bytecode.c 34.1 KB
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/* Execution of byte code produced by bytecomp.el.
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   Copyright (C) 1985, 1986, 1987, 1988, 1993, 2000 Free Software Foundation, Inc.
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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
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the Free Software Foundation; either version 2, or (at your option)
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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
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the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.
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hacked on by jwz@lucid.com 17-jun-91
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  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;
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  o  made temp_output_buffer_show be called with the right number
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     of args;
  o  made the new bytecodes be called with args in the right order;
  o  added metering support.

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

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

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/*
 * 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. 
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 */
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/* #define BYTE_CODE_SAFE */
/* #define BYTE_CODE_METER */
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#ifdef BYTE_CODE_METER

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Lisp_Object Vbyte_code_meter, Qbyte_code_meter;
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int byte_metering_on;

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

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#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)++;			\
    }								\
}
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#else /* no BYTE_CODE_METER */
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#define METER_CODE(last_code, this_code)
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#endif /* no BYTE_CODE_METER */
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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
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#define Bsymbol_function 0113
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#define Bset 0114
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#define Bfset 0115
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#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
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/* Was Bmark in v17.  */
#define Bsave_current_buffer 0141
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#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
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#define Bsave_current_buffer_1 0162 /* Replacing Bsave_current_buffer.  */
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#define Bread_char 0162 /* No longer generated as of v19 */
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#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
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#define Bend_of_line 0177
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#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

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

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#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

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

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

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#define Bconstant 0300
#define CONSTANTLIM 0100
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228

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/* 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;

264

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/* 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)
    {
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      /* If STACK->top is null here, this means there's an opcode in
	 Fbyte_code that wasn't expected to GC, but did.  To find out
	 which opcode this is, record the value of `stack', and walk
	 up the stack in a debugger, stopping in frames of Fbyte_code.
	 The culprit is found in the frame of Fbyte_code where the
	 address of its local variable `stack' is equal to the
	 recorded value of `stack' here.  */
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      if (!stack->top)
	abort ();
      
      for (obj = stack->bottom; obj <= stack->top; ++obj)
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	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);
	}
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    }
}


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/* Unmark objects in the stacks on byte_stack_list.  Relocate program
   counters.  Called when GC has completed.  */
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void 
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unmark_byte_stack ()
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{
  struct byte_stack *stack;
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  Lisp_Object *obj;
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  for (stack = byte_stack_list; stack; stack = stack->next)
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    {
      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;
	}
    }
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}

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

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#define FETCH *stack.pc++
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/* Fetch two bytes from the bytecode stream and make a 16-bit number
   out of them */
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#define FETCH2 (op = FETCH, op + (FETCH << 8))

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/* 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 */
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#define PUSH(x) (top++, *top = (x))
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/* Pop a value off the execution stack.  */

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#define POP (*top--)
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/* Discard n values from the execution stack.  */

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#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)
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/* Actions that must be performed before and after calling a function
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   that might GC.  */
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#define BEFORE_POTENTIAL_GC()	stack.top = top
#define AFTER_POTENTIAL_GC()	stack.top = NULL
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/* 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)	\
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    {						\
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      BEFORE_POTENTIAL_GC ();			\
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      Fgarbage_collect ();			\
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      AFTER_POTENTIAL_GC ();			\
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    }						\
  else

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/* Check for jumping out of range.  */
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#ifdef BYTE_CODE_SAFE

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

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#else /* not BYTE_CODE_SAFE */
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#define CHECK_RANGE(ARG)

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#endif /* not BYTE_CODE_SAFE */
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DEFUN ("byte-code", Fbyte_code, Sbyte_code, 3, 3, 0,
  "Function used internally in byte-compiled code.\n\
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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\
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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
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  int op;
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  /* Lisp_Object v1, v2; */
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  Lisp_Object *vectorp;
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#ifdef BYTE_CODE_SAFE
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  int const_length = XVECTOR (vector)->size;
  Lisp_Object *stacke;
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#endif
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  int bytestr_length;
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  struct byte_stack stack;
  Lisp_Object *top;
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  Lisp_Object result;
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  CHECK_STRING (bytestr, 0);
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  if (!VECTORP (vector))
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    vector = wrong_type_argument (Qvectorp, vector);
  CHECK_NUMBER (maxdepth, 2);

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  if (STRING_MULTIBYTE (bytestr))
    /* BYTESTR must have been produced by Emacs 20.2 or the earlier
       because they produced a raw 8-bit string for byte-code and now
       such a byte-code string is loaded as multibyte while raw 8-bit
       characters converted to multibyte form.  Thus, now we must
       convert them back to the original unibyte form.  */
    bytestr = Fstring_as_unibyte (bytestr);

  bytestr_length = STRING_BYTES (XSTRING (bytestr));
  vectorp = XVECTOR (vector)->contents;

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

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

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

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	case Bvarref: 
	case Bvarref + 1: 
	case Bvarref + 2: 
	case Bvarref + 3:
	case Bvarref + 4: 
	case Bvarref + 5:
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	  op = op - Bvarref;
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	  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;
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	varref:
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	  {
	    Lisp_Object v1, v2;

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

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

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

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

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

	case Bcdr:
	  {
	    Lisp_Object v1;
	    v1 = TOP;
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	    if (CONSP (v1))
	      TOP = XCDR (v1);
	    else if (NILP (v1))
	      TOP = Qnil;
	    else
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	      {
		BEFORE_POTENTIAL_GC ();
		Fcdr (wrong_type_argument (Qlistp, v1));
		AFTER_POTENTIAL_GC ();
	      }
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	    break;
	  }
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	case Bvarset:
	case Bvarset+1:
	case Bvarset+2:
	case Bvarset+3:
	case Bvarset+4:
	case Bvarset+5:
	  op -= Bvarset;
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	  goto varset;

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

	case Bvarset+6:
	  op = FETCH;
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	varset:
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	  {
	    Lisp_Object sym, val;
	      
	    sym = vectorp[op];
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	    val = TOP;
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	    /* 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
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	      {
		BEFORE_POTENTIAL_GC ();
		set_internal (sym, val, current_buffer, 0);
		AFTER_POTENTIAL_GC ();
	      }
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	  }
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	  POP;
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	  break;

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

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

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

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

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	case Bvarbind:
	case Bvarbind+1:
	case Bvarbind+2:
	case Bvarbind+3:
	case Bvarbind+4:
	case Bvarbind+5:
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	  op -= Bvarbind;
	varbind:
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	  /* Specbind can signal and thus GC.  */
	  BEFORE_POTENTIAL_GC ();
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	  specbind (vectorp[op], POP);
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	  AFTER_POTENTIAL_GC ();
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	  break;

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

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

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	case Bcall:
	case Bcall+1:
	case Bcall+2:
	case Bcall+3:
	case Bcall+4:
	case Bcall+5:
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	  op -= Bcall;
	docall:
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	  {
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	    BEFORE_POTENTIAL_GC ();
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	    DISCARD (op);
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#ifdef BYTE_CODE_METER
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	    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);
		  }
	      }
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#endif
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	    TOP = Ffuncall (op + 1, &TOP);
	    AFTER_POTENTIAL_GC ();
	    break;
	  }
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	case Bunbind+6:
	  op = FETCH;
	  goto dounbind;

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

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

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

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

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

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

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

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

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

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

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

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

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	case Breturn:
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	  result = POP;
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	  goto exit;

	case Bdiscard:
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	  DISCARD (1);
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	  break;

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

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

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

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

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

	case Bcatch:
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	  {
	    Lisp_Object v1;
	    BEFORE_POTENTIAL_GC ();
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	    v1 = POP;
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	    TOP = internal_catch (TOP, Feval, v1);
	    AFTER_POTENTIAL_GC ();
	    break;
	  }
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	case Bunwind_protect:
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	  /* The function record_unwind_protect can GC.  */
	  BEFORE_POTENTIAL_GC ();
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	  record_unwind_protect (0, POP);
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	  AFTER_POTENTIAL_GC ();
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	  (specpdl_ptr - 1)->symbol = Qnil;
	  break;

	case Bcondition_case:
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	  {
	    Lisp_Object v1;
	    v1 = POP;
	    v1 = Fcons (POP, v1);
	    BEFORE_POTENTIAL_GC ();
	    TOP = Fcondition_case (Fcons (TOP, v1));
	    AFTER_POTENTIAL_GC ();
	    break;
	  }
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	case Btemp_output_buffer_setup:
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	  BEFORE_POTENTIAL_GC ();
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	  temp_output_buffer_setup (XSTRING (TOP)->data);
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	  AFTER_POTENTIAL_GC ();
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	  TOP = Vstandard_output;
	  break;

	case Btemp_output_buffer_show:
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	  {
	    Lisp_Object v1;
	    BEFORE_POTENTIAL_GC ();
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	    v1 = POP;
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	    temp_output_buffer_show (TOP);
	    TOP = v1;
	    /* pop binding of standard-output */
	    unbind_to (specpdl_ptr - specpdl - 1, Qnil);
	    AFTER_POTENTIAL_GC ();
	    break;
	  }
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	case Bnth:
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	  {
	    Lisp_Object v1, v2;
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	    BEFORE_POTENTIAL_GC ();
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	    v1 = POP;
	    v2 = TOP;
	    CHECK_NUMBER (v2, 0);
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	    AFTER_POTENTIAL_GC ();
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	    op = XINT (v2);
	    immediate_quit = 1;
	    while (--op >= 0)
	      {
		if (CONSP (v1))
		  v1 = XCDR (v1);
		else if (!NILP (v1))
		  {
		    immediate_quit = 0;
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		    BEFORE_POTENTIAL_GC ();
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		    v1 = wrong_type_argument (Qlistp, v1);
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		    AFTER_POTENTIAL_GC ();
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		    immediate_quit = 1;
		    op++;
		  }
	      }
	    immediate_quit = 0;
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	    if (CONSP (v1))
	      TOP = XCAR (v1);
	    else if (NILP (v1))
	      TOP = Qnil;
	    else
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	      {
		BEFORE_POTENTIAL_GC ();
		Fcar (wrong_type_argument (Qlistp, v1));
		AFTER_POTENTIAL_GC ();
	      }
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	    break;
	  }
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	case Bsymbolp:
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	  TOP = SYMBOLP (TOP) ? Qt : Qnil;
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	  break;

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

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

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

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

	case Bcons:
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	  {
	    Lisp_Object v1;
	    v1 = POP;
	    TOP = Fcons (TOP, v1);
	    break;
	  }
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	case Blist1:
	  TOP = Fcons (TOP, Qnil);
	  break;

	case Blist2:
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	  {
	    Lisp_Object v1;
	    v1 = POP;
	    TOP = Fcons (TOP, Fcons (v1, Qnil));
	    break;
	  }
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	case Blist3:
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	  DISCARD (2);
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	  TOP = Flist (3, &TOP);
	  break;

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

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

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

	case Baref:
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	  {
	    Lisp_Object v1;
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	    BEFORE_POTENTIAL_GC ();
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	    v1 = POP;
	    TOP = Faref (TOP, v1);
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	    AFTER_POTENTIAL_GC ();
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	    break;
	  }
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	case Baset:
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	  {
	    Lisp_Object v1, v2;
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	    BEFORE_POTENTIAL_GC ();
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	    v2 = POP; v1 = POP;
	    TOP = Faset (TOP, v1, v2);
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	    AFTER_POTENTIAL_GC ();
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	    break;
	  }
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	case Bsymbol_value:
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	  BEFORE_POTENTIAL_GC ();
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	  TOP = Fsymbol_value (TOP);
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	  AFTER_POTENTIAL_GC ();
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	  break;

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

	case Bset:
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	  {
	    Lisp_Object v1;
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	    BEFORE_POTENTIAL_GC ();
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	    v1 = POP;
	    TOP = Fset (TOP, v1);
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	    AFTER_POTENTIAL_GC ();
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	    break;
	  }
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	case Bfset:
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	  {
	    Lisp_Object v1;
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	    BEFORE_POTENTIAL_GC ();
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	    v1 = POP;
	    TOP = Ffset (TOP, v1);
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	    AFTER_POTENTIAL_GC ();
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	    break;
	  }
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	case Bget:
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	  {
	    Lisp_Object v1;
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	    BEFORE_POTENTIAL_GC ();
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	    v1 = POP;
	    TOP = Fget (TOP, v1);
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	    AFTER_POTENTIAL_GC ();
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	    break;
	  }
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	case Bsubstring:
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	  {
	    Lisp_Object v1, v2;
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	    BEFORE_POTENTIAL_GC ();
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	    v2 = POP; v1 = POP;
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	    TOP = Fsubstring (TOP, v1, v2);
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	    AFTER_POTENTIAL_GC ();
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	    break;
	  }
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	case Bconcat2:
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	  BEFORE_POTENTIAL_GC ();
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	  DISCARD (1);
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	  TOP = Fconcat (2, &TOP);
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	  AFTER_POTENTIAL_GC ();
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	  break;

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