    }
}


/* Fetch the next byte from the bytecode stream */

#define FETCH *stack.pc++

/* Fetch two bytes from the bytecode stream and make a 16-bit number
   out of them */

#define FETCH2 (op = FETCH, op + (FETCH << 8))

/* Push x onto the execution stack.  This used to be #define PUSH(x)
   (*++stackp = (x)) This oddity is necessary because Alliant can't be
   bothered to compile the preincrement operator properly, as of 4/91.
   -JimB */

#define PUSH(x) (top++, *top = (x))

/* Pop a value off the execution stack.  */

#define POP (*top--)

/* Discard n values from the execution stack.  */

#define DISCARD(n) (top -= (n))

/* Get the value which is at the top of the execution stack, but don't
   pop it. */

#define TOP (*top)

/* Actions that must be performed before and after calling a function
   that might GC.  */

#define BEFORE_POTENTIAL_GC()	stack.top = top
#define AFTER_POTENTIAL_GC()	stack.top = NULL

/* Garbage collect if we have consed enough since the last time.
   We do this at every branch, to avoid loops that never GC.  */

#define MAYBE_GC()				\
  if (consing_since_gc > gc_cons_threshold)	\
    {						\
      BEFORE_POTENTIAL_GC ();			\
      Fgarbage_collect ();			\
      AFTER_POTENTIAL_GC ();			\
    }						\
  else

/* Check for jumping out of range.  */

#ifdef BYTE_CODE_SAFE

#define CHECK_RANGE(ARG) \
  if (ARG >= bytestr_length) abort ()

#else /* not BYTE_CODE_SAFE */

#define CHECK_RANGE(ARG)

#endif /* not BYTE_CODE_SAFE */


DEFUN ("byte-code", Fbyte_code, Sbyte_code, 3, 3, 0,
  "Function used internally in byte-compiled code.\n\
The first argument, BYTESTR, is a string of byte code;\n\
the second, VECTOR, a vector of constants;\n\
the third, MAXDEPTH, the maximum stack depth used in this function.\n\
If the third argument is incorrect, Emacs may crash.")
  (bytestr, vector, maxdepth)
     Lisp_Object bytestr, vector, maxdepth;
{
  int count = specpdl_ptr - specpdl;
#ifdef BYTE_CODE_METER
  int this_op = 0;
  int prev_op;
#endif
  int op;
  /* Lisp_Object v1, v2; */
  Lisp_Object *vectorp = XVECTOR (vector)->contents;
#ifdef BYTE_CODE_SAFE
  int const_length = XVECTOR (vector)->size;
  Lisp_Object *stacke;
#endif
  int bytestr_length = STRING_BYTES (XSTRING (bytestr));
  struct byte_stack stack;
  Lisp_Object *top;
  Lisp_Object result;

  CHECK_STRING (bytestr, 0);
  if (!VECTORP (vector))
    vector = wrong_type_argument (Qvectorp, vector);
  CHECK_NUMBER (maxdepth, 2);

  stack.byte_string = bytestr;
  stack.pc = stack.byte_string_start = XSTRING (bytestr)->data;
  stack.constants = vector;
  stack.bottom = (Lisp_Object *) alloca (XFASTINT (maxdepth) 
                                         * sizeof (Lisp_Object));
  top = stack.bottom - 1;
  stack.top = NULL;
  stack.next = byte_stack_list;
  byte_stack_list = &stack;

#ifdef BYTE_CODE_SAFE
  stacke = stack.bottom - 1 + XFASTINT (maxdepth);
#endif
  
  while (1)
    {
#ifdef BYTE_CODE_SAFE
      if (top > stacke)
	abort ();
      else if (top < stack.bottom - 1)
	abort ();
#endif

#ifdef BYTE_CODE_METER
      prev_op = this_op;
      this_op = op = FETCH;
      METER_CODE (prev_op, op);
#else
      op = FETCH;
#endif

      switch (op)
	{
	case Bvarref + 7:
	  op = FETCH2;
	  goto varref;

	case Bvarref: 
	case Bvarref + 1: 
	case Bvarref + 2: 
	case Bvarref + 3:
	case Bvarref + 4: 
	case Bvarref + 5:
	  op = op - Bvarref;
	  goto varref;

	/* This seems to be the most frequently executed byte-code
	   among the Bvarref's, so avoid a goto here.  */
	case Bvarref+6:
	  op = FETCH;
	varref:
	  {
	    Lisp_Object v1, v2;

	    v1 = vectorp[op];
	    if (SYMBOLP (v1))
	      {
		v2 = XSYMBOL (v1)->value;
		if (MISCP (v2) || EQ (v2, Qunbound))
		  v2 = Fsymbol_value (v1);
	      }
	    else
	      v2 = Fsymbol_value (v1);
	    PUSH (v2);
	    break;
	  }

	case Bgotoifnil:
	  MAYBE_GC ();
	  op = FETCH2;
	  if (NILP (POP))
	    {
	      QUIT;
	      CHECK_RANGE (op);
	      stack.pc = stack.byte_string_start + op;
	    }
	  break;

	case Bcar:
	  {
	    Lisp_Object v1;
	    v1 = TOP;
	    if (CONSP (v1))
	      TOP = XCAR (v1);
	    else if (NILP (v1))
	      TOP = Qnil;
	    else
	      {
		BEFORE_POTENTIAL_GC ();
		Fcar (wrong_type_argument (Qlistp, v1));
		AFTER_POTENTIAL_GC ();
	      }
	    break;
	  }

	case Beq:
	  {
	    Lisp_Object v1;
	    v1 = POP;
	    TOP = EQ (v1, TOP) ? Qt : Qnil;
	    break;
	  }

	case Bmemq:
	  {
	    Lisp_Object v1;
	    v1 = POP;
	    TOP = Fmemq (TOP, v1);
	    break;
	  }

	case Bcdr:
	  {
	    Lisp_Object v1;
	    v1 = TOP;
	    if (CONSP (v1))
	      TOP = XCDR (v1);
	    else if (NILP (v1))
	      TOP = Qnil;
	    else
	      {
		BEFORE_POTENTIAL_GC ();
		Fcdr (wrong_type_argument (Qlistp, v1));
		AFTER_POTENTIAL_GC ();
	      }
	    break;
	  }

	case Bvarset:
	case Bvarset+1:
	case Bvarset+2:
	case Bvarset+3:
	case Bvarset+4:
	case Bvarset+5:
	  op -= Bvarset;
	  goto varset;

	case Bvarset+7:
	  op = FETCH2;
	  goto varset;

	case Bvarset+6:
	  op = FETCH;
	varset:
	  {
	    Lisp_Object sym, val;
	      
	    sym = vectorp[op];
	    val = POP;

	    /* Inline the most common case.  */
	    if (SYMBOLP (sym)
		&& !EQ (val, Qunbound)
		&& !MISCP (XSYMBOL (sym)->value)
		/* I think this should either be checked in the byte
		   compiler, or there should be a flag indicating that
		   a symbol might be constant in Lisp_Symbol, instead
		   of checking this here over and over again. --gerd.  */
		&& !EQ (sym, Qnil)
		&& !EQ (sym, Qt)
		&& !(XSYMBOL (sym)->name->data[0] == ':'
		     && EQ (XSYMBOL (sym)->obarray, initial_obarray)
		     && !EQ (val, sym)))
	      XSYMBOL (sym)->value = val;
	    else
	      set_internal (sym, val, current_buffer, 0);
	  }
	  break;

	case Bdup:
	  {
	    Lisp_Object v1;
	    v1 = TOP;
	    PUSH (v1);
	    break;
	  }

	/* ------------------ */

	case Bvarbind+6:
	  op = FETCH;
	  goto varbind;

	case Bvarbind+7:
	  op = FETCH2;
	  goto varbind;

	case Bvarbind:
	case Bvarbind+1:
	case Bvarbind+2:
	case Bvarbind+3:
	case Bvarbind+4:
	case Bvarbind+5:
	  op -= Bvarbind;
	varbind:
	  specbind (vectorp[op], POP);
	  break;

	case Bcall+6:
	  op = FETCH;
	  goto docall;

	case Bcall+7:
	  op = FETCH2;
	  goto docall;

	case Bcall:
	case Bcall+1:
	case Bcall+2:
	case Bcall+3:
	case Bcall+4:
	case Bcall+5:
	  op -= Bcall;
	docall:
	  {
	    BEFORE_POTENTIAL_GC ();
	    DISCARD (op);
#ifdef BYTE_CODE_METER
	    if (byte_metering_on && SYMBOLP (TOP))
	      {
		Lisp_Object v1, v2;

		v1 = TOP;
		v2 = Fget (v1, Qbyte_code_meter);
		if (INTEGERP (v2)
		    && XINT (v2) != ((1<<VALBITS)-1))
		  {
		    XSETINT (v2, XINT (v2) + 1);
		    Fput (v1, Qbyte_code_meter, v2);
		  }
	      }
#endif
	    TOP = Ffuncall (op + 1, &TOP);
	    AFTER_POTENTIAL_GC ();
	    break;
	  }

	case Bunbind+6:
	  op = FETCH;
	  goto dounbind;

	case Bunbind+7:
	  op = FETCH2;
	  goto dounbind;

	case Bunbind:
	case Bunbind+1:
	case Bunbind+2:
	case Bunbind+3:
	case Bunbind+4:
	case Bunbind+5:
	  op -= Bunbind;
	dounbind:
	  BEFORE_POTENTIAL_GC ();
	  unbind_to (specpdl_ptr - specpdl - op, Qnil);
	  AFTER_POTENTIAL_GC ();
	  break;

	case Bunbind_all:
	  /* To unbind back to the beginning of this frame.  Not used yet,
	     but will be needed for tail-recursion elimination.  */
	  BEFORE_POTENTIAL_GC ();
	  unbind_to (count, Qnil);
	  AFTER_POTENTIAL_GC ();
	  break;

	case Bgoto:
	  MAYBE_GC ();
	  QUIT;
	  op = FETCH2;    /* pc = FETCH2 loses since FETCH2 contains pc++ */
	  CHECK_RANGE (op);
	  stack.pc = stack.byte_string_start + op;
	  break;

	case Bgotoifnonnil:
	  MAYBE_GC ();
	  op = FETCH2;
	  if (!NILP (POP))
	    {
	      QUIT;
	      CHECK_RANGE (op);
	      stack.pc = stack.byte_string_start + op;
	    }
	  break;

	case Bgotoifnilelsepop:
	  MAYBE_GC ();
	  op = FETCH2;
	  if (NILP (TOP))
	    {
	      QUIT;
	      CHECK_RANGE (op);
	      stack.pc = stack.byte_string_start + op;
	    }
	  else DISCARD (1);
	  break;

	case Bgotoifnonnilelsepop:
	  MAYBE_GC ();
	  op = FETCH2;
	  if (!NILP (TOP))
	    {
	      QUIT;
	      CHECK_RANGE (op);
	      stack.pc = stack.byte_string_start + op;
	    }
	  else DISCARD (1);
	  break;

	case BRgoto:
	  MAYBE_GC ();
	  QUIT;
	  stack.pc += (int) *stack.pc - 127;
	  break;

	case BRgotoifnil:
	  MAYBE_GC ();
	  if (NILP (POP))
	    {
	      QUIT;
	      stack.pc += (int) *stack.pc - 128;
	    }
	  stack.pc++;
	  break;

	case BRgotoifnonnil:
	  MAYBE_GC ();
	  if (!NILP (POP))
	    {
	      QUIT;
	      stack.pc += (int) *stack.pc - 128;
	    }
	  stack.pc++;
	  break;

	case BRgotoifnilelsepop:
	  MAYBE_GC ();
	  op = *stack.pc++;
	  if (NILP (TOP))
	    {
	      QUIT;
	      stack.pc += op - 128;
	    }
	  else DISCARD (1);
	  break;

	case BRgotoifnonnilelsepop:
	  MAYBE_GC ();
	  op = *stack.pc++;
	  if (!NILP (TOP))
	    {
	      QUIT;
	      stack.pc += op - 128;
	    }
	  else DISCARD (1);
	  break;

	case Breturn:
	  result = POP;
	  goto exit;

	case Bdiscard:
	  DISCARD (1);
	  break;

	case Bconstant2:
	  PUSH (vectorp[FETCH2]);
	  break;

	case Bsave_excursion:
	  record_unwind_protect (save_excursion_restore,
				 save_excursion_save ());
	  break;

	case Bsave_current_buffer:
	case Bsave_current_buffer_1:
	  record_unwind_protect (set_buffer_if_live, Fcurrent_buffer ());
	  break;

	case Bsave_window_excursion:
	  BEFORE_POTENTIAL_GC ();
	  TOP = Fsave_window_excursion (TOP);
	  AFTER_POTENTIAL_GC ();
	  break;

	case Bsave_restriction:
	  record_unwind_protect (save_restriction_restore,
				 save_restriction_save ());
	  break;

	case Bcatch:
	  {
	    Lisp_Object v1;
	    v1 = POP;
	    BEFORE_POTENTIAL_GC ();
	    TOP = internal_catch (TOP, Feval, v1);
	    AFTER_POTENTIAL_GC ();
	    break;
	  }

	case Bunwind_protect:
	  record_unwind_protect (0, POP);
	  (specpdl_ptr - 1)->symbol = Qnil;
	  break;

	case Bcondition_case:
	  {
	    Lisp_Object v1;
	    v1 = POP;
	    v1 = Fcons (POP, v1);
	    BEFORE_POTENTIAL_GC ();
	    TOP = Fcondition_case (Fcons (TOP, v1));
	    AFTER_POTENTIAL_GC ();
	    break;
	  }

	case Btemp_output_buffer_setup:
	  BEFORE_POTENTIAL_GC ();
	  temp_output_buffer_setup (XSTRING (TOP)->data);
	  AFTER_POTENTIAL_GC ();
	  TOP = Vstandard_output;
	  break;

	case Btemp_output_buffer_show:
	  {
	    Lisp_Object v1;
	    v1 = POP;
	    BEFORE_POTENTIAL_GC ();
	    temp_output_buffer_show (TOP);
	    TOP = v1;
	    /* pop binding of standard-output */
	    unbind_to (specpdl_ptr - specpdl - 1, Qnil);
	    AFTER_POTENTIAL_GC ();
	    break;
	  }

	case Bnth:
	  {
	    Lisp_Object v1, v2;
	    v1 = POP;
	    v2 = TOP;
	    BEFORE_POTENTIAL_GC ();
	    CHECK_NUMBER (v2, 0);
	    AFTER_POTENTIAL_GC ();
	    op = XINT (v2);
	    immediate_quit = 1;
	    while (--op >= 0)
	      {
		if (CONSP (v1))
		  v1 = XCDR (v1);
		else if (!NILP (v1))
		  {
		    immediate_quit = 0;
		    BEFORE_POTENTIAL_GC ();
		    v1 = wrong_type_argument (Qlistp, v1);
		    AFTER_POTENTIAL_GC ();
		    immediate_quit = 1;
		    op++;
		  }
	      }
	    immediate_quit = 0;
	    if (CONSP (v1))
	      TOP = XCAR (v1);
	    else if (NILP (v1))
	      TOP = Qnil;
	    else
	      {
		BEFORE_POTENTIAL_GC ();
		Fcar (wrong_type_argument (Qlistp, v1));
		AFTER_POTENTIAL_GC ();
	      }
	    break;
	  }

	case Bsymbolp:
	  TOP = SYMBOLP (TOP) ? Qt : Qnil;
	  break;

	case Bconsp:
	  TOP = CONSP (TOP) ? Qt : Qnil;
	  break;

	case Bstringp:
	  TOP = STRINGP (TOP) ? Qt : Qnil;
	  break;

	case Blistp:
	  TOP = CONSP (TOP) || NILP (TOP) ? Qt : Qnil;
	  break;

	case Bnot:
	  TOP = NILP (TOP) ? Qt : Qnil;
	  break;

	case Bcons:
	  {
	    Lisp_Object v1;
	    v1 = POP;
	    TOP = Fcons (TOP, v1);
	    break;
	  }

	case Blist1:
	  TOP = Fcons (TOP, Qnil);
	  break;

	case Blist2:
	  {
	    Lisp_Object v1;
	    v1 = POP;
	    TOP = Fcons (TOP, Fcons (v1, Qnil));
	    break;
	  }

	case Blist3:
	  DISCARD (2);
	  TOP = Flist (3, &TOP);
	  break;

	case Blist4:
	  DISCARD (3);
	  TOP = Flist (4, &TOP);
	  break;

	case BlistN:
	  op = FETCH;
	  DISCARD (op - 1);
	  TOP = Flist (op, &TOP);
	  break;

	case Blength:
	  TOP = Flength (TOP);
	  break;

	case Baref:
	  {
	    Lisp_Object v1;
	    v1 = POP;
	    TOP = Faref (TOP, v1);
	    break;
	  }

	case Baset:
	  {
	    Lisp_Object v1, v2;
	    v2 = POP; v1 = POP;
	    TOP = Faset (TOP, v1, v2);
	    break;
	  }

	case Bsymbol_value:
	  TOP = Fsymbol_value (TOP);
	  break;

	case Bsymbol_function:
	  TOP = Fsymbol_function (TOP);
	  break;

	case Bset:
	  {
	    Lisp_Object v1;
	    v1 = POP;
	    TOP = Fset (TOP, v1);
	    break;
	  }

	case Bfset:
	  {
	    Lisp_Object v1;
	    v1 = POP;
	    TOP = Ffset (TOP, v1);
	    break;
	  }

	case Bget:
	  {
	    Lisp_Object v1;
	    v1 = POP;
	    TOP = Fget (TOP, v1);
	    break;
	  }

	case Bsubstring:
	  {
	    Lisp_Object v1, v2;
	    v2 = POP; v1 = POP;
	    BEFORE_POTENTIAL_GC ();
	    TOP = Fsubstring (TOP, v1, v2);
	    AFTER_POTENTIAL_GC ();
	    break;
	  }

	case Bconcat2:
	  DISCARD (1);
	  TOP = Fconcat (2, &TOP);
	  break;

	case Bconcat3:
	  DISCARD (2);
	  TOP = Fconcat (3, &TOP);
	  break;

	case Bconcat4:
	  DISCARD (3);
	  TOP = Fconcat (4, &TOP);
	  break;

	case BconcatN:
	  op = FETCH;
	  DISCARD (op - 1);
	  TOP = Fconcat (op, &TOP);
	  break;

	case Bsub1:
	  {
	    Lisp_Object v1;
	    v1 = TOP;
	    if (INTEGERP (v1))
	      {
		XSETINT (v1, XINT (v1) - 1);
		TOP = v1;
	      }
	    else
	      TOP = Fsub1 (v1);
	    break;
	  }

	case Badd1:
	  {
	    Lisp_Object v1;
	    v1 = TOP;
	    if (INTEGERP (v1))
	      {
		XSETINT (v1, XINT (v1) + 1);
		TOP = v1;
	      }
	    else
	      TOP = Fadd1 (v1);
	    break;
	  }

	case Beqlsign:
	  {
	    Lisp_Object v1, v2;
	    v2 = POP; v1 = TOP;
	    BEFORE_POTENTIAL_GC ();
	    CHECK_NUMBER_OR_FLOAT_COERCE_MARKER (v1, 0);
	    CHECK_NUMBER_OR_FLOAT_COERCE_MARKER (v2, 0);
	    AFTER_POTENTIAL_GC ();
	    if (FLOATP (v1) || FLOATP (v2))
	      {
		double f1, f2;

		f1 = (FLOATP (v1) ? XFLOAT_DATA (v1) : XINT (v1));
		f2 = (FLOATP (v2) ? XFLOAT_DATA (v2) : XINT (v2));
		TOP = (f1 == f2 ? Qt : Qnil);
	      }
	    else
	      TOP = (XINT (v1) == XINT (v2) ? Qt : Qnil);
	    break;
	  }

	case Bgtr:
	  {
	    Lisp_Object v1;
	    v1 = POP;
	    TOP = Fgtr (TOP, v1);
	    break;
	  }

	case Blss:
	  {
	    Lisp_Object v1;
	    v1 = POP;
	    TOP = Flss (TOP, v1);
	    break;
	  }

	case Bleq:
	  {
	    Lisp_Object v1;
	    v1 = POP;
	    TOP = Fleq (TOP, v1);
	    break;
	  }

	case Bgeq:
	  {
	    Lisp_Object v1;
	    v1 = POP;
	    TOP = Fgeq (TOP, v1);
	    break;
	  }

	case Bdiff:
	  DISCARD (1);
	  TOP = Fminus (2, &TOP);
	  break;

	case Bnegate:
	  {
	    Lisp_Object v1;
	    v1 = TOP;
	    if (INTEGERP (v1))
	      {
		XSETINT (v1, - XINT (v1));
		TOP = v1;
	      }
	    else
	      TOP = Fminus (1, &TOP);
	    break;
	  }

	case Bplus:
	  DISCARD (1);
	  TOP = Fplus (2, &TOP);
	  break;

	case Bmax:
	  DISCARD (1);
	  TOP = Fmax (2, &TOP);
	  break;

	case Bmin:
	  DISCARD (1);
	  TOP = Fmin (2, &TOP);
	  break;

	case Bmult:
	  DISCARD (1);
	  TOP = Ftimes (2, &TOP);
	  break;

	case Bquo:
	  DISCARD (1);
	  TOP = Fquo (2, &TOP);
	  break;

	case Brem:
	  {
	    Lisp_Object v1;
	    v1 = POP;
	    TOP = Frem (TOP, v1);
	    break;
	  }

	case Bpoint:
	  {
	    Lisp_Object v1;
	    XSETFASTINT (v1, PT);
	    PUSH (v1);
	    break;
	  }

	case Bgoto_char:
	  BEFORE_POTENTIAL_GC ();
	  TOP = Fgoto_char (TOP);
	  AFTER_POTENTIAL_GC ();
	  break;

	case Binsert:
	  BEFORE_POTENTIAL_GC ();
	  TOP = Finsert (1, &TOP);
	  AFTER_POTENTIAL_GC ();
	  break;

	case BinsertN:
	  op = FETCH;
	  BEFORE_POTENTIAL_GC ();
	  DISCARD (op - 1);
	  TOP = Finsert (op, &TOP);
	  AFTER_POTENTIAL_GC ();
	  break;

	case Bpoint_max:
	  {
	    Lisp_Object v1;
	    XSETFASTINT (v1, ZV);
	    PUSH (v1);
	    break;
	  }

	case Bpoint_min:
	  {
	    Lisp_Object v1;
	    XSETFASTINT (v1, BEGV);
	    PUSH (v1);
	    break;
	  }

	case Bchar_after:
	  TOP = Fchar_after (TOP);
	  break;

	case Bfollowing_char:
	  {
	    Lisp_Object v1;
	    v1 = Ffollowing_char ();
	    PUSH (v1);
	    break;
	  }

	case Bpreceding_char:
	  {
	    Lisp_Object v1;
	    v1 = Fprevious_char ();
	    PUSH (v1);
	    break;
	  }

	case Bcurrent_column:
	  {
	    Lisp_Object v1;
	    XSETFASTINT (v1, current_column ());
	    PUSH (v1);
	    break;
	  }

	case Bindent_to:
	  BEFORE_POTENTIAL_GC ();
	  TOP = Findent_to (TOP, Qnil);
	  AFTER_POTENTIAL_GC ();
	  break;

	case Beolp:
	  PUSH (Feolp ());
	  break;

	case Beobp:
	  PUSH (Feobp ());
	  break;

	case Bbolp:
	  PUSH (Fbolp ());
	  break;

	case Bbobp:
	  PUSH (Fbobp ());
	  break;

	case Bcurrent_buffer:
	  PUSH (Fcurrent_buffer ());
	  break;

	case Bset_buffer:
	  BEFORE_POTENTIAL_GC ();
	  TOP = Fset_buffer (TOP);
	  AFTER_POTENTIAL_GC ();
	  break;

	case Binteractive_p:
	  PUSH (Finteractive_p ());
	  break;

	case Bforward_char:
	  BEFORE_POTENTIAL_GC ();
	  TOP = Fforward_char (TOP);
	  AFTER_POTENTIAL_GC ();
	  break;

	case Bforward_word:
	  BEFORE_POTENTIAL_GC ();
	  TOP = Fforward_word (TOP);
	  AFTER_POTENTIAL_GC ();
	  break;

	case Bskip_chars_forward:
	  {
	    Lisp_Object v1;
	    v1 = POP;
	    BEFORE_POTENTIAL_GC ();
	    TOP = Fskip_chars_forward (TOP, v1);
	    AFTER_POTENTIAL_GC ();
	    break;
	  }

	case Bskip_chars_backward:
	  {
	    Lisp_Object v1;
	    v1 = POP;
	    BEFORE_POTENTIAL_GC ();
	    TOP = Fskip_chars_backward (TOP, v1);
	    AFTER_POTENTIAL_GC ();
	    break;
	  }

	case Bforward_line:
	  BEFORE_POTENTIAL_GC ();
	  TOP = Fforward_line (TOP);
	  AFTER_POTENTIAL_GC ();
	  break;

	case Bchar_syntax:
	  BEFORE_POTENTIAL_GC ();
	  CHECK_NUMBER (TOP, 0);
	  AFTER_POTENTIAL_GC ();
	  XSETFASTINT (TOP, syntax_code_spec[(int) SYNTAX (XINT (TOP))]);
	  break;

	case Bbuffer_substring:
	  {
	    Lisp_Object v1;
	    v1 = POP;
	    BEFORE_POTENTIAL_GC ();
	    TOP = Fbuffer_substring (TOP, v1);
	    AFTER_POTENTIAL_GC ();
	    break;
	  }

	case Bdelete_region:
	  {
	    Lisp_Object v1;
	    v1 = POP;
	    BEFORE_POTENTIAL_GC ();
	    TOP = Fdelete_region (TOP, v1);
	    AFTER_POTENTIAL_GC ();
	    break;
	  }

	case Bnarrow_to_region:
	  {
	    Lisp_Object v1;
	    v1 = POP;
	    BEFORE_POTENTIAL_GC ();
	    TOP = Fnarrow_to_region (TOP, v1);
	    AFTER_POTENTIAL_GC ();
	    break;
	  }

	case Bwiden:
	  BEFORE_POTENTIAL_GC ();
	  PUSH (Fwiden ());
	  AFTER_POTENTIAL_GC ();
	  break;

	case Bend_of_line:
	  BEFORE_POTENTIAL_GC ();
	  TOP = Fend_of_line (TOP);
	  AFTER_POTENTIAL_GC ();
	  break;

	case Bset_marker:
	  {
	    Lisp_Object v1, v2;
	    v1 = POP;
	    v2 = POP;
	    TOP = Fset_marker (TOP, v2, v1);
	    break;
	  }

	case Bmatch_beginning:
	  TOP = Fmatch_beginning (TOP);
	  break;

	case Bmatch_end:
	  TOP = Fmatch_end (TOP);
	  break;

	case Bupcase:
	  TOP = Fupcase (TOP);
	  break;

	case Bdowncase:
	  TOP = Fdowncase (TOP);
	break;

	case Bstringeqlsign:
	  {
	    Lisp_Object v1;
	    v1 = POP;
	    TOP = Fstring_equal (TOP, v1);
	    break;
	  }

	case Bstringlss:
	  {
	    Lisp_Object v1;
	    v1 = POP;
	    TOP = Fstring_lessp (TOP, v1);
	    break;
	  }

	case Bequal:
	  {
	    Lisp_Object v1;
	    v1 = POP;
	    TOP = Fequal (TOP, v1);
	    break;
	  }

	case Bnthcdr:
	  {
	    Lisp_Object v1;
	    v1 = POP;
	    TOP = Fnthcdr (TOP, v1);
	    break;
	  }

	case Belt:
	  {
	    Lisp_Object v1, v2;
	    if (CONSP (TOP))
	      {
		/* Exchange args and then do nth.  */
		v2 = POP;
		v1 = TOP;
		BEFORE_POTENTIAL_GC ();
		CHECK_NUMBER (v2, 0);
		AFTER_POTENTIAL_GC ();
		op = XINT (v2);
		immediate_quit = 1;
		while (--op >= 0)
		  {
		    if (CONSP (v1))
		      v1 = XCDR (v1);
		    else if (!NILP (v1))
		      {
			immediate_quit = 0;
			BEFORE_POTENTIAL_GC ();
			v1 = wrong_type_argument (Qlistp, v1);
			AFTER_POTENTIAL_GC ();
			immediate_quit = 1;
			op++;
		      }
		  }
		immediate_quit = 0;
		if (CONSP (v1))
		  TOP = XCAR (v1);
		else if (NILP (v1))
		  TOP = Qnil;
		else
		  {
		    BEFORE_POTENTIAL_GC ();
		    Fcar (wrong_type_argument (Qlistp, v1));
		    AFTER_POTENTIAL_GC ();
		  }
	      }
	    else
	      {
		v1 = POP;
		TOP = Felt (TOP, v1);
	      }
	    break;
	  }

	case Bmember:
	  {
	    Lisp_Object v1;
	    v1 = POP;
	    TOP = Fmember (TOP, v1);
	    break;
	  }

	case Bassq:
	  {
	    Lisp_Object v1;
	    v1 = POP;
	    TOP = Fassq (TOP, v1);
	    break;
	  }

	case Bnreverse:
	  TOP = Fnreverse (TOP);
	  break;

	case Bsetcar:
	  {
	    Lisp_Object v1;
	    v1 = POP;
	    TOP = Fsetcar (TOP, v1);
	    break;
	  }

	case Bsetcdr:
	  {
	    Lisp_Object v1;
	    v1 = POP;
	    TOP = Fsetcdr (TOP, v1);
	    break;
	  }

	case Bcar_safe:
	  {
	    Lisp_Object v1;
	    v1 = TOP;
	    if (CONSP (v1))
	      TOP = XCAR (v1);
	    else
	      TOP = Qnil;
	    break;
	  }

	case Bcdr_safe:
	  {
	    Lisp_Object v1;
	    v1 = TOP;
	    if (CONSP (v1))
	      TOP = XCDR (v1);
	    else
	      TOP = Qnil;
	    break;
	  }

	case Bnconc:
	  DISCARD (1);
	  TOP = Fnconc (2, &TOP);
	  break;

	case Bnumberp:
	  TOP = (NUMBERP (TOP) ? Qt : Qnil);
	  break;

	case Bintegerp:
	  TOP = INTEGERP (TOP) ? Qt : Qnil;
	  break;

#ifdef BYTE_CODE_SAFE
	case Bset_mark:
	  BEFORE_POTENTIAL_GC ();
	  error ("set-mark is an obsolete bytecode");
	  AFTER_POTENTIAL_GC ();
	  break;
	case Bscan_buffer:
	  BEFORE_POTENTIAL_GC ();
	  error ("scan-buffer is an obsolete bytecode");
	  AFTER_POTENTIAL_GC ();
	  break;
#endif

	case 0:
	  abort ();

	case 255:
	default:
#ifdef BYTE_CODE_SAFE
	  if (op < Bconstant)
	    {
	      abort ();
	    }
	  if ((op -= Bconstant) >= const_length)
	    {
	      abort ();
	    }
	  PUSH (vectorp[op]);
#else
	  PUSH (vectorp[op - Bconstant]);
#endif
	}
    }

 exit:

  byte_stack_list = byte_stack_list->next;

  /* Binds and unbinds are supposed to be compiled balanced.  */
  if (specpdl_ptr - specpdl != count)
#ifdef BYTE_CODE_SAFE
    error ("binding stack not balanced (serious byte compiler bug)");
#else
    abort ();
#endif
  
  return result;
}

void
syms_of_bytecode ()
{
  Qbytecode = intern ("byte-code");
  staticpro (&Qbytecode);

  defsubr (&Sbyte_code);

#ifdef BYTE_CODE_METER

  DEFVAR_LISP ("byte-code-meter", &Vbyte_code_meter,
   "A vector of vectors which holds a histogram of byte-code usage.\n\
(aref (aref byte-code-meter 0) CODE) indicates how many times the byte\n\
opcode CODE has been executed.\n\
(aref (aref byte-code-meter CODE1) CODE2), where CODE1 is not 0,\n\
indicates how many times the byte opcodes CODE1 and CODE2 have been\n\
executed in succession.");
  DEFVAR_BOOL ("byte-metering-on", &byte_metering_on,
   "If non-nil, keep profiling information on byte code usage.\n\
The variable byte-code-meter indicates how often each byte opcode is used.\n\
If a symbol has a property named `byte-code-meter' whose value is an\n\
integer, it is incremented each time that symbol's function is called.");

  byte_metering_on = 0;
  Vbyte_code_meter = Fmake_vector (make_number (256), make_number (0));
  Qbyte_code_meter = intern ("byte-code-meter");
  staticpro (&Qbyte_code_meter);
  {
    int i = 256;
    while (i--)
      XVECTOR (Vbyte_code_meter)->contents[i] =
	Fmake_vector (make_number (256), make_number (0));
  }
#endif
}