abort always dispatches to VM bytecode, to detect same-invocation aborts

[bpt/guile.git] / libguile / vm-i-system.c

/* Copyright (C) 2001,2008,2009,2010 Free Software Foundation, Inc.
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation; either version 3 of
 * the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301 USA
 */


/* This file is included in vm_engine.c */

\f
/*
 * Basic operations
 */

VM_DEFINE_INSTRUCTION (0, nop, "nop", 0, 0, 0)
{
  NEXT;
}

VM_DEFINE_INSTRUCTION (1, halt, "halt", 0, 0, 0)
{
  HALT_HOOK ();
  nvalues = SCM_I_INUM (*sp--);
  NULLSTACK (1);
  if (nvalues == 1)
    POP (finish_args);
  else
    {
      POP_LIST (nvalues);
      POP (finish_args);
      SYNC_REGISTER ();
      finish_args = scm_values (finish_args);
    }
    
  {
#ifdef VM_ENABLE_STACK_NULLING
    SCM *old_sp = sp;
#endif

    /* Restore registers */
    sp = SCM_FRAME_LOWER_ADDRESS (fp) - 1;
    /* Setting the ip here doesn't actually affect control flow, as the calling
       code will restore its own registers, but it does help when walking the
       stack */
    ip = SCM_FRAME_RETURN_ADDRESS (fp);
    fp = SCM_FRAME_DYNAMIC_LINK (fp);
    NULLSTACK (old_sp - sp);
  }
  
  goto vm_done;
}

VM_DEFINE_INSTRUCTION (2, break, "break", 0, 0, 0)
{
  BREAK_HOOK ();
  NEXT;
}

VM_DEFINE_INSTRUCTION (3, drop, "drop", 0, 1, 0)
{
  DROP ();
  NEXT;
}

VM_DEFINE_INSTRUCTION (4, dup, "dup", 0, 0, 1)
{
  SCM x = *sp;
  PUSH (x);
  NEXT;
}

\f
/*
 * Object creation
 */

VM_DEFINE_INSTRUCTION (5, void, "void", 0, 0, 1)
{
  PUSH (SCM_UNSPECIFIED);
  NEXT;
}

VM_DEFINE_INSTRUCTION (6, make_true, "make-true", 0, 0, 1)
{
  PUSH (SCM_BOOL_T);
  NEXT;
}

VM_DEFINE_INSTRUCTION (7, make_false, "make-false", 0, 0, 1)
{
  PUSH (SCM_BOOL_F);
  NEXT;
}

VM_DEFINE_INSTRUCTION (8, make_nil, "make-nil", 0, 0, 1)
{
  PUSH (SCM_ELISP_NIL);
  NEXT;
}

VM_DEFINE_INSTRUCTION (9, make_eol, "make-eol", 0, 0, 1)
{
  PUSH (SCM_EOL);
  NEXT;
}

VM_DEFINE_INSTRUCTION (10, make_int8, "make-int8", 1, 0, 1)
{
  PUSH (SCM_I_MAKINUM ((signed char) FETCH ()));
  NEXT;
}

VM_DEFINE_INSTRUCTION (11, make_int8_0, "make-int8:0", 0, 0, 1)
{
  PUSH (SCM_INUM0);
  NEXT;
}

VM_DEFINE_INSTRUCTION (12, make_int8_1, "make-int8:1", 0, 0, 1)
{
  PUSH (SCM_I_MAKINUM (1));
  NEXT;
}

VM_DEFINE_INSTRUCTION (13, make_int16, "make-int16", 2, 0, 1)
{
  int h = FETCH ();
  int l = FETCH ();
  PUSH (SCM_I_MAKINUM ((signed short) (h << 8) + l));
  NEXT;
}

VM_DEFINE_INSTRUCTION (14, make_int64, "make-int64", 8, 0, 1)
{
  scm_t_uint64 v = 0;
  v += FETCH ();
  v <<= 8; v += FETCH ();
  v <<= 8; v += FETCH ();
  v <<= 8; v += FETCH ();
  v <<= 8; v += FETCH ();
  v <<= 8; v += FETCH ();
  v <<= 8; v += FETCH ();
  v <<= 8; v += FETCH ();
  PUSH (scm_from_int64 ((scm_t_int64) v));
  NEXT;
}

VM_DEFINE_INSTRUCTION (15, make_uint64, "make-uint64", 8, 0, 1)
{
  scm_t_uint64 v = 0;
  v += FETCH ();
  v <<= 8; v += FETCH ();
  v <<= 8; v += FETCH ();
  v <<= 8; v += FETCH ();
  v <<= 8; v += FETCH ();
  v <<= 8; v += FETCH ();
  v <<= 8; v += FETCH ();
  v <<= 8; v += FETCH ();
  PUSH (scm_from_uint64 (v));
  NEXT;
}

VM_DEFINE_INSTRUCTION (16, make_char8, "make-char8", 1, 0, 1)
{
  scm_t_uint8 v = 0;
  v = FETCH ();

  PUSH (SCM_MAKE_CHAR (v));
  /* Don't simplify this to PUSH (SCM_MAKE_CHAR (FETCH ())).  The
     contents of SCM_MAKE_CHAR may be evaluated more than once,
     resulting in a double fetch.  */
  NEXT;
}

VM_DEFINE_INSTRUCTION (17, make_char32, "make-char32", 4, 0, 1)
{
  scm_t_wchar v = 0;
  v += FETCH ();
  v <<= 8; v += FETCH ();
  v <<= 8; v += FETCH ();
  v <<= 8; v += FETCH ();
  PUSH (SCM_MAKE_CHAR (v));
  NEXT;
}



VM_DEFINE_INSTRUCTION (18, list, "list", 2, -1, 1)
{
  unsigned h = FETCH ();
  unsigned l = FETCH ();
  unsigned len = ((h << 8) + l);
  POP_LIST (len);
  NEXT;
}

VM_DEFINE_INSTRUCTION (19, vector, "vector", 2, -1, 1)
{
  unsigned h = FETCH ();
  unsigned l = FETCH ();
  unsigned len = ((h << 8) + l);
  SCM vect;
  
  SYNC_REGISTER ();
  sp++; sp -= len;
  CHECK_UNDERFLOW ();
  vect = scm_make_vector (scm_from_uint (len), SCM_BOOL_F);
  memcpy (SCM_I_VECTOR_WELTS(vect), sp, sizeof(SCM) * len);
  NULLSTACK (len);
  *sp = vect;

  NEXT;
}

\f
/*
 * Variable access
 */

#define OBJECT_REF(i)		objects[i]
#define OBJECT_SET(i,o)		objects[i] = o

#define LOCAL_REF(i)		SCM_FRAME_VARIABLE (fp, i)
#define LOCAL_SET(i,o)		SCM_FRAME_VARIABLE (fp, i) = o

/* For the variable operations, we _must_ obviously avoid function calls to
   `scm_variable_ref ()', `scm_variable_bound_p ()' and friends which do
   nothing more than the corresponding macros.  */
#define VARIABLE_REF(v)		SCM_VARIABLE_REF (v)
#define VARIABLE_SET(v,o)	SCM_VARIABLE_SET (v, o)
#define VARIABLE_BOUNDP(v)      (VARIABLE_REF (v) != SCM_UNDEFINED)

#define FREE_VARIABLE_REF(i)	SCM_PROGRAM_FREE_VARIABLE_REF (program, i)

/* ref */

VM_DEFINE_INSTRUCTION (20, object_ref, "object-ref", 1, 0, 1)
{
  register unsigned objnum = FETCH ();
  CHECK_OBJECT (objnum);
  PUSH (OBJECT_REF (objnum));
  NEXT;
}

/* FIXME: necessary? elt 255 of the vector could be a vector... */
VM_DEFINE_INSTRUCTION (21, long_object_ref, "long-object-ref", 2, 0, 1)
{
  unsigned int objnum = FETCH ();
  objnum <<= 8;
  objnum += FETCH ();
  CHECK_OBJECT (objnum);
  PUSH (OBJECT_REF (objnum));
  NEXT;
}

VM_DEFINE_INSTRUCTION (22, local_ref, "local-ref", 1, 0, 1)
{
  PUSH (LOCAL_REF (FETCH ()));
  ASSERT_BOUND (*sp);
  NEXT;
}

VM_DEFINE_INSTRUCTION (23, long_local_ref, "long-local-ref", 2, 0, 1)
{
  unsigned int i = FETCH ();
  i <<= 8;
  i += FETCH ();
  PUSH (LOCAL_REF (i));
  ASSERT_BOUND (*sp);
  NEXT;
}

VM_DEFINE_INSTRUCTION (24, local_bound, "local-bound?", 1, 0, 1)
{
  if (LOCAL_REF (FETCH ()) == SCM_UNDEFINED)
    PUSH (SCM_BOOL_F);
  else
    PUSH (SCM_BOOL_T);
  NEXT;
}

VM_DEFINE_INSTRUCTION (25, long_local_bound, "long-local-bound?", 2, 0, 1)
{
  unsigned int i = FETCH ();
  i <<= 8;
  i += FETCH ();
  if (LOCAL_REF (i) == SCM_UNDEFINED)
    PUSH (SCM_BOOL_F);
  else
    PUSH (SCM_BOOL_T);
  NEXT;
}

VM_DEFINE_INSTRUCTION (26, variable_ref, "variable-ref", 0, 1, 1)
{
  SCM x = *sp;

  if (!VARIABLE_BOUNDP (x))
    {
      finish_args = scm_list_1 (x);
      /* Was: finish_args = SCM_LIST1 (SCM_CAR (x)); */
      goto vm_error_unbound;
    }
  else
    {
      SCM o = VARIABLE_REF (x);
      *sp = o;
    }

  NEXT;
}

VM_DEFINE_INSTRUCTION (27, variable_bound, "variable-bound?", 0, 1, 1)
{
  if (VARIABLE_BOUNDP (*sp))
    *sp = SCM_BOOL_T;
  else
    *sp = SCM_BOOL_F;
  NEXT;
}

VM_DEFINE_INSTRUCTION (28, toplevel_ref, "toplevel-ref", 1, 0, 1)
{
  unsigned objnum = FETCH ();
  SCM what;
  CHECK_OBJECT (objnum);
  what = OBJECT_REF (objnum);

  if (!SCM_VARIABLEP (what)) 
    {
      SYNC_REGISTER ();
      what = resolve_variable (what, scm_program_module (program));
      if (!VARIABLE_BOUNDP (what))
        {
          finish_args = scm_list_1 (what);
          goto vm_error_unbound;
        }
      OBJECT_SET (objnum, what);
    }

  PUSH (VARIABLE_REF (what));
  NEXT;
}

VM_DEFINE_INSTRUCTION (29, long_toplevel_ref, "long-toplevel-ref", 2, 0, 1)
{
  SCM what;
  unsigned int objnum = FETCH ();
  objnum <<= 8;
  objnum += FETCH ();
  CHECK_OBJECT (objnum);
  what = OBJECT_REF (objnum);

  if (!SCM_VARIABLEP (what)) 
    {
      SYNC_REGISTER ();
      what = resolve_variable (what, scm_program_module (program));
      if (!VARIABLE_BOUNDP (what))
        {
          finish_args = scm_list_1 (what);
          goto vm_error_unbound;
        }
      OBJECT_SET (objnum, what);
    }

  PUSH (VARIABLE_REF (what));
  NEXT;
}

/* set */

VM_DEFINE_INSTRUCTION (30, local_set, "local-set", 1, 1, 0)
{
  LOCAL_SET (FETCH (), *sp);
  DROP ();
  NEXT;
}

VM_DEFINE_INSTRUCTION (31, long_local_set, "long-local-set", 2, 1, 0)
{
  unsigned int i = FETCH ();
  i <<= 8;
  i += FETCH ();
  LOCAL_SET (i, *sp);
  DROP ();
  NEXT;
}

VM_DEFINE_INSTRUCTION (32, variable_set, "variable-set", 0, 2, 0)
{
  VARIABLE_SET (sp[0], sp[-1]);
  DROPN (2);
  NEXT;
}

VM_DEFINE_INSTRUCTION (33, toplevel_set, "toplevel-set", 1, 1, 0)
{
  unsigned objnum = FETCH ();
  SCM what;
  CHECK_OBJECT (objnum);
  what = OBJECT_REF (objnum);

  if (!SCM_VARIABLEP (what)) 
    {
      SYNC_BEFORE_GC ();
      what = resolve_variable (what, scm_program_module (program));
      OBJECT_SET (objnum, what);
    }

  VARIABLE_SET (what, *sp);
  DROP ();
  NEXT;
}

VM_DEFINE_INSTRUCTION (34, long_toplevel_set, "long-toplevel-set", 2, 1, 0)
{
  SCM what;
  unsigned int objnum = FETCH ();
  objnum <<= 8;
  objnum += FETCH ();
  CHECK_OBJECT (objnum);
  what = OBJECT_REF (objnum);

  if (!SCM_VARIABLEP (what)) 
    {
      SYNC_BEFORE_GC ();
      what = resolve_variable (what, scm_program_module (program));
      OBJECT_SET (objnum, what);
    }

  VARIABLE_SET (what, *sp);
  DROP ();
  NEXT;
}

\f
/*
 * branch and jump
 */

/* offset must be at least 24 bits wide, and signed */
#define FETCH_OFFSET(offset)                    \
{						\
  offset = FETCH () << 16;                      \
  offset += FETCH () << 8;                      \
  offset += FETCH ();                           \
  offset -= (offset & (1<<23)) << 1;            \
}

#define BR(p)					\
{						\
  scm_t_int32 offset;                           \
  FETCH_OFFSET (offset);                        \
  if (p)					\
    ip += offset;                               \
  if (offset < 0)                               \
    VM_HANDLE_INTERRUPTS;                       \
  NULLSTACK (1);				\
  DROP ();					\
  NEXT;						\
}

VM_DEFINE_INSTRUCTION (35, br, "br", 3, 0, 0)
{
  scm_t_int32 offset;
  FETCH_OFFSET (offset);
  ip += offset;
  if (offset < 0)
    VM_HANDLE_INTERRUPTS;
  NEXT;
}

VM_DEFINE_INSTRUCTION (36, br_if, "br-if", 3, 0, 0)
{
  BR (scm_is_true_and_not_nil (*sp));
}

VM_DEFINE_INSTRUCTION (37, br_if_not, "br-if-not", 3, 0, 0)
{
  BR (scm_is_false_or_nil (*sp));
}

VM_DEFINE_INSTRUCTION (38, br_if_eq, "br-if-eq", 3, 0, 0)
{
  sp--; /* underflow? */
  BR (scm_is_eq (sp[0], sp[1]));
}

VM_DEFINE_INSTRUCTION (39, br_if_not_eq, "br-if-not-eq", 3, 0, 0)
{
  sp--; /* underflow? */
  BR (!scm_is_eq (sp[0], sp[1]));
}

VM_DEFINE_INSTRUCTION (40, br_if_null, "br-if-null", 3, 0, 0)
{
  BR (scm_is_null_or_nil (*sp));
}

VM_DEFINE_INSTRUCTION (41, br_if_not_null, "br-if-not-null", 3, 0, 0)
{
  BR (!scm_is_null_or_nil (*sp));
}

\f
/*
 * Subprogram call
 */

VM_DEFINE_INSTRUCTION (42, br_if_nargs_ne, "br-if-nargs-ne", 5, 0, 0)
{
  scm_t_ptrdiff n;
  scm_t_int32 offset;
  n = FETCH () << 8;
  n += FETCH ();
  FETCH_OFFSET (offset);
  if (sp - (fp - 1) != n)
    ip += offset;
  NEXT;
}

VM_DEFINE_INSTRUCTION (43, br_if_nargs_lt, "br-if-nargs-lt", 5, 0, 0)
{
  scm_t_ptrdiff n;
  scm_t_int32 offset;
  n = FETCH () << 8;
  n += FETCH ();
  FETCH_OFFSET (offset);
  if (sp - (fp - 1) < n)
    ip += offset;
  NEXT;
}

VM_DEFINE_INSTRUCTION (44, br_if_nargs_gt, "br-if-nargs-gt", 5, 0, 0)
{
  scm_t_ptrdiff n;
  scm_t_int32 offset;

  n = FETCH () << 8;
  n += FETCH ();
  FETCH_OFFSET (offset);
  if (sp - (fp - 1) > n)
    ip += offset;
  NEXT;
}

VM_DEFINE_INSTRUCTION (45, assert_nargs_ee, "assert-nargs-ee", 2, 0, 0)
{
  scm_t_ptrdiff n;
  n = FETCH () << 8;
  n += FETCH ();
  if (sp - (fp - 1) != n)
    goto vm_error_wrong_num_args;
  NEXT;
}

VM_DEFINE_INSTRUCTION (46, assert_nargs_ge, "assert-nargs-ge", 2, 0, 0)
{
  scm_t_ptrdiff n;
  n = FETCH () << 8;
  n += FETCH ();
  if (sp - (fp - 1) < n)
    goto vm_error_wrong_num_args;
  NEXT;
}

VM_DEFINE_INSTRUCTION (47, bind_optionals, "bind-optionals", 2, -1, -1)
{
  scm_t_ptrdiff n;
  n = FETCH () << 8;
  n += FETCH ();
  while (sp - (fp - 1) < n)
    PUSH (SCM_UNDEFINED);
  NEXT;
}

VM_DEFINE_INSTRUCTION (48, bind_optionals_shuffle, "bind-optionals/shuffle", 6, -1, -1)
{
  SCM *walk;
  scm_t_ptrdiff nreq, nreq_and_opt, ntotal;
  nreq = FETCH () << 8;
  nreq += FETCH ();
  nreq_and_opt = FETCH () << 8;
  nreq_and_opt += FETCH ();
  ntotal = FETCH () << 8;
  ntotal += FETCH ();

  /* look in optionals for first keyword or last positional */
  /* starting after the last required positional arg */
  walk = fp + nreq;
  while (/* while we have args */
         walk <= sp
         /* and we still have positionals to fill */
         && walk - fp < nreq_and_opt
         /* and we haven't reached a keyword yet */
         && !scm_is_keyword (*walk))
    /* bind this optional arg (by leaving it in place) */
    walk++;
  /* now shuffle up, from walk to ntotal */
  {
    scm_t_ptrdiff nshuf = sp - walk + 1, i;
    sp = (fp - 1) + ntotal + nshuf;
    CHECK_OVERFLOW ();
    for (i = 0; i < nshuf; i++)
      sp[-i] = walk[nshuf-i-1];
  }
  /* and fill optionals & keyword args with SCM_UNDEFINED */
  while (walk <= (fp - 1) + ntotal)
    *walk++ = SCM_UNDEFINED;

  NEXT;
}

/* Flags that determine whether other keywords are allowed, and whether a
   rest argument is expected.  These values must match those used by the
   glil->assembly compiler.  */
#define F_ALLOW_OTHER_KEYS  1
#define F_REST              2

VM_DEFINE_INSTRUCTION (49, bind_kwargs, "bind-kwargs", 5, 0, 0)
{
  scm_t_uint16 idx;
  scm_t_ptrdiff nkw;
  int kw_and_rest_flags;
  SCM kw;
  idx = FETCH () << 8;
  idx += FETCH ();
  /* XXX: We don't actually use NKW.  */
  nkw = FETCH () << 8;
  nkw += FETCH ();
  kw_and_rest_flags = FETCH ();

  if (!(kw_and_rest_flags & F_REST)
      && ((sp - (fp - 1) - nkw) % 2))
    goto vm_error_kwargs_length_not_even;

  CHECK_OBJECT (idx);
  kw = OBJECT_REF (idx);

  /* Switch NKW to be a negative index below SP.  */
  for (nkw = -(sp - (fp - 1) - nkw) + 1; nkw < 0; nkw++)
    {
      SCM walk;

      if (scm_is_keyword (sp[nkw]))
	{
	  for (walk = kw; scm_is_pair (walk); walk = SCM_CDR (walk))
	    {
	      if (scm_is_eq (SCM_CAAR (walk), sp[nkw]))
		{
		  SCM si = SCM_CDAR (walk);
		  LOCAL_SET (SCM_I_INUMP (si) ? SCM_I_INUM (si) : scm_to_long (si),
			     sp[nkw + 1]);
		  break;
		}
	    }
	  if (!(kw_and_rest_flags & F_ALLOW_OTHER_KEYS) && !scm_is_pair (walk))
	    goto vm_error_kwargs_unrecognized_keyword;

	  nkw++;
	}
      else if (!(kw_and_rest_flags & F_REST))
        goto vm_error_kwargs_invalid_keyword;
    }

  NEXT;
}

#undef F_ALLOW_OTHER_KEYS
#undef F_REST


VM_DEFINE_INSTRUCTION (50, push_rest, "push-rest", 2, -1, -1)
{
  scm_t_ptrdiff n;
  SCM rest = SCM_EOL;
  n = FETCH () << 8;
  n += FETCH ();
  while (sp - (fp - 1) > n)
    /* No need to check for underflow. */
    CONS (rest, *sp--, rest);
  PUSH (rest);
  NEXT;
}

VM_DEFINE_INSTRUCTION (51, bind_rest, "bind-rest", 4, -1, -1)
{
  scm_t_ptrdiff n;
  scm_t_uint32 i;
  SCM rest = SCM_EOL;
  n = FETCH () << 8;
  n += FETCH ();
  i = FETCH () << 8;
  i += FETCH ();
  while (sp - (fp - 1) > n)
    /* No need to check for underflow. */
    CONS (rest, *sp--, rest);
  LOCAL_SET (i, rest);
  NEXT;
}

VM_DEFINE_INSTRUCTION (52, reserve_locals, "reserve-locals", 2, -1, -1)
{
  SCM *old_sp;
  scm_t_int32 n;
  n = FETCH () << 8;
  n += FETCH ();
  old_sp = sp;
  sp = (fp - 1) + n;

  if (old_sp < sp)
    {
      CHECK_OVERFLOW ();
      while (old_sp < sp)
        *++old_sp = SCM_UNDEFINED;
    }
  else
    NULLSTACK (old_sp - sp);

  NEXT;
}

VM_DEFINE_INSTRUCTION (53, new_frame, "new-frame", 0, 0, 3)
{
  /* NB: if you change this, see frames.c:vm-frame-num-locals */
  /* and frames.h, vm-engine.c, etc of course */
  PUSH ((SCM)fp); /* dynamic link */
  PUSH (0);  /* mvra */
  PUSH (0);  /* ra */
  NEXT;
}

VM_DEFINE_INSTRUCTION (54, call, "call", 1, -1, 1)
{
  nargs = FETCH ();

 vm_call:
  program = sp[-nargs];

  VM_HANDLE_INTERRUPTS;

  if (SCM_UNLIKELY (!SCM_PROGRAM_P (program)))
    {
      if (SCM_STRUCTP (program) && SCM_STRUCT_APPLICABLE_P (program))
        {
          sp[-nargs] = SCM_STRUCT_PROCEDURE (program);
          goto vm_call;
        }
      else if (SCM_NIMP (program) && SCM_TYP7 (program) == scm_tc7_smob
               && SCM_SMOB_APPLICABLE_P (program))
        {
          SYNC_REGISTER ();
          sp[-nargs] = scm_i_smob_apply_trampoline (program);
          goto vm_call;
        }
      else
        goto vm_error_wrong_type_apply;
    }

  CACHE_PROGRAM ();
  fp = sp - nargs + 1;
  ASSERT (SCM_FRAME_RETURN_ADDRESS (fp) == 0);
  ASSERT (SCM_FRAME_MV_RETURN_ADDRESS (fp) == 0);
  SCM_FRAME_SET_RETURN_ADDRESS (fp, ip);
  SCM_FRAME_SET_MV_RETURN_ADDRESS (fp, 0);
  ip = SCM_C_OBJCODE_BASE (bp);
  ENTER_HOOK ();
  APPLY_HOOK ();
  NEXT;
}

VM_DEFINE_INSTRUCTION (55, tail_call, "tail-call", 1, -1, 1)
{
  nargs = FETCH ();

 vm_tail_call:
  program = sp[-nargs];

  VM_HANDLE_INTERRUPTS;

  if (SCM_UNLIKELY (!SCM_PROGRAM_P (program)))
    {
      if (SCM_STRUCTP (program) && SCM_STRUCT_APPLICABLE_P (program))
        {
          sp[-nargs] = SCM_STRUCT_PROCEDURE (program);
          goto vm_tail_call;
        }
      else if (SCM_NIMP (program) && SCM_TYP7 (program) == scm_tc7_smob
               && SCM_SMOB_APPLICABLE_P (program))
        {
          SYNC_REGISTER ();
          sp[-nargs] = scm_i_smob_apply_trampoline (program);
          goto vm_tail_call;
        }
      else
        goto vm_error_wrong_type_apply;
    }
  else
    {
      int i;
#ifdef VM_ENABLE_STACK_NULLING
      SCM *old_sp = sp;
      CHECK_STACK_LEAK ();
#endif

      EXIT_HOOK ();

      /* switch programs */
      CACHE_PROGRAM ();
      /* shuffle down the program and the arguments */
      for (i = -1, sp = sp - nargs + 1; i < nargs; i++)
        SCM_FRAME_STACK_ADDRESS (fp)[i] = sp[i];

      sp = fp + i - 1;

      NULLSTACK (old_sp - sp);

      ip = SCM_C_OBJCODE_BASE (bp);

      ENTER_HOOK ();
      APPLY_HOOK ();
      NEXT;
    }
}

VM_DEFINE_INSTRUCTION (56, subr_call, "subr-call", 1, -1, -1)
{
  SCM foreign, ret;
  SCM (*subr)();
  nargs = FETCH ();
  POP (foreign);

  subr = SCM_FOREIGN_POINTER (foreign, void);

  VM_HANDLE_INTERRUPTS;
  SYNC_REGISTER ();

  switch (nargs)
    {
    case 0:
      ret = subr ();
      break;
    case 1:
      ret = subr (sp[0]);
      break;
    case 2:
      ret = subr (sp[-1], sp[0]);
      break;
    case 3:
      ret = subr (sp[-2], sp[-1], sp[0]);
      break;
    case 4:
      ret = subr (sp[-3], sp[-2], sp[-1], sp[0]);
      break;
    case 5:
      ret = subr (sp[-4], sp[-3], sp[-2], sp[-1], sp[0]);
      break;
    case 6:
      ret = subr (sp[-5], sp[-4], sp[-3], sp[-2], sp[-1], sp[0]);
      break;
    case 7:
      ret = subr (sp[-6], sp[-5], sp[-4], sp[-3], sp[-2], sp[-1], sp[0]);
      break;
    case 8:
      ret = subr (sp[-7], sp[-6], sp[-5], sp[-4], sp[-3], sp[-2], sp[-1], sp[0]);
      break;
    case 9:
      ret = subr (sp[-8], sp[-7], sp[-6], sp[-5], sp[-4], sp[-3], sp[-2], sp[-1], sp[0]);
      break;
    case 10:
      ret = subr (sp[-9], sp[-8], sp[-7], sp[-6], sp[-5], sp[-4], sp[-3], sp[-2], sp[-1], sp[0]);
      break;
    default:
      abort ();
    }
  
  NULLSTACK_FOR_NONLOCAL_EXIT ();
      
  if (SCM_UNLIKELY (SCM_VALUESP (ret)))
    {
      /* multiple values returned to continuation */
      ret = scm_struct_ref (ret, SCM_INUM0);
      nvalues = scm_ilength (ret);
      PUSH_LIST (ret, scm_is_null);
      goto vm_return_values;
    }
  else
    {
      PUSH (ret);
      goto vm_return;
    }
}

VM_DEFINE_INSTRUCTION (57, smob_call, "smob-call", 1, -1, -1)
{
  SCM smob, ret;
  SCM (*subr)();
  nargs = FETCH ();
  POP (smob);

  subr = SCM_SMOB_DESCRIPTOR (smob).apply;

  VM_HANDLE_INTERRUPTS;
  SYNC_REGISTER ();

  switch (nargs)
    {
    case 0:
      ret = subr (smob);
      break;
    case 1:
      ret = subr (smob, sp[0]);
      break;
    case 2:
      ret = subr (smob, sp[-1], sp[0]);
      break;
    case 3:
      ret = subr (smob, sp[-2], sp[-1], sp[0]);
      break;
    default:
      abort ();
    }
  
  NULLSTACK_FOR_NONLOCAL_EXIT ();
      
  if (SCM_UNLIKELY (SCM_VALUESP (ret)))
    {
      /* multiple values returned to continuation */
      ret = scm_struct_ref (ret, SCM_INUM0);
      nvalues = scm_ilength (ret);
      PUSH_LIST (ret, scm_is_null);
      goto vm_return_values;
    }
  else
    {
      PUSH (ret);
      goto vm_return;
    }
}

VM_DEFINE_INSTRUCTION (58, foreign_call, "foreign-call", 1, -1, -1)
{
  SCM foreign, ret;
  nargs = FETCH ();
  POP (foreign);

  VM_HANDLE_INTERRUPTS;
  SYNC_REGISTER ();

  ret = scm_i_foreign_call (foreign, sp - nargs + 1);

  NULLSTACK_FOR_NONLOCAL_EXIT ();
      
  if (SCM_UNLIKELY (SCM_VALUESP (ret)))
    {
      /* multiple values returned to continuation */
      ret = scm_struct_ref (ret, SCM_INUM0);
      nvalues = scm_ilength (ret);
      PUSH_LIST (ret, scm_is_null);
      goto vm_return_values;
    }
  else
    {
      PUSH (ret);
      goto vm_return;
    }
}

VM_DEFINE_INSTRUCTION (89, continuation_call, "continuation-call", 0, -1, 0)
{
  SCM contregs;
  POP (contregs);

  scm_i_check_continuation (contregs);
  vm_return_to_continuation (scm_i_contregs_vm (contregs),
                             scm_i_contregs_vm_cont (contregs),
                             sp - (fp - 1), fp);
  scm_i_reinstate_continuation (contregs);

  /* no NEXT */
  abort ();
}

VM_DEFINE_INSTRUCTION (59, tail_call_nargs, "tail-call/nargs", 0, 0, 1)
{
  SCM x;
  POP (x);
  nargs = scm_to_int (x);
  /* FIXME: should truncate values? */
  goto vm_tail_call;
}

VM_DEFINE_INSTRUCTION (60, call_nargs, "call/nargs", 0, 0, 1)
{
  SCM x;
  POP (x);
  nargs = scm_to_int (x);
  /* FIXME: should truncate values? */
  goto vm_call;
}

VM_DEFINE_INSTRUCTION (61, mv_call, "mv-call", 4, -1, 1)
{
  scm_t_int32 offset;
  scm_t_uint8 *mvra;
  
  nargs = FETCH ();
  FETCH_OFFSET (offset);
  mvra = ip + offset;

 vm_mv_call:
  program = sp[-nargs];

  VM_HANDLE_INTERRUPTS;

  if (SCM_UNLIKELY (!SCM_PROGRAM_P (program)))
    {
      if (SCM_STRUCTP (program) && SCM_STRUCT_APPLICABLE_P (program))
        {
          sp[-nargs] = SCM_STRUCT_PROCEDURE (program);
          goto vm_mv_call;
        }
      else if (SCM_NIMP (program) && SCM_TYP7 (program) == scm_tc7_smob
               && SCM_SMOB_APPLICABLE_P (program))
        {
          SYNC_REGISTER ();
          sp[-nargs] = scm_i_smob_apply_trampoline (program);
          goto vm_mv_call;
        }
      else
        goto vm_error_wrong_type_apply;
    }

  CACHE_PROGRAM ();
  fp = sp - nargs + 1;
  ASSERT (SCM_FRAME_RETURN_ADDRESS (fp) == 0);
  ASSERT (SCM_FRAME_MV_RETURN_ADDRESS (fp) == 0);
  SCM_FRAME_SET_RETURN_ADDRESS (fp, ip);
  SCM_FRAME_SET_MV_RETURN_ADDRESS (fp, mvra);
  ip = SCM_C_OBJCODE_BASE (bp);
  ENTER_HOOK ();
  APPLY_HOOK ();
  NEXT;
}

VM_DEFINE_INSTRUCTION (62, apply, "apply", 1, -1, 1)
{
  int len;
  SCM ls;
  POP (ls);

  nargs = FETCH ();
  ASSERT (nargs >= 2);

  len = scm_ilength (ls);
  if (len < 0)
    goto vm_error_wrong_type_arg;

  PUSH_LIST (ls, SCM_NULL_OR_NIL_P);

  nargs += len - 2;
  goto vm_call;
}

VM_DEFINE_INSTRUCTION (63, tail_apply, "tail-apply", 1, -1, 1)
{
  int len;
  SCM ls;
  POP (ls);

  nargs = FETCH ();
  ASSERT (nargs >= 2);

  len = scm_ilength (ls);
  if (len < 0)
    goto vm_error_wrong_type_arg;

  PUSH_LIST (ls, SCM_NULL_OR_NIL_P);

  nargs += len - 2;
  goto vm_tail_call;
}

VM_DEFINE_INSTRUCTION (64, call_cc, "call/cc", 0, 1, 1)
{
  int first;
  SCM proc, vm_cont, cont;
  POP (proc);
  SYNC_ALL ();
  vm_cont = vm_capture_continuation (vp->stack_base, fp, sp, ip, NULL);
  cont = scm_i_make_continuation (&first, vm, vm_cont);
  if (first) 
    {
      PUSH ((SCM)fp); /* dynamic link */
      PUSH (0);  /* mvra */
      PUSH (0);  /* ra */
      PUSH (proc);
      PUSH (cont);
      nargs = 1;
      goto vm_call;
    }
  else 
    {
      /* otherwise, the vm continuation was reinstated, and
         scm_i_vm_return_to_continuation pushed on one value. So pull our regs
         back down from the vp, and march on to the next instruction. */
      CACHE_REGISTER ();
      program = SCM_FRAME_PROGRAM (fp);
      CACHE_PROGRAM ();
      NEXT;
    }
}

VM_DEFINE_INSTRUCTION (65, tail_call_cc, "tail-call/cc", 0, 1, 1)
{
  int first;
  SCM proc, vm_cont, cont;
  POP (proc);
  SYNC_ALL ();
  /* In contrast to call/cc, tail-call/cc captures the continuation without the
     stack frame. */
  vm_cont = vm_capture_continuation (vp->stack_base,
                                     SCM_FRAME_DYNAMIC_LINK (fp),
                                     SCM_FRAME_LOWER_ADDRESS (fp) - 1,
                                     SCM_FRAME_RETURN_ADDRESS (fp),
                                     SCM_FRAME_MV_RETURN_ADDRESS (fp));
  cont = scm_i_make_continuation (&first, vm, vm_cont);
  if (first) 
    {
      PUSH (proc);
      PUSH (cont);
      nargs = 1;
      goto vm_tail_call;
    }
  else
    {
      /* Otherwise, cache regs and NEXT, as above. Invoking the continuation
         does a return from the frame, either to the RA or MVRA. */
      CACHE_REGISTER ();
      program = SCM_FRAME_PROGRAM (fp);
      CACHE_PROGRAM ();
      NEXT;
    }
}

VM_DEFINE_INSTRUCTION (66, return, "return", 0, 1, 1)
{
 vm_return:
  EXIT_HOOK ();
  RETURN_HOOK (1);

  VM_HANDLE_INTERRUPTS;

  {
    SCM ret;

    POP (ret);

#ifdef VM_ENABLE_STACK_NULLING
    SCM *old_sp = sp;
#endif

    /* Restore registers */
    sp = SCM_FRAME_LOWER_ADDRESS (fp);
    ip = SCM_FRAME_RETURN_ADDRESS (fp);
    fp = SCM_FRAME_DYNAMIC_LINK (fp);

#ifdef VM_ENABLE_STACK_NULLING
    NULLSTACK (old_sp - sp);
#endif

    /* Set return value (sp is already pushed) */
    *sp = ret;
  }

  /* Restore the last program */
  program = SCM_FRAME_PROGRAM (fp);
  CACHE_PROGRAM ();
  CHECK_IP ();
  NEXT;
}

VM_DEFINE_INSTRUCTION (67, return_values, "return/values", 1, -1, -1)
{
  /* nvalues declared at top level, because for some reason gcc seems to think
     that perhaps it might be used without declaration. Fooey to that, I say. */
  nvalues = FETCH ();
 vm_return_values:
  EXIT_HOOK ();
  RETURN_HOOK (nvalues);

  VM_HANDLE_INTERRUPTS;

  if (nvalues != 1 && SCM_FRAME_MV_RETURN_ADDRESS (fp)) 
    {
      /* A multiply-valued continuation */
      SCM *vals = sp - nvalues;
      int i;
      /* Restore registers */
      sp = SCM_FRAME_LOWER_ADDRESS (fp) - 1;
      ip = SCM_FRAME_MV_RETURN_ADDRESS (fp);
      fp = SCM_FRAME_DYNAMIC_LINK (fp);
        
      /* Push return values, and the number of values */
      for (i = 0; i < nvalues; i++)
        *++sp = vals[i+1];
      *++sp = SCM_I_MAKINUM (nvalues);
             
      /* Finally null the end of the stack */
      NULLSTACK (vals + nvalues - sp);
    }
  else if (nvalues >= 1)
    {
      /* Multiple values for a single-valued continuation -- here's where I
         break with guile tradition and try and do something sensible. (Also,
         this block handles the single-valued return to an mv
         continuation.) */
      SCM *vals = sp - nvalues;
      /* Restore registers */
      sp = SCM_FRAME_LOWER_ADDRESS (fp) - 1;
      ip = SCM_FRAME_RETURN_ADDRESS (fp);
      fp = SCM_FRAME_DYNAMIC_LINK (fp);
        
      /* Push first value */
      *++sp = vals[1];
             
      /* Finally null the end of the stack */
      NULLSTACK (vals + nvalues - sp);
    }
  else
    goto vm_error_no_values;

  /* Restore the last program */
  program = SCM_FRAME_PROGRAM (fp);
  CACHE_PROGRAM ();
  CHECK_IP ();
  NEXT;
}

VM_DEFINE_INSTRUCTION (68, return_values_star, "return/values*", 1, -1, -1)
{
  SCM l;

  nvalues = FETCH ();
  ASSERT (nvalues >= 1);
    
  nvalues--;
  POP (l);
  while (scm_is_pair (l))
    {
      PUSH (SCM_CAR (l));
      l = SCM_CDR (l);
      nvalues++;
    }
  if (SCM_UNLIKELY (!SCM_NULL_OR_NIL_P (l))) {
    finish_args = scm_list_1 (l);
    goto vm_error_improper_list;
  }

  goto vm_return_values;
}

VM_DEFINE_INSTRUCTION (88, return_nvalues, "return/nvalues", 0, 1, -1)
{
  SCM n;
  POP (n);
  nvalues = scm_to_int (n);
  ASSERT (nvalues >= 0);
  goto vm_return_values;
}

VM_DEFINE_INSTRUCTION (69, truncate_values, "truncate-values", 2, -1, -1)
{
  SCM x;
  int nbinds, rest;
  POP (x);
  nvalues = scm_to_int (x);
  nbinds = FETCH ();
  rest = FETCH ();

  if (rest)
    nbinds--;

  if (nvalues < nbinds)
    goto vm_error_not_enough_values;

  if (rest)
    POP_LIST (nvalues - nbinds);
  else
    DROPN (nvalues - nbinds);

  NEXT;
}

VM_DEFINE_INSTRUCTION (70, box, "box", 1, 1, 0)
{
  SCM val;
  POP (val);
  SYNC_BEFORE_GC ();
  LOCAL_SET (FETCH (), scm_cell (scm_tc7_variable, SCM_UNPACK (val)));
  NEXT;
}

/* for letrec:
   (let ((a *undef*) (b *undef*) ...)
     (set! a (lambda () (b ...)))
     ...)
 */
VM_DEFINE_INSTRUCTION (71, empty_box, "empty-box", 1, 0, 0)
{
  SYNC_BEFORE_GC ();
  LOCAL_SET (FETCH (),
             scm_cell (scm_tc7_variable, SCM_UNPACK (SCM_UNDEFINED)));
  NEXT;
}

VM_DEFINE_INSTRUCTION (72, local_boxed_ref, "local-boxed-ref", 1, 0, 1)
{
  SCM v = LOCAL_REF (FETCH ());
  ASSERT_BOUND_VARIABLE (v);
  PUSH (VARIABLE_REF (v));
  NEXT;
}

VM_DEFINE_INSTRUCTION (73, local_boxed_set, "local-boxed-set", 1, 1, 0)
{
  SCM v, val;
  v = LOCAL_REF (FETCH ());
  POP (val);
  ASSERT_VARIABLE (v);
  VARIABLE_SET (v, val);
  NEXT;
}

VM_DEFINE_INSTRUCTION (74, free_ref, "free-ref", 1, 0, 1)
{
  scm_t_uint8 idx = FETCH ();
  
  CHECK_FREE_VARIABLE (idx);
  PUSH (FREE_VARIABLE_REF (idx));
  NEXT;
}

/* no free-set -- if a var is assigned, it should be in a box */

VM_DEFINE_INSTRUCTION (75, free_boxed_ref, "free-boxed-ref", 1, 0, 1)
{
  SCM v;
  scm_t_uint8 idx = FETCH ();
  CHECK_FREE_VARIABLE (idx);
  v = FREE_VARIABLE_REF (idx);
  ASSERT_BOUND_VARIABLE (v);
  PUSH (VARIABLE_REF (v));
  NEXT;
}

VM_DEFINE_INSTRUCTION (76, free_boxed_set, "free-boxed-set", 1, 1, 0)
{
  SCM v, val;
  scm_t_uint8 idx = FETCH ();
  POP (val);
  CHECK_FREE_VARIABLE (idx);
  v = FREE_VARIABLE_REF (idx);
  ASSERT_BOUND_VARIABLE (v);
  VARIABLE_SET (v, val);
  NEXT;
}

VM_DEFINE_INSTRUCTION (77, make_closure, "make-closure", 2, -1, 1)
{
  size_t n, len;
  SCM closure;

  len = FETCH ();
  len <<= 8;
  len += FETCH ();
  SYNC_BEFORE_GC ();
  closure = scm_words (scm_tc7_program | (len<<16), len + 3);
  SCM_SET_CELL_OBJECT_1 (closure, SCM_PROGRAM_OBJCODE (sp[-len]));
  SCM_SET_CELL_OBJECT_2 (closure, SCM_PROGRAM_OBJTABLE (sp[-len]));
  sp[-len] = closure;
  for (n = 0; n < len; n++)
    SCM_PROGRAM_FREE_VARIABLE_SET (closure, n, sp[-len + 1 + n]);
  DROPN (len);
  NEXT;
}

VM_DEFINE_INSTRUCTION (78, make_variable, "make-variable", 0, 0, 1)
{
  SYNC_BEFORE_GC ();
  /* fixme underflow */
  PUSH (scm_cell (scm_tc7_variable, SCM_UNPACK (SCM_UNDEFINED)));
  NEXT;
}

VM_DEFINE_INSTRUCTION (79, fix_closure, "fix-closure", 2, -1, 0)
{
  SCM x;
  unsigned int i = FETCH ();
  size_t n, len;
  i <<= 8;
  i += FETCH ();
  /* FIXME CHECK_LOCAL (i) */ 
  x = LOCAL_REF (i);
  /* FIXME ASSERT_PROGRAM (x); */
  len = SCM_PROGRAM_NUM_FREE_VARIABLES (x);
  for (n = 0; n < len; n++)
    SCM_PROGRAM_FREE_VARIABLE_SET (x, n, sp[-len + 1 + n]);
  DROPN (len);
  NEXT;
}

VM_DEFINE_INSTRUCTION (80, define, "define", 0, 0, 2)
{
  SCM sym, val;
  POP (sym);
  POP (val);
  SYNC_REGISTER ();
  VARIABLE_SET (scm_sym2var (sym, scm_current_module_lookup_closure (),
                             SCM_BOOL_T),
                val);
  NEXT;
}

VM_DEFINE_INSTRUCTION (81, make_keyword, "make-keyword", 0, 1, 1)
{
  CHECK_UNDERFLOW ();
  SYNC_REGISTER ();
  *sp = scm_symbol_to_keyword (*sp);
  NEXT;
}

VM_DEFINE_INSTRUCTION (82, make_symbol, "make-symbol", 0, 1, 1)
{
  CHECK_UNDERFLOW ();
  SYNC_REGISTER ();
  *sp = scm_string_to_symbol (*sp);
  NEXT;
}

VM_DEFINE_INSTRUCTION (83, prompt, "prompt", 4, 2, 0)
{
  scm_t_int32 offset;
  scm_t_uint8 escape_only_p;
  SCM k, prompt;

  escape_only_p = FETCH ();
  FETCH_OFFSET (offset);
  POP (k);

  SYNC_REGISTER ();
  /* Push the prompt onto the dynamic stack. The setjmp itself has to be local
     to this procedure. */
  /* FIXME: do more error checking */
  prompt = scm_c_make_prompt (vm, k, escape_only_p, vm_cookie);
  scm_i_set_dynwinds (scm_cons (prompt, scm_i_dynwinds ()));
  if (SCM_PROMPT_SETJMP (prompt))
    {
      /* The prompt exited nonlocally. Cache the regs back from the vp, and go
         to the handler.
      */
      CACHE_REGISTER (); /* Really we only need SP. FP and IP should be
                            unmodified. */
      ip += offset;
      NEXT;
    }
      
  /* Otherwise setjmp returned for the first time, so we go to execute the
     prompt's body. */
  NEXT;
}

VM_DEFINE_INSTRUCTION (85, wind, "wind", 0, 2, 0)
{
  SCM wind, unwind;
  POP (unwind);
  POP (wind);
  SYNC_REGISTER ();
  /* Push wind and unwind procedures onto the dynamic stack. Note that neither
     are actually called; the compiler should emit calls to wind and unwind for
     the normal dynamic-wind control flow. */
  if (SCM_UNLIKELY (scm_is_false (scm_thunk_p (wind))))
    {
      finish_args = wind;
      goto vm_error_not_a_thunk;
    }
  if (SCM_UNLIKELY (scm_is_false (scm_thunk_p (unwind))))
    {
      finish_args = unwind;
      goto vm_error_not_a_thunk;
    }
  scm_i_set_dynwinds (scm_cons (scm_cons (wind, unwind), scm_i_dynwinds ()));
  NEXT;
}

VM_DEFINE_INSTRUCTION (86, abort, "abort", 1, -1, -1)
{
  unsigned n = FETCH ();
  SYNC_REGISTER ();
  if (sp - n - 2 <= SCM_FRAME_UPPER_ADDRESS (fp))
    goto vm_error_stack_underflow;
  vm_abort (vm, n);
  /* vm_abort should not return */
  abort ();
}

VM_DEFINE_INSTRUCTION (87, unwind, "unwind", 0, 0, 0)
{
  /* A normal exit from the dynamic extent of an expression. Pop the top entry
     off of the dynamic stack. */
  scm_i_set_dynwinds (scm_cdr (scm_i_dynwinds ()));
  NEXT;
}

VM_DEFINE_INSTRUCTION (90, wind_fluids, "wind-fluids", 1, -1, 0)
{
  unsigned n = FETCH ();
  SCM wf;
  
  if (sp - 2*n < SCM_FRAME_UPPER_ADDRESS (fp))
    goto vm_error_stack_underflow;

  wf = scm_i_make_with_fluids (n, sp + 1 - 2*n, sp + 1 - n);
  scm_i_swap_with_fluids (wf, dynstate);
  scm_i_set_dynwinds (scm_cons (wf, scm_i_dynwinds ()));
  NEXT;
}

VM_DEFINE_INSTRUCTION (91, unwind_fluids, "unwind-fluids", 0, 0, 0)
{
  SCM wf;
  wf = scm_car (scm_i_dynwinds ());
  scm_i_set_dynwinds (scm_cdr (scm_i_dynwinds ()));
  scm_i_swap_with_fluids (wf, dynstate);
  NEXT;
}

VM_DEFINE_INSTRUCTION (92, fluid_ref, "fluid-ref", 0, 1, 1)
{
  size_t num;
  SCM fluids;
  
  CHECK_UNDERFLOW ();
  fluids = SCM_I_DYNAMIC_STATE_FLUIDS (dynstate);
  if (SCM_UNLIKELY (!SCM_I_FLUID_P (*sp))
      || ((num = SCM_I_FLUID_NUM (*sp)) >= SCM_SIMPLE_VECTOR_LENGTH (fluids)))
    {
      /* Punt dynstate expansion and error handling to the C proc. */
      SYNC_REGISTER ();
      *sp = scm_fluid_ref (*sp);
    }
  else
    *sp = SCM_SIMPLE_VECTOR_REF (fluids, num);
  
  NEXT;
}

VM_DEFINE_INSTRUCTION (93, fluid_set, "fluid-set", 0, 2, 0)
{
  size_t num;
  SCM val, fluid, fluids;
  
  POP (val);
  POP (fluid);
  fluids = SCM_I_DYNAMIC_STATE_FLUIDS (dynstate);
  if (SCM_UNLIKELY (!SCM_I_FLUID_P (fluid))
      || ((num = SCM_I_FLUID_NUM (fluid)) >= SCM_SIMPLE_VECTOR_LENGTH (fluids)))
    {
      /* Punt dynstate expansion and error handling to the C proc. */
      SYNC_REGISTER ();
      scm_fluid_set_x (fluid, val);
    }
  else
    SCM_SIMPLE_VECTOR_SET (fluids, num, val);
  
  NEXT;
}


/*
(defun renumber-ops ()
  "start from top of buffer and renumber 'VM_DEFINE_FOO (\n' sequences"
  (interactive "")
  (save-excursion
    (let ((counter -1)) (goto-char (point-min))
      (while (re-search-forward "^VM_DEFINE_[^ ]+ (\\([^,]+\\)," (point-max) t)
        (replace-match
         (number-to-string (setq counter (1+ counter)))
          t t nil 1)))))
(renumber-ops)
*/
/*
  Local Variables:
  c-file-style: "gnu"
  End:
*/