summaryrefslogtreecommitdiff
path: root/rts/Exception.cmm
blob: 24da1c690e50784451e5f144edce893029cb6f2c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
/* -----------------------------------------------------------------------------
 *
 * (c) The GHC Team, 1998-2004
 *
 * Exception support
 *
 * This file is written in a subset of C--, extended with various
 * features specific to GHC.  It is compiled by GHC directly.  For the
 * syntax of .cmm files, see the parser in ghc/compiler/cmm/CmmParse.y.
 *
 * ---------------------------------------------------------------------------*/

#include "Cmm.h"
#include "RaiseAsync.h"

import ghczmprim_GHCziTypes_True_closure;

/* -----------------------------------------------------------------------------
   Exception Primitives

   A thread can request that asynchronous exceptions not be delivered
   ("blocked") for the duration of an I/O computation.  The primitive
   
	maskAsyncExceptions# :: IO a -> IO a

   is used for this purpose.  During a blocked section, asynchronous
   exceptions may be unblocked again temporarily:

	unmaskAsyncExceptions# :: IO a -> IO a

   Furthermore, asynchronous exceptions are blocked automatically during
   the execution of an exception handler.  Both of these primitives
   leave a continuation on the stack which reverts to the previous
   state (blocked or unblocked) on exit.

   A thread which wants to raise an exception in another thread (using
   killThread#) must block until the target thread is ready to receive
   it.  The action of unblocking exceptions in a thread will release all
   the threads waiting to deliver exceptions to that thread.

   NB. there's a bug in here.  If a thread is inside an
   unsafePerformIO, and inside maskAsyncExceptions# (there is an
   unmaskAsyncExceptions_ret on the stack), and it is blocked in an
   interruptible operation, and it receives an exception, then the
   unsafePerformIO thunk will be updated with a stack object
   containing the unmaskAsyncExceptions_ret frame.  Later, when
   someone else evaluates this thunk, the blocked exception state is
   not restored.

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


INFO_TABLE_RET(stg_unmaskAsyncExceptionszh_ret, RET_SMALL)
{
    CInt r;

    StgTSO_flags(CurrentTSO) = %lobits32(
      TO_W_(StgTSO_flags(CurrentTSO)) & ~(TSO_BLOCKEX|TSO_INTERRUPTIBLE));

    /* Eagerly raise a blocked exception, if there is one */
    if (StgTSO_blocked_exceptions(CurrentTSO) != END_TSO_QUEUE) {

        STK_CHK_GEN( WDS(2), R1_PTR, stg_unmaskAsyncExceptionszh_ret_info);
        /* 
         * We have to be very careful here, as in killThread#, since
         * we are about to raise an async exception in the current
         * thread, which might result in the thread being killed.
         */
        Sp_adj(-2);
        Sp(1) = R1;
        Sp(0) = stg_gc_unpt_r1_info;
        SAVE_THREAD_STATE();
        (r) = foreign "C" maybePerformBlockedException (MyCapability() "ptr", 
    					              CurrentTSO "ptr") [R1];

        if (r != 0::CInt) {
            if (StgTSO_what_next(CurrentTSO) == ThreadKilled::I16) {
                jump stg_threadFinished;
            } else {
                LOAD_THREAD_STATE();
                ASSERT(StgTSO_what_next(CurrentTSO) == ThreadRunGHC::I16);
                jump %ENTRY_CODE(Sp(0));
            }
        }
        else {
            /*
               the thread might have been removed from the
               blocked_exception list by someone else in the meantime.
               Just restore the stack pointer and continue.  
            */   
            Sp_adj(2);
        }
    }

    Sp_adj(1);
    jump %ENTRY_CODE(Sp(0));
}

INFO_TABLE_RET(stg_maskAsyncExceptionszh_ret, RET_SMALL)
{
    StgTSO_flags(CurrentTSO) = 
       %lobits32(
	 TO_W_(StgTSO_flags(CurrentTSO))
          | TSO_BLOCKEX | TSO_INTERRUPTIBLE
      );

    Sp_adj(1);
    jump %ENTRY_CODE(Sp(0));
}

INFO_TABLE_RET(stg_maskUninterruptiblezh_ret, RET_SMALL)
{
    StgTSO_flags(CurrentTSO) = 
       %lobits32(
	(TO_W_(StgTSO_flags(CurrentTSO))
          | TSO_BLOCKEX)
          & ~TSO_INTERRUPTIBLE
       );

    Sp_adj(1);
    jump %ENTRY_CODE(Sp(0));
}

stg_maskAsyncExceptionszh
{
    /* Args: R1 :: IO a */
    STK_CHK_GEN( WDS(1)/* worst case */, R1_PTR, stg_maskAsyncExceptionszh);

    if ((TO_W_(StgTSO_flags(CurrentTSO)) & TSO_BLOCKEX) == 0) {
        /* avoid growing the stack unnecessarily */
        if (Sp(0) == stg_maskAsyncExceptionszh_ret_info) {
            Sp_adj(1);
        } else {
            Sp_adj(-1);
            Sp(0) = stg_unmaskAsyncExceptionszh_ret_info;
        }
    } else {
        if ((TO_W_(StgTSO_flags(CurrentTSO)) & TSO_INTERRUPTIBLE) == 0) {
            Sp_adj(-1);
            Sp(0) = stg_maskUninterruptiblezh_ret_info;
        }
    }

    StgTSO_flags(CurrentTSO) = %lobits32(
        TO_W_(StgTSO_flags(CurrentTSO)) | TSO_BLOCKEX | TSO_INTERRUPTIBLE);

    TICK_UNKNOWN_CALL();
    TICK_SLOW_CALL_v();
    jump stg_ap_v_fast;
}

stg_maskUninterruptiblezh
{
    /* Args: R1 :: IO a */
    STK_CHK_GEN( WDS(1)/* worst case */, R1_PTR, stg_maskAsyncExceptionszh);

    if ((TO_W_(StgTSO_flags(CurrentTSO)) & TSO_BLOCKEX) == 0) {
        /* avoid growing the stack unnecessarily */
        if (Sp(0) == stg_maskUninterruptiblezh_ret_info) {
            Sp_adj(1);
        } else {
            Sp_adj(-1);
            Sp(0) = stg_unmaskAsyncExceptionszh_ret_info;
        }
    } else {
        if ((TO_W_(StgTSO_flags(CurrentTSO)) & TSO_INTERRUPTIBLE) != 0) {
            Sp_adj(-1);
            Sp(0) = stg_maskAsyncExceptionszh_ret_info;
        }
    }

    StgTSO_flags(CurrentTSO) = %lobits32(
        (TO_W_(StgTSO_flags(CurrentTSO)) | TSO_BLOCKEX) & ~TSO_INTERRUPTIBLE);

    TICK_UNKNOWN_CALL();
    TICK_SLOW_CALL_v();
    jump stg_ap_v_fast;
}

stg_unmaskAsyncExceptionszh
{
    CInt r;
    W_ level;

    /* Args: R1 :: IO a */
    STK_CHK_GEN( WDS(4), R1_PTR, stg_unmaskAsyncExceptionszh);
    /* 4 words: one for the unblock frame, 3 for setting up the
     * stack to call maybePerformBlockedException() below.
     */

    /* If exceptions are already unblocked, there's nothing to do */
    if ((TO_W_(StgTSO_flags(CurrentTSO)) & TSO_BLOCKEX) != 0) {

	/* avoid growing the stack unnecessarily */
	if (Sp(0) == stg_unmaskAsyncExceptionszh_ret_info) {
	    Sp_adj(1);
	} else {
	    Sp_adj(-1);
            if ((TO_W_(StgTSO_flags(CurrentTSO)) & TSO_INTERRUPTIBLE) != 0) {
                Sp(0) = stg_maskAsyncExceptionszh_ret_info;
            } else {
                Sp(0) = stg_maskUninterruptiblezh_ret_info;
            }
	}

	StgTSO_flags(CurrentTSO) = %lobits32(
            TO_W_(StgTSO_flags(CurrentTSO)) & ~(TSO_BLOCKEX|TSO_INTERRUPTIBLE));

        /* Eagerly raise a blocked exception, if there is one */
        if (StgTSO_blocked_exceptions(CurrentTSO) != END_TSO_QUEUE) {
            /* 
             * We have to be very careful here, as in killThread#, since
             * we are about to raise an async exception in the current
             * thread, which might result in the thread being killed.
             *
             * Now, if we are to raise an exception in the current
             * thread, there might be an update frame above us on the
             * stack due to unsafePerformIO.  Hence, the stack must
             * make sense, because it is about to be snapshotted into
             * an AP_STACK.
             */
            Sp_adj(-3);
            Sp(2) = stg_ap_v_info;
            Sp(1) = R1;
            Sp(0) = stg_enter_info;

            SAVE_THREAD_STATE();
            (r) = foreign "C" maybePerformBlockedException (MyCapability() "ptr", 
						      CurrentTSO "ptr") [R1];

            if (r != 0::CInt) {
                if (StgTSO_what_next(CurrentTSO) == ThreadKilled::I16) {
                    jump stg_threadFinished;
	        } else {
	            LOAD_THREAD_STATE();
	            ASSERT(StgTSO_what_next(CurrentTSO) == ThreadRunGHC::I16);
	            jump %ENTRY_CODE(Sp(0));
	        }
            } else {
                /* we'll just call R1 directly, below */
                Sp_adj(3);
            }
        }

    }
    TICK_UNKNOWN_CALL();
    TICK_SLOW_CALL_v();
    jump stg_ap_v_fast;
}


stg_getMaskingStatezh
{
    /* args: none */
    /* 
       returns: 0 == unmasked,
                1 == masked, non-interruptible,
                2 == masked, interruptible
    */
    RET_N(((TO_W_(StgTSO_flags(CurrentTSO)) & TSO_BLOCKEX) != 0) +
          ((TO_W_(StgTSO_flags(CurrentTSO)) & TSO_INTERRUPTIBLE) != 0));
}

stg_killThreadzh
{
    /* args: R1 = TSO to kill, R2 = Exception */

    W_ why_blocked;
    W_ target;
    W_ exception;
    
    target = R1;
    exception = R2;
    
    /* Needs 3 words because throwToSingleThreaded uses some stack */
    STK_CHK_GEN( WDS(3), R1_PTR & R2_PTR, stg_killThreadzh);
    /* We call allocate in throwTo(), so better check for GC */
    MAYBE_GC(R1_PTR & R2_PTR, stg_killThreadzh);

    /* 
     * We might have killed ourselves.  In which case, better be *very*
     * careful.  If the exception killed us, then return to the scheduler.
     * If the exception went to a catch frame, we'll just continue from
     * the handler.
     */
    if (target == CurrentTSO) {
        /*
         * So what should happen if a thread calls "throwTo self" inside
         * unsafePerformIO, and later the closure is evaluated by another
         * thread?  Presumably it should behave as if throwTo just returned,
         * and then continue from there.  See #3279, #3288.  This is what
         * happens: on resumption, we will just jump to the next frame on
         * the stack, which is the return point for stg_killThreadzh.
         */
	SAVE_THREAD_STATE();
	/* ToDo: what if the current thread is blocking exceptions? */
	foreign "C" throwToSingleThreaded(MyCapability() "ptr", 
					  target "ptr", exception "ptr")[R1,R2];
	if (StgTSO_what_next(CurrentTSO) == ThreadKilled::I16) {
            jump stg_threadFinished;
	} else {
	    LOAD_THREAD_STATE();
	    ASSERT(StgTSO_what_next(CurrentTSO) == ThreadRunGHC::I16);
	    jump %ENTRY_CODE(Sp(0));
	}
    } else {
	W_ out;
	W_ msg;
	out = Sp - WDS(1); /* ok to re-use stack space here */

	(msg) = foreign "C" throwTo(MyCapability() "ptr",
                                    CurrentTSO "ptr",
                                    target "ptr",
                                    exception "ptr") [R1,R2];
	
        if (msg == NULL) {
	    jump %ENTRY_CODE(Sp(0));
	} else {
            StgTSO_why_blocked(CurrentTSO) = BlockedOnMsgThrowTo;
            StgTSO_block_info(CurrentTSO) = msg;
	    // we must block, and unlock the message before returning
	    jump stg_block_throwto;
	}
    }
}

/* -----------------------------------------------------------------------------
   Catch frames
   -------------------------------------------------------------------------- */

#define SP_OFF 0

/* Catch frames are very similar to update frames, but when entering
 * one we just pop the frame off the stack and perform the correct
 * kind of return to the activation record underneath us on the stack.
 */

INFO_TABLE_RET(stg_catch_frame, CATCH_FRAME,
#if defined(PROFILING)
  W_ unused1, W_ unused2,
#endif
  W_ unused3, P_ unused4)
   {
      Sp = Sp + SIZEOF_StgCatchFrame;
      jump %ENTRY_CODE(Sp(SP_OFF));
   }

/* -----------------------------------------------------------------------------
 * The catch infotable
 *
 * This should be exactly the same as would be generated by this STG code
 *
 * catch = {x,h} \n {} -> catch#{x,h}
 *
 * It is used in deleteThread when reverting blackholes.
 * -------------------------------------------------------------------------- */

INFO_TABLE(stg_catch,2,0,FUN,"catch","catch")
{
  R2 = StgClosure_payload(R1,1); /* h */
  R1 = StgClosure_payload(R1,0); /* x */
  jump stg_catchzh;
}

stg_catchzh
{
    /* args: R1 = m :: IO a, R2 = handler :: Exception -> IO a */
    STK_CHK_GEN(SIZEOF_StgCatchFrame + WDS(1), R1_PTR & R2_PTR, stg_catchzh);
  
    /* Set up the catch frame */
    Sp = Sp - SIZEOF_StgCatchFrame;
    SET_HDR(Sp,stg_catch_frame_info,W_[CCCS]);
    
    StgCatchFrame_handler(Sp) = R2;
    StgCatchFrame_exceptions_blocked(Sp) = 
        TO_W_(StgTSO_flags(CurrentTSO)) & (TSO_BLOCKEX | TSO_INTERRUPTIBLE);
    TICK_CATCHF_PUSHED();

    /* Apply R1 to the realworld token */
    TICK_UNKNOWN_CALL();
    TICK_SLOW_CALL_v();
    jump stg_ap_v_fast;
}

/* -----------------------------------------------------------------------------
 * The raise infotable
 * 
 * This should be exactly the same as would be generated by this STG code
 *
 *   raise = {err} \n {} -> raise#{err}
 *
 * It is used in stg_raisezh to update thunks on the update list
 * -------------------------------------------------------------------------- */

INFO_TABLE(stg_raise,1,0,THUNK_1_0,"raise","raise")
{
  R1 = StgThunk_payload(R1,0);
  jump stg_raisezh;
}

section "data" {
  no_break_on_exception: W_[1];
}

INFO_TABLE_RET(stg_raise_ret, RET_SMALL, P_ arg1)
{
  R1 = Sp(1);
  Sp = Sp + WDS(2);
  W_[no_break_on_exception] = 1;  
  jump stg_raisezh;
}

stg_raisezh
{
    W_ handler;
    W_ frame_type;
    W_ exception;
    /* args : R1 :: Exception */

   exception = R1;

#if defined(PROFILING)
    /* Debugging tool: on raising an  exception, show where we are. */

    /* ToDo: currently this is a hack.  Would be much better if
     * the info was only displayed for an *uncaught* exception.
     */
    if (RtsFlags_ProfFlags_showCCSOnException(RtsFlags) != 0::I32) {
      foreign "C" fprintCCS_stderr(W_[CCCS] "ptr") [];
    }
#endif
    
retry_pop_stack:
    SAVE_THREAD_STATE();
    (frame_type) = foreign "C" raiseExceptionHelper(BaseReg "ptr", CurrentTSO "ptr", exception "ptr") [];
    LOAD_THREAD_STATE();
    if (frame_type == ATOMICALLY_FRAME) {
      /* The exception has reached the edge of a memory transaction.  Check that 
       * the transaction is valid.  If not then perhaps the exception should
       * not have been thrown: re-run the transaction.  "trec" will either be
       * a top-level transaction running the atomic block, or a nested 
       * transaction running an invariant check.  In the latter case we
       * abort and de-allocate the top-level transaction that encloses it
       * as well (we could just abandon its transaction record, but this makes
       * sure it's marked as aborted and available for re-use). */
      W_ trec, outer;
      W_ r;
      trec = StgTSO_trec(CurrentTSO);
      (r) = foreign "C" stmValidateNestOfTransactions(trec "ptr") [];
      outer  = StgTRecHeader_enclosing_trec(trec);
      foreign "C" stmAbortTransaction(MyCapability() "ptr", trec "ptr") [];
      foreign "C" stmFreeAbortedTRec(MyCapability() "ptr", trec "ptr") [];

      if (outer != NO_TREC) {
        foreign "C" stmAbortTransaction(MyCapability() "ptr", outer "ptr") [];
        foreign "C" stmFreeAbortedTRec(MyCapability() "ptr", outer "ptr") [];
      }

      StgTSO_trec(CurrentTSO) = NO_TREC;
      if (r != 0) {
        // Transaction was valid: continue searching for a catch frame
        Sp = Sp + SIZEOF_StgAtomicallyFrame;
        goto retry_pop_stack;
      } else {
        // Transaction was not valid: we retry the exception (otherwise continue
        // with a further call to raiseExceptionHelper)
        ("ptr" trec) = foreign "C" stmStartTransaction(MyCapability() "ptr", NO_TREC "ptr") [];
        StgTSO_trec(CurrentTSO) = trec;
        R1 = StgAtomicallyFrame_code(Sp);
        jump stg_ap_v_fast;
      }          
    }

    // After stripping the stack, see whether we should break here for
    // GHCi (c.f. the -fbreak-on-exception flag).  We do this after
    // stripping the stack for a reason: we'll be inspecting values in
    // GHCi, and it helps if all the thunks under evaluation have
    // already been updated with the exception, rather than being left
    // as blackholes.
    if (W_[no_break_on_exception] != 0) {
        W_[no_break_on_exception] = 0;
    } else {
        if (TO_W_(CInt[rts_stop_on_exception]) != 0) {
            W_ ioAction;
            // we don't want any further exceptions to be caught,
            // until GHCi is ready to handle them.  This prevents
            // deadlock if an exception is raised in InteractiveUI,
            // for exmplae.  Perhaps the stop_on_exception flag should
            // be per-thread.
            CInt[rts_stop_on_exception] = 0;
            ("ptr" ioAction) = foreign "C" deRefStablePtr (W_[rts_breakpoint_io_action] "ptr") [];
            Sp = Sp - WDS(6);
            Sp(5) = exception;
            Sp(4) = stg_raise_ret_info;
            Sp(3) = exception;             // the AP_STACK
            Sp(2) = ghczmprim_GHCziTypes_True_closure; // dummy breakpoint info
            Sp(1) = ghczmprim_GHCziTypes_True_closure; // True <=> a breakpoint
            R1 = ioAction;
            jump RET_LBL(stg_ap_pppv);
        }
    }

    if (frame_type == STOP_FRAME) {
	/*
	 * We've stripped the entire stack, the thread is now dead.
	 * We will leave the stack in a GC'able state, see the stg_stop_thread
	 * entry code in StgStartup.cmm.
	 */
        W_ stack;
        stack = StgTSO_stackobj(CurrentTSO);
        Sp = stack + OFFSET_StgStack_stack
                + WDS(TO_W_(StgStack_stack_size(stack))) - WDS(2);
	Sp(1) = exception;	/* save the exception */
	Sp(0) = stg_enter_info; /* so that GC can traverse this stack */
	StgTSO_what_next(CurrentTSO) = ThreadKilled::I16;
	SAVE_THREAD_STATE();	/* inline! */

        jump stg_threadFinished;
    }

    /* Ok, Sp points to the enclosing CATCH_FRAME or CATCH_STM_FRAME.  Pop everything
     * down to and including this frame, update Su, push R1, and enter the handler.
     */
    if (frame_type == CATCH_FRAME) {
      handler = StgCatchFrame_handler(Sp);
    } else {
      handler = StgCatchSTMFrame_handler(Sp);
    }

    /* Restore the blocked/unblocked state for asynchronous exceptions
     * at the CATCH_FRAME.  
     *
     * If exceptions were unblocked, arrange that they are unblocked
     * again after executing the handler by pushing an
     * unmaskAsyncExceptions_ret stack frame.
     *
     * If we've reached an STM catch frame then roll back the nested
     * transaction we were using.
     */
    W_ frame;
    frame = Sp;
    if (frame_type == CATCH_FRAME) {
      Sp = Sp + SIZEOF_StgCatchFrame;
      if ((StgCatchFrame_exceptions_blocked(frame) & TSO_BLOCKEX) == 0) {
          Sp_adj(-1);
          Sp(0) = stg_unmaskAsyncExceptionszh_ret_info;
      }
    } else {
      W_ trec, outer;
      trec = StgTSO_trec(CurrentTSO);
      outer  = StgTRecHeader_enclosing_trec(trec);
      foreign "C" stmAbortTransaction(MyCapability() "ptr", trec "ptr") [];
      foreign "C" stmFreeAbortedTRec(MyCapability() "ptr", trec "ptr") [];
      StgTSO_trec(CurrentTSO) = outer;
      Sp = Sp + SIZEOF_StgCatchSTMFrame;
    }

    /* Ensure that async excpetions are blocked when running the handler.
     * The interruptible state is inherited from the context of the
     * catch frame.
    */
    StgTSO_flags(CurrentTSO) = %lobits32(
	TO_W_(StgTSO_flags(CurrentTSO)) | TSO_BLOCKEX);
    if ((StgCatchFrame_exceptions_blocked(frame) & TSO_INTERRUPTIBLE) == 0) {
        StgTSO_flags(CurrentTSO) = %lobits32(
            TO_W_(StgTSO_flags(CurrentTSO)) & ~TSO_INTERRUPTIBLE);
    } else {
        StgTSO_flags(CurrentTSO) = %lobits32(
            TO_W_(StgTSO_flags(CurrentTSO)) | TSO_INTERRUPTIBLE);
    }

    /* Call the handler, passing the exception value and a realworld
     * token as arguments.
     */
    Sp_adj(-1);
    Sp(0) = exception;
    R1 = handler;
    Sp_adj(-1);
    TICK_UNKNOWN_CALL();
    TICK_SLOW_CALL_pv();
    jump RET_LBL(stg_ap_pv);
}

stg_raiseIOzh
{
  /* Args :: R1 :: Exception */
  jump stg_raisezh;
}