ocaml/byterun/interp.c

/***********************************************************************/
/*                                                                     */
/*                           Objective Caml                            */
/*                                                                     */
/*            Xavier Leroy, projet Cristal, INRIA Rocquencourt         */
/*                                                                     */
/*  Copyright 1996 Institut National de Recherche en Informatique et   */
/*  Automatique.  Distributed only by permission.                      */
/*                                                                     */
/***********************************************************************/

/* $Id$ */

/* The bytecode interpreter */

#include "alloc.h"
#include "callback.h"
#include "debugger.h"
#include "fail.h"
#include "fix_code.h"
#include "instrtrace.h"
#include "instruct.h"
#include "interp.h"
#include "major_gc.h"
#include "memory.h"
#include "misc.h"
#include "mlvalues.h"
#include "prims.h"
#include "signals.h"
#include "stacks.h"
#include "str.h"

#if macintosh
#include "rotatecursor.h"
extern int volatile have_to_interact;
#endif

/* Registers for the abstract machine:
        pc         the code pointer
        sp         the stack pointer (grows downward)
        accu       the accumulator
        env        heap-allocated environment
        trapsp     pointer to the current trap frame
        extra_args number of extra arguments provided by the caller

sp is a local copy of the global variable extern_sp. */

/* Instruction decoding */

#ifdef THREADED_CODE
#  define Instruct(name) lbl_##name
#  if defined(ARCH_SIXTYFOUR) && !defined(ARCH_CODE32)
#    define Jumptbl_base ((char *) &&lbl_ACC0)
#  else
#    define Jumptbl_base ((char *) 0)
#    define jumptbl_base ((char *) 0)
#  endif
#  ifdef DEBUG
#    define Next goto next_instr
#  else
#    define Next goto *(void *)(jumptbl_base + *pc++)
#  endif
#else
#  define Instruct(name) case name
#  define Next break
#endif

/* GC interface */

#define Setup_for_gc { sp -= 2; sp[0] = accu; sp[1] = env; extern_sp = sp; }
#define Restore_after_gc { accu = sp[0]; env = sp[1]; sp += 2; }
#define Setup_for_c_call { *--sp = env; extern_sp = sp; }
#define Restore_after_c_call { sp = extern_sp; env = *sp++; }

/* Debugger interface */

#define Setup_for_debugger \
   { sp -= 4; \
     sp[0] = accu; sp[1] = (value)(pc - 1); \
     sp[2] = env; sp[3] = Val_long(extra_args); \
     extern_sp = sp; }
#define Restore_after_debugger { sp += 4; }

#ifdef THREADED_CODE
#define Restart_curr_instr \
  goto *(jumptable[saved_code[pc - 1 - start_code]])
#else
#define Restart_curr_instr \
  curr_instr = saved_code[pc - 1 - start_code]; \
  goto dispatch_instr
#endif

/* Register optimization.
   Some compilers underestimate the use of the local variables representing
   the abstract machine registers, and don't put them in hardware registers,
   which slows down the interpreter considerably.
   For GCC, I have hand-assigned hardware registers for several architectures.
*/

#if defined(__GNUC__) && !defined(DEBUG)
#ifdef __mips__
#define PC_REG asm("$16")
#define SP_REG asm("$17")
#define ACCU_REG asm("$18")
#endif
#ifdef __sparc__
#define PC_REG asm("%l0")
#define SP_REG asm("%l1")
#define ACCU_REG asm("%l2")
#endif
#ifdef __alpha__
#define PC_REG asm("$9")
#define SP_REG asm("$10")
#define ACCU_REG asm("$11")
#define JUMPTBL_BASE_REG asm("$12")
#endif
#ifdef __i386__
#define PC_REG asm("%esi")
#define SP_REG asm("%edi")
#define ACCU_REG asm("%ebx")
#endif
#if defined(PPC) || defined(_POWER) || defined(_IBMR2)
#define PC_REG asm("26")
#define SP_REG asm("27")
#define ACCU_REG asm("28")
#endif
#ifdef __hppa__
#define PC_REG asm("%r18")
#define SP_REG asm("%r17")
#define ACCU_REG asm("%r16")
#endif
#ifdef __mc68000__
#define PC_REG asm("a5")
#define SP_REG asm("a4")
#define ACCU_REG asm("d7")
#endif
#endif

/* The interpreter itself */

value interprete(prog, prog_size)
     code_t prog;
     asize_t prog_size;
{
#ifdef PC_REG
  register code_t pc PC_REG;
  register value * sp SP_REG;
  register value accu ACCU_REG;
#else
  register code_t pc;
  register value * sp;
  register value accu;
#endif
#if defined(THREADED_CODE) && defined(ARCH_SIXTYFOUR) && !defined(ARCH_CODE32)
#ifdef JUMPTBL_BASE_REG
  register char * jumptbl_base JUMPTBL_BASE_REG;
#else
  register char * jumptbl_base;
#endif
#endif
  value env;
  long extra_args;
  struct longjmp_buffer * initial_external_raise;
  int initial_sp_offset;
  value * initial_local_roots;
  struct caml__roots_block *initial_local_roots_new;
  int initial_callback_depth;
  struct longjmp_buffer raise_buf;
  value * modify_dest, modify_newval;
  opcode_t curr_instr;

#ifdef THREADED_CODE
  static void * jumptable[] = {
#    include "jumptbl.h"
  };
#endif

  if (prog == NULL) {           /* Interpreter is initializing */
#ifdef THREADED_CODE
    instr_table = (char **) jumptable; 
    instr_base = Jumptbl_base;
#endif
    return Val_unit;
  }

#if defined(THREADED_CODE) && defined(ARCH_SIXTYFOUR) && !defined(ARCH_CODE32)
  jumptbl_base = Jumptbl_base;
#endif
  sp = extern_sp;
  pc = prog;
  extra_args = 0;
  env = Atom(0);
  accu = Val_int(0);
  initial_local_roots = local_roots;
  initial_local_roots_new = local_roots_new;
  initial_sp_offset = stack_high - sp;
  initial_external_raise = external_raise;
  initial_callback_depth = callback_depth;
  if (sigsetjmp(raise_buf.buf, 1)) {
    local_roots = initial_local_roots;
    local_roots_new = initial_local_roots_new;
    callback_depth = initial_callback_depth;
    accu = exn_bucket;
    sp = extern_sp;
    goto raise_exception;
  }
  external_raise = &raise_buf;

#ifdef THREADED_CODE
#ifdef DEBUG
 next_instr:
  if (icount-- == 0) stop_here ();
  Assert(sp >= stack_low);
  Assert(sp <= stack_high);
#endif
  goto *(void *)(jumptbl_base + *pc++); /* Jump to the first instruction */
#else
  while(1) {
#ifdef DEBUG
    if (icount-- == 0) stop_here ();
    if (trace_flag) disasm_instr(pc);
    Assert(sp >= stack_low);
    Assert(sp <= stack_high);
#endif
    curr_instr = *pc++;
  dispatch_instr:
    switch(curr_instr) {
#endif

/* Basic stack operations */

    Instruct(ACC0):
      accu = sp[0]; Next;
    Instruct(ACC1):
      accu = sp[1]; Next;
    Instruct(ACC2):
      accu = sp[2]; Next;
    Instruct(ACC3):
      accu = sp[3]; Next;
    Instruct(ACC4):
      accu = sp[4]; Next;
    Instruct(ACC5):
      accu = sp[5]; Next;
    Instruct(ACC6):
      accu = sp[6]; Next;
    Instruct(ACC7):
      accu = sp[7]; Next;

    Instruct(PUSH): Instruct(PUSHACC0):
      *--sp = accu; Next;
    Instruct(PUSHACC1):
      *--sp = accu; accu = sp[1]; Next;
    Instruct(PUSHACC2):
      *--sp = accu; accu = sp[2]; Next;
    Instruct(PUSHACC3):
      *--sp = accu; accu = sp[3]; Next;
    Instruct(PUSHACC4):
      *--sp = accu; accu = sp[4]; Next;
    Instruct(PUSHACC5):
      *--sp = accu; accu = sp[5]; Next;
    Instruct(PUSHACC6):
      *--sp = accu; accu = sp[6]; Next;
    Instruct(PUSHACC7):
      *--sp = accu; accu = sp[7]; Next;

    Instruct(PUSHACC):
      *--sp = accu;
      /* Fallthrough */
    Instruct(ACC):
      accu = sp[*pc++];
      Next;

    Instruct(POP):
      sp += *pc++;
      Next;
    Instruct(ASSIGN):
      sp[*pc++] = accu;
      accu = Val_unit;
      Next;

/* Access in heap-allocated environment */

    Instruct(ENVACC1):
      accu = Field(env, 1); Next;
    Instruct(ENVACC2):
      accu = Field(env, 2); Next;
    Instruct(ENVACC3):
      accu = Field(env, 3); Next;
    Instruct(ENVACC4):
      accu = Field(env, 4); Next;

    Instruct(PUSHENVACC1):
      *--sp = accu; accu = Field(env, 1); Next;
    Instruct(PUSHENVACC2):
      *--sp = accu; accu = Field(env, 2); Next;
    Instruct(PUSHENVACC3):
      *--sp = accu; accu = Field(env, 3); Next;
    Instruct(PUSHENVACC4):
      *--sp = accu; accu = Field(env, 4); Next;

    Instruct(PUSHENVACC):
      *--sp = accu;
      /* Fallthrough */
    Instruct(ENVACC):
      accu = Field(env, *pc++);
      Next;

/* Function application */

    Instruct(PUSH_RETADDR): {
      sp -= 3;
      sp[0] = (value) (pc + *pc);
      sp[1] = env;
      sp[2] = Val_long(extra_args);
      pc++;
      Next;
    }
    Instruct(APPLY): {
      extra_args = *pc - 1;
      pc = Code_val(accu);
      env = accu;
      goto check_stacks;
    }
    Instruct(APPLY1): {
      value arg1 = sp[0];
      sp -= 3;
      sp[0] = arg1;
      sp[1] = (value)pc;
      sp[2] = env;
      sp[3] = Val_long(extra_args);
      pc = Code_val(accu);
      env = accu;
      extra_args = 0;
      goto check_stacks;
    }
    Instruct(APPLY2): {
      value arg1 = sp[0];
      value arg2 = sp[1];
      sp -= 3;
      sp[0] = arg1;
      sp[1] = arg2;
      sp[2] = (value)pc;
      sp[3] = env;
      sp[4] = Val_long(extra_args);
      pc = Code_val(accu);
      env = accu;
      extra_args = 1;
      goto check_stacks;
    }
    Instruct(APPLY3): {
      value arg1 = sp[0];
      value arg2 = sp[1];
      value arg3 = sp[2];
      sp -= 3;
      sp[0] = arg1;
      sp[1] = arg2;
      sp[2] = arg3;
      sp[3] = (value)pc;
      sp[4] = env;
      sp[5] = Val_long(extra_args);
      pc = Code_val(accu);
      env = accu;
      extra_args = 2;
      goto check_stacks;
    }

    Instruct(APPTERM): {
      int nargs = *pc++;
      int slotsize = *pc;
      value * newsp;
      int i;
      /* Slide the nargs bottom words of the current frame to the top
         of the frame, and discard the remainder of the frame */
      newsp = sp + slotsize - nargs;
      for (i = nargs - 1; i >= 0; i--) newsp[i] = sp[i];
      sp = newsp;
      pc = Code_val(accu);
      env = accu;
      extra_args += nargs - 1;
      goto check_stacks;
    }
    Instruct(APPTERM1): {
      value arg1 = sp[0];
      sp = sp + *pc - 1;
      sp[0] = arg1;
      pc = Code_val(accu);
      env = accu;
      goto check_stacks;
    }
    Instruct(APPTERM2): {
      value arg1 = sp[0];
      value arg2 = sp[1];
      sp = sp + *pc - 2;
      sp[0] = arg1;
      sp[1] = arg2;
      pc = Code_val(accu);
      env = accu;
      extra_args += 1;
      goto check_stacks;
    }
    Instruct(APPTERM3): {
      value arg1 = sp[0];
      value arg2 = sp[1];
      value arg3 = sp[2];
      sp = sp + *pc - 3;
      sp[0] = arg1;
      sp[1] = arg2;
      sp[2] = arg3;
      pc = Code_val(accu);
      env = accu;
      extra_args += 2;
      goto check_stacks;
    }

    Instruct(RETURN): {
      sp += *pc++;
      if (extra_args > 0) {
        extra_args--;
        pc = Code_val(accu);
        env = accu;
      } else {
        pc = (code_t)(sp[0]);
        env = sp[1];
        extra_args = Long_val(sp[2]);
        sp += 3;
      }
      Next;
    }

    Instruct(RESTART): {
      int num_args = Wosize_val(env) - 2;
      int i;
      sp -= num_args;
      for (i = 0; i < num_args; i++) sp[i] = Field(env, i + 2);
      env = Field(env, 1);
      extra_args += num_args;
      Next;
    }

    Instruct(GRAB): {
      int required = *pc++;
      if (extra_args >= required) {
        extra_args -= required;
      } else {
        mlsize_t num_args, i;
        num_args = 1 + extra_args; /* arg1 + extra args */
        Alloc_small(accu, num_args + 2, Closure_tag);
        Field(accu, 1) = env;
        for (i = 0; i < num_args; i++) Field(accu, i + 2) = sp[i];
        Code_val(accu) = pc - 3; /* Point to the preceding RESTART instr. */
        sp += num_args;
        pc = (code_t)(sp[0]);
        env = sp[1];
        extra_args = Long_val(sp[2]);
        sp += 3;
      }
      Next;
    }

    Instruct(CLOSURE): {
      int nvars = *pc++;
      int i;
      if (nvars > 0) *--sp = accu;
      Alloc_small(accu, 1 + nvars, Closure_tag);
      Code_val(accu) = pc + *pc;
      for (i = 0; i < nvars; i++) Field(accu, i + 1) = sp[i];
      sp += nvars;
      pc++;
      Next;
    }

    Instruct(CLOSUREREC): {
      int nvars = *pc++;
      int i;
      if (nvars > 0) *--sp = accu;
      Alloc_small(accu, 2 + nvars, Closure_tag);
      Code_val(accu) = pc + *pc;
      Field(accu, 1) = Val_int(0);
      for (i = 0; i < nvars; i++) Field(accu, i + 2) = sp[i];
      sp += nvars;
      modify(&Field(accu, 1), accu);
      pc++;
      Next;
    }

    Instruct(PUSHGETGLOBAL):
      *--sp = accu;
      /* Fallthrough */
    Instruct(GETGLOBAL):
      accu = Field(global_data, *pc);
      pc++;
      Next;

    Instruct(PUSHGETGLOBALFIELD):
      *--sp = accu;
      /* Fallthrough */
    Instruct(GETGLOBALFIELD): {
      accu = Field(global_data, *pc);
      pc++;
      accu = Field(accu, *pc);
      pc++;
      Next;
    }

    Instruct(SETGLOBAL):
      modify(&Field(global_data, *pc), accu);
      accu = Val_unit;
      pc++;
      Next;

/* Allocation of blocks */

    Instruct(PUSHATOM0):
      *--sp = accu;
      /* Fallthrough */
    Instruct(ATOM0):
      accu = Atom(0); Next;

    Instruct(PUSHATOM):
      *--sp = accu;
      /* Fallthrough */
    Instruct(ATOM):
      accu = Atom(*pc++); Next;

    Instruct(MAKEBLOCK): {
      mlsize_t wosize = *pc++;
      tag_t tag = *pc++;
      mlsize_t i;
      value block;
      Alloc_small(block, wosize, tag);
      Field(block, 0) = accu;
      for (i = 1; i < wosize; i++) Field(block, i) = *sp++;
      accu = block;
      Next;
    }
    Instruct(MAKEBLOCK1): {
      tag_t tag = *pc++;
      value block;
      Alloc_small(block, 1, tag);
      Field(block, 0) = accu;
      accu = block;
      Next;
    }
    Instruct(MAKEBLOCK2): {
      tag_t tag = *pc++;
      value block;
      Alloc_small(block, 2, tag);
      Field(block, 0) = accu;
      Field(block, 1) = sp[0];
      sp += 1;
      accu = block;
      Next;
    }
    Instruct(MAKEBLOCK3): {
      tag_t tag = *pc++;
      value block;
      Alloc_small(block, 3, tag);
      Field(block, 0) = accu;
      Field(block, 1) = sp[0];
      Field(block, 2) = sp[1];
      sp += 2;
      accu = block;
      Next;
    }

/* Access to components of blocks */

    Instruct(GETFIELD0):
      accu = Field(accu, 0); Next;
    Instruct(GETFIELD1):
      accu = Field(accu, 1); Next;
    Instruct(GETFIELD2):
      accu = Field(accu, 2); Next;
    Instruct(GETFIELD3):
      accu = Field(accu, 3); Next;
    Instruct(GETFIELD):
      accu = Field(accu, *pc); pc++; Next;

    Instruct(SETFIELD0):
      modify_dest = &Field(accu, 0);
      modify_newval = *sp++;
    modify:
      Modify(modify_dest, modify_newval);
      accu = Val_unit;
      Next;
    Instruct(SETFIELD1):
      modify_dest = &Field(accu, 1);
      modify_newval = *sp++;
      goto modify;
    Instruct(SETFIELD2):
      modify_dest = &Field(accu, 2);
      modify_newval = *sp++;
      goto modify;
    Instruct(SETFIELD3):
      modify_dest = &Field(accu, 3);
      modify_newval = *sp++;
      goto modify;
    Instruct(SETFIELD):
      modify_dest = &Field(accu, *pc);
      pc++;
      modify_newval = *sp++;
      goto modify;

/* For recursive definitions */

    Instruct(DUMMY): {
      int size = *pc++;
      Alloc_small(accu, size, 0);
      while (size--) Field(accu, size) = Val_long(0);
      Next;
    }
    Instruct(UPDATE): {
      value newval = *sp++;
      mlsize_t size, n;
      size = Wosize_val(newval);
      Assert(size == Wosize_val(accu));
      Tag_val(accu) = Tag_val(newval);
      for (n = 0; n < size; n++) {
        modify(&Field(accu, n), Field(newval, n));
      }
      accu = Val_unit;
      Next;
    }

/* Array operations */

    Instruct(VECTLENGTH):
      accu = Val_long(Wosize_val(accu));
      Next;
    Instruct(GETVECTITEM):
      accu = Field(accu, Long_val(sp[0]));
      sp += 1;
      Next;
    Instruct(SETVECTITEM):
      modify_dest = &Field(accu, Long_val(sp[0]));
      modify_newval = sp[1];
      sp += 2;
      goto modify;

/* String operations */

    Instruct(GETSTRINGCHAR):
      accu = Val_int(Byte_u(accu, Long_val(sp[0])));
      sp += 1;
      Next;
    Instruct(SETSTRINGCHAR):
      Byte_u(accu, Long_val(sp[0])) = Int_val(sp[1]);
      sp += 2;
      accu = Val_unit;
      Next;

/* Branches and conditional branches */

    Instruct(BRANCH):
      pc += *pc;
      Next;
    Instruct(BRANCHIF):
      if (accu != Val_false) pc += *pc; else pc++;
      Next;
    Instruct(BRANCHIFNOT):
      if (accu == Val_false) pc += *pc; else pc++;
      Next;
    Instruct(SWITCH): {
      uint32 sizes = *pc++;
      if (Is_block(accu)) {
        long index = Tag_val(accu);
        Assert(index >= 0 && index < (sizes >> 16));
        pc += pc[(sizes & 0xFFFF) + index];
      } else {
        long index = Long_val(accu);
        if ((unsigned long) index < (sizes & 0xFFFF))
          pc += pc[index];
        else
          pc += (sizes & 0xFFFF) + (sizes >> 16);
      }
      Next;
    }
    Instruct(BOOLNOT):
      accu = Val_not(accu);
      Next;

/* Exceptions */

    Instruct(PUSHTRAP):
      sp -= 4;
      Trap_pc(sp) = pc + *pc;
      Trap_link(sp) = trapsp;
      sp[2] = env;
      sp[3] = Val_long(extra_args);
      trapsp = sp;
      pc++;
      Next;

    Instruct(POPTRAP):
      /* We should check here if a signal is pending, to preserve the
         semantics of the program w.r.t. exceptions. Unfortunately,
         process_signal destroys the accumulator, and there is no
         convenient way to preserve it... */
      trapsp = Trap_link(sp);
      sp += 4;
      Next;

    Instruct(RAISE):
    raise_exception:
      if (trapsp >= trap_barrier) {
        Setup_for_debugger;
        debugger(TRAP_BARRIER);
        Restore_after_debugger;
      }
      sp = trapsp;
      if (sp >= stack_high - initial_sp_offset) {
        exn_bucket = accu;
        external_raise = initial_external_raise;
        siglongjmp(external_raise->buf, 1);
      }
      pc = Trap_pc(sp);
      trapsp = Trap_link(sp);
      env = sp[2];
      extra_args = Long_val(sp[3]);
      sp += 4;
      Next;

/* Stack checks */

    check_stacks:
      if (sp < stack_threshold) {
        extern_sp = sp;
        realloc_stack();
        sp = extern_sp;
      }
      /* Fall through CHECK_SIGNALS */

/* Signal handling */

    Instruct(CHECK_SIGNALS):    /* accu not preserved */
      if (something_to_do) goto process_signal;
      Next;

    process_signal:
      something_to_do = 0;
      if (force_major_slice){
        Setup_for_gc;
        minor_collection ();
        Restore_after_gc;
      }
      /* If a signal arrives between the following two instructions,
         it will be lost. */
      { int signal_number = pending_signal;
        pending_signal = 0;
        if (signal_number) {
          /* Push a return frame to the current code location */
          sp -= 4;
          sp[0] = Val_int(signal_number);
          sp[1] = (value) pc;
          sp[2] = env;
          sp[3] = Val_long(extra_args);
          /* Branch to the signal handler */
          env = Field(signal_handlers, signal_number);
          pc = Code_val(env);
          extra_args = 0;
        }
      }
#if macintosh
      if (have_to_interact){
        have_to_interact = 0;
        rotatecursor_action (0);
      }
#endif
      Next;

/* Calling C functions */

    Instruct(C_CALL1):
      Setup_for_c_call;
      accu = cprim[*pc](accu);
      Restore_after_c_call;
      pc++;
      Next;
    Instruct(C_CALL2):
      Setup_for_c_call;
      accu = cprim[*pc](accu, sp[1]);
      Restore_after_c_call;
      sp += 1;
      pc++;
      Next;
    Instruct(C_CALL3):
      Setup_for_c_call;
      accu = cprim[*pc](accu, sp[1], sp[2]);
      Restore_after_c_call;
      sp += 2;
      pc++;
      Next;
    Instruct(C_CALL4):
      Setup_for_c_call;
      accu = cprim[*pc](accu, sp[1], sp[2], sp[3]);
      Restore_after_c_call;
      sp += 3;
      pc++;
      Next;
    Instruct(C_CALL5):
      Setup_for_c_call;
      accu = cprim[*pc](accu, sp[1], sp[2], sp[3], sp[4]);
      Restore_after_c_call;
      sp += 4;
      pc++;
      Next;
    Instruct(C_CALLN): {
      int nargs = *pc++;
      *--sp = accu;
      Setup_for_c_call;
      accu = cprim[*pc](sp + 1, nargs);
      Restore_after_c_call;
      sp += nargs;
      pc++;
      Next;
    }

/* Integer constants */

    Instruct(CONST0):
      accu = Val_int(0); Next;
    Instruct(CONST1):
      accu = Val_int(1); Next;
    Instruct(CONST2):
      accu = Val_int(2); Next;
    Instruct(CONST3):
      accu = Val_int(3); Next;

    Instruct(PUSHCONST0):
      *--sp = accu; accu = Val_int(0); Next;
    Instruct(PUSHCONST1):
      *--sp = accu; accu = Val_int(1); Next;
    Instruct(PUSHCONST2):
      *--sp = accu; accu = Val_int(2); Next;
    Instruct(PUSHCONST3):
      *--sp = accu; accu = Val_int(3); Next;

    Instruct(PUSHCONSTINT):
      *--sp = accu;
      /* Fallthrough */
    Instruct(CONSTINT):
      accu = Val_int(*pc);
      pc++;
      Next;

/* Integer arithmetic */

    Instruct(NEGINT):
      accu = (value)(2 - (long)accu); Next;
    Instruct(ADDINT):
      accu = (value)((long) accu + (long) *sp++ - 1); Next;
    Instruct(SUBINT):
      accu = (value)((long) accu - (long) *sp++ + 1); Next;
    Instruct(MULINT):
      accu = Val_long(Long_val(accu) * Long_val(*sp++)); Next;

    Instruct(DIVINT): {
      long divisor = Long_val(*sp++);
      if (divisor == 0) { Setup_for_c_call; raise_zero_divide(); }
      accu = Val_long(Long_val(accu) / divisor);
      Next;
    }
    Instruct(MODINT): {
      long divisor = Long_val(*sp++);
      if (divisor == 0) { Setup_for_c_call; raise_zero_divide(); }
      accu = Val_long(Long_val(accu) % divisor);
      Next;
    }
    Instruct(ANDINT):
      accu = (value)((long) accu & (long) *sp++); Next;
    Instruct(ORINT):
      accu = (value)((long) accu | (long) *sp++); Next;
    Instruct(XORINT):
      accu = (value)(((long) accu ^ (long) *sp++) | 1); Next;
    Instruct(LSLINT):
      accu = (value)((((long) accu - 1) << Long_val(*sp++)) + 1); Next;
    Instruct(LSRINT):
      accu = (value)((((unsigned long) accu - 1) >> Long_val(*sp++)) | 1);
      Next;
    Instruct(ASRINT):
      accu = (value)((((long) accu - 1) >> Long_val(*sp++)) | 1); Next;

#define Integer_comparison(opname,tst) \
    Instruct(opname): \
      accu = Val_int((long) accu tst (long) *sp++); Next;

    Integer_comparison(EQ, ==)
    Integer_comparison(NEQ, !=)
    Integer_comparison(LTINT, <)
    Integer_comparison(LEINT, <=)
    Integer_comparison(GTINT, >)
    Integer_comparison(GEINT, >=)

    Instruct(OFFSETINT):
      accu += *pc << 1;
      pc++;
      Next;
    Instruct(OFFSETREF):
      Field(accu, 0) += *pc << 1;
      accu = Val_unit;
      pc++;
      Next;

/* Object-oriented operations */

#define Lookup(obj, lab) \
  Field (Field (Field (obj, 0), ((lab) >> 16) / sizeof (value)), \
         ((lab) / sizeof (value)) & 0xFF)

    Instruct(GETMETHOD):
      accu = Lookup(sp[0], accu);
      Next;

/* Debugging and machine control */

    Instruct(STOP):
      external_raise = initial_external_raise;
      extern_sp = sp;
      return accu;

    Instruct(EVENT):
      if (--event_count == 0) {
        Setup_for_debugger;
        debugger(EVENT_COUNT);
        Restore_after_debugger;
      }
      Restart_curr_instr;

    Instruct(BREAK):
      Setup_for_debugger;
      debugger(BREAKPOINT);
      Restore_after_debugger;
      Restart_curr_instr;

#ifndef THREADED_CODE
    default:
      fatal_error_arg("Fatal error: bad opcode (%lx)\n",
                      (char *)(long)(*(pc-1)));
    }
  }
#endif
}